Search

Featured Application: This work supplies a systematical comparison study on various typical noble metal catalysts with an exploration of the potential for CVOC destruction, which would supply an overall view of universal applicability for the practical operation of noble metals. Understanding the reaction path and mechanism of chlorinated volatile organic compound (CVOC) destruction is important for designing efficient catalysts, especially for the application of noble metal-based materials. Herein, several typical noble metals, Ru, Rh, Pt, Pd, Au, and Ir, supported on γ-Al2O3 catalysts were synthesized by the hydrazine hydrate reduction method for 1,2-dichloroethane (1,2-DCE) elimination. Various character measurements were conducted, and the results suggest that the high-valence state of noble metals is beneficial for the 1,2-DCE reaction as it enables the enhancement of the mobility of the surficial active oxygen species of catalysts. Among the noble metals, Ru/γ-Al2O3 expresses superior catalytic reactivity, with a 90% pollutant conversion rate at 337 °C, and competitive CO2 selectivity, 99.15% at the temperature of total oxidation. The distribution of by-products and the degradation routes were analyzed online by GC-ECD and in situ diffuse reflectance infrared spectroscopy, which may provide helpful insight for the future application of noble metal-based catalysts for CVOC elimination in industrial fields. [ABSTRACT FROM AUTHOR]

• The CeO 2 @TiO 2 core-shell catalysts were prepared by a two-step hydrothermal synthesis method. • The CeO 2 @TiO 2 catalyst showed the excellent catalytic activity and stability for 1,2-DCE. • 1,2-DCE total destruction achieved over CeO 2 @TiO 2 at 275 °C. • The synthetic catalysts have good stability due to the inhibitory of by-products caused by the C Cl/C C keys. 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, CeO 2 @TiO 2 catalyst which has a core-shell structure were made by a simple two-step hydrothermal synthesis method for 1,2-DCE oxidation. CeO 2 @TiO 2 catalysts show higher activity (T 90 =275 °C), better carbon dioxide yield (Y CO2 =89.54 %) and lower by-products production than primitive CeO 2 and TiO 2. Due to its core-shell structure, CeO 2 @TiO 2 shows the appropriate oxidation and reduction ability and appropriate acidity distribution, the powerful relationship between Ce and Ti elements in CeO 2 @TiO 2 leads to effectively generate activity Ce3+and oxygen, which is greatly great enhance the activity of CeO 2 @TiO 2 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 CeO 2 @TiO 2. In addition, CeO 2 @TiO 2 has good stability, and adding water vapor over the CeO 2 @TiO 2 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. [Display omitted] [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Hierarchically micro-mesostructured K-(Al)SiO 2 supports were successfully prepared. • Monodispersed Pt was created by ethylene glycol reduction and colloid impregnation. • Pt/K-Al-SiO 2 nanorod catalysts exhibit superior performance for MEK oxidation. • Role of K and Al and structure-activity relationships of catalysts were studied. • MEK destruction mechanism was investigated and proposed by in situ DRIFTS and DFT. Abstract Hierarchically micro-mesostructured Pt/K-Al-SiO 2 catalysts with regular nanorod (Pt/KA-NRS) and spherical nanoflower-like (Pt/KA-SNFS) morphologies were prepared. The existence of Al atoms generates Brønsted acid sites and reduces silanol groups over the supports, promoting the dispersion of Pt nanoparticles and stability of catalysts. Potassium atoms balance the negative charge of supports and enhance O 2 mobility. The Pt/KA-NRS catalysts exhibit unexceptionable low temperature activity, CO 2 selectivity, and stability for MEK oxidation. Amongst, 0.27 wt.% Pt/KA-NRS completely converts MEK at just 170 °C (activation energy as low as 37.22 kJ· mol−1), more than 100 °C lower than other typical Pt/Pd supported catalysts reported in the literature. Diacetyl and 2,3-butandiol are the main intermediates during MEK activation, which convert into H 2 O and CO 2 through aldehydes and acids. The excellent catalytic activity of Pt/KA-NRS is ascribed to their regular morphology, high Pt0 content and dispersion, excellent MEK adsorption capacity and superior O 2 /CO 2 desorption capability under low temperature. [ABSTRACT FROM AUTHOR]

Three-dimensional ordered meso-macroporous La 0.7 Sr 0.3 Fe 0.5 Co 0.5 O 3 (3DOM LSFCO)-supported Co 3 O 4 catalysts were designed and prepared via a PMMA-templating strategy for the total oxidation of 1,2-dichloroethane (1,2-DCE). The physicochemical properties of all synthesized samples were characterized by XRD, FE-SEM, TEM, HAADF-STEM, low-temperature N 2 sorption, XPS, H 2 -TPR, and in situ FT-IR. The introduction of Co 3 O 4 increases the generation rate of oxygen vacancy, playing a crucial role in adsorption and activation of oxygen species. The special 3DOM structure of perovskite-type oxide promotes 1,2-DCE molecules to effectively and intimately contact with the surface adsorbed oxygen over supported catalysts and further accelerates the redox process. Compared with pure LSFCO, all the Co 3 O 4 supported catalysts show superior catalytic performance with reaction rate increases from 5.53 × 10 −12 to 2.29 × 10 −11 mol g −1  s −1 and E a decreases from 74.7 to 22.6 KJ mol −1 . Amongst, the 10Co 3 O 4 /3DOM LSFCO catalyst exhibits the best catalytic activity, highest resistance to chlorine poisoning and lowest by-products concentration because of the largest amount of surface adsorbed oxygen. CO 2 , CO, HCl, and Cl 2 are the main oxidation productions, while some typical reaction intermediates such as vinyl chloride, 1,1,2-trichloroethane and trichloroethylene are also observed, especially over the 3DOM LSFCO sample. Furthermore, the reaction mechanism of 1,2-DCE oxidation over obtained catalysts was proposed based on the results of gas chromatography, in situ FT-IR, and on-line MS. It is believed that the Co 3 O 4 /3DOM LSFCO are promising catalysts for the total removal of chlorinated volatile organic compounds. [ABSTRACT FROM AUTHOR]

