An Fe–Mn–Cu/SiO2@silicalite-1 catalyst for CO hydrogenation: the role of the zeolite shell on light-olefin production

Abstract

A core–shell structured catalyst is considered effective for regulating product distribution in a complex reaction network. By systematically analyzing the behaviors of an Fe–Mn–Cu/SiO₂@silicalite-1 core–shell catalyst in Fischer–Tropsch synthesis, a unique temperature-dependent role of the silicalite-1 shell is demonstrated on the distribution of products via modulation of the intra- and inter-pellet secondary reactions, which successfully fulfills synchronous increments of CO conversion, light olefin/light paraffin ratio (C_2–4⁼/C_2–4⁰) and C_2–4⁼ selectivity, opposite to the behavior of a naked industrial Fe–Mn–Cu/SiO₂ catalyst. This effect could be attributed to the different diffusion limitation of the silicalite-1 shell on various reactants/products in different temperature ranges. Such a discovery not only rationally explains the excellent performance of the core–shell catalyst on C_2–4⁼ production but also provides a new clue for the design of catalysts in complex reaction networks.