The influence of H2O and SO2 on the mechanism of CO oxidation over low noble metal loading catalysts

Abstract

Noble metal catalysts exhibit high efficiency and stability in CO removal, but their high loading of noble metals led to elevated costs, limiting industrial applications. This study selected three representative noble metals (Pt, Au, Ru) to investigate the CO reaction mechanisms on low-loading noble metal catalysts and the effects of SO₂/H₂O on CO oxidation. Catalysts with 0.1 wt% metal loading were synthesized via the impregnation method using conventional TiO₂ as the support, denoted as 0.1Pt/Ti, 0.1Au/Ti and 0.1Ru/Ti. Among them, 0.1Pt/Ti achieved complete CO conversion at 270 °C and maintained 100% conversion over 46 h of continuous operation at 250 °C in the presence of SO₂ and H₂O. In situ DRIFTS indicated that the CO reaction over all catalysts followed the Mars–van Krevelen (MvK) mechanism. However, both Langmuir–Hinshelwood (L–H) and MvK pathways coexisted on 0.1Pt/Ti, with the L–H mechanism being dominant. DFT calculations revealed that CO also exhibited a higher adsorption preference for the 0.1Pt/Ti catalyst, which was identified as the primary reason for its superior performance.