Dimethyl Ether-Reforming Catalysts for Hydrogen Production

This article reviews our recent works on dimethyl ether steam reforming (DME SR) over nanocomposite catalysts of copper-based spinel oxide and solid-acid catalyst. A series of Cu-based spinels was prepared by citric acid complexation method and their catalytic performance was studied in terms of activity, selectivity, and stability. The influence of preparation conditions, such as calcination temperature, reduction temperature, and chemical composition, and reforming conditions, such as steam-to-carbon ratio and reaction temperature, was systematically studied. Effect of type of solid-acid catalyst was also reported. Zeolite-based composites and alumina-based ones are highly active in temperature ranges of < 300 A degrees C and > 300 A degrees C, respectively. The composite of CuFe2O4 and alumina treated thermally in air at 700-800 A degrees C exhibited excellent activity and stability in DME SR. Upon H-2 reduction, phase separation of copper spinel to metallic copper nanoparticles and host oxides proceeds. The high dispersion of the Cu particles (Cu1+-rich surface of ca. 70%) on the hosts, and the strong chemical interaction between them could be observed. The H-2-rich reformate (> 70% H-2) could be attained for longer than 800 h at 375 A degrees C, showing the good potential for practical use in H-2 and fuel cell applications. Doping Ni to CuFe2O4 significantly enhanced the stability of the catalyst, in accordance with the alloying effect. Regeneration of the degraded catalysts could be obtained by simple heat-treatment since carbon deposits were removed, and spinel structures were reconstructed.