Performance of Modified VWTi Catalysts on Naphthalene Oxidation in SO ₂ -Containing Flue Gas

Naphthalene was the primary component of polycyclic aromatic hydrocarbons (PAHs) from coal-fired flue gas. The Cu-doped VWTi catalyst with CTAB-remodification was prepared by sol–gel method, and its naphthalene oxidation activity was assessed, which exhibited the CO2 yield of approximately 65% and naphthalene conversion rate of 100% at 320 °C. Moreover, the naphthalene degradation under different SO2 concentrations was explored in depth, where SO2 rarely affected the naphthalene conversion but caused an obvious decline in CO2 generation. Significantly, the SO2 poisoning characteristics of the modified VWTi catalyst were explained by a series of characterization techniques such as FTIR, TG, XRD, N2 adsorption–desorption isotherms, SEM, XPS, H2-TPR, EPR, and in situ DRIFTS. Results illustrated that SO2 was oxidized to SO3, and the formed metal sulfates were adhered to the catalyst surface, which could clog the catalyst pores, cover the active sites, break the surface lattice oxygen, and cut down the low-temperature reduction performance. The introduction of SO2 tended to consume more active metals (V5+, W6+, and Cu+) and oxygen vacancies, resulting in the production of more basic hydroxyl groups. This promoted the chemisorption to naphthalene, restrained its deep oxidation to CO2, and led to the accumulation of more anhydride byproducts on the catalyst surface. This work provided insights into the SO2 poisoning mechanism of naphthalene oxidation on VWTi-based catalysts.