Chemical deactivation of Cu-SAPO-18 deNOx catalyst caused by basic inorganic contaminants in diesel exhaust

Abstract Contaminants (K, Na, Ca, and Mg) were introduced into Cu-SAPO-18 via incipient wetness impregnation to investigate their effect on the selective catalytic reduction of NO x with NH 3 (NH 3 -SCR) over Cu-SAPO-18. After the introduction of contaminants into Cu-SAPO-18, the quantity of acidic sites and Cu 2+ species in catalyst decreases owing to the replacement of H + and Cu 2+ by K + , Na + , Ca 2+ , and Mg 2+ . Furthermore, the loss of isolated Cu 2+ induces the generation of CuO and CuAl 2 O 4 -like phases, which causes further loss in the Brunauer-Emmett-Teller surface area of the catalyst. Consequently, the deNO x performance of the contaminated Cu-SAPO-18 catalysts drops. Such decline in NH 3 -SCR performance becomes more pronounced by increasing the contaminant contents from 0.5 to 1.0 mmol/g catal . In addition, the deactivation influence of the contaminants on Cu-SAPO-18 is presented in the order of K> Na > Ca > Mg, which is consistent with the order of reduction of acidic sites. To a certain degree, the effect of the acidic sites on the deactivation of Cu-SAPO-18 might be more significant than that of isolated Cu 2+ and the catalyst framework. Moreover, kinetic analysis of NH 3 -SCR was conducted, and the results indicate that there is no influence of contaminants on the NH 3 -SCR mechanism.