CA2126388C

CA2126388C - Olefin oligomerization process

Info

Publication number: CA2126388C
Application number: CA002126388A
Authority: CA
Inventors: Kevin J. Theriot
Original assignee: BP Corp North America Inc
Current assignee: Ineos USA LLC
Priority date: 1993-07-12
Filing date: 1994-06-21
Publication date: 2006-01-24
Anticipated expiration: 2014-06-21
Also published as: US5396013A; CA2126388A1; JPH07173083A; JP3843140B2; DE69412937T2; DE69412937D1; EP0634381B1; ZA945054B; EP0634381A1

Abstract

A process for making an .alpha.-olefin oligomer comprises contacting a C6 to C20 .alpha.-olefin monomer with a catalyst which includes boron trifluoride, a protic promotor and a polyether.

Description

OLEFIN OLIGOMERIZATION PROCESS
This invention relates generally to the preparation of alpha-olefin oligomers which are useful as synthetic lubricants and functional fluids and more particularly to a BF3-promoter catalyst system which uses a polyether modifier to control the oligomer product distribution and provide higher percentages of lower oligomers.
Alpha-olefin oligomers and their use as synthetic lubricants ("synlubes") are well-known. The oligomers are usually hydrogenated in order to improve their stability. Early reports of such synlubes are in Seger et al. U.S. Pat. No.

2,500,161 1o and Garwood U.S. Pat. No. 2,500,163. U.S. Pat. No. 2,766,312 describes the oligomerization of a-olefins in a Group IV metal oxide bed using a BF3-protic promoter catalyst. Promoters include water, carboxylic acid, alkyl halides, alcohols and ethers. U.S. Pat. No. 2,806,072 discloses the dimerization of C6-C,2 poly-propylenes using a preformed BF3-dialkylether catalyst. U.S. Pat. No.

3,382,291 describes the oligomerization of olefins using BF3-promoter catalyst complexes which include acid anhydrides, esters, ketones and aldehydes. U.S. Pat. No.

4,172,855 describes BF3-promoter catalysts for grafting a second a-olefin onto C6-C,2 a-olefin dimer to form a low volatility lubricating oil. The promoters include glycol ethers such as ethylene glycol monomethyl ether, propylene glycol monoethyl ether, and di-e o isobutyl ether.
The particular application for which the oligomer oils are used depends upon their viscosity, with viscosities of about 2-10 cSt at 100°C being preferred for general lubricating oil applications. These materials are mixtures of different percentages of dimer, trimer, tetramer, pentamer and higher oligomers, which olig-2 5 omers are produced in different proportions in the oligomerization process. In order to increase the viscosity, processes are used which either produce more of the higher oligomers or some of the lower oligomers are removed such as by distillation.
Most CASE PA-6788 ~ 12 ~ 3 8 8 lower viscosity dimer products are obtained as by-products of the production of higher viscosity synthetic oils. Due to the increasing use of dimers in applications such as low temperature lubricants and drilling fluids, methods for their preferential produc-tion are of interest. It is known that higher temperatures favor dimer production, but such higher temperatures can cause corrosion of production equipment. U.S.
Pat. No.

5,068,487 discloses a process for making predominantly dimers and trimers of a-olefins using an alcohol alkoxylate promoted BF3 catalyst. U.S. Pat. No.
5,191,140 discloses a process for making a-olefin oligomers which uses BF3 promoted by at least two of water, alcohols and anhydrides to peak the reaction at lower molecular 1 o weight product.
The discovery has now been made that polyethers will moderate BF3 catalyzed oligomerizations to provide either predominantly dimer or trimer containing oligomers.
In accordance with this invention there is provided a process for making an a-olefin oligomer which comprises contacting an a-olefin monomer which contains from about 6 to 20 carbon atoms with a catalyst comprising boron trifluoride, a protic promotor and a polyether.
The olefins used in making the oligomers are predominantly (at least SO
mole percent) C6 to CZO straight chain monoolefinically unsaturated hydrocarbons in 2 0 which the olefinic unsaturation occurs at the 1- or alpha-position of the straight carbon chain. Such alpha-olefins are commercially available and can be made by the thermal cracking of paraffinic hydrocarbons or by the well-known Ziegler ethylene chain growth process. Individual olefins may be used as well as mixtures of such olefins.
Examples of such olefins are 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-dodecene, 1-hexadecene and 1-tetradecene. The more preferred normal-alpha-olefin monomers are those containing about 8-14 carbon atoms. The most preferred olefin monomer is 1-decene.

