U.S. patent application number 13/916276 was filed with the patent office on 2013-11-21 for selective olefin dimerization with supported metal complexes activated by alkylaluminum compounds or ionic liquids.
The applicant listed for this patent is Phillips 66 Company. Invention is credited to Helmut G. Alt, Christine Denner, Matthias Dotterl, Tanja Englmann, Roland Schmidt.
Application Number | 20130310619 13/916276 |
Document ID | / |
Family ID | 43411472 |
Filed Date | 2013-11-21 |
United States Patent
Application |
20130310619 |
Kind Code |
A1 |
Dotterl; Matthias ; et
al. |
November 21, 2013 |
SELECTIVE OLEFIN DIMERIZATION WITH SUPPORTED METAL COMPLEXES
ACTIVATED BY ALKYLALUMINUM COMPOUNDS OR IONIC LIQUIDS
Abstract
Methods for dimerizing alpha-olefins utilizing immobilized
buffered catalysts wherein the catalytic component is of the form:
##STR00001## where X is a halogen, n=2 or 3, M=Ti, V, Cr, Mn, Fe,
Co and Ni and R1, R2, R3 and R4 are selected from the group
consisting of hydrogen, alkyl, aryl, alkenyl, alkinyl, alkyloxy,
substituted aryl, and X are provided. A method for dimerizing
alpha-olefins utilizing the immobilized buffered catalysts and a
co-catalyst is also provided.
Inventors: |
Dotterl; Matthias;
(Bayreuth, DE) ; Schmidt; Roland; (Bartlesville,
OK) ; Englmann; Tanja; (Immenreuth, DE) ;
Denner; Christine; (Gefrees, DE) ; Alt; Helmut
G.; (Bayreuth, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Phillips 66 Company |
Houston |
TX |
US |
|
|
Family ID: |
43411472 |
Appl. No.: |
13/916276 |
Filed: |
June 12, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12828797 |
Jul 1, 2010 |
8487153 |
|
|
13916276 |
|
|
|
|
61222436 |
Jul 1, 2009 |
|
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Current U.S.
Class: |
585/513 |
Current CPC
Class: |
B01J 2531/842 20130101;
C07C 2/34 20130101; B01J 31/0295 20130101; C07C 2521/08 20130101;
B01J 37/0209 20130101; B01J 31/0231 20130101; C07C 2531/14
20130101; B01J 2231/20 20130101; B01J 37/0207 20130101; B01J
31/0272 20130101; C07C 2/32 20130101; B01J 31/0275 20130101; C07C
2531/22 20130101; B01J 21/08 20130101 |
Class at
Publication: |
585/513 |
International
Class: |
C07C 2/34 20060101
C07C002/34 |
Claims
1-9. (canceled)
10. A process for the dimerization of olefins comprising the steps
of: modifying a support material containing OH groups with air
alkylaluminum compound to form a modified support material; mixing
an organometallic complex of the formula ##STR00009## where X is a
halogen, n=2 or 3, M=Ti, V, Cr, Mn, Co and Ni and R1, R2, R3 and R4
are selected from the group consisting of hydrogen, and X with one
or more co-catalysts selected from the group of MAO and
B(C.sub.6Fi).sub.3 and with the modified support material to form a
combined catalyst; and mixing the combined catalyst with one or
more alpha-olefins.
11. The process of claim 10 wherein the alkylaluminum compound is
chloroethylaluminum.
12. The process of claim 10 wherein the support is silica, zeolite,
partially hydrolyzed trimethylaluminum, or a mixture thereof.
13. The process of claim 10 wherein the one more alpha-olefins is
selected from the group alkenes having between three and ten carbon
atoms.
14. The process of claim 10 wherein the olefin dimerization is
conducted in a fixed bed reactor.
15. (canceled)
16. A process for the dimerization of olefins comprising the steps
of: modifying a support material containing --H groups with an
alkylaluminum compound to form a modified support material; mixing
an ionic liquid having a melting point below about 100.degree. C.
with a buffer to form a buffered ionic liquid; mixing the buffered
ionic liquid with an organometallic complex of the formula
##STR00010## where X is a halogen, n=2 or 3, M=Fe and R1, R2, R3
and R4 are selected from hydrogen and X, and at least one of R1 and
R2=X, to form a buffered ionic liquid/catalyst complex; mixing the
buffered ionic liquid/catalyst complex with the modified support
material to form an immobilized buffered catalyst; and mixing the
immobilized buffered catalyst with one or more alpha-olefins.
