Silica-modified aluminophosphate compositions, catalysts, method of preparing same and polymerization processes

An amorphous aluminophosphate composition is provided which exhibits a microstructure of sheets and spheres of silica-modified aluminophosphate. Also provided is a method for preparing the composition comprising mixing an aqueous solution containing aluminum ions, phosphate ions and silica ions, with a neutralizing solution, wherein the mixing is conducted with sufficient shear to produce on a microlevel, sheets of silica-modified aluminophosphate and spheres of silica-modified aluminophosphate. A polymerization catalyst and a polymerization process are also provided.

FIELD OF THE INVENTION 
This invention relates to silica-modified aluminophosphate compositions, 
catalysts and polymerization processes. 
BACKGROUND OF THE INVENTION 
Various aluminophosphate compositions are known in the art. These 
compositions can exhibit widely different physical properties such as 
surface area, pore size and pore size distribution. The terms 
aluminophosphate compositions, supports and precipitates are used 
interchangeably herein. 
Many aluminophosphate compositions lack a combination of physical 
properties which characterize superior polymerization catalyst supports. 
For example, some aluminophosphate compositions exhibit low surface area 
and poor heat stability. Other supports with a high macropore volume do 
not exhibit good physical stability. 
Other supports lack sufficient activity to be suitable catalysts. Previous 
methods employed a cocatalyst to boost activity; however, the presence of 
the cocatalyst increases the amount of undesirable low molecular weight 
portion in the polymer product. This low molecular weight material causes 
problems, such as smoking, during subsequent processing. 
Other catalysts are not effective at incorporating comonomer during 
polymerization. Still other catalysts produce a polymer having a 
relatively broad molecular weight distribution, while some applications 
require a narrow molecular weight distribution. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a silica-modified 
aluminophosphate composition with excellent thermal stability. 
It is another object of the present invention to provide a silica-modified 
aluminophosphate composition with excellent physical stability. 
It is another object of the present invention to provide a silica-modified 
aluminophosphate composition with a relatively high amount of 
macroporosity. 
It is another object of the present invention to provide a silica-modified 
aluminophosphate composition with a relatively high fragmentation 
potential. 
It is another object of the present invention to provide a silica-modified 
aluminophosphate composition having a relatively large amount of 
macropores and sufficient physical strength that the composition does not 
fragment too easily. 
It is another object of the present invention to provide a catalyst useful 
in reactions involving relatively large molecules. 
It is another object of the present invention to provide catalysts which 
are effective in various types of polymerization processes. 
It is another object of the present invention to provide catalysts which 
are sufficiently active that a cocatalyst is not necessary in a gas phase 
polymerization processes. 
It is another object of the present invention to provide catalysts which 
produce polymer having a relatively low amount of low molecular weight 
component. 
It is another object of the present invention to provide a polymerization 
catalyst with relatively high activity. 
It is another object of the present invention to provide a polymerization 
catalyst which produces relatively high comonomer incorporation. 
It is another object of the present invention to provide a polymerization 
catalyst which produces a polymer having a relatively narrow molecular 
weight distribution. 
It is another object of the present invention to provide a polymerization 
process which produces a polymer which does not produce smoking during 
processing. 
In accordance with the present invention an amorphous aluminophosphate 
composition is provided which exhibits a microstructure of sheets and 
spheres of silica-modified aluminophosphate. Also provided is a method for 
preparing the composition comprising mixing an aqueous solution containing 
aluminum ions, phosphate ions and silica ions with a neutralizing 
solution, wherein the mixing is conducted with sufficient shear to 
produce, on a microlevel, sheets of silica-modified aluminophosphate and 
spheres of silica-modified aluminophosphate. A catalyst and polymerization 
process are also provided. 
DETAILED DESCRIPTION OF THE INVENTION 
This application is a continuation-in-part of U.S. Ser. Nos. 08/741,595 and 
08/742,794 both filed Oct. 31, 1996, the disclosures of which are 
incorporated herein by reference. 
The inventive silica-modified aluminophosphate compositions, having the 
empirical formula Al.sub.2 O.sub.3.xAlPO.sub.4.ySiO.sub.2, exhibit a 
microstructure of sheets and spheres of silica-modified aluminophosphate. 
The inventive aluminophosphate compositions have excellent thermal and 
physical stability together with a relatively high amount of 
macroporosity. These materials are particularly suited for use as catalyst 
support materials, especially for use in reactions involving relatively 
large molecules. 
The silica-modified aluminophosphate compositions are prepared by the 
method comprising mixing an aqueous solution containing aluminum ions, 
phosphorous ions and silica ions with a neutralizing solution, wherein the 
mixing is conducted with sufficient shear to result in the formation of 
sheets and spheres on a microlevel. 
As used herein, shear means shear rate which is a change in velocity 
(.DELTA.V) divided by a change in distance (.DELTA.d). The shear rate can 
be increased by increasing .DELTA.V or decreasing .DELTA.d. 
