Catalyst for exhaust gas purification

A catalyst for exhaust gas purification having a crystalline silicate including an oxide of an alkali metal and/or hydrogen ion, aluminum oxide, an oxide of an alkaline earth metal, Ca, Mg, Sn, or Ba, an X-ray diffraction pattern described in Table 1 in the specification, and containing at least one metal from the group consisting of the elements in Groups Ib and VIII of the periodic table, rare earth elements, titanium, vanadium, chromium, antimony, zinc, and manganese. With the use of a crystalline silicate containing alkaline earth elements together with other metals or with a composite structure of catalyst, the separation of aluminum or other metals from the crystal lattices (dealuminization or demetallization) can be controlled, and heat and steam resistance may be achieved.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a catalyst for purifying exhaust gases 
that contain nitrogen oxides (NOx), carbon monoxide (CO), and 
hydrocarbons. 
2. Description of the Related Art 
For the purification treatment of exhaust gases from automobiles and other 
similar sources, catalysts (composition: Pt, Rh/Al.sub.2 O.sub.3 system) 
known as three-way catalysts which utilize hydrocarbons and CO in the 
automotive emissions are usually used. The three-way catalysts are 
normally prepared by applying a .gamma.-alumina slurry to a refractory 
carrier of cordierite or the like, baking, and then causing the carrier to 
support a metal, e.g., Pt, Rh, or Pd. They cannot remove NOx, 
hydrocarbons, and CO, however, unless the combustion occurs within a very 
narrow range close to the theoretical air-fuel ratio (e.g., A/F=14.6). 
With growing concern over the global environments in recent years, there 
has been strong demand for fuel-efficient cars. Accordingly, lean-burn 
engines for combustion above the theoretical air-fuel ratio have arrested 
attention as a key technology. It is well-known that the fuel efficiency 
is improved by burning in the engine a fuel mixture of an increased 
air-fuel ratio (A/F). 
However, this is accompanied by an increase in the oxygen concentration in 
the exhaust to such a level that while an ordinary three-way catalyst can 
remove hydrocarbons and CO, it does not remove NOx. 
To purify the exhaust gas in the "lean-burn" region where the oxygen 
concentration is high, it has already been proposed to use catalysts 
consisting of a transition metal, such as Cu, supported by a zeolite of 
the general formula, xM.sub.2 /.sub.n O.Al.sub.2 O.sub.3.ySiO.sub.2, 
wherein M is an n-valent metal (see, e.g., Japanese Patent Provisional 
Publications Nos. 125250/1985 (60-125250) and 130735/1989 (1-130735)). 
Another catalyst has also been introduced to meet the end which comprises 
a crystalline silicate to which Cu is added, the silicate itself having a 
chemical composition, (1.+-.0.4)R.sub.2 O.[aM.sub.2 O.sub.3.bAl.sub.2 
O.sub.3 ].ySiO.sub.2, in which R is an alkali metal ion and/or hydrogen 
ion, M is the ion of at least one element selected from the group 
consisting of Group VIII elements, rare earth elements, titanium, 
vanadium, chromium, niobium, and antimony, a+b=1.0, a.ltoreq.0, b&gt;0, and 
y&gt;12 (Japanese Patent Provisional Publication No. 303194/1989 (1-303194)). 
While these recently introduced catalysts exhibit satisfactory initial 
activities, they have the disadvantage of limited durability. 
Exhaust gases from ordinary lean-burn engines are at high temperatures over 
a broad range of 300.degree. to 700.degree. C., and conventional catalysts 
used for such engines have been found to deteriorate due to sintering of 
the supported active metal. Also, the present inventors have found that 
the catalytic deterioration of such conventional catalysts is accelerated 
by demetallization, a phenomenon in which aluminum and iron in the crystal 
lattices, which form ion exchange sites in the catalyst carrier zeolite 
and crystalline silicate, are removed from the crystal lattices under the 
influence of the high temperature exhaust gas atmosphere, especially in 
the presence of steam. 
SUMMARY OF THE INVENTION 
In view of the state of the art summarized above, an object of this 
invention is to provide a catalyst for purifying exhaust gases which is 
highly resistant to heat and steam and which does not have the drawbacks 
of conventional catalysts. 
In order to develop a catalyst with great resistance to heat and steam, it 
is necessary to avoid the separation of aluminum or iron from the carrier, 
and it has been found that if aluminum remains stably in the crystal 
lattice, the degree of sintering of the active metal would be low under 
the exhaust gas conditions in the presence of high temperature steam. 
The present inventors have also found that a catalyst which uses an 
alkaline earth metal-containing crystalline silicate as a catalyst carrier 
and which supports Cu or other similar metals on the carrier inhibits the 
metal from separating from the crystal lattices at elevated temperatures 
and in the presence of steam; that is, the demetallization can be 
controlled. 
Thus the present inventors have developed a catalyst with excellent heat 
and steam resistance developed through the application of a crystalline 
silicate which incurs only a small possibility of dealuminization. 
Furthermore, the present inventors have also discovered that by employing a 
composite structure of a crystalline silicate catalyst, the 
demetallization in high temperature steam atmosphere can be prevented, and 
have developed new types of catalysts for the purification of exhaust 
gases containing nitrogen oxides, hydrocarbons, and carbon monoxide. 
A first aspect of this invention provides a catalyst for exhaust gas 
purification which comprises a crystalline silicate which in a dehydrated 
state has a chemical formula, in terms of the molar ratio of oxides, 
EQU aR.sub.2 O.bMO.Al.sub.2 O.sub.3.cSiO.sub.2, 
wherein R is an alkali metal ion and/or hydrogen ion, M is an alkaline 
earth metal, Ca, Mg, Sr, or Ba, a =0-2, b=0.03-40, with the proviso that 
a+b&gt;1, and c=11-3000 and which silicate has an X-ray diffraction pattern 
described in Table 1 hereinbelow, said crystalline silicate containing at 
least one metal chosen from Groups Ib and VIII of the periodic table. 
In the above chemical formula it is specified that a is 0 to 2 and a+b is 
more than one. This is because the components in these ranges permit the 
synthesis of the crystalline silicate as formulated. Also, the specified 
range of b being 0.03 to 40 is where the alkaline earth metal can function 
effectively. The further limitation of c being 11 to 3000 is based on the 
fact that if c is less than 11 the synthesis of the crystalline silicate 
is impossible and if c is more than 3000 the resulting catalyst according 
to the invention does not have adequate exhaust purification activity. 
Thus, the catalyst of the first aspect of the invention for exhaust gas 
purification is characterized by the use of a silicate containing an 
alkaline earth metal as a crystalline silicate which incurs only a limited 
possibility of removal of aluminum from the carrier. This silicate is 
produced through crystallization by hydrothermal synthesis, with the 
presence of an alkaline earth metal in the starting material mixture. 
TABLE 1 
______________________________________ 
Lattice spacing (d value) 
Relative intensity 
______________________________________ 
11.2 .+-. 0.3 VS 
10.0 .+-. 0.3 VS 
6.7 .+-. 0.2 W 
6.4 .+-. 0.2 M 
6.0 .+-. 0.2 M 
5.7 .+-. 0.2 W 
5.6 .+-. 0.2 M 
4.6 .+-. 0.1 W 
4.25 .+-. 0.1 M 
3.85 .+-. 0.1 VS 
3.75 .+-. 0.1 S 
3.65 .+-. 0.1 S 
3.3 .+-. 0.1 M 
3.05 .+-. 0.1 W 
3.0 .+-. 0.1 M 
______________________________________ 
VS: Very Strong 
S: Strong 
M: Moderate 
W: Weak 
For the synthesis of the crystalline silicate that contains an alkaline 
earth metal, the silica source to be used is water glass, silica sol, 
silica gel or the like. The alumina source to be chosen is aluminum 
nitrate, aluminum sulfate, sodium aluminate or the like. The alkali metal 
ion is, e.g., sodium oxide in water glass, sodium aluminate, sodium 
hydroxide. For alkaline earth metal ions, their acetates, nitrates, and 
chlorides may be used. As an alkaline earth metal calcium (Ca), magnesium 
(Mg), strontium (St), or barium (Ba) can be used. Further, as a 
crystallizing mineralizer tetrapropylammonium bromide or the like is used. 
The reaction mixture for the hydrothermal synthesis of the alkaline earth 
metal-containing crystalline silicate is made up with the following mixing 
ratios: SiO.sub.2 /Al.sub.2 O.sub.3 =11 to 3000 (molar ratio); OH.sup.- 
/SiO.sub.2 =0.01 to 10; H.sub.2 O/SiO.sub.2 =1 to 1000; 
tetrapropylammonium compound/SiO.sub.2 =0 to 4; alkaline earth metal/Al 
(atomic ratio)=0.03 to 40. 
The crystalline silicate can be synthesized by heating the above mixture at 
80.degree. to 200.degree. C. for about 1 to 200 hours with stirring, 
removing excess ions by water rinsing, drying, and then baking. 
The catalyst according to the first aspect of the invention is prepared by 
allowing the alkaline earth metal-containing crystalline silicate to 
support at least one metal in Groups Ib and VIII, e.g., copper or cobalt, 
either by way of ion exchange with the immersion of the silicate in an 
aqueous solution of such a metal or by impregnating the silicate with an 
aqueous solution of a salt of the metal, such as chloride or nitrate. 
Although the catalyst made in accordance with the invention is desired to 
have a honeycomb shape that permits the reduction of pressure loss, it may 
be pelletized instead. Such binder as silica sol or alumina sol in use for 
the molding of the catalyst has already been confirmed to have little 
adverse effect upon the catalyst performance. 
The catalyst of this first aspect for exhaust gas purification is 
adequately durable in automotive exhaust purification and other similar 
services with only little deterioration of activity in the presence of 
steam at 600.degree. C. and even higher temperatures. 