17. The process of claim 16 wherein M=Fe, X=Cl, n=3 and up to three
of R1, R2, R3 and R4=hydrogen.
18. The process of claim 16 wherein the one or more alpha-olefins
is selected from the group alkenes having between five and ten
carbon atoms.
19. The process of claim 16 wherein the ionic liquid comprises a
salt selected from the group consisting of AlCl.sub.3AlRCl.sub.2
and AlR.sub.2Cl, where R is an alkyl chain.
20. The process of claim 16 wherein the ionic liquid comprises a
cation selected from the group consisting of ammonium, imidazolium,
sulfonium and phosphonium salts.
21. The process of claim 16 wherein the alkylaluminum compound is a
chloroethylaluminum.
22. The process of claim 16 wherein the support is silica, zeolite,
partially hydrolyzed trimethylaluminum, or a mixture thereof.
23. The process of claim 16 wherein the step of mixing the
immobilized buffered catalyst with one or more alpha-olefins is
conducted in a fixed bed reactor.
24. The process of claim 16 wherein the alpha-olefin dimerization
reaction comprises 1,2- or 2,1-insertion.
25. The process of claim 16 further comprising drying the
immobilized buffered catalyst to form a powder prior to the mixing
the immobilized buffered catalyst with one or more
alpha-olefins.
26. A process for the dimerization of olefins comprising the steps
of: modifying a support material containing OH groups with an
alkylaluminum compound to form a modified support material; mixing
an organometallic complex of the formula ##STR00011## where X is a
halogen, n=3, M=Fe and R1, R2, R3 and R4 are selected from the
group consisting of hydrogen and X, and at least one of R1 and
R2=X, with one or more co-catalysts selected from the group of MAO
and B(C.sub.6F.sub.5).sub.3 and with the modified support material
to form a combined catalyst; and mixing the combined catalyst with
one or more alpha-olefins.
27. The process of claim 26 wherein the alkylaluminum compound is a
chloroethylaluminum.
28. The process of claim 26 wherein the support is silica, zeolite,
partially hydrolyzed trimethylaluminum, or a mixture thereof.
29. The process of claim 26 wherein the one or more alpha-olefins
is selected from the group alkenes having between three and ten
carbon atoms.
30. The process of claim 26 wherein the olefin dimerization is
conducted in a fixed bed reactor.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
Application No. 61/222,436, filed Jul. 1, 2009.
FEDERALLY SPONSORED RESEARCH STATEMENT
[0002] Not applicable.
REFERENCE TO MICROFICHE APPENDIX
[0003] Not applicable.
FIELD OF THE INVENTION
[0004] The invention relates to processes for dimerizing
alkenes.
BACKGROUND OF THE INVENTION
[0005] Dimerization of olefins is well known and industrially
useful. Further, the use of transition metals to catalyze olefin
dimerization and oligomerization is also known.
[0006] Use of ionic liquids for dimerization and oligomerization of
olefins is also well known. In the broad sense, the term ionic
liquids includes all molten salts, for instance, sodium chloride at
temperatures higher than 800.degree. C. Today, however, the term
"ionic liquid" is commonly used for salts whose melting point is
relatively low (below about 100.degree. C.). One of the earlier
known room temperature ionic liquids was [EtNH.sub.3]+[NO.sub.3]
(m.p. 12.degree. C.), the synthesis of which was published in 1914.
Much later, series of ionic liquids based on mixtures of
1,3-dialkylimidazolium or 1-alkylpyridinium halides and
trihalogenoaluminates, initially developed for use as electrolytes,
were to follow.