Highly crystalline flake-like CuCeO 2 − δ composites (strCC x ) with large specific surface area and developed mesoporosity were prepared using an economic and effective bio-template route. Modified starch with abundant surface carboxyl groups was adopted as the chelating agent and template for metal cations immobilization via electrostatic attraction predominately based on the process of –COO − ⋯Cu 2+ and –COO − ⋯Ce 3+ . Physicochemical properties of prepared materials were systematically explored by FT-IR, XRD, TG, N 2 adsorption/desorption, FE-SEM, TEM, H 2 -TPR, O 2 -TPD, XPS, DRUV–Vis, and XAFS techniques. Propanal as a typical oxygen-contained VOC was adopted as the probe pollutant to evaluate the catalytic performance of synthesized materials. Characterization results reveal that plenty of copper ions in composite oxides are incorporated into CeO 2 lattice, which produces oxygen vacancies and enhances metal reducibility. Both specific surface area and pore volume of strCC x samples decreased with the increasing of Cu loading. The flake-like CuCeO 2 − δ sample (Cu/(Cu + Ce) = 0.15) with highest specific surface area (108.2 m 2 /g) and surface oxygen concentration is indentified as the most active catalyst with propanal totally destructed at 230 °C. The introduction of H 2 O has a negative effect on propanal removal, and the synthesized catalyst has high tolerance to moisture. In conclusion, the specific surface area and surface oxygen density are two vital factors governing the catalytic activity of composite catalysts. [ABSTRACT FROM AUTHOR]

Mesostructured CuMnCeO catalysts were prepared and tested in chlorobenzene destruction. Mn and Cu phases enter CeO matrix with a fluorite-like structure to form Cu-Mn-O-Ce solid solution. Both synthesis protocol and metal-doping content affect the metal state, reducibility, and oxygen distribution of composites. The ccc sample exhibits the highest activity with 90 % of chlorobenzene oxidized at around 250 °C. Enhanced oxygen concentration and mobility, and abundant oxygen vacancy promote the desorption of adsorbed Cl, which guarantees the superior stability of CuMnCeO. Incorporation of CuO and MnO effectively inhibits the formation of organic byproducts, such as phenolates, maleates, and o-benzoquinone, especially at elevated temperatures. [ABSTRACT FROM AUTHOR]

Mesostructured ACeO x (A = Co, Cu, Fe, Mn, or Zr) composites with large specific surface area and developed mesoporosity were prepared by inorganic metal precursor spontaneous precipitation (IMSP) method. Influences of catalyst surface area, pore structure, reducibility, and active oxygen concentration on catalytic performance were studied. Both preparation route and metal precursor type affect metal active site dispersion, and the IMSP is a desirable approach for synthesis of metal composites with homogeneous active phase distribution. The original crystalline structure of CeO 2 is well maintained although parts of transition metal cations are incorporated into its framework. The forming of A n + –O 2 − –Ce 4 + connections in ACeO x catalysts could reduce the redox potential of metal species, allowing effective redox cycles during oxidation reactions. CuCeO x demonstrates powerful catalytic efficiency with 99% of chlorobenzene (CB) destructed at 328 °C, which is much lower than the other ACeO x oxides and Cu-doped catalysts synthesized via the incipient impregnation and coprecipitation methods (T 99 > 405 °C). The active site reducibility is the foremost activity determining factor for CB destruction. [ABSTRACT FROM AUTHOR]

Highlights: [•] A facile and universal self-precipitation route for mesoporous metal oxides preparation. [•] CuCeO x catalysts with high surface area and homogeneous mesostructure. [•] Catalysts combined promoted reducibility and surface oxygen concentration. [•] Mesostructured metal oxides with superior low-temperature catalytic efficiency. [•] Catalysts possess remarkable enhanced reaction rate and selectivity. [Copyright &y& Elsevier]

Catalytic oxidation is widely used in pollution control technology to remove volatile organic compounds. In this study, Pd/ZSM-5 catalysts with different Pd contents and acidic sites were prepared via the impregnation method. All the catalysts were characterized by means of N 2 adsorption-desorption, X-ray fluorescence (XRF), H 2 temperature programmed reduction (H 2 -TPR), and NH 3 temperature programmed desorption (NH 3 -TPD). Their catalytic performance was investigated in the oxidation of butyl acetate experiments. The by-products of the reaction were collected in thermal desorption tubes and identified by gas chromatography/mass spectrometry. It was found that the increase of Pd content slightly changed the catalytic activity of butyl acetate oxidation according to the yield of CO 2 achieved at 90%, but decreased the cracking by-products, whereas the enhancement of strong acidity over Pd-based catalysts enriched the by-product species. The butyl acetate oxidation process involves a series of reaction steps including protolysis, dehydrogenation, dehydration, cracking, and isomerization. Generally, butyl acetate was cracked to acetic acid and 2-methylpropene and the latter was an intermediate of the other by-products, and the oxidation routes of typical by-products were proposed. Trace amounts of 3-methylpentane, hexane, 2-methylpentane, pentane, and 2-methylbutane originated from isomerization and protolysis reactions. [ABSTRACT FROM AUTHOR]

Abstract: Catalytic oxidation is a widely used pollution control technology for removing volatile organic compounds. Pd–Ce/ZSM-5 catalysts with different Ce contents were prepared by a co-impregnation method, and their catalytic performance was investigated for the oxidation of methyl ethyl ketone (MEK). The by-products of the reaction were monitored using gas chromatography and collected in thermal desorption tubes, which were further analyzed by gas chromatography/mass spectrometry. The PdCe9.6/ZSM-5 catalyst displayed the highest catalytic efficiency, as a consequence of a higher amount of strong acid sites and a superior PdO-Pd redox cycle in the presence of a CeO2 additive. The introduction of CeO2 enriched the by-product species. The formation mechanisms and oxidation routes of typical by-products, such as methyl acetate, 1-penten-3-one and 3-buten-2-one, 3-methyl, during MEK oxidation over Pd–Ce/ZSM-5 catalysts was also analyzed. CH3* species that formed on the catalyst were identified as reaction intermediaries. Trace amounts of acetic acid and methyl vinyl ketone were also detected and were further oxidized to methyl acetate, 1-penten-3-one and 3-buten-2-one, 3-methyl. [Copyright &y& Elsevier]

