The synthesis of CuyMnzAl1−zOx mixed oxide as a low-temperature NH3-SCR catalyst with enhanced catalytic performance

A new type of low-temperature selective catalytic reduction (SCR) catalyst, CuyMnzAl1-zOx, derived from layered double hydroxides is presented in this contribution. By tuning the Cu/Mn/Al ratio, the optimal catalyst Cu2Mn0.5Al0.5Ox resulted in a NOx conversion of 91.2% at 150 °C, which is much higher than that of all other control catalysts, Cu2AlOx (71.1%), Cu-Mn/γ-Al2O3 (65.23%), and Mn/γ-Al2O3 (59.32%). All samples were characterized in detail using various physico-chemical techniques including XRD, BET, FTIR, TEM, H2-TPR, NH3-TPD, and XPS analyses, and the results revealed that the superior catalytic performance of the Cu2Mn0.5Al0.5Ox catalyst can be attributed to its high specific surface area, high reducibility of MnO2 and CuO species, abundance of surface acid sites, and the good dispersion of MnO2 and CuO species. FTIR analyses of pyridine adsorbed samples revealed that the catalytic activity is proportional to the amount of Lewis acid sites. Cu2Mn0.5Al0.5Ox also showed much higher resistance to 100 ppm SO2 and 5% H2O than the control catalysts. The poisoning mechanism and the regenerability of the Cu2Mn0.5Al0.5Ox catalyst was also investigated. In all, compared with the control catalysts of Cu2AlOx, Cu-Mn/γ-Al2O3, and Mn/γ-Al2O3, the newly designed Cu2Mn0.5Al0.5Ox catalyst is not only more active at low temperatures (100-250 °C), but is also relatively more robust in the presence of SO2 and H2O.