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, N2 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% O2, balance He, 40–140 °C) and in a hydrogen-rich atmosphere (1.5 mol% CO, 1.5 mol% O2, 46 mol% H2, 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 Co3O4. 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.

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► SBA-15-templated, rod-shaped Co3O4 and Co–Cu spinels were prepared.
► Cu is beneficial in the CO oxidation only at reaction temperatures above 100 °C.
► PROX occurs with higher O2 and CO conversions on the Cu-containing catalysts.
► Cu enhances H2 combustion and, at high temperature, induces some methanation.
► Methanation seems catalyzed by metallic cobalt formed during the PROX run.