178
Ind. Eng. Chem. Prod. Res. Dev. 1083, 22, 178-181
Numerous combinations of alkyl substituents can be made through the reaction between either a Grignard or organolithium reagent with an alkylchlorosilane. Pure monomolecular silahydrocarbons or mixtures of silahydrocarbons may be synthesized through variation of the stoichiometry of the reactants. The resulting silahydrocarbons are fluids having a variety of rheologic properties depending on whether the silahydrocarbon is monomolecular or a mixture of silahydrocarbons. In general, the best liquid range in the silahydrocarbons is obtained by the use of the mixed molecular structures. The thermal stability of the silahydrocarbons containing four normal alkyl substituents is excellent up to 370 O C (700 OF). By the addition of antiwear additives, e.g., tricresyl phosphate, and antioxidants, e.g., hindered phenols, formulated silahydrocarbons with excellent performance properties are obtained. The resulting formulated silahydrocarbons represent an improved class of fluids with excellent thermal and rheological properties which may be considered for
applications requiring unusual and severe environmental conditions. Registry No. n-C8H17Br,111-83-1;CH3Si(n-C&,,),, 3510-72-3; CH3SiC13,75-79-6; n-C9HlgBr, 693-58-3; n-CloHzlBr, 112-29-8; CH3Si(n-C12H25)(n-CBH17)z, 83094-42-2; n-C12Hz5Br,143-15-7; CH3Si(n-ClzHZ5)Cl2, 18407-07-3; CH3Si(n-CloH21)3, 18769-78-3; CH3Si(n-CgH19)3, 83094-38-6; CH3Si(n-C6H13)3, 3429-60-5; CH3Si(CH2CH(C2H,)C4H9)3, 83094-43-3.
Literature Cited Baum, G.; Tamborski, C. J. Chem. Eng. Data 1961, 6 , 142. Petrov, A. D.; Nironov, B. F.; Ponomorenko, V. A,; Chernyshev, E. A. "Synthesis of Organosilicon Monomers"; Consultants Bureau: New York, 1964. Rosenberg, H.; Groves, J. D.; Tambroskl, C. J. Org. Chem. 1960, 25, 243. Snyder, C. E., Jr.; Tamborski. C.; Gschwender, L. J.; Chen, G. J. "Development of High Temperature (-40 OC to 288 "C) Hydraulic Fluids for Advanced Aerospace Applications"; Presented at ASME/ASLE Lubricants Conference in San Francisco, CA, Aug 1960; Preprint No. 80-LCIC-1. Tamborski, C.; Rosenberg, H. J. Org. Chem. 1960, 25, 246.
Received f o r review May 17, 1982 Accepted September 7, 1982
Synthetic Lubricants: Star-Branched Oligomers via Metathesis/Dimerization of 1-0ctene and/or 1-Decene Wllllam T. Nelson' and Louis F. Heckelsberg Research and Development Department, Phllllps Petroleum Company, Bartlesvllle, Oklahoma 74004
A desirable molecular structure for a synthetic lubricant, as exemplified by poly(a-olefins), is the "star-branched" hydrocarbon having one or two alkyl groups of 6-10 carbons each attached near the center of a normal paraffin. Such a material can now be prepared by a novel two-step process in which l-octene and/or ldecene is first metathesized to a mixture of &-C18 internal olefins which is then dimerized to a lube oil range hydrocarbon intermediate. The lube oil range hydrocarbons have a star-branched configuration R',
,R3
c=c
where Rl-R, are alkyl groups each having 6-9 carbon atoms such that the molecule has a total of 28 to 36 carbon atoms. Hydrogenation of these olefinic dimers yields synthetic lube stocks with viscosity indices of 105-134 and pour points of -54 to -34 O C . The relationship of feed composition to lube stock properties will also be discussed.
Introduction Hydrocarbon synthetic lubricants are generally hydrogenated a-olefin oligomers or alkylated aromatic hydrocarbons. Of these two types, the poly(&-o1efin)'isthe more common. The desired structure in a poly(a-olefin) is one which Graessley (1977) has called a "star-branched oligomer", that is, a hydrocarbon molecule with one or two relatively long side chains attached somewhere near the middle. The principal isomer in 1-decene trimer, 9methyl-11-octylheneicosane (after hydrogenation), appears to be such a star-branched oligomer. Recent work, however, suggests that BF,-catalyzed oligomers contain more branching than would be predicted by the accepted carbonium ion mechanism (Shubkin et al., 1980). Metathesis (disproportionation) of olefins is a remarkably selective reaction for synthesizing unusual olefins (Banks, 1979). Thus, it was envisioned that 1-octene and
1-decene could be metathesized to a mixture of CI4, CI6, and CI8 internal olefins which in turn could be dimerized to C&% olefins having the star-branched structure. This carbon number range is most suitable as a base stock for an SAFC 1OW motor oil. The two-step generalized reaction for the synthesis of doubly branched star-branched oligomers is c=,c t
, =C=C
(1)
t Cn=Cn
Cn=C
c,=cn t
Cm-1
-
c,=cn
\=c
/
Cn
J
\
Cn-1
(2) Cm
where m = 7 or 9 and n = 7 or 9. Since the metathesis step
0196-4321/83/1222-0178$01.50/00 1983 American Chemical Society
Ind. Eng. Chem. Prod. Res. Dev., Vol. 22, No. 2, 1983 170
is an equilibrium step, unreacted 1-octene or 1-decene can be left in the product from the first step to co-dimerize with the internal olefins to give a singly branched oligomer cm=c* f
Cm-1
-
,Cn-j
(3 1 5
b/
VISCOSITY INDEX = 104 7 - 9 6 x 1O'Y' + 5 8 7 x 1O'Y'
100-
+
0 66Y
-30
