Process for preparing catalysts

A process for preparing novel catalysts of increased activity which comprises (1) mixing alumina with at least one metal compound selected from the group consisting of Group IVB metal compounds and compounds of vanadium, chromium, manganese, tungsten, nickel and cobalt and an aqueous solution containing at least one dissolved compound therein that imparts to said aqueous solution a pH below 6 and (2) thereafter adding to the resulting product at least one metal compound not previously added thereto.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a novel process for preparing novel catalysts of 
increased activity which comprises (1) mixing alumina with at least one 
metal compound selected from the group consisting of Group IVB metal 
compounds and compounds of vanadium, chromium, manganese, tungsten, nickel 
and cobalt and an aqueous solution containing at least one dissolved 
compound therein that imparts to said aqueous solution a pH below 6 and 
(2) thereafter adding to the resulting product at least one metal compound 
not previously added thereto. 
2. Description of the Prior Art 
Catalysts can be prepared that are composed of an alumina support carrying 
metal components thereon, for example, compounds of nickel, titanium or 
molybdenum. 
SUMMARY OF THE INVENTION 
We have found that catalysts of increased activity can be prepared by (1) 
mixing alumina with at least one metal compound selected from the group 
consisting of Group IVB metal compounds and compounds of vanadium, 
chromium, manganese, tungsten, nickel and cobalt and an aqueous solution 
containing at least one dissolved compound therein that imparts to said 
aqueous solution a pH below 6 and (2) thereafter adding to the resulting 
product at least one metal compound not previously added thereto. 
In preparing the novel catalyst herein, four separate and distinct 
components are required in the first stage of such preparation. The first 
component is alumina, which will form the support portion of the novel 
catalyst claimed therein. Any of the known aluminas, or any aluminum 
compound capable of being calcined to alumina in air at a temperature of 
about 200.degree. to about 1200.degree. C. over a period of about 0.5 to 
about 24 hours, can be used. When an uncalcined alumina precursor is used, 
it is preferably selected from any of the well-known groups of hydroxides, 
hydrated oxides, carbonate compounds or mixtures thereof. Examples of such 
compounds are pseudoboehmite, boehmite, bayerite, gibbsite, nordstrandite, 
and ammonium aluminum carbonate hydroxide hydrate. Of these, we prefer to 
employ pseudoboehmite. If a precalcined alumina is used, it can be one or 
more of the well-known aluminas, examples of which are gamma, eta, theta, 
chi, alpha, delta, iota and kappa alumina. Of these, we prefer gamma 
and/or eta alumina. Additionally, precursors or aluminum oxides which are 
non-crystalline can also be utilized. In general the alumina will have an 
average pore radius of about 10 to about 300 .ANG., preferably about 20 
to about 250 .ANG., a surface area of about 350 m.sup.2 /g, and a pore 
volume of from about 0.05 to about 2.0 cc/g, preferably about 0.10 to 
about 1.5 cc/g, when measured by the nitrogen adsorption method (Barrett, 
E. P., Joyner, L. G. and Halenda, P. P., J. Am. Chem. Soc., 73, 373 
(1951)). 
The second component required in the first stage of the claimed process is 
at least one metal compound selected from the group consisting of Group 
IVB metal compounds and compounds of vanadium, chromium, manganese, 
tungsten, cobalt and nickel that is desired to place on the surface of the 
alumina. Any of the metal oxides of the above metals, or compounds of the 
above metals, organic or inorganic, capable of being converted to its 
oxide form under the calcination conditions defined above can be used. Of 
these we prefer to use the corresponding metallic oxides, hydroxides or 
