Controlled gas-phase presulfation on manganese oxide for catalytic oxidation of chlorobenzene: quantifying sulfate deposition–driven deactivation and acid-wash regeneration

Chlorinated volatile organic compounds (CVOCs), such as chlorobenzene, are highly toxic and persistent, with low-temperature catalytic oxidation being a key abatement strategy. However, SO 2 often coexists with CVOCs in industrial flue gases, leading to sulfur poisoning of Mn-based oxides. The effectiveness and limits of catalyst regeneration remain unclear. In this study, Mn 2 O 3 is used as a model catalyst, and a controllable gas-phase presulfation strategy is proposed to construct a “fresh–poisoned–regenerated” tri-state system for evaluating surface sulfur species. Fresh Mn 2 O 3 -F shows low light-off temperatures for chlorobenzene oxidation (T 50  = 278 °C, T 90  = 326 °C), but SO 2 pretreatment significantly reduces activity, with increasing SO 2 concentrations further inhibiting the reaction. None of the presulfated samples reach 90% conversion within the tested temperature window. After acid regeneration, sulfur content decreases from 2.37 wt% to 1.30 wt%, leading to partial recovery of activity (T 90 rises to 375 °C, Ea decreases to 59.36 kJ/Mol). In situ DRIFTS reveals that SO 2 forms stable surface sulfates, which block active sites, occupy oxygen vacancies, and hinder lattice oxygen migration, resulting in partial deactivation. The regeneration process removes weakly bound sulfur species, but residual sulfates and structural changes limit full recovery. This work provides a framework for evaluating sulfur-tolerant design and regeneration pathways for Mn-based catalysts.