Effect of Support on Catalytic Performance of Photothermal Fischer-Tropsch Synthesis to Produce Lower Olefins over Fe 5
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doi: 10.1007/s40242-020-0253-5
Article
Effect of Support on Catalytic Performance of Photothermal Fischer-Tropsch Synthesis to Produce Lower Olefins over Fe5C2-based Catalysts LI Yuan, LI Ruizhe, LI Zhenhua, WEI Weiqin, OUYANG Shuxin *, YUAN Hong and ZHANG Tierui College of Chemistry, Central China Normal University, Wuhan 430079, P. R. China Abstract Photothermal Fischer-Tropsch synthesis(FTS) has been extensively studied, but few reports were focused on systematically exploring the influence of support on catalytic performance. Herein, a series of Fe 5C2-based catalysts with different supports was fabricated via a one-step wet-chemical method for photothermal conversion of syngas to lower olefins. Under light irradiation, the optimized Fe 5C2/α-Al2O3 catalyst demonstrated remarkable photothermal FTS activity, delivering selectivity to lower olefins of 50.3% with a CO conversion rate of 52.5%. Characterization studies using X-ray diffraction and Mössbauer spectroscopy analysis revealed that the active catalyst mainly contained Fe5C2 nanoparticles on α-Al2O3 support. It was found that the weak interaction between active phase and α-Al2O3 could promote the formation of Fe 5C2, which contributed to the high selectivity to lower olefins. Keywords χ-Fe5C2 catalyst; Fischer-Tropsch synthesis; Metal-support interaction; Photothermal catalysis
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Introduction
Lower olefins(C2—C4) are extensively used as raw materials to synthesize a wide range of products, such as synthetic textiles, solvents, and coatings, which occupies huge market demand in the whole industrial manufacture chain[1—3]. The conventional route for the production of lower olefins relies on the thermal or catalytic cracking of naphtha or vacuum gas oil[4,5]. However, limited petroleum resources and high oil prices have inhibited the application of this route, and therefore, the other new routes were developed to meet the growing demand of lower olefins[6,7]. Among different techniques, the Fischer-Tropsch synthesis(FTS), as an approach to directly convert syngas(CO and H2) to lower olefins(which are also known as FTO)[8], has become a hot topic in recent years because of its economic advantages, such as few reaction steps, simple production equipment and cheap raw materials[9,10]. In FTO, iron occupies an indispensable status not only due to its low cost and high operational flexibility, but also for its high selectivity to lower olefins with low CH4 productivity at high reaction temperatures[2,11]. Many studies suggest that the reactivity of the Fe-based FT catalyst is correlated with the properties of iron carbides[12—14]. It is worth noting that much experience indicates that Fe5C2 is the active phase of Fe-based catalyst for FTO, which is responsible for the high activity for lower olefins production in FTO[15,16]. Ma and co-authors[17] synthesized single-phase Fe5C2 nanoparticles(NPs) by a facile wet chemical route; the Fe5C2 NPs exhibited higher intrinsic catalytic activity than conventional reduced hematite catalyst in
the thermally catalyzed F
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