hydrated oxides and carbonates of these metals. Examples of such metal 
compounds are: 
______________________________________ 
TiO.sub.2, WO.sub.3, 
TiO.sub.2.xH.sub.2 O, 
CoO, 
Ti(OC.sub.3 H.sub.7),.sub.4, 
Co(NO.sub.3).sub.2.6H.sub.2 O, 
Ti(OC.sub.4 H.sub.9).sub.4, 
Co(OH).sub.2, 
Ti.sub.2 (C.sub.2 O.sub.4).sub.3.10H.sub.2 O, 
CoCO.sub.3, 
Ti.sub.2 O.sub.3, 
2CoCO.sub.3.Co(OH).sub.2.H.sub.2 O, 
Ti.sub.2 (SO.sub.4).sub.3, 
Co(C.sub.2 H.sub.3 O.sub.2).sub.2.4H.sub.2 O, 
TiOSO.sub.4, Co(C.sub.2 H.sub.3 O.sub.2).sub.3, 
ZrO.sub.2, Co(CHO.sub.2).sub.2.2H.sub.2 O, 
ZrO.sub.2.xH.sub.2 O, 
Co.sub.2 O.sub.3.3H.sub.2 O, 
3ZrO.sub.2.CO.sub.2.H.sub.2 O, 
CoC.sub.2 O.sub.4, 
Zr(OH).sub.4, CoSO.sub.4, 
Zr(NO.sub.3).sub.4.5H.sub.2 O, 
NiO, 
Zr(SO.sub.4).sub.2, 
Ni(NO.sub.3).sub.2.6H.sub.2 O, 
Zr(OC.sub.3 H.sub.7).sub.4, 
Ni(OH.sub.2), 
Zr(O.sub.2 C.sub.5 H.sub.7).sub.4, 
NiCO.sub.3, 
HfO.sub.2, 2NiCO.sub.3.3Ni(OH).sub.2.4H.sub.2 O, 
V.sub.2 O.sub.5, Ni(C.sub.2 H.sub.3 O.sub.2).sub. 2, 
Cr.sub.2 O.sub.3, 
NiC.sub.2 O.sub.4.2H.sub.2 O, 
MnO.sub.2, Ni(CHO.sub.2).sub.2.2H.sub.2 O, and 
NiSO.sub.4 
______________________________________ 
Of these we prefer to use TiO.sub.2 or ZrO.sub.2 alone, most preferably 
TiO.sub.2 alone. 
Also required in the first stage of the process for the preparation of the 
novel catalyst herein is an aqueous solution containing water, as the 
third component, and dissolved therein, as the fourth component; at least 
one compound sufficient to impart to said aqueous solution a pH below 6, 
generally in the range of about 0.1 to about 5.5, but, most preferably, 
from about 1.0 to about 5.0. For such use any water-soluble compound, 
organic or inorganic, but preferably inorganic, that can impart to said 
aqueous solution a pH below 6 can be used. Specific examples of such 
water-soluble compounds that can be used include inorganic acids, such as 
nitric acid, sulfuric acid, hydrofluoric acid, hydrochloric acid, 
phosphoric acid and boric acid, organic acids, such as acetic acid, oxalic 
acid, citric acid, tartaric acid and formic acid, salts, such as aluminum 
nitrate, aluminum chloride, aluminum sulfate, ammonium nitrate, ammonium 
chloride and water-soluble nitrate and chloride salts of transition 
metals, such as iron, chromium, copper, zinc and lanthanum. Of these we 
prefer the mineral acids, nitric acid and hydrochloric acid. Most 
preferred is aqueous nitric acid having a concentration of about five to 
about 90 weight percent, preferably about 10 to about 70 weight percent. 
If desired, for example, to further enhance the catalytic performance of 
the novel catalyst herein, by, for example, increasing activity, altering 
selectivity or prolonging useful lifetime, we can add to the mixture 
obtained from a combination of the above-named four components other metal 
oxide(s) or metal compound(s), organic or inorganic, capable of being 
converted to its oxide form under the calcination conditions defined above 
but which had not been used, as well as those whose metal portions fall 
within Periods 4, 5 and 6 of the Periodic Table and which are selected 
from the groups consisting of IIA, IIIB and IVA of the Periodic Table and 
the elements Mg, Fe, Cu, Zn, Si, Sb, and Bi, or any ammonium compound that 
will decompose or volatilize under the calcination conditions defined 
above. Of these we prefer to use the corresponding metallic oxides, 
hydroxides or hydrated oxides and carbonates as the optional metallic 
component. Specific examples of such compounds include Group IIA metal 
compounds, such as CaO, CaCO.sub.3, SrO and BaO; Group IIIB metal 
compounds, such a Sc.sub.2 O.sub.3, Y.sub.2 O.sub.3, La.sub.2 O.sub.3, 
Ce.sub.2 O.sub.3 and CeO.sub.2 ; Group IVA metal compounds such as 
GeO.sub.2, SnO.sub.2 and PbO, MgO, Fe.sub.2 O.sub.3, CuO, ZnO, SiO.sub.2, 
Sb.sub.2 O.sub.3, Bi.sub.2 O.sub.3, and ammonium compounds, such as 
ammonium hydroxide, ammonium acetate, ammonium nitrate, etc. Of these we 
prefer ammonium hydroxide. 
