Oligomerization of 1-Hexene and 1-Octene over Solid Acid Catalysts

Oligomerization of hexene and heavier olefins is important for synthetic fuel producers to reduce refinery complexity, as well as to produce good quality middle distillates and lubricating oils. Conversion of such olefins with homogeneous catalysts is much easier than with solid acid catalysts, which are prone to deactivation and are limited to middle distillate production. Solid phosphoric acid, amorphous silica-alumina, sulfated zirconia, MCM-41, ZSM-5, zeolite-Y, and zeolite-omega heterogeneous catalysts were evaluated in fixed-bed reactors with 1-hexene and 1-octene to determine the key catalyst properties required. The influence of added chromium and nickel was also evaluated. It was found that solid acids with average pore size of more than 10 nm had consistently better catalyst lifetime, because heavy oligomers were less readily trapped in the catalyst. It was also found that in large-pore catalysts chromium improved selectivity to lubricating oil significantly by changing the oligomerization mechanism.