The catalytic degradation of chlorinated volatile organic compounds (CVOCs) often encounters challenges such as excessive chlorination, volatilization, and deactivation of active catalytic sites, resulting in a shortened catalyst lifespan, formation of polychlorinated by-products, and reduced rate of mineralization. Herein, we developed H-zeolite supported multi-interface metal catalysts consisting of CuNbCeOx/HZSM-5 with three types of conjugated active centers. Through experimental and computational demonstrations, we have shown that the catalytic destruction of chlorobenzene (CB) involves distinct active centers responsible for directional fixed chlorine, water dechlorination, and high efficiency mineralization processes. The temperature at which 90% of CB is removed can be achieved at 260 degrees C, while complete mineralization occurs at 370 degrees C. and stability tests demonstrate that complete removal of CB can be maintained at 320 degrees C for over 24 h. The excellent resistance to chlorine poisoning during reaction process is primarily due to the preferential adsorption of chlorine over the NbO of Cu-Nb interface, inhibiting the transformation of Cu-O and Ce-O to Cu-Cl and Ce-Cl, which maintain the high level of oxidation performance. After addition water into reaction process, the hydrogen protons produced through water dissociation transfer the chlorine adsorbed on the copper-connected Nb surface to form HCl. This is caused by the water molecules efficiently absorb onto the Ce-O at the Cu-Ce interface and then dissociate on adjacent Cu-O sites. This water-mediated promotion of chlorine transfer significantly also reduces the content of dichlorobenzene and chlorophenol, which are precursors to dioxins. Finally, a detailed mechanism for CB elimination has been proposed by using In situ DRIFTS and GC/MS. These findings provide possible solution for catalyst design and process optimization in practical applications aimed at eliminating chlorinated organic waste gases from industrial emissions.

Recent research highlights the pressing need for innovative and practical oxidation degradation technologies for volatile organic compounds (VOCs). In this study, a monolithic catalyst was successfully developed by loading PtCeO2 onto nickel foam (NF) matrix through hydrothermal and reduction methods. The photothermal catalytic performance was investigated at room temperature for varying Pt content, toluene concentration, light source type, and water content. Remarkably, the toluene removal efficiency and CO2 selectivity stabilized at 98.8 % and 74.6 %, respectively, within less than 10 min of light activation. The d-d transition thermal effect of CeO2 and plasma effect of Pt enhanced light-to-heat conversion and active free radical generation (center dot O2- and center dot OH) through light absorption, respectively. The NF matrix's excellent thermal conductivity ensured a rapid increase in catalyst temperature upon visible light irradiation, reaching 173 degrees C. The study demonstrated that both the Mars-van Krevelen (Mvk) oxidation process, driven by temperature increase from near-infrared (NIR) absorption, and the free radical oxidation process, induced by higher energy illumination, synergistically contributed to toluene decomposition and mineralization. The catalyst's morphology, physical and chemical properties, surface synergistic oxidation process involving gaseous oxygen and free radicals, and toluene degradation pathway were thoroughly analyzed. We believe that this coexistence of thermocatalytic and photocatalytic mechanisms in a monolithic catalyst driven by renewable solar energy holds significant potential for practical applications and warrants further exploration.

Composite oxides obtained by calcining layered double hydroxides (LDHs) were used to construct a functional hydrolysis interface. Using nickel foam (NF) as a carrier, LDH was produced on the surface of this monolithic catalyst. The original morphology was retained after calcination. NF provided better thermal conductivity for catalytic combustion than conventional cordierite carriers. The clear phase interface between the different mixed metal oxides (CuxCo3-xFe-MMO/NF) promoted oxidation and hydrolysis during toluene combustion. Physicochemical investigations were performed using XRD, SEM, TEM, H-2-TPR, ESR, and XPS. GC-MS, in situ DRIFT, H2O-TPD, and DFT were also used to explore the deep hydrolysis mechanism. The dissociation of water to form the surface *OH was the main hydrolysis process owing to the existence of the Cu-Co functional interface, with the largest energy emission (0.56 eV from DFT calculations). This hydrolysis process also altered the toluene degradation pathway, as confirmed by the in situ DRIFTS and GC/MS results, which guaranteed significant stability of the Cu1Co2Fe-MMO/NF catalyst in a highly humid environment and the removal efficiency and mineralization of toluene were both >90 % below 270 degrees C. This monolithic catalyst exhibits excellent water resistance and the toluene conversion rate remained stable at 90 % without any attenuationhas >40 h, which provides potential utility in the combustion of volatile organic compounds in high-humidity industrial streams.

The catalytic combustion of chlorine-containing VOCs primarily encounters the bottleneck of catalyst poisoning by chlorine, thereby impeding the further industrial application of this technology. The development of multi-active catalytic materials for discerning chlorine fixation, chlorine transfer, deep oxidation during elimination of chlorine-containing VOCs can mitigate catalyst chlorination and enhance stability. Herein, we utilizing LDHs as catalyst precursors and successfully synthesized flower-like Co2FexCr1-xOy catalyst with different functionalized reaction centers. The addition of Cr improved the surface lattice oxygen, oxygen vacancies, and acid sites of catalyst. The removal efficiency of CB can be achieved >90 % at 247 degrees C (WHSV = 33000 mL g(-1)h(-1)). The fixation of dissociated chlorine contributed by Cr not only enhances oxidation performance and directional adsorption of chlorine, but also improves carbon deposition resistance and catalyst sintering resistance significantly. Compared with Co2Fe1Oy, Co2Fe0.67Cr0.33Oy catalyst achieves a remarkable threefold reduction in surface carbon deposition. The DFT calculation revealed that water dissociation energy over the Co site is -0.72 eV, which is significantly lower than Fe (-0.59 eV) and Cr (-0.17 eV), facilitating water dissociation and subsequently removes a substantial amount of accumulated chlorine on Cr to form HCl. With the help of In situ DRIFT and GC/MS analysis, we found the efficient removal of chlorine atoms enhances the exposure of active sites on the catalyst surface with hydrolyzed hydroxyl group, which facilitating the conversion of aromatic hydrocarbons into a greater quantity of maleate and carboxylate species. This phenomenon is beneficial for the subsequent mineralization process of chlorobenzene. This work provide valuable insights for multi-active site catalysis mechanism in practical applications aimed at eliminating chlorinated organic waste gases from industrial emissions.