[0007] One property of the imidazolium halogenoaluminate salts was
that they were tuneable, i.e., viscosity, melting point and the
acidity of the melt could be adjusted by changing the alkyl
substituents and the ratio of imidazolium or pyridinium halide to
halogenoaluminate. Imidazolium halogenoaluminate salts exhibit
moisture sensitivity and, depending on the ratio of aluminum
halide, Lewis acidic or Lewis basic properties. Ionic liquids with
`neutral`, weakly coordinating anions such as hexafluorophosphate
([PF.sub.6].sup.-) and tetrafluoroborate ([BF.sub.4].sup.-) have
also been used as alternatives to imidazolium halogenoaluminate
salts. [PF.sub.6].sup.- and [BF.sub.4].sup.- based ionic liquids
are generally highly toxic. Yet another anion for use in ionic
liquids is bistriflimide [(CF.sub.3SO.sub.2).sub.2].sup.-, which
does not exhibit the toxicity of [PF.sub.6].sup.- and
[BF.sub.4].sup.- anions. Ionic liquids with less toxic cations are
also known, including those with compounds like ammonium salts
(such as choline) being used in lieu of imidazole.
[0008] Ionic liquids have found use as a catalyst in various
chemical reactions. For example, Lewis acidic ionic liquids have
been used as a catalyst to alkylate aromatic hydrocarbons, such as
the alkylation of benzene with ethylene. In such processes, the
ionic liquid itself serves as the catalyst, and the catalyst is
neither buffered nor immobilized on a support. Ionic liquids have
also been used in processes for making high viscosity
polyalphaolefins using an oligomerization catalyst including an
aluminum halide or alky-aluminum halides, and alkyl-substituted
imidazolium halide or pyridinium halide. In such processes, the
ionic liquid itself again serves as the catalyst and preferentially
forms high-viscosity polyalphaolefins due to the lack of
buffering.
[0009] Processes utilizing immobilized ionic liquids are also
known. For example, immobilized ionic liquids may be prepared by
functionalizing a support prior to contact with or forming the
ionic liquid. Such known immobilized ionic liquids however are not
buffered and therefore preferentially form high viscosity
polyolefins. Again, in such systems, the ionic liquid itself
functions as the catalyst.
[0010] Although all of the above methods are known and used in the
synthesis of olefins, what is needed in the art is an improved
synthetic method that allows for easy separation of the product.
Especially in the case of olefin dimerizations, which usually yield
liquids with relatively low viscosities or even gaseous olefins,
the application of supported systems that allows the use of fixed
bed reactors is superior to batch oligomerization, obviating the
need for further product separation. In addition, the catalytically
active surface may be maximized by use of high surface support
materials, which optimizes the catalytic performance.
SUMMARY OF THE INVENTION
[0011] Some embodiments of the invention provide a process for the
dimerization of olefins comprising the steps of: modifying a
support material containing OH groups with an alkylaluminum
compound to form a modified support material; mixing an ionic
liquid having a melting point below about 100.degree. C. with an
organometallic complex of the formula:
##STR00002##
where X is a halogen, n=2 or 3, M=Ti, V, Cr, Mn, Fe, Co and Ni and
R1, R2, R3 and R4 are selected from the group consisting of
hydrogen, alkyl, aryl, alkenyl, alkinyl, alkyloxy, substituted
aryl, and X to form an ionic liquid/catalyst complex; mixing the
ionic liquid/catalyst complex with the modified support material to
form an immobilized buffered catalyst; and mixing the immobilized
buffered catalyst with one or more alpha-olefins.
[0012] In some embodiments, M=Fe, X=Cl, n=3 and R1, R2, R3 and
R4=H. In yet other embodiments, the one or more alpha-olefins is
selected from the group alkenes having between three and ten carbon
atoms.
[0013] In certain embodiments of the invention, the ionic liquid
comprises an anion selected from the group consisting of
AlCl.sub.3, AlRCl.sub.2 and AlR.sub.2Cl, where R is an alkyl chain.
In yet other embodiments of the invention, the ionic liquid
comprises a cation selection from the group consisting of ammonium,
imidazolium, sulfonium and phosphonium salts. In a particular
embodiment, the alkylaluminum compound is chloroethylaluminum.
[0014] Other embodiments of the invention provide a process for the
dimerization of olefins comprising the steps of: modifying a
support material containing OH groups with an alkylaluminum
compound to form a modified support material; mixing an
organometallic complex of the formula:
##STR00003##
where X is a halogen, n=2 or 3, M=Ti, V, Cr, Mn, Fe, Co and Ni and
R1, R2, R3 and R4 are selected from the group consisting of
hydrogen, alkyl, aryl, alkenyl, alkinyl, alkyloxy, substituted
aryl, and X with one or more co-catalysts selected from the group
of methylaluminoxane (MAO) and B(C.sub.6F.sub.5).sub.3 to form a
combined catalyst; mixing the combined catalyst with one or more
alpha-olefins.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a gas chromatographic spectra of the reaction
products produced after five hours reaction per Example 2.
