The promotion effect of manganese on Cu/SAPO for selective catalytic reduction of NO(x) with NH(3)

The activity and hydrothermal stability of Cu/SAPO and xMn–2Cu/SAPO for low-temperature selective catalytic reduction of NO(x) with ammonia were investigated. An ion-exchanged method was employed to synthesize xMn–2Cu/SAPO, which was characterized by N(2) adsorption, ICP-AES, X-ray diffraction (XRD), NH(3)-temperature programmed desorption (NH(3)-TPD), NO oxidation, X-ray photoelectron spectrum (XPS), UV-vis, H(2)-temperature programmed reduction (H(2)-TPR) and diffuse reflectance infrared Fourier transform spectra (DRIFTS). 2Mn–2Cu/SAPO and 4Mn–2Cu/SAPO showed the best SCR activity, in that at 150 °C NO conversion reached 76% and N(2) selectivity was above 95% for the samples. NO oxidation results showed that the 2Mn–2Cu/SAPO had the best NO oxidation activity and the BET surface area decreased as manganese loading increased. XRD results showed that the metal species was well dispersed. NH(3)-TPD showed that the acid sites have no significant influence on the SCR activity of xMn–2Cu/SAPO. H(2)-TPR patterns showed good redox capacity for xMn–2Cu/SAPO. UV-vis and H(2)-TPR showed that the ratio of Mn(4+) to Mn(3+) increased as manganese loading increased. XPS spectra showed a significant amount of Mn(3+) and Mn(4+) species on the surface and addition of manganese increased the ratio of Cu(2+). The promotion effect of manganese to 2Cu/SAPO comes from the generation of Mn(3+) and Mn(4+) species. Deduced from the DRIFTS spectra, the Elay–Rideal mechanism was effective on 4Mn–2Cu/SAPO.