Efficient Catalytic Elimination of Chlorobenzene Based on the Water Vapor-Promoting Effect within Mn-Based Catalysts: Activity Enhancement and Polychlorinated Byproduct Inhibition.

Achieving no or low polychlorinated byproduct selectivity is essential for the chlorinated volatile organic compounds (CVOCs) degradation, and the positive roles of water vapor may contribute to this goal. Herein, the oxidation behaviors of chlorobenzene over typical Mn-based catalysts (MnO2 and acid-modified MnO2) under dry and humid conditions were fully explored. The results showed that the presence of water vapor significantly facilitates the deep mineralization of chlorobenzene and restrains the formation of Cl2 and dichlorobenzene. This remarkable water vapor-promoting effect was conferred by the MnO2 substrate, which could suitably synergize with the postconstructed acidic sites, leading to good activity, stability, and desirable product distribution of acid-modified MnO2 catalysts under humid conditions. A series of experiments including isotope-traced (D2O and H218O) CB-TPO provided complete insights into the direct involvement of water molecules in chlorobenzene oxidation reaction and attributed the root cause of the water vapor-promoting effect to the proton-rich environment and highly reactive water-source oxygen species rather than to the commonly assumed cleaning effect or hydrogen proton transfer processes (generation of active OOH). This work demonstrates the application potential of Mn-based catalysts in CVOCs elimination under practical application conditions (containing water vapor) and provides the guidance for the development of superior industrial catalysts.

Monolithic Catalyst of Ni Foam-Supported MnOx for Boosting Magnetocaloric Oxidation of Toluene.

Catalytic oxidation has been considered an effective technique for volatile organic compound degradation. Development of metal foam-based monolithic catalysts coupling electromagnetic induction heating (EMIH) with efficiency and low energy is critical yet challenging in industrial applications. Herein, a Mn18.2-NF monolithic catalyst prepared by electrodeposition exhibited superior toluene catalytic activity under EMIH conditions, and the temperature of 90% toluene conversion decreased by 89 °C compared to that in resistance furnace heating. Relevant characterizations proved that the skin effect induced by EMIH encouraged activation of gaseous oxygen, leading to superior low-temperature redox properties of Mn18.2-NF under the EMIH condition. In situ Fourier transform infrared spectroscopy results showed that skin effect-induced activation of oxidizing species further accelerated the conversion of intermediates. As a result, the Mn18.2-NF monolithic catalyst under EMIH demonstrated remarkable performance for the toluene oxidation, surpassing the conventional nonprecious metal catalyst and other reported monolithic catalysts.

Pt/CeO2 coated with polyoxometallate chainmail to regulate oxidation of chlorobenzene without hazardous by-products.

Doping noble metal and acid functionalization were both valid approaches to facilitate oxidation of chlorobenzene on CeO2-based catalysts, but their promotion effects were influenced by different orders of modification process. Because of strong interaction between metal and support and proper redox nature of CeO2, Pt NPs were re-dispersed into single atoms on CeO2 surface via "ex-solution". Companied with Pt loading, the enhancement of oxidizing ability led to generation of polychlorinated by-products. Herein, CeO2-supported Pt was coated by HSiW chainmail to protect Pt from being exposed to Cl-contained atmosphere, and HSiW coating promoted activation of chlorobenzene. The as-prepared chainmail catalyst of HSiW/Pt/CeO2 displayed a remarkable performance in catalyzing oxidation of chlorobenzene without any dichlorobenzene at realistic condition. By comparison, other catalysts with exposed Pt suffered from production of toxic by-products.

Using the Interaction between Copper and Manganese to Stabilize Copper Single-atom for CO Oxidation.

The interaction between Cu and Mn has been used to immobilize the Cu single-atom on MnO2 surface by redox-driven hydrolysis. Comprehensive structure and property characterizations demonstrate that the existence of an Cu-Mn interaction on the catalyst surface can effectively restrain the aggregation of Cu single atoms and improve carbon monoxide (CO) oxidation activity. The interaction of forming the Cu-O-Mn entity is beneficial for CO catalytic activity as the migration of reactive oxygen species and the coordination effect of active centers accelerate the reaction. In particular, 3%-Cu1 /MnO2 shows an oxygen storage capacity (OSC) value (342.75 µmol/g) more than ten times that of pure MnO2 (27.79 µmol/g) and has high CO catalytic activity (T90% =80 °C), it can maintain CO conversion of 95 % after 15 cycles. This work offers a reliable method for synthesizing Cu single-atom catalysts and deepens understanding of the interaction effect between single transition metal atoms and supports that can improve the catalytic activity of CO oxidation.