Chlorinated Volatile Organic Compounds Research Articles

Molybdenum Carbide Catalyst Enables Efficient Conversion of Chlorinated Volatile Organic Waste into Syngas through Catalytic Steam Reforming.

Catalytic steam reforming offers a groundbreaking approach for converting industrial chlorinated volatile organic compound (CVOC) waste into valuable syngas (H2 and CO) and recovering HCl. However, the lack of C-Cl bond activation ability in traditional transition metal catalysts results in their insufficient reforming activity toward CVOCs. Herein, a novel molybdenum carbide (β-Mo2C) catalyst is developed and loaded onto a γ-Al2O3 support synthesized through a self-assembly method. The γ-Al2O3 support provides abundant unsaturated coordinated Al3+ ions, which effectively anchor and disperse β-Mo2C nanoparticles. In the catalytic steam reforming reaction at 600 °C, the β-Mo2C/γ-Al2O3 catalyst achieves a conversion efficiency higher than 95% and syngas yields of 82.4-92.3% for various typical industrial CVOCs. The mechanistic research reveals that the coordination between C and Mo atoms in β-Mo2C leads to a slightly electron-deficient state of the Mo sites, accompanied by a high density of unoccupied 4d orbitals. These characteristics are highly advantageous for the adsorption and dechlorination of CVOC molecules. The produced nonchlorinated intermediates can subsequently be oxidized to CO and H2 by hydroxyl radicals on adjacent Mo sites.

Boosted 1,2-Dichloroethane Deep Destruction over CoRu/Al2O3 Bifunctional Catalysts via Surface Oxygen and Water Molecule Synergistic Activation.

Developing efficacious catalysts with superior Cl resistance and polychlorinated byproduct inhibition capability is crucial for realizing the environmentally friendly purification of chlorinated volatile organic compounds (CVOCs). Activating CVOC molecules and desorbing Cl species by modulating the metal-oxygen property is a promising strategy to fulfill these. Herein, a bifunctional CoRu/Al2O3 catalyst with synergistic Co and Ru interactions (Ru-O-Co species) was rationally fabricated, which possesses abundant surface Co2+ and Ruδ+ sites and collaboratively facilitates the activation of lattice oxygen (O2-) and molecular oxygen (O2 → O2- → O-), accelerating 1,2-dichloroethane (1,2-DCE) decomposition via the reaction route of enolic species → aldehydes → carboxylate/carbonate. Furthermore, CoRu/Al2O3 stimulates 1,2-DCE oxidation under humid conditions as H2O molecules can be easily activated to active *OH (potential oxidizing agent) over Ru species, accelerating C-Cl dissociation and Cl desorption and promoting the transformation of catecholate-type (C═O) species to easily oxidizable carboxylic acid (COOH) species, remarkably suppressing the formation of hazardous CCl4 and CHCl2CH2Cl. This study provides critical insights into the development of bifunctional catalysts to synergistically activate surface oxygen species and H2O molecules for industrial CVOC stable and efficient elimination.

Investigation of the by-product selectivity of industrialized support for the catalytic elimination of o-DCB over Pt-catalysts

For chlorinated volatile organic compounds (CVOCs), it is critical to design and fabricate applicable noble metal catalysts to exhibit superior catalytic performance in catalytic oxidation under both dry air and 5.0 vol% H2O conditions. In pursuit of this goal, a facile strategy was developed to prepare a series of Pt-supported catalysts for the elimination of o-dichlorobenzene (o-DCB). Among these catalysts, Pt/CeAlZrOx possessed excellent activity (T90 = 285 °C) and Pt/LaAlOx showed outstanding selectivity within/without 5.0 vol% H2O, attributed to the strong interaction of multi-components, abundance of adsorbed oxygen, prominent redox properties, and suitable acidity. According to the analysis results of density functional theory (DFT), the introduction of Pt can significantly improve the adsorption and activation of o-DCB molecules on the catalysts. Specifically, the action of Marse-van Krevelen (MvK) combining with Langmuir-Hinshelwood (L-H) mechanism was proposed. In general, this work provides promising candidates and valuable insights into the comprehensive improvement of o-DCB catalytic degradation for industrial application.

