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RESEARCH PRODUCT

Co3O4/CeO2 composite oxides for methane emissions abatement: Relationship between Co3O4–CeO2 interaction and catalytic activity

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Abstract Co 3 O 4 /CeO 2 composite oxides with different cobalt loading (5, 15, 30, 50, 70 wt.% as Co 3 O 4 ) were prepared by co-precipitation method and investigated for the oxidation of methane under stoichiometric conditions. Pure oxides, Co 3 O 4 and CeO 2 were used as reference. Characterization studies by X-ray diffraction (XRD), BET, temperature programmed reduction/oxidation (TPR/TPO) and X-ray photoelectron spectroscopy (XPS) were carried out. An improvement of the catalytic activity and thermal stability of the composite oxides was observed with respect to pure Co 3 O 4 in correspondence of Co 3 O 4 –CeO 2 containing 30% by weight of Co 3 O 4 . The combined effect of cobalt oxide and ceria, at this composition, strongly influences the morphological and redox properties of the composite oxides, by dispersing the Co 3 O 4 phase and promoting the efficiency of the Co 3+ –Co 2+ redox couple. The presence in the sample Co 3 O 4 (30 wt.%)–CeO 2 of a high relative amount of Ce 3+ /(Ce 4+  + Ce 3+ ) as detected by XPS confirms the enhanced oxygen mobility. The catalysts stability under reaction conditions was investigated by XRD and XPS analysis of the used samples, paying particular attention to the Co 3 O 4 phase decomposition. Methane oxidation tests were performed over fresh (as prepared) and thermal aged samples (after ageing at 750 °C for 7 h, in furnace). The resistance to water vapour poisoning was evaluated for pure Co 3 O 4 and Co 3 O 4 (30 wt.%)–CeO 2 , performing the tests in the presence of 5 vol.% H 2 O. A methane oxidation test upon hydrothermal ageing (flowing at 600 °C for 16 h a mixture 5 vol.% H 2 O + 5 vol.%O 2 in He) of the Co 3 O 4 (30 wt.%)–CeO 2 sample was also performed. All the results confirm the superiority of this composite oxide.