ABSTRACT This work aimed at investigating the reaction behaviors and kinetics of catalytic oxidation of benzene, toluene, and ethyl acetate over Pd/SBA-15 catalyst. Results for single components show that toluene ( T50 = 185-215 °C) is more easily oxidized than ethyl acetate ( T50 = 220-255 °C) and benzene ( T50 = 215-290 °C). The conversion of toluene and benzene decreases continuously as their inlet concentrations are increased. The conversion of ethyl acetate increases slightly when its feed concentration increases in a small range, while this trend is not kept when the concentration is further raised. Results for multicomponents reveal that the presence of benzene or toluene inhibits the conversion of ethyl acetate, and the aromatic hydrocarbons inhibit each other. Ethyl acetate has an inhibitory effect on benzene, while it is interested to note that the promotion behaviors are observed for toluene. Kinetic results of all studied volatile organic compounds obtained in the absence of diffusion limitations are fit to the Mars-van Krevelen expressions. © 2011 Curtin University of Technology and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: A series of micro/mesoporous hybridized materials with coke-resistant ZSM-5 and three-dimensional large pore KIT-6 as their micro- and mesoporous components were synthesized and investigated for toluene deep oxidation. The characterization results show that most of Al atoms are tetrahedrally coordinated in the framework of the samples, and the ratio of ZSM-5 to KIT-6 can be systematically controlled by varying the Si/Al molar ratio in the synthesis mixture. The acid sites over the supports are favorable for Pd nanoparticle dispersion and metallic Pd oxidation due to their electrophilic characters. All Pd supported composite materials are found to be powerful catalysts for the total oxidation of toluene. Particularly, Pd/ZK-50 possesses the highest catalytic activity with 90% toluene decomposition at 197°C, this temperature is much lower than that of Pd/KIT-6 (T 90 =234°C). CO2 desorption capability has positive effects on catalytic activity, while the influence of toluene adsorption property is negligible. The superior activity of the composite catalysts can be ascribed to the cumulative of specific surface area, support acidity, Pd particles dispersion and CO2 desorption capability. [Copyright &y& Elsevier]

Abstract: A series of novel Pd/Co3AlO catalysts derived from hydrotalcite-like compounds (HTlcs) have been prepared and investigated for total oxidation of toluene. The HTlcs phase Co–Al precursors were prepared by coprecipitation method and Pd active species were introduced by different approaches, i.e., impregnation (IMP), wet ion exchange (WIE) or directly at coprecipitation stage (COP). It is found that all hydrotalcite-derived Pd/Co3AlO catalysts are much more active than the Pd/Co3AlO catalyst prepared via traditional thermal combustion method (TCB) in toluene elimination. The activities of all synthesized catalysts obey the following sequence: Pd/Co3AlO (COP)>Pd/Co3AlO (WIE)≥Pd/Co3AlO (IMP)>Pd/Co3AlO (TCB). Excellent catalytic activities of the novel hydrotalicite-derived Pd/Co3AlO catalysts could be contributed to their high surface area, small mean crystallized size of support and highly dispersed PdO particles. Besides, they are well positively associated with catalyst reducibilities and the amounts of oxygen vacancies. According to the XPS, TEM and TPR results, it was found that the strong synergistic effect between Co3O4 and PdO, but not the amount of the surface palladium species which are generally believed to be the active sites, is the main factors determining the catalytic activity in this work. The stability tests indicate that all Pd/Co3AlO catalysts have no obvious deactivation, and some catalysts even show improved activities during the reaction process due to the emergence of metal Pd. [ABSTRACT FROM AUTHOR]

Abstract: In this study, mesoporous SBA-15 supported Pd catalysts were synthesized through impregnation and grafting approaches. Moreover, the influences of different solvents (ethanol, H2O, tetrahydrofuran, dimethyl sulphoxide and N,N-dimethylformamide) on the dispersion of supported Pd nanoparticles were also systematically investigated. The prepared materials were comprehensively explored by various techniques, including XRD, EDS, ICP-OES, H2 chemisorption, N2 adsorption/desorption, TG-DSC, FT-IR, TEM and STEM. It is found that the traditional impregnation method has some disadvantages in obtaining highly dispersed Pd active phase. Whereas, the grafting method could highly disperse Pd nanoparticles within the mesoporous channels of support material, and the grafting procedure should be promising in designing highly dispersed Pd particles on the silica-based mesoporous materials. The catalyst prepared via the grafting procedure possesses much higher activity and selectivity than that prepared by impregnation method for deep catalytic oxidation of toluene. [Copyright &y& Elsevier]

[Display omitted] • CuO x /MnO 2 catalysts with different crystal phases of MnO 2 were synthesized. • CuO x / α-MnO 2 catalyst showed excellent catalytic activity in NO reduction and CO oxidation. • The presence of CO enhanced the NH 3 -SCR catalytic activity of catalyst. • Mechanism model for NO reduction and CO oxidation was proposed. NO and CO are two primary pollutants in the sintering flue gas emission, posing significant challenges for the treatment. Under oxygen-enriched conditions, CO was easily oxidized to CO 2 before participating in CO-SCR reaction as a reducing agent. Consequently, NH 3 -SCR technology coupled with CO oxidation reaction is a promising approach for simultaneous NO and CO removal. In this study, a series of bifunctional CuO x /MnO 2 catalysts were synthesized using a combine of hydrothermal and wet impregnation methods, and their catalytic performance for simultaneous removal of NO and CO was assessed. CuO x /α-MnO 2 catalyst displayed outstanding catalytic activity for both NO and CO, achieving over 80 % NO removal efficiency and 96 % CO conversion rate at 150 °C, while CuO x /β-MnO 2 catalyst exhibited poor catalytic activity in the entire temperature range. Moreover, the interplay between the NH 3 -SCR and CO catalytic oxidation reactions was also explored. XPS results revealed that the concentration of Mn4+ and Cu+ species significantly influenced the catalytic activity of the catalysts for the simultaneous removal of NO and CO. Particularly, the presence of Mn4+ species promoted "fast SCR" reaction, whereas Cu+ species demonstrated higher reactivity for both NO reduction and CO oxidation. In situ DRIFTS analysis of transient reactions revealed that the L-H mechanism was followed over CuO x /α-MnO 2 catalyst in the NH 3 -SCR reaction, while both the M-K and L-H mechanisms were observed in CO catalytic oxidation reaction. [ABSTRACT FROM AUTHOR]

A series of carbon-supported Cu Co oxide catalysts (Cu-Co/C) were prepared via the combination methods of impregnation and pyrolysis using Co-doped Cu-based metal organic framework (Cu 3 (BTC) 2 ·3H 2 O, Cu-BTC) precursor. Physicochemical properties of prepared catalysts were characterized by using various technologies and toluene was chosen as the probe molecule to evaluate their catalytic performance. Results revealed that the successive calcination in Ar and air was conducive to the formation of 3D porous carbon matrix and homogeneous elemental dispersion. The Cu-Co/C catalysts with spinel structure exhibited higher catalytic activity than that of Cu-500/C material. Moreover, CuCo 0.5 /C material exhibited superior catalytic durability and water resistance in catalytic oxidation of toluene. The excellent catalytic performance of CuCo 0.5 /C was mainly related to large specific surface area, high amounts of surface chemisorbed active oxygen and high ratio of Co2+/Co3+. Unlabelled Image • Cu-Co/Carbon catalysts were prepared using Co-doped Cu-MOF precursor. • Porous carbon matrix with homogeneous element dispersion was formed. • Surface area, chemisorbed active oxygen and Co2+/Co3+ ratio determined activity. [ABSTRACT FROM AUTHOR]

