Effect of calcination temperature on catalyst reducibility and hydrogenation reactivity in rice husk ash-alumina supported nickel systems

Nickel catalysts supported on rice husk ash-alumina (Ni/RHA-Al2O3) were prepared by an incipient wetness impregnation method. Characterization included TGA, DSC, TPR, XRD, and BET. Results show that the decomposition of the nickel compound to nickel oxide was complete above 500degreesC. The TPR analysis revealed a strong interaction between nickel and support, and a decrease in reducibility of NiO with increasing calcination temperature. The XRD analysis of Ni/RHA-Al2O3 catalyst precursors demonstrated the presence of spinel. It also showed that the size of crystallites in the supported NiO first decreased with increase in calcination temperature up to 700degreesC, and then increased due to phase transformation of nickel oxide to spinel. The pores are mesopores and their meshy surface structure was not affected by calcination temperature in the range investigated. The catalytic activity was tested by CO, hydrogenation with an H-2/CO2 ratio of 4/1 at 500degreesC. The CO2 conversion and CH4 yield for CO2 hydrogenation over 15 wt% Ni/RHA-Al2O3 catalyst were almost independent of calcination and reduction temperatures. (C) 2004 Society of Chemical Industry.