Thermal Catalytic Oxidation Research Articles

Enhanced photo-assisted thermal catalytic oxidation of formaldehyde via abundant surface adsorbed oxygen in Co3O4 with the assistance of natural zeolite

Photo-assisted catalytic oxidation is a promising and sustainable method for the formaldehyde (HCHO) degradation. Catalyst loading and surface adsorbed oxygen species are common strategies to enhance the efficiency of photo-assisted catalytic oxidation. In this work, acid-treated zeolite-based natural zeolites (mordenite and stellerite) were used as supports, to obtain Co3O4-natural zeolite composites by impregnation and MOF-templated methods. Under the combined action of visible light irradiation and heat condition, the photo-assisted thermal catalytic performance of different composites was determined. Among these composites, the Co-AS (Co3O4-acid-treated stellerite) composite exhibited the best HCHO mineralization performance. The use of acid-treated stellerite as a catalyst carrier effectively reduced the crystallite size of Co3O4, improved its dispersibility, and increased the surface adsorbed oxygen species, contributing to enhanced catalytic efficiency. The in-situ DRIFTs results showed that the main intermediates of photo-assisted thermal catalysis degradation were dioxymethylene (DOM) and HCOO-. Additionly, the reusability performance of the composites was also investigated. Experimental results showed that the composite had good photo-assisted thermal catalytic performance and durability, making it a promising catalyst for indoor air purification.

Synthesis and Optimization of Foam Copper-Based CoMnOx@Co3O4/CF Catalyst: Achieving Efficient Catalytic Oxidation of Paraxylene.

This study successfully developed a foam copper (CF)-based CoMnOx@Co3O4/CF composite catalyst, achieving efficient thermal catalytic oxidation of paraxylene through multifactor optimization of synthesis conditions. At a Co:Mn molar ratio of 2:1 and a calcination temperature of 450 °C, the catalyst exhibited outstanding catalytic performance, with a T90 temperature as low as 246 °C, significantly lower than that of catalysts synthesized under other conditions. Additionally, BET, XPS, Raman, EPR, and H2-TPR test results indicate that the catalyst possesses a high specific surface area, abundant oxygen vacancies, a distribution of multivalent Co and Mn species, and a lower hydrogen reduction temperature, all of which contribute to the high catalytic activity of CoMnOx@Co3O4/CF. Furthermore, in situ DRIFTS confirmed that the oxidation of paraxylene on CoMnOx@Co3O4/CF follows the Mars-Van Krevelen (MvK) mechanism. The proposed reaction pathway begins with the oxidation of the methyl group on paraxylene, followed by the opening of the benzene ring and further oxidation to CO2 and H2O. The innovative structural design and excellent catalytic performance of this catalyst provide new insights and solutions for the industrial treatment of VOCs.

Selective recovery of platinum from spent catalysts to fabricate platinum/amorphous manganese oxide/corrugated silica carrier for formaldehyde removal

The efficient recovery and reutilization of spent Pt catalysts have two huge challenges in the metallurgical and chemical industries. Herein, platinum was selectively retrieved from spent Pt/γ-Al2O3 catalysts by a microwave-assisted aqua regia digestion strategy, and the as-obtained platinum extract was utilized to prepare a novel Pt/amorphous MnOx/corrugated silica carrier (Pt/MnOx/CSC) catalyst for formaldehyde removal. To decrease consumption of toxic aqua regia, the γ-Al2O3 in the spent catalysts was converted to chemically stabile α-Al2O3 via high-temperature calcination. The high Pt leaching efficiency of 98.31% was achieved at a digestion temperature of 110oC and aqua regia concentration of 40vol%. However, the high leaching temperatures and aqua regia concentrations caused the part dissolution of α-Al2O3, and thus decreased the Pt leaching efficiency. The CSC in the Pt/MnOx/CSC catalysts served as a support, while both the Pt nanoparticles and amorphous MnOx microspheres acted as active catalysts. The synergistical effects between the Pt and amorphous MnOx endowed the composite catalysts with excellent catalytic activity, and the HCHO removal efficiency reached 100% even after five cycle tests. On the one hand, the nanostructured MnOx microspheres provided great surface areas and rich oxygen vacancies for heterogeneous catalysis. On the other hand, the Pt nanoparticles not only enhanced the low-temperature reducibilities of MnOx, but also decreased the apparent activation energies of HCHO catalytic oxidation. This work provided a new strategy for the selective recovery of platinum from spent catalysts and the reutilization of Pt-based catalysts for the HCHO thermal catalytic oxidation.