The outstanding durability of the catalyst according to the first aspect of 
the invention is attributable to the use of an alkaline earth-containing 
silicate as a carrier. The alkaline earth contained in the silicate 
functions to decrease the number of strongly acidic points in the silicate 
which would otherwise accelerate the dealuminization. On the other hand, 
it causes little change in the catalytic activities for NO adsorption and 
the activation of hydrocarbons. Since the dealuminization is thus avoided, 
the Group Ib or VIII metal or metals that are active can be stably 
supported by the silicate carrier. 
A second aspect of this invention provides a catalyst for exhaust gas 
purification, comprising a crystalline silicate which in a dehydrated 
state has a chemical formula, 
EQU (1.+-.0.4)R.sub.2 O.[aM.sub.2 O.sub.3.bAl.sub.2 O.sub.3 ].cMeO.ySiO.sub.2, 
wherein R is an alkali metal ion and/or hydrogen ion, M is at least one 
element selected from the group consisting of Group VIII elements, rare 
earth elements, titanium, vanadium, chromium, niobium, and antimony, Me is 
an alkaline earth element, a+b=1.0, a&gt;0, b&gt;0, y/c&gt;12, and y&gt;12, said 
crystalline silicate containing at least one metal selected from Zn, Mn, 
Cr, and the elements in Groups Ib and VIII of the periodic table. 
The alkaline earth metal-containing crystalline silicate is prepared by 
mixing sources of silica, alkaline earth metal, alkali metal, transition 
metal, and aluminum with water and a quaternary alkylammonium salt such as 
tetrapropylammonium bromide, or an alcohol amine, alkylamine or the like, 
and then holding this reaction mixture for a period and at a temperature 
adequate for forming a crystalline silicate. 
The silica source to be used may be water glass, silica sol, silica gel or 
the like. The alkaline earth metal source may be an acetate, nitrate, 
chloride, or the like of Ca, Mg, St, or Ba. 
The alkali metal is, e.g., sodium in water glass, sodium hydroxide, or 
potassium hydroxide. The aluminum source may be sodium aluminate, aluminum 
nitrate, aluminum sulfate, or the like. Transition metal sources include 
the Group VIII elements, such as Fe, Ni, Co, Rh, Ru, and Pd, rare earth 
elements, such as La and Ce, as well as Ti, V, Cr, Nb, and Sb. Such a 
source of transition metals may be used in the form of, e.g., a sulfate, 
nitrate, or chloride as a starting material. 
The catalyst is prepared by adding the chloride or nitrate of Cu, Co, Ni, 
Zn, Fe, Cr, or Mn to the alkaline earth metal-containing crystalline 
silicate either through impregnation or ion exchange with an aqueous 
solution of their salt. 
The catalyst according to the second aspect of the invention is 
characterized in that it is prepared by allowing an alkaline earth metal 
to be present in the reaction mixture at the time of crystalline silicate 
synthesis. Presumably, the alkaline earth metal incorporated and 
stabilized in the lattice of the silicate crystal in this way helps 
improve the catalyst durability. 
A third aspect of this invention provides a catalyst for exhaust gas 
purification comprising a composite crystalline silicate having an X-ray 
diffraction pattern described in Table 1 above, the composite crystalline 
silicate being formed by growing a crystalline silicate made from Si and O 
over a mother crystal of a crystalline silicate synthesized in advance, 
the mother crystal being represented, in a dehydrated state and in terms 
of the molar ratio of oxides, by the following chemical formula: 
EQU (1.+-.0.6 )R.sub.2 O.[aM.sub.2 O.sub.3.bAl.sub.2 O.sub.3 ].ySiO.sub.2, 
wherein R is an alkali metal ion and/or hydrogen ion, M is an ion of at 
least one element selected from the group consisting of Group VIII 
elements, rare earth elements, titanium, vanadium, chromium, niobium, 
antimony, and gallium, a.ltoreq.0, b.ltoreq.0, a+b=1, and y&gt;12, said 
mother crystal having an X-ray diffraction pattern described in Table 1 
above, the crystalline silicate grown over the mother crystal having the 
same crystalline structure as the mother crystal, and the composite 
crystalline silicate containing at least one metal chosen from Groups Ib 
and VIII of the periodic table. 
The mother crystal to be used in the third aspect of the present invention 
is synthesized under the following conditions: 
SiO.sub.2 /(M.sub.2 O.sub.3 +Al.sub.2 O.sub.3): 12-3000 (preferably 20-200 
) 
OH.sup.- /SiO.sub.2 : 0-1.0 (preferably 0.2-0.8) 
H.sub.2 O/SiO.sub.2 : 2-1000 (preferably 10-200) 
Organonitrogen compound/(M.sub.2 O.sub.3 +Al.sub.2 O.sub.3): 0-200 
(preferably 0-50) 
M signifies one or more elements chosen from Group VIII elements, rare 
earth elements, titanium, vanadium, chromium, niobium, antimony, and 
gallium, and the organonitrogen compound when used may be 
tetrapropylammonium bromide or the like. 
The crystalline silicate used as the mother crystal can be synthesized by 
heating a mixture of the above materials at a temperature and for a time 
period sufficient for producing a crystalline silicate. The temperature 
for hydrothermal synthesis is in the range of 80.degree. to 300.degree. 
C., preferably 130.degree. to 200.degree. C., and the hydrothermal 
synthesis may be carried out for 0.5 to 14 days, preferably 1 to 10 days. 
The pressure is not specifically limited, but desirably the synthesis is 
carried out under the mixture's own pressure. 
The hydrothermal synthesis reaction is effected by heating the material 
mixture to a desired temperature and, with stirring where necessary, 
continued until a crystalline silicate forms. Following the 
crystallization, the reaction mixture is cooled down to room temperature, 
filtered, rinsed with water, and separated. Usually, the product is 
further dried at 100.degree. C. or above for about 5 to 24 hours. 
The term "composite crystalline silicate" as used herein means a composite 
crystalline silicate of a structure formed by first synthesizing a 
crystalline silicate in the aforesaid manner as a mother crystal and then 
allowing a crystalline silicate (to be called "silicalite" hereinafter) 
which comprises Si and O and has the same structure as the mother crystal 
to grow thereon. 
The crystalline silicate serving as the mother crystal is desirably one 
which is represented, in a dehydrated state and in terms of the molar 
ratio of oxides, by the following chemical formula: 
EQU (1.+-.0.6)R.sub.2 O.[aM.sub.2 O.sub.3.bAl.sub.2 O.sub.3 ].ySiO.sub.2, 
wherein R is an alkali metal ion and/or hydrogen ion, M is an ion of at 
least one element selected from the group consisting of Group VIII 
elements, rare earth elements, titanium, vanadium, chromium, niobium, 
antimony, and gallium, a.gtoreq.0, b.gtoreq.0, a+b=1, and y&gt;12, said 
crystalline silicate having an X-ray diffraction pattern shown in Table 1 
above. 
One method for the crystal growth of silicalite on the outer surface of the 
crystalline silicate serving as the mother crystal is hydrothermal 
synthesis. 
For the crystal growth of silicalite on the outer surface of the mother 
crystal by hydrothermal synthesis, water glass, silica sol or the like is 
employed as a silica source. The alkali metal ion to be used is, e.g., 
sodium oxide or sodium hydroxide in water glass, and the crystallizing 
mineralizer is, e.g., tetrapropylammonium bromide. 
The proportion of the silicalite to be grown as crystal with respect to the 
mother crystal crystalline silicate is desirably, in terms of the 
silicalite/mother crystal weight ratio, from 0.01 to 100 for the 
synthesis. Also, as a prerequisite for the crystal growth of silicalite on 
the mother crystal, the mixing ratios of the materials should be: OH.sup.- 
/SiO.sub.2 =0.01 to 10, H.sub.2 O/SiO.sub.2 =1 to 1000, and organic 
matter (e.g., tetrapropylammonium compound)/SiO.sub.2 =0 to 10. 
The synthesis procedure consists of adding finely powdered mother crystals 
to the above mixture, stirring the whole mixture homogeneously, heating it 
with stirring at 80 to 200.degree. C. for 1 to 200 hours, removing excess 
ions by water rinsing, drying, and baking. In this way a composite 
crystalline silicate according to the third aspect of the present 
invention is obtained. 
The catalyst is prepared by immersing the composite crystalline silicate in 
an aqueous solution of a salt of a Group Ib or VIII metal, e.g., copper or 
cobalt, and allowing the silicate to support the metal ion by ion exchange 
or by impregnation with an aqueous solution of a metal salt, such as 
chloride or nitrate. 
In the third aspect of the invention, the use of a silicalite-covered 
composite crystalline silicate improves the durability of the resulting 
catalyst for the following reason. In exhaust emissions present are such 
gases as NO, CO, hydrocarbons, H.sub.2 O (steam), and O.sub.2. The exhaust 
is purified at the active reaction sites of the catalyst while, at the 
same time, the presence of high temperature H.sub.2 O tends to cause 
metals to separate from the silicate (demetallization). However, the 
coating of silicalite, which is hydrophobic by nature, makes it difficult 
for H.sub.2 O alone to permeate deep into the crystalline silicate. As a 
consequence, the H.sub.2 O concentrations become low around the active 
reaction sites in the catalyst, and the demetallization is inhibited. 
