Catalytic steam reforming of methane, methanol, and ethanol over Ni/YSZ: The possible use of these fuels in internal reforming SOFC

摘要

This study investigated the possible use of methane, methanol, and ethanol with steam as a direct feed to Ni/YSZ anode of a direct internal reforming Solid Oxide Fuel Cell (DIR-SOFC). It was found that methane with appropriate steam content can be directly fed to Ni/YSZ anode without the problem of carbon formation, while methanol can also be introduced at a temperature as high as 1000 deg C. In contrast, ethanol cannot be used as the direct fuel for DIR-SOFC operation even at high steam content and high operating temperature due to the easy degradation of Ni/YSZ by carbon deposition. From the steam reforming of ethanol over Ni/YSZ, significant amounts of ethane and ethylene were present in the product gas due to the incomplete reforming of ethanol. These formations are the major reason for the high rate of carbon formation as these components act as very strong promoters for carbon formation. It was further observed that ethanol with steam can be used for an indirect internal reforming operation (HR-SOFC) instead. When ethanol was first reformed by Ni/Ce-ZrO_2 at the temperature above 850 deg C, the product gas can be fed to Ni/YSZ without the problem of carbon formation. Finally, it was also proposed from the present work that methanol with steam can be efficiently fed to Ni/YSZ anode (as DIR operation) at the temperature between 900 and 975 deg C without the problem of carbon formation when SOFC system has sufficient space volume at the entrance of the anode chamber, where methanol can homogeneously convert to CH_4, CO, CO_2, and H_2 before reaching SOFC anode.