Oligomerization of alpha-olefin

Olefin oligomers are prepared by polymerizing one or a mixture of olefins, each of which has about 6 to 20 carbon atoms, in the presence of a catalyst prepared by reacting in an organic solvent an aluminum halide and from about 0.01 to 0.99 mole per mole of aluminum halide of a proton donor.

BACKGROUND 
This invention relates generally to the preparation of alpha-olefin 
oligomer oils having a high viscosity, and particularly to methods for 
preparing oligomer oils, which are useful in lubricants and functional 
fluids, by polymerizing an olefin having 6 or more carbon atoms in the 
presence of a catalyst prepared by reacting an aluminum halide such as 
AlCl.sub.3 with a proton source, such as an alcohol, in an organic 
solvent. 
Synthetic oils having high viscosities of about 30 centistokes or above at 
100.degree. C. have been prepared by using aluminum halide catalyst 
systems to oligomerize alpha-olefins having about 6 to 20 carbon atoms. 
Such oils possess a good stability to shearing, a low pour point, and a 
high viscosity index. A number of aluminum halide catalyst systems have 
been disclosed for this purpose. U.S. Pat. No. 3,637,503 discloses a 
lubricating oil composition containing a viscosity index improving amount 
of a polymer obtained by polymerizing a normal alphaolefin having from 4 
to 16 carbon atoms in the presence of a mixture of aluminum chloride and a 
nonpolymerizing hydrocarbon diluent. The mixture is preferably contacted 
with gaseous hydrogen chloride as a promoter by bubbling the gas through 
the solvent containing the aluminum chloride prior to introducing the 
olefin monomer. We have found that the viscosity of the product polyolefin 
oil is very sensitive to the ratio of hydrogen chloride to aluminum 
chloride. It would be difficult to control this ratio to the extent 
necessary to provide oligomer products of a selected viscosity using 
gaseous hydrogen chloride according to the process of U.S. Pat. No. 
3,637,503. U.S. Pat. No. 4,107,080 discloses the preparation of an 
oligomerization catalyst suitable for the preparation of low viscosity 
olefin polymers in which aluminum halide is contacted with a fatty acid 
with complete removal of the hydrogen halide which is generated. U.S. Pat. 
No. 4,006,199 describes a catalyst system using aluminum halides in 
conjunction with dicarbonyl compounds to give olefin oligomers having a 
kinematic viscosity between 500-1500 cSt at 37.6.degree. C. U.S. Pat. No. 
4,219,691 discloses the preparation of olefin oligomer in the presence of 
an aluminum halide and a secondary or tertiary alcohol. The optional use 
of a solvent in the oligomerization reaction for reducing the viscosity 
increase and easy control of the reaction temperature is suggested. 
Comparative i0 examples using primary alcohols gave relatively low 
viscosity products e.g. less than 500 centistokes at 37.8.degree. C. U.S. 
Pat. No. 2,631,176 discloses the preparation of high viscosity olefin 
polymers using a Friedel-Crafts catalyst in the presence of an oxygenated 
compound such as an aliphatic alcohol. The preparation of a polymer of 
1-deoene in the presence of n-heptane, AlCl.sub.3 and about 2 moles of 
methanol per mole of AlCl.sub.3 (excess methanol) is described. The 
polymer had a 210.degree. F. viscosity of 232 SUS or only about 50 
centistokes. We have discovered a process which can provide, with good 
selectivity, very high viscosity olefin oligomer fluids using a catalyst 
composition, which includes aluminum halide in combination with primary 
(as well as secondary and tertiary) alcohols or other proton donor 
compounds, by preparing the catalyst composition in the presence of an 
organic solvent using an excess of aluminum halide. 
BRIEF SUMMARY 
In accordance with this invention there is provided a process for preparing 
an olefin oligomer comprising polymerizing one or a mixture of olefins, 
each of which has about 6 to 20 carbon atoms, in the presence of a 
catalyst prepared by reacting, in an organic solvent, an aluminum halide 
with from about 0.01 to 0.99 mole per mole of aluminum halide of a proton 
source. 
Also provided is a catalyst composition prepared by reacting, in an organic 
solvent, an aluminum halide with from about 0.01 to 0.99 mole per mole of 
aluminum halide of a proton source so as to generate hydrogen halide which 
is substantially completely absorbed in said solvent.

DETAILED DESCRIPTION 
The olefins used in the process of the invention are predominately (at 
least 50 mole percent) C.sub.6 to C.sub.20 straight chain monoolefinically 
unsaturated hydrocarbons in which the olefinic unsaturation occurs in the 
1- or alpha-position. Such olefins are commercially available and can be 
made by the thermal cracking of paraffinic hydrocarbons or by the 
well-known Ziegler ethylene chain growth and displacement process using 
triethyl aluminum. Individual olefins may be used as well as mixtures of 
such olefins. Examples of such olefins are 1-hexene, 1-octene, 1-nonene, 
1-decene, 1-dodecene, 1-hexadecene and 1-tetradecene. The more preferred 
normal-alpha-olefin monomers are those containing about 8-12 carbon atoms. 
