CO oxidation over PdOσ/Fe1-xWxOy catalysts and their SO2 resistance at relatively low temperature

Efficient sulfur-tolerant catalysts for purification in sulfur-containing steel sintering flue gas remain a severe challenge. Herein, a series of Fe2O3 modified by WO3-supported PdOσ was fabricated to make progress in this issue. WO3 decoration decreases Pd dispersion but significantly enhances the sulfur resistance of PdOσ/Fe2O3 for CO catalytic oxidation. Typically, at an SO2 concentration as high as 1000 ppm, the optimal PdOσ/Fe0.6W0.4Oy can keep its activity with a CO conversion of 90% even at relatively low temperatures (175 °C) for 20 h, which was superior to most reported catalysts. As evidenced by systematical surface properties and kinetic analysis, this accepted sulfur tolerance was closely related to the enhanced amount of surface acid sites and the formation of a new phase of FeWO4 from the strong interaction of FeOx and WO3, which could suppress SO2 adsorption and decrease the deposition of the undesirable sulfate (S6+). Additionally, PdO2 (4+) appears to be more resistant to sulfur than PdO (2+), probably due to the latter palladium species being more likely to react with sulfur. Also, WO3 modification induced the chemical state of sulfur component changing from S6+ to S4+, thereby preserving PdO2 (4+) catalytic activity species and showing remarkable performance of sulfur tolerance.