Pt/TiO 2 catalysts with various Pt loadings (0.1–0.7 wt.%) were synthesized by a combined wet impregnation and H 2 -reduction method. The as-prepared catalysts were firstly reported being applied in thermal catalytic decomposition of hydrogen peroxide (H 2 O 2 ) vapor for treating NO X . Physico-chemical properties of Pt/TiO 2 catalysts were investigated by comprehensive techniques, including XRD, Raman, N 2 adsorption–desorption, TEM, UV–vis DRS, XPS and PL spectroscopy. The activity tests showed that the incorporation of platinum into TiO 2 led to a significant increase in the catalytic oxidation of NO compared with the unmodified TiO 2 . Toward NO oxidation from H 2 O 2 vapor (molar ratio = 12/1), 0.3 wt.% Pt-TiO 2 exhibited a remarkable activity in NO X removal (96.7%) and a high selectivity (89.2%) in their conversion to nitrate species under the optimal condition. XRD and TEM results show that ultrafine Pt particles were well dispersed on the surface of anatase-phase TiO 2 . XPS analysis indicated that Pt dopant existed as mainly metallic Pt (0) and a small portion of Pt 2+ in as-prepared materials. The results of PL spectra demonstrated that the platinum nanoparticles on the TiO 2 surface significantly accelerated electron transfer and served as active sites for the adsorption and activation of H 2 O 2 molecules, to facilitate the generation of hydroxyl groups. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effect of Mn doping size over Al 2 O 3 on NO oxidation activity were elucidated. • Mn SACs/Cs -Al 2 O 3 exhibits a superior NO-NO 2 capacity compared with Mn NPs -Al 2 O 3. • The coordination environment of Mn species significantly affects the mobility of O sur. • Reducing Mn size from NPs to SACs/Cs promotes labile nitrate species formation. The exploitation of transitional metal catalysts for high-efficient conversion of NO to NO 2 still persists as an imperative issue due to the high cost of currently used Pt–based catalysts. Herein, we report a TEA-modification strategy to anchor Mn single atoms/clusters on Al 2 O 3 (Mn/Al 2 O 3 -T) for NO oxidation. Activity tests show that Mn/Al 2 O 3 -T (T 83 = 275 °C) displays a superior NO-to-NO 2 capacity compared with the unmodified Mn nanoparticle on Al 2 O 3 (Mn/Al 2 O 3 -B, T 66 = 300 °C) and Pt/Al 2 O 3 (T 43 = 350 °C) counterparts. Comprehensive characterization and DFT calculations discover that the effective adjustment of TEA can promote the generation of coordination unsaturated Mn sites with elongated Mn-O bonds, which can improve the mobility of surface lattice oxygen and facilitate the activation of molecular oxygen. Additionally, reducing Mn size from nanoparticles to single atoms/clusters favors the formation of labile nitrate species and facile desorption of NO 2 , thereby regenerating active sites and accelerating overall NO oxidation reaction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mn-decorated ZIF-67 derived catalyst is synthesized by MOF-template method. • The interface interaction enhances the mineralization rate of the catalyst. • MnCoO x -M existed the best catalytic activity, stability, and water resistance. • The introduction of H 2 O obviously inhibited the generation of organic by-products. Herein, a Mn cations highly dispersed and bimetallic interfacial interaction strengthen catalyst, MnCoO x , via combinations of MOF-templated method, Mn cation doping has been constructed for the chlorobenzene (CB) oxidation. As a result, MnCoO x -M possessed the best chlorobenzene degradation capacity and stability than those of similar bimetallic compounds prepared by co-precipitation method and single-phase oxide. Notably, this superior catalyst obtained a high mineralization efficiency with inhibition effect of the CO generation. The excellent performance of MnCoO x -M can be conducted to the good dispersion of the metal cations as well as a stronger Mn-Co interaction, which are further induced the excellent redox properties of the catalyst. Besides, the humidity tolerance experiments showed that a certain H 2 O participation can significantly inhibit the generation of some types of organic by-products, especially chlorinated organic compounds. Mechanistic studies showed that chlorobenzene dissociated on the surface of MnCoO x -M to form benzoquinone, phenolates, maleates, etc., which were finally oxidized to inorganic products. [ABSTRACT FROM AUTHOR]

Reactivity loss by intermediates aggregation and water vapor inhibition are two major and longstanding challenges for the noble-metal-based catalysts in oxygenated volatile organic compounds (OVOCs) oxidation. Herein, the core-shell Pd@CoO Janus sites are creatively designed and stabilized over the HSAPO-34 support. Quasi in situ XPS spectra reveal that the strong interactions in Pd@CoO Janus sites promote the charge redistribution and electron back-donation through Pd-O-Co coordination. Therefore, abundant positively charged Pd2+ sites are formed and oxygen species transformation is facilitated, which significantly promote the low-temperature efficiency of acetone oxidation. Furthermore, the Pd@CoO/HSAPO-34 catalyst facilitates H 2 O molecules dissociation and produce reactive OH Ter and OH Tri species, which considerably promotes the rapid decomposition of aldehyde intermediate via attacked CH 2 O* group, ensuring low-temperature oxidation of acetone. This work provides valuable guidance to develop specific catalysts with functional active sites for rationally utilizing H 2 O molecules to improve low-temperature performance and modulate reaction pathways during OVOCs oxidation. [Display omitted] • Thermal-depolymerization was employed to synthesize the Pd@CoO Janus sites. • Charge redistribution through Pd-O-Co coordination facilitates reactant activation. • Positively charged Pd2+ and activated Co-O coordination promote acetone oxidation. • Pd@CoO/HSAPO-34 catalyst facilitates the dissociation of H 2 O molecules. • Surface OH Tri and OH Ter groups accelerate aldehyde intermediate degradation. [ABSTRACT FROM AUTHOR]

