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

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 NO_x species by NH₃ (i-SCR) and (2) selective catalytic reduction of NO_x 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 NO_x via reaction with stored imide, amide (–NH_x) 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.