Effect of transition metal oxide doping on catalytic activity of titania for the oxidation of 1,2-dichloroethane

Praseodymium-Doped Cr2O3 Prepared by In Situ Pyrolysis of MIL-101(Cr) for Highly Efficient Catalytic Oxidation of 1,2-Dichloroethane

The development of economical catalysts that exhibit both high activity and durability for chlorinated volatile organic compounds (CVOCs) elimination remains a challenge. The oxidizing and acidic sites play a crucial role in the oxidation process of CVOCs; herein, praseodymium (Pr) was introduced into CrOx catalysts via in situ pyrolysis of MIL-101(Cr). With the decomposition of the ligand, a mixed micro-mesoporous structure was formed within the M-Cr catalyst, thereby reducing the contact resistance between catalyst active sites and the 1,2-dichloroethane molecule. Moreover, the synergistic interaction between chromium and praseodymium facilitates Oβ species and acidic sites, significantly enhancing the low-temperature catalytic performance and durability of the M-PrCr catalyst for 1,2-dichloroethane (1,2-DCE) oxidation. The M-30PrCr catalyst possess enhanced active oxygen sites and acid sites, thereby exhibiting the highest catalytic activity and stability. This study may provide a novel and promising strategy for practical applications in the elimination of 1,2-DCE.

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.

Catalytic degradation of chlorinated volatile organic compounds (CVOCs) over Ce-Mn-Ti composite oxide catalysts

Developing industrially moldable catalysts with harmonized redox performance and acidity is of great significance for the efficient disposal of chlorinated volatile organic compounds (CVOCs) in actual exhaust gasses. Here, commercial TiO2, typically used for molding catalysts, was chosen as the carrier to fabricate a series of Ce0.02Mn0-0.24TiOx materials with different Mn doping ratios and employed for chlorobenzene (CB) destruction. The introduction of Mn remarkedly facilitated the synergistic effect of each element via the electron transfer processes: Ce3++Mn4+/3+↔Ce4++Mn3+/2+ and Mn4+/3++Ti4+↔Mn3+/2++Ti3+. These synergistic interactions in Ce0.02Mn0.04-0.24TiOx, especially Ce0.02Mn0.16TiOx, significantly elevated the active oxygen species, oxygen vacancies and redox properties, endowing the superior catalytic oxidation of CB. When the Mn doping amount increased to 0.24, a separate Mn3O4 phase appeared, which in turn might weaken the synergistic effect. Furthermore, the acidity of Ce0.02Mn0.04-0.24TiOx was decreased with the Mn doping, regulating the balance of redox property and acidity. Notably, Ce0.02Mn0.16TiOx featured relatively abundant B-acid sites. Its coordinating redox ability and moderate acidity promoted the deep oxidation of CB and RCOOH- intermediates, as well as the rapid desorption of Cl species, thus obtaining sustainable reactivity. In comparison, CeTiOx owned the strongest acidity, however, its poor redox property was not sufficient for the timely oxidative decomposition of the easier adsorbed CB, resulting in its rapid deactivation. This finding provides a promising strategy for the construction of efficient commercial molding catalysts to decompose the industrial-scale CVOCs.

Progress of catalytic oxidation of typical chlorined volatile organic compounds (CVOCs): A review

Chlorinated volatile organic compounds (CVOCs) are still a part of the current atmospheric environmental problems that cannot be ignored, but unlike conventional VOCs, the presence of Cl causes various catalyst deactivations in the catalytic process. In this paper, we focus on six common CVOCs and discuss various behavioral mechanisms of the whole catalytic process from six aspects: catalyst selection, factors affecting the catalytic effect, changes in catalytic behavior in the presence of different gases, catalyst poisoning deactivation behavior, degradation products and degradation mechanisms to provide guidance for further development of low-temperature and efficient CVOCs catalysts.

Core-shell CoCuOx@MOx (MNb, Ti and Ce) catalysts with outstanding durability and resistance to H2O for the catalytic combustion of o-dichlorobenzene

Configuring Co-based catalysts with excellent activity, durability, anti-H₂O capability and superior chlorine resistance is an effective strategy for catalytic combustion of CVOCs. In this work, we elaborated a CoCuO_x catalysts with the same core but different shell. The CoCuO_x dodecahedron surface was successfully coated with shells of Nb₂O₅, TiO₂, and CeO₂ using a range of conventional synthesis methods. The prepared core-shell catalysts (CoCuO_x@TiO₂ and CoCuO_x@Nb₂O₅) were found to generate plentiful acid sites and abundant lattice oxygen species, indicating a strong interaction between the core and shell layers that resulted in a significant enhancement of catalytic activity. Additionally, by-products generation was successfully controlled by acid sites and lattice oxygen species. More importantly, the core-shell structure design significantly improved the thermal stability and anti-H₂O capability of the catalysts. Furthermore, the possible formation pathways and reaction mechanisms were proposed based on in-situ FTIR and selectivity analysis.

High Selectivity to HCl for the Catalytic Removal of 1,2-Dichloroethane Over RuP/3DOM WOx: Insights into the Effects of P-Doping and H2O Introduction

Ru-based catalysts for catalytic combustion of high-toxicity Cl-containing volatile organic compounds are inclined to produce Cl₂ instead of ideal HCl due to the Deacon reaction. We herein reported that the three-dimensionally ordered macroporous (3DOM) WO_x-supported RuP nanocatalyst greatly improved HCl selectivity (at 400 °C, increased from 66.0% over Ru/3DOM WO_x to 96.4% over RuP/3DOM WO_x) and reduced chlorine-containing byproducts for 1,2-dichloroethane (1,2-DCE) oxidation. P-doping enhanced the number of structural hydroxyl groups and Brønsted acid sites. The isotopic 1,2-DCE temperature-programmed desorption experiment in the presence of H₂¹⁸O indicated the generation of a new active oxygen species ¹⁶O¹⁸O that participated in the reaction. Generally, P-doping and H₂O introduction could promote the exchange reaction between Cl and hydroxyl groups, rather than oxygen defects, and then benefit the production of HCl and reduce the generation of other chlorine species or Cl₂, via the reaction processes of C₂H₃Cl → alcohol → aldehyde → carboxylic acids.