Boosting the catalytic performance of Cu-SAPO-34 in NO removal via hydrothermal treatment.

Phosphate ions promoted Cu-SAPO-34 (P-Cu-SAPO-34) were prepared using bulk CuO particles as Cu precursor by a solid-state ion exchange technique for the selective catalytic reduction of NO with NH (NH-SCR). The effects of high temperature (H-T) hydrothermal aging on the NO removal (de-NO) performance of Cu-SAPO-34 with and without phosphate ions were systematically investigated at atomic level. The results displayed that both Cu-SAPO-34 and P-Cu-SAPO-34 presented relatively poor NO removal activity with a low conversion (< 30%) at 250-500°C. However, after H-T hydrothermal treatment (800°C for 10 hr at 10% HO), these two samples showed significantly satisfied NO elimination performance with a quite high conversion (70%-90%) at 250-500°C. Additionally, phosphate ions decoration can further enhance the catalytic performance of Cu-SAPO-34 after hydrothermal treatment (Cu-SAPO-34H). The textural properties, morphologies, structural feature, acidity, redox characteristic, and surface-active species of the fresh and hydrothermally aged samples were analyzed using various characterization methods. The systematical characterization results revealed that increases of 28% of the isolated Cu active species (Cu-2Z, Cu (OH)-Z) mainly from bulk CuO and 50% of the Brønsted acid sites, the high dispersion of isolated Cu active component as well as the Brønsted acid sites were mainly responsible for the accepted catalytic activity of these two hydrothermally aged samples, especially for P-Cu-SAPO-34H.