The rice husk ash supported nickel catalysts was prepared by deposition-precipitation and used for hydrogenation of CO2 from a H-2/CO2 (4/1) mixture. The reaction exhibited high selectivity (80%) for CH4 formation when carried out at 673-873 K with the supported nickel. The effects of nickel loading, deposition-precipitation time, calcination, and reduction of temperature on the catalytic performance were also extensively studied. These results show that nickel loading increases with an increase in the deposition-precipitation time up to 24 h, while metal dispersion increases with a decrease in nickel loading. The conversion of CO2 and the yield of CH4 were found to be independent of the calcination temperature and time. Furthermore, the conversion and yield increase with an increasing reaction temperature up to 723 K, but decrease with a further increase in the reaction temperature. Moreover, rice husk ash has been found to be preferable over silica gel as a catalyst support as revealed by the temperature-programed desorption techniques and the reaction test.
