High surface aluminas are pre-calcined to form gamma-alumina. In one embodiment, the gamma-alumina is treated with an anhydrous solution of a fluorine-containing compound. In a second embodiment, alumina is precipitated in the pores of the gamma-alumina and then treated with a fluorine-containing compound. In a third embodiment a cogel of aluminum trifluoride and aluminum hydroxide is prepared. The three inventive fluorided alumina supports can be impregnated with a transition metal, preferably chromium, to form a catalyst system which can be used to polymerize mono-1-olefins.

BACKGROUND OF THE INVENTION 
This invention relates to treated alumina. 
Supported chromium oxide catalysts have long been used to prepare olefin 
polymers to give products having excellent characteristics from many 
standpoints. A number of supports have long been broadly disclosed in the 
art for chromium oxide catalysts including silica, alumina, thoria, 
zirconia, silica-alumina, and other refractory materials. However, as a 
practical matter only predominately silica supports have achieved 
substantial commercial success. Alumina, which is almost always included 
in the prior art in the list of suitable supports, while operable, 
invariably causes productivity to be extremely low. The preferred prior 
art support, silica, also suffers from disadvantages among which is the 
inability to produce ultra high molecular weight polymer using hexavalent 
chromium. 
SUMMARY OF THE INVENTION 
It is an object of this invention to provide an improved catalyst support. 
It is another object of this invention to provide an improved alumina, 
which can be used as a catalyst support. 
It is a further object of this invention to provide an improved 
polymerization catalyst. 
It is yet another object of this invention to provide a chromium catalyst 
capable of giving high productivity. 
It is yet a further object of this invention to provide an improved olefin 
polymerization process. 
It is yet a further object of this invention to provide an improved process 
for preparing supported chromium olefin polymerization catalysts. 
In accordance with one embodiment of this invention a fluorided alumina is 
prepared by calcining a large pore, high surface area alumina to form a 
calcined gamma-alumina and contacting the calcined gamma-alumina with an 
anhydrous solution of a fluorine-containing compound. 
In accordance with a second embodiment of this invention, an 
alumina-in-gamma-alumina is prepared by calcining a large surface area 
alumina to form a calcined gamma-alumina; contacting the calcined 
gamma-alumina with a sufficient amount of a solution of an aluminum 
compound up to incipient wetness; contacting the incipiently wet product 
with an alumina precipitating compound to form a precipitated alumina in 
the calcined gamma-alumina; removing any residual solution of aluminum 
compound and any residual aluminum precipitating compound from the 
precipitated alumina in the calcined gamma-alumina; and drying the 
resultant compound. While not wishing to be bound by theory, it is 
believed that the resultant composition comprises boehmite alumina in 
calcined gamma-alumina, i.e., alumina-in-gamma-alumina. This 
alumina-in-gamma-alumina composition can then be impregnated with a 
fluorine-containing compound to form another type of fluorided alumina. 
In accordance with yet a third embodiment of this invention, an alumina 
cogel can be prepared by dissolving a fluorine-containing compound with a 
base; neutralizing that solution by mixing it with a water-soluble 
aluminum salt solution to form a hydrated aluminum oxy-fluoride cogel, 
(AlF.sub.3).x(Al.sub.2 O.sub.3). 
Any of the three above-mentioned fluorided aluminas can be used as a 
catalyst support for a transition metal, preferably chromium, to form a 
catalyst system useful to polymerize mono-1-olefins. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Supports 
The support of the catalyst of this invention is a fluorided 
alumina-containing material. As used in this disclosure, the term 
"support" refers to a carrier for another catalytic component. However, a 
support is not necessarily an inert material; a support can contribute to 
catalytic activity and/or catalytic productivity. Furthermore, a support 
can have an effect on the properties of the resultant polymer produced. 
The starting material is an alumina-containing material which can contain 
other ingredients which are present to produce some unrelated result 
and/or which do not adversely affect the quality of the final catalyst. 
For example, other metal oxides, such as boria, magnesia, silica, thoria, 
titania, zirconia, and mixtures thereof, can be present without adverse 
affects. Preferably, the support is at least 75 weight percent alumina and 
preferably 85 weight percent alumina, based on the weight of the 
alumina-containing material, in order to achieve optimum catalyst quality, 
as well as improved polymer characteristics. Usually, the starting alumina 
will comprise some silica. 