The resulting mixture when the above four components are combined will 
contain the four components in the following amounts in weight percent. 
TABLE I 
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Weight Percent 
Most 
Broad Preferred Preferred 
Range Range Range 
______________________________________ 
Alumina 15-75 20-60 25-45 
Metallic component(s) 
0.1-25 0.5-10 1-5 
Water 15-80 30-75 50-70 
Acidic Component(s) 
0.001-10 0.01-2 0.1-0.7 
______________________________________ 
When the optional component is added to the above four components in the 
mixture, the resulting mixture will contain each of the components in the 
following amounts in weight percent. 
TABLE II 
______________________________________ 
Weight Percent 
Most 
Broad Preferred Preferred 
Range Range Range 
______________________________________ 
Alumina 15-70 20-50 25-40 
Metallic component(s) 
0.1-25 0.5-10 1-5 
Water 20-75 30-70 50-60 
Acidic Component(s) 
0.001-10 0.01-2 0.1-0.7 
Optional Component(s) 
0.01-20 0.1-10 0.6-7 
______________________________________ 
The mixtures defined above are preferably obtained by intimately mixing 
together, in any desired manner, the four or more components defined above 
until a substantially homogeneous entity is obtained. In an especially 
preferred embodiment, the alumina and the metallic component or components 
are first brought together and mixed, after which they are then further 
mixed with the aqueous solution of desired pH. The resulting paste, or 
slurry, can then be formed into any desired shape following any desired or 
conventional procedure to obtain extrudates or spheres, or the mixture can 
be spray-dried to obtain a fluid catalyst. Following this, the formed 
entity can be dried, for example, at a temperature of about 100.degree. to 
about 200.degree. C. to remove water therefrom, and then, optionally, 
calcined in air at any suitable temperature, for example, in the range of 
about 200.degree. to about 1200.degree. C., preferably from about 
300.degree. to about 800.degree. C., for about 0.5 to about 24 hours, 
preferably for about two to about 20 hours. 
The resulting product, composed of alumina carrying the metallic 
component(s) thereon, can then be treated in the second stage of the 
process for the purpose of adding thereon molybdenum oxide or any 
molybdenum compound, organic or inorganic, capable of being converted to 
its oxide form under any of the calcination conditions defined above. 
Examples of molybdenum compounds that can be used are: 
MoO.sub.3, 
(NH.sub.4).sub.6 Mo.sub.7 O.sub.24.4H.sub.2 O, 
(NH.sub.4).sub.2 MoO.sub.4, 
3(NH.sub.4).sub.2.0.5MoO.sub.3.2MoO.sub.4.6H.sub.2 O, 
[Mo(OCOCH.sub.3).sub.2 ].sub.2, 
Mo(CO).sub.6, 
H.sub.3 PO.sub.4.12MoO.sub.3.xH.sub.2 O, 
(NH.sub.4).sub.3 PO.sub.4.12MoO.sub.3.xH.sub.2 O, 
H.sub.4 SiO.sub.4.12MoO.sub.3.xH.sub.2 O, 
(NH.sub.4).sub.4 SiO.sub.4.12MoO.sub.3.xH.sub.2 O, and 
(NH.sub.4).sub.2 Mo.sub.2 O.sub.7). 
Of these we prefer (NH.sub.4).sub.6 Mo.sub.7 O.sub.24.4H.sub.2 O. 
If desired, for example, to further enhance the catalytic performance of 
the novel catalyst herein, by, for example, increasing activity, altering 
selectivity, or prolonging useful lifetime, we can additionally add in the 
second stage of the process herein any one or combination of metals 
previously defined herein but which have not been previously added to the 
catalyst. Of the additional compounds we prefer to use nickel compounds. 
In our most preferred embodiment, we desire to add both molybdenum and 
nickel to the catalyst in the second stage. 
The addition of the catalytic component in the second stage of the process 
herein can be done in any known or conventional manner, for example, by 
impregnation, mix-mulling or compositing, preferably by impregnation, 
followed by, if desired and/or required, drying and calcining as defined 
above at the end of the first stage. 
The selection of the method of additional component addition, for example, 
of the molybdenum compound and of the nickel compound, for example, nickel 
nitrate or nickel carbonate, is based upon the characteristics of the 
added catalyst material, the nature of the desired additional component 
and the intended process application. For fixed-bed catalysis utilizing 
extrudates or other formed particles, incipient wetness (no excess 
solution) impregnation is the preferred procedure. The solution employed 
is preferably aqueous, and any combination of mutually-soluble components 
can be added to the catalyst by way of the solution prior to the 
additional drying and calcining, if used, as defined in the first stage 
above. 
