Simultaneous catalytic removal of NOx and soot particulates over CuMgAl hydrotalcites derived mixed metal oxides

Abstract

A series of CuMgAl hydrotalcites derived oxides were prepared by co-precipitation and calcination methods and tested for the simultaneous catalytic removal of NOx and soot. The obtained samples were characterized by XRD, N 2 adsorption-desorption, H 2-TPR and ICP-AES techniques. The crystal phases, porous structures and redox properties of the catalysts were strongly influenced by Cu substitution contents and calcination temperatures. The CuMgAl mixed oxides with mesoporous properties exhibit high activity for the simultaneous NOx-soot removal. Among the tested catalysts, 3.0Cu-800 sample shows the best performance with the ignition temperature of soot = 260 °C and the total amounts of N 2 = 6.0 × 10 − 5 mol. Based on the experimental work, a primitive kinetics analysis was carried out from the non-steady (dynamic) TPR measurements. Linear Arrhenius plots of rates of CO 2, N 2 and N 2O formation were observed around the onset of formation curves where the substantial amount of the soot still remains in the soot/catalyst mixture and the effective area of the soot/catalyst contact can be regarded as constant. Finally, a compensation effect was found for the formation of CO 2, N 2 and N 2O over CuMgAl mixed oxides with CuO as the predominant phase.