H2O and/or SO2 Tolerance of Cu-Mn/SAPO-34 Catalyst for NO Reduction with NH3 at Low Temperature

A series of molecular sieve catalysts (Cu-Mn/SAPO-34) with different loadings of Cu and Mn components were prepared by the impregnation method. The deNO(x) activity of the catalyst was investigated during the selective catalytic reduction (SCR) of NO with NH3 in the temperature range of 120 degrees C to 330 degrees C, including the effects of H2O vapors and SO2. In order to understand the poisoning mechanism by the injection of H2O and/or SO2 into the feeding gas, the characteristics of the fresh and spent catalyst were identified by means of Brunner-Emmet-Teller (BET), X-ray Diffraction (XRD), Scanning Electronic Microscopy (SEM) and Thermal Gravity- Differential Thermal Gravity (TG-DTG). The conversion of NO by the catalyst can achieve at 72% under the reaction temperature of 120 degrees C, while the value reached more than 90% under the temperature between 180 degrees C and 330 degrees C. The deNO(x) activity test shows that the H2O has a reversible negative effect on NO conversion, which is mainly due to the competitive adsorption of H2O and NH3 on Lewis acid sites. When the reaction temperature increases to 300 degrees C, the poisoning effect of H2O can be negligible. The poisoning effect of SO2 on deNO(x) activity is dependent on the reaction temperature. At low temperature, the poisoning effect of SO2 is permanent with no recovery of deNO(x) activity after the elimination of SO2. The formation of (NH4)(2)SO4, which results in the plug of active sites and a decrease of surface area, and the competitive adsorption of SO2 and NO should be responsible for the loss of deNO(x) activity over Cu/SAPO-34.