No abstract

A series of Mn-exchanged SAPO-34 catalysts were synthesized and developed as catalysts for the low temperature selective catalytic reduction (SCR) of NO with ammonia in the presence of excess oxygen.

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.