Production of Synthesis Gas by Partial Oxidation of Methane over the Group VIII Metal Catalysts.

Abstract

Specific activities and reaction pathway in the CO-H2 formation by partial oxidation of CH4, CH4+1/2O2→CO+2H2, have been studied on SiO2 supported group VIII metal catalysts. Over Rh, Ru and Ni catalysts at relatively low temperature (600-700K), CO2 and H2O were produced by complete oxidation of CH4. At higher temperature, the initially formed CO2 and H2O led to CO and H2 by reactions of CH4+H2O and CH4+CO2 which are endothermic reactions. The yield of products was well explained by equilibrium and kinetic consideration of the composite reactions. Above 900K the conversion of CH4 to CO and H2 was about 90% over these three catalysts. Pt catalyst also showed activity for the CO and H2 formation at temperature as high as 900K. It was suggested that reverse water gas shift reaction was involved in the reaction pathway over Pt. Pd catalyst showed lower activity for CO and H2 formation. On the other hand, only CO2 and H2O were produced by the complete oxidation of CH4 over Fe and Co catalysts. For catalysts used here, the CH4+CO2 and CH4+H2O reactions are completely hindered during the period when complete oxidation is proceeding on the surface. The retardation was ascribed to the state of oxidation of catalysts surface.