Sustainable and efficient catalytic oxidation of chlorinated volatile organic compounds over Ru-loaded facet-engineered {201}-TiO2 catalyst with tuned defects

Sustainable and efficient catalytic oxidation of chlorinated volatile organic compounds (CVOCs) poses an enduring challenge. This bottleneck arises from the limited catalytic activity of redox reactions and chlorine desorption, causing catalyst deactivation and secondary pollution. Herein, our sound strategy involves Ru-loaded facet-engineered {201}-TiO2 with tuned defects, thereby boosting its reactivity. Comprehensive characterizations and DFT calculation manifested that Ru/{201}-TiO2, with abundant oxygen vacancies, Ti3+ defects, and robust metal-support interaction, enabled flexible electron transfer to activate O2 and the dissociation of H2O, thus facilitating the continuous generation of reactive oxygen species (ROS), such as •O2– and hydroxyl species. These ROS effectively enhance chlorine desorption and chlorobenzene deep oxidation. Ru/{201}-TiO2 exhibited superior reactivity for chlorobenzene degradation, with an apparent activation energy (Ea) of 31.0 KJ/mol and 100 % chlorobenzene conversion in a 1000-min stability test, even with H2O introduction. Ru/{201}-TiO2 produced 2.2–3.1 times fewer small-molecule chlorinated byproducts than Ru/{101}-TiO2, with no polychlorinated benzenes detected.

Adsorption recovery of chlorinated volatile organic compounds on coffee ground-based activated carbon of tunable porosity

Chlorinated volatile organic compounds (CVOCs) play an indispensable role in industrial production, but meanwhile pose serious threats to human health. As a response to the urgent and challenging requirements of reducing pollution and carbon emissions, in this work, the critically favorable ultra-micropores and hierarchical porous structure are constructed onto the low-cost coffee ground-based activated carbon (AC) for the CVOCs adsorption recovery. To regulate the processes of carbonization and activation, the formation of the porosity is elaborated in terms of elements, functional groups and graphited structure. As expected, abundant ultra-micropores (<1 nm) are particularly apt to the adsorption of 1,2-dichloroethane (1,2-DCE) of small size and also contribute positively to the adsorption of chlorobenzene (CB). Moreover, the sample S400-4 possesses a large surface area (1643 m2/g), pore volume (0.89 cm3/g) and hierarchical porous structures that greatly benefit the adsorption of both 1,2-DCE (2.11 mmol/g) and CB (4.15 mmol/g). The advantage is ascribed to the facilitated transfer of CVOCs through the hierarchical porous structures and the higher affinity of CB for the π-π interaction. S400-4 presents a good performance in the recycle tests and with the interference of co-existing components alike, which indicates the engineering application potential of coffee ground-based AC. Hopefully, this work sheds light on the structure-function relationship between biomass-based AC and CVOCs adsorption, and contributes to the targeted development of suitable CVOCs adsorption materials and recovery technologies.

Enhanced catalytic performance and antichlorine poisoning over Cu-doped cobalt oxide nanosheets for chlorobenzene oxidation

The degradation of Chlorinated volatile organic compounds (CVOCs) by catalytic oxidation forms toxic products, and catalysts may be poisoned by chlorine at low temperatures. To address this, a Cu-assisted strategy is proposed for enhancing the catalytic degradation of chlorobenzene (CB) over cobalt oxide nanosheets. The Cu-doped Co3O4 catalysts exhibited lower T90 values (temperatures with 90 % conversion) and improved stability compared to the unmodified catalyst. These results were attributed to strong metal-metal interactions between Cu species and cobalt oxide nanosheets, which showed a high specific surface area, reduced binding energy of lattice oxygen, higher surface oxygen concentration, and more surface Co3+ species. These properties promoted low-temperature catalytic activity. In addition, the disappearance of Cu2+ satellite peak after the catalyst is used, indicating that the Cu2+ also contributes to the catalytic activity. Furthermore, the in situ FTIR spectra provided details about the reaction mechanism of CB degradation over Cu-doped cobalt oxide nanosheets. The oxygen vacancy generation and the surface absorption of chlorine-containing intermediates were calculated using density functional theory calculations. This study provides new insight into novel pathways for catalyst design aimed at CB degradation.

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.