DESCRIPTION OF EMBODIMENTS OF THE INVENTION
[0016] In one embodiment of the invention, a process for dimerizing
olefins utilizes an organometallic catalyst dissolved in a buffered
ionic liquid immobilized on a support material.
[0017] For example, support material containing --OH groups may be
modified with one or more aluminumhalide, alkylaluminumdihalide,
and dialkylaluminumhalide or trialkylaluminum compounds
(generically, "AlXR.sub.3-n"). Generally, to achieve the support
modification, the support material is mixed with a solution of the
AlX.sub.nR.sub.3-n with stirring. Suitable solvents include
aromatics and paraffins having 5 or more carbon atoms, including by
way of example, toluene, benzene, pentane, hexane, cyclohexane and
dichloromethane.
[0018] Excess solvent may be removed following a reaction time from
between about 2 minutes to about 30 minutes, preferably between
about 5 and 25 minutes and most preferably between about 10 and
about 20 minutes. The result is a coated support material. Equation
(1) below illustrates an exemplary formation of a modified support
according to one embodiment of the invention.
##STR00004##
[0019] The ionic liquid is primarily a salt or mixture of salts
that melt below room temperature. In some embodiments of the
invention, the ionic liquid anion may be one or more of aluminum
halide, alkylaluminum halide, gallium halide or alkylgallium
halide. Preferably, the ionic liquid anion is one or more of
AlCl.sub.3, AlRCl.sub.2, or AlR.sub.2Cl where R is an alkyl chain.
In some embodiments of the invention, the ionic liquid cation may
be ammonium, imidazolium, sulfonium or phosphonium salt. In
preferred embodiments, the ionic liquid cation is selected from
ammonium halides containing one or more alkyl moieties having from
1 to about 9 carbon atoms, such as, for example,
trimethylbenzylammoniumchloride, or hydrocarbyl substituted
imidazolium halides, such as, for example,
1-butyl-3-methylimidazolium chloride.
[0020] The ionic liquid which will be used in producing the novel
catalyst composition may be produced by first separately dissolving
each of an acceptable cation and an acceptable anion in a solvent.
The dissolved cation and anion are then mixed followed by removal
of solvent.
[0021] In some embodiments of the invention, the ionic liquid is
buffered. For example, a buffered system of ionic liquid may be
produced utilizing one or more buffers having the general formula
R.sub.4Al.sub.2Cl.sub.2 or R.sub.2Al.sub.2Cl.sub.4 where the
neutral compounds are dissolved in an organic phase. For
example:
2[Et.sub.2Al.sub.2Cl.sub.5].sup.-2[AlCl.sub.4].sup.-+Et.sub.4Al.sub.2Cl.-
sub.2
2[Et.sub.2Al.sub.2Cl.sub.5].sup.-2[AlCl.sub.4].sup.-+Et.sub.2Al.sub.2Cl.-
sub.4.
[0022] In some embodiments, the quarternary amine is dissolved
first in methylene chloride and AlCl.sub.3 and stirred between 1
and 20 hours. The solvent is then removed by any of a number of
known methods, most preferably by vacuum. The buffered system is
then formed by addition of about 0.001 to about 0.2 equivalents
Et.sub.2AlCl to yield a ratio of the buffered system of
amine:AlCl.sub.3:Et.sub.2AlCl of about 1:1.22:0.2.
[0023] An organometallic catalyst is then mixed with the ionic
liquid. The organometallic catalyst may be selected from the group
of halogenated organometallic complexes wherein the metal is
selected from the group consisting of Ti, V, Cr, Mn, Fe, Co and Ni
and having the general formula shown by the formula below:
##STR00005##
where X is a halogen, n=2 or 3, M=Ti, V, Cr, Mn, Fe, Co and Ni and
R1, R2, R3 and R4 are selected from the group consisting of
hydrogen, alkyl, aryl, alkenyl, alkinyl, alkyloxy, substituted
aryl, and X.
