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

摘要

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.