Unveiling microbial community structure and metabolic pathway over carbon cloth-titanium nitride-polyaniline biocathode for effective dichloromethane transformation

Chlorinated volatile organic compounds (Cl–VOCs) have dramatically biotoxicity and environmental persistence due to the presence of chlorine atoms, seriously jeopardizing ecological security and human health. Dichloromethane (DCM) as a model pollutant, is widely applied in solvents, extractants and cleaning agents in the pharmaceutical, chemical and food industries. In this study, highly biocompatible and conductive carbon cloth-titanium nitride-polyaniline (CC–TiN-PANI) bioelectrodes were obtained for DCM degradation in microbial electrolysis cell (MEC). The good adhesion of TiN and PANI on the electrode surface was demonstrated. The degradation kinetics were fitted by the Haldane model, compared to the CC bioelectrode (0.8 h−1), the proportion of maximum degradation rates to half-saturation concentration (Vmax/Km) of CC-TiN (1.4 h−1) and CC-TiN-PANI (2.2 h−1) bioelectrodes were enhanced by 1.8 and 2.8 times, respectively. Microbial community structure analysis illuminated that the dominant genera on the biofilm were Alicycliphilus and Hyphomicrobium, and the abundance was enhanced significantly with the modification of TiN and PANI. The dechlorination of DCM to formaldehyde could be catalyzed by DCM dehalogenase (DcmA) or by haloalkane dehalogenase (DhlA). And further oxidized to formate: 1) direct catalyzed by formaldehyde dehydrogenase (FdhA); 2) conjugated with glutathione by S-(hydroxymethyl)-glutathione synthase (Gfa), S-(hydroxymethyl)-glutathione dehydrogenase (FrmA) and S-formyl-glutathione hydrolase (FrmB); 3) conjugation with tetrahydrofolate (H4F) and/or tetrahydromethanopterin.

Promotional effect of WO3 in V2O5–WO3/TiO2 on low-temperature activity in the catalytic oxidation of 1,2-dichloroethane

Transition metal oxides are promising catalysts for the degradation of chlorinated volatile organic compounds (CVOCs). However, their practical applications are limited due to their poor low-temperature (<300 °C) activity. In this study, we introduced WOx into VOx/TiO2 to modulate its redox and acidic properties. We found that the V2O5(2 wt%)–WO3(10 wt%)/TiO2 (2V10W/TiO2) catalyst exhibited a 1,2-dichloroethane (DCE) conversion of 90 % at 256 °C, which is comparable to that of Ru-based catalysts (DCE conversion of 90 % at 257–340 °C) for the oxidation of DCE. The addition of WOx into VOx/TiO2 gave rise to the formation of labile surface oxygen species and promoted interactions between V and W, which improved the reducibility, oxygen mobility, and Brønsted acidity of the 2V10W/TiO2 catalyst. These properties of 2V10W/TiO2 lowered its activation barrier for DCE oxidation and mitigated coke formation and Cl deposition on the catalyst, enhancing the low-temperature activity and long-term stability. The 2V10W/TiO2 catalyst also exhibited superior resistance to water. This study provides insights into catalytic design for balancing the redox and acidic properties in the catalytic oxidation of CVOCs.

Unveiling the Function of Oxygen Vacancy on Facet-Dependent CeO2 for the Catalytic Destruction of Monochloromethane: Guidance for Industrial Catalyst Design.

Secondary pollution remains a critical challenge for the catalytic destruction of chlorinated volatile organic compounds (CVOCs). By employing experimental studies and theoretical calculations, we provide valuable insights into the catalytic behaviors exhibited by ceria rods, cubes, and octahedra for monochloromethane (MCM) destruction, shedding light on the elementary reactions over facet-dependent CeO2. Our findings demonstrate that CeO2 nanorods with the (110) facet exhibit the best performance in MCM destruction, and the role of vacancies is mainly to form a longer distance (4.63 Å) of frustrated Lewis pairs (FLPs) compared to the stoichiometric surface, thereby enhancing the activation of MCM molecules. Subsequent molecular orbital analysis showed that the adsorption of MCM mainly transferred electrons from the 3σ and 4π* orbitals to the Ce 4f orbitals, and the activation was mainly caused by weakening of the 3σ bonding orbitals. Furthermore, isotopic experiments and theoretical calculations demonstrated that the hydrogen chloride generated is mainly derived from methyl in MCM rather than from water, and the primary function of water is to form excess saturated H on the surface, facilitating the desorption of generated hydrogen chloride.

