Toluene Conversion Research Articles

Direct amination of toluene with hydroxylamine to produce toluidine over vanadium catalysts

In this study, metallic vanadium was used as catalysts for direct amination of toluene with hydroxylamine to produce toluidine under mild conditions. High toluene conversion and toluidine selectivity were obtained, corresponding to 87.62% and 96.45% respectively. Additionally, thermodynamic and kinetic calculations were carried out. It was concluded that the reaction was dominated by kinetics, with the distribution of three products being para > ortho > meta. The computational and experimental results indicated that the amination process involves an amino radical mechanism.

Highly Stable MOFs-Derived Cu–Co Composite Metal Oxides for Catalytic Oxidation of Toluene

CuCoOx was prepared by in situ pyrolysis of Cu2+ partially substituted MOF-74 precursor with Co-MOF as a template for catalytic oxidation of toluene. T90 (the temperature corresponding conversion of 90%) was only 212°C, at 1000 ppm toluene and weight hourly space velocity (WHSV) of 36 000 mL g–1 h–1. In addition, the conversion was maintained above 97% for 74 h of continuous reaction at 260°C. Even if after 2400 ppm 1,2-dichloroethane (1,2-DCE) poisoning for 2 h, the toluene conversion was still up to 93%, demonstrating excellent stability and resistance to deactivation of catalyst. Furthermore, The high activity and stability of CuCoOx could be attributed to the large specific surface area as well as the high Co2+/Co3+, Cu2+/Cu+, and Olatt/Oads molar ratios.

Synergistic catalytic degradation of benzene and toluene on spinel MMn2O4 (M[dbnd]Co, Ni, Cu) catalysts

Owing to the complexity of multicomponent gases, developing multifunctional catalysts for synergistic removal of benzene and toluene remains challenging. The spinel MMn2O4 (MCo, Ni, or Cu) catalysts were successfully synthesized via the sol–gel method and tested for their catalytic performance for simultaneous degradation of benzene and toluene. The CuMn2O4 sample exhibited the best catalytic performance, the conversion of benzene reached 100 % at 350 °C, and toluene conversion reached 100 % at 250 °C. XRD, N2 adsorption-desorption, HRTEM-EDS, ED-XRF, Raman spectroscopy, H2-TPR, NH3-TPD, O2-TPD and XPS were used to characterize the physical and chemical properties of MMn2O4 catalysts. The excellent redox properties, high concentration of surface Mn4+, and adsorption of oxygen species over the CuMn2O4 sample facilitated the simultaneous and efficient removal of benzene and toluene. Additionally, in situ DRIFTS illustrated the intermediate species and reaction mechanism for the synergetic catalytic oxidation of benzene and toluene. Notably, as an effective catalytic material, spinel oxide exhibited excellent synergistic degradation performance for benzene and toluene, providing some insight for the development of efficient multicomponent VOC catalysts.

CeCoaOx catalysts derived from metal-organic frameworks for enhancing catalytic toluene oxidation by tuning surface oxygen property

Rod-shaped CeCoaOx catalysts with varying Co doping ratios (a = 0.012, 0.017, 0.022) were synthesized by calcinating the Ce-MOF, prepared using a water bath and trimesic acid as an organic ligand. This method ensured a high degree of elemental mixing, abundant pore channels and a large specific surface area are all beneficial for enhancing toluene catalytic oxidation activity. Raman, XPS, and catalytic activity tests confirmed strong interactions between the Ce and Co oxides, promoting the formation of more Ce3+ and oxygen vacancies. Among these catalysts, CeCo0.012Ox exhibited superior catalytic performance for toluene oxidation under weight hourly space velocity of 40,000 mL·g−1·h−1. The temperature at toluene conversion of 10 %, 50 % and 90 % was 140, 205 and 226 °C, respectively, which was 61, 12 and 14 °C higher than those over pure phase CeO2. CeCo0.012Ox also demonstrated excellent activity stability under high humidity (10 vol%H2O). H2-TPR, O2-TPD and in situ DRIFTS also revealed that surface-absorbed oxygen species played a crucial role in catalytic activity, with CeCo0.012Ox benefiting from abundant oxygen vacancies and effective oxygen species mobility.