The promotional mechanism of Ce substituted A-site cation over YMn2O5 for toluene oxidation

Mullite-type YMn2O5 oxides have considerable potential for the removal of VOCs due to the abundance of lattice oxygen and the stability. The present study investigated the promotional mechanism of toluene oxidation by A-site cations of YMn2O5 with Ce. Y1-xCexMn2O5 was synthetized by sol-gel method and characterized with various techniques. The results revealed that samples doping with Ce could notably enhanced the toluene oxidation performance, and the toluene conversion of Y0.97Ce0.03Mn2O5 was 32% higher than that of YMn2O5 at 300 ℃. Detailed characterizations demonstrated that the modification of Ce produced an interface between YMn2O5 and YMnO3, the strong interactions at the interface improved the content of Mn3+ and oxygen vacancies, which promoted the toluene oxidation performance. Furthermore, the intermediate of toluene oxidation on Y0.97Ce0.03Mn2O5 was performed by in-situ DRIFTS. Toluene was sequentially oxidized to benzaldehyde, benzoic acid and maleic anhydride, ultimately produced H2O and CO2. This work offered a material science basis for the development of manganese-based mullite in thermal catalytic oxidation of toluene.

Acid-activated α-MnO2 for photothermal co-catalytic oxidative degradation of propane: Activity and reaction mechanism

In order to further reduce the energy consumption of the conventional thermal catalytic oxidation system and improve the degradation efficiency of pollutants, photothermal synergistic catalytic oxidation (PTSCO) system was constructed in this paper with propane as simulated pollutant representing VOCs, and then the modified α-MnO2 catalysts were prepared by using the acid activation method, which were used for the catalytic oxidation of propane in PTSCO. The α-MnO2 with appropriate acid concentration possessed excellent low-temperature reducibility, abundant active oxygen species, fast oxygen migration rate and a large number of acid sites. The optimal catalyst, H0.05-MnO2, had a T90 of 204 °C in the PTSCO system, which reduced by more than 30 °C relative to the α-MnO2 (T90 of 235 °C). Moreover, H0.05-MnO2 demonstrated excellent water resistance and long-term stability (T = 45 h). It was shown that the combination of photocatalysis and thermocatalysis can improve propane degradation by examining the kinetics of propane degradation in the PTSCO system and the conformational relationship of propane degradation by catalysts. Furthermore, a multi-pathway synergistic mechanism between photocatalysis and thermocatalysis in the PTSCO system was proposed. This work provided a theoretical basis for the preparation of high-performance catalysts and the catalytic degradation of propane.

Energy‐Efficient Co‐production of Benzoquinone and H2 Using Waste Phenol in a Hybrid Alkali/Acid Flow Cell

AbstractIn both the manufacturing and chemical industries, benzoquinone is a crucial chemical product. A perfect and economical method for making benzoquinone is the electrochemical oxidation of phenol, thanks to the traditional thermal catalytic oxidation of phenol process requires high cost, serious pollution and harsh reaction conditions. Here, a unique heterostructure electrocatalyst on nickel foam (NF) consisting of nickel sulfide and nickel oxide (Ni9S8‐Ni15O16/NF) was produced, and this catalyst exhibited a low overpotential (1.35 V vs. RHE) and prominent selectivity (99 %) for electrochemical phenol oxidation reaction (EOP). Ni9S8‐Ni15O16/NF is beneficial for lowering the reaction energy barrier and boosting reactivity in the EOP process according to density functional theory (DFT) calculations. Additionally, an alkali/acid hybrid flow cell was successfully established by connecting Ni9S8‐Ni15O16/NF and commercial RuIr/Ti in series to catalyze phenol oxidation in an alkaline medium and hydrogen evolution in an acid medium, respectively. A cell voltage of only 0.60 V was applied to produce a current density of 10 mA cm−2. Meanwhile, the system continued to operate at 0.90 V for 12 days, showing remarkable long‐term stability. The unique configuration of the acid‐base hybrid flow cell electrolyzer provides valuable guidance for the efficient and environmentally friendly electrooxidation of phenol to benzoquinone.

