Large pore alumina-supported transition metal alkyl

In a process for polymerizing a 1-olefin with a catalyst system comprising a reaction product of a porous alumina and an organometallic compound of the formula (RCH.sub.2).sub.4 M wherein M is Ti, Zr, or Hf and R is a group which is such that there is no hydrogen atom attached to an atom which is in the .beta.-position to M, and more specifically, R is aryl, aralkyl, tertiary alkyl, for example, trialkylmethyl, or trialkylsilyl, the improvement characterized in that the alumina has an average pore diameter of at least about 150 A and/or at least about 10% of the total pore volume of the alumina is provided by pores having diameters greater than about 200 A.

DESCRIPTION 
1. Technical Field 
This invention relates to a catalyst system for polymerizing 1-olefins. 
More particularly, it relates to products formed by reacting aluminas 
whose surfaces have pores of relatively large diameters with selected 
tetrahydrocarbyl derivatives of Group IVa metals, and to their uses as 
catalyst systems in such polymerizations. 
2. Background 
U.S. Pat. No. 3,840,508 discloses a process for polymerizing olefinically 
unsaturated monomers using as an initiator a reaction product of a 
transition metal complex and a matrix material which has a hydroxylated 
surface but which is otherwise substantially inert. 
Copending application Ser. No. 917,281 filed June 20, 1978 and now U.S. 
Pat. No. 4,228,263 discloses a catalytic process for preparing elastomeric 
polymers of propylene. The catalyst, which is a reaction product of a 
metal oxide and an organometallic compound of the formula 
(RCH.sub.2).sub.4 M wherein M is Zr, Ti or Hf and R is aryl, aralkyl, 
tertiary alkyl or trialkylsilyl, is prepared in situ in a solvent 
consisting principally of liquid propylene. A similar process for 
preparing elastomeric polypropylene, using the catalyst system of U.S. 
Pat. No. 3,932,307, infra, is disclosed in British Specification 
2,001,080. 
U.S. Pat. No. 3,932,307 discloses a process for polymerizing 1-olefins with 
the catalyst which consists essentially of the reaction product of 
tetraneophylzirconium and a hydroxylated oxide of a metal of Group IIa, 
IIIa, IVa or IVb of the Periodic Table of the Elements. Fumed alumina, 
i.e., alumina prepared by burning aluminum chloride in the presence of 
water vapor, is an exemplified preferred metal oxide and provides an 
especially active catalyst system. Related catalyst systems and 
polymerization processes are disclosed in U.S. 3,950,269; 3,971,767; and 
4,011,383. 
Although catalyst systems employing fumed alumina are highly active, the 
use of such alumina has certain disadvantages in that it is relatively 
expensive, its preparation is energy consumptive, and it has a relatively 
low bulk density (about 0.055 g/ml), which makes it inconvenient to 
handle. A need exists, therefore, for a material which: can be substituted 
for the fumed alumina; provides a highly active catalyst system; is easy 
to handle and relatively inexpensive to prepare; and is not unduly energy 
consumptive in its preparation.

DISCLOSURE OF INVENTION 
For further comprehension of the invention, and of the objects and 
advantages thereof, reference may be made to the following description and 
accompanying drawings, and to the appended claims in which the various 
novel features of the invention are more particularly set forth. 
The invention herein is based on the discovery that active catalysts for 
polymerizing 1-olefins can be obtained by reacting tetraneophylzirconium 
or other selected tetrahydrocarbyl derivatives of a Group IVa metal with a 
porous alumina which has an average pore diameter of at least about 150 A 
and/or at least about 10% of whose total pore volume is provided by pores 
having diameters greater than about 200 A. Aluminas of this type are 
available commercially; alternatively, they can be made by procedures that 
are described hereinafter. As far as is known, all such aluminas are made 
by precipitation methods and, consequently, they are less expensive to 
prepare than fumed aluminas. In addition, they have relatively high bulk 
densities (for example, about 0.30-0.35 g/ml for commercially available 
materials) and are easy to handle. 
The average pore diameter of an alumina, along with its surface area, can 
be determined as follows. First, the isotherms for nitrogen adsorption and 
desorption are measured by conventional techiques. The data from these 
determinations are fed to a computer, which effects the calculations and 
prepares the numerical and graphical information described below. The 
calculation of surface area is based on the wellknown B.E.T. adsorption 
isotherm (Brunauer, Emmett, and Teller, J. Am. Chem. Soc. 60, 309 (1938)). 