Preparation of Nanosized Copper–Manganese Composite Oxides and Their Catalytic Performance in the Oxidation of Toluene

Nanosized Cu–Mn composite oxide catalysts were prepared from potassium permanganate, copper nitrate, n-butanol, and cetyltrimethylammonium bromide as a manganese source, copper source, reducing agent, and surfactant, respectively. The Cu[Formula: see text]–Mn sample possessed a small particle size (10–40[Formula: see text]nm) and a relatively high specific surface area ([Formula: see text]); its main components were Cu[Formula: see text]Mn[Formula: see text]O4 and Mn3O4. As a consequence, the Cu[Formula: see text]–Mn catalyst exhibited good catalytic activity in the oxidation of toluene. At a toluene concentration of 1000[Formula: see text]ppm and a space velocity of [Formula: see text], the [Formula: see text] and [Formula: see text] of the Cu[Formula: see text]–Mn catalyst toward toluene were 239[Formula: see text]C and 250[Formula: see text]C, respectively. Furthermore, even after 30[Formula: see text]h of operation at 275[Formula: see text]C, the conversion of toluene was 99% (at the space velocity of [Formula: see text]).

Two-dimensional model in a laminar flow slit photoreactor for the determination of surface kinetic constants considering the presence of diffusion limitations

Narrow slit reactors are widely used in laboratory testing of photocatalytic materials, as well as for the determination of kinetic coefficients in surface photocatalyzed reactions. In this work, the behavior of a continuous laminar flow slit reactor was described by a two-dimensional model, addressing the advection–diffusion problem in the fluid phase, coupled with a first-order chemical reaction on the reactor walls. The concentration profile of the reactant, in the transverse and longitudinal directions of the reactor, depends on two parameters that characterize the system; the Péclet number and the Damköhler number, in addition to the geometry of the reactor. Once a short distance from the reactor’s entrance has been surpassed, the relationship between the transversally averaged reactant concentration and the concentration existing on the catalytic surface becomes essentially constant, thus defining an (external) effectiveness factor. The simulations carried out for a wide range of values of the parameters characterizing the model showed that the effectiveness factor only depends on the Damköhler number, being independent of the value of the Péclet number and of the relationship between the reactor length and the distance separating the plates. An analytical expression for the effectiveness factor as a function of the Damköhler number was proposed, which allows to determine the value of the kinetic coefficient for the surface reaction (ks), even in the presence of important limitations to mass transfer. The methodology proposed was illustrated performing experiments of photocatalytic oxidation of toluene in air (with Péclet numbers ranging from 20 to 40), employing a paint formulated with carbon-doped TiO2 in a continuous laboratory photoreactor of flat parallel plates. The observed toluene conversions were in the range of 13 to 26 %, consequently, the calculated Damköhler number was Da = 0.0307 and the surface kinetic coefficient thus determined (for 50 % of relative humidity and 42.3 W/m2 of irradiance flux) was ks = 1.262 10-4 m/s. The significance of this work lies in the development of a comprehensive model that can be used to know the surface kinetics in photocatalytic reactions, applicable to scenarios where there are considerable mass transfer limitations or not.

