Preparation and use of catalysts comprising a mixture of tungsten oxide and silica supported on a boehmite-like surface

Useful cracking catalysts and catalyst supports comprising a mixture of tungsten oxide and silica supported on a boehmite-like surface which, in turn, is supported on alumina are prepared by forming a composite of particles of (a) tungsten oxide, (b) silica and (c) boehmite and subjecting the composite to steaming at a temperature of at least about 500.degree. C. During the steaming, the tungsten oxide and silica react with the surface of the boehmite as the boehmite converts to alumina.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to the preparation and use of catalysts comprising a 
mixture of tungsten oxide and silica supported on a boehmite-like surface. 
More particularly, this invention relates to the preparation of catalyst 
supports and cracking catalysts comprising mixtures of tungsten oxide and 
silica supported on a boehmite-like surface which are prepared by forming 
a composite of a mixture of (a) tungsten oxide or tungsten oxide 
precursor, (b) particles of silica and (c) particles of boehmite and 
subjecting said composite to high temperature steaming at a temperature of 
at least about 500.degree. C. for a time sufficient for at least a portion 
of said silica and tungsten oxide mixture to react with the surface of the 
boehmite as the bulk boehmite converts to alumina. 
2. Background of the Disclosure 
The use of silica-alumina composites as catalysts and as catalyst support 
materials is well known to those skilled in the art. These catalysts are 
prepared in many different ways such as co-precipitation, various co-gel 
techniques, by contacting alumina with various silica precursor salts such 
as organosilanes, including alkoxy silanes followed by calcination of the 
so-formed composite to produce the desired silica-alumina material. Use of 
the latter techniques enables one to obtain an alumina whose surface is 
partly or completely covered with silica as opposed to a homogeneous or 
heterogeneous silica-alumina composite. 
U.S. Pat. No. 4,440,872 to Grenoble et al discloses various acid cracking 
catalysts. Some of the catalyst supports are prepared by impregnating 
gamma alumina with a silane compound followed by either calcining or 
steaming the impregnate at 500.degree. C. The calcined support material is 
then impregnated with ammonium meta-tungstate which is steamed at high 
temperature to form a catalyst. Peters et al in U.S. Pat. No. 3,671,432 
disclose a process for preparing a supported transition metal of Group V 
or VI of the Periodic Table which includes mixing a water dispersible 
transition metal compound with particles of support material and calcining 
the mixture at a temperature of from 200.degree.-1000.degree. C. However, 
the disclosure contains examples employing only either chromium trioxide 
or vanadium pentoxide as the water dispersible transition metal compounds. 
U.S. Pat. No. 3,668,151 mixes particulate zinc oxide with particulate 
gamma alumina and calcines the mixture at 600.degree.-1500.degree. C. 
Browning et al in U.S. Pat. No. 3,182,012 prepare a cracking catalyst 
comprising cobalt and molybdenum on a silica-alumina support. The silica 
and alumina may be mixed as dry powders, but the cobalt and molybdenum are 
deposited on the support by impregnation. The final impregnate is calcined 
at 600.degree.-1200.degree. F. 
In U.S. Pat. No. 2,830,960 Broomhead mixes cobalt formate, molybdic and an 
alumina hydrogel, followed by drying and calcining the mixture at 
450.degree.-650.degree. C. Porter et al in U.S. Pat. No. 2,640,802 
disclose mixing powdered cobalt oxide, molybdic oxide and alumina, 
pelleting the mixture and heating the pellets for two hours at 530.degree. 
C. U.S. Pat. No. 3,151,091 discloses preparing alumina based catalyst by 
dry mixing alumina with an oxide of a metal selected from the group 
consisting of the iron transition metals, molybdenum, tungsten, vanadium 
and mixtures thereof and calcining the resulting mixture at 
800.degree.-1200.degree. F. 
U.S. Pat. No. 2,394,796 discloses impregnating a porous, hydrated alumina, 
including boehmite, with silicon tetrachloride or tetraethylsilicate, 
followed by hydrolysis of the impregnate to form silica. In U.S. Pat. No. 
