Industrial-use catalysts usually encounter severe deactivation after long-term operation for catalytic oxidation of chlorinate volatile organic compounds (CVOCs), which becomes a "bottleneck" for large-scale application of catalytic combustion technology. In this work, typical acidic solid-supported catalysts of MnCeO/HZSM-5 were investigated for the catalytic oxidation of chlorobenzene (CB). The activation energy (E), Brønsted and Lewis acidities, CB adsorption and activation behaviors, long-term stabilities, and surficial accumulation compounds (after aging) were studied using a range of analytical techniques, including XPS, H-TPR, pyridine-IR, DRIFT, and O-TP-Ms. Experimental results revealed that the Brønsted/Lewis (B/L) ratio of MnCeO/HZSM-5 catalysts could be adjusted by ion exchange of H• (in HZSM-5) with Mn (where the exchange with Ce did not distinctly affect the acidity); the long-term aged catalysts could accumulate ca. 14 organic compounds at surface, including highly toxic tetrachloromethane, trichloroethylene, tetrachloroethylene, o-dichlorobenzene, etc.; high humid operational environment could ensure a stable performance for MnCeO/HZSM-5 catalysts; this was due to the effective removal of Cl• and coke accumulations by HO washing, and the distinct increase of Lewis acidity by the interaction of HO with HZSM-5. This work gives an in-depth view into the CB oxidation over acidic solid-supported catalysts and could provide practical guidelines for the rational design of reliable catalysts for industrial applications.

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The synergistic control of multipollutants is the frontier of environmental catalysis. This research is in the infancy stage, and many uncertainties still remain. Herein, we investigated the reaction characteristics of synergistic elimination of NO x and chloroaromatics on a commercial V2O5–WO3/TiO2 catalyst. The reaction byproducts were qualitatively and quantitatively analyzed, and their origins were clarified. In particular, the origins of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) from the synergistic reaction with or without SO2 were first explored; this is crucial for assessing the environmental risk by applying such a synergistic system. Experimental results indicate that during the synergistic reaction, the V2O5–WO3/TiO2 catalyst was deactivated at 200 and 250 °C, whereas the 300 °C was sufficient to durably convert the NO and chlorobenzene at the turnover frequency (TOF) of 7.23 × 10–4 and 1.32 × 10–4 s–1, respectively. A range of aromatics, alkenes, and alkanes, particularly their chlorinated congeners, were observed in the off-gases and on the catalyst surface, where those of 3-chlorobenzonitrile, 4-chloro-2-nitrophenol, and inorganic CS2 were first discovered. In the time-on-stream test at 250 °C, the PCDD/Fs collected from the off-gases was measured at 0.0514 ng I-TEQ Nm–3, but the most toxic dioxins congener, 2,3,7,8-TCDD, was not observed. The alkalinity of selective catalytic reduction reaction likely facilitated the chlorophenol formation, which eventually promoted PCDD/F generation. The SO2 was found to benefit polychlorinated byproduct generation, but the addition of which distinctly inhibited PCDD/F formation.

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