Comparative Investigation on Chlorobenzene Oxidation by Oxygen and Ozone over a MnOx/Al2O3 Catalyst in the Presence of SO2

241

Volatile organic compounds (VOCs) are one of the main sources of air pollution, which are of wide concern because of their toxicity and serious threat to the environment and human health. Catalytic oxidation has been proven to be a promising and effective technology for VOCs abatement in the presence of heat or light. As environmentally friendly and low-cost materials, manganese-based oxides are the most competitive and promising candidates for the catalytic degradation of VOCs in thermocatalysis or photo/ thermocatalysis. This article summarizes the research and development on various manganesebased oxide catalysts, with emphasis on their thermocatalytic and photo/thermocatalytic purification of VOCs in recent years in detail. Single manganese oxides, manganese-based oxide composites, as well as improving strategies such as morphology regulation, heterojunction engineering, and surface decoration by metal doping or universal acid treatment are reviewed. Besides, manganese-based monoliths for practical VOCs abatementare also discussed. Meanwhile, relevant catalytic mechanisms are also summarized. Finally, the existing problems and prospect of manganese-based oxide catalysts for catalyzing combustion of VOCs are proposed.

Section: Mn-based Oxide Thermocatalysts For Vocs Purificationmentioning

confidence: 99%

Recent Progress of Thermocatalytic and Photo/Thermocatalytic Oxidation for VOCs Purification over Manganese-based Oxide Catalysts

Jin

Qiu

et al. 2021

241

“…As one of the typical chlorinated volatile organic compounds (Cl-VOCs), dichloromethane (DCM, CH 2 Cl 2 ) emitted from steel sintering, smelting, solid waste treatment, glass manufacture, and organic synthesis is an important precursor of aerosols, particle matter (PM), and photochemical smog. , Currently, catalytic oxidation of DCM into harmless CO 2 /H 2 O and soluble acid gas (HCl/Cl 2 ) at 200–500 °C attains remarkable environmental significance due to lower cost and less hazardous byproducts . However, the DCM molecule containing dominant C–H bonds with high dissociation energy requires higher degradation temperature. − Furthermore, the accumulation of chlorinated intermediates during catalytic oxidation of DCM induces catalyst deactivation. , Fortunately, ozone-enhanced catalytic oxidation alleviates the above problems to attain low temperature (<150 °C) elimination of Cl-VOCs with high Cl resistance and inhibition of chlorinated byproducts, which is also named catalytic ozonation. , It also exhibits low ozone escape under optimal conditions; therefore, synergetic elimination of Cl-VOC and O 3 can be achieved.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the Flexibility for Catalytic Ozonation of Dichloromethane over Urchin-Like CuMnO_x in Flue Gas with Complicated Components

Lin

Cai

et al. 2022

Self Cite

The evaluation of the poisoning effect of complex components in practical gas on DCM (dichloromethane) catalytic ozonation is of great significance for enhancing the technique’s environmental flexibility. Herein, Ca, Pb, As, and NO/SO2 were selected as a typical alkaline-earth metal, heavy metal, metalloid, and acid gas, respectively, to evaluate their interferences on catalytic behaviors and surface properties of an optimized urchin-like CuMn catalyst. Ca/Pb loading weakens the formation of oxygen vacancies, oxygen mobility, and acidity due to the fusion of Mn–Ca/Pb–O, leading to their inferior catalytic performance with poor CO2 selectivity and mineralization rate. Noticeably, the presence of As induces excessively strong acidity, facilitating the inevitable formation of byproducts. Catalytic co-ozonation of NO/DCM is achieved with stoichiometric ozone addition. Unfortunately, SO2 introduction brings irreversible deactivation due to strong competition adsorption and the loss of active sites. Unexpectedly, Ca loading protects active sites from an attack by SO2. The formation of unstable sulfites and the released Mn–O structure offset the negative effect from SO2. Overall, the catalytic ozonation of DCM exhibits a distinctive priority in the antipoisoning of metals with the maintenance of DCM conversion. The construction of more stable acid sites should be the future direction of catalyst design; otherwise, catalytic ozonation should be arranged together with post heavy metal capture and a deacidification system.

“…While the highly electronegative Pt species can provide the active sites for VOC adsorption and oxygen activation, the adjacent promoter (Sn–O) can function as acid sites in such bimetallic catalysts . The monomeric SnO x species can form both Brønsted and Lewis acid sites, which provide sufficient protons for HCl formation, maintaining the reactivity of the Pt surface by removing Cl as well as the formation of more oxygen vacancies as active sites for the C–Cl bond dissociation . Therefore, the desorption amount of HCl at low temperatures from the Pt–O–Sn-like bimetallic catalyst is much larger than that from the Pt/CeO 2 catalyst (Figure , ( o -xylene + TCE)-TPD).…”

Section: Discussionmentioning

confidence: 99%

Engineering Platinum Catalysts via a Site-Isolation Strategy with Enhanced Chlorine Resistance for the Elimination of Multicomponent VOCs

Gao

Zhang

Liu

et al. 2022

Pt-based catalysts can be poisoned by the chlorine formed during the oxidation of multicomponent volatile organic compounds (VOCs) containing chlorinated VOCs. Improving the low-temperature chlorine resistance of catalysts is important for industrial applications, although it is yet challenging. We hereby demonstrate the essential catalytic roles of a bifunctional catalyst with an atomic-scale metal/oxide interface constructed by an intermetallic compound nanocrystal. Introducing trichloroethylene (TCE) exhibits a less negative effect on the catalytic activity of the bimetallic catalyst for o-xylene oxidation, and the partial deactivation caused by TCE addition is reversible, suggesting that the bimetallic, HCl-etched Pt3Sn(E)/CeO2 catalyst possesses much stronger chlorine resistance than the conventional Pt/CeO2 catalyst. On the site-isolated Pt–Sn catalyst, the presence of aromatic hydrocarbon significantly inhibits the adsorption strength of TCE, resulting in excellent catalytic stability in the oxidation of the VOC mixture. Furthermore, the large amount of surface-adsorbed oxygen species generated on the electronegative Pt is highly effective for low-temperature C–Cl bond dissociation. The adjacent promoter (Sn–O) possesses the functionality of acid sites to provide sufficient protons for HCl formation over the bifunctional catalyst, which is considered critical to maintaining the reactivity of Pt by removing Cl and decreasing the polychlorinated byproducts.