[Display omitted] • K/MnO 2 prepared by hydrothermal impregnation method shows superior performance. • MnO 6 -K-MnO 6 bridging bond leads to the uniform energy of Mn-O bonds. • High electron density of K promotes the activation of oxygen molecules. • Excellent reducibility and abundant Brønsted acid sites promote toluene mineralization. • Effect of K doping position on oxygen vacancy and adsorption energy was proposed. Alkali metal potassium is conducive to structure promotion and electronic modulation in metal oxides. Here, K species was successfully introduced into α-MnO 2 via in situ synthesis (Pre-K/MnO 2) and hydrothermal impregnation method (Post-K/MnO 2) with target to boost the low-temperature reactivity and deep destruction efficiency for toluene oxidation. Results reveal that Post-K/MnO 2 possesses the highest catalytic activity with toluene (1000 ppm) totally mineralized at just 258 °C, achieving over 70 °C of temperature reduction than that of Pre-K/MnO 2. K specie shows obvious charge transfer balance ability in MnO 2 , forming MnO 6 -K-MnO 6 bridging bond and leading to more uniform energy of Mn-O bonds. High electron density of K+ can promote the activation of oxygen molecules, resulting in a better catalytic performance of toluene. Abundant Brønsted acid sites are beneficial for toluene adsorption and regeneration of hydroxyl on the surface, which promote the degradation of intermediates during toluene oxidation. Moreover, Post-K/MnO 2 shows satisfied catalytic performance under different space velocities and initial concentrations and humid condition. Density functional theory (DFT) calculation revealed the situation of oxygen vacancy and toluene/oxygen adsorption energy in catalysts with different K doping locations. Results showed that the adsorption energy is stronger when K located in large tunnel (0.46 × 0.46 nm), and it is easier to form oxygen vacancy while K entered the small tunnel (0.33 × 0.33 nm). The present work paves new insights into the designing of efficient transition metal oxide catalyst for VOC deep purification. [ABSTRACT FROM AUTHOR]

[Display omitted] • K-doped ɑ-MnO 2 were synthesized by a reproducible post processing process. • Oxygen vacancies can be modulated by varying K+ incorporation amount. • 4-K/MnO 2 has the highest activity due to abundant surface absorbed oxygen (O ads). • O ads plays an important role in toluene dehydrogenation and benzoate formation. Oxygen vacancy plays an important role in adsorption and activation of oxygen species and therefore promotes the catalytic performance of materials in heterogeneous oxidation reactions. Here, a series of K-doped ɑ-MnO 2 materials with different K loadings were synthesized by a reproducible post processing process. Results show that the presence of K+ enhances the reducibility and oxygen vacancy concentration of ɑ-MnO 2 due to the break of charge balance and the formation of low valence Mn species. 4-K/MnO 2 material exhibits the highest toluene oxidation activity and satisfied long-term stability and water resistance owing to its superior reducibility and abundant surface absorbed oxygen (O ads). In situ DRIFTS demonstrate that O ads greatly accelerates toluene dehydrogenation rate and promotes benzoate formation, enhancing the activation and decomposition of toluene molecules. Moreover, the C C cleavage of benzene ring (forming maleic anhydride) is the rate-determining step of toluene oxidation, which can be easily occurred over 4-K/MnO 2. [ABSTRACT FROM AUTHOR]

[Display omitted] Fabricating of economical transitional metal oxide-based materials with satisfied low-temperature catalytic performance and application perspective is still a challenge in deep degradation of VOCs. Here, Mn-Cu bimetallic oxides were facilely prepared by one-step hydrothermal-redox method, which displayed much higher catalytic activity in toluene oxidation than those synthesized by hydrolysis-driven redox-precipitation or co-precipitation approach. It is shown that the lattice defect and oxygen vacancy concentration over prepared materials can be tuned by controlling Cu/Mn molar ratio. Amongst, spinel structured MnCu 0.5 exhibited the highest catalytic activity, superior durability and water resistance in toluene total oxidation owing to abundant surface adsorbed oxygen species, excellent low-temperature reducibility, and high amounts of Cu+ and Mn3+. In detail, the reaction rate of MnCu 0.5 was over 9.0 times higher than that of MnCu 0.75 , MnCu 0.75 -P and MnCu 0.75 -H 2 O 2 at relative low temperature of 210 °C. The cyclic redox process with easier oxygen species mobility played a key role in the catalytic oxidation of toluene. Typical reaction intermediates as benzyl alcohol, benzaldehyde, benzene, phenol, and benzoquinone could be detected by PTR-MS, which further decomposed to acetone, ethanol, ketone, acetic acid, methanol, formaldehyde and acetaldehyde species by ring opening before total mineralization. [ABSTRACT FROM AUTHOR]

• Rod-, sheet-, and cube-like Co 3 O 4 with different exposing crystal facets were synthesized. • Rod-like Co 3 O 4 with (110) facet exhibits the highest catalytic activity in propane oxidation. • Co 3 O 4 with exposed (110) facet has more lattice defects and low coordination Co atoms. • (110) facet of Co 3 O 4 has the lowest formation energy of oxygen vacancy. • Lewis acid-base pairs and surface oxygen vacancy promote oxygen and propane activation. Low-temperature degradation of short chain alkane is one of the greatest challenges of volatile organic compound purification. Here, rod-, sheet-, and cube-like Co 3 O 4 (Co 3 O 4 -R, Co 3 O 4 -S, and Co 3 O 4 -C) with predominantly exposed (110), (111), and (100) facets respectively were fabricated. Co 3 O 4 -R presents excellent activity achieving 90 % of propane oxidized at just 195 °C owing to large amounts of lattice defects, oxygen vacancies and low coordinated Co atoms. Theoretical calculation reveals that Co 3 O 4 -R has the lowest formation energy of oxygen vacancy on (110) facet (E vo (110) =1.7 eV), which has a higher activation capacity for oxygen due to the largest O 2 adsorption energy (−1.30 eV) and thus accelerates propane oxidation. Moreover, largest amount of lewis acid-base pairs existed in Co 3 O 4 -R polarizes substrate electron distribution and therefore accelerates the activation of C–H bonds. Electrophilic oxygen species (O 2 2− or O−) caused the degradation of carbon skeleton and formed carboxylate intermediates before mineralized to CO 2. [ABSTRACT FROM AUTHOR]

The development of highly active and SO 2 -resistant catalysts is a major hurdle in the catalytic oxidation of NO to NO 2. Herein, we fabricate a core–shell Mn 2 O 3 @CeO 2 catalyst using a two-step method for NO oxidation. Benefiting from the generation of abundant Mn4+−O v −Ce3+ interfacial sites and plentiful oxygen vacancies, the resulting Mn 2 O 3 @CeO 2 exhibits a superior low-temperature NO-to-NO 2 capacity (T 50 at 183 °C and T 86 at 275 °C), obtaining a remarkable temperature reduction compared to commercial Pt/γ-Al 2 O 3 catalyst (T 50 at 262 °C). Meanwhile, In-situ Raman and In-situ Drifts reveal that Mn4+−O v −Ce3+ interfacial site is the main adsorption site for the formation of N-containing intermediates, which plays a decisive role in the NO oxidation reaction. More encouragingly, SO 2 shows a much higher affinity for CeO 2 sheath (E CeO 2 , SO 2 = –3.48 eV) than Mn 2 O 3 core (E Mn 2 O 3 , SO 2 = –0.87 eV), thus avoiding its toxic effects on the interior active sites and endowing Mn 2 O 3 @CeO 2 a superior SO 2 -resistance. [Display omitted] • A two-step hydrothermal approach was adopted to fabricate Mn 2 O 3 @CeO 2 for NO oxidation. • Abundant Mn4+−O v −Ce3+ sites form at manganese−cerium interfacial perimeter. • Mn4+−O v −Ce3+ interfacial sites of Mn 2 O 3 @CeO 2 boost the low-temperature activity. • The CeO 2 sheath improves SO 2 -resistant ability of Mn 2 O 3 @CeO 2. [ABSTRACT FROM AUTHOR]