Study of Pt-modified chromium-manganese oxide alloys to improve the performance of toluene abatement

This research is dedicated to solving the environmental problems of volatile organic compounds (VOCs), particularly aromatic chemicals in industrial emissions. The research aims to explore low-temperature, effective catalytic degradation technologies, specifically involving metal oxide and noble metal oxide catalysts, especially the Cr-Mn-Pt series catalysts. The Cr-Mn-Pt catalysts synthesized by the co-precipitation method showed efficient catalytic degradation of VOCs in low-temperature environments. The results of the experiment show that the Cr-Mn-Pt catalysts achieved 90 % toluene conversion at 198 °C, a 1000 ppm toluene concentration, and GHSV=15,000 mL/g·h, which is superior to single MnOx and Cr-Mn catalysts. The catalysts are characterized in depth using X-ray diffraction, specific surface area analysis and Fourier transform infrared spectroscopy. The result shows that the high specific surface area and large volume of pores of the Cr-Mn-Pt catalyst are advantageous for enhancing their catalytic activity and stability. The catalytic mechanism analysis shows that the degradation mechanism of toluene follows the Mars-van Krevelen mechanism with the final conversion of the intermediate product benzoate to CO2 and H2O. In summary, the Cr-Mn-Pt catalyst shows great potential in the technical treatment of VOCs due to their excellent low-temperature catalytic efficiency and stability, and it has enormous practical implications for protecting the environment in the industry.

Introducing attapulgite to prepare manganese-based monolithic catalyst for catalytic combustion of toluene

A series of attapulgite-loaded manganese oxides cordierite monolithic catalysts with different KMnO4/Mn(NO3)2 molar ratios (3:1, 1:1, and 1:3 for KMnO4/Mn(NO3)2, respectively) were prepared by a hydrothermal-ball mill impregnation method. According to the analysis of the characterization findings, the main active species of the catalyst was Mn4+ species. By incorporating acid-treated attapulgite (HATP) and adjusting the molar ratio of KMnO4/Mn(NO3)2, the content of Mn4+ and surface-adsorbed oxygen species on the catalyst surface increased, subsequently enhancing catalytic activity at low temperatures. Experimental results revealed that the Mn/HATP/cordierite catalyst with a KMnO4 to Mn(NO3)2 molar ratio of 3:1, Mn loading amount of 30 wt%, and active coating deposition of 250 g/L exhibited the highest catalytic activity, achieving a 90 % conversion of toluene at 298 °C (T90 = 298 °C, GHSV = 10000 h−1). These findings will provide valuable support for the design of highly efficient monolithic catalysts for toluene removal.

Surface oxygen vacancies induced by cu-doping in hexagonal ZnMn2O4 nanoplates for high efficiency photothermocatalytic oxidation of toluene

The exploitation of efficient and stable photothermal catalyst for the deep mineralization of volatile organic compounds (VOCs) is crucial and challenging. Herein, a photothermal catalyst with abundant oxygen defects was prepared for the first time via Cu-doped ZnMn2O4 hexagonal nanoplate. Experimental characterization results reveal that Cu doping enhances not only the ZnMn2O4 defect contents but also the light absorption and thermal conversion ability of ZnMn2O4. Compared to the undoped ZnMn2O4 (ZMO), the ZnMn2O4 with optimal Cu doping amount (ZMO-4Cu) exhibits excellent photothermal catalytic performance (94% toluene conversion and 87% toluene mineralization) and good resistance to low concentration SO2 under full-spectrum light irradiation. Experimental characterizations and theoretical calculations jointly demonstrated that the oxygen vacancies of ZMO-4Cu surface are more conducive to the adsorption of O2, effectively reduce the oxygen dissociation energy of ZMO-4Cu, thus generating abundant active oxygen species and improving the photothermal catalytic activity for toluene oxidation. In situ IR experiments disclosed that photothermal catalysis is more conducive to the toluene deep oxidation than thermal catalysis. This work provides new insights for the design of high efficiency photothermal catalysis for the deep oxidation of VOCs.