A fourth aspect of this invention provides a catalyst for exhaust gas 
purification comprising a composite crystalline silicate having an X-ray 
diffraction pattern shown in Table 1 above, the composite crystalline 
silicate being formed by growing a crystalline silicate made from Si and 0 
over a mother crystal of a crystalline silicate synthesized in advance, 
said mother crystal is represented, in a dehydrated state and in terms of 
the molar ratio of oxides, by the following chemical formula: 
EQU (1.+-.0.6)R.sub.2 O.[aM.sub.2 O.sub.3.bAl.sub.2 O.sub.3 ].cMeO.ySiO.sub.2, 
wherein R is an alkali metal ion and/or hydrogen ion, M is at least one 
element selected from the group consisting of Group VIII elements, rare 
earth elements, titanium, vanadium, chromium, niobium, antimony, and 
gallium, Me is an alkaline earth element, a.gtoreq.0, b.gtoreq.0, 
c.gtoreq.0, a+b=1, y/c&gt;12, and y&gt;12, the mother crystal having an X-ray 
diffraction pattern shown in Table 1 above, the crystalline silicate grown 
over the mother crystal having the same crystalline structure as the 
mother crystal, and the composite crystalline silicate containing at least 
one metal chosen from Groups Ib and VIII of the periodic table. 
The mother crystal to be used in the present invention can be synthesized 
under the following conditions: 
SiO.sub.2 /(M.sub.2 O.sub.3 +Al.sub.2 O.sub.3): 12-3000 (preferably 20-200) 
SiO.sub.2 /MeO: 12-.infin.(preferably 20-10000) 
OH.sup.- /SiO.sub.2 : 0-10 
H.sub.2 O/SiO.sub.2 : 2-1000 (preferably 10-200) 
Organonitrogen compound/(M.sub.2 O.sub.3 +Al.sub.2 O.sub.3): 0-1000 
(preferably 0-50) 
M is at least one element selected from the group consisting of Group VIII 
elements, rare earth elements, titanium, vanadium, chromium, niobium, 
antimony, and gallium, Me is an alkaline earth metal, and the 
organonitrogen compound when used may be tetrapropylammonium bromide or 
the like. 
The crystalline silicate used as the mother crystal is synthesized by 
heating a mixture of the above materials at a temperature and for a time 
period sufficient for producing a crystalline silicate. The temperature 
for hydrothermal synthesis is in the range of 80.degree. to 300.degree. 
C., preferably 130.degree. to 200.degree. C., and the hydrothermal 
synthesis is carried out for 0.5 to 14 days, preferably 1 to 10 days. The 
pressure is not specifically limited, but desirably the synthesis is 
carried out under the mixture's own pressure. 
The hydrothermal synthesis reaction is effected by heating the material 
mixture to a desired temperature and, with stirring where necessary, kept 
on until a crystalline silicate forms. Following the crystallization, the 
reaction mixture is cooled down to room temperature, filtered, rinsed with 
water, and separated. Usually, the product is further dried at 100.degree. 
C. or above for about 5 to 24 hours. 
The term "composite crystalline silicate" as used herein means a composite 
crystalline silicate of a structure formed by first synthesizing a 
crystalline silicate in the aforesaid manner as a mother crystal and then 
allowing a crystalline silicate (to be called "silicalite" hereinafter) 
which comprises Si and O and has the same structure as the mother crystal 
to grow thereon. 
The crystalline silicate serving as the mother crystal is desirably one 
which is represented, in a dehydrated state and in terms of the molar 
ratio of oxides, by the following chemical formula: 
EQU (1.+-.0.6)R.sub.2 O.[aM.sub.2 O.sub.3.bAl.sub.2 O.sub.3 ].cMeO.ySiO.sub.2, 
wherein R is an alkali metal ion and/or hydrogen ion, M is the ion of at 
least one element selected from the group consisting of Group VIII 
elements, rare earth elements, titanium, vanadium, chromium, niobium, 
antimony, and gallium, Me is an alkaline earth element, a.gtoreq.0, 
b.gtoreq.0, c.gtoreq.0, a+b=1, y/c&gt;12, and y&gt;12, said crystalline silicate 
having an X-ray diffraction pattern shown in Table 1 above. 
One method for the crystal growth of silicalite on the outer surface of the 
crystalline silicate serving as the mother crystal is hydrothermal 
synthesis. For the crystal growth of silicalite on the outer surface of 
the mother crystal by hydrothermal synthesis, water glass, silica sol or 
the like is employed as a silica source. The alkali metal ion to be used 
is, e.g., sodium oxide or sodium hydroxide in water glass, and the 
crystallizing mineralizer is, e.g., tetrapropylammonium bromide. 
The proportion of the silicalite to be grown as crystal with respect to the 
crystalline silicate as the mother crystal is desirably, in terms of the 
silicalite/mother crystal weight ratio, from 0.01 to 100 for the 
synthesis. Also, as a prerequisite for the crystal growth of silicalite on 
the mother crystal, the mixing ratios of the materials should be: OH.sup.- 
/SiO.sub.2 =0.01 to 10, H.sub.2 O/SiO.sub.2 =1 to 1000, and organic matter 
(e.g., tetrapropylammonium compound)/SiO.sub.2 =0 to 10. 
The synthesis procedure consists of adding finely powdered mother crystals 
to the above mixture, stirring the whole mixture homogeneously, heating it 
with stirring at 80 to 200.degree. C. for 1 to 200 hours, removing excess 
ions by water rinsing, drying, and baking. In this way a composite 
crystalline silicate according to the present invention is obtained. 
The catalyst is prepared by immersing the composite crystalline silicate in 
an aqueous solution of a salt of a Group Ib or VIII metal, e.g., copper or 
cobalt, and allowing the silicate to support the metal ion by ion exchange 
or by impregnation with an aqueous solution of a metal salt, such as 
chloride or nitrate. 
The use of a silicalite-covered composite crystalline silicate improves the 
durability of the resulting catalyst for the following reason. In exhaust 
emissions are present such gases as NO, CO, hydrocarbons, H.sub.2 O 
(steam), and O.sub.2. The exhaust is purified at the active reaction sites 
of the catalyst while, at the same time, the presence of high temperature 
H.sub.2 O tends to cause metals to separate from the silicate 
(demetallization). However, the coating of silicalite, which is 
hydrophobic by nature, makes it difficult for H.sub.2 O alone to permeate 
deep into the crystalline silicate. As a consequence, the H.sub.2 O 
concentrations around the active reaction sites in the catalyst are low 
and the demetallization is inhibited. 
Moreover, in the catalyst according to the fourth aspect of the invention, 
the alkaline earth element contained in the mother crystal weakens the 
strongly acidic sites in the silicate which would otherwise promote the 
removal of metal from the resulting catalyst and thereby inhibits the 
demetallization in the presence of high-temperature steam. 
As discussed in connection with the first to fourth aspects above, the 
catalyst for exhaust gas purification in accordance with the invention is 
highly durable and stable. It is useful as a catalyst for purifying 
exhaust gases from lean-burn gasoline engines and diesel engines of motor 
vehicles. 
In the following the present invention will be described in further detail 
with reference to a number of embodiments for this invention and 
comparative examples for conventional catalyst.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The first aspect of the invention will now be described in detail by way of 
Examples 1 to 3 and Comparative Example 1. 
EXAMPLE 1 
Catalysts for describing the first aspect of this invention were prepared 
in the following way. 
Synthesis of alkaline earth metal-containing silicate 1A 
A solution prepared by dissolving 395.5 g of aluminum nitrate and 94.4 g of 
calcium acetate in 6552 g of water was designated solution 1A. Solution 1B 
was prepared by dissolving 4212 g of water glass sold as "Cataloid SI-30" 
(a product of Catalysts & Chemicals Industries Co., Japan, contg. 30.5% 
SiO.sub.2 and 0.42% Na.sub.2 O) in 2808 g of water. Solution 1B was added 
to solution 1A with vigorous stirring. Next, a solution of 234 g sodium 
hydroxide in 1404 g water and then a solution of 568.6 g 
tetrapropylammonium bromide (TPABr) in 2106 g water were added. Stirring 
was continued for about 10 minutes, and an aqueous gel mixture resulted. 
The molar ratios of the components were: SiO.sub.2 /Al.sub.2 O.sub.3 =40 
and SiO.sub.2 /CaO=40. 
This aqueous gel mixture was charged into an autoclave having a capacity of 
20 liters and hydrothermally treated at the charge's own pressure and at 
160.degree. C. for 72 hours with stirring (at 200 rpm). Following the 
treatment, the reaction product was centrifuged for solid-liquid 
separation. The solid matter was thoroughly washed with water and dried at 
120.degree. C. for 5 hours in the air. It was then baked at 500.degree. C. 
for 5 hours. The Ca-containing crystalline silicate thus obtained is 
herein referred to as silicate 1A. 
Synthesis of alkaline earth metal-containing silicates 1B-1N 
The procedure described above for the synthesis of the alkaline earth 
metal-containing silicate 1A was repeated except for changes in the 
alkaline earth salts used as an ingredient and in compositional 
formulation to obtain various alkaline earth metal-containing silicates 1B 
to 1N. The proportions of ingredients are listed in Table 2 below. 
Preparation of catalysts 
Alkaline earth metal-containing silicates 1A to 1N were subjected to copper 
ion exchange by immersion in a 0.04M aqueous copper acetate with stirring, 
and after 24-hour stirring at room temperature they were rinsed. This 
cycle of copper ion exchange was repeated three times each with a fresh 
supply of the solution. Final rinsing and drying gave powder catalysts 1a 
to 1n. 
To 100 parts of each of the powder catalysts added as binders were 3 parts 
of alumina sol, 55 parts of silica sol, and 230 parts of water. The 
mixtures upon thorough stirring afforded slurries for wash coating. 
Divided portions of cordierite type monolithic substrates (with a 400-cell 
lattice pattern) were separately dipped in the slurries and taken out, 
excess slurries were blown away, and then dried at 200.degree. C. The 
coating weighed 200 g per liter of the substrate. The coated substrates 
are designated as honeycomb catalysts 1A to 1N. 