The aqueous solution is generally an acidic medium containing aluminum 
cations and phosphate anions. Suitable sources of aluminum ions include 
inorganic aluminum salts. The aluminum salt can be any aluminum salt which 
is soluble in water such as aluminum nitrate, aluminum chloride, aluminum 
sulfate, pseudo-boehmite, aluminum hydroxide, or aluminum alkoxide. 
Typically, the source of phosphorous ions is phosphoric acid. 
The concentration of aluminum salt can vary broadly. Generally, the 
concentration of aluminum salt will be in the range of from about 12 to 
about 80 weight percent of the aqueous solution prior to neutralization, 
preferably from about 30 to about 70 weight percent, and more preferably 
from 60 to 70 weight percent. The use of the lower concentration of 
aluminum salts results in the formation of harder aluminophosphate 
precipitates. 
The phosphorous ions are present in an amount such that the phosphorous to 
aluminum mole ratio is similar to the phosphorous to aluminum mole ratio 
desired in the final product. The mole ratio of phosphorous to aluminum in 
the aqueous solution is generally about 0.01 to about 2, preferably about 
0.1 to about 1. The phosphorus to aluminum mole ratio for the 
aluminophosphate product is about 0.01 to about 2, preferably in the range 
of from 0.1 to about 1, more preferably from 0.2 to 0.8, and most 
preferably from 0.4 to 0.6. 
Suitable sources of silicate ions include inorganic silicate salt and 
aqueous silica gels which are soluble in water. The silicate salt can be 
any silica salt such as alkali metal silicates. Excellent results have 
been obtained with sodium silicate and it is preferred. 
The concentration of silicate salt can vary broadly in the aqueous solution 
prior to neutralization. Generally, the concentration of silicate salt 
will be varied to yield silica in the product with the empirical formula 
Al.sub.2 O.sub.3.xAlPO.sub.4.ySiO.sub.2, where y, the mole ratio of 
silica, is 3 or less, preferably 2 or less and most preferably 1 or less. 
Or, expressed another way, the mole ratio of phosphorus to silicon is from 
about 20 to about 0.05. In a preferred embodiment, the mole ratio of 
phosphorus to silicon is from about 10 to about 0.05. In a more preferred 
embodiment, the mole ratio of phosphorus to silicon is from about 4 to 
about 2. 
Generally, the neutralizing material is a base such as an aqueous solution 
of ammonia such as ammonium hydroxide, ammonium carbonate, ammonium 
bicarbonate or urea. It is preferred that the concentration of the salts 
and the base be high, so that on mixing of the two streams, a precipitate 
is immediately formed. 
The neutralization is controlled so the pH of the neutralized reaction 
mixture is in the range of from about 4 to about 11, preferably from about 
6 to about 11, and more preferably from 7 to 10. 
The neutralization is conducted by adding controlled amounts of (i) the 
aqueous solution containing aluminum, phosphate and silica ions and (ii) 
the neutralizing medium to a high shear mixer/reactor in a continuous 
manner. The neutralization reaction is substantially instantaneous and is 
exothermic. 
Alternatively, the aqueous solution can be a basic solution of salts such 
as a mixture of sodium aluminate and sodium phosphate which is neutralized 
with an acid solution such as HCl. The concentration of salts and the 
neutralization is conducted as disclosed above. 
Preferably, the composition is prepared by the method comprising the 
continuous addition of the aqueous solution and neutralizing medium to a 
high shear mixer/reactor, and the continuous removal of the 
silica-modified aluminophosphate precipitate as it is formed. The 
silica-modified aluminophosphate precipitate can be quenched and/or 
cooling means can be used to lower the reactor temperature. Generally, the 
temperature in the reactor is in the range of from about 20.degree. C. to 
about 90.degree. C. 
The key element in the preparation of the silica-modified aluminophosphate 
compositions is mixing the reactants with sufficient shear force to 
produce the formation of a silica-modified aluminophosphate composition 
containing sheets of silica-modified aluminophosphate as well as spheres 
of silica-modified aluminophosphatein the microstructure of the 
composition. 
Various types of mixing techniques and apparatus are suitable for 
generating varying levels of shear delivery mixing. See, for example, 
"Scaleup and Design of Industrial Mixing Processes" by Gary B. Tatterson, 
McGraw-Hill, Inc., (1994), the disclosure of which is hereby incorporated 
by reference. Figure 2.9 illustrates the shear level of various types of 
mixers and impellers. Colloid mills, saw blade-type impellers; 
homogenizers and rotor stator mixers provide the highest level of shear 
while the hydrofoil and propeller provide the lowest shear. The newer jet 
stream mixers can also be employed with sufficient shear as taught herein. 
One suitable mixer is a rotor stator mixer where the fluids to be mixed 
usually are pumped in the rotor stator chamber through concentric tubes. 
