Decomposition Of Benzene Research Articles

A monolithic self-supporting ZnFe2O4/ZnO/ZnNi foam photocatalyst and application in the decomposition of gaseous benzene

Volatile organic compounds (VOCs) are major air pollutants which seriously affect ecological environment and pose threats to human health. In this investigation, a monolithic self-supporting ZnFe2O4/ZnO/ZNF(ZFO/ZnO/ZNF) photocatalyst was developed by in-situ growing ZnFe2O4 and ZnO on ZnNi foam (ZNF). Using benzene as a representative of the target gaseous contaminants, the optimal 5ZFO/ZnO/ZNF achieved a 99.8 % removal efficiency and 99.7 % mineralization efficiency within 20 min at an initial benzene concentration of 600 ppm under simulated sunlight irradiation. Moreover, this catalyst presents the lower ullage during gas–solid reaction, and thus enables durable recycling reuse of the photocatalyst, which still retains a 95.8 % benzene decomposition after 30th consecutive run. The mechanism studies reveal that the metal-mediated Z-type heterostructure of ZFO/ZnO/ZNF enhances rapid transportation of the photo-generated electrons and promotes redox potential, leading to the excellent photocatalytic oxidation activity and mineralization efficiency. This study highlights the potential of self-supporting monolithic metal-mediated catalysts and provides a key strategy for effective VOCs degradation.

Boosting visible-light response for the complete decomposition of volatile organic compounds on the Cu-oxide deposited WO3 photocatalyst by the synergistic effects of TiO2

The degradation of volatile organic compounds (VOCs) by photocatalytic systems is the most practical strategy due to its cost performance, simplicity, and environmental sustainability. To address such issues, the photocatalytic activities of tungsten trioxide (WO3) were developed by the deposition of various cocatalysts. In particular, the Cu-oxide (CuO/Cu2O)-deposited WO3 (Cu-WO3) photocatalyst could efficiently decompose acetic acid and acetaldehyde into CO2 under visible-light irradiation, although it exhibited low activity for the decomposition of benzene, toluene and xylene (BTX). Furthermore, a composite Cu-WO3/TiO2 photocatalytic system, which was fabricated by the simple physical mixing of Cu-WO3 with TiO2, was found to exhibit unprecedented reactivity for the complete decomposition of persistent BTX pollutants into CO2 under visible light irradiation. The synergistic effects of Cu-WO3 and the interfacial surface complex (ISC) formed by toluene-adsorbed TiO2 contribute to the efficient visible light response by excitation up to around 600 nm. The reaction mechanism for the enhancement of photocatalytic activity by the Cu-WO3/TiO2 composite photocatalyst is examined in this study.

Designed Nanoarchitectures of a BiOBr/BiOI Nanosheet Heterojunction Anchored on Dendritic Fibrous Nanosilica as Visible-Light Responsive Photocatalysts.

Heterojunctions, particularly those involving BiOBr/BiOI, have attracted significant attention in the field of photocatalysis due to their remarkable properties. In this study, a unique architecture of BiOBr/BiOI was designed to facilitate the rapid transfer of electrons and holes, effectively mitigating the recombination of electron-hole pairs. Accordingly, the BiOBr/BiOI nanosheet heterojunction was anchored on dendritic fibrous nanosilica (DFNS) by the immobilization of Bi2O3 nanodots in DFNS and the subsequent reaction with HBr and then HI vapors at room temperature. The 4 nm-Bi2O3 nanodots acted as a sacrificial template to form BiOX nanosheets by reaction with HX vapors (X = Br, I). The BiOBr/BiOI nanosheet heterojunction with the lateral size remained in the range of 90 to 110 nm and a thickness of 15 nm formed on DFNS, where the BiOBr:BiOI ratio in the product was controlled by the exposure time to HX vapors. The reaction sequence (HBr → HI vapors) was a key for the formation of BiOBr/BiOI nanosheet heterojunction with controlled composition. When the reaction of Bi2O3 nanodots with HI vapor was performed in the reverse sequence (HI→ HBr), the substitution of I- with Br- occurred to form BiOBr sheets on DFNS. The BiOBr/BiOI nanosheet heterojunction anchored on DFNS was used as a visible-light-driven photocatalyst for the decomposition of benzene in water under solar light, and its activity was superior to that of single BiOX nanosheets on DFNS.

