Synergistic effects of lattice defects and acid sites in ZrMnOX catalysts on efficient chlorobenzene catalytic oxidation: enhanced oxidation activity and chlorine resistance

Abstract

The efficient mineralization of chlorinated volatile organic compounds (CVOCs) and the suppression of polychlorinated by-product formation can be realized by modulating the redox capability and surface acid sites of α-Mn₂O₃ catalyst. M–MnO_X (M = Zr, Hf, and Y) catalysts with abundant lattice defect structures were synthesized via redox precipitation and employed for the catalytic oxidation of chlorobenzene (CB). Experimental characterizations demonstrate that Zr doping induces lattice distortion in α-Mn₂O₃, generating numerous defect sites that facilitate the formation and migration of surface oxygen species. The synergistic effect between the high concentration of active species and acid sites in the ZrMnO_X catalyst promotes the cleavage of the C–Cl bond and enables the removal of Cl species as inorganic chlorine. Compared with α-Mn₂O₃, ZrMnO_X exhibits superior catalytic activity for CB (500 ppm CB, GHSV = 30 000 mL g⁻¹ h⁻¹, T₉₀ = 237 °C, E_a = 28.23 kJ mol⁻¹) and generates fewer chlorinated by-products. Meanwhile, the reaction pathway of CB oxidation over ZrMnO_X, as revealed by in situ infrared spectroscopy, follows the Mars–van Krevelen (MVK) mechanism.