Energy-Efficient Co-production of Benzoquinone and H2 Using Waste Phenol in a Hybrid Alkali/Acid Flow Cell.

In both the manufacturing and chemical industries, benzoquinone is a crucial chemical product. A perfect and economical method for making benzoquinone is the electrochemical oxidation of phenol, thanks to the traditional thermal catalytic oxidation of phenol process requires high cost, serious pollution and harsh reaction conditions. Here, a unique heterostructure electrocatalyst on nickel foam (NF) consisting of nickel sulfide and nickel oxide (Ni9S8-Ni15O16/NF) was produced, and this catalyst exhibited a low overpotential (1.35 V vs. RHE) and prominent selectivity (99 %) for electrochemical phenol oxidation reaction (EOP). Ni9S8-Ni15O16/NF is beneficial for lowering the reaction energy barrier and boosting reactivity in the EOP process according to density functional theory (DFT) calculations. Additionally, an alkali/acid hybrid flow cell was successfully established by connecting Ni9S8-Ni15O16/NF and commercial RuIr/Ti in series to catalyze phenol oxidation in an alkaline medium and hydrogen evolution in an acid medium, respectively. A cell voltage of only 0.60 V was applied to produce a current density of 10 mA cm-2. Meanwhile, the system continued to operate at 0.90 V for 12 days, showing remarkable long-term stability. The unique configuration of the acid-base hybrid flow cell electrolyzer provides valuable guidance for the efficient and environmentally friendly electrooxidation of phenol to benzoquinone.

Economics of enhanced methane oxidation relative to carbon dioxide removal

Mitigating short-term global warming is imperative, and a key strategy involves reducing atmospheric methane (CH4) due to its high radiative forcing and short lifespan. This objective can be achieved through methods such as oxidising methane at its source or implementing enhanced oxidation techniques to reduce atmospheric CH4 concentrations. In this study, we use a range of metrics to analyse both the impact and value of enhanced CH4 oxidation relative to carbon dioxide (CO2) removal on global temperature. We apply these metrics to a select group of model studies of thermal-catalytic, photocatalytic, biological and capture-based oxidation processes under different greenhouse gas (GHG) concentrations. Using a target cost of €220-1000/tCO2 for CO2 removal, our findings indicate that metrics valuing enhanced oxidation techniques based on their contribution to mitigating the long-term level of warming show these techniques are uncompetitive with CO2 removal. However, when using metrics that value enhanced oxidation of CH4 based on its impact on the immediate rate of warming, photocatalytic methods may be competitive with CO2 removal, whereas biofiltration, thermal-catalytic oxidation and capture-based units remain uncompetitive. We conclude that if the policy goal is to target the immediate rate of warming, it may be more valuable to incentivise CO2 removal and enhanced oxidation of methane under separate GHG targets.

Insight into recycling spent power ternary cathode materials: Towards preparation of Mn-based catalyst for efficient toluene removal

Both the resource utilization of spent power ternary lithium-ion batteries (LIBs) and degradation of volatile organic compounds (VOCs) by thermal catalytic oxidation are environmental concerns. In this study, a novel perspective is presented: the Mn-based composite metal oxide catalysts were synthesized via impregnation of spent ternary cathode materials for the thermocatalytic oxidative degradation of toluene gas. The results demonstrated that the optimal conditions for catalyst synthesis were a 2% Mn loading, a Co/Mn molar ratio of 0.4, and calcination at 500 ℃ for 6 h. The effectiveness of catalysts is determined by two inherent factors: the specific surface area and the presence of active sites on the surface. The degradation of toluene remained stable across various reaction environments, with the predominant degradation mechanism being Marks-Van-Kreven (MVK) model. The toluene undergoes oxygenation on the catalyst in this pathway, resulting in the formation of H2O, CO2, and intermediates containing benzene rings; and simultaneously, the catalyst is regenerated. The present study offers a valuable reference for the resource utilization of spent ternary LIBs and advances the development of catalysts for efficient degradation of VOCs.