When the catalyst prepared from the four or more components has not been 
formed into particles, such as extrudates, then other methods of 
additional component blending, in addition to impregnation, can be 
utilized. Such methods include mix-mulling and compositing. These methods 
are used primarily to add insoluble components to a fluid or 
finely-divided catalyst. Mix-mulling implies the use of a liquid to aid in 
the mixing and blending of two or more solid materials. The resulting 
blend can be formed as described above into extrudates, spheres, etc., or 
additional solution can be added to form a pumpable slurry for purposes of 
spray drying. Compositing implies a dry mixing of two or more components. 
The mixture can then be formed into tablets, or a liquid can be added 
thereto to facilitate formation by extrusion spheronization, etc., or a 
slurry can be formed to facilitate spray drying. 
The addition of other components in the second stage can be done in any 
convenient manner, examples of which are set forth below. 
(1) Calcined extrudates can be impregnated with compounds dissolved in 
solution using the well-known incipient wetness (not excess solution) 
method. Compounds can be added in a single step wherein one or more 
compounds are dissolved in solution and simultaneously added to the 
catalyst, followed by drying and calcination. If desired, several steps 
can be employed with intermediate heat treatments. For example: 
(A) A first solution of nickel nitrate hexahydrate can be prepared by 
dissolving the salt in a mixture of water and ammonium hydroxide. A second 
solution can be prepared by dissolving ammonium paramolybdate in a mixture 
of water and ammonium hydroxide. The two solutions can be combined and the 
pH can be adjusted to about 9.6 using additional ammonium hydroxide. This 
solution can then be used to impregnate an extrudate prepared in the first 
stage containing, for example, Al.sub.2 O.sub.3 and TiO.sub.2, followed by 
drying and calcination. The resultant catalyst will contain nickel, 
titanium and molybdenum as oxides and alumina. 
(B) Alternatively, the extrudates of Al.sub.2 O.sub.3 and TiO.sub.2 can be 
impregnated in a two-step process with intermediate heat treatment. In 
such case, this can be done by dissolving ammonium molybdate in a mixture 
of ammonium hydroxide and water and using the resulting solution to 
impregnate the extrudates. After drying, and optionally calcining, the 
impregnated extrudates can be further impregnated using an aqueous 
solution of nickel nitrate hexahydrate, followed by drying and calcination 
to obtain a catalyst containing nickel, titanium and molybdenum as oxides 
and alumina. 
(2) The method of mix-mulling can be used when aggregates, such as 
extrudates, are not formed from the initial mixture. For instance, a 
catalyst resulting from the blending of alumina precursor, titania, and an 
aqueous solution of nitric acid, can be dried, calcined and sized to 
100-200 mesh particles. The catalyst can be dry blended with nickel 
carbonate and molybdenum oxide and sufficient water to form a paste, and 
the resulting combination can be thoroughly mix-mulled, after which the 
catalyst is dried, calcined and sized to 100-200 mesh and then tabletted 
to obtain a catalyst containing nickel, titanium and molybdenum as oxides 
and alumina. 
(3) A composite catalyst can be prepared by blending alumina precursor 
along with water and nitric acid, followed by drying and sizing to 100-200 
mesh. The catalyst was then blended with nickel oxide and molybdenum 
oxide. The powder was tabletted using 1/8-inch dies, then dried and 
calcined to form a catalyst containing nickel, titanium and molybdenum as 
oxides and alumina.

DESCRIPTION OF PREFERRED EMBODIMENTS 
EXAMPLE 1 
226.9 grams of Harshaw alumina, Al 4100P, containing 73.4 weight percent of 
Al.sub.2 O.sub.3, were dry mixed with 18.5 grams of TiO.sub.2, and the 
resulting mixture was further mixed with a solution consisting of 1.8 
grams of 70 weight percent aqueous nitric acid that had been diluted with 
water to a total volume of 167 milliliters. The total amount of water thus 
present was 165 milliliters, and the pH of the aqueous solution prior to 
mixing was 2.1. The components were mixed over a period of two hours to 
obtain a paste. The paste so obtained was then converted to 1/16-inch (1.6 
mm) extrudates which were then dried at 120.degree. C. over a period of 20 
hours and calcined in air at 450.degree. C. over a period of 10 hours. 