Insights into the adsorption and decomposition mechanisms of tar typical model compounds (benzene, toluene and phenol) on Ni(111) surface by DFT calculations

Studying the adsorption and decomposition of tar-typical model compounds on nickel surfaces is necessary to guide catalyst design. This study investigates the adsorption and decomposition mechanisms of three typical tar model compounds (benzene-benzene ring without branched chain, toluene-benzene ring with methyl group and phenol-benzene ring with hydroxyl group) on the Ni(111) surface using density functional theory calculations. The results showed that the most stable adsorption site was Bridge0 for benzene and Bridge0-F for toluene and phenol. The adsorption energies were −0.89 eV, −0.76 eV and −0.71 eV, respectively. During decomposition, benzene will first be dehydrogenated (energy barrier of 1.57 eV) and the benzene ring will be opened after the removal of the first H atom (2.10 eV). The rate-limiting step in benzene decomposition is the first dehydrogenation step (1.57 eV). Toluene decomposes like phenol by dehydrogenating functional groups before breaking the benzene ring. The rate-limiting step in the decomposition of toluene is the ring opening of the benzene ring (1.67 eV). The dehydrogenation of the benzene ring is the rate-limiting step in the decomposition of phenol (1.74 eV). This occurs after the removal of the hydrogen atom from the hydroxyl group.

Unveiling platinum's electronic and dispersion impacts for enhanced benzene combustion: From nanoparticles to nanoclusters and single atoms

Catalytic combustion using platinum (Pt) supported on metal oxides emerges as an eco-friendly approach for benzene removal. However, relationships between Pt dispersion, adsorptive properties, and reactivity across overall Pt size regimes remain unclear, as many previous studies have focused on only one or two Pt size ranges. This study systematically examines the oxidation state, electron density, and resulting adsorptive properties of Pt across a range of sizes, including isolated atoms, sub-nanometer clusters, and nanoparticles. The as-synthesized Pt/Fe2O3 catalysts with defined Pt dispersion and electronic states on faceted Fe2O3 supports. Benzene combustion kinetics are measured over Pt entities from single atoms to sub-nanometer clusters and 2 nm particles, elucidating mechanisms and structure–reactivity links. Findings reveal surprising non-monotonic activity trends that deviate from dispersion features, with an order of: Pt sub-nanometer clusters < Pt single atoms < Pt nanoparticles. Despite high dispersion, single Pt atoms and nanoclusters exhibit lower benzene combustion activity than 2 nm Pt particles on Fe2O3. This reduced activity stems from diminished adsorptive affinity of single atoms and nanoclusters for benzene and O2, tracing back to their oxidized Pt valence states. In contrast, 2 nm Pt particles show excellent benzene and oxygen adsorption capacities enabled by metallic Pt ensembles, thus maximizing reactivity. Additional insights indicate single Pt atoms supported on Fe2O3 avoid competitive benzene/O2 adsorption through a non-competitive mechanism, moderately enhancing performance versus nanoclusters with competitive adsorption. However, Pt valence state has a greater impact than adsorption mechanisms, as Pt nanoparticles are considerably more active than single atoms and nanoclusters. In situ analysis proposes plausible benzene decomposition routes over active Pt sites. The novel findings that fine-tuning Pt dispersion and electronic structure—along with kinetic mechanisms—lead to significant variations in benzene combustion reactivity will assist rational design of efficient Pt catalysts for benzene elimination.

