Oxidation Of Benzene Research Articles

Catalytic removal of harmful volatile organic compounds by reutilizing zinc rods waste from spent batteries as a palladium catalyst support

The emission of volatile organic compounds (VOCs) has led to significant deterioration in air quality, making it imperative to ensure that these compounds are removed from emission sources before they are released into the atmosphere. In this context, the present study recycled spent primary batteries to use their zinc rods waste (ZRW) as a palladium catalyst support for the removal of harmful VOCs. To this end, palladium supported on ZRW (Pd/ZRW) catalysts were prepared and tested for the catalytic oxidation of benzene, methylbenzene and 1,2-dimethylbenzene. The physicochemical properties of the Pd/ZRW catalysts were carefully characterized by ICP-OES, BET, SEM, XRD, FE-TEM, XPS, and H2-TPR analyses. The main component of ZRW was identified as ZnO. Consistent with expectations, increases in the loading of Pd from 0.1 to 1.0 wt% in the Pd/ZRW catalysts resulted in enhanced VOCs removal efficiency. The reaction temperature required for the complete oxidation (100% removal efficiency) of methylbenzene and 1,2-dimethylbenzene on the 1.0 wt% Pd/ZRW catalyst was below 340 °C at a gas hourly space velocity of 50,000 h−1. TEM, XPS, and H2-TPR results implied that the enhancement of catalytic activity with the addition of Pd could be attributed to the readily movable surface lattice oxygen as well as the active component (Pd species). Ultimately, ZRW of spent primary batteries appear to show promise as a catalyst support for VOCs removal. This study has introduced a novel strategy for reducing air pollutants by utilizing waste, which promotes the disposal of hazardous solid waste and ensures clean air quality.

Potential for the anaerobic oxidation of benzene and naphthalene in thermophilic microorganisms from the Guaymas Basin.

Unsubstituted aromatic hydrocarbons (UAHs) are recalcitrant molecules abundant in crude oil, which is accumulated in subsurface reservoirs and occasionally enters the marine environment through natural seepage or human-caused spillage. The challenging anaerobic degradation of UAHs by microorganisms, in particular under thermophilic conditions, is poorly understood. Here, we established benzene- and naphthalene-degrading cultures under sulfate-reducing conditions at 50°C and 70°C from Guaymas Basin sediments. We investigated the microorganisms in the enrichment cultures and their potential for UAH oxidation through short-read metagenome sequencing and analysis. Dependent on the combination of UAH and temperature, different microorganisms became enriched. A Thermoplasmatota archaeon was abundant in the benzene-degrading culture at 50°C, but catabolic pathways remained elusive, because the archaeon lacked most known genes for benzene degradation. Two novel species of Desulfatiglandales bacteria were strongly enriched in the benzene-degrading culture at 70°C and in the naphthalene-degrading culture at 50°C. Both bacteria encode almost complete pathways for UAH degradation and for downstream degradation. They likely activate benzene via methylation, and naphthalene via direct carboxylation, respectively. The two species constitute the first thermophilic UAH degraders of the Desulfatiglandales. In the naphthalene-degrading culture incubated at 70°C, a Dehalococcoidia bacterium became enriched, which encoded a partial pathway for UAH degradation. Comparison of enriched bacteria with related genomes from environmental samples indicated that pathways for benzene degradation are widely distributed, while thermophily and capacity for naphthalene activation are rare. Our study highlights the capacities of uncultured thermophilic microbes for UAH degradation in petroleum reservoirs and in contaminated environments.

Development of a Kinetic Model for the Direct Oxidation of Benzene to Phenol by Oxygen in Dielectric Barrier Discharge

Development of a Kinetic Model for the Direct Oxidation of Benzene to Phenol by Oxygen in Dielectric Barrier Discharge

Extraction of Silica from Different Solid Wastes and Its Application as Catalyst Support for Vapour Phase Oxidation of Aromatic Hydrocarbon

In present study, the research work has been divided into two sections viz. Firstly, amorphous silica was extracted from different silica rich agricultural and industrial waste materials (fly ash, perlite and rice husk ash) via sol-gel method. The extracted silica (RHA-Si, Perlite-Si, FA-Si) was characterized using BET surface area, FESEM, EDS, XRD, NMR and FTIR techniques. The surface area and particle size of extracted silica was found to be 23.06-255.5 m2/g and 61-267 nm. Secondly, fly ash silica was used as catalyst support and modified desirably by loading different molybdenum weight percentages via acid impregnation method. The presence of MoO3 on the surface of extracted silica were confirmed by different characterization techniques. The kinetic studies of the FASi/Mo-15 catalyst for the vapour phase oxidation of benzene was also investigated by employing the Mars Van Krevelen model to analyze the reaction mechanism and rate of the process. The vapour phase oxidation reaction follows zero order kinetics, with faster benzene conversion occurring at lower intake concentrations and higher reaction temperatures.

