Patent Publication Number: US-10780427-B2

Title: Selective ammoxidation catalysts

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional application of U.S. application Ser. No. 14/290,380, filed May 29, 2014, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an improved catalyst for use in the ammoxidation of an unsaturated hydrocarbon to the corresponding unsaturated nitrile. In particular, the present invention is directed to an improved catalytic composition for the ammoxidation of propylene and/or isobutylene to acrylonitrile and/or methacrylonitrile, respectively, wherein said catalyst comprises a complex of metal oxides comprising bismuth, molybdenum, iron, cerium and other promoters and wherein said catalyst is characterized by ratio of bismuth to cerium contained in the catalyst. 
     Description of the Prior Art 
     Catalysts containing oxides of iron, bismuth and molybdenum, promoted with suitable elements, have long been used for the conversion of propylene and/or isobutylene at elevated temperatures in the presence of ammonia and oxygen (usually in the form of air) to manufacture acrylonitrile and/or methacrylonitrile. In particular, Great Britain Patent 1436475; U.S. Pat. Nos. 4,766,232; 4,377,534; 4,040,978; 4,168,246; 5,223,469 and 4,863,891 are each directed to bismuth-molybdenum-iron catalysts which may be promoted with the Group II elements to produce acrylonitrile. In addition, U.S. Pat. Nos. 5,093,299, 5,212,137, 5,658,842, 5,834,394, 8,153,546 and CN103418400 are directed to bismuth-molybdenum promoted catalysts exhibiting high yields to acrylonitrile. 
     In part, the instant invention relates to a bismuth-molybdenum-iron catalysts promoted with cerium. It has been discovered that by controlling the relative ratio of bismuth to cerium impacts the performance of the catalyst. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an improved mixed metal oxide catalyst for the ammoxidation of propylene and/or isobutylene. This improved catalyst provides greater overall conversion of the propylene and/or isobutylene to nitriles (i.e. compounds having the function group “—CN”, such as acrylonitrile, methacrylonitrile, acetonitrile and hydrogen cyanide), higher hydrogen cyanide production, and greater ammonia utilization efficiency. 
     In one embodiment, the invention is directed to a catalytic composition comprising a complex of metal oxides wherein the relative ratios of the listed elements in said catalyst are represented by the following formula:
 
Mo m Bi a Fe b A c D d E e F f G g Ce h Ni i Co j Mn k Mg l O # 
     wherein A is at least one element selected from the group consisting of sodium, potassium, rubidium and cesium; and
       D is at least one element selected from the group consisting of zinc, calcium, strontium, cadmium and barium;   E is at least one element selected from the group consisting of chromium, tungsten, boron, aluminum, gallium, indium, phosphorus, arsenic, antimony, vanadium and tellurium;   F is at least one element selected from the group consisting of lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium thulium, ytterbium, lutetium, scandium, yttrium, titanium, zirconium, hafnium, niobium, tantalum, aluminum, gallium, indium, thallium, silicon, germanium and lead;   G is at least one element selected from the group consisting of silver, gold, ruthenium, rhodium, palladium, osmium, iridium, platinum and mercury; and wherein   a is from 0.05 to 7,   b is from 0.1 to 7,   c is from 0.01 to 5,   d is 0 or d is from 0.1 to 12,   e is from 0 to 5,   f is from 0 to 5,   g is from 0 to 0.2,   h is from 0.01 to 5,   i is from 0.1 to 12,   j is 0 or j is from 0.1 to 12,   k is 0 or k is from 0.1 to 12,   l is 0 or 1 is from 0.1 to 12,   m is from 10 to 15,   # is the number of oxygen atoms required to satisfy the valence requirements of the other component elements present; and   wherein z=d+i+j+k+l; and wherein 0.45≤a/h&lt;1.5 and 0.3≤(a+h)/z;
 
wherein 0.57&lt;i/(i+j+k+l). As an embodiment, wherein 0.2&lt;i/(i+j+k+l). As an embodiment, wherein 0.25&lt;i/(i+j+k+l).
   
       

     The present invention is also directed to processes for the conversion of an olefin selected from the group consisting of propylene and isobutylene or mixtures thereof, to acrylonitrile, and/or methacrylonitrile, and other by-product nitriles (i.e. compounds having the function group “—CN”, such acetonitrile and hydrogen cyanide) and mixtures thereof, by reacting in the vapor phase at an elevated temperature and pressure said olefin with a molecular oxygen containing gas and ammonia in the presence of the mixed metal oxide catalyst described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING(S) 
         FIG. 1  provides an aspect of the present invention with a plot trend with respect to acrylonitrile catalyst development showing percentage acrylonitrile yield on the x-axis and i/(i+j+k+l) on the y-axis. 
         FIG. 2  provides an aspect of the present invention with a plot trend with respect to acrylonitrile catalyst development showing trending of percentage acrylonitrile yield on the x-axis and unit cell volume of β-M 2+ MoO 4  by X-Ray Diffraction (Angstroms 3 ) on the y-axis. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is directed to an improved mixed metal oxide catalyst for the ammoxidation of propylene and/or isobutylene. This improved catalyst provides greater overall conversion of the propylene and/or isobutylene to nitriles (i.e. compounds having the function group “—CN”, such as acrylonitrile, methacrylonitrile, acetonitrile and hydrogen cyanide), higher hydrogen cyanide production, and greater ammonia utilization efficiency. 
     The Catalyst: 
     The present invention is directed to a multi-component mixed metal oxide ammoxidation catalytic composition comprising a complex of catalytic oxides wherein the elements and the relative ratios of the elements in said catalytic composition are represented by the following formula: 
     A catalytic composition comprising a complex of metal oxides wherein the relative ratios of the listed elements in said catalyst are represented by the following formula:
 
Mo m Bi a Fe b A c D d E e F f G g Ce h Ni i Co j Mn k Mg l O # 
     wherein A is at least one element selected from the group consisting of sodium, potassium, rubidium and cesium; and
       D is at least one element selected from the group consisting of zinc, calcium, strontium, cadmium and barium;   E is at least one element selected from the group consisting of chromium, tungsten, boron, aluminum, gallium, indium, phosphorus, arsenic, antimony, vanadium and tellurium;   F is at least one element selected from the group consisting of lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium thulium, ytterbium, lutetium, scandium, yttrium, titanium, zirconium, hafnium, niobium, tantalum, aluminum, gallium, indium, thallium, silicon, germanium and lead;   G is at least one element selected from the group consisting of silver, gold, ruthenium, rhodium, palladium, osmium, iridium, platinum and mercury; and wherein   a is from 0.05 to 7,   b is from 0.1 to 7,   c is from 0.01 to 5,   d is 0 or d is from 0.1 to 12,   e is from 0 to 5,   f is from 0 to 5,   g is from 0 to 0.2,   h is from 0.01 to 5,   i is from 0.1 to 12,   j is 0 or j is from 0.1 to 12,   k is 0 or k is from 0.1 to 12,   l is 0 or 1 is from 0.1 to 12,   m is from 10 to 15,   # is the number of oxygen atoms required to satisfy the valence requirements of the other component elements present; and   wherein z=d+i+j+k+l; and wherein 0.45≤a/h&lt;1.5 and 0.3≤(a+h)/z;
 
wherein 0.57&lt;i/(i+j+k+l). As an embodiment, wherein 0.2≤i/(i+j+k+l). As an embodiment, wherein 0.25≤i/(i+j+k+l).
 
In an independent embodiment, a catalytic composition comprising a complex of metal oxides wherein the relative ratios of the listed elements in said catalyst are represented by the following formula:
 
Mo m Bi a Fe b A c D d E e F f G g Ce h Ni i Co j Mn k Mg l O # 
   
       wherein A is at least one element selected from the group consisting of sodium, potassium, rubidium and cesium; and
       D is at least one element selected from the group consisting of nickel, cobalt, manganese, zinc, calcium, strontium, cadmium and barium;   E is at least one element selected from the group consisting of chromium, tungsten, boron, aluminum, gallium, indium, phosphorus, arsenic, antimony, vanadium and tellurium;   F is at least one element selected from the group consisting of lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium thulium, ytterbium, lutetium, scandium, yttrium, titanium, zirconium, hafnium, niobium, tantalum, aluminum, gallium, indium, thallium, silicon, germanium and lead;   G is at least one element selected from the group consisting of silver, gold, ruthenium, rhodium, palladium, osmium, iridium, platinum and mercury; and wherein   a is from 0.05 to 7,   b is from 0.1 to 7,   c is from 0.01 to 5,   d is 0 or d is from 0.1 to 12,   e is from 0 to 5,   f is from 0 to 5,   g is from 0 to 0.2,   h is from 0.01 to 5,   i is from 0.1 to 12,   j is 0 or j is from 0.1 to 12,   k is 0 or k is from 0.1 to 12,   l is 0 or 1 is from 0.1 to 12,   m is from 10 to 15,   # is the number of oxygen atoms required to satisfy the valence requirements of the other component elements present; and   wherein 0.45≤a/h&lt;1.5 and 0.3≤(a+h)/z≤0.4; wherein z=d+i+j+k+l;
 
wherein 0.57&lt;i/(i+j+k+l). As an embodiment, wherein 0.2&lt;i/(i+j+k+l). As an embodiment, wherein 0.25&lt;i/(i+j+k+l).
 
In an independent embodiment, a catalytic composition comprising a complex of metal oxides wherein the relative ratios of the listed elements in said catalyst are represented by the following formula:
 
Mo m Bi a Fe b A c D d E e F f G g Ce h Ni i Co j Mn k Mg l O # 
   
       wherein A is at least one element selected from the group consisting of sodium, potassium, rubidium and cesium; and
       D is at least one element selected from the group consisting of nickel, cobalt, manganese, zinc, calcium, strontium, cadmium and barium;   E is at least one element selected from the group consisting of chromium, tungsten, boron, aluminum, gallium, indium, phosphorus, arsenic, antimony, vanadium and tellurium;   F is at least one element selected from the group consisting of lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium thulium, ytterbium, lutetium, scandium, yttrium, titanium, zirconium, hafnium, niobium, tantalum, aluminum, gallium, indium, thallium, silicon, germanium and lead;   G is at least one element selected from the group consisting of silver, gold, ruthenium, rhodium, palladium, osmium, iridium, platinum and mercury; and wherein   a is from 0.05 to 7,   b is from 0.1 to 7,   c is from 0.01 to 5,   d is 0 or d is from 0.1 to 12,   e is from 0 to 5,   f is from 0 to 5,   g is from 0 to 0.2,   h is from 0.01 to 5,   i is from 0.1 to 12,   j is 0 or j is from 0.1 to 12,   k is 0 or k is from 0.1 to 12,   l is 0 or 1 is from 0.1 to 12,   m is from 10 to 15,   # is the number of oxygen atoms required to satisfy the valence requirements of the other component elements present;
 
wherein 0.7≤a/h&lt;1.5 and 0.3≤(a+h)/z; wherein z=d+i+j+k+l;
 
wherein 0.57&lt;i/(i+j+k+l). As an embodiment, wherein 0.2&lt;i/(i+j+k+l). As an embodiment, wherein 0.25&lt;i/(i+j+k+l).
 