An SDBD plasma-based source for efficient degradation of VOCs in an enclosed environment

In this work, a surface dielectric barrier discharge (SDBD) plasma-based source powered by a bipolar pulsed power supply is reported. This source has been tested for the decomposition of toluene and benzene in an enclosed environment of size 12 ft3. Study has been performed to compare decomposition of toluene and benzene on various combinations of the applied voltages and frequencies. For about 60 min of continuous operation of the SDBD source, a decomposition efficiency of 99.7% (toluene) and 74.8% (benzene) has been achieved. For the effective generation of reactive species, the ground electrode of the SDBD source is coated with TiO2 nanoparticles. Optical emission spectroscopy diagnostic has also been used to estimate the electron temperature, which is found to be in the range of 3–6 eV. Consequently, the high energetic electrons produced via the SDBD source are the primary reason to activate the catalyst instead of ultra-violet (UV) light. The results further showed that the developed SDBD source produces powerful, immediate discharge and energetic electrons, which could be efficiently used for volatile organic compounds (VOCs) degradation. The need for feed gas, pellets and/or differential pressure has been eliminated by the developed SDBD source from the known conventional methods for VOCs decomposition.

Advancing Sustainable Decomposition of Biomass Tar Model Compound: Machine Learning, Kinetic Modeling, and Experimental Investigation in a Non-Thermal Plasma Dielectric Barrier Discharge Reactor

This study examines the sustainable decomposition reactions of benzene using non-thermal plasma (NTP) in a dielectric barrier discharge (DBD) reactor. The aim is to investigate the factors influencing benzene decomposition process, including input power, concentration, and residence time, through kinetic modeling, reactor performance assessment, and machine learning techniques. To further enhance the understanding and modeling of the decomposition process, the researchers determine the apparent decomposition rate constant, which is incorporated into a kinetic model using a novel theoretical plug flow reactor analogy model. The resulting reactor model is simulated using the ODE45 solver in MATLAB, with advanced machine learning algorithms and performance metrics such as RMSE, MSE, and MAE employed to improve accuracy. The analysis reveals that higher input discharge power and longer residence time result in increased tar analogue compound (TAC) decomposition. The results indicate that higher input discharge power leads to a significant improvement in the TAC decomposition rate, reaching 82.9%. The machine learning model achieved very good agreement with the experiments, showing a decomposition rate of 83.01%. The model flagged potential hotspots at 15% and 25% of the reactor’s length, which is important in terms of engineering design of scaled-up reactors.

Оxidative destruction of benzene in the conditions of unstationary cavitation excitation

The threshold value of the energy required for the decomposition of benzene after the cessation of cavitation has been established. The regularities of the oxidative destruction of benzene in the cyclic mode “cavitation-exposure” were established. The possibility of destruction of benzene in case of initiation of the process by introducing a certain amount of its cavitationally activated part into the water-benzene medium is shown. The role of oxygen in the cavitation decomposition of benzene was experimentally confirmed.

Decomposition of Benzene during Impacts in N2-dominated Atmospheres

Benzene is a simple neutral aromatic compound found in molecular clouds, comets, and planetary atmospheres. It has been confirmed on Jupiter, Saturn, Titan, and is expected on exoplanets. In this paper, the decomposition of benzene in a simulated asteroid or comet impact into an N2-dominated atmosphere was investigated. The impact plasma was simulated with laser-induced dielectric breakdown and the gas phase decomposition products were observed using high-resolution Fourier transform infrared spectroscopy. The gas phase decomposition products involve mainly HCN, C2H2, and smaller amounts of CH4 with yields of 3.1%–24.0%, 0–11.7%, and 0.5%–3.3%, respectively. Furthermore, in presence of water, benzene also produces CO and CO2 with yields of 2.4%–35.1% and 0.01%–4.8%, respectively. The oxidation state of the product mixture is proportional to the water content. Apart from that, a black-brownish solid phase is formed during the experiments, which makes up about 60% of the original carbon content. Our results therefore show that in anoxic N2-dominated planetary atmospheres, impacts might lead to the depletion of benzene and the formation of HCN, C2H2, and CH4 and, in the presence of water, to the formation of CO and CO2.

