Fischer-tropsch synthesis in monolith catalysts coated with hierarchical ZSM-5

Abstract Fischer-Tropsch synthesis (FTS) is explored as a candidate one-step process for the selective conversion of synthesis gas to short and branched hydrocarbons. Novel structured catalysts for in-situ upgrading of FTS products to gasoline-range hydrocarbons are synthesized by coating controlled-thickness ZSM-5 films on the surface of Co-Al2O3/monolith substrates. FTS catalysts with coating of microporous and mesoporous ZSM-5 are synthesized, characterized and tested. These catalysts leverage the benefits of monolith reactors as efficient mass and heat transfer structures, with the ZSM-5 layer as a hydrocarbon cracking and isomerization agent. Hierarchical ZSM-5 co-catalysts are shown to relax mass transfer limitations through the zeolite film, thus improving conversion and selectivity. The proposed co-catalysts exhibit high CO conversion and high gasoline selectivity with high octane number. Loss of catalyst activity was observed and attributed to ZSM-5 pore plugging by C13+ saturated hydrocarbons. In-situ regeneration of the catalysts enabled stability in FTS performance.