Catalytic Reduction of NOx With NH3 Over CeO2 and SiO2 Supported Tungstophosphoric Acid: Promoting Effects of Ceria Support and Cobalt Proton Substitute

Grafted tungstophosphoric acid (H3PW12O40/ HPW) is applied as a catalyst in the selective catalytic reduction of NOx with NH3 (NH3-SCR). The HPW/CeO2 catalyst has been found to be effective in the SCR reaction compared to HPW/SiO2. The cobalt-exchanged HPW/CeO2 improved NOx conversion, which reached 98% over a wide operating temperature window (280–500 °C). The better NOx performance of the CoPW/CeO2 catalyst is mainly due to the higher dispersion of tungsten on the CeO2 support, the formation of oxygen vacancies and the production of nitrogenous species. Incorporation of vanadium decreased the acidity of HPW, which reduced SCR activity on the HPVW/CeO2 catalyst.