Density functional studies on the thermal decomposition of H2O2 and heterogeneous oxidation of benzene on the Cu surface

The related research of volatile organic compounds (VOCs) is of great significance to atmospheric governance. Benzene is extremely harmful to humans and the environment as a representative substance in VOCs. In recent years, H2O2, a highly effective oxidant, has seen usage in flue gas purification. However, the purification efficiency remains limited due to the low utilization rate of hydroxyl radicals (·OH), which are derived from H2O2 decomposition. This research primarily focuses on catalyst selection. Density functional theory (DFT) was employed to investigate the characteristics of H2O2 adsorption and decomposition on Cu-based catalysts, as well as the ineffective consumption reaction of·OH on the Cu surface. Concurrently, the interaction mechanism between benzene and·OH on Cu surface was investigated. The findings demonstrate that Cu-based catalysts can enhance the decomposition of H2O2 molecules, and that H2O2 can dissociate to·OH on the surface. Moreover, these catalysts exert a pronounced inhibitory effect on the ineffective consumption reaction between·OH, H2O2 molecules, and the HO2·. The degradation process of benzene under the influence of·OH was analyzed, and the critical step of the reaction, along with the specifics of the ring-opening reaction, were determined. These reactions mechanisms were elucidated, thereby providing theoretical support for the development of novel catalysts.

Catalytic degradation of benzene at room temperature over FeN4O2 sites embedded in porous carbon

Benzene and its aromatic derivatives are typical volatile organic compounds for indoor and outdoor air pollution, harmful to human health and the environment. It has been considered extremely difficult to break down benzene rings at ambient conditions without external energy input, due to the extraordinary stability of the aromatic structure. Here, we show one such solution that can thoroughly degrade benzene to basically water and carbon dioxide at 25 °C in air using atomically dispersed Fe in N-doped porous carbon, with almost 100% benzene conversion. Further experimental studies combined with molecular simulations reveal the mechanism of this catalytic reaction. Hydroxyl radicals (·OH) evolved on the atomically dispersed FeN4O2 catalytic centers were found responsible for initiating and completing the oxidation of benzene. This work provides a new chemistry to degrade aromatics at ambient conditions and also a pathway to generate active ·OH oxidant for generic remediation of organic pollutants.

Photocatalytic Oxidation of Benzene to Phenol and Dye Over N and S Doped Ferromagnetic Nanosize TiO2

Photocatalytic Oxidation of Benzene to Phenol and Dye Over N and S Doped Ferromagnetic Nanosize TiO2

Development of a Kinetic Model for the Direct Oxidation of Benzene to Phenol by Oxygen in Dielectric Barrier Discharge

A simplified model of the process of benzene oxidation by oxygen in a dielectric barrier discharge has been developed. A kinetic scheme of oxidation is proposed that reflects the real chemistry of the process. The simulation results confirm the earlier assumptions about the main stages of the benzene oxidation process with oxygen.

Improving benzene catalytic oxidation on Ag/Co3O4 by regulating the chemical states of Co and Ag

Silver (9 wt.%) was loaded on Co3O4-nanofiber using reduction and impregnation methods, respectively. Due to the stronger electronegativity of silver, the ratios of surface Co3+/Co2+ on Ag/Co3O4 were higher than on Co3O4, which further led to more adsorbed oxygen species as a result of the charge compensation. Moreover, the introducing of silver also obviously improved the reducibility of Co3O4. Hence the Ag/Co3O4 showed better catalytic performance than Co3O4 in benzene oxidation. Compared with the Ag/Co3O4 synthesized via impregnation method, the one prepared using reduction method (named as AgCo-R) exhibited higher contents of surface Co3+ and adsorbed oxygen species, stronger reducibility, as well as more active surface lattice oxygen species. Consequently, AgCo-R showed lowest T90 value of 183°C, admirable catalytic stability, largest normalized reaction rate of 1.36 × 10−4 mol/(h·m2) (150°C), and lowest apparent activation energy (Ea) of 63.2 kJ/mol. The analyzing of in-situ DRIFTS indicated benzene molecules were successively oxidized to phenol, o-benzoquinone, small molecular intermediates, and finally to CO2 and water on the surface of AgCo-R. At last, potential reaction pathways including five detailed steps were proposed.