Plasma-catalytic steam reforming of benzene as a tar model compound over Ni-HAP and Ni-γAl2O3 catalysts: Insights into the importance of steam and catalyst support

Non-thermal plasma (NTP) coupled Ni-based catalysts are a promising method for tar steam reforming to syngas. In this work, Ni-based catalysts supported on hydroxyapatite (Ni-HAP) and γAl2O3 (Ni-γAl2O3) coupled with a coaxial dielectric barrier discharge (DBD) plasma were used to degrade biomass tar, and benzene was selected as a typical unbranched benzene ring structured tar model compound. In the NTP alone system, an increase in discharge power leads to benzene deep cracking to carbon deposition. In the NTP-catalytic system, the reaction temperature is a critical factor for catalysis, and the catalyst leads to a significant increase in benzene conversion and total gas yield, prompting the conversion of more cracking intermediates to gaseous products. Steam in the system has both positive and negative effects: a certain amount of steam can increase the amount of H· and ·OH, promoting benzene decomposition and carbon deposit elimination; excessive steam will compete for energetic electrons or oxidize the active metal in the catalyst, inhibiting benzene conversion. The Ni3-HAP catalyst exhibits the maximum benzene conversion (92.13 %) and energy efficiency (8.49 g/kWh), thanks to the formed Ni2+[I] and Ni2+[II] in the lattice due to the flexible ion exchange properties of the HAP support. The main reason for the catalyst activity degradation is carbon deposition rather than catalyst sintering. A good match among tar conversion rate, degree of decomposition, steam content and steam decomposition rate is critical for efficient and stable operation of the NTP-catalytic system.

Morphology-modulated rambutan-like hollow NiO catalyst for plasma-coupled benzene removal: Enriched O species and synergistic effects

While catalyst morphology plays an essential role in traditional thermal catalysis, the specific effects in plasma catalysis deserve further in-depth study. In the present study, hollow NiO nanospheres with a rambutan-like structure were successfully prepared by MOFs-derived method involving morphology modulation, and employed for the in-plasma catalytic oxidation of benzene. The results show an enhancement of 60 % for benzene removal, while CO2 selectivity was increased by 20 %. The energy consumption for 95 % benzene removal efficiency (RE95%) was also reduced from 3600 J/L to 1100 J/L. Specifically, the hollow spherical shell structure is more abundant in surface oxygen species, including chemisorbed oxygen and surface lattice oxygen, which can be activated by plasma; the hollow structure also modulates the plasma discharge by shielding effect. The plasma field in turn also excites the oxidation activity of NiO, thus achieving the synergistic effect. In addition, a more comprehensive benzene decomposition pathway is proposed by analysis of the gaseous and non-gaseous intermediates (tar), where the plasma non-selectively breaks the chemical bonds of reactants and the catalyst selectively oxidizes the organic intermediates to CO2, and they promote each other to achieve synergistic effects.

Decomposition of hexane and benzene by dielectric barrier discharge plasma and reaction temperature: Comparison of performance of DC nano-second pulsed power supply and AC high voltage power supply

The VOC decomposition performance of a dielectric barrier discharge plasma powered by a DC nano-second pulsed power system was compared with that of an AC high voltage power system. Benzene and hexane were selected as a representative aromatic VOC and a chain-structured VOC, respectively, and the decomposition of each VOC was conducted at the same applied voltage in both systems. The energy of electrons released from the plasma was analyzed, and the ozone production ability was evaluated under a constant applied voltage at different temperatures. Compared with AC high voltage system, the DC nano-second pulsed power system had about 32 times, 26 times, and 30 times better performances for ozone production yield, benzene decomposition yield, and hexane decomposition yield, respectively. For benzene decomposition, the ring cleavage reaction was constant at all reaction temperatures. On the other hand, the mineralization of hexane was largely improved by higher temperatures, because the dehydrogenation reaction was accelerated. Consequently, benzene decomposition was easier than hexane decomposition at the same energy.