TABLE 2 
__________________________________________________________________________ 
"Cataloid" Alkaline earch Charge Conditions for 
Silicate 
SI-30 Al(NH.sub.3).sub.2.9H.sub.2 O 
NaOH 
TPABr 
metal salt composition hydrothermal 
No. (g) (g) (g) (g) Type (g) 
SiO.sub.2 /Al.sub.2 O.sub.3 
SiO.sub.2 /MO 
synthesis 
__________________________________________________________________________ 
1A 4212 395.5 234 568.6 
Ca(CH.sub.3 COO).sub.2.H.sub. 
94.4 
40 M:Ca 40 
160.degree. C. 
.times. 72 hr 
1B " " " " Mg(CH.sub.3 COO).sub.2.4H.sub.2 O 
114.7 
40 M:Mg 40 
" 
1C " " " " Sr(CH.sub.3 COO).sub.2.1/2H.sub.2 O 
113.0 
40 M:Sr 40 
" 
1D " " " " Ba(CH.sub.3 COO).sub.2.H.sub.2 O 
143.5 
40 M:Ba 40 
" 
1E " " " " Ca(CH.sub.3 COO).sub.2.H.sub.2 O 
47.2 
40 M:Ca 80 
" 
1F " " " " Ca(CH.sub.3 COO).sub.2.H.sub.2 O 
188.8 
40 M:Ca 20 
" 
1G " " " " Ca(NO.sub.3).sub.2.4H.sub.2 O 
126.5 
40 M:Ca 40 
" 
1H " " " " Ba(NO.sub.3).sub.2. 
104.6 
40 M:Ba 40 
" 
1I " " " 94.6 
Ca(CH.sub.3 COO).sub.2.H.sub.2 O 
94.4 
40 M:Ca 40 
" 
1J " 197.8 " 568.6 
Ca(CH.sub.2 COO).sub.2.H.sub.2 O 
94.4 
80 M:Ca 40 
" 
1K " " " " CaCl.sub.2.2H.sub.2 O 
78.8 
80 M:Ca 40 
" 
1L " " " " Sr(CH.sub.3 COO).sub.2.1/2H.sub.2 O 
113.0 
80 M:Sr 40 
" 
1M " " " " Ba(CH.sub.3 COO).sub.2.H.sub.2 O 
143.5 
80 M:Ba 40 
" 
1N " " " " Mg(CH.sub.3 COO).sub.2.4H.sub.2 O 
114.7 
80 M:Mg 40 
" 
1O 4212 395.5 234 568.6 
-- 40 -- 160.degree. C. 
.times. 72 hr 
1P " 197.8 " " -- 80 -- " 
__________________________________________________________________________ 
EXAMPLE 2 
Divided portions of silicate 1A obtained in Example 1 were immersed with 
agitation in 0.04M aqueous solutions of cuptic chloride, cobalt chloride, 
nickel chloride, ferric chloride, and silver nitrate, and in the same way 
as described in Example 1, powder catalysts 1O to 1S were prepared. 
These powder catalysts were supported by monolithic substrates in the 
manner described in Example 1, and honeycomb catalysts 1O to 1S were 
obtained. 
EXAMPLE 3 
Silicate 1A prepared in Example 1, with the addition of a binder, was 
applied to a cordieritc type monolithic substrate to form a coating. 
Divided portions of the coated monolithic substrate were separately 
immersed for impregnation over a one-hour period in a solution of cuprous 
chloride in hydrochloric acid (26.8 g in 200 cm.sup.3 of HCl), aqueous 
cupric chloride solution (46.1 g in 200 cm.sup.3 of water), aqueous cobalt 
chloride (64.4 g in 200 cm.sup.3 of water), aqueous nickel chloride (64.4 
g in 200 cm.sup.3 of water), aqueous solution mixture of cupric chloride 
and cobalt chloride (23.1 g of CuCl.sub.2.2H.sub.2 O and 32.2 g of 
CoCl.sub.2.6H.sub.2 O in 200 cm.sup.3 of water), and aqueous solution 
mixture of nickel chloride and cobalt chloride (32.2 g of 
NiCl.sub.2.2H.sub.2 O and 32.2 g of CoCl.sub.2.6H.sub.2 O in 200 cm.sup.3 
of water), respectively. The solutions left on the walls of the substrates 
were wiped off, and the coated substrates were dried at 200.degree. C. A 
12-hour purging in a nitrogen atmosphere at 500.degree. C. yielded 
honeycomb catalysts 1T to 1Y. 
COMATIVE EXAMPLE 1 
Two types of crystalline silicates were synthesized by the same method as 
described in Example 1 with the exception that no alkaline earth metal was 
added. The material proportions of these silicates, designated as 1O and 
1P, are also given in Table 2. 
These silicates 1O and 1P were subjected to Cu ion exchange in the same 
manner as for the catalyst preparation in Example 1 to obtain powder 
catalysts 1t and 1u. Likewise monolithic substrates were coated with them 
to give honeycomb catalysts 1Z and 1ZA. The details of thus obtained 
honeycomb catalysts 1A to 1ZA are summarized in Table 3. 
EXPERIMENT 1 
Honeycomb catalysts 1A to 1ZA prepared in Examples 1 to 3 and in 
Comparative Example 1 were tested for the evaluation of their activities. 
The conditions for activity evaluation were as follows. 
Gas composition 
NO=400 ppm; CO=1000 ppm; C.sub.2 H.sub.4 =1000 ppm; C.sub.3 H.sub.6 =340 
ppm; O.sub.2 =8%; CO.sub.2 =10%; H.sub.2 O=10%; the remainder=N.sub.2 ; 
GHSV=30000 hr.sup.-1 ; catalyst shape=15 mm.times.15 mm.times.60 mm (144 
cells); reaction temperature=350.degree. C. 
The denitration rates of the catalysts in the initial state at 450.degree. 
C. are given in Table 4. 
EXPERIMENT 2 
As a durability test the catalysts were forced to deteriorate with the 
supply of a gaseous mixture consisting of 10% H.sub.2 O and the balance 
N.sub.2 gas at a GHSV of 30000 hr.sup.-1 for 24 hours. 
The forcibly deteriorated honeycomb catalysts 1A to 1ZA were evaluated for 
their activities under the same conditions as used in Experiment 1. The 
results are also shown in Table 4. 
As Table 4 indicates, honeycomb catalysts 1A to 1Y prepared using alkaline 
earth metal-containing silicates had high denitration activities after the 
forced deterioration as well as in the initial state, proving that they 
were durable. 
Table 4 also indicates that the ordinary silicate catalysts (honeycomb 
catalysts 1Z and 1ZA) showed substantial reductions in activity after the 
forced deterioration, revealing that they were less durable. 
TABLE 3 
__________________________________________________________________________ 
Qty of active 
substance supported 
Honeycomb 
Powder (mmol per gram 
Type of silicate 
catalyst No. 
catalyst No. 
of silicate) 
No. 
SiO.sub.2 /Al.sub.2 O.sub.3 
SiO.sub.2 /MO 
__________________________________________________________________________ 
1A 1a Cu (0.55) 1A 40 M:Ca 40 
1B 1b Cu (0.5) 1B 40 M:Mg 40 
1C 1c Cu (0.55) 1C 40 M:Sr 40 
1D 1d Cu (0.5) 1D 40 M:Ba 40 
1E 1e Cu (0.5) 1E 40 M:Ca 80 
1F 1f Cu (0.45) 1F 40 M:Ca 20 
1G 1g Cu (0.4) 1G 40 M:Ca 40 
1H 1h Cu (0.45) 1H 40 M:Ba 40 
1I 1i Cu (0.5) 1I 40 M:Ca 40 
1J 1j Cu (0.4) 1J 80 M:Ca 40 
1K 1k Cu (0.35) 1K 80 M:Ca 40 
1L 1l Cu (0.45) 1L 80 M:Sr 40 
1M 1m Cu (0.4) 1M 80 M:Ba 40 
1N 1n Cu (0.35) 1N 80 M:Mg 40 
1O 1o Cu (0.55) 1A 40 M:Ca 40 
1P 1p Co (0.5) 1A 40 M:Ca 40 
1Q 1q Ni (0.55) 1A 40 M:Ca 40 
1R 1r Fe (0.35) 1A 40 M:Ca 40 
1S 1s Ag (0.8) 1A 40 M:Ca 40 
1T -- Cu (0.8) 1A 40 M:Ca 40 
1U -- Cu (0.8) 1A 40 M:Ca 40 
1V -- Co (0.8) 1A 40 M:Ca 40 
1W -- Ni (0.8) 1A 40 M:Ca 40 
1X -- Cu(0.4)Co(0.4) 
1A 40 M:Ca 40 
1Y -- Ni(0.4)Co(0.4) 
1a 40 M:Ca 40 
1Z 1t Cu (0.6) 1O 40 -- 
1ZA 1u Cu (0.4) 1P 40 -- 
__________________________________________________________________________ 
TABLE 4 
______________________________________ 
After forced 
Initial activity 
deterioration 
Honeycomb (.eta.NOx %) (.eta.NOx %) 
Catalyst No. 
350.degree. C. 
450.degree. C. 
350.degree. C. 
450.degree. C. 
______________________________________ 
1A 42 39 37 39 
1B 41 40 35 39 
1C 38 42 33 40 
1D 41 39 36 38 
1E 42 39 38 39 
1F 44 41 38 42 
1G 45 41 40 41 
1H 42 43 38 41 
1I 45 41 39 40 
1J 46 43 38 41 
1K 43 41 39 40 
1L 42 39 38 39 
1M 40 40 36 37 
1N 41 42 35 38 
1O 42 40 34 39 
1P 41 39 38 40 
1Q 43 41 36 39 
1R 28 29 28 29 
1S 31 31 30 28 
1T 45 40 35 40 
1U 44 39 39 40 
1V 46 41 36 39 
1W 45 40 35 39 
1X 43 39 36 38 
1Y 41 38 35 38 
1Z 41 38 8 18 
1ZA 42 39 7 17 
______________________________________ 
As for the purification activity against CO and hydrocarbons, honeycomb 
catalysts 1A to 1Y according to the first aspect of the invention showed 
little changes in activity from the initial stage till after the forced 
deterioration. They all achieved 100% removal of those pollutants at both 
350.degree. C. and 450.degree. C. Comparative honeycomb catalysts 1Z and 
1ZA also exhibited initial activities of 100% CO and hydrocarbon removal 
at the two temperature levels. After the forced deterioration, however, 
honeycomb catalyst 1Z showed much lower CO removal rates at 350.degree. C. 
and 450.degree. C. of 15% and 60%, respectively. Its hydrocarbon removal 
rates at the two temperature levels dropped to 45% and 80%. At 350.degree. 