The starting alumina-containing material, hereinafter also referred to as 
"alumina" or "base alumina", must be a high surface area, large pore 
volume alumina and must be calcined prior to use. Usually, the surface 
area of the starting alumina, after one hour of calcination at 600.degree. 
C., will be greater than about 200 square meters per gram (m.sup.2 /g) and 
preferably within the range of about 200 to about 600 m.sup.2 /g. Most 
preferably, the starting alumina will have a surface area within the range 
of about 250 to about 500 m.sup.2 /g for easier fluoride and catalyst 
loading, improved productivity, and greater durability. Usually, the pore 
volume of the starting alumina will be greater than 0.5 milliliters per 
gram (ml/g) and preferably within the range of about 0.5 to about 2.5 
ml/g. Most preferably, the starting alumina will have a pore volume within 
the range of about 1 to about 2 ml/g for greater durability. 
Exemplary starting aluminas are commercially available. Preferred 
commercially available base aluminas are commonly referred to as Ketjen B 
or Ketjen L. Typical Ketjen B or Ketjen L aluminas, as used in the present 
invention, will have typical analyses as given in Table I, below. 
TABLE I 
______________________________________ 
Ketjen B 
Ketjen L 
______________________________________ 
Loss on ignition 25 25 
(1 hr., 1000.degree. C., 
wt. % wet base) 
Chemical Composition 
(wt. % dry base) 
Alumina, Al.sub.2 O.sub.3 
Balance Balance 
Sodium oxide, Na.sub.2 O 
0.1 0.15 
Sulfate, SO.sub.4 1.5 2.0 
Silicon dioxide, SiO.sub.2 
1.0 5.0 
Iron, Fe 0.03 0.03 
Physical Properties 
Surface Area, M.sup.2 /g 
340 380 
(1 hr., 600.degree. C.) 
Apparent bulk density, g/ml 
0.3 0.3 
Pore Size Distribtuion (radius) 
&lt;37.5 .ANG., ml/g 0.20 0.20 
37.5-100 .ANG., ml/g 0.18 0.18 
100-1000 .ANG., ml/g 0.74 0.74 
1000-10,000 .ANG., ml/g 
0.51 0.71 
10,000-75,000 .ANG., ml/g 
0.15 0.17 
Total pore volume, ml/g 
1.78 2.00 
Particle Size Distribution (% wt.) 
-149 micron 98 95 
-105 micron 65 60 
-74 micron 39 30 
-40 micron 19 15 
Average particle size, micron 
85 95 
______________________________________ 
Prior to treatment with, or contacting, a fluoriding agent, the alumina 
must be calcined. As used in this disclosure, the terms "gamma-alumina", 
"calcined alumina", and "calcined, gamma-alumina" are used interchangeably 
and refer to the calcined base alumina, described above. The alumina is 
calcined under conditions of temperature and time sufficient to convert 
substantially all of the alumina to gamma-alumina and to remove 
substantially all water. Generally, temperatures within the range of about 
300.degree. to about 900.degree. C., for times within a range of about 1 
minute to about 48 hours are sufficient. Temperatures under about 
300.degree. C. and times of less than about 1 minute can be insufficient 
to convert substantially all of the alumina to gamma-alumina. Temperatures 
of greater than about 900.degree. C. and times of greater than about 48 
hours do not convert a significantly greater portion of the alumina to 
gamma-alumina. Preferably, temperatures within the range of about 
500.degree. to about 800.degree. C. and times within the range of about 30 
minutes to about 24 hours are employed. Most preferably, temperatures 
within the range of about 500.degree. to about 700.degree. C. and times 
within the range of about 1 hour to about 6 hours are employed. The 
calcining can be carried out under an oxidizing, reducing, or inert 
atmosphere; the principal purpose of the atmosphere is to sweep away 
moisture. 
The term "fluorided" is meant to describe an alumina support treated with a 
fluorine-containing compound as described herein. The terms "fluoride 
treatment" and "fluoriding" are meant to refer broadly to the fluorine, 
i.e., fluorine-containing compound, or fluoriding agent. Reaction of the 
fluorine-containing compound with an alumina support can take place on 
impregnation or on activation. Any organic or inorganic 
fluorine-containing compound which can provide fluoride can be used in 
this invention. Exemplary fluorine-containing compounds include, but are 
not limited to, ammonium bifluoride (NH.sub.4 HF.sub.2), ammonium 
fluoroborate (NH.sub.4 BF.sub.4), ammonium silicofluoride 
((NH.sub.4).sub.2 SiF.sub.6), and mixtures thereof. The most preferred 
fluorine-containing compound is ammonium bifluoride, due to ease of use 
and availability. While not wishing to be bound by theory, it is believed 
that the fluoride in inorganic fluorine-containing compounds, which can 
provide free fluoride in solution, attaches to the gamma-alumina in 
solution. It is also believed that the fluoride inorganic 
fluorine-containing compounds does not attach to the gamma-alumina in 
solution, but can attach to the gamma-alumina upon catalyst system 
activation. 