Hydroxyl-Decorated Pt as a Robust Water-Resistant Catalyst for Catalytic Benzene Oxidation.

In catalytic oxidation reactions, the presence of environmental water poses challenges to the performance of Pt catalysts. This study aims to overcome this challenge by introducing hydroxyl groups onto the surface of Pt catalysts using the pyrolysis reduction method. Two silica supports were employed to investigate the impact of hydroxyl groups: SiO2-OH with hydroxyl groups and SiO2-C without hydroxyl groups. Structural characterization confirmed the presence of Pt-Ox, Pt-OHx, and Pt0 species in the Pt/SiO2-OH catalysts, while only Pt-Ox and Pt0 species were observed in the Pt/SiO2-C catalysts. Catalytic performance tests demonstrated the remarkable capacity of the 0.5 wt % Pt/SiO2-OH catalyst, achieving complete conversion of benzene at 160 °C under a high space velocity of 60,000 h-1. Notably, the catalytic oxidation capacity of the Pt/SiO2-OH catalyst remained largely unaffected even in the presence of 10 vol % water vapor. Moreover, the catalyst exhibited exceptional recyclability and stability, maintaining its performance over 16 repeated cycles and a continuous operation time of 70 h. Theoretical calculations revealed that the construction of Pt-OHx sites on the catalyst surface was beneficial for modulating the d-band structure, which in turn enhanced the adsorption and activation of reactants. This finding highlights the efficacy of decorating the Pt surface with hydroxyl groups as an effective strategy for improving the water resistance, catalytic activity, and long-term stability of Pt catalysts.

Enhancing water resistance of α-MnO2 catalyst for efficient airborne benzene oxidation at mild temperatures via facile Ag incorporation

Facile structural modification of α-MnO2via single incorporation of Ag element was applied to achieve high-efficiency oxidation removal of benzene, particularly under wet gas. Ag+ ions could enter the MnO2 structure by partially replacing the tunnel K+ ions, leading to lower crystallinity, smaller crystallite and distorted lattice arrangement. Due to electron transfer from Ag+ to lattice oxygen, Ag decoration weakened Mn-O bonds and the bulk lattice oxygen became more mobile to migrate towards the Ag-MnO2 surface, resulting in the larger number of surface lattice oxygen. Along with the abundance of oxygen species, the reactivity of surface adsorbed oxygen and lattice oxygen was significantly improved as well by Ag modification. All these factors were favorable to the complete C6H6-to-CO2 conversion. Gaseous benzene could be directly oxidized by oxygen species over the pristine MnO2 catalyst, while the adsorptive activation of gaseous benzene was required for the Ag-MnO2 before further oxidation. As to the Ag-MnO2’s endurability of moisture-aroused inactivation, Ag species oppressed water adsorption in the form of strong adsorbate, thus preventing structural damage of the catalyst during humid benzene oxidation. Moreover, water molecules could enhance the “Ag-MnO2vs. adsorbed benzene” interaction, which increased the oxidation efficiency of adsorbed benzene. However, the strong binding of water vapor with the MnO2 surface would cause strong restriction of gaseous benzene from approaching the surface oxygen species, resulting in much less benzene being oxidized under wet gas.

Highly selective oxidation of benzene to phenol with air at room temperature promoted by water

Phenol is one of the most important fine chemical intermediates in the synthesis of plastics and drugs with a market size of ca. $30b1 and the commercial production is via a two-step selective oxidation of benzene, requiring high energy input (high temperature and high pressure) in the presence of a corrosive acidic medium, and causing serious environmental issues2–5. Here we present a four-phase interface strategy with well-designed Pd@Cu nanoarchitecture decorated TiO2 as a catalyst in a suspension system. The optimised catalyst leads to a turnover number of 16,000–100,000 for phenol generation with respect to the active sites and an excellent selectivity of ca. 93%. Such unprecedented results are attributed to the efficient activation of benzene by the atomically Cu coated Pd nanoarchitecture, enhanced charge separation, and an oxidant-lean environment. The rational design of catalyst and reaction system provides a green pathway for the selective conversion of symmetric organic molecules.