2,493,896 an alumina support material is impregnated with ethylsilicate or 
a polymer of ethylsilicate, followed by calcination. Multiple 
impregnations, with calcining after each impregnation, are said to yield a 
catalyst containing up to 50 wt. % silica. In U.S. Pat. No. 4,172,809 a 
process for preparing alumina extrudates is disclosed wherein a silicon 
compound is added to an alumina gel during extrusion of the gel. The 
resulting extrudate is then calcined. U.S. Pat. No. 2,579,123 discloses 
reactivating deactivated silica-alumina catalysts by impregnating with a 
silicon or silicate compound, followed by calcination. 
U.S. Pat. No. 3,502,595 discloses the preparation of silica-alumina 
catalysts by impregnating a hydrated alumina, including boehmite, with one 
or more organic esters of silicon followed by calcination. U.S. Pat. No. 
4,038,337 discloses the preparation of a silica-alumina catalyst by 
reacting gamma or eta alumina with various esters of orthosilicic acid 
followed by calcination. U.S. Pat. No. 4,080,284 discloses contacting a 
support material, such as alumina, with an organic or halogen-substituted 
silane. The silylated support material is then calcined, followed by 
steaming at 900.degree.-1600.degree. F. 
U.S. Pat. No. 4,013,589 discloses a process for improving the mechanical 
and thermal properties (stability) of gamma alumina by impregnating the 
alumina with a hydrolyzable silicone compound and hydrolyzing the 
impregnate to convert the silicone compound to silica. Temperatures of up 
to 500.degree. C. are employed for the hydrolyzing step. In one example, a 
negative comparative example, the alumina was impregnated with a "Ludox" 
slurry (a solution of colloidal silica) followed by calcination in air at 
500.degree. C. 
SUMMARY OF THE INVENTION 
It has now been discovered that useful cracking catalysts and catalyst 
supports comprising mixtures of silica and tungsten oxide supported on a 
boehmite-like surface can be prepared by compositing particles of boehmite 
with particles of silica and tungsten oxide and steaming the composite at 
a temperature of at least about 500.degree. C. for a time sufficient for 
at least a portion of the silica and tungsten oxide to react with the 
surface of the boehmite. In a preferred embodiment of the process of this 
invention the steaming temperature will be at least about 700.degree. C. 
and the silica and tungsten oxide will also spread out, wet and disperse 
over at least a portion of the surface. 
In a preferred embodiment, the boehmite will be porous possessing both 
external and internal surfaces so that the silica and tungsten oxide will 
spread out, wet and disperse over at least a portion of the combined 
external and internal surface of the porous boehmite particles. 
As the composite of boehmite, silica and tungsten oxide is steamed, the 
boehmite converts to .gamma.-Al.sub.2 O.sub.3. At the same time, the 
silica and tungsten oxide react with the surface of the converting 
boehmite thereby stabilizing or freezing the surface of the converting 
boehmite in a transitional or boehmite-like state, while the bulk of the 
boehmite converts to .gamma.-Al.sub.2 O.sub.3. This transitional state is 
herein defined as a boehmite-like surface phase which has an amorphous, 
disordered sstructure which is different from both boehmite and 
.gamma.-Al.sub.2 O.sub.3. Thus, the compositions produced by the process 
of this invention comprise silica and tungsten oxide supported on a 
boehmite-like surface which, in turn, is supported on bulk alumina. 
These compositions are different from similar types of compositions (a) 
formed by compositing particles of silica and tungsten oxide with 
particles of alumina and steaming the composite at high temperatures and 
(b) calcining the composite of silica, tungsten oxide and boehmite. 
DETAILED DESCRIPTION 
Those skilled in the art know that boehmite is a highly hydroxylated form 
of alumina that can be represented by the simple formula A100H. Boehmites 
also have relatively high surface areas. Commercially available boehmites 
generally have surface areas of about 300-500 M.sup.2 /g (BET). These 
materials are generally relatively porous and, consequently, their 
measured surface areas include both the exterior surface and the internal 
pore surface. When boehmite is steamed at temperatures in excess of about 
500.degree. C., it undergoes a phase change first to pseudo-boehmite and 
then to .gamma.-Al.sub.2 O.sub.3, which also results in a dramatic 
reduction of the surface area of from about 300-500 M.sup.2 /g to about 
200-300 M.sup.2 /g. If the steaming temperature is greater than about 
800.degree. C., the formation of .theta.-Al.sub.2 O.sub.3 or a mixture of 
.theta.-Al.sub.2 O.sub.3 and .gamma.-Al.sub.2 O.sub.3 occurs with a 
concomitant surface area reduction to from about 1-100 M.sup.2 /g. In 
marked contrast, in the process of this invention the surface area of the 
final, silica and tungsten oxidecontaining composition will generally 
range from about 180-220 M.sup.2 /g when the surface area of the boehmite 
is about 300-500 M.sup.2 /g. In the process and compositions of this 
invention, boehmite refers to the bulk structure and is meant to include 
pseudo-boehmite and mixtures of boehmite with pseudo-boehmite. 
