Abstract: CeO₂-MnO_x catalyst samples with different Mn/(Ce+Mn) molar ratios (0, 1/4, 1/2, 3/4, and 1) prepared by the citric acid (CA) sol-gel method were studied for catalytic combustion of vinyl chloride (VC) emission. The effects of preparation conditions and operation parameters on the catalytic performance of CeO₂-MnO_x were investigated. The catalyst samples were characterized by N₂ adsorption, X-ray diffraction (XRD), and H₂ temperature-programmed reduction (H₂-TPR). In the catalytic combustion of VC over CeO₂-MnO_x, the products containing HCl, CO₂, and H₂O were produced and there were no byproducts such as chlorohydrocarbons and chlorine. The CeO₂-MnO_x catalyst with the molar ratio of CA:Mn:Ce = 0.30:0.50:0.50 showed the best catalytic performance and had better operating flexibility over the ranges of gas hourly space velocity (GHSV) of 10000–30000 h^-1 and VC concentration of 0.05%–0.15%. The temperatures at 50% conversion (110 ^oC) and at 99% conversion (220 ^oC) were achieved at VC concentration of 0.1% and GHSV of 15000 h^-1. XRD characterization indicated that only the characteristic diffraction peaks of CeO₂ with the cubic fluorite structure appeared and no characteristic diffraction peaks of MnO_x species appeared over CeO₂-MnO_x catalyst. XRD and H₂-TPR results indicated that Mn ions were incorporated into the CeO₂ lattice to form Ce-Mn-O solid solution, which was favorable for improving the reactivity of active oxygen species on the catalyst surface and thereby enhanced the catalyst activity.

Key words: cerium, manganese, composite oxide, vinyl chloride, catalytic combustion, solid solution, oxygen species