Promotion of catalytic performance by adding Cu into Pt/ZSM-5 catalyst for selective catalytic oxidation of ammonia

Abstract

The selective catalytic oxidation of ammonia (NH3-SCO) catalysts Pt/ZSM-5 and PtCu/ZSM-5 were prepared by impregnation method. Differences in textural, structural, morphological, acidic and reduction property, together with the catalytic performance of catalysts were investigated systematically. The results revealed that the introduction of Cu induced the adjustment of Pt states. Detailedly, the results of H2-TPR and XPS displayed the superior reduction property and more electron-rich of Pt species on the surface of PtCu/ZSM-5 rather than Pt/ZSM-5. And the average particle sizes of Pt species were decreased from 12.4 nm to 6.2 nm and the dispersion of Pt species was enhanced by introducing Cu into Pt/ZSM-5. Moreover, the acid types and acidity were modified by the addition of Cu species at some extent from NH3 adsorption of in situ DRIFTS. The larger amounts of NH3 absorbed on Brønsted acid sites were observed over PtCu/ZSM-5, which could transfer to the Lewis acid sites and promote the ammonia activation. Furthermore, Cu species also as the active species of selective catalytic reduction NO by NH3 (NH3-SCR) were able to improve N2 selectivity. It consequently resulted in enhanced NH3-SCO catalytic performance over PtCu/ZSM-5, its light-off temperature of NH3 was 212 °C and the maximum N2 selectivity (80%) was obtained at 225 °C, obviously better than that of Pt/ZSM-5.