Facile synthesis of Ni-doped zeolite-based catalysts from waste coal gasification fine slag for steam reforming of toluene

The preparation of efficient and stable catalysts for biomass tar reforming using low-cost solid waste is of great value for achieving green biomass gasification. In this work, new porous Ni-doped zeolite catalysts were formed by an ion exchange method making use of the waste CGFS as the precursor. At a proper NiO loading content, the catalyst (Na@Air-0.2Ni) exhibits a uniform spherical particle-linked porous structure with NaAlSiO4 as the supporting matrix and NiO particles anchoring on the surface as active sites. The catalytic performance of the catalysts was investigated in toluene reforming experiments to evaluate their potential for biomass tar conversion. Under optimized conditions (720 °C, S/C = 1.5, and N2 flow 25 mL/min), toluene conversion reached 92 % using Na@Air-0.2Ni as a catalyst, yielding 2500 μmol/min CO and 2800 μmol/min H2. Continuous steam reforming of toluene formed to FeNi3 alloy, which in turn strengthens the stability of the catalyst, and a high toluene conversion of 81 % can be achieved in 450 min continuous experiment, indicating the excellent stability of the catalyst. This work has confirmed that coal gasification slag rich in silicon and aluminum has the potential to prepare new zeolite-based catalysts, which is an important exploration for promoting high-value conversion of solid waste.

One-Pot construction of highly active hetero-interface over porous non-stoichiometric perovskite with gel combustion strategy to enhance toluene purification activity

Constructing active perovskite nanostructures by a simple method is of great value and significance to the practical application of non-precious metal oxide-based catalysts. Herein, a surfactant-assisted gel combustion approach was adopted to fabricate a state-of-the-art LaMnO3 perovskite catalyst with a rich porous structure and hetero-interface, which can be active for low-temperature purification of toluene. Due to the large amount of gas produced during the decomposition of surfactant, the obtained catalysts own a rich porous structure, which results in a higher specific surface area and exposes more active sites. Significantly, the highly active Mn2O3-LaMnO3 hetero-interface can be generated over the non-stoichiometric perovskite successfully through adjusting the proportion of B-site element. The introduction of hetero-interfaces alters the surface structure of the material with more oxygen vacancies, leading to a significant promoting effect. It is found that the T90 of toluene (1000 ppm in air) conversion over the sample with 30 % excess manganese (La: Mn = 1: 1.3) is only 289 °C at a relatively high weight hourly space velocity (WHSV = 120,000 mL•g−1•h−1), which is 87 °C lower than that of stoichiometric LaMnO3 perovskite. This work presents a versatile strategy for preparing highly active non-precious metal catalysts for industrial applications.

Modulate synthesis of CeMn solid solution using various alcohols for toluene catalytic oxidation: synergistic effect of Ce-Mn and reaction mechanism

A redox co-precipitation method was employed to synthesize CeMn homogeneous solid solutions, utilizing various alcohols as activating agents. Ethanol effectively orchestrated the precipitation of CeO2 and MnOx, promoting their co-growth. As a result, the CeMn-EA achieved 90 % toluene conversion at 218 ℃ (T90 =218 ℃) with a weight hourly space velocity (WHSV) of 48000 ml/(g·h). It also demonstrated high adaptability to increased WHSV, suggesting its potential for industrial-scale applications. The uniform dispersion of Ce and Mn accelerated the coupling between Ce3+/Ce4+ and Mn4+/Mn3+, engineering numerous oxygen vacancies, which enhanced the activation of gas-phase oxygen and the mobility of lattice oxygen. In situ DRIFTS confirmed that toluene oxidation accommodated both Langmuir-Hinshelwood (L-H) and Mars-van Krevelen (MvK) mechanisms, with benzoate identified as a pivotal intermediate. Enhanced oxygen mobility facilitated the cleavage of the benzene ring, which was the rate-determining step. Additionally, the introduction of H2O significantly enhanced the dissociation and adsorption of toluene and facilitated the activation of gas-phase oxygen. At higher temperatures, H2O could further activate lattice oxygen engaging in toluene oxidation. Environmental ImplicationVolatile organic compounds (VOCs) have emerged as major air pollutants due to the changes in air pollution patterns. They can act as precursors to near-surface ozone and haze. Toluene, a typical VOC, is primarily released from anthropogenic sources and poses significant risks to human health and the environment. Ce-based catalysts have been demonstrated efficiency in toluene oxidation due to their excellent oxygen storage and release properties. This study synthesized CeMn homogeneous solid solutions utilizing various alcohols as activating agents, which possessed abundant oxygen vacancies and optimum oxygen activation capacity to oxidize toluene in time.