The rotor stator chamber consists of a rotor revolving at some desired 
rate and a "stator" or surrounding wall close to the tips of the revolving 
rotor. The wall is provided with openings to permit the mixed fluids to be 
removed or withdrawn quickly and continuously from the rotor-stator 
chamber. 
Using the rotor stator mixer as an example, the velocity of the fluid is 
highest at the tip of the rotor impeller and is zero at the wall. Thus, 
the .DELTA.V is taken as the velocity at the tip which can be calculated 
by multiplying the revolutions of the rotor per second times the radius of 
the rotor thus: 
EQU .DELTA.V=ND/2 
where N is the number of revolutions of the rotor per second and D is the 
diameter of the rotor. 
The change in distance, .DELTA.d, is the distance over which the change in 
velocity is measured, for example, the distance between the tip of the 
impeller and the wall in a rotor sator. Shear rates have the units of 
reciprocal time. 
The apparent average shear rate is defined as the change in velocity over 
the change in distance and is calculated by the equation: 
##EQU1## 
N is the number of revolutions of the impeller per second, W is the 
distance between the tip of the impeller and the wall of the mixer, and D 
is the diameter of the rotor in the case of rotor-sator mixers, or can be 
the thickness of the impeller blade for other mixers. 
The shape of the impeller and the design of the stator have an effect on 
the amount of shear developed. The stator, for example, can be a 
cylindrical wall provided with slots or can be a cylindrical screen. 
The reactants are fed into the reactor/mixer and the aluminophosphate 
precipitate removed as it is formed. As noted above, it is preferred to 
use relatively concentrated solutions of aluminum and phosphorous so that 
on neutralization a precipitate is formed immediately. The neutralization 
reaction occurs rapidly and aluminophosphate precipitate is removed in 
times of from 0.5 to 5 seconds. Typically, the reaction and mixing occurs 
in less than 1 second. 
It has been found that the apparent average shear rate should be at least 
0.5.times.10.sup.4 reciprocal seconds to result in the formation of sheets 
of aluminophosphate on the microlevel, preferably in the range of from 
1.times.10.sup.4 to 10.times.10.sup.4 reciprocal seconds. 
The aluminophosphate product can be quenched if desired and then washed to 
reduce the concentration of residual salts. Removal of residual salt is 
generally desired because such salts can act as poisons to catalytic metal 
deposited on the support. However, some residual salt level can help 
maintain the stability of the aluminophosphate structure and preserve the 
sheets of aluminophosphate in the microstructure. 
Typically, the initial conductivity of the water wash is from 30,000 mmohs 
to 100,000 mmohs. Washing is conducted to reduce the conductivity from the 
initial value to some lower value, but greater than about 500 mmohs, 
typically from about 2,000 mmohs to about 4,000 mmohs. 
Employing a quench procedure to reduce the temperature of the 
aluminophosphate precipitate will affect the size of the pores in the 
final product. Quenching to a temperature of from 18.degree. C. to 
30.degree. C. tends to make an aluminophosphate composition having a 
narrower distribution of pores whereas non-quenching of the product tends 
to broaden the pore size distribution in the product. The distribution of 
pore size and pore volume can be affected by the use or non-use of a 
quench and whether washing is done with either hot water or cold water. 
The use of hot washing and hot aging tends to shift the aluminophosphate 
composition to a larger pore volume and a larger macropore volume. By hot 
washing is meant that the aluminophosphate composition is washed with 
water which has been heated to a temperature of 45.degree. C. to 
80.degree. C. By hot aging is meant that the product simply sits in a hold 
vessel for 1 to 4 hours at a temperature from 45.degree. C. to 80.degree. 
C. 
The preferred technique of washing and filtration is by the use of a 
vibrating filtration membrane. When a vibrating filtration membrane is 
employed, the aluminophosphate is not compacted as a cake so that washing 
and filtration occur much more quickly than with non-vibrating techniques. 
After the water has been reduced to the desired conductivity level, the 
water washing is stopped and the hydrogel is concentrated to a level of 12 
percent to 22 percent solids, depending on which type of subsequent drying 
is employed. The temperature of drying is usually from 100.degree. C. to 
130.degree. C. for times varying from 6 to 30 hours. Spray drying is very 
rapid and results in the formation of small-particle size beads which are 
suitable for use in fluid bed type operations. 
After drying, the precipitates or the beads are generally calcined in the 
presence of air or oxygen. Usually, the heating is done at a temperature 
from about 300.degree. C. to about 800.degree. C. for a time of up to 16 
hours, usually for a time of from 2 hours to 16 hours. 
The silica-modified aluminophosphate precipitates prepared as described 
above are amorphous and contain, in their microstructure, sheets of 
silica-modified aluminophosphate as well as spheres of silica-modified 
aluminophosphate. 
Typically, the surface area of the silica-modified aluminophosphate 
composition is in the range of from about 90 to about 300 m.sup.2 /gram, 
preferably from 90 to 250 m.sup.2 /gram as determined according to the BET 
(Brunauer, Emmett, and Teller) method. Surface area is calculated using 
the BET equations as described in the Journal of the American Chemical 
Society 60, 309 (1938). The equations are used in conjunction with 
corrections proposed by Voet in Rubber World 139, 63, 232 (1958). 