In an independent embodiment, a catalytic composition comprising a complex of metal oxides wherein the relative ratios of the listed elements in said catalyst are represented by the following formula:
 
Mo m Bi a Fe b A c D d E e F f G g Ce h Ni i Co j Mn k Mg l O # 
   
       wherein A is at least one element selected from the group consisting of sodium, potassium, rubidium and cesium; and
       D is at least one element selected from the group consisting of nickel, cobalt, manganese, zinc, calcium, strontium, cadmium and barium;   E is at least one element selected from the group consisting of chromium, tungsten, boron, aluminum, gallium, indium, phosphorus, arsenic, antimony, vanadium and tellurium;   F is at least one element selected from the group consisting of lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium thulium, ytterbium, lutetium, scandium, yttrium, titanium, zirconium, hafnium, niobium, tantalum, aluminum, gallium, indium, thallium, silicon, germanium and lead;   G is at least one element selected from the group consisting of silver, gold, ruthenium, rhodium, palladium, osmium, iridium, platinum and mercury; and wherein   a is from 0.05 to 7,   b is from 0.1 to 7,   c is from 0.01 to 5,   d is 0 or d is from 0.1 to 12,   e is from 0 to 5,   f is from 0 to 5,   g is from 0 to 0.2,   h is from 0.01 to 5,   i is from 0.1 to 12,   j is 0 or j is from 0.1 to 12,   k is 0 or k is from 0.1 to 12,   l is 0 or 1 is from 0.1 to 12,   m is from 10 to 15,   # is the number of oxygen atoms required to satisfy the valence requirements of the other component elements present;
 
wherein 0.45≤a/h&lt;1.5 and 0.3≤(a+h)/z; wherein z=d+i+j+k+l;
 
wherein 0.57&lt;i/(i+j+k+l). As an embodiment, wherein 0≤a/h&lt;1.5 and 0.3≤(a+h)/d. As an embodiment, wherein 0≤a/h&lt;1.5 and 0.3≤(a+h)/z; wherein z=d+i+j+k+l. As an embodiment, wherein 0.2&lt;i/(i+j+k+l). As an embodiment, wherein 0.25&lt;i/(i+j+k+l).
 
In an independent embodiment, a catalytic composition comprising a complex of metal oxides wherein the relative ratios of the listed elements in said catalyst are represented by the following formula:
 
Mo m Bi a Fe b A c D d E e F f G g Ce h Ni i Co j Mn k Mg l O # 
   
       wherein A is at least one element selected from the group consisting of sodium, potassium, rubidium and cesium; and
       D is at least one element selected from the group consisting of zinc, calcium, strontium, cadmium and barium;   E is at least one element selected from the group consisting of chromium, tungsten, boron, aluminum, gallium, indium, phosphorus, arsenic, antimony, vanadium and tellurium;   F is at least one element selected from the group consisting of lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium thulium, ytterbium, lutetium, scandium, yttrium, titanium, zirconium, hafnium, niobium, tantalum, aluminum, gallium, indium, thallium, silicon, germanium and lead;   G is at least one element selected from the group consisting of silver, gold, ruthenium, rhodium, palladium, osmium, iridium, platinum and mercury; and wherein   a is from 0.05 to 7,   b is from 0.1 to 7,   c is from 0.01 to 5,   d is 0 or d is from 0.1 to 12,   e is from 0 to 5,   f is from 0 to 5,   g is from 0 to 0.2,   h is from 0.01 to 5,   i is from 0.1 to 12,   j is 0 or j is from 0.1 to 12,   k is 0 or k is from 0.1 to 12,   l is 0 or 1 is from 0.1 to 12,   m is from 10 to 15,   # is the number of oxygen atoms required to satisfy the valence requirements of the other component elements present; and
 
wherein the cell volume of the M 2+ MoO 4  is defined as β; wherein 625 {acute over (Å)} 3 ≤β≤630 {acute over (Å)} 3 ; In an embodiment, wherein z=d+i+j+k+l and 0.3≤(a+h)/z≤1; In an embodiment, wherein 600 {acute over (Å)} 3 ≤β≤630 {acute over (Å)} 3 .
 
In an independent embodiment, a catalytic composition comprising a complex of metal oxides wherein the relative ratios of the listed elements in said catalyst are represented by the following formula:
 
Mo m Bi a Fe b A c D d E e F f G g Ce h Ni i Co j Mn k Mg l O # 
   
       wherein A is at least one element selected from the group consisting of sodium, potassium, rubidium and cesium; and
       D is at least one element selected from the group consisting of nickel, cobalt, manganese, zinc, calcium, strontium, cadmium and barium;   E is at least one element selected from the group consisting of chromium, tungsten, boron, aluminum, gallium, indium, phosphorus, arsenic, antimony, vanadium and tellurium;   F is at least one element selected from the group consisting of lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium thulium, ytterbium, lutetium, scandium, yttrium, titanium, zirconium, hafnium, niobium, tantalum, aluminum, gallium, indium, thallium, silicon, germanium and lead;   G is at least one element selected from the group consisting of silver, gold, ruthenium, rhodium, palladium, osmium, iridium, platinum and mercury; and wherein   a is from 0.05 to 7,   b is from 0.1 to 7,   c is from 0.01 to 5,   d is 0 or d is from 0.1 to 12,   e is from 0 to 5,   f is from 0 to 5,   g is from 0 to 0.2,   h is from 0.01 to 5,   i is from 0.1 to 12,   j is 0 or j is from 0.1 to 12,   k is 0 or k is from 0.1 to 12,   l is 0 or 1 is from 0.1 to 12,   m is from 10 to 15,   # is the number of oxygen atoms required to satisfy the valence requirements of the other component elements present;
 
wherein 0.45≤a/h&lt;1.5 and 0.3≤(a+h)/z≤0.4; wherein z=d+i+j+k+l; and wherein the cell volume of the M 2+ MoO 4  is defined as β; wherein 625 {acute over (Å)} 3 ≤β≤630 {acute over (Å)} 3 .
 
In an independent embodiment, a catalytic composition comprising a complex of metal oxides wherein the relative ratios of the listed elements in said catalyst are represented by the following formula:
 
Mo m Bi a Fe b A c D d E e F f G g Ce h Ni i Co j Mn k Mg l O # 
   
       wherein A is at least one element selected from the group consisting of sodium, potassium, rubidium and cesium; and
       D is at least one element selected from the group consisting of nickel, cobalt, manganese, zinc, calcium, strontium, cadmium and barium;   E is at least one element selected from the group consisting of chromium, tungsten, boron, aluminum, gallium, indium, phosphorus, arsenic, antimony, vanadium and tellurium;   F is at least one element selected from the group consisting of lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium thulium, ytterbium, lutetium, scandium, yttrium, titanium, zirconium, hafnium, niobium, tantalum, aluminum, gallium, indium, thallium, silicon, germanium and lead;   G is at least one element selected from the group consisting of silver, gold, ruthenium, rhodium, palladium, osmium, iridium, platinum and mercury; and wherein   a is from 0.05 to 7,   b is from 0.1 to 7,   c is from 0.01 to 5,   d is 0 or d is from 0.1 to 12,   e is from 0 to 5,   f is from 0 to 5,   g is from 0 to 0.2,   h is from 0.01 to 5,   i is from 0.1 to 12,   j is 0 or j is from 0.1 to 12,   k is 0 or k is from 0.1 to 12,   l is 0 or 1 is from 0.1 to 12,   m is from 10 to 15,   # is the number of oxygen atoms required to satisfy the valence requirements of the other component elements present;
 
wherein 0.7≤a/h&lt;1.5 and 0.3≤(a+h)/z; wherein z=d+i+j+k+l; and
 
wherein the cell volume of the M 2+ MoO 4  is defined as β; wherein 625 {acute over (Å)} 3 ≤β≤630 {acute over (Å)} 3 . In an embodiment, wherein 600 {acute over (Å)} 3 ≤β≤630 {acute over (Å)} 3 .
 
In an independent embodiment, a catalytic composition comprising a complex of metal oxides wherein the relative ratios of the listed elements in said catalyst are represented by the following formula:
 
Mo m Bi a Fe b A c D d E e F f G g Ce h Ni i Co j Mn k Mg l O # 
   
       wherein A is at least one element selected from the group consisting of sodium, potassium, rubidium and cesium; and
       D is at least one element selected from the group consisting of nickel, cobalt, manganese, zinc, calcium, strontium, cadmium and barium;   E is at least one element selected from the group consisting of chromium, tungsten, boron, aluminum, gallium, indium, phosphorus, arsenic, antimony, vanadium and tellurium;   F is at least one element selected from the group consisting of lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium thulium, ytterbium, lutetium, scandium, yttrium, titanium, zirconium, hafnium, niobium, tantalum, aluminum, gallium, indium, thallium, silicon, germanium and lead;   G is at least one element selected from the group consisting of silver, gold, ruthenium, rhodium, palladium, osmium, iridium, platinum and mercury; and wherein   a is from 0.05 to 7,   b is from 0.1 to 7,   c is from 0.01 to 5,   d is 0 or d is from 0.1 to 12,   e is from 0 to 5,   f is from 0 to 5,   g is from 0 to 0.2,   h is from 0.01 to 5,   i is from 0.1 to 12,   j is 0 or j is from 0.1 to 12,   k is 0 or k is from 0.1 to 12,   l is 0 or 1 is from 0.1 to 12,   m is from 10 to 15,   # is the number of oxygen atoms required to satisfy the valence requirements of the other component elements present;
 
wherein 0.45≤a/h&lt;1.5 and 0.3≤(a+h)/z; wherein z=d+i+j+k+l; and
 
wherein the cell volume of the M 2+ MoO 4  is defined as β; wherein 625 {acute over (Å)} 3 ≤β≤630 {acute over (Å)} 3 ; In an embodiment, wherein 0≤a/h&lt;1.5 and 0.3≤(a+h)/z; In an embodiment, wherein 600 {acute over (Å)} 3 ≤β≤630 {acute over (Å)} 3 .
   
       

     In independent embodiments, wherein 0.2&lt;i/(i+j+k+l); wherein 0.25&lt;i/(i+j+k+l); wherein 0.3&lt;i/(i+j+k+l); 
     wherein 0.5&lt;i/(i+j+k+l); wherein 0.57&lt;i/(i+j+k+l); wherein 0.7&lt;i/(i+j+k+l); wherein z=d+i+j+k+l and 0.3≤(a+h)/z≤1; wherein 0.45≤a/h&lt;1.5; wherein 0.65≤a/h&lt;1.5; wherein 0.7≤a/h&lt;1.5; wherein 0.8≤a/h&lt;1.5; wherein 0.90≤a/h≤1.2; wherein 0.8≤h/b≤5; wherein 1.2≤h/b≤5.
 
As an independent embodiment wherein 0.45≤a/h&lt;1.5, and 0.3≤(a+h)/d.
 
