Gasoline selective Fischer-Tropsch synthesis in structured bifunctional catalysts

Abstract

The need for energy independence and security has refocused research on Fischer-Tropsch Synthesis (FTS) and its capability to selectively produce short and branched hydrocarbons. In this work, FTS selectivity to gasoline-range products was explored as a catalysis and process engineering problem. Novel structured catalysts for in situ upgrading of FTS products to gasoline-range hydrocarbons were successfully synthesized by coating controlled-thickness ZSM-5 films on the surface of Co-Al2O3/monolith substrates. These catalysts were synthesized on the premise that the monolith serves as an efficient mass and heat transfer structure, while the ZSM-5 layer functions as a hydrocarbon cracking and isomerization agent. Compared to traditional diesel-selective FTS, considerably higher quantity and quality of gasoline-range products were achieved with these bi-layered/bifunctional catalysts. Oil products with gasoline yield higher than 65 wt.% and selectivity to isomers and olefins greater than 70 wt.% were formed at relatively high temperature (230 °C) and intermediate pressure (12 bar), without compromising CO conversion, which remained as high as 79%.