Dual-Zeolite Catalysts for Synthesis of Liquid Hydrocarbon Fuels

A series of bifunctional cobalt composite catalysts supported on mixed zeolites were synthesized to enhance the selectivity towards liquid fuels rich in branched hydrocarbons. Given that the catalysts were prepared with an alumina binder and that the mixed zeolites consisted of two molecular sieves, the finished samples were generally formulated as Co–Al2O3/SiO2 + [ZSM-5 + (ZSM-23, Beta, SAPO-11)] + Al2O3. The catalysts were tested in Fischer–Tropsch synthesis at 240°C, 2.0 MPa, an H2/CO ratio of 2 : 1, and a syngas hourly space velocity (GHSV) of 1000 h–1. The catalyst supported on ZSM-5+Beta exhibited the highest selectivity towards C5–C10 hydrocarbons. The ZSM-5+ZSM-23-supported catalyst turned out to be the most selective towards branched hydrocarbons, which, in turn, favored the production of a diesel fraction with optimal low-temperature properties.