Under the BET method, a sample is degassed by heating and evacuating to 
300.degree. C. and a pressure not to exceed 10.sup.-3 Torr to remove 
adsorbed vapors from the surface. The sample is then evacuated and cooled 
to the boiling point of liquid nitrogen (77.3 K). The nitrogen adsorption 
isotherm is determined by subsequently adding known amounts of nitrogen 
gas to the sample at various low level pressures until the saturation 
pressure of nitrogen is reached. Each next dose of nitrogen is introduced 
to the sample only after the foregoing dose has reached equilibrium. The 
desorption isotherm is determined by measuring the incremental volume of 
nitrogen desorbed from the saturated sample for each successive small 
decrements in the ambient pressure. The pore size distribution is 
determined by analyzing the desorption data of the nitrogen isotherm. 
Computations are predicted from the Kelvin equation. 
The macropore volume is defined as the volume occupied by pore sizes 
greater than 1000 .ANG.. A relatively high macropore volume is 
particularly desirable for some end uses, such as the polymerization of 
olefins. 
Generally, the macropore volume is greater than about 0.01 cc per gram, 
preferably the volume is about 0.1 cc per gram or greater, and more 
preferably from about 0.1 cc per gram to about 0.8 cc per gram, and most 
preferably from 0.1 cc per gram to 0.6 cc per gram as determined by the 
mercury porosimetry test according to ASTM D4284-88 where gamma is 473 
dynes per cm and the contact angle is 140 degrees. 
Spray drying followed by calcining at 450.degree. C. for 8 hours typically 
yields aluminophosphate compositions with macropore volumes from about 0.1 
cc per gram to about 0.6 cc per gram. Relatively higher macropore volume 
materials can be prepared by directly calcining the undried 
aluminophosphate filter cake in a muffle furnace. 
The mesopore volume is defined as the volume occupied by pore sizes from 20 
.ANG. to 1000 .ANG.. There are substantially no micropores (less that 20 
.ANG.). 
The mesopore volume is generally 0.1 cc per gram or greater, preferably 
from about 0.2 cc per gram to about 1 cc per gram, more preferably from 
about 0.3 cc per gram to about 0.8 cc per gram, and most preferably from 
0.5 cc per gram to 0.7 cc per gram as determined by the BET method. 
The mean mesopore diameter of the new silica-modified aluminophosphate 
compositions is generally in the range of from 50 .ANG. to 450 .ANG., 
preferably in the range of from 150 .ANG. to 400 .ANG., and more 
preferably in the range of from 150 .ANG. to 300 .ANG.. 
Polymerization catalysts are subject to attrition during activation and 
polymerization. Traditional techniques such as air jet testing can provide 
an effective model for attrition occurring during activation; however, 
such techniques do not provide an effective model for attrition occurring 
during polymerization. 
The fragmentation potential and sonication number, as determined by 
sonication, can be used in determining the expected efficiency of a 
catalyst in a process where fragmentation will occur. It is believed that 
the sonication process closely resembles the fracturing process which can 
occur during polymerization. The catalyst particles break up due to the 
accumulation of polymer and pressure within the pore structure. 
The "fragmentation potential", as used herein, is the percent increase in 
the percentage of particles which are smaller than 40 microns after 
sonication for 30 minutes in an aqueous medium plus a dispersant using an 
Horiba LA 900 instrument. It is preferred to presonicate the sample for 1 
minute to break up any agglomerations to obtain a base value of particles 
smaller than 40 microns. When the catalyst is activated, as later 
described, the sonication number of the silica-modified aluminophosphate 
composition is generally from about 5 minutes to about 350 minutes. 
Generally, the fragmentation potential is greater than about 10 percent, 
preferably about 30 percent or greater and more preferably in the range of 
from 20 percent to 60 percent. This is accomplished by mixing the reagents 
in the aqueous solution with sufficient shear and the concentration of 
reactants is sufficiently high. 
As used herein, "sonication number" is the amount of time necessary to 
reach a mean particle size of 40 microns determined by using a Malvern 
Particle Size Analyzer with 300 mm focal length and an active beam length 
of 2 mm. The sonication number is inversely proportional to the 
fragmentation potential. 
The sonication number of the silica-modified aluminophosphate composition 
is generally from about 5 minutes to about 200 minutes, preferably from 
about 10 minutes to about 150 minutes, and more preferably from 20 minutes 
to 100 minutes. 
The inventive silica-modified aluminophosphate compositions exhibit 
excellent thermal stability. Typically, the compositions exhibit less than 
thirty percent loss of surface area after heating at 600.degree. C. for 2 
hours versus heating for 8 hours at 30.degree. C. 
