Effect of La/Ce modification over Cu based Y zeolite catalysts on high temperature selectivity for selective catalytic reduction with ammonia

Abstract

CuY zeolite catalyst is considered to be one of most promising catalysts for selective catalytic reduction with ammonia (NH3-SCR), but its main byproduct is the greenhouse gas N2O. To increase N2 selectivity, the modification mode and promotion mechanism of La/Ce doping with two-step ion exchange method were investigated. Impressively, CuLaY achieved above 90% efficiency from 140 °C to 380 °C and less N2O production especially at the temperature above 250 °C. The characterization results showed La/Ce doping increased the content of surface Cu2+ species and improved the oxidation ability of Cu ions in catalysts. However, the formation of La/Ce oxides on the zeolite surface had an adverse impact on the SCR activity, while Ce oxides were more easily formed than La oxides. In addition, more abundant adsorbed NOx species and stronger NH3 adsorption on the surfaces enhanced L-H mechanism for CuLaY with high N2 selectivity above 250 °C.