In accordance with one embodiment of the invention, the fluoriding 
treatment must be done with a substantially anhydrous fluorine-containing 
compound, since the base alumina has been calcined and substantially all 
water has been removed from the alumina. The calcined, gamma-alumina and 
the fluorine-containing compound can be contacted according to any method 
known in the art. For ease of preparation, an anhydrous 
fluorine-containing compound can be prepared, or dissolved, with any 
anhydrous liquid, preferably an anhydrous alcohol. Most preferably, the 
anhydrous liquid is an alcohol with from about 1 to about 3 carbon atoms 
per molecule for better solubility of the fluoriding-agent. If the 
fluorine-containing compound is dissolved in an anhydrous liquid, the 
alumina can be mixed, or slurried, with the anhydrous fluorine-containing 
compound solution. 
Sufficient fluorine-containing compound is combined with the alumina in 
order to achieve from about 4 to about 14 weight percent fluoride, 
preferably from about 4 to about 10 weight percent fluoride, based on the 
weight of the calcined alumina used. Most preferably, the fluorine loading 
is within the range of from about 5 to about 9 weight percent fluorine, 
for best catalyst system activity and productivity. 
After addition of the fluorine-containing compound to the alumina, a 
chromium compound can be added to the support. The support can be dried, 
i.e., removal of substantially all liquid, prior to chromium addition, but 
drying is not essential. In accordance with this first embodiment, 
however, it is sometimes useful that the fluorine-containing compound be 
added to the alumina prior to, and not simultaneously with or subsequent 
to, the addition of a chromium compound. Some fluorine-containing 
compounds can precipitate the chromium if a fluorine-containing compound 
is added simultaneously with a chromium compound. Furthermore, while not 
wishing to be bound by theory, it is believed that the fluorine-containing 
compound has a greater affinity to alumina if a fluorine-containing 
compound is added prior to the chromium compound. 
In accordance with a second embodiment of this invention, the fluoriding 
treatment is done with an alumina-treated-alumina or an alumina 
precipitated in gamma-alumina compound. As with the first embodiment, a 
base alumina must be calcined to convert the base alumina to gamma-alumina 
prior to any subsequent treatment. These calcining conditions are the same 
as those previously described for the first embodiment of the invention. 
The calcined gamma-alumina is then treated with an aqueous solution of 
aluminum ions. Any aluminum compound soluble in water can be used. For 
ease of use and availability, the most preferred aluminum compounds 
include aluminum nitrate (Al(NO.sub.3)), aluminum sulfate (Al.sub.2 
(SO.sub.4).sub.3), aluminum chloride (AlCl.sub.3), and mixtures thereof. A 
concentrated aqueous solution of aluminum ions is added to the calcined 
gamma-alumina and adsorbed into the pores of the calcined gamma-alumina. A 
sufficient amount of aqueous aluminum solution is added to be equal to or 
less than incipient wetness. The concentration of the aqueous aluminum 
solution can be any concentration such that about 1 to about 25 weight 
percent aluminum, based on the weight of the calcined gamma-alumina, is 
adsorbed or deposited into the pores of the calcined gamma-alumina. 
Preferably, about 1 to about 20 weight percent aluminum, and must 
preferably, about 2 to about 15 weight percent aluminum is deposited into 
the pores of the calcined gamma-alumina. 
After the aqueous aluminum impregnation of the gamma-alumina compound, any 
basic compound which can provide hydroxyl (OH.sup.-) groups to precipitate 
the aluminum ions is added. Preferably, for compatibility and ease of use, 
an aqueous solution of a basic compound is used. For ease of use and 
availability, the preferred basic compound is ammonium hydroxide (NH.sub.4 
OH). Any amount of basic compound can be added which is sufficient to 
precipitate the aluminum ions. Thus, lesser quantities of a concentrated 
basic solution or greater quantities of a dilute basic solution can be 
used. An excess of basic compound usually is not detrimental to the final 
support and catalyst system in that any excess can be subsequently 
removed. 
