Partial oxidation of methane and the effect of sulfur on catalytic activity and selectivity

Partial oxidation of methane into syngas was conducted over fresh and sulfided catalysts at a temperature range of 450–750 °C. The temperature dependence of conversion, H2/CO ratio, and the CO2 concentration were measured for both fresh and sulfided catalysts. Regardless of metal type, metal loading, support type, and the methods of preparation it appears that all the fresh catalysts were very active and conversions of higher than 70% with H2/CO ratio of about 2 were observed at 750 °C. Pulse sulfidation appears to be reversible for some of the catalysts but not for all. Under pulse sulfidation conditions, the Rh(0.5%)/Al2O3 and NiMg2Ox-1100 °C (solid solution) catalysts were fully regenerated after reduction with hydrogen. Rh catalyst showed the best overall activity, less carbon deposition, both fresh and when it was exposed to pulses of H2S. Sulfidation under steady-state conditions, flowing H2S/Ar mixture over the catalysts, significantly reduce catalyst activity. The catalysts were characterized before and after reaction with H2S using temperature-programmed oxidation (TPO) and reduction (TPR), X-ray diffraction, and XPS.