Phosphotungstic Acid as a Dechlorination Agent Collaborates with CeO2 for Synergistic Catalytic Elimination of NOx and Chlorobenzene.

The development of efficient technologies for the synergistic catalytic elimination of NOx and chlorinated volatile organic compounds (CVOCs) remains challenging. Chlorine species from CVOCs are prone to catalyst poisoning, which increases the degradation temperature of CVOCs and fails to balance the selective catalytic reduction of NOx with the NH3 (NH3-SCR) performance. Herein, synergistic catalytic elimination of NOx and chlorobenzene has been originally demonstrated by using phosphotungstic acid (HPW) as a dechlorination agent to collaborate with CeO2. The conversion of chlorobenzene was over 80% at 270 °C, and the NOx conversion and N2 selectivity reached over 95% at 270-420 °C. HPW not only allowed chlorine species to leave as inorganic chlorine but also enhanced the Bro̷nsted acidity of CeO2. The NH4+ produced in the NH3-SCR process can effectively promote the dechlorination of chlorobenzene at low temperatures. HPW remained structurally stable in the synergistic reaction, resulting in good water resistance and long-term stability. This work provides a cheaper and more environmentally friendly strategy to address chlorine poisoning in the synergistic reaction and offers new guidance for multipollutant control.

Construction of ZIF-derived CoCrOx/HZSM5 catalysts for deep catalytic oxidation of dichloromethane: Synergistic of B acid, L acid, and redox sites

The acidic and oxidizing properties of the catalyst are critical for the removal of chlorinated volatile organic compounds (CVOCs). An excellent catalyst often requires outstanding chlorine resistance and byproduct inhibition. In this study, CoOx, which is widely used for the removal of volatile organic compounds (VOCs) because of its outstanding activity was chosen to provide oxidizing properties. To address the potential for chlorination byproducts and the lack of activity, we loaded CoOx on the acidic carrier HZSM-5 by ZIF-derived method, then doped CrOx using impregnation method to enhance both oxidation and acidity. It was found that ZIF-derived method disperse CoOx nicely thus providing more oxidation sites. Besides, CrOx effectively increases the superficial lattice oxygen of the catalyst to compensate for the loss of sites due to the occupation of oxygen vacancies by DCM during the oxidation process. This contributes to the superior oxidizability of the modified catalysts, which explains the high CO2 selectivity. Invigoratingly, CrOx can increase the ratio of Lewis acid to Brønsted acid to completely break the C–Cl bond, hence eliminating the possibility of chlorine-containing byproducts and accomplishing a deeper degradation of CVOCs. The bimetallic catalysts we prepared have high activity and can achieve very low or even zero byproduct generation. In addition, the catalyst shows outstanding stability and water resistance, which is quite meaningful in the field of catalytic oxidation of CVOCs.

Degradation of chlorinated volatile organic compounds in waste gas by catalytic plasma system

Dichloromethane (DCM), one of the main components of chlorinated volatile organic compounds (Cl-VOCs), is recognized as extremely hazardous and severely affects human health and the environment. In this study, a self-designed Dielectric Barrier Discharge (DBD) reactor combined with different catalysts to treat the exhaust DCM gas containing ppm concentration levels. A plasma system can generate high-energy electrons and free radicals (such as hydroxyl radical (OH·), and superoxide radical (O2·)) to degrade DCM in the industrial exhaust gas into most HCl and CO2. The removal efficiency can achieve 98.7% under the conditions, a flow rate of 1042 mLmin−1, the residence time of 76.72 ms, concentration of DCM of about 1650 ppm, and specific input energy of 591 JL−1. Although the plasma was highly reactive, the selectivity of the desired products was low, and there were unwanted toxic byproducts such as CHCl3 (1.7%) and CCl4 (13.8%). Thus catalysts were loaded in the plasma discharging zone to enhance removal efficiency and change product distribution. The catalysts were conducive to producing water-soluble products such as HCl. At the same time, the formation of some unwanted byproducts, CHCl3 and CCl4, were also inhibited. We found that using 11.5 kVpp plasma operating voltage combined with 200 mg Co3O4/HZSM-5 can lower the DCM concentration of the outlet stream from 1650 ppm to 53 ppm. Under this condition, the removal efficiency was about 96.7%, attaining permitted emissions.