C. and 450.degree. C, honeycomb catalyst 1ZA too showed reduced CO removal 
rates of 10% and 50% and hydrocarbon removal rates of 35% and 70%, 
respectively. 
The second aspect of the invention will now be described in more detail by 
way of Example 4 and Comparative Example 2. 
EXAMPLE 4 
Synthesis of alkaline earth metal-containing silicate 2A 
A solution prepared by dissolving 5616 g of water glass #1 (contg. 30 wt % 
SiO.sub.2) in 5429 g of water is referred to as solution 2A. Into 4175 g 
of water were dissolved 453.6 g of aluminum sulfate (Al.sub.2 
(SO.sub.4).sub.3.17H.sub.2 O), 94.6 g of ferric chloride 
(FeCl.sub.3.6H.sub.2 O), 153.3 g of calcium chloride (CaCl.sub.2.6H.sub.2 
O), 262 g of sodium chloride, and 2020 g of concentrated hydrochloric 
acid. The resulting solution is designated as solution 2B. Solutions 2A 
and 2B were gradually mixed and sufficiently stirred to form a 
precipitate, thus preparing a slurry with pH 8.0. This slurry was charged 
into an autoclave and, with the addition of 500 g tetrapropylammonium 
bromide, the mixture was kept at 160.degree. C. for 72 hours for 
crystallization. The crystalline product was filtered, rinsed, dried, and 
baked in air at 500.degree. C. for 3 hours, and crystalline silicate 2A 
resulted. 
Synthesis of alkaline earth metal-containing crystalline silicates 2B, 2C, 
and 2D 
The procedure for the synthesis of silicate 2A was repeated with the 
exception that calcium chloride (as 6H.sub.2 O salt) was replaced by 142.3 
g of magnesium chloride (as 6H.sub.2 O salt), 186.6 g of strontium 
chloride (as 6H.sub.2 O salt), or 170.9 g of barium chloride (as 2H.sub.2 
O salt) to obtain crystalline silicates 2B, 2C, and 2D, respectively. 
Preparation of catalysts 
With the addition of a binder, powders of crystalline silicates 2A to 2D 
were applied to cordierite monolithic substrates (meshed with 400 cells 
per square inch). The coated substrates were immersed in a 4M aqueous 
NH.sub.4 Cl solution at 80.degree. C. for 24 hours to effect NH.sub.4 ion 
exchange. The ion exchange was followed by rinsing, drying, and baking at 
500.degree. C. for 3 hours to convert the coated crystalline silicates to 
proton type silicates. 
The monolithic catalysts so obtained were then separately dipped separately 
in an aqueous hydrochloric acid solution of CuCl and aqueous solutions of 
CoCl.sub.2, NiCl.sub.2, ZnCl.sub.2, FeCl.sub.3, and MnCl.sub.2. Excess 
liquid was wiped off from the substrate walls, and the catalysts were 
dried at 200.degree. C. Purging in an N.sub.2 atmosphere at 500.degree. C. 
for 12 hours gave catalysts C1 to C28 as listed in Table 5 below. The 
quantity of each metal supported by the crystalline silicate was 0.8 
mmol/g. 
COMATIVE EXAMPLE 2 
As a comparative example, crystalline silicate 2E was obtained by the same 
procedure for the synthesis of crystalline silicate 2A but without the 
addition of calcium chloride. 
Then, catalysts R1 to R7 were prepared for comparison purposes are prepared 
using this crystalline silicate 2E in the same way as with the preparation 
of catalysts C1 to C28 with the supported metal listed in Table 5 below. 
Also, divided portions of the monolithic substrate coated with silicate 2A 
were converted to the proton type in the manner described above and then 
were subjected to ion exchange separately with aqueous solutions of the 
chlorides of Ca, Mg, Sr, and Ba. After water rinsing, drying, and dipping 
in aqueous hydrochloric acid solution of CuCl in the same way as above, 
catalysts R8 to R11 were obtained as comparative examples. 
EXPERIMENT 3 
The monolithic catalysts prepared as above were tested for their catalytic 
performance before and after use in the treatment of a gas consisting of 
10% H.sub.2 O and the balance N.sub.2 at 700.degree. C. and at a GHSV of 
30000 Hr.sup.-1 for 24 hours. Their performance was determined under the 
following conditions. 
Testing conditions 
NO: 400 ppm 
CO: 1000 ppm 
C.sub.2 H.sub.4 : 1000 ppm 
C.sub.3 H.sub.6 : 340 ppm 
O.sub.2 : 8% 
CO.sub.2 : 10% 
H.sub.2 O: 10% 
N.sub.2 : balance 
GHSV: 30000 hr.sup.-1 
The denitration rates at 350.degree. C. and 450.degree. C. are given in 
Table 6. 
TABLE 5 
______________________________________ 
Catalysts prepared 
Crystal- Alkaline earth 
Catalyst line metal in crystalline 
Metal 
No. silicate silicate supported 
______________________________________ 
Example 
C1 2A Ca Cu 
C2 2A Ca Co 
C3 2A Ca Ni 
C4 2A Ca Zn 
C5 2A Ca Fe 
C6 2A Ca Cr 
C7 2A Ca Mn 
C8 2B Mg Cu 
C9 2B Mg Co 
C10 2B Mg Ni 
C11 2B Mg Zn 
C12 2B Mg Fe 
C13 2B Mg Cr 
C14 2B Mg Mn 
C15 2C Sr Cu 
C16 2C Sr Co 
C17 2C Sr Ni 
C18 2C Sr Zn 
C19 2C Sr Fe 
C20 2C Sr Cr 
C21 2C Sr Mn 
C22 2D Ba Cu 
C23 2D Ba Co 
C24 2D Ba Ni 
C25 2D Ba Zn 
C26 2D Ba Fe 
C27 2D Ba Cr 
C28 2D Ba Mn 
Comparative 
Example 
R1 2E None Cu 
R2 2E " Co 
R3 2E " Ni 
R4 2E " Zn 
R5 2E " Fe 
R6 2E " Cr 
R7 2E " Mn 
R8 2E " Cu + Ca 
R9 2E " Cu + Mg 
R10 2E " Cu + Sr 
R11 2E " Cu + Ba 
______________________________________ 
TABLE 6 
______________________________________ 
Denitration rate (%) 
Before After 
treatment treatment 
Catalyst No. 
350.degree. C. 
400.degree. C. 
350.degree. C. 
400.degree. C. 
______________________________________ 
C1 41 40 37 40 
C2 47 41 42 41 
C3 47 39 42 39 
C4 32 40 29 40 
C5 30 29 29 29 
C6 28 25 25 25 
C7 25 33 21 33 
C8 40 39 36 40 
C9 46 40 42 39 
C10 45 40 41 41 
C11 33 41 30 41 
C12 30 28 28 28 
C13 29 24 26 24 
C14 24 34 21 34 
C15 40 42 37 42 
C16 46 40 41 40 
C17 45 41 40 40 
C18 33 41 30 41 
C19 31 29 27 28 
C20 29 25 25 25 
C21 23 32 21 31 
C22 39 40 35 40 
C23 47 41 42 41 
C24 46 40 41 40 
C25 32 40 30 41 
C26 29 27 26 28 
C27 28 24 26 24 
C28 24 31 23 30 
R1 41 39 10 20 
R2 46 40 8 20 
R3 46 41 9 21 
R4 33 39 11 19 
R5 30 29 9 15 
R6 27 24 8 12 
R7 23 31 10 18 
R8 38 41 12 23 
R9 39 40 10 22 
R10 40 41 7 19 
R11 38 39 10 20 
______________________________________ 
Catalysts C1 to C28 according to the second aspect of the present invention 
were found to be clearly superior to comparative catalysts R1 to R11 in 
denitration after the treatment of a gaseous mixture with 10% H.sub.2 O at 
700.degree. C., and it is now obvious that the catalysts of the second 
aspect of the invention is excellently durable and useful as a catalyst 
for the treatment of exhaust gases. 
The third aspect of the present invention will now be described in detail 
by way of Examples 5 to 8 and Comparative Example 3. 
EXAMPLE 5 
Synthesis of mother crystal 3A 
A solution of 5616 g of water glass #1 (contg. 30% SiO.sub.2) in 5429 g of 
water is prepared and referred to as solution 3A. Meanwhile 718.9 g of 
aluminum sulfate, 110 g of ferric chloride, 262 g of sodium chloride, and 
2020 g of concentrated hydrochloric acid are dissolved in 4175 g of water, 
and the solution is designated as solution 3B. Solutions 3A and 3B are fed 
at a predetermined ratio, and the mixture is caused to precipitate. 
Thorough agitation yields a slurry of pH 8.0. 
This slurry is charged into a 20-liter autoclave and, with the addition of 
500 g tetrapropylammonium bromide, the mixture is subjected to 
hydrothermal synthesis at 160.degree. C. for 72 hours. The synthesis is 
followed by water rinsing, drying, and baking at 500.degree. C. for 3 
hours to obtain crystalline silicate 3A. This crystalline silicate is 
represented, in terms of the molar ratio of the oxides (excluding crystal 
water), by the compositional formula: 
EQU 0.5Na.sub.2 O.0.5H.sub.2 O.[0.8Al.sub.2 O.sub.3.0.2Fe.sub.2 O.sub.3 
].25SiO.sub.2 
and has a crystal structure according to an X-ray diffraction analysis as 
shown in Table 1 above. 
