Selective catalytic reduction of NOx by H2 over Pd/TiO2 catalyst

Pd/TiO2 catalysts prepared by three different methods (impregnation, deposition-precipitation, and polyethylene glycol reduction) were investigated in the selective catalytic reduction of NOx by H-2 (Hz-SCR). It was found that the preparation method exerted a significant effect on the activity of the Pd/TiO2 catalyst, and that the catalyst prepared by the polyethylene glycol reduction method exhibited the highest activity in the reduction of NOx. Characterization of the catalyst showed that, in the Pd/TiO2 catalyst prepared by the polyethylene glycol reduction method, the existing Pd species was Pd-0, which is the desirable species for the Hz-SCR of NOx. In situ DRIFTS studies demonstrated that over this catalyst, more chelating nitrite and monodentate nitrite species formed, both of which are reactive intermediates in the Hz-SCR of NOx. All of these factors account for the high activity of Pd/TiO2 prepared by the polyethylene glycol reduction method. (C) 2019, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.