The pore-volume distribution as a function of pore diameter is calculated, 
assuming cylindrical pores, by the method of B. F. Roberts, J. Colloid and 
Interface Sci. 23, 266 (1967), in which the Kelvin equation of capillary 
condensation is used to relate the capillary diameter to the nitrogen gas 
pressure. The average pore diameter is calculated from the B.E.T. surface 
area and the total measured saturation volume from the equation d=10.sup.4 
(4V/S) wherein d is the average pore diameter in angstroms, V is the total 
measured saturation volume in (cm.sup.3 /g), and S is the B.E.T. surface 
area in (m.sup.2 /g.) 
The computer generates bar graphs of pore-volume distribution. Such graphs 
are illustrated in FIGS. 1 and 2 wherein pore volumes (in ml) are plotted 
against pore diameters (in A); these graphs give the pore-volume 
distributions for the aluminas used in Examples 1 and 2, respectively. The 
area in any one bar of such a graph divided by the total area of all the 
bars gives the fraction of the total pore volume contributed by pores 
having diameters in the range corresponding to the particular bar. 
Similarly, the sum of the areas in two or more adjoining bars, divided by 
the total area, gives the percentage of total pore volume contributed by 
pores having diameters over the range corresponding to the bars in 
question. 
To determine whether a particular alumina will give an active catalyst in 
the present invention, it is usually sufficient merely to determine its 
average pore diameter. As noted above, any porous alumina having an 
average pore diameter of at least about 150 A will provide such an active 
catalyst. However, it is conceivable that an alumina may have a relatively 
large number of pores of extremely small diameters and a relatively small 
number of pores of large diameters, so that the average pore diameter 
would be below 150 A, and yet be usable to form an active catalyst because 
of its large-diameter pores. A secondary method of predicting whether an 
alumina forms an active polymerization catalyst on reaction with an 
organo(transition metal) compound can be used. Any alumina in which at 
least about 10% of the total pore volume is provided by pores having 
diameters greater than about 200 A is operable in the present invention. 
In general, it is preferred that the average pore diameter be as large as 
possible, although it is to be understood that once a certain average 
diameter is reached, no further improvement in carrying out the process of 
the invention will be realized by further increasing the alumina pore 
diameter. 
The organometallic compound used in the invention is of the formula 
(RCH.sub.2).sub.4 M wherein M is Ti, Zr, or Hf and R is a group which is 
such that there is no hydrogen atom attached to an atom, usually a carbon 
atom, which is in the .beta.-position to M. More specifically, R is aryl, 
aralkyl, tertiary alkyl, for example, trialkylmethyl, or trialkylsilyl. 
Examples of RCH.sub.2 -- include neophyl, benzyl and trimethylsilylmethyl. 
Representative organometallic compounds include tetraneophyl zirconium, 
-titanium or -hafnium, tetraneopentyl zirconium, -titanium or -hafnium, 
and tetrabenzyl zirconium, -titanium or -hafnium. 
The 1-olefins that can be homopolymerized and/or copolymerized by means of 
the catalysts and polymerization processes of this invention include, in 
particular, ethylene, propylene, butene-1, pentene-1, hexene-1, heptene-1, 
octene-1, nonene-1, decene-1, 1,3-butadiene, 1,4-hexadiene, and other 
dienes having at least one terminal olefinic group. Homopolymers and 
copolymers which can be and/or have been prepared by the process of this 
invention, some of which preparations are described in the examples 
hereinafter, include ethylene and propylene homopolymers, 
ethylene-propylene copolymers and ethylene-propylene-1,4-hexadiene 
terpolymers. 
The process conditions for carrying out homopolymerizations or 
copolymerizations with the catalysts of the invention are those commonly 
used in the art for polymerizing 1-olefins with catalysts of the general 
type employed here. In connection therewith, reference may be made to the 
background discussion provided hereinabove. For example, the 
polymerizations can be conducted at 10.degree.-300.degree. C. at pressures 
of 1-1000 atmospheres (1-1000.times.10.sup.5 Pa) or more, using slurry or 
solution polymerization techniques. Inert hydrocarbon media, including 
alkanes and cycloalkanes, such as n-hexane, n-heptane, or cyclohexane, and 
aromatic componds, such as toluene, can be employed. Known means can be 
used to control molecular weight and/or molecular weight distribution. 