[Display omitted] • Spinel-type high-entropy (CoCrFeMnNi) 3 O 4 oxides were synthesized. • Role of precipitant in activation of OOH− groups and reactive oxygen was revealed. • (CoCrFeMnNi) 3 O 4 has superior activity and hydrothermal stability in propane oxidation. • OOH− and O 2 − are the key species in catalytic oxidation of propane. Efficient catalytic destruction of light alkane with ultra-stable and highly symmetric structure is still an intractable issue. High entropy oxides (HEOs) with high chemical disorder and lattice distortion and superior stability have shown great potential in heterogeneous thermocatalysis. Herein, spinel-type HEOs are synthesized via a scalable co-precipitation method with different precipitants (NaOH, Na 2 CO 3 , and NaHCO 3) and firstly adopted in catalytic destruction of propane. Results demonstrate that the HEO-NaOH possesses the best activity, achieving 90% of propane conversion at 325 °C with an apparent activation energy of 56 kJ mol−1. Compared with other two HEOs, the HEO-NaOH has larger quantities of surface oxygen vacancies and easily forms several reactive oxygen species (OOH−, O 2 −, and OH−, etc.), which significantly contribute to improve the catalytic performance. Moreover, the excellent water resistance of HEOs is verified due to their high conformational entropy and structural stability. Reaction mechanism reveals that OOH− and O 2 − are the key species in the oxidation of C 3 H 8 , which break C-H and C-C bonds in sequence, and are then converted to oxygenated compounds via oxygen oxidation before the final mineralization. The present work provides new insights into the fabrication of efficient catalysts for light alkane destruction as well as other thermocatalytic applications. [ABSTRACT FROM AUTHOR]

• Hierarchical Al 2 O 3 -pm and ZnO-pm microspheres are prepared by a hydrothermal method. • Pd/Al 2 O 3 -pm and Pd/ZnO-pm show excellent EA oxidation activity and CO 2 yield. • Pd dispersion is enhanced by high surface area and developed porosity of supports. • Mechanisms of EA oxidation over Pd/Al 2 O 3 -pm and Pd/ZnO-pm were elucidated. • Pd availability is obviously enhanced by using Al 2 O 3 -pm and ZnO-pm coatings. Developing economical and active materials is of great significance for VOC purification. Here, hierarchical porous Al 2 O 3 and ZnO microspheres (Al 2 O 3 -pm and ZnO-pm) were synthesized by a facile hydrothermal strategy. The urchin-like Al 2 O 3 -pm and flower-like ZnO-pm possess high specific surface area (especially; external surface area) obviously boost the dispersion of Pd with 29.3 % and 30.1 % over Pd/Al 2 O 3 -pm and Pd/ZnO-pm, respectively, over 3.4 times higher than those of commercial Al 2 O 3 - and ZnO-supported counterparts. Pd/Al 2 O 3 -pm possesses excellent activity and CO 2 yield in ethyl acetate (EA) degradation, with TOF reaches 7.76 × 10−3 s−1 at 160 °C under GHSV of 50,000 h-1. Moreover, Pd/Al 2 O 3 -pm exhibits satisfied performance in EA-contained binary VOCs oxidation and has high long-term stability under both dry and humid conditions. Both Pd sites and Brønsted acid sites participated in reaction process and initially react with EA to form ethylene and ethanol, respectively. Larger amount Brønsted acid sites over Pd/Al 2 O 3 -pm promote ethanol formation and C-C cleavage, resulting in different CO 2 yields and EA activation mechanisms. The coating greatly enhances Pd dispersion over Pd supported monolithic catalyst, endowing its desired activity and stability even with a much lower Pd loading. This work promotes the potential application of noble-metal-based monolithic materials in VOC degradation. [ABSTRACT FROM AUTHOR]

• Spherical-like Pd-based catalysts were rationally prepared by different protocols. • High Pd dispersion favors the catalytic activity in n -butylamine combustion. • High porosity of catalysts is beneficial for NO x formation control. • Pd/S-2 IS prepared by in situ synthesis method shows the best catalytic performance. • The n -butylamine destruction mechanism was proposed by in situ DRIFTS. Two types spherical-like SiO 2 with different specific surface area (SSA) and porosity were synthesized and used as support for Pd catalysts, which were prepared by various protocols (in situ synthesis (IS, Pd/S-1 IS , and Pd/S-2 IS), wet impregnation (WI, Pd/S-1 WI , and Pd/S-2 WI), and grafting (GA, Pd/S-1 GA , and Pd/S-2 GA)) and adopted in n -butylamine combustion. Results suggest that Pd dispersion is positive correlation with support SSA and GA method is the most favorable approach to obtain highly dispersed Pd active sites. Pd/S-1 IS , Pd/S-1 WI , and Pd/S-1 GA catalysts with small SSA show inferior activity and higher NO x yield than those of Pd/S-2 IS , Pd/S-2 WI , and Pd/S-2 GA with large SSA, irrelevant with the preparation methods. Amongst, Pd/S-2 GA possesses the smallest Pd average diameter (ca. 1.72 nm) and highest activity with 90% of n -butylamine destructed at 234 °C; however, the yield of NO x over Pd/S-2 GA is much higher than the other catalysts (except Pd/S-1 GA) as the GA approach provides high concentration of active sites and the preparation procedure sacrifices the SSA and porosity of supports to some extent. In situ DRIFTS results reveal that the developed porosity of catalyst promotes nitrogen-containing by-products (NH x) transfer and diffusion and avoids their further oxidizing to NO x. The activity of samples prepared by the WI process is lower than that prepared by the IS or GA method due to limited active sites. Comparatively, the Pd/S-2 IS prepared by the IS method has relative high activity (T 90 of 240 °C) and low NO x yield (0.99% at T 90) in n -butylamine oxidation among all materials, exhibiting an attractive prospective in nitrogen-containing VOC environment-friendly elimination. [ABSTRACT FROM AUTHOR]