In the process of this invention, the silica and tungsten oxide react with 
the surface of the boehmite as it is undergoing phase transition, thereby 
"freezing" or stabilizing the changing surface in the form of 
boehmite-like transitional phase reacted with the silica and tungsten 
oxide which have an amorphous, disordered structure unlike either 
boehmite, pseudo-boehmite or alumina. Consequently, even though the bulk 
boehmite converts to alumina during the high temperature steaming 
treatment, the surface of the so-formed alumina or, more precisely, those 
portions of the surface of the so-formed alumina underlying and supporting 
the reacted tungsten oxide and silica, will be a boehmite-like phase 
stabilized by the reaction of the silica and tungsten oxide with the 
surface of the transforming boehmite. It is the formation of this tungsten 
oxide and silica-stabilized boehmite-like phase that prevents the boehmite 
from desurfacing down to about 100 or even M.sup.2 /g in the presence of 
high temperature steam, which will occur if the mixture of silica and 
tungsten oxide are not present on the boehmite surface. As will be shown 
in the Examples below, the compositions of this inventions are different 
from compositions formed (a) by high temperature steaming a composite of 
particles of .gamma.-Al.sub.2 O.sub.3, silica and tungsten oxide or (b) 
calcining composites of silica, tungsten oxide and boehmite. 
Thus, in the process of this invention, the high temperature steaming 
treatment causes the tungsten oxide and silica to react with the surface 
of the boehmite. While not wishing to be held to any particular theory, 
those skilled in the art know that boehmite is a particular form of 
hydrated alumina which loses water of hydration at elevated temperatures. 
Boehmite has a relatively large amount of surface hydroxyl groups. It is 
believed that these surface hydroxyls on the boehmite react with the 
tungsten oxide and silica with the formation of oxygen-silicon bonds and 
oxygen-tungsten bonds. Thus, during the process of this invention, the 
silica and tungsten oxide react with the surface of the transforming 
boehmite to form a surface phase complex. This surface phase complex is 
non-crystalline in form and exhibits properties substantially different 
from either bulk silica, bulk tungsten oxide, bulk boehmite or the bulk 
alumina formed from high temperature steaming of the boehmite. 
The amount of steam employed in forming the compositions of this invention 
may vary over a wide range, i.e., from less than about 1% to more than 90% 
of the non-reducing, steaming environment. Compositions of this invention 
have been made employing as little as 3% steam to as much as 90% steam. In 
general, the more steam that is employed the faster will be the reaction 
of the silica and tungsten oxide with the alumina boehmite. 
In general, the loading levels of the silica and tungsten may be such that 
the combined amount of silica and tungsten oxide will range from about 
1-50 wt. % of the total composition, with the WO.sub.3 loading range from 
about 1-25 wt. % of the total composition and the silica loading ranging 
from about 1-50 wt. % of the total composition. Preferably the amount of 
WO.sub.3 or silica will be present in an amount of from about 1 to 20 wt. 
% of the total composition, more preferably from about 2-10 wt. % and most 
preferably from about 2-6 wt. %. 
As previously stated, boehmites are generally porous materials. That is, 
there are a multitude of pores and channels from the exterior of a 
discrete, macroscopic particle to the interior of the particle. 
Consequently, the surface of a boehmite particle includes all the pores 
and channels of said boehmite and their surface area as measured by 
nitrogen gas adsorption according to BET theory. There is much more 
surface in the interior of such a discrete, macroscopic particle of 
boehmite than on its exterior surface. In many cases, the external surface 
is less than 2% of the total surface area. In this application, "surface" 
is used in such an art-recognized fashion and, unless expressly stated 
otherwise, is not to be restricted to the physical exterior surface of 
macroscopic particles of boehmite. 
It is to be noted that the process of this invention of dispersing the 
silica and tungsten oxide onto the surface of boehmite by the high 
temperature steam treatment in a non-reducing atmosphere will not work 
with oxides or oxide salt precursors of, for example, titanium, zirconium, 
hafnium, vanadium, niobium, tantalum and chromium. That is, none of these 
oxides will disperse onto the surface of boehmite via the high temperature 
steam treatment process of this invention. 