EXAMPLE 1 
A. Preparation of Alumina 
A solution of 80 g of ammonium nitrate in 100 cc of water was added to a 
solution of 375 g of aluminum nitrate nonahydrate in one liter of water. 
The resulting solution was poured into a solution of 300 cc of 
concentrated ammonium hydroxide in 300 cc of water in a plastic beaker. A 
thick white precipitate appeared. The mixture was allowed to stand for 5 
minutes and was then cooled in dry ice. After the contents had frozen, the 
beaker was removed from the dry ice, and the mixture was allowed to thaw 
and then filtered. The solid on the filter was washed with water until 
substantially free of base, washed with acetone, air-dried, and then dried 
at 120.degree. C. for 24 hours. The white powdery alumina thus obtained 
weighed 62 g and had a volume of 333 ml (0.19 g/ml). Its surface area was 
463 m.sup.2 /g; average pore diameter, 173 A; and pore volume, 2.00 ml/g. 
After being heated at 400.degree. C. for 4 hours, its surface area was 497 
m.sup.2 /g; average pore diameter, 180 A; and pore volume, 2.24 ml/g. FIG. 
1 depicts the pore-volume distribution for this alumina. 
B. Polymerization of Propylene 
A dry, oxygen-free, 1-liter, stainless-steel autoclave equipped with a 
stirrer was charged with a suspension of 60 ml of cyclohexane and 2 g of 
the alumina of Part A, to which had been added 0.2 mmol of 
tetraneophylzirconium as a 0.1 M solution in toluene. The autoclave was 
cooled in dry ice/acetone and charged with 168 g of propylene. On stirring 
and warming, an exothermic polymerization occurred, causing the 
temperature to rise at 70.degree. C. The mixture was stirred at 
70.degree.-50.degree. C. and autogeneous pressure for 1 hour from the time 
when the temperature first reached 50.degree. C., after which volatile 
materials were removed by evaporation and the polymer was air-dried. The 
elastomeric polypropylene thus produced weighed 151 g (90% yield) and had 
properties typical of those of known elastomeric polypropylenes. 
C. Polymerization of Propylene 
In a confirmatory experiment, the procedure of Part B was substantially 
repeated. An exothermic polymerization again took place, the temperature 
rising from 50.degree. C. to 66.degree. C. in four minutes. The yield of 
elastomeric polypropylene was 140 g (83% yield). 
COMATIVE EXPERIMENT 1 
A. Example 1B was substantially repeated, except that the catalyst was made 
from an alumina having an average pore diameter of 67 A, i.e., a catalyst 
outside this invention. Only 10 g (6% yield) of polypropylene was 
produced. 
B. The procedure of Part A was substantially repeated, except that 20 g of 
ethylene was charged in addition to the other materials. Also, in this 
experiment 0.15 mmol of tetraneophylzirconium was used instead of 0.20 
mmol as in Part A; this difference would not be expected to affect the 
yield substantially. In spite of the fact that ethylene is easier to 
polymerize than propylene with catalysts of this type made from active 
aluminas, the yield of solid polymer, presumably an ethylene/propylene 
copolymer, was only 12 g (6% yield). 
EXAMPLE 2 
A. Polymerization of Propylene 
The alumina used in this example was Alcoa.RTM. XF-100 (about 0.30-0.35 
g/ml bulk density) that had been heated at 400.degree. C. for 4 hours in a 
stream of nitrogen. Following this treatment its average pore diameter was 
208 A; surface area, 121 m.sup.2 /g; and pore volume, 0.63 ml/g. Its 
pore-volume distribution is depicted in FIG. 2. The process of Example 1B 
was substantially repeated except that the amount of tetraneophylzirconium 
was 0.25 mmol and the amount of cyclohexane was 100 ml. Drying the solid 
product at 120.degree. C. for 1 hour gave 46.5 g (28% yield) of 
elastomeric polypropylene. Its properties were typical of known 
elastomeric polypropylenes. 
B. Polymerization of Propylene; Effect of Washing Alumina with Acid 
The alumina used in Part A apparently had base associated with it. This was 
shown by adding water to indicator paper that was in contact with the 
alumina. A 25-g sample of the alumina was suspended in 200 ml of distilled 
water, and 44 ml of 0.2 M sulfuric acid was added. The mixture was stirrer 
for 30 minutes, and the solid was separated by filtration, washed with 
water, and dried. A small sample was dried further at 400.degree. C. in a 
stream of nitrogen for 4 hours for use in the following polymerization. 