The most preferred olefin monomer is 1-decene. 
The olefin monomers can also contain amounts of up to a total of about 50 
but usually less that 25 mole percent of internal olefin and vinylidene 
olefin. 
The catalysts for use in the present invention include an aluminum halide 
e.g. aluminum fluoride, aluminum bromide, aluminum chloride, aluminum 
iodide and mixtures thereof. The preferred aluminum halide is aluminum 
chloride. The aluminum halide is reacted with from about 0.01 to 0.99 mole 
per mole of aluminum halide of a proton source and, preferably, about 0.05 
to 0.42 mole per mole of aluminum halide. It is necessary to carry out the 
reaction between the aluminum halide and the proton source in the presence 
of a nonpolymerizable organic solvent which acts to absorb the hydrogen 
halide which is generated. This permits the amount of hydrogen halide 
which is present in the oligomerization reaction to be reproducibly 
controlled to provide high viscosity oligomers products of from about 30 
to 400 cSt at 100.degree. C. by adjusting the proton source to aluminum 
halide ratio. 
Both organic and inorganic proton sources which will generate hydrogen 
halide in contact with the aluminum halide can be used. These are, for 
example, proton donor compounds such as water, alcohols, phenols, e.g. 
phenol, naphthol, etc., carboxylic acids, inorganic acids, e.g. 
phosphoric, sulfuric, nitric, etc., and the like. Preferred proton sources 
are primary, secondary, and tertiary aliphatic and alicyclic alcohols and 
alcohol alkoxylates such as, for example, methanol, ethanol, 
propanol-1,isopropanol, butanol-1, tert.-butyl alcohol, sec.-butyl 
alcohol, pentane-2-o1, pentanol-1, hexanol-1, hexane-2-o1, cyclohexanol, 
heptanol-1, heptane-2-o1, octanol-1, decanol-1, ethylene glycol, propylene 
glycol, glycerol and the like; and any mixtures thereof. Preferred alcohol 
alkoxylates can be represented by the formula: 
EQU RO(CHR'--CHR"(CHR"').sub.m --O).sub.n H 
where m is 0, 1 or 2, R is hydrocarbyl containing 1 to 24 carbon atoms, 
including mixtures thereof, R', R" and R'" are independently hydrogen, 
methyl, or ethyl, and when m is 2 each R'" can be different, and n 
averages 1 to 15. Examples of such alcohol alkoxylates include glycol 
ethers such as ethylene glycol monomethyl ether (2-methoxyethanol) and 
propylene glycol monoethyl ether and the like and ethoxylates derived from 
mixed C.sub.2 to C.sub.24, preferably C.sub.2 to C.sub.18 and most 
preferably C.sub.6 to C.sub.12 straight chain alcohols. Examples of 
carboxylic acids include propionic acid, butyric acid, trimethyl acetic 
acid, valeric acid, caproic acid, 2-ethyl hexanoic acid, caprilic acid, 
enanthic acid and the like. 
Suitable solvents for use in preparing the catalysts are aprotic organic 
liquids and include, for example, aliphatic, alicyclic and halogenated 
hydrocarbons. Such solvents are inert in that they do not participate in 
the oligomerization reaction. Preferred solvents are n-pentane, n-heptane, 
isooctane, cyclohexane, decane, methylene chloride, dichloroethane and the 
like. The amount of organic solvent used should be sufficient to absorb 
substantially all of the hydrogen halide which is generated. Generally 
amounts of from about 20 to 500 percent by volume of the amount of olefin 
to be oligomerized in the process are adequate. The amount of aluminum 
halide catalyst can vary and amounts of from about 1 to 10 weight percent 
based on the amount of olefin are preferred. The amount of hydrogen halide 
in the reaction system is an important factor in determining the viscosity 
of the oligomer and in achieving high viscosity products. The viscosity is 
readily controlled according to the process of the invention by selecting 
the amount of proton source which is used to react with the aluminum 
halide in the solvent absorbent and thus generate the desired amount of 
hydrogen halide. 
The reaction can be carried out by forming a slurry of the aluminum halide 
in the solvent absorbent, adding the proton donor co-catalyst and then 
feeding the olefin to a reactor which contains the catalyst system over a 
period of about 1 to 6 hours. The reaction temperatures will generally 
range from about 0.degree. to 100.degree. C. with the viscosity of the 
product decreasing somewhat with increasing temperature. 
The invention is further illustrated by, but is not intended to be limited 
to, the following examples. 