[0024] The immobilized buffered catalyst is then formed by mixing
the organometallic catalyst/ionic liquid composition with the
coated support material. Following sufficient mixing, excess
solvent is removed, leaving an immobilized buffered catalyst solid
or powder material. The immobilized buffered catalyst may then be
mixed with one or more alpha-olefins to dimerize the olefins. In
some embodiments, the immobilized buffered catalyst is mixed with a
single alpha-olefin to form homogenous dimers or oligomers having
fifty or fewer monomer units.
Example 1
[0025] Silica Modification:
[0026] Commercially available silica (DAVICAT.RTM. SI 1102 from
W.R. GRACE & COO) was calcined at 400.degree. C. in dry argon
for 4 hours. The calcined silica (13.97 g) was slowly added to a 1
molar solution of Et.sub.2AlCl in toluene with vigorous stirring
(45 ml, 3-3.5 ml per g of calcined silica) and further stirred for
10-20 minutes. The toluene solution was decanted and the silica
washed 3 times with toluene.
[0027] Ionic Liquid Preparation:
[0028] 20.89 g 1-butyl-3-methylimidazolium chloride ("[BMIM]Cl")
95%, BASF) was dissolved in CH.sub.2Cl.sub.2. 19.43 g AlCl.sub.3
(1.22 mol, eq., REAGENT PLUS, SIGMA-ALDRICH.TM.) was suspended in
100 ml CH.sub.2Cl.sub.2 and the suspension was slowly transferred
to the solution of [BMIM]Cl. This addition was exothermic. The
methylene chloride solvent was removed by subjecting the mixture to
vacuum, heated to 70.degree. C. and left on high vacuum until no
more bubbles were observed. The result was a viscous, slightly
colored liquid.
[0029] Catalyst Preparation:
[0030] 10 ml of the ionic liquid was placed in a schlenk tube and
47.5 mg of unsubstituted bis(imino)pyridine-Fe(III)chloride-complex
(0.01 mmol/ml) was added and the mixture stirred for a few
seconds.
[0031] Catalyst Coating:
[0032] The toluene suspension of the coated support material was
slowly added to 8.9 ml (80 wt %) of the catalyst containing ionic
liquid with vigorous stirring. This mixture was stirred for 15
minutes to produce an immobilized buffered catalyst as shown in
equation (2) below. The toluene solvent was then decanted and the
remainder of the toluene was removed by application of high vacuum
to produce a powder.
##STR00006##
[0033] Dimerization of Propene in a Pressure Schlenk Tube:
[0034] 2.92 g of the prepared supported buffered catalyst was
placed in a pressure schlenk tube, vacuum applied and 50 ml of
liquid propene (>99.3% purity) condensed into the tube using
liquid nitrogen. The schlenk tube was then placed in a room
temperature water bath and stirred for 90 minutes. After the
pressure was released, 20.67 g of oligomer product remained in the
schlenk tube, which equals about 1550 kg Oligomer/mol.times.h. Gas
Chromatography ("GC") analysis revealed a dimer content of
95.9%.
[0035] Dimerization of Propene in a Fixed Bed Reactor:
[0036] The remainder of the immobilized buffered powder catalyst
(26.30 g) was loaded into a reactor tube. The reactor was run with
a flow rate of 1 ml/min, 40.degree. C., 20 bar, 20 wt % propene in
pentane feed. Six samples were taken, each containing 94-96%
dimers. Two cooled samples (dry ice, acetone+isopropanol) were
taken revealing conversions of about 58% after 6 hours and about
14% after 12 hours. The peak intensities of the fractions, which
were taken without cooling, showing conversion at 3 hours, 4 hours
and 5 hours, respectively, are not shown, but available on
request.
[0037] In another embodiment of the invention, alpha olefins are
homogenously dimerized using organometallic complexes with selected
co-catalysts. Specifically, oganometallic complexes of the form
shown above may be mixed with one or more co-catalysts selected
from the group of methylaluminoxane (MAO) and
B(C.sub.6F.sub.5).sub.3. The methylaluminoxane may be used in
different ratios vis a vis the organometallic catalyst, ranging
from about 100:1 to about 1000:1 co-catalyst:catalyst. Most
preferably, MAO is used as a co-catalyst in a ratio between about
250:1 to about 750:1 co-catalyst:catalyst.