Synthesis of composite crystalline silicate A 
One thousand grams of mother crystal A (crystalline silicate A) in a finely 
powdered state is added to 2160 g of water. With the further addition of 
4590 g of colloidal silica (contg. 20% SiO.sub.2), the mixture is 
thoroughly stirred, and the resulting solution is designated solution 3a. 
In the meantime 105.8 g of sodium hydroxide is dissolved in 2008 g of 
water to prepare solution 3b. While solution 3a is kept under agitation, 
solution 3b is slowly added drop-wise into solution 3a to form a 
precipitate and obtain a slurry. 
This slurry is placed in an autoclave and a solution of 568 g 
tetrapropylammonium bromide in 2106 g of water is added. Inside the 
autoclave hydrothermal synthesis is carried out at 160.degree. C. for 72 
hours (with stirring at 200 rpm). After the stirring, the synthesis 
product is rinsed, dried, and baked at 500.degree. C. for 3 hours to yield 
composite crystalline silicate 3A. 
Preparation of catalysts 
The composite crystalline silicate 3A was subjected to copper ion exchange 
by immersion in a 0.04M aqueous copper acetate solution at 30.degree. C. 
with stirring. After 24-hour stirring, it was rinsed, and this cycle was 
repeated to conduct the copper ion exchange with the aqueous solution 
three times. Final rinsing and drying gave powder catalyst 3a. 
To 100 parts of powder catalyst 3a added as binders were 3 parts of alumina 
sol, 55 parts of silica sol (contg. 20% SiO.sub.2), and 200 parts of 
water. The mixture on thorough stirring afforded a slurry for wash 
coating. A monolithic substrate (with a 400-cell lattice pattern) for 
cordierite was dipped in the slurry and taken out, excess slurry was blown 
away, and then dried at 200.degree. C. The coating so supported weighed 
200 g per liter of the substrate, and this coated matter is designated as 
honeycomb catalyst 3A. 
EXAMPLE 6 
Mother crystals 3B to 3L were prepared by repeating the procedure for the 
synthesis of the mother crystal 3A in Example 5 with the exception that 
the ferric chloride was replaced by the chlorides of cobalt, ruthenium, 
rhodium, lanthanum, cerium, titanium, vanadium, chromium, antimony, 
gallium, or niobium, respectively, each in the same molar amount as 
Fe.sub.2 O.sub.3 in terms of equivalency as oxide. The compositions of 
these mother crystals are represented, as the molar ratio of the oxides 
(in the dehydrated state), by the formula: 
EQU 0.5Na.sub.2 O0.5H.sub.2 O.(0.2M.sub.2 O.sub.3.0.8Al.sub.2 
O.sub.3).25SiO.sub.2, 
wherein M is Co, Ru, Rh, La, Ce, Ti, V, Cr, Sb, Ga, or Nb, constituting 
mother crystals 3B to 3L, respectively. 
In the same manner as with mother crystal 3A but without the addition of 
the ferric chloride, mother crystal 3M was obtained. 
These mother crystals 3B to 3M were finely powdered and used in place of 
mother crystal 3A in the synthesis of the crystalline silicate in Example 
5. Repeated runs of hydrothermal synthesis using the autoclave gave 
laminar composite crystalline silicates 3B to 3M. 
Using these crystalline silicates 3B to 3M, the procedure of Example 5 for 
the preparation of a catalyst was repeated, and powder catalysts 3b to 3m 
were obtained. These powder catalysts were used to coat monolithic 
substrates of cordierite, in the same way as in the preparation of 
catalyst in Example 5, and honeycomb catalysts 3B to 3M were obtained. 
EXAMPLE 7 
Divided portions of composite crystalline silicate 3A obtained in Example 5 
were immersed with agitation in 0.04M aqueous solutions of cupric 
chloride, cobalt chloride, nickel chloride, ferric chloride, and silver 
nitrate at 60.degree. C. for ion exchange with the respective metals. 
Then, in the same way as described in Example 5, powder catalysts 3n to 3r 
were prepared. 
These powder catalysts were supported by monolithic substrates in the 
manner described in Example 5, and honeycomb catalysts 3N to 3R were 
obtained. 
EXAMPLE 8 
Composite crystalline silicate A prepared in Example 5 was immersed in a 4N 
aqueous NH.sub.4 Cl solution at 80.degree. C. and was stirred for 24 hours 
for NH.sub.4 ion exchange. Following the ion exchange, the product was 
rinsed, dried at 100.degree. C. for 24 hours, and baked at 500.degree. C. 
for 3 hours to give H type crystalline silicate 3A. With the addition of a 
binder, this silicate 3A was applied to a cordierite type monolithic 
substrate as a coating. 
Divided portions of the coated monolithic substrate were separately 
immersed for impregnation over a one-hour period in a cuprous chloride 
solution in hydrochloric acid (26.8 g in 200 cm.sup.3 of HCl), aqueous 
cupric chloride solution (46.1 g in 200 cm.sup.3 of water), aqueous cobalt 
chloride solution (64.4 g in 200 cm.sup.3 of water), aqueous nickel 
chloride solution (64.4 g in 200 cm.sup.3 of water), aqueous solution 
mixture of cupric chloride and cobalt chloride (23.1 g CuCl.sub.2.2H.sub.2 
O and 32.2 g CoCl.sub.2.6H.sub.2 O in 200 cm.sup.3 of water), and aqueous 
solution mixture of nickel chloride and cobalt chloride (32.2 g 
NiCl.sub.2.2H.sub.2 O and 32.2 g CoCl.sub.2.6H.sub.2 O in 200 cm.sup.3 of 
water), respectively. The solutions left on the walls of the substrates 
were wiped off, and the coated substrates dried at 200.degree. C. A 
12-hour purging in a nitrogen atmosphere at 500.degree. C. gave honeycomb 
catalysts 3S to 3X. 
COMATIVE EXAMPLE 3 
Mother crystal 3M obtained in Example 6 was directly subjected to Cu ion 
exchange in the same manner as with the preparation of catalyst in Example 
5 to obtain powder catalyst 3m'. Likewise a monolithic substrate was 
coated with it to yield honeycomb catalyst 3Y. 
EXPERIMENT 4 
Honeycomb catalysts 3A to 3Y prepared in Examples 5 to 8 and in Comparative 
Example 3 were tested for the evaluation of their activities. The 
conditions for activity evaluation were as follows. 
Gas composition 
NO=400 ppm; CO=1000 ppm; C.sub.2 H.sub.4 =1000 ppm; C.sub.3 H.sub.6 =340 
ppm; O.sub.2 =8%; CO.sub.2 =10%; H.sub.2 O=10%; the remainder=N.sub.2 ; 
(144 cells). 
The denitration rates of the catalysts in the initial state at reaction 
temperatures of 350.degree. C. and 450.degree. C. are given in Table 8. 
EXPERIMENT 5 
As a durability test the catalysts were forced to deteriorate with the 
supply of a gaseous mixture consisting of 10% H.sub.2 O and the balance 
N.sub.2 gas at a GHSV of 30000 hr.sup.-1 for 24 hours. 
The forcibly deteriorated honeycomb catalysts 3A to 3Y were evaluated for 
their activities under the same conditions as used in Experiment 4. The 
results are also shown in Table 8. 
As Table 8 indicates, honeycomb catalysts 3A to 3X prepared using composite 
crystalline silicates had high denitration activities after the forced 
deterioration as well as in the initial state, proving that they were 
durable. The table also shows that the ordinary silicate catalyst 
(honeycomb catalyst 3Y) lost much of its activity after the forced 
deterioration, revealing that it was less durable. 
TABLE 7 
__________________________________________________________________________ 
Powder catalyst 
Qty of active 
Honeycomb substance supported 
Composite crystalline silicate 
catalyst No. 
No. 
(mmol/g) No. Composition* 
__________________________________________________________________________ 
3A 3a Cu(0.45) 3A S.L/0.5Na.sub.2 O.0.5H.sub.2 O(0.2Fe.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3) 
3B 3b Cu(0.40) 3B S.L/0.5Na.sub.2 O.0.5H.sub.2 O(0.2Co.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3) 
3C 3c Cu(0.35) 3C S.L/0.4Na.sub.2 O.0.5H.sub.2 O(0.2Ru.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3) 
3D 3d Cu(0.40) 3D S.L/0.5Na.sub.2 O.0.4H.sub.2 O(0.2Rh.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3) 
3E 3e Cu(0.45) 3E S.L/0.5Na.sub.2 O.0.5H.sub.2 O(0.2La.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3) 
3F 3f Cu(0.40) 3F S.L/0.6Na.sub.2 O.0.4H.sub.2 O(0.2Ce.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3) 
3G 3g Cu(0.45) 3G S.L/0.5Na.sub.2 O.0.6H.sub.2 O(0.2Ti.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3) 
3H 3h Cu(0.35) 3H S.L/0.4Na.sub.2 O.0.6H.sub.2 O(0.2V.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3) 
3I 3i Cu(0.40) 3I S.L/0.5Na.sub.2 O.0.6H.sub.2 O(0.2Cr.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3) 
3J 3j Cu(0.45) 3J S.L/0.6Na.sub.2 O.0.4H.sub.2 O(0.2Sb.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3) 
3K 3k Cu(0.40) 3K S.L/0.6Na.sub.2 O.0.5H.sub.2 O(0.2Ga.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3) 
3L 3l Cu(0.50) 3L S.L/0.5Na.sub.2 O.0.5H.sub.2 O(0.2Nb.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3) 
3M 3m Cu(0.40) 3M S.L/0.4Na.sub.2 O.0.4H.sub.2 O.0.8Al.sub.2 
O.sub.3 
3N 3n Cu(0.40) 3A S.L/0.5Na.sub.2 O.0.4H.sub.2 O(0.2Fe.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3) 
3O 3o Co(0.35) 3A " 
3P 3p Ni(0.30) 3A " 
3Q 3q Fe(0.30) 3A " 
3R 3r Ag(0.70) 3A " 
3S -- CU(0.80) 3A(H type) 
S.L/H.sub.2 O.(0.2Fe.sub.2 O.sub.3.0.8Al.sub.2 
O.sub.3) 
3T -- Cu(0.80) 3A(H type) 
" 
3U -- Co(0.80) 3A(H type) 
" 
3V -- Ni(0.40) 3A(H type) 
" 
3W -- Cu(0.40) 3A (type) 
" 
Co(0.40) 
3X -- Ni(0.40) 3A (type) 
" 
Co(0.40) 
3Y m' Cu(0.40) 0.4Na.sub.2 O.0.8Al.sub.2 O.sub.3 (without 
__________________________________________________________________________ 
S.L) 
*In the composition, the symbol S.L stands for silicalite, and 25SiO.sub. 
is omitted because it is common to all the compositions. 
