Integration of Catalytic Oxidation and Reforming of Methane over a Dual-Catalyst Bed for the Production of Syngas

This present work investigates the potential advantages of combining exothermic catalytic methane oxidation with endothermic catalytic reforming of methane over a dual-catalyst bed to produce syngas, partly similar to the autothermal reforming (ATR) of methane. Noncatalytic oxidation of methane, hot-spot formation, coking, and catalyst stability are the major challenges in the traditional ATR process, and using two catalysts to sequentially combine the oxidation and reforming was shown to address the aforementioned challenges. An oxidation catalyst (Pd/CeO2/Al2O3) and mesoporous alumina-supported (MAl) bimetallic RhNi and NiCo catalysts as reforming catalysts were chosen and packed in a fixed-bed catalytic reactor as layers and in a blended form. The sequential layer of Pd/CeO2/Al2O3 and NiCo/MAl, as well as the blended form of Pd/CeO2/alumina and RhNi/MAl, was able to reform methane using steam and oxygen as the oxidant feed to produce syngas with excellent catalyst stability. The Pd/CeO2/Al2O3 catalyst demonstrated methane oxidation capability, achieving high activity at temperatures as low as 290 °C and generating substantial heat at higher temperatures, sufficient to initiate the downstream reforming reactions over the reforming catalyst. The H2/CO ratio present in the as-produced syngas was higher than that of the CO-rich syngas obtained by dry methane reforming (DRM) and catalytic partial oxidation (CPOX) but lower than the ratio obtained from steam reforming of methane (SRM) and ATR processes. DFT studies revealed that the combination of exothermic oxidation and endothermic reforming in a dual-catalyst bed improved the activity of reforming and enhanced the syngas production as well as the catalyst stability.