After sufficient basic compound is added to precipitate the desired amount 
of alumina into the pores of the gamma-alumina, excess aluminum ions 
and/or excess basic compound(s) can be removed by any method known in the 
art. Usually, for ease of use, excess aluminum ions and/or excess basic 
compound(s) can be removed by washing the resultant product. Preferably, 
for compatibility and safety, the wash solution is water. 
Upon completion of the water wash, the support, which now comprises 
alumina-precipitated-in-gamma-alumina is washed in an organic liquid of 
low surface tension such as, for example, an alcohol, and is dried to 
remove substantially all liquid. The drying can be performed in any manner 
known in the art which does not collapse the support. Preferably, drying 
is done under a vacuum, at temperatures within the range of from about 
70.degree. to about 90.degree. C. in order to best maintain pore 
integrity. While not wishing to be bound by theory, it is believed that 
drying the alumina-in-gamma-alumina composition at relatively low 
temperatures, the precipitated alumina is boehmite alumina, and not 
gamma-alumina. Thus, the alumina-precipitated-in-alumina compound 
comprises boehmite alumina within the pores of gamma-alumina. 
The alumina-in-gamma-alumina composition can be used as a catalyst support. 
Preferably, the composition can be further treated with a 
fluorine-containing compound in any manner known in the art, as disclosed 
in the first embodiment. Preferably, a fluorine-containing compound is 
dissolved in an anhydrous liquid, and then this anhydrous solution of the 
fluorine-containing compound is contacted with the 
alumina-in-gamma-alumina support. The amount of fluorine-containing 
compound employed in the second embodiment is the same as that in the 
first embodiment of the invention. Finally, the resultant support, either 
wet or dry, can be contacted with a chromium compound. 
Although not wishing to be bound by theory, it is believed that the 
effectiveness of the second embodiment comes from the following 
explanation. The support matrix is first calcined at high temperatures, 
which converts boehmite to gamma-alumina and makes the alumina more 
resistant to attack by fluoride. Onto this "hard" framework is deposited a 
"soft" layer of aluminum hydroxide (Al(OH).sub.3), which is converted to 
boehmite alumina. Fluoride later tends to preferentially attack the "soft" 
layer, which puts more fluoride onto the surface without damaging the 
support structure. 
A third embodiment of this invention can be defined as a cogel of aluminum 
trifluoride (AlF.sub.3) and aluminum hydroxide. Preparation of the 
aluminum trifluoride can be done by dissolving any fluorine-containing 
compound with, or in, a base. Due to ease of use and safety, ammonium 
bifluoride (NH.sub.4 HF.sub.2), the most preferred fluorine-containing 
compound, can be dissolved in ammonium hydroxide (NH.sub.4 OH). The basic 
fluorine-containing compound solution is then mixed with a water soluble 
aluminum compound to neutralize the two solutions to form an aluminum 
trifluoride/aluminum hydroxide cogel, also referred to as an 
aluminum-oxy-fluoride cogel. The aluminum-oxy-fluoride, or 
aluminum-hydroxide-fluoride, cogel can then be combined with a chromium 
compound or can be calcined to convert the alumina to gamma-alumina, 
resulting in a complex with a generic representation as AlF.sub.3 
xAl.sub.2 O.sub.3, wherein x can be any fraction or number greater than 
zero. After chromium addition, the catalyst system must be activated, as 
described in this disclosure. 
Usually, the AlF.sub.3.xAl.sub.2 O.sub.3 complex will comprise less than 
about 75 weight percent AlF.sub.3, calculated as AlF.sub.3, and preferably 
less than about 60 weight percent AlF.sub.3. Most preferably, the 
AlF.sub.3.xAl.sub.2 O.sub.3 will comprise from about 10 to about 50 weight 
percent AlF.sub.3 calculated as AlF.sub.3, for best support physical 
characteristics, as well as best resultant catalyst system productivity. 
While not wishing to be bound by theory, it is believed the third 
embodiment is best represented by a generic representation of 
AlF.sub.3.xAl.sub.2 O.sub.3. However, generic representation can be some 
type of matrix, or network, of aluminum and fluoride, or fluorine. 
Usually, the mole ratio of fluorine to aluminum (F:Al) is less than about 
2:1, preferably, less than about 1.5:1. Most preferably, the mole ratio of 
fluorine to aluminum is within the range of 0.1:1 to 1.2:1 for reasons 
given above. 