CASE PA-6788 ~ 12 6 3 ~ 8 The olefin monomers can also contain minor amounts of up to about 50, and usually less than 25 mole percent, of internal olefins and vinylidene olefins.
The olefin is contacted as known in the art with a catalytic amount of boron trifluoride which should be at least about 0.002 moles per mole of olefin.
Preferably, the reaction mixture is saturated with BF3. To be effective, the boron trifluoride is used in combination with a protic promoter such as water, carboxylic acids, mineral acids, alcohols, phenols, carboxylic acid esters and anhydrides, ketones and aldehydes. Preferred are water and C, to C24 alcohols and, more preferably, C, to C,2 alcohols (e.g. methanol, ethanol, n-propanol, isopropanol, n-butanol, to isobutanol, n-hexanol, 2-ethylhexanol, n-decanol, n-dodecanol, and the like). The amount of promotor should be an amount which is effective to cause the BF3 to act as an oligomerization catalyst, for example, from about 0.001 to 0.040 moles per mole of a-olefin monomers. In general, the BF3 is used in molar excess to the amount of promotor. This can be accomplished by using a closed reactor and a small BF3 pressure over the reaction mixture. The promoter can be mixed with the olefin feed and the reaction can be carried out in a batch or continuous process at temperatures of about 0° to 200°C. and pressures ranging from atmospheric up to, for example, 1,000 psig. The reaction temperature will change the oligomer distribution with temperatures of about 45°C and above favoring the production of lower oligomers, 2o namely dimer. Preferred reaction temperatures and pressures are about 20° to 65°C.
and 5 to 100 psig.
Preferred polyether modifiers can be defined by the formula:
RO f C-Co-C-O ~mR
2 5 R' R' where each R is individually a hydrocarbyl group and, preferably, a C, to C3o alkyl or cycloalkyl group or a C6 to C3o aryl group; each R' is individually hydrogen or a hydrocarbyl group or, taken together, form a hydrocarbyl ring;
also, R and R' taken together can form a cyclic ether, when R' is a hydrocarbyl group, it is preferably a C, to C~ alkyl or cycloalkyl group or a C6 to C~
aryl group; n = 0, l, 2, or 3 and m = 1 to 8. Non-limiting examples of such poly-ethers include 1,2-dimethoxyethane, diethylene glycol diethyl ether, 1,2-diethoxy-ethane, triethylene glycol diethyl ether, 1,2-dimethoxypropane, 1,2-dirt~ethoxybenzene, 1,3-dimethoxycyclohexane, methyl tetrahydrofuryl ether, 1,3-io dimethoxybutane, 2,3-dimethoxybutane, and the like.
The polyether modifters are used in mole ratios of promotor to modifier which are selected to peak the oligomers at either dimer or trimer.
The ratios will vary somewhat depending upon the particular combination of promotor and polyether which are used. In general, there is a range of ratios of promotor to polyether which will peak dimer. Above and below such ratios, the product will peak at trimer. For example, when using a combination of n-butanol and 1,2-dimethoxyethane, mole ratios of alcohol to polyether of up to about 1 peaked trimer whereas ratios of about 1.3 to 6.5 peaked dimer. At ratios of above 6.5, trimer again became the predominant product. When diethylene glycol diethyl 2 o ether was used, a ratio of about 1 produced predominantly dimer. The ratio which will peak the process at dimer for each catalyst combination can be readily determined by running a few oligomerizations according to the procedures described in the following examples which are intended to illustrate, but not limit, the process of the invention.

In a preferred embodiment, the invention comprises a process for making an a-olefin comprising contacting an a-olefin monomer containing from about 6 to 20 carbon atoms with a catalyst comprising boron trifluoride, a protic promoter and a polyether wherein the polyether is 1,2-dimethoxyethane and the mole ratio of the protic promotor to the polyether is in the range of about 1 to 1 to about 6.5 to 1. In another preferred embodiment, the invention comprises a process for making an a-olefin comprising contacting an a-olefin monomer containing from about 6 to 20 carbon atoms with a catalyst comprising boron trifluoride, a protic promoter and a polyether wherein the polyether is diethylene glycol diethyl ether and the mole ratio of the protic promotor to the glycol diethylene ether is in the range of about 0.5 to 1 to about 4.0 to 1.
Examples 1 to 10 1-Decene, 1-butanol ( 1.0 mol % based on decene), and the appropriate amount of polyether (see Table I), were charged into the reactor which -4a-CASE PA-6788 2 i 2 fi 3 8 8 was then assembled and purged with Nz. The reactor contents were brought up to the appropriate reaction temperature by a heating coil circulating system. The stirred reactor was then pressurized with BF3 ( 10 psig) via a sparge tube located below the surface of the liquid. The reaction was stopped after 2 hours by venting the BF3 through a caustic scrubber and quenching the reactor contents with 5 aqueous NaOH. The oligomer content of the final product was then determined by GC.
Comparative examples were run with no ether modifier at temperatures of 45 and 25°C (Comparisons 1 and 2). A comparative example was 1o run using a monoether (Comparison 3). Without an ether modifier, the dimer content was only 17 % even at a reaction temperature of 45 ° C. Using a mono-ether (dibutyl ether) had little effect on the reaction. This illustrates the importance of using a polyether as the moderator.

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Claims

1. A process for making an .alpha.-olefin oligomer comprising reacting an .alpha.-olefin monomer containing from about 6 to 20 carbon atoms in the presence of a catalyst comprising, at least about 0.002 moles of boron trifluoride per mole of said monomer, from about 0.001 to 0.04 mole of a protic promoter per mole of said monomer, and a polyether in a mole ratio of promoter to polyether of from about 0.5 to 10, the mole ratio being selected so as to form predominantly the dimer or trimer oligomerizaton product.

2. The process of claim 1 wherein the mole ratio of protic promoter to polyether is selected such that the oligomer is predominantly dimer.

3. The process of claim 2 wherein the polyether is 1,2-dimethoxyethane and the mole ratio of protic promoter to polyether is from about 1 to about 6.5.

4. The process of claim 3 wherein the mole ratio of protic promoter to 1,2-dimethoxyethane is from about 1.3 to 4Ø

5. The process of claim 2 wherein the polyether is diethylene glycol diethyl ether and the mole ratio of protic promoter to diethylene glycol diethyl ether is from about 0.5 to 4Ø

6. The process of claim 1 wherein the mole ratio of protic promoter to polyether is selected such that the oligomer is predominantly trimer.

7. The process of claim 1 wherein the .alpha.-olefin is 1-decene.

8. The process of claim 1 wherein the polyether has the formula:

0 where each R is individually a C1 to C30 alkyl or cycloalkyl group or a C6 to C30 aryl group or taken with an R' forms a cyclic ether; each R' is individually hydrogen or a C1 to C30 alkyl or cycloalkyl group or a C6 to C30 aryl group or, taken together, form a hydrocarbyl ring; n = 0, 1, 2, or 3 and m = 1 to 8.