The catalytic performances and reaction mechanism of nanoparticle Cd/Ce-Ti oxide catalysts for NH3-SCR reaction

Ce-0.3-TiOx nanoparticle carrier was prepared by the sol-gel method, and a series of Cd-Ce-Ti nanoparticle catalysts with variable Cd contents were prepared by the means of an improved incipientwetness impregnation. The catalysts were characterized by means of XRD, N-2 adsorption-desorption analysis, SEM, TEM, NH3-TPD and in situ DRIFTS. The catalytic activities for deNOx were evaluated by NH3-SCR reaction. All these nanoparticle catalysts contain mesopores with a pore size around 7 nm, and the average particle size is 20 nm. Among the catalysts, 2 wt% Cd/Ce0.3TiOx catalyst exhibits the best NH3-SCR performance with a wide temperature window of 250-400 degrees C for NO conversion above 90%. Moreover, in situ DRIFTS spectra of NOx reduction over 2 wt% Cd/Ce0.3TiOx catalyst were also investigated. The results show that this reaction mainly follows the Langmuir-Hinshelwood mechanism at room temperature, while Eley-Rideal mechanism plays more important role when the reaction temperature is higher than 150 degrees C. The adsorbed NH3 coordinately linked to Lewis acid site is easy to react with NOx at high temperature.