PROCESS FOR THE PREPARATION OF HYDROGENATED CO-OLIGOMERS

Abstract: Higher viscosity index lubricant products are obtained at high yield by catalytically reacting branched internal olefinic oligomers with alpha olefins under oligomerization conditions.

Description: This application is directed to a composition comprising the oligomerization product of branched internal olefins or blends thereof with alpha olefins to produced improve synthetic lubricants. Synthetic hydrocarbon lubricants obtained from Friedel-Crafts catalyzed oligomerization of alpha-olefins that are known: U.S. Patent No. 4,469,912. Oligomerization of alpha olefins such as 1-decene using boron trifluoride plus promotor are described in for example U.S. Patent Nos. 3,149,178, 3,763,244, 3,780,128 and 4,469,912. U.S. Patent No. 4,463,201 discloses synthetic lubricating oils prepared by copolymerizing certain olefinic monomers and a third alpha olefin and thereafter dewaxing the polymerization product via a urea addition process. This invention is directed to a process of making improved synthetic lubricants comprising reacting branched internal olefins with added alpha olefin to produce synthetic lube-range product in increased yield, higher viscosity index (VI) and high quality. According to the present invention, high quality synthetic oils are provided by reacting an oligomer of a lightly branched internal olefin with an alpha olefin. In the context of this invention highly branched means greater than 2 branches per 12 carbon atoms and lightly branched means from 1 to 2 or less. Generally speaking, in the prior art this has meant 1 branch per 20 carbon atoms. The resulting lube-range product is formed in increased yield and of considerably higher VI than that produced by oligomerizing branched internal olefins alone. The higher yields and VI's could not be predicted from a combination of properties of the branched and alpha olefins. The branched internal olefinic oligomers are most advantageously reacted on a substantially equimolar basis with the added alpha olefin. Propylene is the preferred branched internal olefin oligomerized to provide C₁₀+ propylene oligomers, preferrably C₁₂+ oligomers. The branched internal olefinic oligomer may be prepared by any suitable method known in the art. Preferably it is prepared in the presence of an HZSM-5 type catalyst under known oligomerization conditions. Suitable alpha olefins include alpha olefins having from 6 to 20 carbon atoms such as 1-C₁₂, 1-C₁₄, and 1-C₁₆. The first stage or phase of the present process is carried out in the presence of a suitable zeolite catalyst, particularly a ZSM-5 type zeolite. Preferred for use herein include the crystalline aluminosilicate zeolites having a silica to alumina ratio of at least 12, a Constraint Index of 1 to 12 and acid cracking activity of 160 to 200. Representative of the ZSM-5 type zeolites are ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35 and ZSM-38 or their hydrogen forms. ZSM-5 is disclosed and claimed in U.S. Patent No. 3,702,886 and U.S. Patent No. Re. 29,948; ZSM-11 is disclosed and claimed in U.S. Patent No. 3,709,979. Also, see U.S. Patent No. 3,832,449 for ZSM-12; U.S. Patent No. 4,079,979. Also, see U.S. Patent No. 3,832,449 for ZSM-12; U.S. Patent No. 4,076,842 for ZSM-23; U.S. Patent No. 4,016,245 for ZSM-35 and U.S. Patent No. 4,046,839 for ZSM-38. A suitable catalyst is HZSM-5 zeolite with 35 wt% alumina binder in the form of cylindrical extrudates of 1 to 5 mm. These medium pore shape selective catalysts are sometimes known as porotectosilicates or "pentasil" catalysts. Especially preferred is ZSM-23 or its hydrogen form. These catalyst may be unmodified or surface modified. A phosphoric acid modified boron trifluoride catalyst is usually used in the process. However, a portion of the BF₃ may be complexed with water. The use of such catalyst with added alpha olefin results in increased process yields as high as 25% with VI's of 135+. When aqueous phosphoric acid is used as mentioned hereinabove the BF will be at least partially complexed with water. However, the phosphoric acid must comprise at least 50% or more of the aqueous acid solution. The phosphoric acid may be H₃PO₄, orthophosphoric or polyphosphoric acids. The reaction conditions are usually as follows: 10°C to 60°C temperature preferably 0 to 40°C; atmospheric to 793 kPa (100 psig) pressure, preferably slightly super atmospheric. The molar ratio of the first stage product to alpha