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

CeCoMnO spinel-type catalysts for the selective catalytic reduction of NO using NH (NH-SCR) are usually prepared by alkaline co-precipitation. In this paper, a series of CeCoMnO spinel-type catalysts with different calcination temperatures were prepared by acidic oxalate co-precipitation. The physicochemical structures and NH-SCR activities of the CeCoMnO spinel-type catalysts prepared by oxalate co-precipitation and conventional ammonia co-precipitation were systematically compared. The results show that the CeCoMnO spinel-type catalysts prepared by the oxalate precipitation method (CeCoMnO-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 (CeCoMnO-N-400), and thus CeCoMnO-C have better low-temperature NH-SCR performance. At the same calcination temperature of 400 °C, the NO conversion of CeCoMnO-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 CeCoMnO-N-400 at 100-125 °C. In addition, the enhanced redox and acid cycle matching mechanisms on the CeCoMnO-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.