Photocatalysis is a feasible method for degrading indoor formaldehyde (HCHO) pollutants. To improve the purification efficiency and lower the cost of using noble metals as the primary component of the catalyst, synergistic catalysis involving two catalytic modes, such as thermocatalysis/photocatalysis, has attracted significant attention. In this study, a monolithic catalyst was prepared by loading reduced graphene oxide (rGO) and cerium dioxide (CeO2) on a nickel foam (NF) matrix. It was observed that the HCHO removal efficiency could be > 93 % under xenon light. The pre-deposited rGO on the NF matrix served as the photothermal conversion layer and contributed to the uniform and stable loading of CeO2. The surface temperature of this synthesized monolithic catalyst could rapidly rise to 170 degrees C. In addition, the heat was distributed evenly because of the increased nearinfrared (NIR) light absorption caused by the added rGO and high electron mobility owing to the heat-conducting property of NF. At this temperature, the oxidation of HCHO was stimulated not only by the lattice oxygen of CeO2 but also by the production of center dot O2- via oxidation by photogenerated electrons. In addition, center dot O2- would reoxidize Ce3+ to Ce4+ on oxygen vacancies and accelerate the lattice oxygen consumption and supply cycle to reinforce the existing Mars-van Krevelen (MvK) mechanism.

Chlorinated volatile organic compounds (CVOCs) emitted from the industrial fabrication process and coatings, pharmacy, and incineration are toxic to the environment and humans. Catalytic combustion can convert CVOCs into CO2, H2O, and HCl/Cl2 at lower temperatures; as such, it is regarded as a promising method at present. However, it still causes serious secondary pollutants because of the involved toxic polychlorinated byproducts that are discharged in the tail gas or deposited on the catalyst surface or reaction device. This is because the individual combustion process cannot completely remove the dissociated chlorine to form HCl; therefore, it can react again with the catalyst or byproducts, resulting in the deactivation of the catalyst and the formation and accumulation of polychlorinated byproducts, including dioxin. The industrial catalytic hydro-dechlorination (HDC) process is more concerned with formation of HCl and acquisition of desired products, which is expected to achieve a possible result of complete elimination of industrial CVOC gas without secondary byproduct pollution via combination of the combustion process and HDC process. Herein, we highlight the reaction characteristics of combustion and HDC methods against CVOCs and provide a perspective on the need for accomplishing the elimination and recycling of industrial CVOCs in the design of possible combined processing methods.

Mg-doped manganese oxide octahedral molecular sieve (Mg-OMS-2) catalysts were prepared by hydrothermal method. The photothermal degradation performance of these catalysts for formaldehyde (HCHO) in batch system and continuous system was investigated. The light absorption of OMS-2 was increased by Mg-doped, especially for near infrared light, which promoted surface temperature reach a maximum of 214.8 degrees C under xenon irradiation. At this temperature, the reinforced surface lattice oxygen and oxygen vacancy that formed by lattice distortion via Mg-doped were activated. The best HCHO elimination efficiency was achieved over Mg0.2 /OMS-2 catalyst with Mg2 + /Mn2 + = 1/5, which could reduce HCHO from 250 ppm to 10 ppm within 20 min. The in situ DRIFTS was also carried out to monitor the changes in the content of reaction intermediates and analyze the degradation paths of HCHO. It was found the HCHO was attacked by formed center dot OH and center dot O2- to generate formate species and carbonate species, and finally transformed to CO2 and H2 O. This photothermal catalytic oxidation process exhibited a high efficiency purification of HCHO without the help of extra energy consumption. (c) 2024 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.

Much attention has been paid to developing effective visible light catalytic technologies for VOC oxidation without requiring extra energy. In this paper, a series of sponge-based catalysts with rich three-dimensional porosity are synthesized by combining MnOx and graphitic carbon nitride (GCN) with commercial melamine sponges (MS) coated with polydopamine (PDA), demonstrating excellent photothermal catalytic performance for formaldehyde (HCHO). The three-dimensional porous framework of MS can provide a good surface for material modification and a reliable interface for gas-solid interaction. The grown layer of PDA framework not only increases the near-infrared wavelength absorption for improving the light-to-heat conversion of catalysts, but also brings excellent adhesion for the subsequent addition of MnOX and GCN. The efficient formaldehyde oxidation is attributed to the sufficient oxygen vacancies generated by co-loaded MnOX and GCN, which is conducive to the activation of more O2− in the oxidation process. As the surface temperature of catalyst rapidly increases to its maximum value at ca. 115 °C under visible light irradiation, the HCHO concentration drops from 160 ppm to 46 ppm within 20 min. The reaction mechanism is certified as a classical Mars-van Krevelen mechanism based on the photo-induced thermal catalysis process.