As discussed above, the silica-modified aluminophosphate compositions of 
this invention exhibit a microstructure of sheets of silica-modified 
aluminophosphate as well as spheres of silica-modified aluminophosphate. 
In order to observe the sheets, the silica-modified aluminophosphate is 
spray dried to form particles about 0.01 cm in diameter. Microscopic 
examinations of these particles is done using standard transmission 
electron microscope (TEM) techniques. For example, the TEM specimen is 
observed in the bright field imaging mode. 
Microtomy technique is a well established specimen preparation technique in 
the field of transmission electron microscopy. The technique is described 
in standard reference published literature, for example T. F. Malis and D. 
Steele, "Ultramicrotomy for Materials Science", in "Workshop on specimen 
preparation for TEM of materials II", ed. R. Anderson, vol. 199, Materials 
Research Symposium Proceedings (MRS, Pittsburgh, 1990) and N. Reid, 
"Ultramicrotomy", in the "Practical Methods in Electron Microscopy" 
series, ed. A. M. Glauert, Publ. Elsevier/North Holland, 1975. 
Microtomy technique involves embedding the sample in a resin, from a pellet 
by polymerizing the resin in a mold, then cut thin sections using a 
microtone equipped with a diamond knife. A preferred resin is L. R. White 
resin. The typical thin section has a thickness of about 0.06 microns. 
Care should be taken to embed whole aluminophosphate particles in order 
that views of the entire random cross sections of the aluminophosphate 
particles are presented. 
It is also important that prudent sampling techniques are to collect the 
sample for the TEM specimen preparation step. The portion of 
aluminophosphate particles that are embedded is selected from a sample by 
sequentially dividing the originally collected sample into quarter 
portions until the desired amount of material suitable for the embedding 
process is reached. 
For purposes of this specification, printed images of photomicrographs 
having a destination magnification of 12,000.times..+-.1200.times. is 
suitable. The term destination magnification is defined as the sum of the 
magnification on the negative image and the magnification that occurs when 
the negative is further magnified when printed to larger size. This 
destination magnification takes into account some newer machines which use 
cameras to produce a digital image onto a computer for possible printing 
at a later time. 
The cross section of spheres by a plane as well as the projection of 
spheres onto a plane will both result in round features. In this case, the 
round particles tend to be smaller than the thickness of the microtome 
sections. Hence, the round particles are viewed in projection in the 
images. 
The characteristic sheets of silica-modified aluminophosphate appear as 
lines in the micrographs. The sheets can also be observed by crushing the 
samples instead of by microtomy. Crushing the sample breaks apart the 
whole aluminophosphate particles into small fragments then scatters the 
fragments onto thin electron transparent supports. 
An image analysis technique has been developed to quantify the amount of 
sheets per unit volume in a given sample. This is based on general 
mathematical expressions that relate the features of the microstructure 
(interfaces, lines, and points) and intersections with an arbitrary test 
line. The equations are set forth in C. S. Smith and L. Guttman, 
"Measurement of internal boundaries in three dimensional structures by 
random sectioning", Trans. AIME, vol. 197, p. 81, (1953). 
A quantitative representation of the amount of sheet material in the 
aluminophosphate composition is represented by the equation: 
EQU S.sub.v =4N.sub.L 
S.sub.v is the interface area per unit volume, in units of mm.sup.2 
/mm.sup.3 or micron.sup.2 /micron.sup.3. 
N.sub.L is the average number of intersections per unit length between a 
random test line, and the traces of the extended surface in the image 
units of mm.sup.-1 or micron.sup.-1. 
Explanations and example application of stereological analysis to the 
characterization of microstructures can be found in the text books by R. 
T. DeHoff and F. N. Rhines, "Quantitative Microscopy", Publ. 
TechBooks/McGraw Hill, 1968 and J. C. Russ, "Computer-Assisted 
Microscopy," Plenum Press, 1990. 
An example for determining N.sub.L is as follows. Select at least five 
representative printed images of 8.5 in..times.11 in. size at 
12,000.times. destination magnification. Overlay a set of random test 
lines drawn on a transparent sheet of paper on the image. The orientation 
of these lines must be random with respect to the line features resulting 
from the sheets. The total length of these lines on the transparency 
should be at least 150 cm. The number of intersections between the test 
lines and the lines on the image is determined and divided by the total 
length of the test lines. The numerical results for N.sub.L should be 
presented in micron.sup.-1. Care must be taken to convert the distances 
measured on the photomicrographs into correct units of length which 
includes the effect of the image magnification. 
Generally, the silica-modified aluminophosphate compositions have an 
N.sub.L in the range of from about 0.01 micron.sup.-1 to about 3 
micron.sup.-1, preferably from about 0.1 micron.sup.-1 to about 3 
micron.sup.-1, more preferably from 0.1 micron.sup.-1 to 2 micron.sup.-1, 
and most preferably from 0.1 micron.sup.-1 to 1 micron.sup.-1. 
