Catalytic Roles of Co0 and Co2+ during Steam Reforming of Ethanol on Co/MgO Catalysts

The catalytic roles of Co0 and Co2+ during steam reforming of ethanol were investigated over Co/MgO catalysts. Catalysts with different Co0/(Co0+Co2+) fraction were prepared through calcination and/or reduction at different temperatures, and the Co0 fraction was quantified by temperature programmed reduction (TPR) and in situ X-ray photoelectron spectroscopy (XPS). Higher temperature calcination of Co/MgO allowed us to prepare catalysts with more nonreducible Co2+ incorporated in the MgO lattice, while lower calcination temperatures allowed for the preparation of catalysts with higher Co0/(Co0+Co2+) fractions. The catalytic tests on Co0, nonreducible Co2+, and reducible Co2+ indicated that Co0 is much more active than either reducible or nonreducible Co2+ for C−C cleavage and water gas shift reaction. In addition, catalysts with a higher Co0 surface fraction exhibited a lower selectivity to CH4.