Selective Catalytic Reduction of NO_x with C_2H_6 under lean-burn conditions on activated carbon-supported metals

摘要

The Selective Catalytic Reduction of NO_x with C_3H_6 under excess of oxygen has been investigated using different transition metals supported on a carbonaceous material. For this purpose, 1 wt percent Pt, Pd, Fe, Co, Ni and Cu supported on an activated carbon, ROXN, have been tested by Temperature Programme Reaction (TPR). A gas mixture containing 1000 ppm of NO, 1500 ppm of C_3H_6 and 5 vol. percent of O_2 (SV=3600 h`-1) has been used to carry out the experiments. In terms of NO_x conversion and N_2 selectivity, a diversity of behaviours have been obtained. Pt/POXN presents the highest NO_x conversion, almost 100 percent, but exhibits a moderate N_2 selectivity. On the other hand, Fe/ROXN presents a 100 percent N_2 selectivity, but exhibits low NO_x conversions. The results have been discussed attending to the characteristics of the active phase and to the behaviour of the catalysts for C_3H_6 combustion. Conventioanl alumina-supported catalysts have been used for comparative purposes: an identical activity trend has been obtained for the studied metals. Nevertheless, the activated carbon-supported metal catalysts show two advantages; i) higher NO_x conversions at lower temperatures and ii) the achievement of their maximum values for N_2 selectivities, which are similar to the obtained for the alumina-supported catalysts, at lower temperatures.