Research progress of molecular sieve supported catalysts in catalytic oxidation of chlorine-containing volatile organic compounds

Chlorinated Volatile Organic Compounds (CVOCs) come from a wide range of sources and are common precursors of PM2.5 and ozone pollution, which pose a serious threat to the environment and have adverse effects on human health. Catalytic degradation is one of the effective methods to solve CVOCs pollution, which has the advantages of low operating temperature, less chlorine-containing by-products and high degradation efficiency. The core of this technology is to design and develop catalyst materials with excellent stability and catalytic performance. At present, molecular sieve catalysts have attracted extensive attention because of their acidity and unique pore structure. In this paper, the current research status of catalysts supported by molecular sieve, such as noble metals, transition metal oxides and perovskites, and their activity, acidity, stability and selectivity in CVOCs catalytic reactions were summarized and analyzed, and the future development direction of CVOCs molecular sieve supported catalysts was prospected.

Chlorinated volatile organic compounds (CVOCs) and 1,4-dioxane kinetics and equilibrium adsorption studies on selective macrocyclic adsorbents

Chlorinated volatile organic compounds (CVOCs) are often found in combination with 1,4-dioxane which has been used as a solvent stabilizer. It would be desirable to separate these compounds since biodegradation of 1,4-dioxane follows an aerobic pathway while anaerobic conditions are needed for biodegrading CVOCs. Conventional adsorbents such as activated carbon (AC) and carbonaceous resins have high adsorption capacities for 1,4-dioxane and CVOCs but lack selectivity, limiting their use for separation (Liu et al., 2019). In the current work, two macrocyclic adsorbents, β-CD-TFN and Res-TFN, were examined for selective adsorption of chlorinated ethenes in the presence of 1,4-dioxane. Both adsorbents exhibited rapid adsorption of the CVOCs and minimal adsorption of 1,4-dioxane. Res-TFN had a higher adsorption capacity for CVOCs than β-CD-TFN (measured linear partition coefficient, Kd 2140 -9750 L·kg−1 versus 192-918 L·kg−1 for 1,1, DCE, cis-1,2-DCE and TCE, respectively) and was highly selective for CVOCs(TCE Kd ∼117 Kd for 1,4-dioxane). By comparison, TCE and 1,4-dioxane adsorption on AC was approximately equal at 100 µg·L−1 and approximately 1/3 of the adsorption of TCE on the Res-TFN. The greater adsorption and selectivity of Res-TFN suggest that it can be used as a selective adsorbent to separate CVOCs from 1,4-dioxane to allow separate biodegradation.

Catalytic combustion of 1,2-dichloroethane via C[sbnd]C/C[sbnd]Cl bond cleavage through core-shell structured CeO2@TiO2 catalyst with excellent catalytic performances

A highly representative chlorinated volatile organic compound (Cl-VOCs), including 1,2-dichloroethane (1,2-DCE), which is extremely hazardous to human health and the environment. Improving the catalytic activity is very important for catalytic degradation of 1,2-DCE. In the work, CeO2@TiO2 catalyst which has a core-shell structure were made by a simple two-step hydrothermal synthesis method for 1,2-DCE oxidation. CeO2@TiO2 catalysts show higher activity (T90=275 °C), better carbon dioxide yield (YCO2=89.54 %) and lower by-products production than primitive CeO2 and TiO2. Due to its core-shell structure, CeO2@TiO2 shows the appropriate oxidation and reduction ability and appropriate acidity distribution, the powerful relationship between Ce and Ti elements in CeO2@TiO2 leads to effectively generate activity Ce3+and oxygen, which is greatly great enhance the activity of CeO2@TiO2 in 1,2-DCE catalytic oxidation. Based on the analysis of 1,2-DCE degradation performance and physical and chemical attributes, it proposes a way to catalyze 1,2-DCE catalytic oxidation over CeO2@TiO2. In addition, CeO2@TiO2 has good stability, and adding water vapor over the CeO2@TiO2 during 1,2-DCE degradation to promote 1,2-DCE conversion. The findings of this study might offer some new suggestions for creating catalysts that will destroy Cl-VOCs in their preparation and design.

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.