Construction of hollow sphere MnOX with abundant oxygen vacancy for accelerating VOCs degradation: Investigation through operando spectroscopycombined with on-line mass spectrometry

To clarify the key role of oxygen vacancy defects on enhancing the oxidative activity of the catalysts, metal–organic frameworks (MOFs) derived MnOX catalysts with different morphologies and oxygen vacancy defects were successfully prepared using a facile in-situ self-assembly strategy with different alkali moderators. The obtained morphologies included three-dimensional (3D) triangular cone stacked MnOX hollow sphere (MnOX-H) and 3D nanoparticle stacked MnOX nanosphere (MnOX-N). Compared to MnOX-N, MnOX-H exhibited higher activity for the oxidation of toluene (T90 = 226 °C). This was mainly due to the large number of oxygen vacancy defects and Mn4+ species in the MnOX-H catalyst. In addition, the hollow structure of MnOX-H not only facilitated toluene adsorption and activation of toluene and also provided more active sites for toluene oxidation. Reaction mechanism studies showed that the conversion of toluene to benzoate could be realized over MnOX-H catalyst during toluene adsorption at room temperature. In addition, abundant oxygen vacancy defects can accelerate the activated oxidation of toluene and the formation of oxidation products during toluene oxidation.

Efficient photothermal mineralization of toluene over MnCo2O4 with different exposed facets: Revealing the role of oxygen vacancy and photo-/thermo- synergistic mechanism

Modulating oxygen vacancies through facet engineering is a potential strategy to enhance activity of photo-/thermo- synergistic catalysis for toluene mineralization. Hence, we synthesized MnCo2O4 catalysts with exposed {01−1} facets (MCO-R), {1−1−2} facets MCO-S), and {1−10} facets (MCO-C), in which the MCO-R with the highest oxygen vacancy concentration exhibited the highest toluene conversion (95.8 %) and CO2 yield (85.5 %) under the full-spectrum light irradiation. The results of various characterizations and DFT calculations confirmed that the oxygen vacancy could accelerate the activation of lattice oxygen and molecule oxygen, thereby enhancing the photothermal catalytic toluene activity of MnCo2O4. Meanwhile, the results of performance evaluations identified that the efficient photothermal mineralization activity of toluene was induced by the photo-/thermo- synergistic catalysis. Besides, the reaction pathway studies by In-situ DRIFTS tests revealed the key role of oxygen vacancy and photo-/thermo- synergistic effects in the reaction progress of photothermal mineralization of toluene over MnCo2O4.

Insights into catalytic oxidation mechanism of toluene by lanthanum mangan-based perovskite in wet environment based on in-situ DRIFTS

This paper investigated that the catalytic activity and CO2 selectivity of LaMnO3, La0.9Ca0.1MnO3 and 3-La0.9Ca0.1MnO3 catalysts with different oxygen vacancy concentrations were compared under wet and dry conditions. The 3-La0.9Ca0.1MnO3 catalysts had excellent water resistance. The presence of H2O had less effect on toluene conversion than on CO2 selectivity. In wet environment, the 3-La0.9Ca0.1MnO3 catalyst achieved 90 % toluene conversion at 173 °C, but less than 20 % selectivity for CO2 at this time, and reached 90 % selectivity for CO2 at 220 °C. The effect of H2O on the catalytic oxidation mechanism of toluene was analyzed by in-situ DRIFTS analysis. The presence of H2O could promote the decomposition of toluene into intermediates of benzyl alcohol, benzoic acid, benzaldehyde and maleic anhydride at low temperature (50 °C), but the intermediates were difficult to decompose into CO2 and H2O. It was suggested that surface hydroxyl group could promote the transformation of toluene to intermediate at low temperature, and suitable oxygen vacancies and surface hydroxyl group could jointly promote the transformation of toluene to ideal product. This work provided a theoretical basis for the design of water-resistant catalysts in industry.

