Kinetic Study on Microwave-Assisted Oligomerization of 1-Decene over a HY Catalyst

Abstract

A promising production route for a high-quality base stock for lubricants is the oligomerization of high molecular-weight olefins in a high energy efficiency system. Oligomerization of 1-decene (C10) was conducted in a microwave-assisted system over a HY zeolite catalyst at different reaction temperatures and times. Higher reaction temperature resulted in increasing formation of dimers and trimers. The oligomerization reaction yielded 80% conversion, 54.2% dimer product, 22.3% trimer product and 3.4% heavier product at 483 K for a reaction time of 3 h. The best fit kinetic model for the dimerization reaction was formulated from an assumption of no vacant reaction sites. For the trimerization reaction, a molecule of dimer (C20) formed on the active site, interacted with a molecule of 1-decene in the bulk solution to form a molecule of trimer (C30). Apparent activation energies for the dimerization and trimerization reactions were 70.8 ± 0.8 and 83.6 ± 0.9 kJ/mol, respectively. The C13-NMR spectrum indicated that the oligomer product contained a significant portion of highly branched hydrocarbons, causing a substantial reduction in the viscosity index compared to conventional poly-alpha olefin lubricant (PAO).

α-Olefin Trimerization for Lubricant Base Oils with Modified Chevron–Phillips Ethylene Trimerization Catalysts

“…The replacement of CrCl 3 (THF) 2 with Cr(acac) 3 in the catalytic system of CrCl 3 (THF) 2 /1-Li/(iBu) 3 Al substantially improved the TON (1360 vs 770 at 24 h; Table 2, entry 9 vs Table 1, entry 6). Furthermore, the replacement of 1-Li with 1-Na [i.e., catalytic system of Cr(acac) 3 /1-Na/(iBu) 3 Al] further improved the TON (1550 at 24 h; Table 2, entry 10). The optimal Cr(acac) 3 /1-Na ratio was 3.0; a reduction in the ratio…”

“…When an equimolar amount of (iBu) 3 Al was added to a solution of 1-Cr[CH 2 C 6 H 4 (ortho-NMe 2 )-κ 2 C,N] 2 in C 6 D 6 for 1 H NMR studies, characteristic (iBu) 3 Al signals (0.26 ppm as the doublet, 1.0 ppm as the doublet, and 2.0 ppm as the septet) were not detected. Instead, an extremely broad signal appeared at 1.0−1.7 ppm with no other signals (Figure S3a).…”

“…When 3.0 equiv of (iBu) 3 Al was treated, new sets of signals corresponding to ortho-Me 2 NC 6 H 4 CH 2 Al(iBu) 2 , isobutene, and isobutane appeared along with the broad signal at 1.0−1.7 ppm (Figure S3b). The reaction was so slow that 3 days were required for the complete disappearance of (iBu) 3 3, entry 2) to 4300, 5200, 5700, 6500, 7500, and 11000, respectively. These observations indicated that the bimolecular catalyst deactivation process occurred, which was also observed not only in the catalytic system of (trialkyltriazacyclohexane)CrCl 3 /MAO (Scheme 1a) but also in that of the titanium complex/B(C 6 F 5 ) 3 (Scheme 1b).…”

“…Lubricant base oils are classified into five groups: groups I–III are obtained directly from petroleum refinery; group IV is synthetic hydrocarbons; and group V contains all other types. group IV base oils are synthesized through the oligomerization of α-olefins (typically, cationic oligomerization of 1-decene) and called poly­(α-olefin)­s (PAOs). − With high viscosity indices (VI >120) and outstanding oxidative stabilities, PAOs are treated as top-tier base oils and produced at a global annual scale of approximately 600,000 tons. , In the cationic oligomerization, a range of n -mers (such as a dimer, a trimer, or a tetramer) are simultaneously generated with a Shulz–Flory distribution, which are fractionated by energy-intensive distillation. Moreover, severe skeleton rearrangement generates many methyl groups along the carbon chains, resulting in the deterioration of oxidative stability .…”

“…23 MAO obtained from Me 3 Al is costly. Whereas common Et 3 Al and (iBu) 3 Al are produced atom-economically using inexpensive raw materials Al, H 2 , and ethylene (or isobutene), Me 3 Al is produced expensively using Al, CH 3 Cl, and Na metal with the generation of a NaCl byproduct. Moreover, MAO is typically required in excess (Al/Cr > 300).…”