Photothermal dependence on catalytic activity and selectivity of HMF and benzyl alcohol oxidation over Pd/1D‐TiO2 nanotubes

AbstractBACKGROUNDPhotothermal catalytic oxidation technology for synthesis of high value‐added chemicals has become a hot topic of research at home and abroad. As a special structure, titania (TiO2) nanotubes (Ti‐NTs) possess larger specific surface area and adsorption capacity, which have shown great application prospects in photothermal catalytic oxidation.RESULTSIn this work, high‐performance palladium (Pd‐Ti‐NTs catalyst were prepared and applied to the photothermal catalytic oxidation of 5‐hydroxymethyl (HMF) and benzyl alcohol. The photothermal dependence on catalytic activity and selectivity of HMF and benzyl alcohol oxidation was studied in detail. The results revealed that compared with thermal catalytic oxidation, the catalysts showed significantly higher conversions of both benzyl alcohol and HMF under light. in particular, HMF conversion increase from 55.6% to 99.7%. Aldehyde oxidation is inhibited by alcohol and can be dramatically promoted by light radiation. This is probably because alcohol can inhibit the adsorption of aldehyde, and this inhibiting effect is weakened through light radiation, thus promoting the oxidation of aldehydes. Therefore, the selectivity of the final products 2,5‐furandicarboxylic acid (FDCA) and benzoic acid were dramatically increased in both systems under light radiation, and the selectivity for FDCA was obviously increased from 5.8% to 61.3%, and the yield reached 61.0%, which is higher than that of most of the reported Pd‐TiO2‐based catalysts for FDCA.CONCLUSIONSIn this paper, we verify that Pd‐Ti‐NTs could preferentially promote the conversion of aldehydes to acids in the presence of light, and obtained catalysts with high catalytic performance and high stability for benzyl alcohol and HMF oxidation. © 2024 Society of Chemical Industry (SCI).

Engineering the CuO/MnO2 interface with multivalent conversion for low-temperature and efficient CO oxidation

A novel interface of MnO2 with CuO with multivalent conversion is fabricated by the deposition-precipitation method for low-temperature and efficient CO oxidation. It is found that the temperature for CO thermal-catalytic oxidation to reach a complete conversion significantly decreases to 105 °C for the CuO/MnO2. A combination of experimental and theoretical studies demonstrates the successful formation of the CuO/MnO2 interface, inducing a pronounced effect that promotes CO oxidation. The CuO/MnO2 interface leads to the formation of Cu-O-Mn, a superior redox system with multivalent conversion (Cu+ + Mn4+ ↔ Cu2+ + Mn3+, Cu+ + Mn3+ ↔ Cu2+ + Mn2+), abundant active sites, excellent ability to activate O2, the rapid oxygen transfer, and more suitable adsorption energy for O2, CO, and CO2. These characteristics are advantageous to CuxO-MnxOy for achieving a 100 % removal of CO at a lower temperature. Furthermore, the computational study reveals that the CO oxidation process follows two mechanistic pathways (Eley-Rideal (E-R) and Mars-van Krevelen (M-K)), indicating that there is no competitive adsorption of CO and O2 on the CuO/MnO2. This study shows that the interface created between suitable metal oxides can improve the catalytic performance and provides new perspective for catalyst design and performance enhancement mechanisms.

Unveiling the mechanism of thermal catalytic oxidation of HCHO from the kiln exhaust gas using Sc-decorated Cr2CO2-MXenes

Sc/Cr2CO2 is a novel efficient thermal catalyst for HCHO oxidation.