     In independent embodiments, 0.45≤a/h, 0.65≤a/h, 0.7≤a/h, 0.8≤a/h, or, 0.90≤a/h. In other independent embodiments, a/h≤1.2. In one embodiment, 0.8≤h/b≤5. In other independent embodiments: 0.3≤(a+h)/d≤1; 0.3≤(a+h)/d≤0.8; 0.3≤(a+h)/d≤0.6; or 0.3≤(a+h)/d≤0.4. In other embodiments (each line below being an embodiment),
         0.45≤a/h&lt;1.5 and 0.3≤(a+h)/d,   0.65≤a/h&lt;1.5 and 0.3≤(a+h)/d,   0.70≤a/h&lt;1.5 and 0.3≤(a+h)/d,   0.80≤a/h&lt;1.5 and 0.3≤(a+h)/d,   0.90≤a/h&lt;1.5 and 0.3≤(a+h)/d,   0.45≤a/h&lt;1.5, 0.3≤(a+h)/d and 0.8≤h/b≤5,   0.65≤a/h&lt;1.5, 0.3≤(a+h)/d and 0.8≤h/b≤5,   0.70≤a/h&lt;1.5, 0.3≤(a+h)/d and 0.8≤h/b≤5,   0.80≤a/h&lt;1.5, 0.3≤(a+h)/d and 0.8≤h/b≤5,   0.90≤a/h&lt;1.5, 0.3≤(a+h)/d and 0.8≤h/b≤5,   0.90≤a/h≤1.2 and 0.3≤(a+h)/d, and   0.45≤a/h≤1.2, 0.3≤(a+h)/d and 0.8≤h/b≤5.   0.65≤a/h≤1.2, 0.3≤(a+h)/d and 0.8≤h/b≤5.   0.70≤a/h≤1.2, 0.3≤(a+h)/d and 0.8≤h/b≤5.   0.80≤a/h≤1.2, 0.3≤(a+h)/d and 0.8≤h/b≤5.   0.90≤a/h≤1.2, 0.3≤(a+h)/d and 0.8≤h/b≤5,   0.45≤a/h&lt;1.5 and 0.3≤(a+h)/d≤1,   0.65≤a/h&lt;1.5 and 0.3≤(a+h)/d≤1,   0.70≤a/h&lt;1.5 and 0.3≤(a+h)/d≤1,   0.80≤a/h&lt;1.5 and 0.3≤(a+h)/d≤1,   0.90≤a/h&lt;1.5 and 0.3≤(a+h)/d≤1,   0.45≤a/h&lt;1.5, 0.3≤(a+h)/d≤1 and 0.8≤h/b≤5,   0.65≤a/h&lt;1.5, 0.3≤(a+h)/d≤1 and 0.8≤h/b≤5,   0.70≤a/h&lt;1.5, 0.3≤(a+h)/d≤1 and 0.8≤h/b≤5,   0.80≤a/h&lt;1.5, 0.3≤(a+h)/d≤1 and 0.8≤h/b≤5,   0.90≤a/h&lt;1.5, 0.3≤(a+h)/d≤1 and 0.8≤h/b≤5,   0.90≤a/h≤1.2 and 0.3≤(a+h)/d≤1, and   0.45≤a/h≤1.2, 0.3≤(a+h)/d≤1 and 0.8≤h/b≤5.   0.65≤a/h≤1.2, 0.3≤(a+h)/d≤1 and 0.8≤h/b≤5.   0.70≤a/h≤1.2, 0.3≤(a+h)/d≤1 and 0.8≤h/b≤5.   0.80≤a/h≤1.2, 0.3≤(a+h)/d≤1 and 0.8≤h/b≤5.   0.90≤a/h≤1.2, 0.3≤(a+h)/d≤1 and 0.8≤h/b≤5.       

     In one embodiment the catalyst contains no tellurium, antimony or selenium. In another embodiment, the components or elements designated by “E” in the above formula may also include tellurium and/or antimony. In one embodiment, h is from 0.01 to 5. In one embodiment, “F” may additionally include lead (Pb). In one embodiment, “F” may additionally include less than about 10 ppm lead (Pb). In another embodiment, “F” does not include lead (Pb). In one embodiment, “m” is 12. 
     In the embodiments where 0.8≤h/b≤5, “h/b” represents the ratio of cerium to iron in the catalyst and for any catalyst formulation this ratio is simply the moles of cerium (as represented by the subscript for cerium in the formula) divided by the moles of iron (as represented by the subscript for iron in the formula). It has been discovered that catalysts described by the above formula wherein 0.8≤h/b≤5 tend to be stronger in that they have a lower attrition loss as determined by a submerged jet attrition test. 
     As used herein, “catalytic composition” and “catalyst” are synonymous and used interchangeably. As used herein, a “rare earth element” means at least one of lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, scandium and yttrium (while cerium is a rare earth element, it is excluded from this list because cerium is a separately listed component of the catalyst described herein). 
     The catalyst of the present invention may be used either supported or unsupported (i.e. the catalyst may comprise a support). Suitable supports are silica, alumina, zirconium, titania, or mixtures thereof. A support typically serves as a binder for the catalyst and results in a stronger (i.e. more attrition resistant) catalyst. However, for commercial applications, an appropriate blend of both the active phase (i.e. the complex of catalytic oxides described above) and the support is crucial to obtain an acceptable activity and hardness (attrition resistance) for the catalyst. Typically, the support comprises between 40 and 60 weight percent of the supported catalyst. In one embodiment of this invention, the support may comprise as little as about 30 weight percent of the supported catalyst. In another embodiment of this invention, the support may comprise as much as about 70 weight percent of the supported catalyst. 
     In one embodiment the catalyst is supported using a silica sol. Typically, silica sols contain some sodium. In one embodiment, the silica sol contains less than 600 ppm sodium. In another embodiment, the silica sol contains less than 200 ppm sodium. Typically, the average colloidal particle diameter of the silica sol is between about 15 nm and about 50 nm. In one embodiment of this invention, the average colloidal particle diameter of the silica sol is about 10 nm and can be as low as about 4 nm. In another embodiment of this invention, the average colloidal particle diameter of the silica sol is about 100 nm. In another embodiment of this invention, the average colloidal particle diameter of the silica sol is about 20 nm. In another embodiment of this invention, the average colloidal particle diameter of the silica sol is about 40 nm. 
     Catalyst Preparation: 
     The catalyst may be prepared by any of the numerous methods of catalyst preparation which are known to those of skill in the art. A typical preparation method will begin with the formation of a mixture of water, a molybdenum source compound and a support material (e.g. silica sol). Separately, source compounds of the remaining elements in the catalyst are combined in water to form a second mixture. These two mixtures are then combined with stirring at a slightly elevated temperature (approximately 40° C.) to form a catalyst precursor slurry. The catalyst precursor slurry is then dried and denitrified and then calcined as described below. 
     In one embodiment, the elements in the above identified catalyst composition are combined together in an aqueous catalyst precursor slurry, the aqueous precursor slurry so obtained is dried to form a catalyst precursor, and the catalyst precursor is calcined to form the catalyst. However, unique to the process of the instant invention is the following: 
     (i) combining, in an aqueous solution, source compounds of Bi and Ce, and optionally one or more of Na, K, Rb, Cs, Ca, lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, yttrium, Pb, and W, to form a mixture (i.e. a first mixture), 
     (ii) adding a source compound of molybdenum to the mixture (i.e. the first mixture) to react with the mixture and form a precipitate slurry, and 
     (iii) combining the precipitate slurry with source compounds of the remaining elements and of the remaining molybdenum in the catalyst to form the aqueous catalyst precursor slurry. 
     As used herein, “source compounds” are compounds which contain and/or provide one or more of the metals for the mixed metal oxide catalyst composition. As used herein, “remaining elements” or “remaining elements in the catalyst” refers to those elements and the quantity of those elements represented by “A”, “D”, “E”, “F” and “G” in the above formula which were not included in the first mixture. In one embodiment, some elements may be a part of both the first and second mixture. Further, as used herein, “remaining molybdenum” or “remaining molybdenum in the catalyst” refers to that quantity of molybdenum required in the finished catalyst which was not present (i.e. not included in the preparation of) in the precipitate slurry. Lastly, the sum of the quantities of molybdenum provided in the source compounds of molybdenum added in (ii) and (iii) is equal to the total quantity of molybdenum present in the catalyst. 
     In the above catalyst preparation, the source compounds of the remaining elements and of the remaining molybdenum which are combined with the precipitate slurry may be combined in any order or combination of such remaining elements and remaining molybdenum. In one embodiment, a mixture of the source compounds of the remaining elements and of the remaining molybdenum is combined with the precipitate slurry to form the aqueous catalyst precursor slurry. In another embodiment, (i) a mixture of the source compounds of the remaining elements is combined with the precipitate slurry, and (ii) source compounds of the remaining molybdenum are separately added to the precipitate slurry to form the aqueous catalyst precursor slurry. In another embodiment, source compounds of the remaining elements and of the remaining molybdenum are added individually (i.e. one at a time) to the precipitate slurry. In another embodiment, multiple (i.e. more than one) mixtures of source compounds of the remaining elements and of the remaining molybdenum, wherein each mixture contains one or more of the source compounds of the remaining elements or of the remaining molybdenum, are separately added (i.e. one mixture at a time or multiple mixtures added simultaneously) to the precipitate slurry to form the aqueous catalyst precursor slurry. In yet another embodiment, a mixture of source compounds of the remaining elements is combined with a source compound of molybdenum and the resulting mixture is then added to the precipitate slurry to form the catalyst precursor slurry. In yet another embodiment, the support is silica (SiO 2 ) and the silica is combined with a source compound for the remaining molybdenum prior to combining the remaining molybdenum with the precipitate slurry (i.e. the silica and a source compound for the remaining molybdenum are combined to form a mixture and then this mixture is added to the precipitate slurry, individually or in combination with one or more source compounds of the remaining elements). 
     In the above catalyst preparation, molybdenum is added both in the preparation of the precipitate slurry and in the preparation of the aqueous catalyst precursor slurry. On an atomic level, the minimum amount of molybdenum added to form the precipitate slurry is determined by the following relationship
 
Mo=1.5(Bi+Ce)+0.5(Rb+Na+K+Cs)+(Ca)+1.5(sum of the number of atoms of lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium and yttrium)+(Pb)−(W)
 
Wherein in the above relationship “Mo” is the number of atoms of molybdenum to be added to the first mixture, and “Bi”, “Ce”, “Rb”, “Na”, “K”, “Cs”, “Ca”, “Pb” and “W” are the number of atoms of bismuth, cerium, rubidium, sodium, potassium, cesium, calcium, lead and tungsten respectively, present in the first mixture.
 
