Hydrogenation of CO2 over nickel catalysts supported on rice husk ash prepared by ion exchange

Nickel catalysts supported on rice husk ash prepared by the ion exchange technique were investigated and characterized by TEM, SEM, XRD, TPR and H-2-TPD techniques. The catalytic activities of nickel catalysts were tested by CO2 hydrogenation with H-2/CO2 ratios of 4/1 for temperatures between 673 and 873 K. During the investigations of preparation conditions, effects of calcination, nickel loading and reaction temperature on catalytic performance were also examined. The results show that catalysts prepared by ion exchange yield finely dispersed and evenly distributed nickel crystallites. The metal dispersion increases with a decrease in nickel loading. The conversion of CO2 and the yield of CH4 are found to be independent of the calcination time and temperature. Furthermore, the conversion and yield increase with an increasing reaction temperature up to 773 K, but decrease with a further increase in the reaction temperature. Moreover, rice husk ash supported nickel catalysts display higher nickel surface area and activity than silica gel as revealed by the H2-TPD and the hydrogenation tests. (C) 2001 Elsevier Science B.V. All rights reserved.