The order of addition of this third inventive embodiment is extremely 
important. The fluorine-containing compound must be combined with a basic 
compound prior to, i.e., before, the addition of a water soluble aluminum 
compound. If the water soluble aluminum compound is combined directly with 
a fluorine-containing compound, the fluorine-containing compound can 
precipitate alone as aluminum trifluoride. 
CATALYST SYSTEMS 
Catalyst systems employed in the practice of this invention comprise a 
fluorided, predominately gamma-alumina support, prepared as described 
above, and a transition metal compound, such as chromium. Other suitable, 
but less preferred, transition metal compounds are vanadium and titanium 
compounds. It should be recognized, however, that catalyst systems of the 
invention can be used in conjunction with additional polymerization 
components which do not adversely affect the catalyst performance, such as 
a cocatalyst. 
The transition metal compound can be introduced anytime prior to activation 
of the catalyst system. Where the transition metal compound is chromium, 
the chromium compound can be any chromium compound in, or convertible to, 
the hexavalent state. The catalyst system contains chromium in an amount 
generally within the range of about 0.001 to about 10, preferably about 
0.1 to about 5, more preferably about 1 weight percent, based on the 
weight of the dried, fluorided alumina support, to provide a catalyst with 
a high activity. 
Catalyst system concentrations in a polymerization reactor can be such that 
the supported catalyst system content ranges from 0.001 to about 1 weight 
percent based on the weight of the reactor contents. 
The chromium compound can be incorporated in any of several known in the 
art. One method to incorporate a chromium compound is to use an aqueous 
solution of a water-soluble chromium compound which is convertible to 
chromium oxide upon calcination. Examples of water-soluble chromium 
compounds include, but are not limited to, chromium acetate and chromium 
nitrate which precipitate out with the alumina. Chromium trioxide and 
other Cr(.sup.+ 6) compounds can also be used, but are less preferred 
because they are too soluble and tend to drain off with the excess water. 
Chromium compounds can also be incorporated anhydrously into the alumina. A 
hydrocarbon solution of a chromium compound convertible to chromium oxide 
can be used to impregnate the alumina. Examples of such materials include, 
but are not limited to, tert-butyl chromate and chromium acetylacetonate. 
Suitable solvents include, but are not limited to, alcohols, pentanes, 
hexanes, and/or benzenes. Preferably, anhydrous chromium impregnation is 
used to maintain the integrity of the pre-calcined, fluorided, 
gamma-alumina support. 
Calcination can take place by heating the chromium-impregnated fluorided 
alumina in the presence of an excess of molecular oxygen at a temperature 
within the range of about 300.degree. to about 800.degree. C., preferably 
about 300.degree. to about 600.degree. for about 30 minutes to about 50 
hours, more preferably for about 0.5 to about 10 hours. At least a 
substantial portion of the chromium in low valence state is converted to 
the hexavalent form. Preferably, activation is carried out in a stream of 
fluidizing air which is continued as the material is cooled. 
POLYMERIZATION 
The catalysts of this invention can be used to polymerize at least one 
mono-1-olefin containing about 2 to about 8 carbon atoms per molecule, 
preferably ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 
4-methyl-1-pentene, 1-octene, and mixtures thereof. The invention is of 
particular applicability in producing ethylene homopolymers and copolymers 
from mixtures of ethylene and 0.5 to 20 mole percent of one or more 
comonomers selected from 1-olefins containing 3 to 8 carbon atoms per 
molecule. Exemplary comonomers include aliphatic 1-olefins, such as 
propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene and 
other higher olefins and conjugated or non-conjugated diolefins such as 
1,3-butadiene, 1,4-pentadiene, 1,5-hexadiene, and other such diolefins, 
and mixtures thereof. Ethylene copolymers preferably constitute at least 
about 90, preferably 97 to 99.8 mole percent polymerized ethylene units. 
With ethylene/hexene copolymers, about 98 to 99.8 mole percent ethylene is 
preferred, the remainder of course being the comonomer. Propylene, 
1-butene, 1-pentene, 1-hexene and 1-octene are especially preferred 
comonomers for use with ethylene. 
The polymers can be prepared from the catalyst of this invention by 
solution polymerization, slurry polymerization, gas phase polymerization, 
or other polymerization techniques using conventional equipment and 
contacting processes. Contacting of the monomer or monomers with the 
catalyst can be effected by any manner known in the art of solid catalyst. 