In the process of this invention, the silica source may be hydrated silica 
in the form of an aqueous slurry of colloidal silica or very fine 
particles of silicic acid which is also a form of hydrated silica. 
Alternatively, if convenient, the silica source may also be in the form of 
an insoluble silica precursor material such as silicon tetraacetate, 
silicon oxylate, etc. By insoluble silica precursor material is meant a 
silicon compound which is insoluble both in water and polar and non-polar 
solvents ranging from acetone, ethanol, or methanol, ketones, aldehydes, 
cyclic ketones, hydrocarbons, etc. The important requirement is that the 
precursor material be one which when subjected to the steaming treatment 
in the non-reducing atmosphere fairly readily converts to silica under the 
conditions of the steaming treatment. 
In one embodiment, the tungsten oxide source may be solid particles of 
tungsten oxide, particles of tungstic acid which is a form of hydrated 
tungsten oxide or mixture thereof. In another embodiment, the tungsten 
oxide source may be in the form of a more conventional tungsten oxide 
source such as a tungsten oxide precursor salt illustrated by, for 
example, ammonium meta tungstate, a solution of which can be impregnated 
onto the boehmite, before, after or simultaneously with the silica or 
silica precursor in which case the high temperature steaming rapidly 
converts the tungsten oxide precursor to tungsten oxide. In yet another 
embodiment, the tungsten oxide source can be a mixture of both of the 
foregoing, the choice being left to the convenience of the practitioner.

The invention will be more readily understood by reference to the examples 
below. 
EXAMPLES 
Experimental Section 
Introduction 
The preparation of acid catalysts was investigated where the alumina 
support was boehmite (A100H) and where the precursor salt (or salts) can 
be insoluble in an aqueous phase. During the activation of the sample by 
treatment in steam at high temperature to produce an acidic catalyst, the 
boehmite phase converted to .gamma.-Al.sub.2 O.sub.3, or .theta.-Al.sub.2 
O.sub.3, and the precursor salt, or salts, dispersed on the alumina 
surface to introduce strong acid sites. In the process of steaming these 
materials, high cracking activity and high surface area are introduced in 
the final catalyst composition. The unexpected activity and high surface 
area of these catalysts is a result of starting with a boehmite alumina 
and dispersing the active catalyst components. 
EXAMPLE 1 
The preparation of 6% WO.sub.3 on .gamma.-Al.sub.2 O.sub.3 was carried out 
by ball-milling 3.24 g of H.sub.2 WO.sub.4 (Alfa Inorganic) with 58.75 g 
of A100H (Davison Chemical Company) for 15 minutes. The same was steamed 
at 870.degree. C. in 90% H.sub.2 O-10% N.sub.2 for 16 hrs. in a vertical 
tube furnace. The catalytic cracking activity of samples of the instant 
invention were performed on a modified Micro Activity Test (MAT) unit 
described in the Experimental Section. The MAT activity of this steamed 
catalyst was 27 with a conversion to 400.degree. F. liquids of 9.2 wt. % 
based on feed. The BET surface area of this steamed sample was measured to 
be 87 m.sup.2 /g (measured using a Digisorb 2500 as were all the BET 
surface areas reported in the instant invention). This sample demonstrates 
that active cracking catalysts can be prepared by physical mixture of an 
insoluble tungsten precursor and a boehmitic alumina followed by steam 
treatment. 
A 6% WO.sub.3 and 6% SiO.sub.2 on .gamma.-Al.sub.2 O.sub.3 sample was 
prepared for comparison to the 6% WO.sub.3 on .gamma.-Al.sub.2 O.sub.3 
sample of this example. For this preparation, 2.95 g of ammonium 
meta-tungstate was added to 6.8 g of "Ludox" AS-40 (a colloidal SiO.sub.2, 
tradename DuPont) in 60 ml of H.sub.2 O. This solution mixture was added 
to 50 g of A100H (Davidson Chemical Company) by the pore filling method. 