The inventive silica-modified aluminophosphate compositions exhibit the 
combination of a relatively high macropore volume, 0.1 cc per gram or 
greater, a fragmentation potential of 30 percent or greater, and a 
mesopore volume of 0.1 cc per gram or greater. The combination of high 
macropore volume and a fragmentation potential above 30 generally results 
in an aluminophosphate which is physically unstable. This is not the case 
of the present silica-modified aluminophosphate composition, however. 
The aluminophosphate compositions have a wide variety of uses including 
their use as a support for catalysts. In particular, the new 
silica-modified aluminophosphate compositions are useful as supports for 
alpha olefin polymerization catalysts, such as for the polymerization of 
ethylene. Because of their high macropore volume, the aluminophosphate 
compositions find use in the treatment of residua and gas oils, but can 
also be tailored for use as an FCC catalyst or for use in hydroprocessing 
such as hydrodenitrification, hydrodesulfurization, hydrocracking or 
hydrogenation. 
Polymerization catalysts can be prepared by impregnating the 
aluminophosphate composition with a catalytic amount of at least one 
transition metal-containing compound. A catalytic amount is the amount 
necessary to polymerize the olefin. 
Catalysts useful in the polymerization of olefins, such as ethylene, 
generally contain a transition metal selected from Groups IIIA, IVA, VA, 
VIA, VIIA, VIII, IB, and IIB such as titanium, zirconium, hafnium, 
vanadium, chromium, manganese, iron, cobalt, nickel, platinum, copper, or 
zinc. 
Generally, the transition metal will be present in an amount of 0.1 weight 
percent or greater based on the total catalyst weight, preferably in the 
range of from about 0.1 weight percent to about 15 weight percent, more 
preferably in the range of from 0.1 weight percent to 10 weight percent. 
Chromium and mixtures of chromium and titanium are especially preferred. 
Chromium compounds used in preparing the catalyst can be selected from 
various organic or inorganic forms of chromium. Suitable chromium 
compounds include chromic anhydride, chromium chloride, chromium nitrate, 
chromium acetate, and chromium trioxide. Preferably, the aluminophosphate 
composition impregnated with the chromium salt is calcined to convert the 
chromium to an oxide form. 
When employing titanium, various titanium compounds can be used to prepare 
the catalysts. One preferred source for the titanium component is titanium 
tetraisopropoxide. 
Generally, a chromium catalyst is prepared by impregnating a selected 
chromium compound onto the aluminophosphate support. Typically, a solution 
of the chromium compound can be admixed with an aqueous slurry of the 
aluminophosphate composition. The water can be removed by drying at 
50.degree. C. to 200.degree. C. for several hours. One preferred method of 
drying is spray drying which yields relatively large particle sizes and 
eliminates the need for screening the catalyst. The catalysts are 
generally activated by heating in air or other oxygen-containing gas at 
300.degree. F. to 950.degree. F. 
In the alternative, a water-soluble transition metal compound, such as a 
chromium compound, can be incorporated into the aqueous solution 
containing aluminum ions and phosphate ions. The transition metal is thus 
precipitated with the aluminum and phosphorous. The precipitate is then 
dried and calcined as previously described. 
Another type of catalyst can be prepared by depositing organochromium 
compounds on an activated support. The organochromium compound is 
typically dissolved in an appropriate solvent. The solvent is then removed 
by evaporation. Suitable organochromium compounds include 
dicyclopentadienyl chromium (II) and triphenylsilyl chromate. It is not 
necessary to heat activate the catalyst after the addition of the 
organochromium compound. 
Although not required, a suitable cocatalyst can be employed to form a 
catalyst system. Examples of such cocatalysts are disclosed in U.S. Pat. 
No. 4,690,990, the disclosure of which is incorporated herein by 
reference. Suitable cocatalysts include triethylborane, diethylaluminum 
ethoxide, triethylaluminum, ethylaluminum sesquichloride. Generally, the 
cocatalyst is present in an amount up to about 15 mole percent of the 
catalyst system, preferably about 0.1 to about 12 mole percent of the 
catalyst system. 
Typical olefin polymerization processes include slurry and gas phase 
polymerization. These processes differ significantly with respect to the 
dynamics of particle growth. Accordingly, catalysts which are effective in 
one olefin polymerization process are frequently not effective in another 
process. The inventive silica-modified aluminophosphate supports are 
effective in both batch and gas phase polymerization processes. 
The catalysts are suitable for polymerizing at least one mono-1-olefin 
containing 2 to 12 carbon atoms, preferably 2 to 8 carbon atoms. Suitable 
olefins include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 
4-methyl-1-pentene and octene. 
The invention is especially effective for producing ethylene homopolymers 
and copolymers. Typical commoners include alpha-olefins containing from 3 
to 12 carbon atoms. Preferred alpha-olefin comonomers are propylene, 
1-butene, 1-pentene, 1-hexene and mixtures thereof. Dienes such as 
1,3-butadiene, isoprene, piperylene, 2,3-dimethyl-1,3-butadiene, 
1,4-pentadiene, 1,7-hexadiene and mixtures thereof are also suitable 
comonomers. 