     In the above catalyst preparation, typically, the amount of molybdenum added to the first mixture to form the precipitate slurry is about 20 to 35% of the total molybdenum in the final catalyst. In one embodiment, a source compound for the remaining molybdenum present in the catalyst is added to the mixture of the source compounds of the remaining elements (i.e. the second mixture) prior to the combination of the mixture of the remaining elements with the precipitate slurry to form the catalyst precursor slurry. In other embodiments, a source compound of molybdenum containing the remaining molybdenum present in the catalyst is added to the precipitate slurry either prior to, after or simultaneously with, the mixture of the source compounds of the remaining elements (i.e. the second mixture) in order to form the catalyst precursor slurry. 
     In the above preparation, source compounds of Bi and Ce, and optionally one or more of Na, K, Rb, Cs, Ca, a rare earth element, Pb and W, are combined in an aqueous solution to form a mixture. In one embodiment, bismuth nitrate and optionally other metal nitrates (i.e. nitrates of Na, K, Rb, Cs, Ca, a rare earth element and/or Pb) are dissolved in an aqueous solution of ceric ammonium nitrate. If tungsten is added, the source compound is typically ammonium paratungstate, (NH 4 ) 10 H 2 (W 2 O 7 ) 6 . 
     Added to the mixture comprising the bismuth and cerium (and optionally one or more of Na, K, Rb, Cs, Ca, a rare earth element, Pb and/or W) is a source compound of molybdenum. In one embodiment this source compound of molybdenum is ammonium heptamolybdate dissolved in water. Upon the addition of the molybdenum source compound to the mixture comprising the bismuth and cerium, a reaction will occur which will result in a precipitate and the resulting mixture is the precipitate slurry. 
     The precipitate slurry is then combined with a mixture of source compound of the remaining elements of the catalyst and a source compound of molybdenum, to form the aqueous catalyst precursor slurry. The mixture of source compounds of the remaining elements and a source compound of molybdenum may be prepared by combining source compounds of the remaining elements in an aqueous solution (e.g. source compounds are combined in water) and then adding a source compound of molybdenum. In one embodiment this source compound of molybdenum is ammonium heptamolybdate dissolved in water. When combining the precipitate slurry with the remaining elements/molybdenum mixture, the order of addition is not important, i.e. the precipitate slurry may be added to the remaining elements/molybdenum mixture or the remaining elements/molybdenum mixture may be added to the precipitate slurry. The aqueous catalyst precursor slurry is maintained at an elevated temperature. 
     The amount of aqueous solvent in each of the above described aqueous mixtures and slurries may vary due to the solubilities of the source compounds combined to form the particular mixed metal oxide. The amount of aqueous solvent should at least be sufficient to yield a slurry or mixture of solids and liquids which is able to be stirred. 
     In any case, the source compounds are preferably combined and/or reacted by a protocol that comprises mixing the source compounds during the combination and/or reaction step. The particular mixing mechanism is not critical, and can include for example, mixing (e.g., stirring or agitating) the components during the reaction by any effective method. Such methods include, for example, agitating the contents of the vessel, for example by shaking, tumbling or oscillating the component-containing vessel. Such methods also include, for example, stirring by using a stirring member located at least partially within the reaction vessel and a driving force coupled to the stirring member or to the reaction vessel to provide relative motion between the stirring member and the reaction vessel. The stirring member can be a shaft-driven and/or shaft-supported stirring member. The driving force can be directly coupled to the stirring member or can be indirectly coupled to the stirring member (e.g., via magnetic coupling). The mixing is generally preferably sufficient to mix the components to allow for efficient reaction between components of the reaction medium to form a more homogeneous reaction medium (e.g., and resulting in a more homogeneous mixed metal oxide precursor) as compared to an unmixed reaction. This results in more efficient consumption of starting materials and in a more uniform mixed metal oxide product. Mixing the precipitate slurry during the reaction step also causes the precipitate to form in solution rather than on the sides of the reaction vessel. More advantageously, having the precipitate form in solution allows for particle growth on all faces of the particle rather than the limited exposed faces when the growth occurs out from the reaction vessel wall. 
     A source compound of molybdenum may include molybdenum (VI) oxide (MoO 3 ), ammonium heptamolybdate or molybdic acid. The source compound of molybdenum may be introduced from any molybdenum oxide such as dioxide, trioxide, pentoxide or heptaoxide. However, it is preferred that a hydrolyzable or decomposable molybdenum salt be utilized as source compound of molybdenum. 
     Typical source compounds for bismuth, cerium and the remaining elements of the catalyst are nitrate salts of the metals. Such nitrate salts are readily available and easily soluble. A source compound of bismuth may include an oxide or a salt which upon calcination will yield the oxide. The water soluble salts which are easily dispersed but form stable oxides upon heat treating are preferred. In one embodiment the source compound of bismuth is bismuth nitrate, Bi(NO 3 ) 3 .5H 2 O 
     A source compound of cerium may include an oxide or a salt which upon calcination will yield the oxide. The water soluble salts which are easily dispersed but form stable oxides upon heat treating are preferred. In one embodiment the source compound of cerium is ceric ammonium nitrate, (NH 4 ) 2 Ce(NO 3 ) 6 . 
     A source compound of iron may be obtained from any compound of iron which, upon calcination will result in the oxide. As with the other elements, water soluble salts are preferred for the ease with which they may be uniformly dispersed within the catalyst. Most preferred is ferric nitrate. 
     Source compounds for the remaining elements may be derived from any suitable source. For example, cobalt, nickel and magnesium may be introduced into the catalyst using nitrate salts. Additionally, magnesium may be introduced into the catalyst as an insoluble carbonate or hydroxide which upon heat treating results in an oxide. Phosphorus may be introduced in the catalyst as an alkaline metal salt or alkaline earth metal salt or the ammonium salt but is preferably introduced as phosphoric acid. 
     Source compounds for the alkali components of the catalyst may be introduced into the catalyst as an oxide or as a salt which upon calcination will yield the oxide. 
     Solvents, in addition to water, may be used to prepare the mixed metal oxides according to the invention include, but are not limited to, alcohols such as methanol, ethanol, propanol, diols (e.g. ethylene glycol, propylene glycol, etc.), organic acids such as acetic acid, as well as other polar solvents known in the art. The metal source compounds are at least partially soluble in the solvent. 
     As previously noted, the catalyst of the present invention may be used either supported or unsupported (i.e. the catalyst may comprise a support). Suitable supports are silica, alumina, zirconia, titania, or mixtures thereof. The support may be added anytime prior to the catalyst precursor slurry being dried. The support may be added at any time during or after the preparation of any mixture of elements, the precipitate slurry or the catalyst precursor slurry. Further the support need not be added in a single point or step (i.e. the support may be added at multiple points in the preparation. In one embodiment, the support is combined with the other ingredients during the preparation of the aqueous catalyst precursor slurry. In one embodiment, the support is added to the precipitate slurry (i.e. after the precipitate slurry is prepared). In one embodiment, the support is combined with the source compound of molybdenum prior to combining the source compound of molybdenum with source compounds of the remaining elements in the catalyst to form the “second mixture” referred to above. 
     The catalyst precursor slurry is dried and denitrified (i.e. the removal of nitrates) to yield the catalyst precursor. In one embodiment, the catalyst precursor slurry is dried to form catalyst particles. In one embodiment, the catalyst precursor slurry is spray-dried into microspheroidal catalyst particles. In one embodiment the spray dryer outlet temperature of between 110° C. and 350° C. dryer outlet temperature, preferably between 110° C. and 250° C., most preferably between 110° C. and 180° C. In one embodiment the spray dryer is a co-current flow spray dryer (i.e. the particles are sprayed co-current to the gas flow). In another embodiment the spray dryer is countercurrent flow (i.e. the particles are sprayed countercurrent to the gas flow). In another embodiment the spray dryer is a pressure nozzle type spray dryer. In such spray-drying processes, water-containing solid phase particles are sprayed into contact with hot gas (usually air) so as to vaporize the water. The drying is controlled by the temperature of the gas and the distance the particles travel in contact with the gas. It is generally undesirable to adjust these parameters to achieve too rapid drying as this results in a tendency to form dried skins on the partially dried particles of the solid phase which are subsequently ruptured as water occluded within the particles vaporizes and attempts to escape. By the same token, it is desirable to provide the catalyst in a form having as little occluded water as possible. Therefore, where a fluidized bed reactor is to be used and microspheroidal particles are desired, it is advisable to choose the conditions of spray-drying with a view to achieving complete drying without particle rupture. The dried catalyst material is then heated to remove any remaining nitrates. The denitrification temperature may range from 100° C. to 500° C., preferably 250° C. to 450° C. 
     Finally, the dried and denitrified catalyst precursor is calcined to form the finished catalyst. In one embodiment, the calcination is effected in air. In another embodiment, the calcination is effected in an inert atmosphere. In one embodiment, the catalyst precursor is calcined in nitrogen. Calcination conditions include temperatures ranging from about 300° C. to about 700° C., more preferably from about 350° C. to about 650° C., and in some embodiments, the calcination may be at about 600° C. In one embodiment, calcination may be completed in multiple stages of increasing temperatures. In one embodiment, a first calcination step is conducted at a temperature in the range of about 300° C. to about 450° C., followed by a second calcination step conducted at a temperature in the range of about 500° C. to about 650° C. 
     Ammoxidation Process 
     The catalysts of the instant invention are useful in ammoxidation processes for the conversion of an olefin selected from the group consisting of propylene, isobutylene or mixtures thereof, to acrylonitrile, methacrylonitrile and mixtures thereof, respectively, by reacting in the vapor phase at an elevated temperature and pressure said olefin with a molecular oxygen containing gas and ammonia in the presence of the catalyst. The catalysts of the instant invention are also useful for the ammoxidation of methanol to hydrogen cyanide and the ammoxidation of ethanol to acetonitrile. In one embodiment employing the catalysts described herein, methanol and/or ethanol can be co-fed to a process for the ammoxidation of propylene, isobutylene or mixtures thereof to acrylonitrile, methacrylonitrile or mixtures thereof, in order to increase the production of hydrogen cyanide and/or acetonitrile co-products resulting from such process. 
     Preferably, the ammoxidation reaction is performed in a fluid bed reactor although other types of reactors such as transport line reactors are envisioned. Fluid bed reactors, for the manufacture of acrylonitrile are well known in the prior art. For example, the reactor design set forth in U.S. Pat. No. 3,230,246, herein incorporated by reference, is suitable. 
     Conditions for the ammoxidation reaction to occur are also well known in the prior art as evidenced by U.S. Pat. Nos. 5,093,299; 4,863,891; 4,767,878 and 4,503,001; herein incorporated by reference. Typically, the ammoxidation process is performed by contacting propylene or isobutylene in the presence of ammonia and oxygen with a fluid bed catalyst at an elevated temperature to produce the acrylonitrile or methacrylonitrile. Any source of oxygen may be employed. For economic reasons, however, it is preferred to use air. The typical molar ratio of the oxygen to olefin in the feed should range from 0.5:1 to 4:1, preferably from 1:1 to 3:1. 
     The molar ratio of ammonia to olefin in the feed in the reaction may vary from between 0.5:1 to 2:1. There is really no upper limit for the ammonia-olefin ratio, but there is generally no reason to exceed a ratio of 2:1 for economic reasons. Suitable feed ratios for use with the catalyst of the instant invention for the production of acrylonitrile from propylene are an ammonia to propylene ratio in the range of 0.9:1 to 1.3:1, and air to propylene ratio of 8.0:1 to 12.0:1. The catalyst of the instant invention is able to provide high yields of acrylonitrile at relatively low ammonia to propylene feed ratios of about 1:1 to about 1.05:1. These “low ammonia conditions” help to reduce unreacted ammonia in the reactor effluent, a condition known as “ammonia breakthrough”, which subsequently helps to reduce process wastes. Specifically, unreacted ammonia must be removed from the reactor effluent prior to the recovery of the acrylonitrile. Unreacted ammonia is typically removed by contacting the reactor effluent with sulfuric acid to yield ammonium sulfate or by contacting the reactor effluent with acrylic acid to yield ammonium acrylate, which in both cases results in a process waste stream to be treated and/or disposed. 
     The reaction is carried out at a temperature of between the ranges of about 260° to 600° C., preferred ranges being 310° to 500° C., especially preferred being 350° to 480° C. The contact time, although not critical, is generally in the range of 0.1 to 50 seconds, with preference being to a contact time of 1 to 15 seconds. 
     The products of reaction may be recovered and purified by any of the methods known to those skilled in the art. One such method involves scrubbing the effluent gases from the reactor with cold water or an appropriate solvent to remove the products of the reaction and then purifying the reaction product by distillation. 
     The primary utility of the catalyst prepared by the process of the instant invention is for the ammoxidation of propylene to acrylonitrile. Other utilities include the ammoxidation of propane to acrylonitrile, and the ammoxidation of glycerol to acrylonitrile. The catalyst prepared by the process of the instant invention may also be used for the oxidation of propylene to acrolein and/or acrylic acid. Such processes are typically two stage processes, wherein propylene is converted in the presence of a catalyst to primarily acrolein in the first stage and the acrolein is converted in the presence of a catalyst to primarily acrylic acid in the second stage. The catalyst described herein is suitable for use in the first stage for the oxidation of propylene to acrolein. 
     SPECIFIC EMBODIMENTS 
     In order to illustrate the instant invention, catalyst prepared in accordance with the instant invention were evaluated and compared under similar reaction conditions to similar catalysts prepared by prior art methods outside the scope of the instant invention. These examples are provided for illustrative purposes only. Catalyst compositions, for each example, are as shown after the example number. All catalyst preparations were made with 39+/−2 nm silica sol. Examples designated with a “C” are comparative examples. 
     Modified Rietveld Analysis 
     Catalytic compositions may be analyzed using X-ray diffraction (XRD) and a modified Rietveld analysis. In this aspect, crystallographic phases of a catalytic composition are analyzed using XRD analysis as known in the art. A diffraction pattern of the catalytic composition is then analyzed with the modified Rietveld analysis described herein. 
     In accordance with the modified Rietveld analysis, a complete diffraction pattern is simulated through an ab initio calculation on the basis of the atomic structures of the individual phases from an assumed phase composition of the measuring sample. The correspondence between the simulated and measured diffraction pattern can then be effected through determination of covariance. 
     Rietveld analysis may be conducted using GSAS software as described in Larson et al., “General Structural Analysis System (GSAS)”, Los Alamos National Laboratory Report LAUR 86-784 (2004) and in Toby, “EXPGUI, A Graphical User Interface for GSAS”, J. Appl. Cryst., 34, 210-221 (2001), both of which are incorporated herein by reference. GSAS and EXPGUI are available at https://subversion.xor.aps.anl.gov/trac/EXPGUI/wiki. 
     The modified Rietveld model includes four phases which can be described as follows. 
                             TABLE 1               Phase   Model Parameters   Refinement                  β-MMoO 4     Based on β-FeMoO 4     Unit cell and           Start from literature structure:   Fe occupancies           Sleight et al., Inorg. Chem., 7,           1093-8 (1968); Inorg. Chem., 7,           1672-5 (1968); and PDF           04-017-6378       Fe 2 (MoO 4 ) 3     Start from literature structure:           Chen, Mater. Res. Bull., 14,           1583-90 (1979); and PDF           04-007-2787       m-phase   Based on Ce 2 (MoO 4 ) 3     Refine unit cell and Ce           Start from literature structure:   occupancies           Brixner et al., J. Solid State           Chem., 5, 247-9 (1972); and PDF           04-009-6366       t-phase   Based on NaBi(MoO 4 ) 2     Refine unit cell           Start from literature structure:           Waskowska et al., Solid State           Chem., 178, 2218-24 (2005); and           PDF 04-011-8393                    
Starting atom coordinates are the same as reported in literature references. Starting lattice parameters are given here and differ slightly from the literature values. Thermal displacement parameters U iso  are given in units of {acute over (Å)} 2 .
 
