Effect of Alkali Metal Impurities on Co–Re Catalysts for Fischer–Tropsch Synthesis from Biomass-Derived Syngas

Abstract

The effect of alkali impurities on Co-based Fischer-Tropsch (FT) catalysts is important for processing biomass-derived synthesis gas containing inorganic ash impurities. The effects of Na, K, Li, and Ca impurities on c-Al 2 O 3 -supported Co-Re powder catalysts were studied at impurity loadings between 25 and 1,000 ppm. Impurity addition did not have any effect on H 2 chemisorption, but the catalyst activity decreased during FT synthesis experiments. The impurities were also found to slightly increase the reduction temperatures of Co. Carbon selectivities to CH 4 decreased with increasing impurity loading, while CO 2 and C 5? hydrocarbon selectivities increased. Catalyst behavior was attributed mostly to electronic effects from the alkali addition, leading to decreased surface H concentrations and increased CO adsorption and dissociation.

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