A portion of the extrudates so obtained, which contained 78.4 grams of 
Al.sub.2 O.sub.3, was impregnated with a solution prepared as follows: 
15.4 grams of Ni(NO.sub.3).sub.2.6H.sub.2 O, ammonium hydroxide and water 
were combined to form a solution whose total volume amounted to 50 
milliliters and whose pH was 9.5. A separate solution was prepared by 
dissolving 15.0 grams of ammonium para molybdate (containing 82.5 weight 
percent MoO.sub.3), ammonium hydroxide and water, whose total volume 
amounted to 65 ml and whose pH was 9.7. The impregnating solution was 
obtained by combining the two solutions thus formed and adding thereto 
additional amounts of water and ammonium hydroxide to obtain a volume of 
193 ml and a solution having a pH of 9.6. The impregnated extrudates were 
dried at 120.degree. C. over a period of 20 hours and then calcined at 
550.degree. C. over a period of 10 hours. The resultant catalyst was sized 
to 16-30 mesh. The amounts of materials used and conditions employed are 
further set forth below in Table IV. 
EXAMPLE II 
226.9 grams of Harshaw alumina, Al 4100P, containing 73.4 weight percent of 
Al.sub.2 O.sub.3 were thoroughly mixed with a suspension composed of 27.5 
grams of TiO.sub.2 and 851 ml of water. The resultant mixture was dried at 
120.degree. C. for 20 hours and then sized through a 100 mesh screen. The 
material passing through the screen was mixed with a solution consisting 
of 2.7 grams of 70 weight percent aqueous nitric acid that had been 
diluted with water to a total volume of 330 ml. The total amount of water 
thus present was 328 ml and the pH of the aqueous solution prior to mixing 
was 2.2. The components were mixed over a period of two hours to obtain a 
paste. The paste so obtained was then converted to 1/16-inch (1.6 mm) 
extrudates which were then dried at 120.degree. C. over a period of 20 
hours and calcined in air at 700.degree. C. over a period of 10 hours. 
A portion of the extrudates so obtained, which contained 168 grams of 
Al.sub.2 O.sub.3, was impregnated with 205 ml of a solution having a pH of 
9.6 prepared as in Example I using 33.0 grams of 
Ni(NO.sub.3).sub.2.6H.sub.2 O, 32.2 grams of ammonium molybdate 
(containing 82.5 weight percent MoO.sub.3), ammonium hydroxide and water. 
The impregnated extrudates were dried at 120.degree. C. over a period of 
20 hours and then calcined at 550.degree. C. over a period of 10 hours. 
The resultant catalyst was sized to 16-30 mesh. The amounts of materials 
used and conditions employed are further set forth below in Table IV. 
EXAMPLE III 
The procedure of Example I was repeated except that methyl cellulose (an 
extrusion aid) was dry-blended with the alumina and titania. No acidic 
component was added to the water. The amounts of materials used and 
conditions employed are further set forth below in Table IV. 
EXAMPLE IV 
The procedure of Example I was further repeated except that ZrO.sub.2 was 
employed in place of TiO.sub.2. The ZrO.sub.2 was obtained by comingling a 
ZrO(NO.sub.3).sub.2 aqueous solution with a 1:1 volume solution of 
NH.sub.4 OH:H.sub.2 O at a pH of 7, filtering the slurry, washing the 
cake, drying the cake at 120.degree. C. over a period of 20 hours, then 
calcining in air at 500.degree. C. over a period of 10 hours and sizing 
through 80 mesh. The amounts of materials used and conditions employed are 
further set forth below in Table IV. 
EXAMPLE V 
The procedure of Example III was followed, except that ZrO.sub.2 was 
employed in place of TiO.sub.2. The amounts of materials used and 
conditions employed are further set forth below in Table IV. 
Each of the catalysts prepared above contained three weight percent nickel 
metal, five weight percent titanium or zirconium metal, and eight weight 
percent molybdenum metal present as oxides and supported on the Al.sub.2 
O.sub.3. 