Evaluating groundwater ecosystem dynamics in response to post in-situ remediation of mixed chlorinated volatile organic compounds (CVOCs): An insight into microbial community resilience, adaptability, and metabolic functionality for sustainable remediation and ecosystem restoration

The in-situ remediation of groundwater contaminated with mixed chlorinated volatile organic compounds (CVOCs) has become a significant global research interest. However, limited attention has been given in understanding the effects of these remediation efforts on the groundwater microbial communities, which are vital for maintaining ecosystem health through their involvement in biogeochemical cycles. Hence, this study aimed to provide valuable insights into the impacts of in-situ remediation methods on groundwater microbial communities and ecosystem functionality, employing high-throughput sequencing coupled with functional and physiological assays. The results showed that both bioremediation and chemical remediation methods adversely affected microbial diversity and abundance compared to non-polluted sites. Certain taxa such as Pseudomonas, Acinetobacter, and Vogesella were sensitive to these remediation methods, while Aquabacterium exhibited greater adaptability. Functional annotation unveiled the beneficial impact of bioremediation on the sulfur cycle and specific taxa such as Cellvibrio, Massilia, Algoriphagus, and Flavobacterium which showed a significant positive relationship with dark oxidation of sulfur compounds. In contrast, chemical remediation showed adverse impacts on the nitrogen cycle with a reduced abundance of nitrogen and nitrate respiration along with a reduced utilization of amines (nitrogen rich substrate). The findings of this study offer valuable insights into the potential impacts of in-situ remediation methods on groundwater microbial communities and ecosystem functionality, emphasizing the need for meticulous consideration to ensure the implementation of effective and sustainable remediation strategies that safeguard ecosystem health and function.

Synergistic catalytic removal of NOx and chlorinated organics through the cooperation of different active sites

The synergistic removal of NOx and chlorinated volatile organic compounds (CVOCs) has become the hot topic in the field of environmental catalysis. However, due to the trade-off effects between catalytic reduction of NOx and catalytic oxidation of CVOCs, it is indispensable to achieve well-matched redox property and acidity. Herein, synergistic catalytic removal of NOx and chlorobenzene (CB, as the model of CVOCs) has been originally demonstrated over a Co-doped SmMn2O5 mullite catalyst. Two kinds of Mn-Mn sites existed in Mn-O-Mn-Mn and Co-O-Mn-Mn sites were constructed, which owned gradient redox ability. It has been demonstrated that the cooperation of different active sites can achieve the balanced redox and acidic property of the SmMn2O5 catalyst. It is interesting that the d band center of Mn-Mn sites in two different sites was decreased by the introduction of Co, which inhibited the nitrate species deposition and significantly improved the N2 selectivity. The Co-O-Mn-Mn sites were beneficial to the oxidation of CB and it cooperates with Mn-O-Mn-Mn to promote the synergistic catalytic performance. This work paves the way for synergistic removal of NOx and CVOCs over cooperative active sites in catalysts.

Deep Oxidation of Chlorinated VOCs by Efficient Catalytic Peroxide Activation over Nanoconfined Co@NCNT Catalysts.

The catalytic removal of chlorinated VOCs (CVOCs) in gas-solid reactions usually suffers from chlorine-containing byproduct formation and catalyst deactivation. AOP wet scrubber has recently attracted ever-increasing interest in VOC treatment due to its advantages of high efficiency and no gaseous byproduct emission. Herein, the low-valence Co nanoparticles (NPs) confined in a N-doped carbon nanotube (Co@NCNT) were studied to activate peroxymonosulfate (PMS) for efficient CVOC removal in a wet scrubber. Co@NCNT exhibited unprecedented catalytic activity, recyclability, and low Co ion leakage (0.19 mg L-1) for chlorobenzene degradation in a very wide pH range (3-11). The chlorobenzene removal efficiency was kept stable above 90% over Co@NCNT, much higher than that of nonconfined Co@NCNS (45%). The low-valence Co NPs achieved a continuous electron redox cycling (Co0/Co2+ → Co3+ → Co0/Co2+) and greatly promoted the O-O bond dissociation of PMS with the least energy (0.83 eV) inside the channel of Co@NCNT to form abundant HO• and SO4•-. Thus, the deep oxidation of chlorobenzene was achieved without any biphenyl byproducts from the coupling reaction. This study provided a new avenue for designing novel nanoconfined catalysts with outstanding activity, paving the way for the deep oxidation of CVOC waste gas via AOP wet scrubber.