Density functional theory and experimental study on the chemisorption and catalytic decomposition of benzene over exposed bio-char surface: The influence of unsaturated carbon atoms and potassium

Catalytic decomposition over char surface is an effective approach for tar removal. In this work, the density functional theory (DFT) and experiments were used to study the complicated mechanism of the interaction between specific sites on char surface and tar compound at molecular level. Two kinds of bio-char models were used and compared. Three molecular reaction paths were built and corresponding species were optimized. The characteristics of electron density of key components and reaction potential energy were calculated and analyzed. Results show that heterogeneous adsorption of benzene on the active sites of char surface could effectively enhance the decomposition of benzene due to the electron shift caused by chemisorption on char surface. The decomposition temperature is largely reduced from 1100℃ to 900℃ or lower. The band gaps indicate that benzene tends to be more likely excited by model char without potassium, which has more dangling bond on char surface. Potential energy results of three reaction paths show that activation energies of about 208.64 kJ/mole and 163.32 kJ/mole are needed for ring breakage of benzene in Path-1 and Path-2, which are much lower than that of thermal decomposition. The energy barrier for benzene decomposition over char-K is 270.04 kJ/mole. Potassium plays a negative effect on the cracking of tar due to the pore polycondensation and occupation of active sites. Kinetic analysis reveals that the char-tar interactions are largely affected by temperature and higher temperature benefits the breakage of aromatic ring. Experimental results indicate that improving the porosity and surface area of char, especially the active surface area with unsaturated carbon atoms, is crucial for the activation and decomposition of aromatic tar compounds.

Decomposition of benzene as a biomass gasification tar in CH4 carrier gas using non-thermal plasma: Parametric and kinetic study

In this work, the decomposition of benzene was studied with CH4 using a dielectric barrier discharge (DBD) reactor. The experimental conditions such as input power, residence time, and concentration were varied to investigate the decomposition of benzene. The decomposition of benzene increased with increasing input power and residence time. The highest decomposition of benzene at 40 W and 2.86 s was 82.9%. The major gaseous products were H2 and lower hydrocarbons (LHC) and the yield of these products also increases with input power and residence time. The percentage yield of H2 increases from 0.65 to 5.18% by increasing input power from 5 to 40 W at 2.86 s. Similarly, the yield of LHC increases from 0.78 to 8.86% for benzene under the same reaction conditions. Hence, input power promoted the decomposition of tar compounds and enhanced the yield of gaseous products. However, at higher concentrations of the tar compound, decomposition efficiency and product yield decreased. The modified first-order kinetic model was used for the decomposition of tar model compound and methane carrier gas.

Surface enrichment promotes the decomposition of benzene from air

Doping TiO2 with copper can strengthen the absorption of benzene and facilitate the generation of hydroxyl radicals. It can photocatalytically remove very low concentrations of gaseous benzene (4 mg m−3) in air, even at a flow rate of 100 L min−1.

Low Temperature Combustion of VOCs with Enhanced Catalytic Activity Over MnO2 Nanotubes Loaded with Pt and Ni-Fe Spinel.

MnO2 nanotubes loaded with Pt and Ni-Fe spinel were synthesized using simple hydrothermal and sol-gel techniques. After loading with Ni-Fe spinel, the specific surface area of the material increases 3-fold. This change helped to provide more active sites and facilitated the association between the catalyst and volatile organic compounds (VOCs). X-ray photoelectron spectroscopy determined that the adsorbed oxygen concentrations were all greatly increased after Pt loading, indicating that Pt promoted the adsorption of oxygen and so accelerated the combustion process. The performance of the catalyst after loading with 2 wt % Pt was greatly improved, such that the T90 for benzene decomposition was decreased to 113 °C. In addition, the 2% Pt/2Mn@NFO exhibited excellent low-temperature catalytic activity when reacting with low concentrations of toluene and ethyl acetate. This work therefore demonstrates a viable new approach to the development of Mn-based catalysts for the low temperature catalytic remediation of VOCs.

Mechanism of formaldehyde and benzene adsorption on UIO-66 in coordination with gaseous H2O2 using density functional theory

Formaldehyde and benzene adsorption on UIO-66 in coordination with gaseous H2O2 is an efficient and recyclable method for removing formaldehyde and benzene. In this study, the interaction mechanism of formaldehyde and benzene coordinated with UIO-66 under the existence of H2O2 was studied using density functional theory. The results showed that the decomposition of H2O2 by UIO-66 was promoted to produce highly oxidizing hydroxyl groups. The structure of formaldehyde obviously changed in H2O2/UIO-66 system after equilibrium. The CH bond of HCHO molecule was easy to break at different adsorption sites of UIO-66. Comparatively, benzene with distorted ring structure tended to chemically bound to the carbon site of UIO-66, but the decomposition of benzene was difficult. Density of states analysis showed that the adsorption between C6H6 and UIO-66 was chemisorption. The study is of great significance for providing theoretical guidance to the removal of organic pollutants from exhaust gas by UIO-66.