When employed, preferred amounts of the comonomer feed are in the range of 
from about 0.01 to about 10 mole percent of the total ethylene feed, more 
preferably about 0.1 to about 3 mole percent of the total ethylene feed, 
and most preferably 0.2 to 2.0 mole percent of the total ethylene feed. 
The polymerization process can be carried out in various types of reactors. 
For example, a mechanically stirred reaction zone in a horizontal or 
vertical reactor or a fluidized bed in a vertically disposed reactor can 
be used. A fluidized bed is disclosed in U.S. Pat. No. 4,011,382. The bed 
of catalyst particles/polyethylene is fluidized by upwardly flowing 
ethylene gas. 
The catalyst of this invention can be used in solution polymerization, 
slurry polymerization and gas phase polymerization techniques using 
conventional equipment and contacting processes. 
Temperatures and pressures used in the polymerization process of the 
present invention are those sufficient for the polymerization of ethylene. 
Generally, polymerization temperatures are in the range of from about 
50.degree. F. to 250.degree. F. Preferred pressures are below 500 psig, 
preferably between 100 psig and 500 psig, more preferably between 150 psig 
and 400 psig, and most preferably between 250 psig and 350 psig. 
The present catalyst is especially suitable for slurry polymerization. The 
slurry or particle form process is generally carried out in an inert 
diluent such as paraffin, cycloparaffin or aromatic hydrocarbon. 
Temperatures employed are generally in the range of from about 50.degree. 
C. to 150.degree. C. Pressures generally range from 110 to 700 psia 
(0.65-4.8 Mpa) or higher. The catalyst is kept in suspension and is 
contacted with the monomer(s) under conditions sufficient to maintain at 
least a portion of the monomer in the liquid phase. The medium and 
temperature are selected so that the polymer is produced as solid 
particles and is recovered in that form. Catalyst concentrations are 
generally in the range of from about 0.001 to about 1 weight percent based 
on the weight of the reactor contents. 
The present catalysts are also useful in gas phase fluid bed polymerization 
process. During the gas phase process, ethylene and/or other gaseous alpha 
olefins are injected into the bottom of a fluid bed reactor. Catalyst is 
injected appropriately into the reactor and polymer is formed and grows on 
the catalyst. The polymer particles must have a proper size to density or 
the fluid bed will tend to collapse during operation. Usually, the polymer 
mimics the shape of the prior art catalyst particles, which are generally 
spherical and uniform in size. Polymer particles prepared according to the 
present invention are irregularly shaped and exhibit a variety of sizes. 
Conditions in the gas phase process can vary broadly. Generally, the 
temperature is in the range of from about 20.degree. C. to about 
200.degree. C., preferably 50.degree. C. to about 150.degree. C. The 
pressure is typically in the range of from atmospheric to 70 kg/cm.sub.2 
G, preferably from atmospheric to 70 kg/cm.sub.2 G. 
Hydrogen can be used to control the molecular weight. When used, it is 
generally present in an amount up to about 2 mole percent of the reaction 
mixture, preferably with the range of about 0.1 to about 1 mole percent of 
the reaction mixture. 
The following examples will serve to show the present invention in detail 
by way of illustration and not by way of limitation.

EXAMPLES 
Example 1 
Preparing Silica-Modified Aluminophosphate Precipitate 
Silica-modified aluminophosphate precipitate was prepared by adding 6.49 Kg 
of deionized water to a mixing tank that was heated to 50.degree. C. With 
mixing, 15 Kg of Al(NO.sub.3).sub.3.9H.sub.2 O (97% by weight) was added 
to the water. Mixing was continued until the solid dissolved. The pH of 
the aluminum solution was about 0. To the aluminum solution was added 
2,284.4 grams of phosphoric acid (85% by weight) with mixing. 
A silicate solution was prepared by diluting 250 grams of a Banco sodium 
silicate solution (41.degree. Be)(the specific gravity is 1.401). The 
silica solution was added to the aluminophosphate solution over a 5-minute 
period resulting in a solution having a pH of about 0. 
A separate solution of ammonium hydroxide (15% by weight) was prepared. The 
aluminum, phosphorus and silica-containing solution and the ammonium 
hydroxide solution were simultaneously pumped into the mixing chamber of a 
Ross High Shear Mixer. The rate of addition of acid and base solution into 
the mixing chamber is set to achieve a pH of 8.0 at the outlet of the 
mixer. 
The hydrogel was washed with deionized water until a conductivity level of 
about 3000 mmohs was achieved. The hydrogel was then concentrated to about 
18 wt. % solids. The concentrated hydrogel was pumped to the feed system 
of a Stark Bowen BE 1235 spray dryer and dried. The spray dryer conditions 
were varied, by means well known to those having ordinary skill in the 
art, to achieve a desired particle size, LOM weight percent and other 
desired characterized. The spray dired powder was calcined at 450.degree. 