The efficient catalytic oxidation of nitrogen-containing volatile organic compounds remains a big challenge due to unmanaged production of harmful byproducts. Herein, a series of Cu-Mn modified hierarchical SAPO-34 zeolite catalysts with different pore structures were synthesized for n-butylamine oxidation. The physicochemical properties and catalytic performance of catalysts were investigated and analyzed in detail. Among them, CuMn/S-1 shows the highest activity (T 90 = 279 °C, GHSV = 12,000 h−1), which is attributed to its higher porosity, higher surface acidity and superior reducibility. Meanwhile, it is found that the hierarchical structure and mesopore play an important role in improvement of N 2 selectivity. Meanwhile, CuMn/S-1 also exhibits high stability and water resistance. The catalytic mechanism of n-butylamine on CuMn/SAPO-34 was investigated by in situ DRIFTS, showing that propanol, methanol and acetate are the main intermediates. [Display omitted] • A series of Cu-Mn modified hierarchical SAPO-34 zeolite catalysts were prepared. • CuMn/S-1 shows the excellent n-butylamine oxidation activity and high N 2 selectivity. • Acidity and reducibility are the key factors determining catalytic activity in low/high temperature, respectively. • The hierarchical structure and acidity have effects on N 2 selectivity. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • CrO x /LaSrMnCoO 6 (Cr/LSMC) composite catalysts were rationally designed. • Obvious synergistic effect between CrO x and LSMC can be observed. • 10 wt.% Cr/LSMC has excellent catalytic stability and H 2 O resistance. • By-products distribution during 1,2-dichloroethane oxidation was studied. Abstract 1,2-dichloroethane (1,2-DCE) is a representative industrial chlorinated volatile organic compound (CVOC) making great hazardous to the environment and human health. In this work, LaSrMnCoO 6 (LSMC) double perovskite-type materials with high thermal stability and coke resistance in 1,2-DCE oxidation were prepared by a facile sol-gel method. Based on this, a series of CrO x /LaSrMnCoO 6 catalysts (Cr/LSMC, CrO x loading = 5 to 20 wt.%) which combine the merits of CrO x (high activity and chlorine tolerance) and LaSrMnCoO 6 were synthesized and adopted in deep oxidation of 1,2-DCE for the first time. As expected, obvious synergistic effects between CrO x and LSMC on 1,2-DCE destruction were observed. Amongst, 10 wt.% CrO x /LaSrMnCoO 6 (10Cr/LSMC) shows the best catalytic activity with 90% of 1,2-DCE destructed at 400 °C. Furthermore, the outstanding catalytic durability and water resistance of 10Cr/LSMC in 1,2-DCE oxidation were also demonstrated. In addition to this, the reaction pathway of 1,2-DCE decomposition over Cr/LSMC materials was discussed based on the results of online product analysis. We found that the enhanced catalytic performance of Cr/LSMC materials can be reasonably attributed to their high reducibility, excellent 1,2-DCE adsorption capability, and large amounts of surface active lattice oxygen species. It can be anticipated that the Cr/LSMC catalysts are promising materials for CVOC elimination and the results from this work could also provide some new insights into the design of catalysts for CVOC efficient destruction. [ABSTRACT FROM AUTHOR]

[Display omitted] • OV s concentrated La x Sr 1-x MnO 3±δ catalysts were prepared by NaBH 4 reaction method. • Sr segregation was significantly occurred during NaBH 4 treatment and created OVs. • A treated La 0.5 Sr 0.5 MnO 3±δ showed high performance and durability in CB degradation. • Abundant active oxygen species and mobility improved oxidation of CB. • Reaction mechanism and OV s annihilation were proposed over prepared catalyst. Surficial lattice oxygen in perovskite compounds is a common participant during chloroaromatic catalytic degradation. Herein, we proposed a facile oxygen vacancy construction strategy for preparing high active La x Sr 1-x MnO 3±δ (LSMO) via NaBH 4 treatment. Results reveal that LSMO composites are not only reduced by NaBH 4 under mild condition, but also triggering a significant Sr segregation effect, which plays a key role in oxygen vacancy formation accounting to the electron donation from Sr to Mn acceptor and subsequent lattice oxygen activation. Moreover, the concentration of interfacial active oxygen species can be regulated by taming the La-Sr interaction with different Sr substitution proportions. The anchored oxygen vacancies (OVs) take advantage of electron capture or transfer and induce molecule oxygen into active oxygen species to react with chlorobenzene molecules, resulting in a preferential catalytic oxidation capacity. Amongst, reduced La 0.5 Sr 0.5 MnO 3±δ catalyst displays superior chlorobenzene destruction efficiency with 90% of which converted as low as 236 °C, which also exhibits a stable performance in long-time operation. However, the OVs would be refilled by H 2 O molecules and results in a weaker water resistance for OVs anchored catalyst. In summary, the annihilation of OVs is the most important factor for catalyst deactivation. The research offers a new avenue to construct interfacial oxygen species in perovskite oxides during the chlorobenzene deep oxidation process. [ABSTRACT FROM AUTHOR]

