A comparative study of the dichloromethane catalytic combustion over ruthenium-based catalysts: Unveiling the roles of acid types in dissociative adsorption and by-products formation

Catalytic Oxidation of Chlorobenzene over Amorphous Manganese-Chromium Catalysts Supported by UiO-66-Derived ZrOx

The development of efficient catalysts with longevity to remove chlorobenzene is challenging due to Cl poisoning. Herein, a series of Mn-Cr/ZrOx catalysts supported by Zr-based metal-organic framework (UiO-66)-derived ZrOx was prepared and investigated for chlorobenzene (CB) catalytic oxidation. MnCr/ZrOx-M prepared via a wet impregnation method presented an amorphous structure, indicating the homogeneous dispersion of Cr and Mn, which improved acid and redox properties. 40Mn7Cr3/ZrOx-M exhibited the best catalytic activity for chlorobenzene oxidation with T90 of 293 °C, which is mainly due to the strong interaction between manganese and chromium promoted by the large specific surface area of the ZrOx support. Furthermore, 40Mn7Cr3/ZrOx-M presented excellent stability for chlorobenzene oxidation.

Promoted wet peroxide oxidation of chlorinated volatile organic compounds catalyzed by FeOCl supported on macro-microporous biomass-derived activated carbon

Chlorinated volatile organic compounds (CVOCs) are a recalcitrant class of air pollutants, and the strongly oxidizing reactive oxygen species (ROS) generated in advanced oxidation processes (AOPs) are promising to degrade them. In this study, a FeOCl-loaded biomass-derived activated carbon (BAC) has been used as an adsorbent for accumulating CVOCs and catalyst for activating H₂O₂ to construct a wet scrubber for the removal of airborne CVOCs. In addition to well-developed micropores, the BAC has macropores mimicking those of biostructures, which allows CVOCs to diffuse easily to its adsorption sites and catalytic sites. Probe experiments have revealed HO^• to be the dominant ROS in the FeOCl/BAC + H₂O₂ system. The wet scrubber performs well at pH 3 and H₂O₂ concentrations as low as a few mM. It is capable of removing over 90% of dichloroethane, trichloroethylene, dichloromethane and chlorobenzene from air. By applying pulsed dosing or continuous dosing to replenish H₂O₂ to maintain its appropriate concentration, the system achieves good long-term efficiency. A dichloroethane degradation pathway is proposed based on the analysis of intermediates. This work may provide inspiration for the design of catalyst exploiting the inherent structure of biomass for catalytic wet oxidation of CVOCs or other contaminants.

Ru-based monolithic catalysts for the catalytic oxidation of chlorinated volatile organic compounds

A series of cordierite monolithic catalysts with Ru species supported on different available low-cost carriers were prepared and investigated for the elimination of CVOCs. The results suggest that the monolithic catalyst with Ru species supported on anatase TiO₂ carrier with abundant acidic sites exhibited the desired catalytic activity for DCM oxidation with the T _90% value of 368 °C. In addition, a pseudo-boehmite sol used as binder was introduced into the preparation of the monolithic catalysts to further improve the adhesion between the powder catalysts and cordierite honeycomb carrier. The results suggest that although the T _50% and T _90% of the Ru/TiO₂/PB/Cor shifted to higher temperature of 376 and 428 °C, the weight loss of the coating for the Ru/TiO₂/PB/Cor catalyst was improved and decreased to 6.5 wt%. Also, the as-obtained Ru/TiO₂/PB/Cor catalyst exhibited ideal catalytic properties for the abatement of ethyl acetate and ethanol, indicating that the catalyst can meet the demand for the treatment of actual multi-component industrial gas.

