High N2 selectivity of Pt-V-W/TiO2 oxidation catalyst for simultaneous control of NH3 and CO emissions

Abstract

We report a superior N2 selectivity in the catalytic emission control of NH3 and CO over PtVW/TiO2 catalysts synthesized by the co-impregnation method. The PtVW/TiO2 selective oxidation catalyst (SCO) enabled the following surface reactions over bimetallic Pt-V sites: (1) selective catalytic reduction of internally generated NOx species by NH3 (i-SCR) and (2) selective catalytic reduction of NOx by the CO (CO-SCR) present in the feed gas. The enhanced N2 selectivity was characterized in terms of adsorbent behavior and catalyst surface properties as a function of the catalyst formulations. It was found that the strong interaction between the Pt and V metal species increased both the reducibility and the surface acidity of the catalyst, which could be a crucial factor in the enhancement of N2 selectivity. Surface IR measurement and DFT calculations relates these enhanced catalytic properties to the removal of the generated NOx via reaction with stored imide, amide (–NHx) and isocyanate (–NCO) species on the catalyst surface. These stored species enhance the N2 selectivity through the i-SCR and CO-SCR mechanisms. A dual-zoned bench-scale monolith reactor has been tested, with a commercial SCR (front) and the developed SCO (rear) in series. This dual-zoned system showed high N2 selectivity and outstanding CO and NH3 oxidation.