β-FeMoO 4 , structure described in Sleight et al., Inorg. Chem. 7, 1093-8 (1968), and Inorg. Chem, 7, 1672-5 (1968), and PDF 04-017-6378 (Powder Diffraction File 4+, International Centre for Diffraction Data, 2013), which are incorporated herein by reference.
 
space group C2/m, a=10.194 {acute over (Å)}, b=9.229 {acute over (Å)}, c=7.012 {acute over (Å)}, β=107.08°.
 
U iso  0.01 for Fe, 0.005 for Mo, 0.02 for O,
 
Starting Fe occupancies both 1.000.
 
Fe 2 (MoO 4 ) 3 , structure described in Chen, Mater. Res. Bull., 14, 1583-90 (1979), and PDF 04-007-2787, which are incorporated herein by reference.
 
space group P2 1 /a, a=15.820 {acute over (Å)}, b=9.347 {acute over (Å)}, c=18.196 {acute over (Å)}, β=125.60°.
 
U iso  0.01 for Fe and Mo, 0.02 for O.
 
Ce 2 (MoO 4 ) 3 , structure described in Brixner et al., J. Solid State Chem., 5, 247-9 (1972), and PDF 04-009-6366, which are incorporated herein by reference.
 
space group C2/c, a=16.881 {acute over (Å)}, b=11.825 {acute over (Å)}, c=15.953 {acute over (Å)}, β=108.73°.
 
U iso  0.01 for Ce and Mo, 0.02 for O,
 
Starting Ce occupancies all 1.000.
 
NaBi(MoO 4 ) 2 , structure described in Waskowska et al., Solid State Chem., 178, 2218-24 (2005), and PDF 04-011-8393, which are incorporated herein by reference.
 
space group I4 1 /a, a=5.322 {acute over (Å)}, c=11.851 {acute over (Å)}.
 
U iso  0.01 for Mo, 0.02 for Na, Bi, and O.
 
Background is modeled using either a 3-term cosine Fourier series or a 3-term shifted Chebyshev polynomial.
 