One convenient method is to suspend the catalyst in the organic medium and 
to agitate the mixture to maintain the catalyst in suspension throughout 
the polymerization process. Other known contacting methods such as 
fluidized bed, gravitating bed, and fixed bed can also be employed. 
Reference to the production of ethylene polymers in a particle form 
process is disclosed in U.S. Pat. No. 3,624,603 which issued Nov. 30, 1971 
to Witt, the disclosure of which is hereby incorporated by reference. 
Catalysts of this invention are particularly suitable for use in slurry 
polymerizations. The slurry, or particle form, process is generally 
carried out in an inert diluent (medium) such as paraffin, cycloparaffin 
or aromatic hydrocarbon. For predominantly ethylene polymers, a 
temperature of about 66.degree. to about 110.degree. C. is employed. 
Pressures in the particle form process can vary from about 110 to about 
700 psia (0.65-4.8 MPa) or higher. The catalyst is kept in suspension and 
is contacted with the monomer or monomers at sufficient pressure to 
maintain the medium and at least a portion of the monomer or monomers in 
the liquid phase. The medium and temperature are thus selected such that 
the polymer is produced as solid particles and is recovered in that form. 
Catalyst concentrations can be such that the catalyst content ranges from 
0.001 to about 1 weight percent based on the weight of the reactor 
contents. 
Hydrogen can be used to control molecular weight, as is known in the prior 
art. When used, it is generally used at concentrations up to about 2 mole 
percent of reaction mixture, preferably within the range of about 0.1 to 
about 1 mole percent of reaction mixture. 
Cocatalyst, to enhance the polymerization reaction, can be used as is known 
in the prior art. Examples of cocatalysts include, but are not limited to, 
triethylborane, diethylaluminum ethoxide, triethylaluminum, ethylaluminum 
sesquichloride, and mixtures thereof. When used, a cocatalyst is usually 
present at concentrations up to about 15 mole percent of reaction mixture, 
preferably within the range of about 0.1 to about 12 mole percent of the 
reaction mixture.

EXAMPLES 
Examples I, II, and III pertain to the first embodiment of the invention, 
wherein the support comprises an anhydrous solution of a 
fluorine-containing compound impregnated onto gamma-alumina. Example IV 
pertains to the second embodiment of the invention wherein, the support 
comprises a fluorine-containing compound impregnated onto boehmite alumina 
precipitated in gamma-alumina. Example V shows the third embodiment of the 
invention wherein the support comprises a cogel of aluminum trifluoride 
and aluminum hydroxide, AlF.sub.3.xAl.sub.2 O.sub.3. In all Examples, 
ambient temperature and ambient pressure were used, unless otherwise 
indicated. The surrounding atmosphere was air, unless otherwise indicated. 
Polymerization tests were carried out in a two-liter stirred autoclave. 
Typically about 0.05 to 0.10 gm of activated catalyst was charged to the 
reactor under nitrogen, then one liter (about 600 grams) of isobutane 
liquid diluent was added, and finally ethylene was supplied on demand to 
maintain a fixed pressure of 550 psig. Polymerization occurred at 
95.degree. C. At the end of each run, the isobutane and ethylene were 
flashed off, leaving a dry polymer powder. Each run was terminated by 
stopping the ethylene flow and venting the gaseous reactor contents to a 
flare line for disposal. The polymer was recovered, dried and weighed to 
determine catalyst productivity which is expressed in terms of grams 
polyethylene per gram catalyst. 
Catalyst support surface areas were determined on 35-140 mesh samples using 
the standard nitrogen sorption BET method. Catalyst support pore volumes 
were measured by alcohol adsorption according to the Journal of Colloid 
and Interface Science, Vol. 78, No. 1. 
EXAMPLE I 
The following Runs show a minor improvement in activity which can be 
achieved by conventional fluoriding, at low levels, of uncalcined alumina. 
Both water and alcohol were used. Ammonium bifluoride (NH.sub.4 HF.sub.2), 
ACS reagent grade, dissolved in methanol, ACS reagent grade, or deionized 
water, was impregnated onto virgin, i.e., untreated or unheated, Ketjen L 
alumina, commercially available from ARMAK Corporation. The weight percent 
of NH.sub.4 HF.sub.2 present in the catalyst support is based on the 
weight of the Ketjen L alumina immediately prior to the addition of 
NH.sub.4 HF.sub.2. The fluorine-containing alumina, i.e., catalyst 
support, was then dried and impregnated with chromium nitrate, ACS reagent 
grade, in methanol to equal 2 weight percent chromium, based on the weight 
of dried catalyst support. Then, the chromium impregnated support was 
activated in dry air at 500.degree. C. to form a catalyst system. The 
results are given in Table II. 
