Abstract
High temperature water-gas shift (HT-WGS) is an industrially highly relevant reaction. Moreover, climate change and the resulting necessary search for sustainable energy sources are making WGS and reverse-WGS catalytic key reactions for synthetic fuel production. Hence, extensive research has been done to develop improved or novel catalysts. An extremely promising material class for novel highly active HT-WGS catalysts with superior thermal stability are perovskite-type oxides. With their large compositional flexibility, they enable new options for rational catalyst design. Particularly, both cation sites (A and B in ABO3) can be doped with promoters or catalytically active elements. Additionally, B-site dopants are able to migrate to the surface under reducing conditions (a process called exsolution), forming catalytically active nanoparticles and creating an interface that can strongly boost catalytic performance. In this study, we varied A-site composition and B-site doping (Ni, Co), thus comparing six novel perovskites and testing them for their HT-WGS activity: La0.9Ca0.1FeO3-δ, La0.6Ca0.4FeO3-δ, Nd0.9Ca0.1FeO3-δ, Nd0.6Ca0.4FeO3-δ, Nd0.6Ca0.4Fe0.9Ni0.1O3-δ and Nd0.6Ca0.4Fe0.9Co0.1O3-δ. Cobalt and Nickel doping resulted in the highest activity observed in our study, highlighting that doped perovskites are promising novel HT-WGS catalysts. The effect of the compositional variations is discussed considering the kinetics of the two partial reactions of WGS-CO oxidation and water splitting.
Highlights
Water gas shift (WGS) is an industrially highly relevant catalytic reaction, with major applications for hydrogen production via steam reforming of methane [1,2] or from renewable sources like biomass and carbonaceous solid wastes [3,4,5], and for coal-to-liquid processes via Fischer–Tropsch synthesis [6].the reaction is involved in many processes as a partial reaction step, e.g., for ammonia or methanol synthesis
Six novel perovskite materials were synthesised for this study
Fe is well known as an active material for the high temperature WGS reaction [37,38]
Summary
Water gas shift (WGS) is an industrially highly relevant catalytic reaction, with major applications for hydrogen production via steam reforming of methane [1,2] or from renewable sources like biomass and carbonaceous solid wastes [3,4,5], and for coal-to-liquid processes via Fischer–Tropsch synthesis [6].the reaction is involved in many processes as a partial reaction step, e.g., for ammonia or methanol synthesis. WGS has received considerable attention from researchers for a long time, primarily for developing more efficient and cheaper catalysts, both for high- and low-temperature WGS reactions [7,8,9,10]. The WGS reaction can be catalysed by both metals and metal oxides, and classical industrial reactions are typically run in two-step processes, with first a high-temperature step, and a low-temperature step. For low-temperature WGS, the most widely used catalyst material is a mixture of CuO, ZnO, and Al2 O3 /Cr2 O3 [17]. These catalysts have, the drawbacks of a lower thermal stability and their intolerance towards sulphur, halogens, and unsaturated hydrocarbons
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