     The amorphous component of the catalyst is modeled using seven Debye scattering terms with correction for thermal motion (diffuse scattering function 1 in GSAS). Each term is modeled as an Si—O vector with a thermal displacement parameter (U) of 0.05 {acute over (Å)} 2 . The Si—O distances of the seven terms are fixed at 1.55, 2.01, 2.53, 2.75, 3.49, 4.23, and 4.97 {acute over (Å)}, and their amplitudes are optimized in the Rietveld fit. 
     The phases and parameters are introduced into the model gradually to ensure a stable refinement. At each step, 5-10 cycles of least-squares refinement are conducted to allow the model to settle down before the next components are introduced. A damping factor of 5 (i.e. 50%) on all parameters except the scale factors of the phases is used to reduce overshoots and oscillations. The procedure is as follows: 
     1. The starting model contains just the β-FeMoO 4  phase with its lattice parameters fixed and its profile Y (Lorentzian lattice strain) set to 75. Only the 3-term background function and the scale factor of the β-FeMoO 4  phase are varied. 
     2. The shift parameter (sample displacement) is added. 
     3. The lattice parameters of β-FeMoO 4  are allowed to vary. 
     4. The other three phases are added, all with fixed lattice parameters and profile X (Lorentzian Scherrer broadening) set to 20, and their scale factors are allowed to vary. 
     5. The 7 diffuse scattering terms are added and their amplitudes are allowed to vary. 
     6. Lattice parameters of the two scheelite-like phases are allowed to vary. 
     7. Profile Y of β-FeMoO 4  and profile X of the other three phases are allowed to vary. Profile X of Fe 2 (MoO 4 ) 3  should be capped at 25. 
     8. Fe occupancies of the β-FeMoO4 phase and Ce occupancies of the Ce 2 (MoO 4 ). 3  phase are allowed to vary. 
     9. Least-squares refinement is continued until convergence, i.e. the sum of (shift/esd) 2  over all parameters is less than 0.01. 
     Example C1 
     Ni 4 Mg 3 Fe 0.9 Rb 0.192 Cr 0.05 Bi 0.72 Ce 1.76 Mo 12.861 O 51.704 +50 wt % SiO 2    
     Reaction mixture A was prepared by heating 154.9 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (140.8 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 26.4 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (32.1 g), Ni(NO 3 ) 2 .6H 2 O (102.6 g), Mg(NO 3 ) 2 .6H 2 O (67.8 g), and Cr(NO 3 ) 3 .9H 2 O (1.76 g). 
     Reaction mixture C was prepared by heating 65.35 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (59.4 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 170.2 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (30.8 g) and RbNO 3  (2.50 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Example C2 
     Ni 4 Mg 3 Fe 0.9 Rb 0.192 Cr 0.05 Bi 0.75 Ce 1.73 Mo 12.861 O 51.689 +50 wt % SiO 2    
     Reaction mixture A was prepared by heating 154.8 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (140.7 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 26.5 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (32.0 g), Ni(NO 3 ) 2 .6H 2 O (102.5 g), Mg(NO 3 ) 2 .6H 2 O (67.8 g), and Cr(NO 3 ) 3 .9H 2 O (1.76 g). 
     Reaction mixture C was prepared by heating 65.3 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (59.4 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 167.1 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (32.0 g) and RbNO 3  (2.49 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Example 3 
     Ni 4 Mg 3 Fe 0.9 Rb 0.192 Cr 0.05 Bi 0.83 Ce 1.65 Mo 12.861 O 51.649 +50 wt % SiO 2    
     Reaction mixture A was prepared by heating 154.5 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (140.5 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 26.8 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (32.0 g), Ni(NO 3 ) 2 .6H 2 O (102.3 g), Mg(NO 3 ) 2 .6H 2 O (67.7 g), and Cr(NO 3 ) 3 .9H 2 O (1.76 g). 
     Reaction mixture C was prepared by heating 65.2 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (59.3 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 159.2 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (35.4 g) and RbNO 3  (2.49 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Example 4 
     Ni 4 Mg 3 Fe 0.9 Rb 0.192 Cr 0.05 Bi 0.98 Ce 1.5 Mo 12.861 O 51.574 +50 wt % SiO 2    
     Reaction mixture A was prepared by heating 154.0 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (140.0 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 27.5 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (31.9 g), Ni(NO 3 ) 2 .6H 2 O (102.0 g), Mg(NO 3 ) 2 .6H 2 O (67.45 g), and Cr(NO 3 ) 3 .9H 2 O (1.75 g). 
     Reaction mixture C was prepared by heating 65.0 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (59.1 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 144.2 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (41.7 g) and RbNO 3  (2.48 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Example 5 
     Ni 4 Mg 3 Fe 0.9 Rb 0.192 Cr 0.05 Bi 0.98 Ce 1.50 Mo 12.861 O x +50 wt % SiO 2    
     Reaction mixture A was prepared by heating 153 ml of deionized water to 55° C. and then adding with stirring ammonium heptamolybdate (137.87 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 30 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (31.62 g), Ni(NO 3 ) 2 .6H 2 O (101.17 g), Mg(NO 3 ) 2 .6H 2 O (66.88 g), and Cr(NO 3 ) 3 .9H 2 O (1.740 g). 
     Reaction mixture C was prepared by heating 65 ml of deionized water to 55° C. and then adding with stirring ammonium heptamolybdate (58.6 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 93.45 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (63.27 g) and RbNO 3  (2.461 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Example 6 
     Ni 4 Mg 3 Fe 0.9 Rb 0.192 Cr 0.05 Bi 1.1 Ce 1.38 Mo 12.861 O 51.514 +50 wt % SiO 2    
     Reaction mixture A was prepared by heating 153.6 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (139.7 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 28.0 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (31.8 g), Ni(NO 3 ) 2 .6H 2 O (101.7 g), Mg(NO 3 ) 2 .6H 2 O (67.3 g), and Cr(NO 3 ) 3 .9H 2 O (1.75 g). 
     Reaction mixture C was prepared by heating 64.8 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (58.9 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 132.3 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (46.7 g) and RbNO 3  (2.48 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Example 7 
     Ni 4 Mg 3 Fe 0.9 Rb 0.192 Cr 0.05 Bi 1.24 Ce 1.24 Mo 12.861 O 51.444 +50 wt % SiO 2    
     Reaction mixture A was prepared by heating 1379 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (1253 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 257 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (285.4 g), Ni(NO 3 ) 2 .6H 2 O (912.9 g), Mg(NO 3 ) 2 .6H 2 O (603.7 g), and Cr(NO 3 ) 3 .9H 2 O (15.7 g). 
     Reaction mixture C was prepared by heating 582 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (529 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 1067 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (472 g) and RbNO 3  (22.2 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (5488 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Example 8 
     Ni 4 Mg 3 Fe 0.9 Rb 0.192  Cr 0.05 Bi 1.3 Ce 1.18 Mo 12.861 O 51.414 +50 wt % SiO 2  Reaction mixture A was prepared by heating 153.0 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (139.1 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 28.8 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (31.7 g), Ni(NO 3 ) 2 .6H 2 O (101.3 g), Mg(NO 3 ) 2 .6H 2 O (67.0 g), and Cr(NO 3 ) 3 .9H 2 O (1.74 g). 
     Reaction mixture C was prepared by heating 64.5 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (58.7 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 112.7 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (54.9 g) and RbNO 3  (2.47 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Example 9 
     Ni 4 Mg 3 Fe 0.9 Rb 0.192 Cr 0.05 Bi 1.35 Ce 1.13 Mo 12.861 O 51.389 +50 wt % SiO 2  Reaction mixture A was prepared by heating 152.8 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (138.9 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 29.0 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (31.6 g), Ni(NO 3 ) 2 .6H 2 O (101.2 g), Mg(NO 3 ) 2 .6H 2 O (66.9 g), and Cr(NO 3 ) 3 .9H 2 O (1.74 g). 
     Reaction mixture C was prepared by heating 64.5 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (58.6 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 107.8 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (57.0 g) and RbNO 3  (2.46 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Example 10 
     Ni 4 Mg 3 Fe 0.9 Rb 0.192 Cr 0.05 Bi 1.40 Ce 1.08 Mo 12.861 O 51.364 +50 wt % SiO 2  Reaction mixture A was prepared by heating 155 ml of deionized water to 55° C. and then adding with stirring ammonium heptamolybdate (139.21 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 31 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (31.69 g), Ni(NO 3 ) 2 .6H 2 O (101.40 g), Mg(NO 3 ) 2 .6H 2 O (67.04 g), and Cr(NO 3 ) 3 .9H 2 O (1.744 g). 
     Reaction mixture C was prepared by heating 72 ml of deionized water to 55° C. and then adding with stirring ammonium heptamolybdate (58.73 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 103.22 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (59.19 g) and RbNO 3  (2.467 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Example 11 
     Ni 4 Mg 3 Fe 0.9 Rb 0.192 Cr 0.05 Bi 1.45 Ce 1.03 Mo 12.861 O 51.339 +50 wt % SiO 2  Reaction mixture A was prepared by heating 152.5 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (138.6 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 29.4 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (31.6 g), Ni(NO 3 ) 2 .6H 2 O (101.0 g), Mg(NO 3 ) 2 .6H 2 O (66.8 g), and Cr(NO 3 ) 3 .9H 2 O (1.74 g). 
     Reaction mixture C was prepared by heating 64.3 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (58.5 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 98.0 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (61.1 g) and RbNO 3  (2.46 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Example C12 
     Ni 4 Mg 3 Fe 0.9 Rb 0.192 Cr 0.05 Bi 2.12 Ce 0.36 Mo 12.861 O 50.37 +50 wt % SiO 2    
     Reaction mixture A was prepared by heating 153 ml of deionized water to 55° C. and then adding with stirring ammonium heptamolybdate (137.87 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 30 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (31.62 g), Ni(NO 3 ) 2 .6H 2 O (101.17 g), Mg(NO 3 ) 2 .6H 2 O (66.88 g), and Cr(NO 3 ) 3 .9H 2 O (1.740 g). 
     Reaction mixture C was prepared by heating 65 ml of deionized water to 55° C. and then adding with stirring ammonium heptamolybdate (58.6 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 93.45 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (63.27 g) and RbNO 3  (2.461 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Example C13 
     Ni 4 Mg 3 Fe 0.9 Rb 0.192 Cr 0.05 Bi 1.760 Ce 0.72 Mo 12.861 O x +50 wt % SiO 2    
     Reaction mixture A was prepared by heating 152 ml of deionized water to 55° C. and then adding with stirring ammonium heptamolybdate (138.0 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 31 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (31.43 g), Ni(NO 3 ) 2 .6H 2 O (100.53 g), Mg(NO 3 ) 2 .6H 2 O (66.48 g), and Cr(NO 3 ) 3 .9H 2 O (1.730 g). 
     Reaction mixture C was prepared by heating 64.5 ml of deionized water to 55° C. and then adding with stirring ammonium heptamolybdate (58.23 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 68.23 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (73.79 g) and RbNO 3  (2.448 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Example C14 
     Ni 4 Mg 3 Fe 0.9 Rb 0.192 Cr 0.05 Bi 2.12 Ce 0.36 Mo 12.861 O 50.37 +50 wt % SiO 2    
     Reaction mixture A was prepared by heating 151 ml of deionized water to 55° C. and then adding with stirring ammonium heptamolybdate (136.85 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 32.5 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (31.15 g), Ni(NO 3 ) 2 .6H 2 O (99.67 g), Mg(NO 3 ) 2 .6H 2 O (65.91 g), and Cr(NO 3 ) 3 .9H 2 O (1.714 g). 
     Reaction mixture C was prepared by heating 70 ml of deionized water to 55° C. and then adding with stirring ammonium heptamolybdate (57.74 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 33.82 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution plus 10 ml deionized water to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (88.13 g) and RbNO 3  (2.427 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of a solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Example C15 
     Ni 4 Mg 3 Fe 0.9 Rb 0.192 Cr 0.05 Bi 2.48 Ce 0.00 Mo 12.861 O x +50 wt % SiO 2    
     Reaction mixture A was prepared by heating 150 ml of deionized water to 55° C. and then adding with stirring ammonium heptamolybdate (135.7 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 33.5 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (30.89 g), Ni(NO 3 ) 2 .6H 2 O (98.83 g), Mg(NO 3 ) 2 .6H 2 O (65.36 g), and Cr(NO 3 ) 3 .9H 2 O (1.699 g). 
     Reaction mixture C was prepared by heating 63 ml of deionized water to 55° C. and then adding with stirring ammonium heptamolybdate (57.25 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 100 g of 1:10 nitric acid solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (102.20 g) and RbNO 3  (2.406 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of a white solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Example 12 
     Ni 6 Mg 1.5 Fe 0.5 Rb 0.192  Cr 0.05 Bi 0.72 Ce 1.76 Mo 13.191 O 52.594 +50 wt % SiO 2    
     Reaction mixture A was prepared by heating 140 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (127.5 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 25.8 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (17.2 g), Ni(NO 3 ) 2 .6H 2 O (148.3 g), Mg(NO 3 ) 2 .6H 2 O (32.71 g), and Cr(NO 3 ) 3 .9H 2 O (1.70 g). 
     Reaction mixture C was prepared by heating 77.6 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (70.5 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 164.1 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (29.7 g) and RbNO 3  (2.40 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Example 13 
     Ni 5.5 Fe 0.5 Mn 2 Rb 0.192 Cr 0.05 Bi 0.72 Ce 1.76 Mo 13.191 O 52.594 +50 wt % SiO 2  Reaction mixture A was prepared by heating 138 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (125.7 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 60.0 g of 50 wt % Mn(NO 3 ) 2  solution to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (16.9 g), Ni(NO 3 ) 2 .6H 2 O (134.0 g, and Cr(NO 3 ) 3 .9H 2 O (1.68 g). 
     Reaction mixture C was prepared by heating 76.4 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (69.5 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 161.7 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (29.3 g) and RbNO 3  (2.37 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Example 14 
     Ni 6 Co 1.5 Fe 0.5 Rb 0.192 Cr 0.05 Bi 0.72 Ce 1.76 Mo 13.191 O 52.594 +50 wt % SiO 2  Reaction mixture A was prepared by heating 138 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (125.3 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 25.8 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (16.9 g), Ni(NO 3 ) 2 .6H 2 O (145.8 g), Co(NO 3 ) 2 .6H 2 O (36.48 g), and Cr(NO 3 ) 3 .9H 2 O (1.67 g). 