A series of hollow MnOx-CeO 2 mixed oxide catalysts were prepared by employing carbon as hard templates. The activity tests reveal that the catalytic performance of MnOx-CeO 2 (CS) samples are more active than that of MnOx-CeO 2 (AC) sample, indicating carbon sphere (CS) as a more effective carbon template. Among these samples, MnOx-CeO 2 (CS1) sample exhibits the best activity, for which a maximal NO conversion (∼82%) could be attained at 220 °C when GHSV = 120,000 h −1 . In addition, the NO conversion could be further improved with lower NO initial concentration or higher O 2 content. Under the simulated flue gas condition, the activity of MnOx-CeO 2 (CS1) sample is barely affected by the presence of CO 2 , but the influence of H 2 O and SO 2 couldn’t be neglected. The characterization result proves that the core-shell hollow structure has been successfully synthesized over MnOx-CeO 2 binary oxides. For the hollow MnOx-CeO 2 sample, the mesopore structures are formed and the MnOx oxides are highly dispersed on CeO 2 support. Among these samples, MnOx-CeO 2 (CS1) sample possesses the largest S BET and V total values. The result of H 2 -TPR and oxygen pulse measurement indicates that MnOx-CeO 2 (CS) samples, especially MnOx-CeO 2 (CS1) exhibits the best redox property. Moreover, more amount of high valence Mn as redox active sites and more oxygen vacancies exist in MnOx-CeO 2 (CS1) proved by XPS technique. Overall, these properties may contribute to the excellent activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • A series of transition metal cordierite-based monolithic catalysts were prepared. • Mn/Al 2 O 3 /COR shows excellent ethyl acetate (EA) oxidation activity and water resistance. • Surface oxygen species (O β) play vital roles in EA activation and intermediate generation. • Low content water vapor (≤1 vol%) promotes EA activation and ethanol formation. • Water vapor leads to the decline of O β and formation of large-size hard coke. The reduction and control of VOCs from anthropogenic sources becomes a research hotspot due to their tremendous environment hazards. Fabricating efficient and applicable noble-metal-free monolithic catalysts is still a great challenge for industrial VOC economical removal. In this work, cordierite-based honeycomb monolithic catalysts (M/Al 2 O 3 /COR; M = Cr, Mn, Fe, Co, Ni and Cu) were synthesized by a versatile and scalable wash-coating method and adopted for ethyl acetate (EA) catalytic oxidation. Mn/Al 2 O 3 /COR possesses remarkable activity with 90% of ethyl acetate (EA) oxidized at 236 °C owing to abundant surface active oxygen species. Moreover, excellent stability and water resistance of Mn/Al 2 O 3 /COR were observed during long-term successive reaction. In situ DRIFTS results reveal that the decomposition of EA to ethanol is the main pathway under humid conditions, and the presence of low content water vapor (≤1 vol%) promotes EA conversion ascribed to the presence of abundant OH derived from H 2 O dissociation; however, further increasing of water concentration inhibits EA conversion. The adsorption of OH over oxygen vacancies inhibits the generation of surface oxygen species and blocks further oxidation of intermediates to form acetate, leading to the reduction of CO 2 yield and formation of coke aggregates. This work will provide instructive and feasible references for designing of VOC oxidation catalysts under practical reaction conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Birnessite-type short rod-like MnO 2 (MnO 2 -SR) was prepared under ambient conditions. • MnO 2 -SR exhibits the highest activity with 90% of propane oxidized at 225 °C. • Oxygen vacancies and high valent Mn4+ species promote activating of O 2 and propane. • Dissociation of propane molecules is the decisive step in propane oxidation. Developing economical and robust noble metal-free materials for obstinate light alkane low-temperature decomposition is of great significance. Here, birnessite-type short rod-like MnO 2 was firstly prepared by facile mixing KMnO 4 and ascorbic acid under ambient conditions and employed in propane catalytic decomposition. Experimental results revealed that abundant oxygen vacancies and high valent Mn4+ species, superior reducibility, and high surface oxygen mobility guarantee the remarkable low-temperature activity of MnO 2 -SR, over which 90% of propane can be oxidized (T 90) at temperature as low as 225 °C, achieving a temperature reduction over 70 °C compared with that of δ-MnO 2 (T 90 = 300 °C) and α-MnO 2 (T 90 = 355 °C). In situ diffuse reflectance infrared Fourier transform spectroscopy revealed that the dissociation and activation of propane molecules is the decisive step in propane oxidation. Gaseous propane is slowly oxidized by adsorbed oxygen directly to the final mineralization products at low temperature region (<200 °C); at high temperature region (>200 °C) however, propane molecules are firstly dissociated and activated before oxidized to carbonate intermediate products over active oxygen, and then eventually oxidized to carbon dioxide and water. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mn-Cu bimetallic catalysts were facilely prepared by one-step hydrothermal-redox method. • Hydrothermal-redox was superior to other preparation methods for Mn-Cu catalysts. • MnCu spinel type catalyst exhibited excellent low-temperature catalytic performance. • PTR-MS results revealed the reaction routes of toluene oxidation over MnCu catalyst. Developing facile preparation method to obtain the satisfied low-temperature catalytic performance of transitional metal oxide-based materials is still a challenge in deep degradation of VOCs. Here, a series of Mn-Cu bimetallic oxide catalysts were prepared by one-step hydrothermal-redox method for catalytic total oxidation of toluene. The CH 3 COOH concentration, Cu/Mn molar ratio and calcination temperature greatly affected the crystal structure, micromorphology and catalytic performance. Amongst, MnCu spinel structured catalyst exhibited excellent low-temperature catalytic activity, superior durability and water resistance in toluene total oxidation owing to its abundant surface adsorbed oxygen species, higher amount of Cu+ and Mn3+ and excellent low-temperature reducibility. The reaction rate of MnCu was 7.0 times higher than that of MnCu 0.5 at 210 °C. The cyclic redox process with enough oxygen vacancy played a vital role in toluene oxidation. The deep oxidation of benzene was the key step in the toluene oxidation. Proton transfer reaction-mass spectrometry (PTR-MS) results revealed the reaction intermediates including benzaldehyde, benzene and phenol, which further decomposed to acetone, ethanol, acetic acid, ketone and acetaldehyde by ring opening before total mineralization. Therefore, PTR-MS provided a facile method to investigate the reaction mechanism of toluene oxidation. [ABSTRACT FROM AUTHOR]

• Cl-VOC catalytic degradation focuses on regulation of acidity and reducibility. • HCl, CO 2 , and H 2 O are expected final products that represents compete degradation. • All species and formation routes of byproducts in Cl-VOC degradation are collected. • Improving further oxidation and preventing chlorination are two strategies. In catalytic oxidation of Cl-VOCs, H 2 O, CO 2 , and HCl are anticipated final products, while Cl 2 with strong oxidability, CO and organics without complete mineralization are considered as byproducts. The particularity of Cl substitution in Cl-VOCs further brings higher possibility in byproducts formation with higher toxicity. Furthermore, polychlorinated byproducts as predominant precursors for PCDDs and PCDFs are commonly detected, which becomes the biggest potential risk. This review systematically summarizes multiple byproducts distribution in effluent gas and surficial accumulated compounds. The migration pathways of Cl species during catalytic oxidation include HCl desorption assisted by Brønsted acidic sites, Cl 2 formation via Deacon reaction, chlorination into organic byproducts, and deposition on catalyst surface. Various strategies for inhibiting byproducts formation are explored based on the critical factors for byproducts formation with target to provide guidance to the development of catalysts for Cl-VOC efficient and complete elimination. Rapid transformation of intermediates without participating chlorination process is the crucial strategy. Improving further oxidation with rational redox property and preventing chlorination with suitable acidity and specific structures are two directions for inhibit byproducts formation. However, it is still challenging to reveal the migration and evolution routes of Cl species and rational design of catalysts to achieve actually complete elimination of Cl-VOCs with no secondary pollution. [ABSTRACT FROM AUTHOR]