Abatement of dichloromethane with high selectivity over defect-rich MOF-derived Ru/TiO2 catalysts

The regulation of oxygen vacancies and Ru species using metal-organic frameworks was synergically adopted in a rational design to upgrade Ru/TiO₂ catalysts, which are highly active for the catalytic oxidation of dichloromethane (DCM) with less undesired byproducts. In this work, Ru/M-TiO₂ and Ru/N-TiO₂ catalysts were synthesized by the pyrolysis of MIL-125 and NH₂-MIL-125 incorporated with Ru, the existence of Ru nanoclusters and nanoparticles was detected by XAFS, respectively, and the catalytic performance was analyzed comprehensively. Complete oxidation of DCM was obtained at ∼290 °C over Ru/M-TiO₂ and Ru/N-TiO₂ catalysts, while Ru/N-TiO₂ showed quite less monochloromethane (MCM) and higher CO₂ yields, and better dechlorination capacity in oxidation. The distinction comes down to that the easier desorption of chlorine could be achieved over Ru⁴⁺ which act as the main activated adsorption sites for DCM in Ru/N-TiO₂, compared to oxygen vacancies that serve as the main dissociation sites in Ru/M-TiO₂. Additionally, Ru/N-TiO₂ exhibited superior stability and excellent resilience in moisture. An in situ DRIFTS experiment further indicated the different DCM catalytic degradation process as well as the reaction mechanism over the as-prepared catalysts.

Selective Ru Adsorption on SnO2/CeO2 Mixed Oxides for Efficient Destruction of Multicomponent Volatile Organic Compounds: From Laboratory to Practical Possibility

Ru-based catalysts have been extensively employed for the catalytic destruction of chlorinated volatile organic compounds (VOCs), but their versatility for other routine VOCs' destruction has been less explored. Herein, we show that Ru-decorated SnO₂/CeO₂ mixed oxides can sustain H₂O and HCl poisonings and are endowed with extraordinary versatility for a wide range of VOCs' destruction. Selective adsorption of Ru on the cassiterite SnO₂ and CeO₂ nanorods through a Coulomb force can rationally tune the oxidation and dechlorination centers on decorated catalysts, where the epitaxial growth of RuO_x on top of SnO₂ is endowed with excellent dechlorination ability and that on CeO₂ is functional as an oxidation center; the latter could also activate H₂O to provide sufficient H protons for HCl formation. Our developed Ru/SnO₂/CeO₂ catalyst can steadily destruct mono-chlorobenzene, ortho-dichlorobenzene, trichloroethylene, dichloromethane, epichlorohydrin, N-hexane, ethyl acetate, toluene, and their mixtures at an optimum temperature of 300 °C, and its monolithic form is also functional at this temperature with few dioxins being detected in the off-gas. Our results imply that the Ru-decorated SnO₂/CeO₂ catalyst can meet the demands of regenerative catalytic oxidation for the treatment of a wide range of VOCs from industrial exhausts.

Catalytic ozonation of dichloromethane at low temperature and even room temperature on Mn-loaded catalysts

Five Mn-loaded catalysts were synthesized on γ-Al₂O₃, TiO₂, ZrO₂, nano γ-Al₂O₃ and nanoZrO₂ supports. The catalytic ozonation of DCM (dichloromethane) was evaluated under industrial conditions (i.e., temperature, O₃ input, H₂O and SO₂ content). According to results, >90% DCM conversion without O₃ residue was achieved for all samples at 120 °C and an O₃/DCM ratio of 6. At 20–120 °C, the highest Mn³⁺ content, abundant surface oxygen species and more weak acid sites led to the best performance of Mn/nanoAl₂O₃ (M/A-II). At 20 °C and 120 °C, 80% and 95% DCM can be degraded respectively on M/A-II at 20 °C with matched surface oxygen species and acidity. An O₃/DCM ratio of 6 was optimal for performance and economy. For the effects of complex exhaust, both H₂O and SO₂ deactivated M/A-II. The H₂O-induced deactivation was recoverable and also removed surface-deposited chlorine-containing species, enhancing the HCl selectivity. Finally, the Cl equilibrium of the reaction was comprehensively analyzed.

The collaboration of abundant surface oxygen species and weak acid sites at low temperatures ensures the best functioning of M/A-II.

Promoting effect of Ru-doped Mn/TiO2 catalysts for catalytic oxidation of chlorobenzene

Mn/TiO2 catalysts were synthesized using deposition-precipitation method. Ru-doped Mn/TiO2 catalysts were prepared by incipient-wetness impregnation method. To investigate the effect of Ru and Mn species, the catalytic performances of Mn/TiO2...