Effect of preparation procedure and composition of catalysts based on Mn and Ce oxides in the simultaneous removal of NOX and o-DCB

Abstract

Two series of catalysts based on Mn and Ce oxides were prepared by co-precipitation and impregnation, in order to study their physicochemical properties and catalytic performance in the simultaneous reduction of NO and oxidation of o-DCB. Co-precipitation catalysts showed better activity than those prepared by impregnation because of the formation of a MnOX-CeO2 solid solution, which improves redox and acid properties. Moreover, the catalysts with MnOX content between 80 and 90 mol.%, in which a coexistence between solid solution phase and Mn2O3 crystal was found, presented NO conversion above 90 % at temperatures below 250 °C and o-DCB conversion above 80 % at temperatures above 200 °C. The main by-products of SCR were N2O, produced in the whole range of temperature, and NO2, formed at temperatures above 300 °C. Selectivity to CO2 above 80 % was obtained using co-precipitation catalysts in all temperature range. Deactivation experiments showed that oxidation reaction strongly contributes to deactivate impregnation catalysts, whereas the effect of deactivation is lower in co-precipitation catalysts at high Mn contents.