Influence of Copper Locations on Catalytic Properties and Activities of Cu/SAPO-34 in C3H6-SCR

Herein, Cu-modified SAPO-34 catalysts with various copper loadings are synthesized via a pH-controlled ion-exchange method. Cu exists predominantly as isolated cations at lower loadings, located at octahedrally coordinated sites in the ellipsoidal cavity of SAPO-34 zeolites, while CuO is gradually generated on the external surface at higher loadings. Our results reveal that the isolated Cu cations are the active sites for C3H6-SCR. The presence of CuO species enhances the C3H6 activation ability of the catalysts, which thus, improves the C3H6-SCR performance at medium and low temperatures (below 400 degrees C). At high temperatures, however, the formation of CuO accelerates the nonselective oxidation of C3H6 and causes activity decline. These findings suggest that the active temperature window for hydrocarbons-selective catalytic reduction (HC-SCR) reactions over Cu/SAPO-34 catalysts can be tailored by tuning the proportion of various copper species to fit the need in real applications, which provide new insights into understanding and designing highly efficient Cu-based zeolite catalysts.