Study on the mechanism of carbon nanotube-like carbon deposition in tar catalytic reforming over Ni-based catalysts

The use of Ni-based catalysts is a common method for eliminating tar through catalytic cracking. Carbon deposition is the main cause of deactivation in Ni/ZSM-5 catalysts, with filamentous MWCNTs being the primary form of carbon deposits. This study investigates the formation and evolution of CNTs during the catalytic process of biomass tar to explore the mechanism behind carbon deposition. The effect of the 9Ni/10MWCNTs/81ZSM-5 on toluene reforming was investigated through a vertical furnace. Gases produced by tar catalysis were evaluated through GC analysis. The physicochemical structure, properties and catalytic performance of the catalyst were also tested. TG analysis was used to assess the accumulation and oxidation reactivity of carbon on the catalyst surface. An analysis was conducted on the mechanism of carbon deposition during catalyst deactivation in tar catalysis. The results showed that the 9Ni/91ZSM-5 had a superior toluene conversion of 60.49%, but also experienced rapid and substantial carbon deposition up to 52.69%. Carbon is mainly deposited as curved filaments on both the surface and pore channels of the catalyst. In some cases, tip growth occurs where both carbon deposition and Ni coexist. Furthermore, specific surface area and micropore volume are reduced to varying degrees due to carbon deposition. With the time increased, the amount of carbon deposited on the catalyst surface increased to 62.81%, which gradually approached saturation, and the overall performance of the catalyst was stabilized. This situation causes toluene molecules to detach from the active sites within the catalyst, hindering gas release, which leads to reduced catalytic activity and further carbon deposition. It provides both a basis for the development of new catalysts and an economically feasible solution for practical tar reduction and removal.

Mn-Ag bimetals supported on plate-like ZSM-5 as efficient and stable catalysts for the catalytic combustion of toluene: Synergistic effects and catalytic mechanisms

Ag-modified MnO2 loaded on plate-like ZSM-5 (PZ5) with different Ag/Mn ratios were synthesized by an in-situ growth method and used as catalysts for toluene combustion, as a probe molecule of volatile organic compounds (VOCs). The results showed that Ag doping greatly enhanced the toluene combustion activity (Mn50Agy/PZ5). Among them, Mn50Ag0.04/PZ5 showed the highest catalytic activity for toluene combustion with 90 % conversion of toluene at 234 °C (T90), and the reaction rate calculated per unit mass of Mn was 1.22×10−7 at 220 °C, which was 2.7 times higher than that of MnO2. In addition, Mn50Ag0.04/PZ5 exhibited excellent long-term stability and water resistance. Various characterizations indicated that the excellent performance of Mn50Ag0.04/PZ5 was attributed to its higher Mn2++Mn3+/Mn4+ ratios, higher reducibility, and more active surface adsorbed oxygen species. Finally, in-situ DRIFTS studies confirmed that Ag doping did not alter the catalytic combustion pathway of toluene over the Mn50Ag0.04/PZ5 catalyst but could accelerate the rate of conversion of toluene to the final products because the transfer of electrons from Ag+ to lattice oxygen persuaded the weaken of the Mn-O bond, and then made it easier for bulk lattice oxygen to migrate towards the Ag-MnO2 interface or catalysts’ surface, thus showing the better catalytic performance for toluene combustion.