C. for 8 hours in a fixed fluid bed reactor. 
Example 2 
Preparing Catalyst 
Catalyst was prepared by dissolving a predetermined amount of CrO.sub.3 in 
deionized water and adding the CrO.sub.3 solution to a slurry of a 
predetermined amount of silica-modified aluminophosphate in deionized 
water. The mixture was placed in an evaporating flask which was attached 
to a vacuum and placed in a hot water bath at 80.degree. C. When the water 
was evaporated, the thus prepared chromium catalyst was removed and 
employed in various polymerization runs. 
Example 3 
Analyzing the Microstructure of Silica-Modified Aluminophosphate 
The composition of the silica-modified aluminophosphate sheets were 
analyzed by the energy dispersive x-ray (EDX) spectrometry method carried 
out inside the transmission electron microscope (TEM). This is a well 
known technique within the field of electron microscopy. The only physical 
requirement to perform this analysis is for the TEM to be fitted with an 
EDX detector and the associated computer hardware and software to analyze 
the EDX spectrum. These are considered as standard accessories to the TEM 
and there are many commercial manufacturers of EDX systems. The spectrum 
from the TEM-EDX analysis reveals the elemental composition of the 
material being irradiated by the electron beam probe. 
In this case, the composition of the sheet structures were obtained by 
condensing the electron beam into a small probe by adjusting the condenser 
lens current. The size of the probe was chosen such that it was smaller 
than the width (thickness) of the sheet to be analyzed. This small 
electron probe was placed exactly on the sheet structure and an EDX 
spectrum was acquired. The acquisition was stopped when sufficient number 
of counts were accumulated, to the point where it was deemed statistically 
satisfactory to make a judgment on whether Si was present. The same 
process was repeated for many sheet structures. 
For the elemental composition of the silica-modified aluminophosphate 
spheres in the matrix, the same procedure was carried out but the electron 
beam probe chosen was generally of a larger size. The critical point in 
choosing the size and placement of the electron beam probe was to make 
sure that the analyzed areas did not contain sheet structures. 
This EDX analysis verified that Si was present in both the sheets and the 
spheres. 
Example 4 
Catalyst Activations 
Catalyst activations were performed on a bench-scale 28 mm diameter 
fluidized bed under a stream of dry air at 600.degree. C. for 8 hours. The 
activator tube is constructed from a 28 mm diameter quartz tube, a medium 
quartz frit, and a 67 mm diameter quartz disengaging section. The 
fluidization section is 300 mm long from the frit to the half angle 
transition, and the disengaging section is 400 mm tall. The transition 
incorporates an 11.degree. half angle. The whole activator tube is 
enclosed in a 1100.degree. C. Lindberg tube furnace and can be purged with 
dry argon or low dewpoint air, typically at .about.1 L/min. Gas flow 
direction is from the bottom to the top, and a cyclone trap is connected 
to the outlet to collect fines, which might otherwise escape into the 
atmosphere. 
Example 5 
Batch Polymerization Runs 
Polymerizations were performed in two liter autoclave reactors equipped 
with Genesis control systems. A dried 316 stainless steel two liter 
Autoclave Engineers Zipperclave reactor system was heated at 80.degree. C. 
under vacuum until a pressure of &lt;50 microns of Hg was achieved. The 
reactor was then charged with a mixture of 200 mg catalyst and 0.5M (0.65 
mg) of isobutylaluminoxane (Al to Cr ratio of 5) in 200 mL heptane 
contained in a 500 mL glass addition funnel that was fitted with a Kontes 
vacuum valve. The isobutylaluminoxane was added to scavenge unwanted 
catalyst poisons such as oxygen. A Kontes valve was connected to the 
reactor on a Cajon Ultra-Torr fitting, and the mixture was introduced into 
the reactor under vacuum. The reactor was stirred at 550 rpm and ethylene 
was introduced to an internal setpoint pressure of 300 psig. The reactor 
temperature was maintained at the setpoint temperature 80.degree. C. with 
a Neslab RTE-100 water-bath/circulator. The reaction was allowed to 
proceed to a given productivity, typically depletion of 80 L of ethylene 
after which the reactor was vented and purged twice with argon and shut 
down. The reactor was opened while it was still hot and the contents were 
quickly removed. The reactor was cleaned and prepared for the next 
reaction. Table 1 shows the results of five reactions performed as 
described above. 
TABLE 1 
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Activity 
Al.sub.2 O.sub.3 .multidot. 2AlPO.sub.4 .multidot. Run g PE/ 
Run xSiO.sub.2 mole % Cr wt. % 
Time hr. g Cat. .multidot. hr. 
______________________________________ 
101 0.5 0.7. 0.91 575 
102 0.5 0.35 0.79 529 
103 1 0.35 0.78 497 
104 0.5 0.7 1.02 605 
______________________________________