Selection of cobaltite and effect of preparation method of NiCo2O4 for catalytic oxidation of CO–CH4 mixture

Abstract

CNG is used as a green-fuel for automobiles. However, it is a source of CO and CH4 emissions, causing an adverse impact on human-health and climate-change. Therefore, to reduce tailpipe emissions, this work aims to select the best cobaltite catalyst for the oxidation of a lean mixture of CO-CH4 in air. The cobaltite catalysts i.e. (MCo2O4, M=Ni, Co, Mn, Fe, Cu) were prepared by co-precipitation method, calcined in the reactive CO-air mixture and characterized by XRD, XPS, FTIR, SEM, SEM-EDX and TPR. Among studied catalysts, NiCo2O4 showed the highest activity for total oxidation of CO-CH4 mixture at the lowest temperature of 350 °C, reported so far in the literature. The performance order of catalysts is as follows: NiCo2O4>CoCo2O4>MnCo2O4>CuCo2O4>FeCo2O4. To examine the effect of preparation methods on activity, the best-selected NiCo2O4 were prepared by different methods i.e. sol-gel, reactive grinding (RG) of nitrates and of metal oxides. The catalyst prepared by co-precipitation method showed the best performance for the oxidation of CO-CH4 mixture in comparison to others. The order of the preparation method as per activity of the catalysts is as follows: Co-ppt>RG of nitrates>RG of oxides>Sol-gel. The spinel phase confirmed in all catalysts except one prepared by RG of metal oxides. © 2017 Curtin University of Technology and John Wiley & Sons, Ltd. © 2017 Curtin University of Technology and John Wiley & Sons, Ltd.