Benzene Oxidation over Pt Loaded on Fly Ash Zeolite X

In the present study, zeolite X (FANaX) was synthesized from coal fly ash (FA) by a two-step high-temperature method. In order to follow the effect of different contaminants in the starting coal ash, zeolite X was also synthesized from pure chemicals according to a classical recipe (NaX). Iron was loaded on this reference zeolite with the amount which was contained in the coal FA. The final catalytic samples were obtained by wet impregnation of Pt nanoparticles on both types of zeolite crystals. The most active samples in the benzene oxidation were the platinum-modified ones and, among them, the Pt-impregnated FA zeolite (Pt FANaX). The comparison of the catalytic activity of Pt FANaX with the reference PtFe NaX zeolite showed a temperature difference of 10 °C in favor of Pt FANaX at 50% benzene conversion. From these results, it can be concluded that FA zeolites are a good, cheaper and environmentally friendly alternative to traditional zeolites, synthesized from pure chemicals, which can be applied in the preparation of catalysts for the purification of gaseous mixtures from harmful organic compounds.

The enhancement of benzene total oxidation over RuxCeO2 catalysts at low temperature: The significance of Ru incorporation

Catalytic oxidation is considered to be the most efficient technology for eliminating benzene from waste gas. The challenge is the reduction of the catalytic reaction temperature for the deep oxidation of benzene. Here, highly efficient RuxCeO2 catalysts were utilized to turn the number of surface oxygen vacancies and Ce–O–Ru bonds via a one-step hydrothermal method, resulting in a preferable low-temperature reducibility for the total oxidation of benzene. The T50 of the Ru0.2CeO2 catalyst for benzene oxidation was 135 °C, which was better than that of pristine CeO2 (239 °C) and 0.2Ru/CeO2 (190 °C). The superior performance of Ru0.2CeO2 was attributed to its large surface area (approximately 114.23 m2·g−1), abundant surface oxygen vacancies, and Ce–O–Ru bonds. The incorporation of Ru into the CeO2 lattice could effectively facilitate the destruction of the CeO bond and the facile release of lattice oxygen, inducing the generation of surface oxygen vacancies. Meanwhile, the bridging action of Ce–O–Ru bonds accelerated electron transfer and lattice oxygen transportation, which had a synergistic effect with surface oxygen vacancies to reduce the reaction temperature. The Ru0.2CeO2 catalyst also exhibited high catalytic stability, water tolerance, and impact resistance in terms of benzene abatement. Using in situ infrared spectroscopy, it was demonstrated that the Ru0.2CeO2 catalyst can effectively enhance the accumulation of maleate species, which are key intermediates for benzene ring opening, thereby enhancing the deep oxidation of benzene.

Thermo-photocatalytic oxidation of benzene under visible light over nitrogen-doped titania grafted with Cu and Pt

Nitrogen-doped titania (TiO2-N) was synthesized and tested, both in unmodified form and with grafted Cu and Pt particles, in the reaction of photocatalytic oxidation of benzene under visible light irradiation at temperatures of 40, 100 and 140 °C. The results obtained indicate additional thermal activation of the reaction over Pt-containing samples with the maximum difference between the total and thermal activities at 100–120 °C. As modifiers, both platinum and copper separately improve the photoactivity of TiO2-N, but when used together, their effects do not add up, and the photocatalyst behaves like a Pt-modified sample.

Selective oxidation of benzene to phenol in the liquid phase over copper-substituted LaFeO3 perovskite oxide as catalyst

Abstract Selective oxidation of benzene to phenol is done in the liquid phase over copper-substituted LaFeO3 perovskite oxides as catalyst using H2O2 as oxidant under mild reaction conditions. Among the different copper-substituted perovskite catalysts synthesized by a novel solution combustion method, the LaFe0.90Cu0.10O3 catalyst showed highest activity (∼56 % with 100 % selectivity of phenol) and also gives better activity than the corresponding catalyst made via incipient wetness impregnation of 10 at % Cu over combustion-synthesized LaFeO3. XRD analysis revealed formation of the perovskite phase as the predominant one. The greater activity of the combustion-made catalyst has been attributed to the occurrence of a peculiar poorly-defined structure having substitutional copper ion sites on top of the LaFeO3 particle as observed in HRTEM analysis. Much less occurrence of this phase in the impregnated catalyst, where copper is primarily present as dispersed CuO crystallites, explains its comparatively lower activity in the oxidation reaction. The effect of catalyst recycling shows negligible change of activity for the combustion-made catalyst whereas the analogous impregnated catalyst shows considerable decrease in activity in recycling. This explained to be due to the essentially intact poorly-defined structure in the former and leaching of the finely dispersed CuO crystallites from the latter catalyst during cycling.