     Reaction mixture C was prepared by heating 76.2 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (69.3 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 161.3 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (29.2 g) and RbNO 3  (2.37 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Comparative Example 16 
     Co 1.5 Mg 6 Fe 0.5 Rb 0.192 Cr 0.05 Bi 0.72 Ce 1.76 Mo 13.191 O 52.594 +50 wt % SiO 2    
     Reaction mixture A was prepared by heating 148 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (134.6 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 25.7 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (18.1 g), Mg(NO 3 ) 2 .6H 2 O (138.1 g), Co(NO 3 ) 2 .6H 2 O (39.18 g), and Cr(NO 3 ) 3 .9H 2 O (1.80 g). 
     Reaction mixture C was prepared by heating 81.9 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (74.4 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 173.2 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (31.3 g) and RbNO 3  (2.54 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Comparative Example 17 
     Ni 1.5 Mg 6 Fe 0.5 Rb 0.192 Cr 0.05 Bi 0.72 Ce 1.76 Mo 13.191 O 52.594 +50 wt % SiO 2  Reaction mixture A was was prepared by heating 148.1 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (134.6 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 25.7 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (18.1 g), Ni(NO 3 ) 2 .6H 2 O (39.1 g), Mg(NO 3 ) 2 .6H 2 O (138.1 g), and Cr(NO 3 ) 3 .9H 2 O (1.80 g). 
     Reaction mixture C was prepared by heating 81.9 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (74.4 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 173.2 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (31.35 g) and RbNO 3  (2.54 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Comparative Example 18 
     Mg 6 Fe 0.5 Mn 1.5 Rb 0.192 Cr 0.05 Bi 0.72 Ce 1.76 Mo 13.191 O 52.594 +50 wt % SiO 2  Reaction mixture A was was prepared by heating 148.4 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (134.9 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 48.3 g of 50 wt % Mn(NO 3 ) 2  solution to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (18.2 g), Mg(NO 3 ) 2 .6H 2 O (138.4 g, and Cr(NO 3 ) 3  9H 2 O (1.80 g). 
     Reaction mixture C was prepared by heating 82.0 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (74.6 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 173.6 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (31.4 g) and RbNO 3  (2.55 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Example 15 
     Ni 2.03 Co 2.03 Mg 2.03 Fe 1 Mn 0.92 Rb 0.192 C r0.05 Bi 0.72 Ce 1.76 Mo 13.201 O 52.884 +50 wt % SiO 2    
     Reaction mixture A was prepared by heating 141.3 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (128.4 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by adding 11.3 ml of deionized water to 28.2 g of 50 wt % Mn(NO 3 ) 2  solution, heating to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (34.55 g), Ni(NO 3 ) 2 .6H 2 O (50.48 g, Mg(NO 3 ) 2 .6H 2 O (44.51 g), Co(NO 3 ) 2 .6H 2 O (50.53 g), and Cr(NO 3 ) 3  9H 2 O (1.71 g). 
     Reaction mixture C was prepared by heating 78.0 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (70.9 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 165.0 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (29.9 g) and RbNO 3  (2.42 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Example 16 
     Ni 6 Mg 1.5 Fe 0.5 Rb 0.192 Cr 0.05 Bi 1.24 Ce 1.24 Mo 13.191 O 52.334 +50 wt % SiO 2    
     Reaction mixture A was prepared by heating 143.1 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (130.0 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 27.9 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (17.0 g), Ni(NO 3 ) 2 .6H 2 O (146.8 g), Mg(NO 3 ) 2 .6H 2 O (32.36 g), and Cr(NO 3 ) 3 .9H 2 O (1.68 g). 
     Reaction mixture C was prepared by heating 72.5 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (65.9 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 114.4 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (50.6 g) and RbNO 3  (2.38 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Example 17 
     Ni 5.5 Fe 0.5 Mn 2 Rb 0.192 Cr 0.05 Bi 1.24 Ce 1.24 Mo 13.191 O 52.334 +50 wt % SiO 2  Reaction mixture A was prepared by heating 141.0 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (128.15 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 59.3 g of 50 wt % Mn(NO 3 ) 2  solution to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (16.7 g), Ni(NO 3 ) 2 .6H 2 O (132.6 g, and Cr(NO 3 ) 3 .9H 2 O (1.66 g). 
     Reaction mixture C was prepared by heating 71.4 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (64.9 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 112.7 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (49.9 g) and RbNO 3  (2.35 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Example 18 
     Ni 6 Co 1.5 Fe 0.5 Rb 0.192 Cr 0.05 Bi 1.24 Ce 1.24 Mo 13.191 O 52.334 +50 wt % SiO 2  Reaction mixture A was prepared by heating 140.6 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (127.8 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 27.9 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (16.7 g), Ni(NO 3 ) 2 .6H 2 O (144.3 g), Co(NO 3 ) 2 .6H 2 O (36.10 g), and Cr(NO 3 ) 3 .9H 2 O (1.65 g). 
     Reaction mixture C was prepared by heating 71.2 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (64.8 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 112.4 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (49.7 g) and RbNO 3  (2.34 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Comparative Example 19 
     Co 1.5 Mg 6 Fe 0.5 Rb 0.192 Cr 0.05 Bi 1.24 Ce 1.24 Mo 13.191 O 52.334 +50 wt % SiO 2  Reaction mixture A was was prepared by heating 150.9 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (137.2 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 27.9 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (17.9 g), Mg(NO 3 ) 2 .6H 2 O (136.5 g), Co(NO 3 ) 2 .6H 2 O (38.74 g), and Cr(NO 3 ) 3 .9H 2 O (1.78 g). 
     Reaction mixture C was prepared by heating 76.5 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (69.5 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 120.7 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (53.4 g) and RbNO 3  (2.51 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Comparative Example 20 
     Ni 1.5 Mg 6 Fe 0.5 Rb 0.192 Cr 0.05 Bi 1.24 Ce 1.24 Mo 13.191 O 52.334 +50 wt % SiO 2    
     Reaction mixture A was prepared by heating 150.9 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (137.2 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 27.9 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (17.9 g), Ni(NO 3 ) 2 .6H 2 O (38.72 g), Mg(NO 3 ) 2 .6H 2 O (136.55 g), and Cr(NO 3 ) 3 .9H 2 O (1.78 g). 
     Reaction mixture C was prepared by heating 76.5 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (69.5 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 120.7 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (53.4 g) and RbNO 3  (2.51 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Comparative Example 21 
     Mg 6 Fe0. 5 Mn 1.5 Rb 0.192 Cr 0.05 Bi 1.24 Ce 1.24 Mo 13.191 O 52.334 +50 wt % SiO 2    
     Reaction mixture A was prepared by heating 151.2 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (137.5 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by adding 2.4 ml of deionized water to 47.7 g of 50 wt % Mn(NO 3 ) 2  solution, heating to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (17.97 g), Mg(NO 3 ) 2 .6H 2 O (136.8 g), and Cr(NO 3 ) 3 .9H 2 O (1.78 g). 
     Reaction mixture C was prepared by heating 76.6 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (69.65 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 120.9 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (53.5 g) and RbNO 3  (2.52 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Example 19 
     Ni 6 Mg 1.5 Fe 0.5 Rb 0.192 Cr 0.05 Bi 0.72 Ce 1.76 Mo 13.191 O 52.594 +50 wt % SiO 2    
     Reaction mixture A was prepared by heating 140 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (127.5 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 25.8 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (17.2 g), Ni(NO 3 ) 2 .6H 2 O (148.3 g), Mg(NO 3 ) 2 .6H 2 O (32.71 g), and Cr(NO 3 ) 3 .9H 2 O (1.70 g). 
     Reaction mixture C was prepared by heating 77.6 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (70.5 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 164.1 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (29.7 g) and RbNO 3  (2.40 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Example 20 
     Ni 6 Fe 2 Rb 0.192 Cr 0.05 Bi 0.72 Ce 1.76 Mo 13.191 O 52.334 +50 wt % SiO 2  Reaction mixture A was prepared by heating 137.5 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (125.0 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 27.3 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (67.4 g), Ni(NO 3 ) 2 .6H 2 O (145.4 g) and Cr(NO 3 ) 3 .9H 2 O (1.67 g). 
     Reaction mixture C was prepared by heating 76.0 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (69.1 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 160.9 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (29.1 g) and RbNO 3  (2.36 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Example 21 
     Ni 6 Co 1.5 Fe 0.5 Rb 0.192 Cr 0.05 Bi 0.72 Ce 1.76 Mo 13.191 O 52.594 +50 wt % SiO 2  Reaction mixture A was was prepared by heating 138 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (125.3 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 25.8 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (16.9 g), Ni(NO 3 ) 2 .6H 2 O (145.8 g), Co(NO 3 ) 2 .6H 2 O (36.48 g), and Cr(NO 3 ) 3 .9H 2 O (1.67 g). 
     Reaction mixture C was prepared by heating 76.2 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (69.3 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 161.3 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (29.2 g) and RbNO 3  (2.37 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Example 22 
     Ni 6 Mg 1.5  Fe 0.5 Rb 0.192 Cr 0.05 Bi 1.24 Ce 1.24 Mo 13.191 O 52.334 +50 wt % SiO 2    
     Reaction mixture A was prepared by heating 143 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (130.0 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 27.9 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (17.0 g), Ni(NO 3 ) 2 .6H 2 O (146.8 g), Mg(NO 3 ) 2 .6H 2 O (32.35 g), and Cr(NO 3 ) 3 .9H 2 O (1.68 g). 
     Reaction mixture C was prepared by heating 72.5 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (65.9 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 114.4 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (50.6 g) and RbNO 3  (2.38 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Example 23 
     Ni 6 Co 1.5 Fe 0.5 Rb 0.192 Cr 0.05 Bi 1.24 Ce 1.24 Mo 13.191 O 52.334 +50 wt % SiO 2    
     Reaction mixture A was prepared by heating 141 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (127.8 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by heating 27.9 ml of deionized water to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (16.7 g), Ni(NO 3 ) 2 .6H 2 O (144.3 g), Co(NO 3 ) 2 .6H 2 O (36.1 g), and Cr(NO 3 ) 3 .9H 2 O (1.65 g). 
     Reaction mixture C was prepared by heating 71.2 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (64.8 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 112.4 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (49.7 g) and RbNO 3  (2.34 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Comparative Example 22 
     Ni 6 Fe 0.5 Mn 1.5 Rb 0.192 Cr 0.05 Bi 0.72 Ce 1.76 Mo 13.191 O 52.594 +50 wt % SiO 2    
     Reaction mixture A was prepared by heating 138.1 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (125.6 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by adding 1.8 ml of deionized water to 44.95 g of 50 wt % Mn(NO 3 ) 2  solution, heating to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (16.91 g), Ni(NO 3 ) 2 .6H 2 O (146.1 g), and Cr(NO 3 ) 3 .9H 2 O (1.675 g). 
     Reaction mixture C was prepared by heating 76.4 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (69.4 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 161.6 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (29.2 g) and RbNO 3  (2.37 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Comparative Example 23 
     Ni 6 Fe 0.5 Mn 1.5 Rb 0.192 Cr 0.05 Bi 1.24 Ce 1.24 Mo 13.191 O 52.334 +50 wt % SiO 2    
     Reaction mixture A was prepared by heating 140.9 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (128.1 g) to form a clear colorless solution. 
     Reaction mixture B was prepared by adding 4.1 ml of deionized water to 44.5 g of 50 wt % Mn(NO 3 ) 2  solution, heating to 55° C. and then adding with stirring Fe(NO 3 ) 3 .9H 2 O (16.7 g), Ni(NO 3 ) 2 .6H 2 O (144.6 g), and Cr(NO 3 ) 3 .9H 2 O (1.66 g). 
     Reaction mixture C was prepared by heating 71.4 ml of deionized water to 65° C. and then adding with stirring over 30 minutes ammonium heptamolybdate (64.9 g) to form a clear colorless solution. 
     Reaction mixture D was prepared by (i) heating 112.6 g of 50 wt % aqueous (NH 4 ) 2 Ce(NO 3 ) 6  solution to 55° C., (ii) while the solution was stirring and heating, sequentially adding Bi(NO 3 ) 3 .5H 2 O (49.8 g) and RbNO 3  (2.35 g). 
     Reaction mixture E was prepared by adding with stirring, silica sol (610 g, 41 wt % silica) to Reaction mixture A, followed by the addition of Reaction mixture B. 
     Reaction mixture F was prepared by adding reaction mixture C to reaction mixture D, which resulted in precipitation of an orange solid (this resulting mixture was the precipitate slurry). The stirring of the precipitate slurry was continued for 15 minutes while the temperature was maintained in the 50-55° C. range. 
     Reaction mixture E was then added to reaction mixture F to form the final catalyst precursor slurry. 
     The catalyst precursor slurry was allowed to stir for one hour while it cooled to approximately 40° C. It was then homogenized in a blender for 3 minutes at 5000 rpm. The slurry was then spray dried in a spray dryer at an inlet/outlet temperature of 325/140° C. The resulting powder was denitrified by heat treating for 3 hours in air at 290° C., followed by an additional 3 hours at 425° C. The powder was then calcined in air for 3 hours at 560° C. 
     Catalyst Testing 
     All catalyst were tested in a bench scale reactor for the ammoxidation of propylene to acrylonitrile. All testing was conducted in a 40 cc fluid bed reactor. Propylene was feed into the reactor at the rates shown in Table 2, between 0.06 and 0.09 WWH (i.e. weight of propylene/weight of catalyst/hour). Pressure inside the reactor was maintained at 10 psig. Reaction temperature was 430° C. Samples of reaction products were collected after several days of testing (between about 140 to about 190 hours on stream). Reactor effluent was collected in bubble-type scrubbers containing cold HCl solution. Off-gas rate was measured with soap film meter, and the off-gas composition was determined at the end of the run with the aid of gas chromatograph fitted with a split column gas analyzer. At the end of the recovery run, the entire scrubber liquid was diluted to approximately 200 grams with distilled water. A weighted amount of 2-butanone was used as internal standard in a ˜50 gram aliquot of the dilute solution. A 2 μl sample was analyzed in a GC fitted with a flame ionization detector and a Carbowax™ column. The amount of NH 3  was determined by titrating the free HCl excess with NaOH solution. 
     