Induced synthesis of CeO2 with abundant crystal boundary for promoting catalytic oxidation of gaseous styrene

Oxygen vacancies can be used as adsorption-activation sites for reactants, and they can also be used to regulate the electronic structure of catalysts in environmental catalytic oxidation. In the current research on thermal catalytic oxidation, one of the most important issues is the further regulation and design of superior CeO2 catalysts with abundant oxygen vacancies. Herein, this study reveals a crystallization-inducing strategy to manipulate the exposed morphology, crystal planes, and crystal boundary of CeO2 catalysts by adding styrene at the synthesis stage. The characterization results demonstrate that the induced activation of styrene can lead to the formation of abundant Ce-Ce crystal boundaries with rich oxygen vacancies in CeO2-C8H8 catalysts. Among the synthesized induced CeO2-C8H8 catalysts, the short bar-like CeO2-C8H8-130–24 catalyst presented better catalytic activity for styrene oxidation (T90 = 149 °C). Moreover, it is found that such a morphological and crystal boundary structure evolution can improve the durability of CeO2-C8H8-130–24. This study provides a novel strategy for modulating the concentration of oxygen vacancies in CeO2 catalysts.

Photothermal catalytic selective oxidation of isobutane to methacrylic acid over keggin-type heteropolyacid

Thermal and photothermal catalytic selective oxidation of isobutane to methacrylic acid (MAA) are comparatively studied over a keggin-type Cs2.9Cu0.34V0.49PMo12O40 heteropolyacid acid. An introduction of light was observed to enhance both the i-C4H10 conversion and the MAA selectivity, and consequently the MAA formate rate, particularly at low temperatures. Characterization results show that oxidation of methacrolein (MAL) to MAA is the rate-limiting step while UV light illumination promotes the oxidation of σ-bonded MAL with OH groups to σ-bonded MAA on the catalyst surface. These results demonstrate a synergistic effect of thermal catalysis and photocatalysis in selective oxidation of isobutane to MAA, which suggests photothermal catalysis as a promising strategy to catalyze the selective oxidation of higher hydrocarbons at relative mild reaction conditions.

Catalytic oxidation degradation of volatile organic compounds (VOCs) – a review

Abstract Volatile organic compounds (VOCs) are considered one of the significant contributors to air pollution because they are toxic, difficult to remove, come from a wide range of sources, and can easily cause damage to the environment and human health. There is an urgent need for effective means to reduce their emissions. The current treatment technologies for VOCs include catalytic oxidation, adsorption, condensation, and recovery. Catalytic oxidation technology stands out among the others thanks to its high catalytic efficiency, low energy requirement, and lack of secondary pollution. The difficulty of this technology lies in the development of efficient catalysts. The research on loaded noble metal catalysts and non-noble metal oxide catalysts in this area over the past few years is briefly described in this work. Firstly, the catalytic destruction mechanism of organic volatile compounds is introduced. Secondly, the effects of structural modulation during catalytic oxidation, such as the adjustment of noble metal particle size and morphology, metal doping, and defect engineering, on the conformational relationships are discussed. Finally, the challenges faced by thermal catalytic oxidation for the degradation of VOCs are discussed, and the prospects for its development are presented.

Biosynthesis of Au/CuO catalyst with Syringa oblata Lindl. leaf extract for efficient selective oxidation of glycerol to 1,3-dihydroxyacetone

Efficient conversion of glycerol to 1,3-dihydroxyacetone (DHA) is the affirmation and guarantee of the feasible development of biodiesel industry, but the biocompatibility of catalyst must be considered due to the wide application of DHA in food and medicine industries. In this work, an environmentally benign biosynthesis approach with Syringa oblata Lindl. (SoL) leaf extract was employed to fabricate Au/CuO catalysts for the oxidation of glycerol to DHA. The biosynthesized SoL-Au/CuO catalysts were characterized and the effects of plant extracts concentration, gold loading, calcination temperature and reaction conditions on the catalytic performance were systematically analyzed. High catalytic performance with glycerol conversion rate of 95.7% and DHA selectivity of 77.9% can be attained under optimum conditions. This work provides the first example of preparing biocompatible catalyst for the thermal catalytic oxidation of glycerol to DHA, which can not only reach efficient conversion of glycerol and selectivity to DHA, but also is simple, green, environmentally friendly, and promising.