olefin is 1:1. Generally speaking the oligomer, e.g. a C₁₂+ propylene oligomer is prepared first and thereafter blended and reacted with the added alpha olefin to provide improved lube-range products. Preferred reactants are (a) an alpha olefin 1-C₆ to 1-C₂₀ and more preferably 1-C₈ to 1-C₁₈ and (b) medium molecular weight lightly branched olefin product of a low molecular weight C₃ to C₈ olefin over ZSM-5 type zeolites (optionally surface modified) such as ZSM-5, ZSM-23 and ZSM-5 type zeolites in general or their hydrogen forms. By lightly branched olefin is meant olefins having 2 or less than 2, e.g., 1.1-2 branches per 12 methyl groups. The low molecular weight olefins are any suitable C₃ to C₈ olefin and preferably C₃ to C₄ olefins. Synthetic fluids produced by the process described herein are also highly useful as blending base stocks for high quality lubricants. The use of this process would allow refinery-produced propylene and alpha olefins to be of significant commericial value as an alternative to expensive polymer oils such as 1-decene polymer oil. Accordingly, the products of this invention can be directly used as lube range products or can be blended with any suitable lubricating media such as oils of lubricating viscosity including hydrocracked lubricating oils, hydraulic oils, automotive oils, gear oils, transmission fluids, waxes, greases and other forms of lubricant compositions selected from mineral oils, synthetic oils or mixtures thereof. Typical synthetic vehicles include polyisobutylene, polybutenes, hydrogenated polydecenes, polypropylene glycol, polyethylene glycol, trimethylol propane esters, neopentyl and pentaerythritol esters, di(2-ethyl hexyl) sebacate, di(2-ethylbenyl) adiptate, dibutyl phthalate, fluorocarbons, silicate esters, silanes, esters of phosphorus-containing acids liquid ureas, ferrocene derivatives, hydrogenated mineral oils, chain-type polyphenols, silozanes and silicones (polysiloxanes), alkyl-substituted diphenyl ethers typified by a butyl substituted bis-(p-phenoxy phenyl) ether, phenoxy phenylether, and the like. EXAMPLES The below described examples further illustrate the process of the invention but are not intended in any way to limit the scope of the invention. Example 1 A C₁₁-C₁₄ oligomer was prepared via HZSM-5 catalysis as follows: A propylene/butylene FCC off gas mixture was passed over a fixed bed of HZSM-5 catalyst at a feed rate of 0.6 grams per gram of catalyst per hour; pressure was 4240 kPa (600 psig); reactor inlet temperature was 232°C (450°F). The resulting mixed oligomers were distilled to give a C₁₁-C₁₄ cut. Example 2 The C₁₁-C₁₄ propylene/butylene oligomer prepared as in Example 1 was catalytically oligomerized using BF₃/H₃PO₄ catalyst as described below: 50 grams of the C₁₁-C₁₄ oligomer was charged to a flask. BF₃ was bubbled in subsurface. After BF₃ saturation had occurred, 0.4 gram of 70% H₃PO₄ was added. Reaction was continued for six hours at room temperature with continued addition of BF₃. The reaction mixture was quenched with water, dried, and distilled to remove lower boiling materials, giving a C₂₅+ oligomer yield of 30%. The viscosity index (VI) was 57. Example 3 Oligomerization, in the same fashion as Example 2, of a 67:33 (wt) blend of the C₁₁-C₁₄ propylene oligomer and 1-hexadecene (C₁₆) gave 61% yield of C₂₅+ oligomer with 117 VI. Based on a linear combination of properties, expected yield and VI for the blend are 50% yield, 91 VI. Thus, the added alpha-olefin enhances yield and VI in excess of that predicted. The added 1-hexadecene increases VI as if it had an effective blending VI of greater than 200 (actual 1-C₁₆= dimer/ trimer VI 161). See Table 1 for summary. Example 4 In the same manner as in Example 3, VI and yield were determined for C₂₅+ oligomer produced by BF₃/aq. H₃PO₄ catalyzed reaction of (a) a C₁₂+ propylene oligomer fraction prepared as in Example 1 using an amine-modified HZSM-23 catalyst prepared in accordance with Example 7 of U.S. Patent No. 4,160,788; (b) 1-hexadecene; (c) a 67:33 (wt) blend of (a) and (b). As in Example 3, the yield and VI of the blend were considerably increased, and were higher than calculated (see Table 2). Example 5 Addition of 15% 1-hexadecene to 85% of a C₁₂+ propylene oligomer (as in Example 4) increased oligomer product VI from 104 to 118 (113 calculated). Example 6 In the same manner as in Example 4, C₂₅+ oligomers were produced by BF₃/H₃ PO₄ catalyzed reaction of (a) a _ C₁₂ or _ C₁₅ lightly