Nickel catalysts supported on rice husk ash-alumina (Ni/RHA-Al2O3) were prepared by the incipient wetness impregnation method. Characterizations were investigated by TPR, XPS, XRD, SEM, and BET techniques. The catalytic activities of nickel catalysts were tested by CO2 hydrogenation with H-2/CO2 ratio of 4:1 for temperatures between 400 and 800 degreesC. The XPS analysis of Ni/RHA-Al2O3 demonstrated the presence of spinel. The TPR analysis indicated that the interaction between nickel and support was strong and difficult to reduce with more than one nickel oxide compound, such as bulk NiO and two NiAl2O4-like species. The results of N-2-adsorption by BET indicated that the maximum surface area was found at 15 wt.% nickel loading with mesopores. The XRD analysis of samples suggested that the crystallite sizes of supported NiO increased with the increase in nickel loading. The CO2 conversion and CH4 yield for CO2 hydrogenation were found to depend on the nickel loading. The reaction temperature of 500degreesC might be the optimum temperature for CO2 hydrogenation to give the maximum yield and selectivity of CH4. Furthermore, the hydrogenation tests showed that the performance of Ni/RHA-Al2O3 is better than that of Ni/SiO2-Al2O3. (C) 2003 Elsevier Science B.V. All rights reserved.