March 19, 2012
Use this non–transition-metal catalyst for olefin codimerization. Commercial homogeneous and heterogeneous olefin dimerization catalysts typically are based on transition metals. Perhaps the best-known example is used in IFP’s Dimersol process. The Dimersol catalyst is a nickel complex combined with a Lewis acid such as AlCl3 or BF3.
A subtle problem with these catalysts is that they are more active for dimerizing lighter olefins than heavier olefins. When a codimerization reaction is attempted, the lighter olefin is consumed first to make a homodimer. The heavier olefin does not react or produces an additional, heavier homodimer.
M. Sigl, M. Triller, and T. Heidermann developed a non–transition-metal heterogeneous dimerization catalyst that can produce codimers effectively. The catalyst is H-β-zeolite shaped with an Al2O3 (boehmite) binder in a 24:1 SiO2/Al2O3 mol ratio.
For the codimerization reaction, the catalyst was activated at 250 °C in a stream of nitrogen for 18 h. An oil-heated double-walled reactor was then filled with 8 mL of crushed catalyst. The feed to the reactor was 12 g/h of a mixture of 64 wt% C8 olefins and 36 wt% C4 olefins. The C8 olefins were mostly 3-methylheptene; the C4 olefins consisted of a mixture of 37% 1-butene, 42% 2-butene, 2% isobutene, and 19% butanes. In addition to the feed stream, a 76 g/h recycle stream was passed through the reactor.
After 160 h of reaction time at 80 °C and 25 bar, the yield of C12 hydrocarbons was 51%. The starting C4 and C8 olefins were both consumed. In a comparative experiment, the conditions were identical, except that the catalyst described above was replaced with a NiO/SiO2 catalyst. In contrast to the initial experiment, only the C4 olefins were consumed; the C8 olefins emerged essentially unreacted. (BASF SE [Ludwigshafen, Germany]. US Patent 8,129,572, March 6, 2012; Jeffrey S. Plotkin)