Effect of Chemical and Physical Properties of Titanium Oxide Support Surface during Nitrogen Monoxide Reduction by Carbon Monoxide in Presence Water over Titanium Oxide Supported Platinum Catalyst

Abstract

With the goal of developing a method for utilizing reactive nitrogen species emitted from combustion processes as raw materials for the synthesis of useful compounds, we investigated the selective conversion of NOx to NH3 by means of the NO–CO–H2O reaction over Pt/TiO2 catalysts. High NH3 selectivity was obtained for high-specific-surface-area catalysts. Catalytic activity tests revealed that the activities of catalysts depended on the crystal structure of the support. Comparing CO conversion between NO–CO–H2O reaction and CO–H2O reaction, which could play a role of H-supply reaction, Pt/TiO2 exhibited higher CO conversion for the NO–CO–H2O reaction than that for CO–H2O reaction except for high-surface-area anatase TiO2-supported catalyst around 200 °C. We focused on how the chemical and physical properties of the catalyst surface. Specifically, we carried out temperature-programmed desorption of CO2, which revealed that the CO2 formed during the NO–CO–H2O reaction had no effect on the difference in activity. Carbonaceous surface species and NHx species were observed on the surface of Pt/TiO2 catalyst during NO–CO–H2O reaction by diffused reflectance infrared Fourier transform spectroscopy, and difference in formate formation on anatase-TiO2 supported Pt catalyst was confirmed compared to rutile-TiO2 supported Pt catalyst. We supposed that the difference in activity between anatase and rutile TiO2 was caused by behavior of formate formation.