The sample was dried at 120.degree. C. for 16 hrs. and then steamed at 
870.degree. C. for 16 hrs. as described previously in this example. The 
MAT activity of this sample was 42 with a conversion to 400.degree. F. 
liquids of 17.2 wt. % based on feed. This sample of 6% WO.sub.3 and 6% 
SiO.sub.2 on .gamma.-Al.sub.2 O.sub.3 is clearly superior to the 6% 
WO.sub.3 on .gamma.-Al.sub.2 O.sub.3 sample described in this example. In 
addition, the BET surface area of this 6% WO.sub.3 -6% SiO.sub.2 on 
.gamma.-Al.sub.2 O.sub.3 catalyst was measured to be 174 m.sup.2 /g. This 
sample surface area is twice that of the 6% WO.sub.3 on .gamma.-Al.sub.2 
O.sub.3 sample of this example. This 6% WO.sub.3 -6% SiO.sub.2 on 
.gamma.-Al.sub.2 O.sub.3 sample with high surface area and high cracking 
activity is an ideal catalyst for heavy ends conversion processes, such as 
residuum cracking and residuum hydroconversion. The results of this 
example will be useful for comparison to other examples of the instant 
invention. 
EXAMPLE 2 
In this example, two WO.sub.3 on Al.sub.2 O.sub.3 catalysts were prepared 
using A100H by use of two different preparation techniques. One 12% 
WO.sub.3 on .gamma.-Al.sub.2 O.sub.3 catalyst was prepared using H.sub.2 
WO.sub.4 as described in Example 1. The other sample was prepared using 
ammonium meta-tungstate dissolved in water using the pore filling method 
of catalyst preparation. This sample was dried at 110.degree. C. for 16 
hrs. Both samples were steam treated at 870.degree. C. for 16 hrs. as 
described in Example 1. The MAT activity and conversion to 400 .degree.F. 
liquid products of both these samples were identical: 44 and 16.4 wt. % 
based on feed. In addition, both samples had the same BET surface area of 
86 m.sup.2 /g. It should be noted that the 6% WO.sub.3 -6% SiO.sub.2 on 
.gamma.-Al.sub.2 O.sub.3 sample of Example 1 has a conversion to liquid 
products superior to the above 12 wt. % WO.sub.3 on .gamma.-Al.sub.2 
O.sub.3 catalysts while having only half the tungsten content. As tungsten 
oxide is an expensive component of the catalysts of the instant invention, 
the mixed WO.sub.3 -SiO.sub.2 on Al.sub.2 O.sub.3 catalyst of Example 1 
shows that the tungsten concentration can be decreased dramatically while 
maintaining high activity and high selectivity to desired products. 
Further, this example demonstrates that active cracking catalysts can be 
prepared using an aqueous solution soluble precursor (ammonium 
meta-tungstate) or an insoluble precursor (tungstic acid). 
EXAMPLE 3 
The preparation of 7.4 wt. % WO.sub.3 on .gamma.-Al.sub.2 O.sub.3 was 
carried out using A100H (Cyanamid, Reforming Grade) as described in 
Example 2 using H.sub.2 WO.sub.4. The sample was steamed at 870.degree. C. 
for 1 hr. as described in Example 1. The MAT activity of this steam 
catalyst was 51 with a conversion to 400.degree. F. liquids of 19.2 wt. % 
based on feed. The BET surface area of this steamed sample was measured to 
be 114 m.sup.2 /g. This sample shows superior activity and liquid yield 
compared to the samples of Example 1 with 6% WO.sub.3 contents. 
A 7.3 wt. % WO.sub.3 /7.3 wt. % SiO.sub.2 on .gamma.-Al.sub.2 O.sub.3 
sample was carried out using Cyanamid A100H. This sample was prepared as 
described in Example 1. Two portions of this sample were activated by 
steam treatment as described in Example 1: one for 1 hr. and the other for 
16 hrs. The sample steamed for 1 hr. had a MAT activity of 52 with a 
conversion of 400.degree. F. liquids of 17.8 wt. % based on feed. The BET 
surface area of this sample was measured to be 188 m.sup.2 /g. As shown in 
Example 1, incorporation of silica along with tungsten oxide on Al.sub.2 
O.sub.3 of the catalysts of the instant invention leads to a higher 
surface area than obtained for tungsten oxide alone on Al.sub.2 O.sub.3. 