Photocatalytic toluene oxidation with nickel-mediated cascaded active units over Ni/Bi2WO6 monolayers

Adsorption and activation of C–H bonds by photocatalysts are crucial for the efficient conversion of C–H bonds to produce high-value chemicals. Nevertheless, the delivery of surface-active oxygen species for C–H bond oxygenation inevitably needs to overcome obstacles due to the separated active centers, which suppresses the catalytic efficiency. Herein, Ni dopants are introduced into a monolayer Bi2WO6 to create cascaded active units consisting of unsaturated W atoms and Bi/O frustrated Lewis pairs. Experimental characterizations and density functional theory calculations reveal that these special sites can establish an efficient and controllable C–H bond oxidation process. The activated oxygen species on unsaturated W are readily transferred to the Bi/O sites for C–H bond oxygenation. The catalyst with a Ni mass fraction of 1.8% exhibits excellent toluene conversion rates and high selectivity towards benzaldehyde. This study presents a fascinating strategy for toluene oxidation through the design of efficient cascaded active units.

Reaction mechanism investigation on Plasma-Assisted steam reforming of toluene based on emission spectrum analysis and kinetic simulation

Plasma-enhanced reforming has been widely studied as an efficient technology for online tar removal. By combining reforming experiments with kinetic modeling and in-situ optical emission spectrometry (OES) analysis, interaction mechanism and coupling rules of plasma/thermal reactions during plasma-assisted steam reforming of toluene were well explored in this study. A chemistry model was innovatively developed for plasma-assisted steam reforming of toluene, and predicted experimental results under different operations conditions with superb agreements. The rate of production and sensitivity analysis implied that OH, H and N2* mainly contributed to primary toluene conversion, while the electronic attachment dissociation of H2O, H addition onto benzene ring and benzyl oxidation by OH were the most enhancing-sensitive reactions. Resultantly, toluene conversion was greatly increased with steam addition before VfH2O = 10 %, but after which VfH2O increase deteriorated the reforming performance due to the inhibition of E-N2 collision by high VfH2O. As temperature increased, plasma and thermal synergistically promoted reforming performance before 300 °C, at which > 60 % toluene was converted into small molecules such as CO, H2 and C2H2, with yields of 23.6 %, 9.4 % and 16.3 % correspondingly at 12 kJ/L, but further temperature increase would not benefit due to the reduced discharge field strength at higher temperatures, being confirmed by the decreased relative intensity of OH, CN feature bands on OES. It was initially proposed that non-thermal plasma governed the reforming process at T < 300 °C, and thermal reactions predominated at T > 500 °C after a transition region (300 ∼ 500 °C). Increase of input energy caused higher discharge field strength, promoted the electronic collision ionization or dissociation of N2 and H2O, thus enhanced toluene conversion and gas yields. A detailed reaction pathway has also been clarified.

A High Nucleus Cu-Incorporated Giant Phosphotungstate with Photocatalytic Oxidation C-H of Toluene.

Exploring a novel photocatalyst for catalytic oxidation of toluene is a sustainable strategy for energy conversion in times of an energy crisis. However, designing an effective photocatalyst for the conversion of toluene remains challenging. Herein, a novel organic monophosphonate-modified high nucleus Cu-incorporated polyoxotungstate, K8H33[{Cu0.5(H2O)4}{Cu2(O3PCH2COO)(1,4,9-α-P2W15O56)}]4·Cl·60H2O (1), has been intentionally synthesized by a self-assembly process utilizing conventional aqueous method. It reveals that 1 contains a polyanion of [{Cu0.5(H2O)}4{Cu2(O3PCH2COO)(1,4,9-α-P2W15O56)}]440- composed of four Dawson-type {1,4,9-α-P2W15} subunits, forming an oval-shaped structure and further connecting into a three-dimensional (3D) framework by lateral {Cu(H2O)4}2+. Interestingly, the trivacant {1,4,9-α-P2W15} subunits were observed in the organophosphonate acid-functionalized polyoxometalates for the first time. Notably, 1 exhibits a wonderful performance in catalytic oxidation of the recalcitrant C(sp3)-H bond of toluene to benzoic acid with a conversion as high as 97% under visible light utilizing O2 as an oxidant.