branched oligomer fraction prepared as in Example 1, using an amine-modified HZSM-23 catalyst in accordance with Example 7 of U.S. Patent No. 4, 160,788; and (6) various alpha-olefins (see Table 3) in varying amounts. As in Example 4, the viscosity index (VI) of the co-oligomer is considerably increased over the VI of the branched olefin homo-oligomer and is higher than expected from linear blending of branched olefin and alpha olefin homo-oligomers. This example illustrates: 1.1 to 2.0 branch ZSM-23 oligomer 1-C₁₀ -- 1-C₁₆ alpha olefin 15 to 50% alpha olefin uses BF₃ / H₃PO₄ catalyst Example 7 A mixture of 33 weight parts of a C₁₂+ ZSM-23 derived propylene oligomer with 1.6 methyl branches per C₁₂ prepared in accordance with Exmaple 6 was co-oligomerized with 67 weight parts 1-decene using the following procedure: A mixture of 670 grams 1-decene, 330 grams branched C₁₂+, and 7.2 grams of n-propanol was pumped into a reactor at 25 to 30°C and atmospheric pressure over four hours. A continuous subsurface BF₃ flow was maintained. After completion of the addition, the reactor was held at 20 to 25°C for an additional two hours. After caustic wash and stripping at low pressure, the fraction of the product boiling above 399°C (750°F) (84% yield) was hydrogenated at 185°C using a Ni-kieselguhr catalyst. Properties of the hydrogenated lube-range oligomer were: VI = 128; pour point -54°C (-65°F); kinematic viscosity at 100°C = 5.3 mm²/s. Example 8 In a manner similar to the previous example, a mixture of 75% 1-C₁₀, 25% 1.6 branch C₁₂+ ZSM-23 derived propylene oligomer was co-oligomer was co-oligomer was co-oligomerized. After removal of low-boiling components and hydrogenation, the properties of the lube-range oligomer were: VI = 133; pour point -54°C (-65°F); kinematic viscosity at 100°C = 5.4 mm²/s; flash point = 232°C (450°F). Examples 7 and 8 clearly illustrate that a high-quality lube base stock can be made by the specified co-oligomerization process. The present invention uses as the major component an inexpensive propylene oligomer instead of an alpha olefinic oligomer and surprisingly produces lube-range product in increased yield with significantly higher VI's than was predictable from a combination of properties of alpha olefins and branched internal olefins (propylene oligomers). Tables 1, 2, and 3 provide data clearly showing the improved yield and higher VI's obtainable by use of the novel process embodied herein.

Claims: 1. A process for preparing synthetic lube range products comprising (1) oligomerizing a low molecular weight C₃ to C₈ olefin or mixture thereof over a zeolite of the ZSM-5 family to form a medium molecular weight lightly branched olefinic product, (2) co-oligomerizing the product of (1) in substantially equimolar amounts with an alpha olefin or a mixture of alpha olefins in the presence of catalytic amounts of BF₃/aq H₃PO₄ in a suitable reaction medium and (3) thereafter removing low boiling materials from and hydrogenating the product of (2). 2. The process of claim 1 wherein the alpha-olefin is a C₃ to C₂₀ alpha olefin or mixture thereof. 3. The process of claim 1 or 2 wherein the alpha-olefin is a C₈ to C₁₈ alpha-olefin of mixture thereof. 4. The process of any of the preceding claims wherein the alpha-olefin is selected from 1-decene, 1-dodecene, 1-butyldecene, 1-hexadecene and mixtures thereof. 5. The process of any of the preceding claims wherein the low molecular weight olefin is a C₃ to C₄ olefin or mixture thereof. 6. The process of any one of the preceding claims wherein the lightly branched olefinic product is a C₁₁ to C₁₄ propylene/butylene oligomer. 7. The process of any of the preceding claims wherein the lightly branched olefinic product is a C₁₁ to C₁₄ propylene oligomer. 8. The process of any of the preceding claims wherein the olefinic product is a C₁₅ propylene oligomer. 9. The process of any of the preceding claims wherein the zeolite of the ZSM-5 family is selected from ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35 and ZSM-38 or their hydrogen forms. 10. The process of any of the preceding claims wherein the reaction is carried out at a temperature of from -10°C to 60°C and at pressure from atmospheric to 793 kPa, and a molar ratio of product of step (1) to added olefin of 1 to 1.

Inventors: YOUNG, LEWIS BREWSTER
Applicants: MOBIL OIL CORPORATION
Application year: 1989
Main classification: C10G69
IPC codes: C10N20, C10N70, C10G69, C10M105, C07C2, B01J29, C07B61, C10N60