Metal-anchoring, metal oxidation-resistance, and electron transfer behavior of oxygen vacancy-rich TiO2 in supported noble metal catalyst for room temperature HCHO conversion

Thermal catalytic oxidation at room temperature using a noble metal catalyst is a rapid, stable, and efficient removal strategy for HCHO, a ubiquitous indoor air pollutant. However, the catalytic oxidation optimization through the support defect control has been barely explored. We prepared an oxygen vacancy-rich anatase TiO2 (VO-TiO2) as electron transfer catalyst support for the efficient catalytic conversion of HCHO to CO2 and H2O. VO-TiO2, prepared by chemical vapor condensation with post heat treatment, exhibits void-embedded nanostructures and electron paramagnetic activity, which governs the deposition pattern of Pt nanoparticles upon the impregnation. Pt/VO-TiO2 (0.086 wt% Pt) converted 100% of 10 ppm HCHO at room temperature and 200,000 cm3 h−1 gcat−1 GHSV in >250 min. The X-ray absorption (XAS) studies of used catalysts confirmed the conservation of metallic state of Pt only in oxygen vacancy-rich anatase TiO2 (VO-TiO2). The First-principles density-functional theory calculations revealed that the excess electrons at the oxygen vacancies in VO-TiO2 stabilize the otherwise-vulnerable Pt nanoparticles. This study demonstrates an effective defect control strategy for transforming a TiO2 support into a dynamic electron transfer catalyst platform.

Experimental study and kinetic model analysis on photothermal catalysis of formaldehyde by manganese and cerium based catalytic materials

ABSTRACT Modern people spend more and more time in cars in their daily lives, and the pollution of formaldehyde in the car may directly affect people’s health. Thermal catalytic oxidation technology by solar light is a potential way to purify formaldehyde in cars. MnOx-CeO2 was prepared by the modified co-precipitation method as the main catalyst, and the basic characteristic (SEM, N2 adsorption, H2-TPR, UV-visible absorbance) were also analyzed in detail. The experimental study was set up to simulate the solar photothermal catalysis of formaldehyde in-car environment. The results showed that the higher the temperature in the experimental box (56.7 ± 0.2°C, 62.6 ± 0.2°C, 68.2 ± 0.2°C), the better the formaldehyde degradation by catalytic effect (formaldehyde degradation percentage: 76.2, 78.3, 82.1). With increase of the initial formaldehyde concentration (200 , 500 , 1000 ), the catalytic effect first increased and then decreased (formaldehyde degradation percentage: 63, 78.3, 70.6). The catalytic effect risen gradually with the increase of load ratio (10, 20, and 40), and the formaldehyde degradation percentages were 62.8, 78.3, and 81.1, respectively. According to the expressions of the Eley-Rideal (ER) model, the Langmuir-Hinshelwood (LH) model, and the Mars-Van Krevelen (MVK) model, the experimental results were fitted and verified, and it was found that the ER model had a high degree of fit. It is more suitable to explain the catalytic mechanism of formaldehyde by MnOx-CeO2 catalyst in the experimental cabin, where formaldehyde is in the adsorption state and oxygen is in the gas phase. Implications: Judging from the current research status, vehicles have become an indispensable mode of travel for people, and the air quality in the vehicle is not optimistic. Most vehicles generally have the phenomenon of excessive formaldehyde. The characteristic of formaldehyde in the car is the continuous release, especially in the hot summer, the temperature inside the car rises sharply under the sun radiation. At this time, the formaldehyde concentration exceeds the standard by 4 to 5 times, which can cause great damage to the health of the passengers. In order to improve the air quality in the car, it is necessary to adopt the correct purification technology to degrade formaldehyde. The problem brought by this situation is how to effectively use solar radiation and high temperature in the car to degrade formaldehyde in the car. Therefore, this study uses the thermal catalytic oxidation technology to catalyze the degradation of formaldehyde in the high temperature environment of the car in summer. The selected catalyst is MnOx-CeO2, mainly because manganese oxide (MnOx) itself is the most effective catalyst for volatile organic compounds (TCO) among transition metal oxides, and CeO2 has excellent oxygen storage and release capacity and Oxidation activity, which helps to improve the activity of MnOx. Finally, the effects of temperature, initial concentration of formaldehyde and catalyst loading on the experiment were explored, and the kinetic model of thermal catalytic oxidation of formaldehyde with MnOx-CeO2 catalyst was analyzed to provide technical support for the future application of this research in practice.