[0038] For the homogenous catalyzed reactions MAO, AlCl.sub.3,
AlR.sub.3, AlR.sub.2Cl, AlBu/AlCl.sub.3, AlR.sub.3/AlCl.sub.3,
AlR.sub.2Cl/AlRCl.sub.2, where R=alkyl, aryl, alkenyl, alkynyl and
so on are used. Additives such as but not limited to phosphoranes
and amines may also be used. Without being bound by any particular
theory, it is thought that by adding MAO, the cocatalyst activates
the organometallic compound by generating a free coordination
center.
[0039] For the heterogeneous catalyzed reaction the homogeneous
activated complex is heterogenized on support material such as but
not limited to silica gels, MgO, Al.sub.2O.sub.3, and such.
Therefore the catalyst is stirred together with the support for 20
minutes in a suitable solvent (for example, toluene) and can be
used in a fixed bed reactor after removing the solvent.
Example 2
[0040] Preparation of the Ligand (Equation (3) Below):
[0041] To a solution of 1.5 g (7 mmol) of p-iodo-aniline and 0.5 g
(3 mmol) of 2,6-diacetylpyridine in 25 ml of toluene, 0.5 g of
silica-alumina catalyst and 5 g molecular sieve were added and
stirred for 24 hours at 50.degree. C. The cold solution was
filtered over sodiumsulfate and washed several times with toluene.
The solvent was removed in vacuo.
##STR00007##
[0042] Preparation of the Complex:
[0043] To 0.2 g (0.4 mmol) of p-iodo-bis(imino)pyridine in 30 ml of
n-butanole, 57 mg (0.4 mol) of FeCl.sub.3 were added and stirred
for two hours at room temperature and filtered. The precipitate was
washed with pentane and dried in vacuo.
[0044] Preparation of the Catalyst:
[0045] 10 mg of di-iodo-bis(imino)pyridine-Fe(III) complex was
mixed with 4.2 ml MAO (10% in toluene, Fe:Al=1:500), 20 ml of
1-hexene were added and the mixture stirred for five hours at
4.degree. C.
[0046] Without being bound by any particular theory, the
dimerization of alpha-hexene may occur as illustrated in equation
(4) below:
##STR00008##
[0047] The reaction products depend on 1,2- or 2,1-insertion and
are able to isomerize. FIG. 1 illustrates a GC spectra of the
reaction products after five hours. From 29.9-33.2 min dodecenes
are detected, octadecenes are detected from 34.0-34.8 min and
higher oligomers are detected after 36 minutes. Not shown, but
abailable on request, are additional data for hexene
dimerization.
[0048] In some embodiments of the invention, the organometallic
catalyst is immobilized on one or more supports selected from the
group consisting of silica, zeolite and partially hydrolyzed
trimethylaluminum ("PHT").
Example 3
[0049] General Synthesis Procedure for the Silicagel/PHT Catalyst
System:
[0050] At room temperature, 30 ml of a 2.0M trimethylaluminum
solution in toluene were added to a suspension of 2.0 g calcined
silica gel in 100 ml toluene. 0.75 ml water was bubbled through the
suspension as a moist argon flow. Thereupon, the reaction mixture
heated itself to 60.degree. C. After 10 min, the suspension became
suddenly highly viscous. After cooling to room temperature, the
mixture was stirred vigorously for 2 hours. 0.23 mmol of the
catalyst precursor were added as solids and stirred for 5 min. Then
the mixture was filtered and the solution dried in vacuo. The
filtrate was colorless and contained no organic or inorganic
components besides the solvent. Yields of the catalyst: 5.40 g
(>95% calculated on aluminum content) of a powder colored
according to the catalyst precursor.
Example 4
[0051] General Synthesis Procedure for the Prepolymerized Silica
Gel/PHT Catalyst System:
[0052] The synthesis was analogous to Example 3. However, an
ethylene pressure of 1.0 bar was applied for 15 min at 25.degree.
C. prior to the filtration of the catalyst suspension. The reaction
vessel was saturated with hydrogen at ambient pressure prior to the
addition of ethylene. During prepolymerization, the color of the
reaction mixture changed to dark-brown and it became highly
viscous. After filtration and drying in vacuo, 5.60 g of a slightly
colored powder were obtained. The polyethylene portion of the
catalyst was obtained from the difference between the weight before
and after prepolymerization.
* * * * *