EXAMPLE 1 
The reaction was carried out in a 500 ml five neck round bottom flask 
fitted with a mechanical stirrer, a solid addition funnel, a thermometer 
and CaCl.sub.2 guard tube, a gas inlet tube and an addition funnel. The 
system was purged with dry nitrogen and 4.0 grams of aluminum chloride (4 
weight percent of 1-decene) and 135 mL of heptane were added with stirring 
to form an aluminum chloride slurry. Methoxyethanol 0.57 grams (0.57 
weight percent of 1-decene) was added to the slurry system using a syringe 
with a long needle submerged in the heptane. There was no gas evolution 
and 100 grams of 1-decene were then added over a period of 4 hours. The 
temperature was maintained between 25.degree.-30.degree. C. with an ice 
water bath. At the end of the reaction, the reaction mixture was poured 
into 200 mL of a 50:50 mixture of heptane and water with vigorous 
stirring. The heptane layer was then separated and washed with water 
(100/mL). Drying (MgSO.sub.4), filtration and the removal of heptane gave 
a viscous oil. Flashing at 150.degree. C./0.5 mm afforded the final 
product (96% conversion) which had a viscosity at 100.degree. C. of 86.4 
cSt. As a comparison, the procedure was repeated except that the 
methoxyethanol was added to dry aluminum chloride in the flask with 
evolution of HCl. The HCl was driven out by dry nitrogen before adding the 
1-decene. The 1-decene was then added in heptane (1:1 volume). The product 
had a 100.degree. C. viscosity of 63.3 cSt which was only slightly higher 
than the 54.1 cSt product viscosity achieved in the absence of solvent 
using the same catalyst and co-catalyst concentrations. 
EXAMPLES 2-6 
The procedure according to Example 1 was carried out at 25.degree. C. with 
a 1:1 vol. ratio of 1-decene/n-heptane for 4 hours using 1-propanol at the 
catalyst compositions and concentrations shown in Table I The kinematic 
viscosities (in centistokes) and viscosity indexes (VI) are also reported 
in the Table. 
TABLE I 
______________________________________ 
Exam- AlCl.sub.3 Alcohol Viscosity, cSt 
ple Conc. (Wt. %) 
Conc. (Wt %) 
100.degree. C. 
40.degree. C. 
VI 
______________________________________ 
2 1 0.18 53.6 561 158 
3 2 0.18 64.6 715 161 
4 3 0.18 79 885 169 
5 4 0.18 84.4 961 170 
6 6 0.18 88.4 1020 171 
______________________________________ 
The results indicate that increasing the AlCl.sub.3 concentration at a 
constant alcohol concentration produces a moderate increase in product 
viscosity. 
EXAMPLES 7-14 
The procedure according to Example I was carried out at 50.degree. C. with 
a 1:1 volume ratio of 1-decene/n-heptane for four hours using aluminum 
chloride at 3 weight percent with varying amounts of 1-octanol. The 
results are reported in Table II. 
TABLE II 
______________________________________ 
AlCl.sub.3 
Alcohol 
Exam- Conc. Conc. Conver- 
KV100.degree. C. 
ple (Wt. %) (Wt. %) sion (%) 
(cSt) 
______________________________________ 
7 3 0.15 92 39.8 
8 3 0.20 96 45.5 
9 3 0.46 95 75.3 
10 3 0.56 95 87.0 
11 3 0.70 94 101.0 
12 3 0.72 94 86.9 
13 3 0.74 93 77.5 
14 3 0.83 95 75.0 
______________________________________ 
The results indicate that at a constant AlCl.sub.3 concentration the 
product viscosity (cSt) was increased by increasing the alcohol 
concentration and then leveled off and declined after a certain point. 
The procedure according to Example 1 was carried out at 25.degree. C with a 
1:1 volume ratio of 1-decene/n-heptane for 4 hours using aluminum chloride 
at 4 weight percent and 1.25 mol percent of the different alcohols The 
results are reported in Table III. 
TABLE III 
______________________________________ 
Exam- 100.degree. C. Vis. 
40.degree. C. Vis. 
ple ROH (cSt) (cSt) VI 
______________________________________ 
15 MeOH 359 4610 235 
16 PrOH 302 3890 224 
17 BuOH 214 2780 204 
18 n-Decanol 165 2140 191 
______________________________________ 
The results indicate that the product viscosity decreased with increased 
molecular weight of the alcohol. 
EXAMPLES 19-21 
The procedure according to Example 1 was carried out at 25.degree. C. with 
varying ratios of n-heptane solvent at 3 weight percent AlCl.sub.3 /0.20 
weight percent of 1-propanol for 4 hours. The results are reported in 
Table IV. 
TABLE IV 
______________________________________ 
Exam- Sol:decene 
100.degree. C. Vis. 
40.degree. C. Vis. 
ple Vol. cSt cSt VI 
______________________________________ 
19 1:1 79 885 169 
20 1:2 68 732 167 
21 1:4 72 786 167 
______________________________________ 
EXAMPLE 22 
Example 19 was repeated at 50.degree. C. and the product had a 100.degree. 
C. viscosity of 63 cSt.