The 7.3 WO.sub.3 -7.3% SiO.sub.2 on Al.sub.2 O.sub.3 sample steamed for 16 
hrs. had a MAT activity of 46 with a conversion to 400.degree. F. liquids 
of 16.0 wt. % based on feed. The BET surface area of this sample was 
measured to be 182 m.sup.2 /g. This sample demonstrates that active and 
steam stable, catalysts can be prepared where mixed WO.sub.3 -SiO.sub.2 on 
.gamma.-Al.sub.2 O.sub.3 catalysts are prepared using A100H as the alumina 
precursor support. 
EXAMPLE 4 
In this example a 12 wt. % SiO.sub.2 on Al.sub.2 O.sub.3 sample will be 
compared to a 7 wt. % WO.sub.3 -12 wt. % SiO.sub.2 sample. The 12 wt. % 
SiO.sub.2 sample was prepared using "Ludox" AS-40 as described in Example 
1. To 27 g of A100H (Cyanamid, Reforming Grade) was added 7.5 g of Ludox 
in 18 ml total solution volume. This sample was steamed at 870.degree. C. 
for 1 hr. as described in Example 1. The MAT activity of this steamed 
catalyst was 28 with a conversion to 400.degree. F. liquids of 9.5 wt. % 
based on feed. The 7 wt. % WO.sub.3 -12 wt. % SiO.sub.2 sample was 
prepared as described in Example 1 using ammonium meta-tungstate and 
"Ludox" AS-40. To 42 g of A100H (Cyanamid, reforming grade) was added 3.24 
g of ammonium metatungstate and 12.5 g of "Ludox" in 28 ml total solution 
volume. This sample was steamed at 870.degree. C. for 1 hr. as described 
in Example 1. The MAT activity of this steamed catalyst was 50 with a 
conversion to 400.degree. F. liquids of 18.2 wt. % based on feed. This 
example demonstrates the superior catalytic activity and selectivity of 
WO.sub.3 -SiO.sub.2 on Al.sub.2 O.sub.3 catalyst of the instant invention 
compared to SiO.sub.2 on Al.sub.2 O.sub.3. The BET surface area of these 
two samples were quite similar: 201 and 214 for 7% WO.sub.3 -12% SiO.sub.2 
on Al.sub.2 O.sub.3 and 12% SiO.sub.2 on Al.sub.2 O.sub.3, respectively. 
Although this 12% SiO.sub.2 sample retained higher surface area than the 
7.4 wt. % WO.sub.3 on Al.sub.2 O.sub.3 of Example 3, the catalytic 
performance was inferior to the 7% WO.sub.3 content samples of Example 3. 
EXAMPLE 5 
A sample of 6 wt. % WO.sub.3 and 6 wt. % Sio.sub.2 on .gamma.-Al.sub.2 
O.sub.3 was prepared using .gamma.-Al.sub.2 O.sub.3 for comparison to the 
catalysts prepared on A100H of the instant invention. To 44 g of 
.gamma.-Al.sub.2 O.sub.3 (Engelhard Industries, reforming. grade) was 
added 7.5 g of "Ludox" AS-40 and 3.24 g of ammonium meta-tungstate in 26 
ml of H.sub.2 O. This solution mixture was added to the alumina by the 
pore filling method. The sample was dried at 120.degree. C. for 16 hrs. 
and then steamed at 870.degree. C. for 16 hrs. as described in Example 1. 
The MAT activity of this sample was 45 with a conversion to 400.degree. F. 
liquids of 15.4 wt. % based on feed. The conversion to liquid products of 
this sample is inferior to the 6% WO.sub.3 -6% SiO.sub.2 on 
.gamma.-Al.sub.2 O.sub.3 of Example 1. 
The BET surface area of the 6% WO.sub.3 -6% SiO.sub.2 on .gamma.-Al.sub.2 
O.sub.3 sample of this example was measured to be 131 m.sup.2 /g. 
Therefore, the 6% WO.sub.3 -6% SiO.sub.2 on .gamma.-Al.sub.2 O.sub.3 
sample of Example 1, made using A100H as the alumina precursor, has a 58% 
higher surface area than the 6% WO.sub.3 -6% SiO.sub.2 on .gamma.-Al.sub.2 
O.sub.3 sample prepared using .gamma.-Al.sub.2 O.sub.3. The superior 
selectivity to liquid products and the higher surface area for catalysts 
prepared employing A100H rather than using .gamma.-Al.sub.2 O.sub.3 is 
demonstrated by this example. Catalysts of the instant invention should be 
particularly suited for application in heavy ends conversion processes, 
such as residuum cracking and residuum hydroconversion.