PROCESS FOR MAKING AN ALPHA-OLEFIN OLIGOMER PRODUCT

Abstract: C₈₋₁₄ α-olefins are oligomerized to a oligomer mixture containing a high content of tetramer by feeding the α-olefin to a reaction vessel at a controlled rate over an extended period and in the presence of BF₃ and a promoter such as an alcohol.

Description: Alpha-olefin oligomers and their use as hydraulic fluids and synthetic lubricants (synlubes) are well known. U. S. 2,937,129 reports the oligomerization of C₅₋₁₄ α-olefins using a dialkyl peroxide catalyst to make a synlube. U. S. 3,113,167 describes an α-olefin oligomer process using a titanium halide and an aluminum compound. The preferred catalysts for making α-olefin oligomers are Friedel Crafts metal halides such as BF₃, U. S. 3,149,178. Optimum properties are obtained starting with 1-decene although mixtures of α-olefins have been used, U. S. 3,330,883. The preferred Friedel Crafts catalyst is BF₃. Pure BF₃ is not an effective oligomerization catalyst. A small amount of polar compound is necessary as a promoter. U. S. 3,382,291 describes the use of alcohol promoters such as decanol. Other reported promoters are modenite (hydrogen form), water, phosphoric acid, fatty acids (e.g., valeric acid), ketones, organic esters, ethers, polyhydric alcohols, silica gel and the like. Synlubes are generally classified by their viscosity at 100°C. The viscosities most often referred to are 4, 6 and 8 centistokes (cs). Oligomers made from α-olefins are mixtures of dimer, trimer, tetramer, pentamer and small amounts of higher oligomers. Dimers are too volatile for most uses and are usually removed by distillation together with any unreacted monomer. In the case of 1-decene, 4 cs fluids are mainly trimer with a small amount of tetramer. The 4 cs synlubes can be merely distilled from the oligomer mixture leaving a more viscous residue that can be used to make 6 and 8 cs fluids. If demand for 6 and 8 cs fluids becomes large, the above procedure can be impractical because it could leave a manufacturer with an excess amount of trimer. Therefore a need exists for a procedure for making 6 and 8 cs fluids directly without the need for distilling out excessive amounts of trimer. Pratt, U. S. 4,587,368, describes a process that results in increased tetramers and pentamers. Pratt achieves this in a 2-stage process by first conducting a conventional batch oligomerization procedure using a BF₃-propanol-hexanol catalyst until the mixture contains only 3-5 weight percent monomer. Then, in the second stage, additional α-olefin is added over an extended period to consume part of the trimer formed in the first stage thus increasing the amount of tetramer. US-A- 4,434,309 discloses a one step batch process for oligomerizing monoolefin with a catalyst comprising BF₃ in the presence of a promoter selected from alcohls and carboxylic acids. However, when using an alcohol promoter only 1.6% tetramer was obtained according to this process. It has now been discovered that oligomers having increased amounts of tetramer and higher components can be made in a single-stage procedure by merely feeding an α-olefin namely 1-decene over and extended period to a reaction vessel in the presence of BF₃ and n-butanol as a promoter. Thus, the invention concerns a one-step batch process for making an α-olefin oligomer product containing at least 40 weight percent tetramer and a tetramer to trimer ratio of at least 1.5, said process comprising: (A) placing an initial amount of 0.1-1.0 mole parts of 1-decene which is substantially free of promoted BF₃, catalyst in a reaction vessel and (B) co-feeding at least 0.5 additional mole parts of said 1-decene and a BF₃ promoter amount of n-butanol to said reaction vessel over a period of at least one-half hour and under BF₃ pressure while maintaining the reaction temperature at 20-50°C, said co-feeding being commenced at a time when said initial amount of 1-decene is still at least 75 weight percent monomer. The present process results in an α-olefin oligomer product having an increased tetramer content compared to the tetramer content one would obtain with the same α-olefin, BF₃ catalyst, promoter and reaction temperature but conducted by charging all of the α-olefin prior to or at the start of the oligomerization. The process is conducted in the presence of BF₃ and n-butanol as a promoter. The process is conducted under BF₃ pressure. A useful pressure is 0.068-6.89 bar (1-100 psig), preferably 0.34-3.4 bar (5-50 psig) and more preferably 0.68-1.36 bar (10-20 psig). The BF₃ pressure is applied at the start of or Just prior to the additional 1-decene feed. Operating in this manner makes it unnecessary to add BF₃ to the reaction mixture through any other source such as by pre-saturating the 1-decene or a portion of the 1-decene with BF₃. Hence a substantially BF₃-free 1-decene is used. The promoter used is n-butanol. The amount of promoter should be an amount that causes the BF₃ to act as an oligomerization catalyst. This is referred to as a promoter amount. A useful range is 0.1-2.0 weight percent of the 1-decene. The promoter is added to the reaction vessel over an extended period of time such that the concentration of the promoter in the liquid phase remains in the desired range. The promoter can be added in spaced increments or can be continuously fed over a prolonged period. This will generally be substantially the same as the extended period of 1-decene feed, although this is not essential. The prolonged period of promoter addition is at least one-half hour and more preferably an hour or longer. There is no critical upper limit to the promoter feed time. The length of the prolonged period of promoter feed depends upon the length of the extended period of 1-decene feed. The time range for feeding the promoter is 0.5 up to 24 hours. A preferred time range is 0.5 up to the 1-decene feed time and, more preferably, one hour up to the 1-decene feed time. The promoter is preferably fed to the reaction mixture in a continuous manner throughout the promoter feed period. Optionally the promoter can be added in a series of incremental feeds. For example a portion of the promoter can be fed every 15 minutes or so to maintain the promoter concentration in the desired 0.1-2.0 weight percent range. A portion of 0.1-1.0 mole parts of 1-decene is initially charged at the start of the process. This enables the reaction vessel agitator to engage a liquid phase. The process is carried out by injecting BF₃ and promoter into the reaction vessel and gradually feeding 1-decene. The controlled feed of the 1-decene is commenced before the initial 1-decene charge has oligomerized to any substantial extent. This means at least 75 weight percent and more preferably at least 90 weight percent of any initial 1-decene charge is still monomer when the controlled feed of the 1-decene over an extended period is commenced. The amount of 1-decene fed to the reaction vessel at a controlled rate over an extended period is at least 0.5 mole parts, preferably 0.5-100 mole parts and more preferably 0.5-10 mole parts by weight. This establishes a weight ratio between initial alpha-olefin charge and the amount of alpha-olefin fed over an extended period. This weight ratio is 0.1-1.0:0.5-100 and more preferably 0.25-0.8:0.5-10.0. The time of addition of the 1-decene at a controlled rate is an extended period. This means it takes place over a period of time rather than all at once. The extended period should be at least one-half hour and preferably at least one hour. There is no critical upper limit to the 1-decene extended feed time. As a practical matter there is little advantage in an extended feed time in excess of 24 hours. A more preferred extended 1-decene feed period is 0.5-12 hours and still more preferably 1.0-8 hours. The 1-decene is fed at a controlled rate. This means the process includes some means to control the rate of 1-decene feed such that it is not all charged to the reaction vessel prior to the start of the reaction. The feed control means can be a valve to adjust 1-decene feed from a head tank or can be a conventional flow meter. The 1-decene feed is preferably continuous over the entire extended feed period but can be conducted in a series of incremental feed periods. For example an increment of the 1-decene can be added every 15 minutes until the total 1-decene has been added. The preferred reaction temperature is 20-50°C and more preferably 25-40°C. Superior results have been achieved at about 30°C. Lower temperatures will increase the amount of higher oligomers but at the cost of a slower reaction rate. High temperatures give a fast reaction rate but increased yield of dimer. The following examples show a conventional process for making α-olefin oligomers compared to the present process for making such oligomers. Example 1 (Comparative Example) This example shows a comparative procedure for making an α-olefin oligomer product which uses promoter feed over a prolonged period but charges all of the α-olefin at the start. In a reaction vessel was placed 2000 g of 1-decene. The vessel was sealed and pressurized to 1.378 bar (20 psig) with BF₃. While stirring, 12 g of n-butanol (0.6 weight percent of 1-decene) was continuously fed to the reaction mixture over a one-hour period while stirring at 30°C. stirring was continued for 1.5 hours at which time the mixture was washed with 30 weight percent aqueous caustic to remove BF₃ and n-butanol. The product was then analyzed by gas chromatograph (GC) which gave the results shown in Table I. Example 2 This example shows how the present process can be conducted. In a reaction vessel was placed 1000 g of 1-decene. The vessel was pressurized to 1.37 bar (20 psig) with BF₃. While stirring at 30°C, 800 g of additional 1-decene containing 0.6 weight percent n-butanol was continuously fed to the reactor over a 2.6 hour period. Six grams of n-butanol was continuously fed to the reactor over a one-hour period. After completion of the 1-decene programmed feed, stirring was continued at 30°C for 15 minutes. The reaction mixture was then washed with aqueous caustic to remove BF₃ and n-butanol and analyzed by GC. Results are shown in Table I. Component Weight Percent Example 1 Example 2 monomer 0.8 0.8 dimer 4.7 2.4 trimer 54.2 25.7 tetramer 26.0 49.4 pentamer 11.1 17.4 hexamer 3.1 4.2 These results show that the present one-step programmed feed process results in a sharp increase in tetramer and higher oligomers. Decene oligomers containing at least 40 weight percent tetramer and having a tetramer/trimer ratio of at least 1.5 are readily obtained. After distillation to remove the monomer and dimer and optionally some of the trimer, the product can be catalytically hydrogenated to obtain a 6 or 8 cs synlube.