The procedure of Part A was substantially repeated, except that 0.2 mmol of 
tetraneophylzirconium was used and the temperature was 
48.degree.-55.degree. C. The amount of elastomeric polypropylene recovered 
was 69 g (41% yield). 
EXAMPLE 3 
Copolymerization of Ethylene and Propylene 
The autoclave of Example 1B was charged with 300 ml of cyclohexane, 168 g 
of propylene, and 20 g of ethylene. The mixture was heated at 125.degree. 
C., at which temperatures a slurry of 1 g of the alumina of Example 1A, 60 
ml of cyclohexane, and 0.2 mmol of tetraneophylzirconium was charged. The 
resulting pressure (800 psi, 5516 KPa) was maintained at 125.degree. C. 
with ethylene until about 20 g of ethylene (measured by weight difference) 
in addition to the original ethylene charged had been consumed. This 
required 19 minutes. Pressure was then released, and the reactor was 
cooled. The solid product was separated and dried at 120.degree. C./0.5 mm 
for 3 hours, to give 60 g (29% yield, a good yield at the 125.degree. C. 
polymerization temperature) of a very soft elastomeric ethylene/propylene 
copolymer. 
EXAMPLE 4 
High-Temperature Polymerization of Ethylene 
A dry, oxygen-free, stainless-steel autoclave was charged with a suspension 
of 1.5 g of the acid-treated dried alumina of Example 2B in 500 ml of 
cyclohexane. The autoclave was closed and heated at 260.degree. C., at 
which temperature ethylene was injected until the internal pressure had 
been increased by 300 psi (2068.5 KPa). Then a solution of 0.15 mmol of 
tetraneophylzirconium in 50 ml of cyclohexane was pressured in with 
stirring. After 5 minutes at 260.degree. C. the initial pressure (840 psi, 
5791.8 KPa) had dropped to 740 psi (5102.3 KPa). At this point the excess 
pressure was released and the reactor was cooled. There was obtained 12 g 
of polyethylene, which was shown by gel-permeation chromatography to have 
a M.sub.w of 8300, a M.sub.n of 1200, and a polydispersity index of 6.87, 
all the evaluations being carried out using conventional procedures. The 
curve of molecular-weight distribution had two peaks of the same 
intensity. 
EXAMPLE 5 
An autoclave like that of Example 1B was charged with 2 g of Alcoa.RTM. 
XF-100 alumina (Example 2A) and 100 ml of cyclohexane. It was closed, 
charged with 168 g of propylene, and heated to 50.degree. C. with 
stirring. At this temperature 50 ml of cycohexane containing 0.2 mmol of 
tetrabenzylzirconium as a 0.1 M solution in toluene was injected. An 
exothermic reaction occurred and the temperature rose to 70.degree. C., 
returning to 50.degree. C. in 8 minutes. The polymerization was continued 
at 50.degree. C. for 1 hour after injection of the tetrabenzylzirconium, 
and the product was isolated as in Example 1B to give 47 g (28% yield) of 
elastomeric polypropylene. 
EXAMPLE 6 
The alumina in this example was Alcoa.RTM. type B boehmite (alumina 
monohydrate) that had been calcined at 550.degree. C. in a stream of 
nitrogen for 18 hours. A sample of the same material that had been 
calcined at 400.degree. C. under nitrogen for 4 hours had an average pore 
diameter of 202.3 A. Using substantially the same procedures described in 
Example 1B, 70 ml of cyclohexane. 1.5 g of boehmite, 0.2 mmol of 
tetraneophylzirconium, and 168 g of propylene were processed at 50.degree. 
C. and autogeneous pressure for 1 hour. The elastomeric polypropylene thus 
produced weighed 43 g (26% yield). 
BEST MODE FOR CARRYING OUT THE INVENTION 
The process of the invention is best carried out with a catalyst prepared 
from alumina having a large average pore diameter, as more fully described 
hereinabove. 
INDUSTRIAL APPLICABILITY 
The industrial applicability of 1-olefin polymers, as well as catalysts and 
processes for preparing such polymers, is well known to one skilled in 
this art. 
Although preferred embodiments of the invention have been illustrated and 
described in the above disclosure, it is to be understood that there is no 
intent to limit the invention to the precise constructions herein 
disclosed, and it is to be further understood that the right is reserved 
to all changes and modifications coming within the scope of the invention 
as defined in the appended claims.