New insights into the influence mechanism of H2O and SO2 on Pt–W/Ti catalysts for CO oxidation

Abstract

A series of anatase TiO₂ catalysts loaded with 0.1 wt% Pt and n% WO₃ (0.1Pt–nW/Ti-A, n = 0, 1, 2, 5, and 10) were prepared via a two-step impregnation method. Among the catalysts, 0.1Pt–5W/Ti-A showed the best CO oxidation activity and outstanding stability in the presence of H₂O and SO₂. H₂O can significantly improve the catalytic oxidation efficiency of the catalyst, and doping of WO₃ apparently enhances the sulfur tolerance of the catalyst. The results of TEM, EDS, XRD and Raman analyses indicated that Pt and W both had a very high degree of dispersion in 0.1Pt–5W/Ti-A. XPS and H₂-TPR results showed that there was a certain effect between WO₃ and Pt, as well as between WO₃ and TiO₂. From XPS and SO₂-TPD results, it can be inferred that WO₃ doping inhibited the adsorption of SO₂, and the amount of S deposited on the catalyst surface did not increase with the reaction time. The results of in situ DRIFTS measurements and H₂¹⁸O isotope labeling experiments revealed that H₂O promoted the catalytic oxidation of CO through two paths. Consequently, the CO oxidation mechanism of 0.1Pt–5W/Ti-A in the presence of H₂O and SO₂ is proposed.