       
         
           
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 Ex. No. 
                 Catalyst 
                 WWH 
                 % C 3  = Conv 
                 % AN Yield 
                 % AN Sel 
                 a/h 
                 (a + h)/d 
                 h/b 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 C1  
                 Ni4Mg3Fe0.9Rb0.192Cr0.05Bi0.72Ce1.76Mo12.861 
                 0.06 
                 98.5 
                 81.9 
                 83.2 
                 0.41 
                 0.354 
                 1.96 
               
               
                   
                 O 51.704 + 50 wt % 
               
               
                 C2  
                 Ni4Mg3Fe0.9Rb0.192Cr0.05Bi0.75Ce1.73Mo12.861 
                 0.06 
                 97.8 
                 81.3 
                 83.2 
                 0.43 
                 0.35 
                 1.92 
               
               
                   
                 O 51.689 + 50 wt % 
               
               
                 3 
                 Ni4Mg3Fe0.9Rb0.192Cr0.05Bi0.83Ce1.65Mo12.861 
                 0.06 
                 98.5 
                 84.0 
                 85.2 
                 0.50 
                 0.354 
                 1.83 
               
               
                   
                 O 51.649 + 50 wt % 
               
               
                 4 
                 Ni4Mg3Fe0.9Rb0.192Cr0.05Bi0.98Ce1.5Mo12.861 
                 0.06 
                 97.2 
                 82.3 
                 84.6 
                 0.65 
                 0.35 
                 1.67 
               
               
                   
                 O 51.574 + 50 wt % 
               
               
                 5 
                 Ni4Mg3Fe0.9Rb0.192Cr0.05Bi0.98Ce1.50Mo12.861 
                 0.06 
                 97.8 
                 82.6 
                 84.4 
                 0.65 
                 0.354 
                 1.67 
               
               
                   
                 O x  + 50 wt % 
               
               
                 6 
                 Ni4Mg3Fe0.9Rb0.192Cr0.05Bi1.10Ce1.38Mo12.861 
                 0.06 
                 97.1 
                 82.8 
                 85.3 
                 0.80 
                 0.35 
                 1.53 
               
               
                   
                 O 51.414 + 50 wt % 
               
               
                 7 
                 Ni4Mg3Fe0.9Rb0.192Cr0.05Bi1.24Ce1.24Mo12.861 
                 0.06 
                 98.6 
                 85 
                 86.2 
                 1.00 
                 0.354 
                 1.38 
               
               
                   
                 O x  + 50 wt % 
               
               
                 8 
                 Ni4Mg3Fe0.9Rb0.192Cr0.05Bi1.3Ce1.18Mo12.861 
                 0.06 
                 96.3 
                 83.7 
                 88.6 
                 1.10 
                 0.35 
                 1.31 
               
               
                   
                 O 51.414 + 50 wt % 
               
               
                 9 
                 Ni4Mg3Fe0.9Rb0.192Cr0.05Bi1.35Ce1.13Mo12.861 
                 0.06 
                 97.2 
                 82.4 
                 84.8 
                 1.19 
                 0.354 
                 1.26 
               
               
                   
                 O 51.389 + 50 wt % 
               
               
                 10  
                 Ni4Mg3Fe0.9Rb0.192Cr0.05Bi1.40Ce1.08Mo12.861 
                 0.06 
                 96.4 
                 82.7 
                 85.8 
                 1.30 
                 0.35 
                 1.2 
               
               
                   
                 O 51.364 + 50 wt % 
               
               
                 11  
                 Ni4Mg3Fe0.9Rb0.192Cr0.05Bi1.45Ce1.03Mo12.861 
                 0.06 
                 95.9 
                 82.4 
                 85.9 
                 1.41 
                 0.354 
                 1.14 
               
               
                   
                 O 51.339 + 50 wt % 
               
               
                 C12 
                 Ni4Mg3Fe0.9Rb0.192Cr0.05Bi1.50Ce0.98Mo12.861 
                 0.06 
                 92.4 
                 73.2 
                 79.2 
                 1.53 
                 0.35 
                 1.09 
               
               
                   
                 O x  + 50 wt % 
               
               
                 C13 
                 Ni4Mg3Fe0.9Rb0.192Cr0.05Bi1.760Ce0.72Mo12.861 
                 0.06 
                 94.7 
                 81.6 
                 86.2 
                 2.44 
                 0.354 
                 0.80 
               
               
                   
                 O x  + 50 wt % 
               
               
                 C14 
                 Ni4Mg3Fe0.9Rb0.192Cr0.05Bi2.12Ce0.36Mo12.861 
                 0.06 
                 90.2 
                 70.7 
                 78.4 
                 5.89 
                 0.35 
                 0.40 
               
               
                   
                 O50.37 + 50 wt % 
               
               
                 C15 
                 Ni4Mg3Fe0.9Rb0.192Cr0.05Bi2.48Ce0.00Mo12.861 
                 0.06 
                 93.4 
                 75.9 
                 81.2 
                 ∞ 
                 0.354 
                 0.00 
               
               
                   
                 O x  + 50 wt % 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
             
               
                 TABLE 3 
               
               
                   
               
               
                 Ex No. 
                 Rb 
                 Bi 
                 Ce 
                 Fe 
                 Ni 
                 Co 
                 Mn 
                 Mg 
                 Mo 
                 % SiO2 
                 i/(i + j + k + l) 
                 % AN Yield 
                 WWH 
                 h/b 
                 a/h 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Ex. 12 
                 0.192 
                 0.72 
                 1.76 
                 0.50 
                 6.00 
                 0.00 
                 0.00 
                 1.50 
                 13.191 
                 50 
                 0.80 
                 81.0 
                 0.060 
                 3.52 
                 0.41 
               
               
                 Ex. 13 
                 0.192 
                 0.72 
                 1.76 
                 0.50 
                 5.50 
                 0.00 
                 2.00 
                 0.00 
                 13.191 
                 50 
                 0.73 
                 83.7 
                 0.060 
                 3.52 
                 0.41 
               
               
                 Ex 14 
                 0.192 
                 0.72 
                 1.76 
                 0.50 
                 6.00 
                 1.50 
                 0.00 
                 0.00 
                 13.191 
                 50 
                 0.80 
                 81.2 
                 0.060 
                 3.52 
                 0.41 
               
               
                 C16 
                 0.192 
                 0.72 
                 1.76 
                 0.50 
                 0.00 
                 1.50 
                 0.00 
                 6.00 
                 13.191 
                 50 
                 0.00 
                 72.2 
                 0.060 
                 3.52 
                 0.41 
               
               
                 C17 
                 0.192 
                 0.72 
                 1.76 
                 0.50 
                 1.50 
                 0.00 
                 0.00 
                 6.00 
                 13.191 
                 50 
                 0.20 
                 69.3 
                 0.060 
                 3.52 
                 0.41 
               
               
                 C18 
                 0.192 
                 0.72 
                 1.76 
                 0.50 
                 0.00 
                 0.00 
                 1.50 
                 6.00 
                 13.191 
                 50 
                 0.00 
                 61.9 
                 0.060 
                 3.52 
                 0.41 
               
               
                 Ex. 15 
                 0.192 
                 0.72 
                 1.76 
                 1.00 
                 2.03 
                 2.03 
                 0.92 
                 2.03 
                 13.191 
                 50 
                 0.29 
                 79.5 
                 0.060 
                 1.76 
                 0.41 
               
               
                 Ex 16 
                 0.192 
                 1.24 
                 1.24 
                 0.50 
                 6.00 
                 0.00 
                 0.00 
                 1.50 
                 13.191 
                 50 
                 0.80 
                 85.2 
                 0.070 
                 2.48 
                 1.00 
               
               
                 Ex 17 
                 0.192 
                 1.24 
                 1.24 
                 0.50 
                 5.50 
                 0.00 
                 2.00 
                 0.00 
                 13.191 
                 50 
                 0.73 
                 75.3 
                 0.060 
                 2.48 
                 1.00 
               
               
                 Ex 18 
                 0.192 
                 1.24 
                 1.24 
                 0.50 
                 6.00 
                 1.50 
                 0.00 
                 0.00 
                 13.191 
                 50 
                 0.80 
                 82.8 
                 0.060 
                 2.48 
                 1.00 
               
               
                 C19 
                 0.192 
                 1.24 
                 1.24 
                 0.50 
                 0.00 
                 1.50 
                 0.00 
                 6.00 
                 13.191 
                 50 
                 0.00 
                 61.6 
                 0.060 
                 2.48 
                 1.00 
               
               
                 C20 
                 0.192 
                 1.24 
                 1.24 
                 0.50 
                 1.50 
                 0.00 
                 0.00 
                 6.00 
                 13.191 
                 50 
                 0.20 
                 65.6 
                 0.060 
                 2.48 
                 1.00 
               
               
                 C21 
                 0.192 
                 1.24 
                 1.24 
                 0.50 
                 0.00 
                 0.00 
                 1.50 
                 6.00 
                 13.191 
                 50 
                 0.00 
                 60.0 
                 0.060 
                 2.48 
                 1.00 
               
               
                   
               
            
           
         
       
     
                                                                             TABLE 4               Ex No.   Rb   Bi   Ce   Fe   Ni   Co   Mn   Mg   Mo   % SiO2   β Å 3     % AN   h/b   WWH                                                                                            Ex. 19   0.192   0.72   1.76   0.50   6.00   0.00   0.00   1.50   13.191   50   626.5   81.0   3.52   0.060       Ex. 20   0.192   0.72   1.76   2.00   6.00   0.00   0.00   0.00   13.191   50   623.5   79.1   0.88   0.060       Ex. 21   0.192   0.72   1.76   0.50   6.00   1.50   0.00   0.00   13.191   50   627.0   81.2   3.52   0.060       Ex. 22   0.192   1.24   1.24   0.50   6.00   0.00   0.00   1.50   13.191   50   626.9   85.2   2.48   0.070       Ex. 23   0.192   1.24   1.24   0.50   6.00   1.50   0.00   0.00   13.191   50   626.7   82.8   2.48   0.060       C22   0.192   0.72   1.76   0.50   6.00   0.00   1.50   0.00   13.191   50   634.0   78.4   3.52   0.060       C23   0.192   1.24   1.24   0.50   6.00   0.00   1.50   0.00   13.191   50   633.5   74.5   2.48   0.060                    
Notes for Table 2, 3 and 4 (where applicable):
 
1. “WWH” is weight of propylene per weight of catalyst per hour in the feed
 
2. “% C 3   = Conv” is mole percent per pass conversion of propylene to all products.
 
3. “% AN Yield” is percent acrylonitrile yield.
 
4. “% AN Sel” is percent acrylonitrile selectivity.
 
5. “a/h” is an atomic ratio of bismuth to cerium.
 
6. “(a+h)/d” is ratio of (atoms of bismuth plus atoms of cerium) to atoms of D.
 
7. “h/b” is an atomic ratio of cerium to iron.
 
8. “β Å 3 ” is a measurement of cell volume in Angstroms 3 .
 
     The data in Tables 2, 3 and 4 clearly shows the benefit of the present invention. Examples 12-14 and 15-18 within the scope of the claimed invention (i.e. wherein 0.2&lt;i/(i+j+k+l)) exhibit greater acrylonitrile yield than those catalysts of C16-C18 and C19-C21 which are outside the claimed bismuth to cerium ratio range. Examples 19-23 with measurement of cell volume in Angstroms 3  within the scope of the claimed invention, wherein the cell volume of the M 2+ MoO 4  is defined as β; wherein 600 {acute over (Å)} 3 ≤β≤630 {acute over (Å)} 3 , exhibit greater acrylonitrile yield than those catalysts of C22, and C23 which are outside the claimed cell volume (β) range. 
     While the foregoing description and the above embodiments are typical for the practice of the instant invention, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of this description. Accordingly, it is intended that all such alternatives, modifications and variations are embraced by and fall within the spirit and broad scope of the appended claims.