Cu/SAPO-34 prepared by a facile ball milling method for enhanced catalytic performance in selective catalytic reduction of NOx with NH3

Cu/SAPO-34 catalysts were prepared by different solid-state ion exchange methods, i.e., mechanical mixing (Cu/SAPO-34-M) and ball milling (Cu/SAPO-34-B), and were used for selective catalytic reduction of NOx with NH3 (NH3-SCR) reaction. Compared with Cu/SAPO-34-M, Cu/SAPO-34-B exhibited more excellent NH3-SCR catalytic activity. Various characterization methods, including XRD, SEM, N2 adsorption-desorption, UV-vis, H2-TPR, EPR, NO + O2-TPD, NH3-TPD, and in situ DRIFTS, were used to elucidate these different catalytic performance. The characterization results suggested that ball milling could benefit to increase the amount of isolated Cu2+ ions in Cu/SAPO-34 catalyst. In comparison with Cu/SAPO-34-M, Cu/SAPO-34-B had more isolated Cu2+ ions, which mainly contributed to the NOx adsorption and Lewis acid sites. Furthermore, ball milling could improve the redox property of Cu/SAPO-34 catalyst. The in situ DRIFTS results verified that NH3 adsorbed on Lewis acid sites were more active than that adsorbed on Bronsted acid sites. Therefore, it was believed that ball milling was a proper method to prepare more efficient Cu/SAPO-34 catalyst for NOx removal from diesel exhaust.