TABLE II 
______________________________________ 
Support Productivity, 
Weight % Surface g/polymer/g 
Run Solvent NH.sub.4 HF.sub.2 
Area, m.sup.2 /g 
catalyst/30 mins 
______________________________________ 
101 Water 0 394 31 
102 " 1 361 66 
103 " 2 397 119 
104 " 3 382 140 
105 " 4 400 181 
106 " 5 346 188 
107 Methanol 0 406 50 
108 " 3 391 89 
109 " 5 381 201 
______________________________________ 
EXAMPLE II 
The following Runs demonstrate the need for the base alumina to be calcined 
first. Again, Ketjen L alumina was used, but with and without calcining at 
600.degree. C. for one hour, prior to introduction of ammonium bifluoride 
(NH.sub.4 HF.sub.2), to convert the boehmite alumina to gamma-alumina. The 
NH.sub.4 HF.sub.2 solvent was methanol. The weight percent of NH.sub.4 
HF.sub.2 present in the catalyst support is based on the weight of the 
Ketjen L alumina immediately prior to the addition of NH.sub.4 HF.sub.2. 
The data in Table III are for supports wherein the base alumina was not 
pre-calcined. The data in Table IV are for supports wherein the base 
alumina was pre-calcined at 600.degree. C. for one hour prior to 
contacting NH.sub.4 HF.sub.2. 
The fluorine-containing alumina, i.e., catalyst support after drying or 
calcining, was then impregnated with chromium nitrate, ACS reagent grade, 
in methanol to equal 2 weight percent chromium, based on the weight of 
dried catalyst support. Then, the chromium impregnated support was 
activated in dry air at 500.degree. C. or 750.degree. C., to form a 
catalyst system. The results are given in Tables III and IV. 
TABLE III 
______________________________________ 
Activation Support Productivity, 
Weight % Temperature, 
Surface g polymer/g 
Run NH.sub.4 HF.sub.2 
.degree.C. Area, m.sup.2 /g 
catalyst/30 mins 
______________________________________ 
201 0 500 406 50 
202 3 500 391 89 
203 5 500 381 201 
204 0 750 367 477 
205 3 750 313 433 
206 5 750 267 306 
______________________________________ 
TABLE IV 
______________________________________ 
Activation Support Productivity, 
Weight % Temperature, 
Surface g/polymer/g 
Run NH.sub.4 HF.sub.2 
.degree.C. Area, m.sup.2 /g 
catalyst/30 mins 
______________________________________ 
210 0 500 331 240 
211 1 500 326 272 
212 3 500 315 516 
213 5 500 292 877 
214 0 750 322 727 
215 1 750 306 645 
216 3 750 294 948 
217 5 750 260 256 
______________________________________ 
EXAMPLE III 
Table V shows the advantages of using higher fluoride loadings, i.e., 
greater than 5 weight percent NH.sub.4 HF.sub.2, based on the weight of 
the calcined alumina, and of using lower activation temperatures. The 
catalyst systems were prepared as described in Example II, wherein the 
Ketjen L alumina was calcined at 600.degree. C. for one hour prior to the 
introduction of NH.sub.4 HF.sub.2. 
