Catalysts of sodium silicate and cadmium oxide supported on silicon carbide nanopowders were synthesized and used in catalytic oxidation of H2S to elemental sulfur. The effect of temperature (from 150 to 250 degrees C); gas hour space velocity (from 2000 to 4000 h(-1)) and sodium:cadmium weight ratio (from 1 to 5), on the conversion of H2S were studied by a Box-Behnken experimental design method. A quadratic regression equation was developed to describe relationship between the operating conditions and the response. The significance of main factors and their quadratic interactions on the conversion of H2S in catalytic oxidation were examined by means of the analysis of variance (ANOVA). The results showed that temperature had the most significant effect on H2S conversion compared with other two variables. F value of 29.46, coefficient of determination (R-2) of 0.9779, adjusted-R-2 of 0.9447, absolute average deviation (AAD) of 0.29% and, coefficient of variation (CV) of 0.59%, implied the satisfactory adjustment of the quadratic model. The results indicated that up to 100% H2S conversion was obtained at the optimum conditions. (C) 2012 Elsevier B.V. All rights reserved.