Insights into the Catalytic Performance of Mesoporous H‐ZSM‐5‐Supported Cobalt in Fischer–Tropsch Synthesis

Abstract Mesoporous H‐ZSM‐5 ( meso H‐ZSM‐5) was used as a carrier for a series of bifunctional Co‐based catalysts for Fischer–Tropsch synthesis with ZrO 2 and/or Ru added as promoters. The reducibility of the catalysts was studied in detail by using temperature‐programmed reduction and X‐ray absorption spectroscopy. A comparison of the catalytic performance of Co/ meso H‐ZSM‐5 and Co/SiO 2 (a conventional catalyst), after 140 h on stream, reveals that the former is two times more active and three times more selective to the C5–C11 fraction with a large content of unsaturated hydrocarbons, which is next to α‐olefins. The acid‐catalyzed conversion of n ‐hexane and 1‐hexene, as model reactions, demonstrates that the improvement in the selectivity toward gasoline range hydrocarbons is due to the acid‐catalyzed reactions of the Fischer–Tropsch α‐olefins over the acidic zeolite. The formation of methane over the zeolite‐supported Co catalysts originates from direct CO hydrogenation and hydrocarbon hydrogenolysis on coordinatively unsaturated Co sites, which are stabilized as a consequence of a strong metal–zeolite interaction. Although the addition of either ZrO 2 or Ru increases the catalyst reducibility considerably, it does not affect the product selectivity significantly.