Experimental Section A. Metathesis. 1-Octene and 1-decene (Aldrich) and their blends were metathesized in a static system over a rhenium-containing catalyst. The catalyst was pretreated with dry air at 500 "C for 3 h and cooled in helium. Approximately 600 g of helium-purged olefin was placed in a 2-L volumetric flask, previously baked and dried in a helium atmosphere. Approximately 25 g of catalyst was then added to the reaction flask. The flask was capped with a rubber septum through which a hypodermic needle was inserted to permit escape of byproduct ethylene. The flask was allowed to sit at rmm temperature. Periodic GC analyses showed that equilibrium was generally reached in 260-340 h. One 12-h continuous run was made in a fmed-bed reactor containing 100 mL (57.0 g) of commercial cobalt-molybdate catalyst. The catalyst was pretreated with 0.125 mequiv of KOH/g of catalyst to neutralize acid sites. The initial reactor temperature, 90 "C, was increased to 140 "C during the first 6 h of hydrocarbon feed and maintained at that temperature for the remainder of the run. The weight hourly space rate was 2.4 g of feed/g of catalystlh. Reactor pressure was sufficient to maintain liquid-phase conditions. The initial off-gas analyzed 94% ethylene/6% propylene, changing to 70% ethylene/30% propylene at 140 "C. During the last 6 h of the run, there was no change in off-gas composition. The products from all the metathesis runs were fractionated into C8, Clot and Cll+ fractions in a 2-ft plate column. The total products and the fractions were analyzed in a Hewlett-Packard 5840A gas chromatograph using Dexsil300 columns (l/8 X 72 in.) and FID detectors. B. Dimerization. The dimerization runs were carried out either in a stirred glass flask or in a Hastelloy B autoclave. The glass flask was equipped with a gas dispersion tube to introduce BF3 gas below the surface of the liquid. The flask was provided with a mercury manostat so that a positive pressure (about 75 torr) of BF3 could be maintained throughout the run. Ethanol or 1-propanol was used as a cocatalyst in all of the runs. n-Hexane or nheptane was used as a diluent in the flask runs. No diluent was used in the autoclave runs and, in these runs, the system was evacuated briefly to remove air prior to pressurizing the autoclave to about 30 psig with BF3. The olefins conversion was monitored by taking small samples for GC analysis. It was found that the reaction time could be cut from the 5-6 h experienced at 40-60 "C in glass to 1 h at 70-80 "C in the autoclave. At the conclusion of the dimerization run, the contenb of the flask (autoclave) were withdrawn and a catalyst phase separated. The catalyst phase comprised BF3, alcohol, and a small amount of olefin. The catalyst phase from one run could be used in subsequent runs provided the BF3 partial pressure was brought back up to 30 psig. The remaining hydrocarbon portion was washed with aqueous NH40H,dried with Linde 3A molecular sieve, and filtered. After removal of the solvent, the product was vacuum distilled, in a 12-in. vacuum-jacketed Vigreux column, into a light fraction (IBP to about 410 "C), a base
- -"A a
lb
io
do 310 io io $0 Eo Y = COMPOSITION OF FEED TO METATHESIS STEP, MOLE oh 1-DECENE IN 1-OCTENE
do
-60 1bO
Figure 1. Correlation of viscosity index and pour point of hydrogenated oil with composition of feed to metathesis step.
oil fraction (about 410 to 520 "C), and a heavy fraction (above about 520 "C). These temperatures have been corrected to 760 torr. The base oil fraction was hydrogenated using 0.2 g of palladium (10% on carbon) catalyst in an autoclave at a temperature of 160 "C and a hydrogen pressure of 300 psig (2.2 mPa). One hour was sufficient to remove traces of olefin observable in an infrared spectrum. The hydrogenated base oil and the fractions from the vacuum distillation were analyzed by GC. Viscosities, pour point, and infrared spectra were run on samples of the hydrogenated oil. Experimental Data The experimental data are presented in three tables and one figure. Table I shows the composition of feeds and products in the metathesis step. Table I1 contains data from olefin dimerization in glass equipment, and Table 111 contains data from olefin dimerization in an autoclave. Figure 1correlates the viscosity index and pour point of the hydrogenated oil with composition of the feed to the metathesis step. Discussion The data in Table I indicate that the metathesis reaction is a remarkably selective reaction. Pure 1-octene could be 75% converted over a rhenium-containing catalyst to higher molecular weight olefins, principally 7-tetradecene, with a weight selectivity of 76%. Similarly, 1-decenecould be 71% converted to 9-octadecene with a weight selectivity of 87%. These yields correspond to 86-96% of the theoretical yield of c14-c18 olefins. Equimolar blends of 1octene/l-decene gave 7-tetradecene, 7-hexadecene, and 9-octadecene in a mole ratio of 1:2:1. 'H and 13C NMR confirm that the double bond is centrally located in the C14 and C18 fractions. Other blends, 3:l and 1:3, of 1octene/l-decene were also metathesized. Products from the metathesis reaction were fractionated to remove unreacted 1-octene and 1-decene. In several runs, the unreacted 1-octene and/or 1-decenewas blended back in the Cll+ product to simulate a feed in which the unreacted light olefins had not been removed. These fractionated or reblended olefins were used as feedstocks for the dimerization reaction. Not all batches of the rhenium-containing catalyst had the same activity, since different batches gave conversions varying from 50 to 75%. Also different batches showed different olefin isomerization activity. Thus, the rhenium catalyst used in runs 1and 5 and cobalt-molybdate catalyst used in run 8 produced a wider spectrum of products with lower attendant selectivity to c13