Metal oxide/activated carbon composites for the reactive adsorption and catalytic oxidation of formaldehyde and toluene in air

The synergistic effect of ‘reactive adsorption and catalytic oxidation (RACO)’ has been investigated to develop an efficient method to remove volatile organic compounds (VOCs: formaldehyde (FA) + toluene) using an amorphous-manganese dioxide-activated carbon (Am-MnO2-AC) composite. The RACO of FA and toluene onto Am-MnO2-AC was examined individually and as a mixture at multiple-isothermal conditions from room temperature (RT) to 300 °C. At RT, the values for 10% adsorption breakthrough volume (BTV10%) of single FA and toluene by Am-MnO2-AC were 45.9 and 152 L g−1, respectively, approx. 1.3-fold higher than those for their mixture. The BTV10% values for FA measured in single and mixture were 270–280 times higher than their pristine AC counterparts. The RACO performance of Am-MnO2-AC was investigated more intensively against a dual component system in reference to its crystalline forms (e.g., δ-MnO2) and two other metal-doped forms (i.e., cobalt and silver). Accordingly, Am-MnO2-AC exhibited the highest catalytic reactivity so as to achieve the complete oxidation of FA and toluene (as individual components) into carbon dioxide (CO2) at 100 and 275 °C, respectively. The thermal catalytic oxidation of FA and toluene onto Am-MnO2-AC was suggested to follow the Langmuir-Hinshelwood mechanism. The enhanced RACO performance of Am-MnO2-AC was ascribed to its higher surface porosity and higher concentration of oxygen vacancies (e.g., Mn3+/Mn4+ of 0.707 and adsorbed oxygen (OA)/lattice oxygen (OL) of 1.79). The present study is expected to provide deep insights into the practical application of metal oxide/AC composites for cleaner indoor air quality.

Surface Modification of GdMn2O5 for Catalytic Oxidation of Benzene via a Mild A-Site Sacrificial Strategy

Thermal catalytic oxidation technology is an effective way to eliminate refractory volatile organic pollutants, such as Benzene. Nevertheless, a high reaction temperature is usually an obstacle to practical application. Here, GdMn2O5 mullite (GMO-H) catalyst with disordered surface Gd-deficient and oxygen-vacancy-rich concentrations was synthesized via a controllable low-temperature acid-etching route. Results show that the preferentially broken Gd-O bond is conducive to exposing more Mn-Mn active sites, which Gd species covered. The affluent surface oxygen vacancies supply sufficient adsorption sites for oxygen molecules, facilitating the oxygen cycles during Benzene catalytic oxidation. Furthermore, surface exposed Mn3+ species were oxidized to Mn4+, which is beneficial to increase catalytic activity at a lower temperature. Compared with the conventional GdMn2O5, the reaction temperature for removing 90% Benzene over GMO-H was dropped from 405 to 310 °C with WHSV of 30,000 mL g−1 h−1. Significantly, during a 72 h catalytic test, the catalytic activity remains constant at 90% of the Benzene removal at 300 °C, indicating excellent activity stability. This work reported an efficient approach to preparing manganese-base mullite thermal catalyst, providing insight into the catalytic oxidation of Benzene.