Study on the mechanism of NH-selective catalytic reduction over CuCeZr/TiO.

Copper-cerium-zirconium catalysts loaded on TiO prepared by a wet impregnation method were investigated for NH-selective catalytic reduction (SCR) of NO. The reaction mechanism was proposed on the basis of results from in situ diffuse reflectance infrared transform spectroscopy (DRIFT). When NH3 is introduced, ammonia bonded to Lewis acid sites is more stable over CuCeZr/TiO at high temperature, while Brønsted acid sites are more important than Lewis acid sites at low temperature. For the NH+NO+O co-adsorption, NH3 species occupy most of activity sites on CuCeZr/TiO catalyst, and mainly exist in the forms of NH (at low temperature) and NH coordinated (at high temperature), playing a crucial role in the NH-SCR process. Two different reaction routes, the L-H mechanism at low temperature (< 200°C) and the E-R mechanism at high temperature (> 200°C), are presented for the SCR reaction over CuCeZr/TiO catalyst. [ABSTRACT FROM AUTHOR]