TABLE 8 
______________________________________ 
Honey- 
Powder catalyst Activity 
comb Qty of active 
Initial after forced 
cata- substance activity deterioration 
lyst supported (.eta.NOx %) 
(.eta.NOx %) 
No. No. (mmol/g) 350.degree. C. 
450.degree. C. 
350.degree. C. 
450.degree. C. 
______________________________________ 
3A 3a Cu(0.45) 41 40 38 36 
3B 3b Cu(0.40) 39 38 37 35 
3C 3c Cu(0.35) 40 41 37 36 
3D 3d Cu(0.40) 38 40 38 35 
3E 3e Cu(0.45) 39 41 39 38 
3F 3f Cu(0.40) 37 40 35 35 
3G 3g Cu(0.45) 38 41 36 35 
3H 3h Cu(0.35) 37 38 36 35 
3I 3i Cu(0.40) 38 36 35 34 
3J 3j Cu(0.45) 37 40 36 33 
3K 3k Cu(0.40) 38 39 37 34 
3L 3l Cu(0.50) 38 41 36 37 
3M 3m Cu(0.40) 38 40 39 35 
3N 3n Cu(0.40) 38 36 34 33 
3O 3o Co(0.35) 38 40 36 35 
3P 3p Ni(0.30) 36 40 38 36 
3Q 3q Fe(0.30) 35 40 36 34 
3R 3r Ag(0.70) 36 38 35 33 
3S -- Cu(0.80) 35 36 34 33 
3T -- Cu(0.80) 36 35 33 32 
3U -- Co(0.80) 36 38 32 33 
3V -- Ni(0.40) 36 38 31 33 
3W -- Cu(0.40) 35 36 31 31 
Co(0.40) 
3X -- Ni(0.40) 35 37 35 32 
Co(0.40) 
3Y m' Cu(0.40) 40 41 10 13 
______________________________________ 
With regard to the catalytic activities for the removal of CO and 
hydrocarbons, honeycomb catalysts 3A to 3X according to the third aspect 
of the invention underwent little changes in activity from the initial 
stage till after the forced deterioration. They showed 100% removal rates 
at both 350.degree. C. and 450.degree. C. Comparative honeycomb catalyst 
3Y also had a CO and hydrocarbon purification activity of 100% initially 
at both 350.degree. C. and 450.degree. C. After the forced deterioration, 
however, the CO removal rates of comparative honeycomb catalyst 3Y at 
350.degree. C. and 450.degree. C. declined to 35% and 75%, respectively, 
and the hydrocarbon removal rates at those temperatures also dropped to 
45% and 90%. 
The fourth aspect of the present invention will now be described in detail 
by way of Examples 9 to 12 and Comparative Example 4. 
EXAMPLE 9 
Synthesis of mother crystal 4A 
A solution of 5616 g water glass #1 (contg. 30% SiO.sub.2) in 5429 g of 
water is prepared and referred to as solution 4A. Meanwhile 718.9 g of 
aluminum sulfate, 110 g of ferric chloride, 47.2 g of calcium acetate, 262 
g of sodium chloride, and 2020 g of concentrated hydrochloric acid are 
dissolved in 4175 g of water, and the solution is designated solution 4B. 
Solutions 4A and 4B are fed at a predetermined ratio, and the mixture is 
caused to precipitate. Thorough agitation yields a slurry of pH 8.0. 
This slurry is charged into a 20-liter autoclave and, with the addition of 
500 g of tetrapropylammonium bromide, the mixture is subjected to 
hydrothermal synthesis at 160.degree. C. for 72 hours. The synthesis is 
followed by water rinsing, drying, and baking at 500.degree. C. for 3 
hours to obtain crystalline silicate 4A. This crystalline silicate is 
represented, in terms of the molar ratio of the oxides (excluding crystal 
water), by the compositional formula: 
EQU 0.5Na.sub.2 O.0.5H.sub.2 O.[0.8Al.sub.2 O.sub.3.0.2Fe.sub.2 
O.sub.3.0.25CaO].25SiO.sub.2 
and has a crystal structure according to an X-ray diffraction analysis as 
shown in Table 1 above. 
Synthesis of composite crystalline silicate 4A 
One thousand grams of the mother crystal 4A (crystalline silicate 4A) in a 
finely powdered state is added to 2160 g of water. With the further 
addition of 4590 g of colloidal silica (contg. 20% SiO.sub.2), the mixture 
is thoroughly stirred, and the resulting solution is designated as 
solution 4a. In the meantime 105.8 g of sodium hydroxide is dissolved in 
2008 g of water to prepare solution 4b. While solution 4a is kept under 
agitation, solution 4b is slowly added drop-wise into solution 4a to form 
a precipitate and obtain a slurry. 
This slurry is placed in an autoclave and a solution of 568 g of 
tetrapropylammonium bromide in 2106 g of water is added. Inside the 
autoclave hydrothermal synthesis is carried out at 160.degree. C. for 72 
hours (with stirring at 200 rpm). After the stirring, the synthesis 
product is rinsed, dried, and baked at 500.degree. C. for 3 hours to yield 
laminar composite crystalline silicate 4A. 
Preparation of catalysts 
Composite crystalline silicate 4A was subjected to copper ion exchange by 
immersion in a 0.04M aqueous copper acetate solution at 30.degree. C. with 
stirring. After 24-hour stirring, it was rinsed, and this cycle was 
repeated to conduct the copper ion exchange with the aqueous solution 
Three times. Final rinsing and drying gave powder catalyst 4a. 
To 100 parts of powder catalyst 4a added as binders were 3 parts of alumina 
sol, 55 parts silica sol (contg. 20% SiO.sub.2), and 200 parts water. The 
mixture upon thorough stirring afforded a slurry for wash coating. A 
monolithic substrate (with a 400-cell lattice pattern) for cordierite was 
dipped in the slurry and taken out, excess slurry was blown away, and then 
dried at 200.degree. C. The coating so supported weighed 200 g per liter 
of the substrate, and this coated matter is designated as honeycomb 
catalyst 4A. 
EXAMPLE 10 
Mother crystals 4B to 4L were prepared by repeating the procedure for the 
synthesis of mother crystal 4A in Example 9 with the exception that the 
ferric chloride was replaced by the chlorides of cobalt, ruthenium, 
rhodium, lanthanum, cerium, titanium, vanadium, chromium, antimony, 
gallium, and niobium, respectively, each in the same molar amount as 
Fe.sub.2 O.sub.3 in terms of equivalency as oxide. The compositions of 
these mother crystals are represented, as the molar ratio of the oxides 
(in the dehydrated state), by the formula: 
EQU 0.5Na.sub.2 O.0.5H.sub.2 O.[0.2M.sub.2 O.sub.3.0.8Al.sub.2 
O.sub.3.0.25CaO].25SiO.sub.2 
wherein M is Co, Ru, Rh, La, Ce, Ti, V, Cr, Sb, Ga, or Nb, constituting 
mother crystals 4B to 4L, respectively. 
In the same manner as with mother crystal 4A but without the addition of 
the ferric chloride and calcium acetate, mother crystal 4M was obtained. 
These mother crystals 4B to 4M were finely powdered and used in place of 
mother crystal 4A in the synthesis of the crystalline silicate in Example 
9. Repeated runs of hydrothermal synthesis using the autoclave gave 
composite crystalline silicates 4B to 4M. 
Using these crystalline silicates 4B to 4M, the procedure of Example 9 for 
the preparation of a catalyst was repeated, and powder catalysts 4b to 4m 
were obtained. These powder catalysts were used to coat monolithic 
substrates of cordierite, in the same way as in the preparation of 
catalyst in Example 9, and honeycomb catalysts 4B to 4M were obtained. 
EXAMPLE 11 
In the synthesis of mother crystal 4A in Example 9 calcium acetate was 
replaced by magnesium acetate, strontium acetate, or barium acetate, each 
in the same molar amount as CaO in terms of equivalency as oxide, and 
otherwise the same procedure with the mother crystal 4A was repeated to 
prepare mother crystals 4N to 4P. The compositions of these mother 
crystals, in terms of the molar ratio of the oxides (in a dehydrated 
state) were represented by: 
EQU 0.5Na.sub.2 O.0.5H.sub.2 O.(0.2Fe.sub.2 O.sub.3.0.8Al.sub.2 
O.sub.3.0.25MeO).25SiO.sub.2 
wherein Me is Mg, Sr, or Ba. These mother crystals were finely ground and 
were subjected to hydrothermal synthesis using the autoclave in the same 
manner as with the synthesis of the crystalline silicates in Example 9 to 
obtain crystalline silicates 4N to 4P. From these silicates 4N to 4P, 
powder catalysts 4n to 4p and then honeycomb catalysts 4N to 4P were 
obtained by following the procedure of Example 9. 