Claims: A one-step batch process for making an α-olefin oligomer product containing at least 40 weight percent tetramer and a tetramer to trimer ratio of at least 1.5, said process comprising: (A) placing an initial amount of 0.1-1.0 mole parts of 1-decene which is substantially free of promoted BF₃ catalyst in a reaction vessel and (B) co-feeding at least 0.5 additional mole parts of said 1-decene and a BF₃ promoter amount of n-butanol to said reaction vessel over a period of at least one-half hour and under BF₃ pressure while maintaining the reaction temperature at 20-50°C, said co-feeding being commenced at a time when said initial amount of 1-decene is still at least 75 weight percent monomer. A process of Claim 1 wherein the process is conducted under a BF₃ pressure of 0.068 to 6.89 bar (1-100 psig). A process of Claims 1 or 2, wherein said reaction temperature is 25-40°C. A process of any of Claims 1 to 3, wherein said n-butanol is added to said reaction vessel over a period of it least one-half hour such that the concentration of the n-butanol in the liquid phase remains in a range of 0.1-2.0 weight percent. A process of Claim 4 wherein said additional 1-decene is added to said reaction vessel over a period of at least one hour. A process of Claim 5 wherein said n-butanol is added to said reaction vessel over a period of at least one hour.

Inventors: DILEO, THOMAS JOSEPH, LIN, RONNY WEN-LONG, LYNCH, MATTHEW JOSEPH, NELSON, MARSHALL BUDD
Applicants: ETHYL CORPORATION
Application year: 1989
Main classification: C07C2
IPC codes: C07C2