The synthesis of Cu y Mn z Al 1-z O x mixed oxide as a low-temperature NH 3 -SCR catalyst with enhanced catalytic performance.

A new type of low-temperature selective catalytic reduction (SCR) catalyst, Cuy Mnz Al1-z Ox , derived from layered double hydroxides is presented in this contribution. By tuning the Cu/Mn/Al ratio, the optimal catalyst Cu2 Mn0.5 Al0.5 Ox resulted in a NOx conversion of 91.2% at 150 °C, which is much higher than that of all other control catalysts, Cu2 AlOx (71.1%), Cu-Mn/γ-Al2 O3 (65.23%), and Mn/γ-Al2 O3 (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 Cu2 Mn0.5 Al0.5 Ox 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. Cu2 Mn0.5 Al0.5 Ox also showed much higher resistance to 100 ppm SO2 and 5% H2 O than the control catalysts. The poisoning mechanism and the regenerability of the Cu2 Mn0.5 Al0.5 Ox catalyst was also investigated. In all, compared with the control catalysts of Cu2 AlOx , Cu-Mn/γ-Al2 O3 , and Mn/γ-Al2 O3 , the newly designed Cu2 Mn0.5 Al0.5 Ox catalyst is not only more active at low temperatures (100-250 °C), but is also relatively more robust in the presence of SO2 and H2 O.