EXAMPLE 12 
Divided portions of composite crystalline silicate 4A obtained in Example 9 
were immersed with agitation in 0.04M aqueous solutions of cupric 
chloride, cobalt chloride, nickel chloride, ferric chloride, and silver 
nitrate at 60.degree. C. for ion exchange with the respective metals. 
Then, in the same way as described in Example 9, powder catalysts 4q to 4u 
were prepared. 
These powder catalysts were supported by monolithic substrates in the 
manner described in Example 9, and honeycomb catalysts 4Q to 4U were 
obtained. 
EXAMPLE 13 
The crystalline silicate 4A prepared in Example 9 was immersed in a 4N 
aqueous NH.sub.4 Cl solution at 80.degree. C. and was stirred for 24 hours 
for NH.sub.4 ion exchange. Following the ion exchange, the product was 
rinsed, dried at 100.degree. C. for 24 hours, and baked at 500.degree. C. 
for 3 hours to give H type crystalline silicate 4A'. With the addition of 
binder, this silicate 4A' was applied to a cordierite type monolithic 
substrate as a coating. 
Divided portions of the coated monolithic substrate were separately 
immersed for impregnation over a one-hour period in a solution of cuprous 
chloride in hydrochloric acid (26.8 g in 200 cm.sup.3 of HCl), aqueous 
cupric chloride solution (46.1 g in 200 cm.sup.3 of water), aqueous cobalt 
chloride solution (64.4 g in 200 cm.sup.3 of water), aqueous nickel 
chloride (64.4 g in 200 cm.sup.3 of water), aqueous solution mixture of 
cupric chloride and cobalt chloride (23.1 g CuCl.sub.2.2H.sub.2 O and 32.2 
g CoCl.sub.2.6H.sub.2 O in 200 cm.sup.3 of water), and aqueous solution 
mixture of nickel chloride and cobalt chloride (32.2 g NiCl.sub.2.2H.sub.2 
O and 32.2g CoCl.sub.2.6H.sub.2 O in 200 cm.sup.3 of water), respectively. 
The solutions left on the walls of the substrates were wiped off, and the 
coated substrates dried at 200.degree. C. A 12-hour purging in a nitrogen 
atmosphere at 500.degree. C. gave honeycomb catalysts 4V to 4.alpha.. 
COMATIVE EXAMPLE 4 
Mother crystal 4M obtained in Example 10 was directly subjected to Cu ion 
exchange in the same manner as with the preparation of catalyst in Example 
9 to obtain powder catalyst 4m'. Likewise a monolithic substrate was 
coated with it to yield honeycomb catalyst 4.beta.. 
EXPERIMENT 6 
Honeycomb catalysts 4A to 4.beta. prepared in Examples 9 to 13 and in 
Comparative Example 4 were tested for the evaluation of their activities. 
The conditions for activity evaluation were as follows. 
Gas composition 
NO=400 ppm; CO=1000 ppm; C.sub.2 H.sub.4 =1000 ppm; C.sub.3 H.sub.6 =340 
ppm; O.sub.2 =8%; CO.sub.2 =10%; H.sub.2 O=10%; the remainder=N.sub.2 ; 
GHSV=30000 hr.sup.-1 ; catalyst shape=15 mm.times.15 mm.times.60 mm (144 
cells). 
The denitration rates of the catalysts in the initial state at reaction 
temperatures of 350.degree. C. and 450.degree. C. are given in Table 10. 
EXPERIMENT 7 
As a durability test the catalysts were forced to deteriorate with the 
supply of a gaseous mixture consisting of 10% H.sub.2 O and the balance 
N.sub.2 gas at a GHSV of 30000 hr.sup.-1 for 24 hours. The forcibly 
deteriorated honeycomb catalysts 4A to 4.beta. were evaluated for their 
activities under the same conditions as used in Experiment 6. The results 
are also shown in Table 10. 
As Table 10 indicates, the honeycomb catalysts 4A to 4.alpha. prepared 
using composite crystalline silicates according to the fourth aspect of 
the invention had high denitration activities after the forced 
deterioration as well as in the initial state, proving that they were 
durable. The table also shows that the ordinary silicate catalyst 
(honeycomb catalyst 4.beta.) lost much of its activity after the forced 
deterioration, revealing that it was less durable. 
TABLE 9 
__________________________________________________________________________ 
Powder catalyst 
Qty of active 
Honeycomb substance supported 
Composite crystalline silicate 
catalyst No. 
No. 
(mmol/g) No. Composition* 
__________________________________________________________________________ 
A a Cu(0.45) A S.L/0.5Na.sub.2 O.0.5H.sub.2 O(0.2Fe.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3.0.25CaO) 
B b Cu(0.40) B S.L/0.5Na.sub.2 O.0.5H.sub.2 O(0.2Co.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3.0.25CaO) 
C c Cu(0.35) C S.L/0.4Na.sub.2 O.0.5H.sub.2 O(0.2Ru.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3.0.25CaO) 
D d Cu(0.40) D S.L/0.5Na.sub.2 O.0.4H.sub.2 O(0.2Rh.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3.0.25CaO) 
E e Cu(0.45) E S.L/0.5Na.sub.2 O.0.5H.sub.2 O(0.2La.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3.0.25CaO) 
F f Cu(0.40) F S.L/0.6Na.sub.2 O.0.4H.sub.2 O(0.2Ce.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3.0.25CaO) 
G g Cu(0.45) G S.L/0.5Na.sub.2 O.0.6H.sub.2 O(0.2Ti.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3.0.25CaO) 
H h Cu(0.35) H S.L/0.4Na.sub.2 O.0.6H.sub.2 O(0.2V.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3.0.25CaO) 
I i Cu(0.40) I S.L/0.5Na.sub.2 O.0.6H.sub.2 O(0.2Cr.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3.0.25CaO) 
J j Cu(0.45) J S.L/0.6Na.sub.2 O.0.4H.sub.2 O(0.2Sb.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3.0.25CaO) 
K k Cu(0.40) K S.L/0.6Na.sub.2 O.0.5H.sub.2 O(0.2Ga.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3.0.25CaO) 
L l Cu(0.50) L S.L/0.5Na.sub.2 O.0.5H.sub.2 O(0.2Nb.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3.0.25CaO) 
M m Cu(0.40) M S.L/0.4Na.sub.2 O.0.4H.sub.2 O.0.8Al.sub.2 
O.sub.3 
N n Cu(0.45) N S.L/0.5Na.sub.2 O.0.5H.sub.2 O(0.2Fe.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3.0.25MgO) 
O o Cu(0.45) O S.L/0.5Na.sub.2 O.0.5H.sub.2 O(0.2Fe.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3.0.25SrO) 
P p Cu(0.45) P S.L/0.5Na.sub.2 O.0.5H.sub.2 O(0.2Fe.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3.0.25BaO) 
Q q Cu(0.40) A S.L/0.5Na.sub.2 O.0.5H.sub.2 O(0.2Fe.sub.2 
O.sub.3.0.8Al.sub.2 O.sub.3.0.25CaO) 
R r Co(0.35) A " 
S s Ni(0.30) A " 
T t Fe(0.30) A " 
U u Ag(0.70) A " 
V Cu(0.80) A'(H type) 
S.L/H.sub.2 O.(0.2Fe.sub.2 O.sub.3.0.8Al.sub.2 
O.sub.3.0.25CaO) 
W Cu(0.80) A'(H type) 
" 
X Co(0.80) A'(H type) 
" 
Y Ni(0.40) A'(H type) 
" 
Z Cu(0.40) A'(H type) 
" 
Co(0.40) 
.alpha. Ni(0.40) A'(H type) 
" 
Co(0.40) 
.beta. m' Cu(0.40) 0.4Na.sub.2 O.0.8Al.sub.2 O.sub.3 (without 
__________________________________________________________________________ 
S.L) 
In the composition, the symbol S.L stands for silicalite, and 25SiO.sub.2 
is omitted because it is common to all the compositions. 
TABLE 10 
______________________________________ 
Honey- 
Powder catalyst Activity 
comb Qty of active 
Initial after forced 
cata- substance activity deterioration 
lyst supported (.eta.NOx %) 
(.eta.NOx %) 
No. No. (mmol/g) 350.degree. C. 
450.degree. C. 
350.degree. C. 
450.degree. C. 
______________________________________ 
A a Cu(0.45) 40 40 39 36 
B b Cu(0.40) 39 39 37 34 
C c Cu(0.35) 41 41 38 36 
D d Cu(0.40) 38 38 38 34 
E e Cu(0.45) 38 41 37 38 
F f Cu(0.40) 37 40 35 36 
G g Cu(0.45) 38 42 35 35 
H h Cu(0.35) 38 38 36 34 
I i Cu(0.40) 38 35 35 34 
J j Cu(0.45) 37 40 35 32 
K k Cu(.040) 37 39 37 34 
L l Cu(0.50) 38 37 37 36 
M m Cu(0.40) 39 40 39 37 
N n Cu(0.45) 39 36 38 36 
O o Cu(0.45) 40 37 36 35 
P p Cu(0.45) 41 40 37 34 
Q q Cu(0.40) 39 36 35 33 
R r Cu(0.35) 39 40 36 36 
S s Ni(0.30) 36 39 37 36 
T t Fe(0.30) 36 40 37 36 
U u Ag(0.70) 36 39 35 33 
V -- Cu(0.80) 36 36 35 33 
W -- Cu(0.80) 36 38 33 34 
X -- Co(0.80) 35 38 33 33 
Y -- Ni(0.40) 36 39 31 32 
Z -- Cu(0.40) 36 36 33 31 
Co(0.40) 
.alpha. 
-- Ni(0.40) 35 38 35 31 
Co(0.40) 
.beta. 
m' Cu(0.40) 39 42 6 12 
______________________________________