The promotion effect of manganese on Cu/SAPO for selective catalytic reduction of NO with NH.

The activity and hydrothermal stability of Cu/SAPO and Mn-2Cu/SAPO for low-temperature selective catalytic reduction of NO with ammonia were investigated. An ion-exchanged method was employed to synthesize Mn-2Cu/SAPO, which was characterized by N adsorption, ICP-AES, X-ray diffraction (XRD), NH-temperature programmed desorption (NH-TPD), NO oxidation, X-ray photoelectron spectrum (XPS), UV-vis, H-temperature programmed reduction (H-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 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-TPD showed that the acid sites have no significant influence on the SCR activity of Mn-2Cu/SAPO. H-TPR patterns showed good redox capacity for Mn-2Cu/SAPO. UV-vis and H-TPR showed that the ratio of Mn to Mn increased as manganese loading increased. XPS spectra showed a significant amount of Mn and Mn species on the surface and addition of manganese increased the ratio of Cu. The promotion effect of manganese to 2Cu/SAPO comes from the generation of Mn and Mn species. Deduced from the DRIFTS spectra, the Elay-Rideal mechanism was effective on 4Mn-2Cu/SAPO.