CO oxidation and preferential oxidation of CO in the presence of hydrogen over SBA-15-templated CuO Co3O4 catalysts

Copper-cobalt mesostructured spinel replicas of SBA-15 were synthesized through a hard template pathway. The catalysts, with Cu/(Co + Cu) atomic ratio in the range 0-17%, were characterized as to their structure, morphology, texture and redox features by X-ray diffraction, FTIR spectroscopy, transmission electron microscopy, N 2 physisorption, and temperature-programmed reduction with hydrogen. The catalysts were tested in a fixed-bed reactor for CO oxidation both in the absence of hydrogen (1.5 mol% CO, 1.5 mol% O 2, balance He, 40-140 °C) and in a hydrogen-rich atmosphere (1.5 mol% CO, 1.5 mol% O 2, 46 mol% H 2, balance He, 40-200 °C). In the absence of hydrogen, catalytic activity for CO oxidation was similar for all the samples for temperatures up to ca. 100 °C, at which 50% CO conversion was observed. Above such temperature the copper-containing catalysts appeared more active than the pure Co 3O 4. All the catalysts were active for the preferential oxidation of CO in hydrogen-rich atmosphere, with 50% CO conversion occurring in the 123-138 °C range. Both CO and oxygen conversions were enhanced by the presence of copper, which however also favoured the occurrence of parasite hydrogen combustion. Methanation was observed (to a limited extent, at temperatures ≥160-180 °C) only on the Cu-containing catalysts. The performance of the present catalysts was compared with literature results for CO oxidation and preferential CO oxidation on cobalt and copper-cobalt oxides prepared by different methods. The hard-templated catalysts seem superior to traditionally prepared ones in the case of CO oxidation in the absence of hydrogen, whereas no clear-cut conclusion can be drawn in the case of preferential CO oxidation.