Enhancing the low temperature NH-SCR activity of FeTiO catalysts Cu doping: a combination of experimental and theoretical study.

A series of Fe Cu TiO catalysts with variable Cu doping amounts was directly synthesized by the sol-gel method and their catalytic performances were tested for the selective catalytic reduction of NO with ammonia. The highest activity was achieved on FeCuTi catalyst. NO conversion was above 80% and N selectivity exceeded 90% on this catalyst in the temperature range of 200-375 °C. High NO and NH oxidation activities facilitated the high NH-SCR activities of the catalysts in the low temperature range, while too strong NH oxidation ability resulted in the decline of NH-SCR activity. DFT calculations based on the Fe and Cu co-doping TiO model showed that the barrier of NH activation is dramatically reduced as compared to pure Fe doping. This is due to the lowered p-band of lattice O. However, such activated O will also strongly decrease the barrier for the dissociation of NH to NH species, which will lead to the formation of NO. Both Brønsted and Lewis acid sites over FeCuTi catalyst are involved in the NH-SCR reaction. The adsorption of NO is strong in the low temperature range, and large amounts of nitrates were decomposed on the catalyst surface in the high temperature range.