Hydrogen production by auto-thermal reforming of ethanol over Ni/γ-Al2O3 catalysts: Effect of second metal addition

Ni/γ-Al2O3 catalysts containing a second metal (Ce, Co, Cu, Mg and Zn) are prepared by a co-impregnation method to investigate the effect of second metal addition on the catalytic performance in the auto-thermal reforming of ethanol. Among the second metals tested, Cu is found to be the most efficient promoter for the production of hydrogen. It is revealed that Cu species are active in the water-gas shift reaction to produce hydrogen from CO and H2O, and furthermore, Cu species serve as a barrier for preventing the growth of Ni particles. In particular, the addition of Cu decreases the interaction between Ni-species and γ-Al2O3, leading to the facile reduction of Ni-Cu/γ-Al2O3 catalyst. Among Ni-Cu/γ-Al2O3 catalysts with different Cu content, a 5 wt.% Cu-containing Ni-Cu/γ-Al2O3 catalyst, which retains an intermediate state of Cu species between copper aluminate and copper oxide, shows the best catalytic performance in terms of hydrogen production and CO composition in the outlet stream. By contrast, a 7 wt.% Cu-containing Ni-Cu/γ-Al2O3 catalyst exhibits rather a low catalytic performance in the production of hydrogen because of the suppressed gasification activity over large Cu particles in the catalyst.