Steam Reforming of Dimethyl Ether by Use of Catalyst Mixture of Cu/Zn Loaded Carbon Catalyst and γ-Al2O3

摘要

Steam reforming of Dimethyl ether (DME) was performed by using a carbon catalyst highly dispersed with Cu/Zn. The Cu and Zn particles were less than 10 nm in diameter. The particles were highly dispersed on a carbon support through carbonization of an ion-exchange resin that was exchanged with Cu~(2+) and Zn~(2+) at 500°C. Cu/Zn loaded carbon catalyst did not enhance any catalytic activity in the steam reforming of DME because of its poor reactivity on hydrolysis reaction. Therefore, it was combined with γ-Al2O3, which is known to have a catalytic activity in DME hydrolysis. Indeed, the reactivity on steam reforming of DME was enhanced by mixing uniformly both catalysts, and the optimum mixing ratio of the Cu/Zn loaded carbon to γ-Al2O3 was found to be 2/3 by weight. We also studied three packing modes of catalysts in a tubular reactor; 2-layer packing, 4-layer packing, and mixed packing. The highest DME conversion and lowest CO yield were obtained by the mixed packing mode. This indicates that close distance between the active sites for DME hydrolysis and steam reforming of methanol produced, enhances the overall steam reforming reaction from DME to hydrogen. By using the mixed packing mode, DME conversions reached to 0.43 at 300°C and more than 0.9 at 360°C–400°C, respectively, while the CH4 yield was suppressed to less than 0.50 mol/mol DME. In addition, CO and CH4 yields by the proposed catalyst were lower than those by a conventionally used Cu/ZnO/γ-Al2O3 catalyst prepared by the impregnation method. Thus, it was verified that the proposed catalyst were effective for producing hydrogen form DME.