The atmospheric oxidation mechanism of acetophenone initiated by the hydroxyl radicals

Acetophenone (C8H8O, AP) is a common indoor air component but with no information on its atmospheric oxidation. The atmospheric oxidation mechanism of AP in gas phase, initiated by its reaction with the OH radical, is investigated here using quantum chemistry and chemical kinetics calculations. The reaction starts mainly by OH additions to the aromatic ring, and the predicted rate coefficient suggests a lifetime of ∼8 days in the atmosphere. The additions form adducts AP-i-OH (Ri) (i = 1, 2, 3, 4, the position on the aromatic ring). The adducts Ri would react with O2 or undergo unimolecular decompositions. The adduct R1 reacts with O2 rather slowly with an effective rate coefficients of <10−20 cm3 molecule−1 s−1, and it would alternatively decompose to phenol and acetyl radical. The dominate fate of R2, R3, and R4 in their reaction with O2 proceeds via direct hydrogen-atom abstraction, forming hydroxyacetophenones, and only R3 would have a fraction of bicyclic radical formation as in oxidation of alkyl benzenes. The main products from oxidation of AP include phenol and three isomers of hydroxyacetophenones, suggesting that oxidation of AP by OH would reduce its unpleasant effect to human beings.

Enabling Specific Benzene Oxidation by Tuning the Adsorption Behavior on Au Loaded MgAl Layered Double Hydroxides.

Direct and selective oxidation of benzene to phenol is a long-term goal in industry. Although great efforts have been made in homogenous catalysis, it still remains a huge challenge to drive this reaction via heterogeneous catalysts under mild conditions. Herein, a single-atom Au loaded MgAl-layered double hydroxide (Au1 -MgAl-LDH) with a well-defined structure, in which the Au single atoms are located on the top of Al3+ with Au-O4 coordination as revealed by extended x-ray-absorption fine-structure (EXAFS)and density-functional theory (DFT)calculation is reported. The photocatalytic results prove the Au1 -MgAl-LDH is capable of driving benzene oxidation reaction with O2 in water, and exhibits a high selectivity of 99% for phenol. While contrast experiment shows a ≈99% selectivity for aliphatic acid with Au nanoparticle loaded MgAl-LDH (Au-NP-MgAl-LDH). Detailed characterizations confirm that the origin of the selectivity difference can be attributed to the profound adsorption behavior of substrate benzene with Au single atoms and nanoparticles. For Au1 -MgAl-LDH, single Au-C bond is formed in benzene activation and result in the production of phenol. While for Au-NP-MgAl-LDH, multiple AuC bonds are generated in benzene activation, leading to the crack of CC bond.

Catalytic oxidation of Benzene with manganese oxide supported on Cordierite

Volatile organic compounds (VOCs) are one of the principal causes of air pollution, posing a grave danger to the environment and human health due to their toxicity. In the presence of heat or light, catalytic oxidation has been recognized as a viable and efficient approach for VOCs remediation. Manganese-based oxides are one of the most environmentally benign and cost-effective choices for the catalytic destruction of volatile organic compounds in thermocatalysis. That is the reason why this article focused on catalytic oxidation to control benzene (a VOCs component). The wet impregnation process was used to produce manganese oxide supported on cordierites. Scanning electron microscopy (SEM), energy dispersive spectrometer mapping (EDS mapping), X-ray diffraction (XRD), and Hydrogen Temperature-programmed reduction (TPR-H2) were used to characterize the catalysts. When using the TCD-FID detector, catalytic activity measurements were done on a micro-flow reactor system coupled online to GC. The results showed that MnO2-Cor potential catalyst for completely oxidizing benzene with a 100% benzene conversion temperature of 350 C to CO2 and H2O. This catalyst provides high thermal stability and good reusability due to being carried on cordierite.

Engineering oxygen vacancies of 2D WO3 for visible-light-driven benzene hydroxylation with dioxygen

Solar-driven benzene oxidation with dioxygen (O2) provides a green and sustainable alternative for phenol production, but the construction of heterogeneous photocatalysts remains a huge challenge for efficient conversion under visible light irradiation and ambient conditions. Herein, we reported a facile microwave assisted strategy for the defect engineering of two-dimensional (2D) tungsten oxide while well maintaining the original crystalline architecture. Abundant oxygen vacancies were constructed on the 2D tungsten oxide, which remarkably promoted photochemical (light harvesting, charge separation and transfer) and O2 activation behaviors, this promotion effect was further strengthened by the hybridization with Pt species with the formation of Schottky junction. The champion catalyst enabled a high phenol yield of 11.3% with a selectivity of 91% in the visible-light-driven benzene hydroxylation with atmospheric O2 at room temperature. The catalyst can be facilely recovered and reused with stable activity. The oxygen vacancies and Pt co-catalyst were demonstrated to play vital roles in the photocatalytic formation of the reactive oxygen species (hydroxyl radials, ·OH) for effective oxidation.