TABLE V 
______________________________________ 
Support Productivity, 
Weight % Activation Surface g polymer/g 
Run NH.sub.4 HF 
Temp. Area, m.sup.2 /g 
catalyst/30 mins 
______________________________________ 
301 6 500 309 1537 
302 7 500 315 1140 
303 8 500 281 1315 
304 10 500 264 1180 
305 12 500 273 1344 
306 14 500 257 949 
307 16 500 261 1134 
308 5 750 260 256 
309 6 600 303 1200 
310 12 600 279 764 
311 14 600 263 583 
312 8 400 276 740 
313 10 400 275 805 
314 12 400 275 1053 
315 14 400 266 370 
316 16 400 274 216 
______________________________________ 
EXAMPLE IV 
Sufficient amounts of an aqueous aluminum nitrate solution, in order to 
obtain from 3 to 10 weight percent aluminum, based on the weight of the 
calcined Ketjen L, was impregnated onto Ketjen L alumina. The Ketjen L 
alumina was precalcined at 700.degree. C. for one hour. Impregnation with 
an aqueous aluminum nitrate solution was stopped just short of incipient 
wetness. Ammonium hydroxide was added to cause precipitation of aluminum 
hydroxide, i.e., "soft" alumina, inside the pores of the "hard" 
gamma-alumina, i.e., the pre-calcined Ketjen L alumina. The resultant 
boehmite alumina in gamma-alumina material was washed with water to be 
free of nitrate and excess ammonium hydroxide, then aged in water at 
80.degree. C. for one hour. The solid was filtered and then washed once 
with methanol, and finally dried at 80.degree. C. in a vacuum oven 
overnight. Then, a sufficient amount of ammonium bifluoride in a methanol 
solution, in order to obtain from 4 to 12 weight percent NH.sub.4 
HF.sub.2, based on the weight of the alumina-in-gamma-alumina support, was 
added to the alumina-in-gamma-alumina. The catalyst support was dried 
again in a vacuum oven at 80.degree. C. for 8 hours, and finally chromium 
nitrate in methanol was added to equal 2 weight percent chromium, based on 
the weight of the dried, fluorided alumina-in-gamma-alumina support. 
Activation occurred in dry air at 500.degree. C. for 3 hours. 
TABLE VI 
______________________________________ 
Weight % Support Productivity, 
"soft" Weight % Surface g/polymer/g 
Run aluminum NH.sub.4 HF.sub.2 
Area, m.sup.2 /g 
catalyst/30 mins 
______________________________________ 
401 3 4 385 1264 
402 3 8 339 1555 
403 3 12 303 3260 
404 3 12 397 2325 
405 6 12 300 2170 
406 10 12 312 1467 
______________________________________ 
Comparison of these activity numbers with the Runs in Tables IV and V show 
that, although the initial support preparation materials of the second 
embodiment are similar to those of the first embodiment, the support 
preparation procedure of the second embodiment yields a far more active 
catalyst system. 
EXAMPLE V 
A cogel of AlF.sub.3 and alumina, aluminum-oxy-fluoride 
(AlF.sub.3.xAl.sub.2 O.sub.3), containing greater than 10% by weight, 
AlF.sub.3, based on the weight of the total support, was prepared. In the 
following Runs, varying amounts of NH.sub.4 HF.sub.2 was dissolved in 250 
mls NH.sub.4 OH and 250 mls water, and this solution was used to 
neutralize an aqueous aluminum nitrate (Al(NO.sub.3).sub.3.9H.sub.2 O) 
solution (1000 g/l), yielding a co-precipitate of aluminum 
hydroxyfluoride. A co-precipitate was washed with water and filtered. A 
solid product was recovered, washed with n-propanol, and dried overnight 
at 80.degree. C. in a vacuum oven. The weight percent of AlF.sub.3, given 
in Table VII, is based on the weight of the total support, 
AlF.sub.3.xAl.sub.2 O.sub.3. 
The catalyst support comprising fluorine-containing alumina, i.e., 
aluminum-oxy-fluoride (AlF.sub.3.xAl.sub.2 O.sub.3), after drying or 
calcining was then impregnated with chromium nitrate, ACS reagent grade, 
in methanol to equal 2 weight percent chromium, based on the weight of 
dried catalyst support. Then, the chromium impregnated support was 
activated in dry air at 450.degree. C. or 500.degree. C., to form a 
catalyst system. The results are given in Tables III and IV. 
TABLE VII 
__________________________________________________________________________ 
Support 
Support 
Productivity, 
Weight % 
F:Al Activation 
Surface 
Pore g/polymer/g 
Run 
AlF.sub.3 * 
Mole Ratio 
Temp., .degree.C. 
Area, m.sup.2 /g 
Vol., cc/g 
catalyst/30/mins 
__________________________________________________________________________ 
501 
30 0.63:1 
450 177 -- 244 
502 
50 1.15:1 
450 116 -- 305 
503 
15 0.30:1 
450 309 -- 100 
504 
30 0.63:1 
500 141 1.3 191 
505 
50 1.15:1 
500 77 0.8 102 
506 
15 0.30:1 
500 256 1.0 613 
__________________________________________________________________________ 
Despite rather low porosity, the catalyst systems made from these gels 
still had some activity for ethylene polymerization, providing a novel 
support previously unknown for this purpose. 
While this invention has been described in detail for the purpose of 
illustration, it is not to be construed as limited thereby but is intended 
to cover all changes and modifications within the spirit and scope 
thereof.