Benzene decomposition by non-thermal plasma: A detailed mechanism study by synchrotron radiation photoionization mass spectrometry and theoretical calculations

Non-thermal Plasma (NTP) catalysis is considered as one of the most promising technologies to address a wide range of environmental needs, such as volatile organic compounds (VOCs) and NOx removal. To meet the updated environmental emission standard, the NTP catalysis reaction system needs to be better understood and further optimized. In this work, the degradation process of benzene in NTP, which is still regarded as a “black box” process, was explored by synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). For the first time, we observed over 20 representative species by PIMS and identified their structures accurately by photoionization efficiency (PIE) spectra. Phenol, acetylene and acrolein were recognized as the three main products. More intriguingly, concentration profiles demonstrated that a large amount of acrolein and also several higher-order products, which were usually neglected in previous research, were produced during the NTP destruction process. The details of the benzene degradation reaction mechanism, were finally established by the combination of SVUV-PIMS results, thermochemistry and theoretical calculations. This work helps to complete the mechanistic picture of plasma chemistry, which may be helpful on raveling the more complicated NTP catalysis mechanism in the future therefore contributing to design of improved NTP system for environmental applications.

Biodegradation of Weathered Petroleum Hydrocarbons Using Organic Waste Amendments

Extraction, transport, and processing of petroleum products have resulted in inadvertent contamination of soil. Various technologies have been proposed for removal of petroleum hydrocarbon contaminants, including biological techniques. Treatment of aged (weathered) petroleum compounds is challenging, as these wastes tend to be enriched with recalcitrant hydrocarbons. The purpose of the reported study was to investigate remediation of weathered petroleum via simulated landfarming using selected soil amendments. Soil contaminated by aged crude petroleum from well fields in the southern Zagros region in Iran was treated in combination with plant compost, papermill sludge, activated carbon, and molasses. Over 15 weeks, the greatest percentage removal (40%) of total petroleum hydrocarbons (TPH) occurred in the molasses treatment, followed by a 29% reduction in the plant compost treatment. The degradation constant (k), produced by a kinetic model, demonstrated the performance of the molasses over the other treatments applied; experimental data adequately fitted into first-order kinetics (k = 0.005 d−1, t½ = 71 d). Benzene decomposition was greatest (77 and 74%) in the molasses and activated carbon treatments, respectively, and was lowest in the papermill sludge treatment (41%). FTIR analysis revealed loss of benzene in all treatments. Bacterial counts were highest (4.9 × 106 CFU/g) in the plant compost treatment and lowest (1 × 105 CFU/g) in the untreated oil-contaminated soil. Based on the findings of the current study, it is possible to successfully conduct landfarming of aged petroleum deposits; however, it is recommended that common and inexpensive amendments such as molasses and plant compost be used when feasible.

Removal of benzene as a tar model compound from a gas mixture using non-thermal plasma dielectric barrier discharge reactor

In the present work, the decomposition of benzene as a tar model compound was studied in a gas mixture (CO2, H2, CO, and CH4) using a dielectric barrier discharge (DBD) non-thermal plasma reactor. The combined effect of temperature and power was studied to investigate the performance of the DBD reactor. The decomposition of tar compound increased from 49.9 to 96% with increasing specific input energy (SIE) from 2.05 to 16.4 kWh/m3. The major products were lower hydrocarbons (C2–C5) and solid residues. The higher temperature (400 °C) in the presence of plasma (40 W), decreased the conversion of tar compound from 96 to 78%. However, the selectivity of lower hydrocarbons increases substantially to 52%, and the formation of solid residues is significantly reduced. Hence, the problematic solid residues formation can be controlled at a higher temperature during the treatment of gasifier product gas using non-thermal plasma.