Low-temperature CeCoMnOx spinel-type catalysts prepared by oxalate co-precipitation for selective catalytic reduction of NO using NH3: A structure–activity relationship study

Abstract

CeCoMnOx spinel-type catalysts for the selective catalytic reduction of NO using NH3 (NH3-SCR) are usually prepared by alkaline co-precipitation. In this paper, a series of CeCoMnOx spinel-type catalysts with different calcination temperatures were prepared by acidic oxalate co-precipitation. The physicochemical structures and NH3-SCR activities of the CeCoMnOx spinel-type catalysts prepared by oxalate co-precipitation and conventional ammonia co-precipitation were systematically compared. The results show that the CeCoMnOx spinel-type catalysts prepared by the oxalate precipitation method (CeCoMnOx-C) have larger specific surface area, more mesopores and surface active sites, stronger redox properties and adsorption activation properties than those prepared by the traditional ammonia co-precipitation method at 400 °C (CeCoMnOx-N-400), and thus CeCoMnOx-C have better low-temperature NH3-SCR performance. At the same calcination temperature of 400 °C, the NO conversion of CeCoMnOx-C-400 exceeds 89 % and approaches 100 % within the reaction temperature of 100–125 °C, which is 14.8 %-2.5 % higher than that of CeCoMnOx-N-400 at 100–125 °C. In addition, the enhanced redox and acid cycle matching mechanisms on the CeCoMnOx-C surface, as well as the enhanced monoadsorption Eley-Rideal (E-R) and double adsorption Langmuir-Hinshelwood (L-H) reaction mechanisms, are also derived from XPS and in situ DRIFTS characterization.