Each of the catalysts prepared above was tested for its catalytic activity 
as follows: In each case 102 ml of the catalyst was charged to the 
reactor, after which the reactor was purged with one standard cubic foot 
(0.028 cubic meter)/hour of nitrogen at atmospheric pressure and 
149.degree. C. for 30 minutes. The catalyst was further pretreated with a 
distillate, spiked with 2000 ppm of sulfur as CS.sub.2, which was 
introduced into the reactor at a flow rate of 102 ml per hour and a 
temperature of 149.degree. C. Hydrogen was then introduced at a flow rate 
of 0.358 standard cubic feet (0.01 cubic meter) per hour and 200 psig 
(1379 kPa). The temperature was then raised at the rate of 26.degree. C. 
per hour to 204.degree. C. The pretreatment lasted for a period of 12 
hours. After pretreatment, the distillate flow was stopped and the 
feedstock was begun at 204.degree. C. and a charge rate of 61 ml per hour. 
The hydrogen feed rate was thereupon increased to 1.54 standard cubic feet 
(0.044 cubic meter) per hour and 2000 psig (13,790 kPa). Over a period of 
one hour the temperature was raised to 360.degree. C. and the run was 
begun. The feedstock consisted of Kuwait first-stage HDS product 
containing 1 weight percent sulfur spiked with 1500 ppm sulfur as 
CS.sub.2. Properties of the feedstock are defined below in Table III. 
TABLE III 
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Feedstock Properties 
______________________________________ 
Gravity, .degree.API 
19.9 
Sulfur, Wt % 1.00 
V, ppm 21 
Ni, ppm 10 
Distallation, D 1160 
5% over at .degree.F. (.degree.C.) 
551 (288) 
10% over at .degree.F. (.degree.C.) 
703 (373) 
20% over at .degree.F. (.degree.C.) 
763 (406) 
30% over at .degree.F. (.degree.C.) 
817 (436) 
40% over at .degree.F. (.degree.C.) 
861 (461) 
50% over at .degree.F. (.degree.C.) 
910 (488) 
60% over at .degree.F. (.degree.C.) 
966 (519) 
70% over at .degree.F. (.degree.C.) 
1013 (545) 
80% over at .degree.F. (.degree.C.) 
cracked at 70% 
______________________________________ 
The product was collected every four hours and analyzed for sulfur. The 
activity data obtained, presented below in Table IV, are an average for 
36- and 40-hour periods. Catalyst activity was defined as follows: 
##EQU1## 
wherein S.sub.o and S are the feedstock and product sulfur respectively. 
TABLE IV 
______________________________________ 
Example No. I II III IV V 
______________________________________ 
Initial Treatment 
Al 4100P, g., 
226.9 340.4 408.8 408.8 408.8 
Group IVB Oxide 
TiO.sub.2 
TiO.sub.2 
TiO.sub.2 
ZrO.sub.2 
ZrO.sub.2 
Grams of Group IVB 
18.5 27.5 33.0 26.2 26.2 
oxide 
Nitric Acid, g. 
1.8 2.7 None 3.3 None 
Methyl Cellulose, g. 
None None 3.25 None 3.25 
Water, ml. 165 328 418 442 445 
pH of Aqueous 
2.1 2.2 6.4 2.2 6.4 
Solution 
Subsequent Treatment 
Wt of Al.sub.2 O.sub.3 In 
78.4 168 88.7 90.9 99.3 
Extrudate, g. 
Ni(NO.sub.3).sub.2.6H.sub.2 O, g., 
15.4 33.0 17.4 17.4 19.0 
Ammonium Para 
15.0 32.2 17.2 17.0 18.9 
Molydate, g. 
Vol. of Impregnating 
98 205 114 133 145 
Solution, ml. 
pH of Impregnating 
9.6 9.6 9.6 10.0 10.1 
Solution 
Activity, 62.1 62.6 58.8 59.3 54.7 
% Hydrodesul- 
furization 
______________________________________ 
The unexpected advantages resulting from the process defined and claimed 
herein are apparent from the data in Table IV above. Note that when the 
procedure claimed herein is followed in each of Examples Nos. I and II, 
the activity was 62.1 and 62.6 percent, respectively. When, instead in 
Example No. III an aqueous solution not having a pH below 6 was used, the 
activity of the catalyst was reduced to 58.8 percent. Although Example No. 
IV shows that a catalyst produced herein using ZrO.sub.2 is not as active 
as a similar catalyst using TiO.sub.2 ; nevertheless Example No. V shows 
that when such catalyst is prepared using an aqueous solution not having a 
pH below 6, its activity is much lower, 54.7 percent against 59.3 percent. 
Obviously, many modifications and variations of the invention, as 
hereinabove set forth, can be made without departing from the spirit and 
scope thereof, and therefore only such limitations should be imposed as 
are indicated in the appended claims.