Decomposition Of Benzene Research Articles

Kinetic modeling of benzene and toluene decomposition in air and in flue gas under electron beam irradiation

Computer simulations of benzene and toluene decomposition in air (79% N2+21% O2) and in flue gas (87% N2+10% O2+3% H2O+160ppm SO2+80ppm NO) under electron beam (EB) irradiation were carried out using computer code KINETIC and GEAR method. 285 reactions involving 73 species and 294 reactions involving 78 species were considered for simulation of benzene and toluene decomposition, respectively. Calculation results of benzene and toluene decomposition in air under electron beam agree well with the published experimental results. OH radicals play a main role in benzene or toluene decomposition.

Synthesis, morphology, and magnetic properties of NiCo/carbon nanocomposites

Abstract

Effect of Pt/γ-Al2O3 Catalyst on Nonthermal Plasma Decomposition of Benzene and Byproducts

This article presents the effects of different packing materials in dielectric barrier discharge (DBD) reactor on benzene removal efficiency to clarify the mechanism of combining efficiency between nonthermal plasma and catalyst over organic contaminants degradation. The influence of γ-Al2O3 and Pt/γ-Al2O3 catalysts on benzene decomposition was examined by passing gaseous benzene through two DBD reactors, each packed with one of the catalysts mentioned above. Concentrations of benzene, CO, CO2, NO2, and NO were measured and decomposition efficiency (of benzene), selectivity (of CO and CO2), and carbon balance were calculated to compare the effects of γ-Al2O3 catalyst with that of Pt/γ-Al2O3 catalyst in DBD reactors on benzene degradation. Data showed that at the same input energy density, benzene decomposition efficiency increased by about 20%, whereas the amount of CO released decreased by about 50% when using Pt/γ-Al2O3 catalyst. From the Arrhenius plot, the activation energy of Pt/γ-Al2O3 catalyst was calculated to be 3.01 kJ/mol, which turned out to be less than that of γ-Al2O3 catalyst by 57%. Further, the amounts of NO2 and NO released from the reactor when using Pt/γ-Al2O3 catalyst were only about 1/3 and 1/6 of that when using γ-Al2O3 catalyst, respectively. Therefore, Pt/γ-Al2O3 is a better catalyst because of the higher benzene decomposition efficiency, lower activation energy, and less byproducts generated when it was used in DBD reactor.

BiVO4/TiO2 nanocrystalline heterostructure: A wide spectrum responsive photocatalyst towards the highly efficient decomposition of gaseous benzene

A low-cost, time-saving coupling method was developed to prepare a novel BiVO4/TiO2 heterostructure photocatalyst. Benzene was selected as a target pollutant to evaluate the enhanced heterogenous photocatalytic oxidation process of this photocatalyst. The results clearly indicated that the addition of BiVO4 accelerated the degradation of benzene, and the optimum composition was recognized as BiVO4: TiO2 with ratio of 1:200 (mass ratio). Compared with TiO2−xNx (nitrogen-doped TiO2), its efficiency of removing gaseous benzene and producing CO2 under visible light irradiation (λ>450nm) was demonstrated more than 3 and 4 times, respectively. Such high conversion and mineralization ratio could be maintained for more than 50h. Applications were also given for the photocatalytic elimination of gaseous benzene under simulated solar light and UV light irradiation. The benzene conversion reached 92% and 11%, corresponding to extremely high mineralization ratios of about 80% and 84%, respectively. Hence, this improved wide spectrum responsive photocatalyst would be needed, which were of importance to the potential application in the photocatalytic field.

Carbon Nanostructures Production by AC Arc Discharge Plasma Process at Atmospheric Pressure

Carbon nanostructures have received much attention for a wide range of applications. In this paper, we produced carbon nanostructures by decomposition of benzene using AC arc discharge plasma process at atmospheric pressure. Discharge was carried out at a voltage of 380 V, with a current of 6 A–20 A. The products were characterized by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (XRD), and Raman spectra. The results show that the products on the inner wall of the reactor and the sand core are nanoparticles with 20–60 nm diameter, and the products on the electrode ends are nanoparticles, agglomerate carbon particles, and multiwalled carbon nanotubes (MWCNTs). The maximum yield content of carbon nanotubes occurs when the arc discharge current is 8 A. Finally, the reaction mechanism was discussed.

Influence of benzene on the Ni 3Fe nanocrystalline compound formation by wet mechanical alloying: An investigation combining DSC, X-ray diffraction, mass and IR spectrometries

Nanocrystalline Ni 3Fe powders were obtained via wet mechanical alloying using benzene as surfactant. The differential scanning calorimetry (DSC) measurements showed the presence of an exothermic peak which does not correspond to any phase transformation or phase formation as was proved by X-ray diffraction measurements. The exothermic peak was observed neither for the dry milled samples nor for the wet milled and subsequently annealed powders at 350 °C for 4 h. The infra-red (IR) spectra registered for the wet milled samples showed a series of vibration bands corresponding to C 6H 6 and also to a series of fragments resulting from benzene decomposition. The results obtained by IR investigation were confirmed by thermogravimetry and mass spectrometry (TG + MS) investigations. The main fragments resulting from the benzene decomposition on the surface of the nanocrystalline Ni 3Fe powders are: CO 2, CO and C. The evolution of the particle size distribution versus the milling time has been determined for the wet mechanical milling process of nanocrystalline Ni 3Fe powders. The DSC analysis reveals a displacement of the exothermic peak onset towards lower temperatures and an increase of the surface of this peak attributed to the changes in the particles specific surface and to the quantity of benzene added in the milling experiments.

Influence of CS2 on the growth of carbon nanotubes

The current work is focused on the impact of sulphur on the growth of carbon nanostructures by the decomposition of benzene in the presence of ferrocene at reduced pressure. The influence has been studied for a wide range of sulphur concentrations. Its effect on the processes taking place inside the reactor, beginning from the decomposition of the chemical compounds up to the formation of the different structures is shown.

Preparation of carbon spheres by low-temperature pyrolysis of cyclic hydrocarbons

Low-temperature pyrolytic decomposition of xylene, benzene, toluene, and naphthalene was investigated as a low-cost method for synthesis of a large quantity of perfectly shaped pure carbon spheres. The reaction occurred in a closed iron container at temperatures in the range of 500–700 °C and under pressure of 20 MPa. Some of the experiments were carried out in the presence of distilled water in vapor state near to its critical point, under which conditions it reacted as a very strong oxidant. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD) analysis were used to investigate the properties of the material obtained. The results demonstrated that synthesis had proceeded in the following sequence: vaporization of hydrocarbon, hydrocarbon transformation to condensing drops of heavy hydrocarbons, then drop growth accompanied by continuous alteration of the heavy carbon compounds until their final carbonization. Synthesis in a closed space stimulated particle growth, and particle diameters reached 1 to 12 μm. Continuous condensation of vapor onto the resulting drops caused agglomeration of some of the spheres to form pearl-necklace-like chains when the spheres docked to one another in the course of growth. Carbon atoms in the spheres were arranged in concentric, incompletely closed graphitic shells, which made them stable up to 600 °C in air. Above this temperature, rapid sphere degeneration occurred. Oxygen reacted with carbon atoms situated at the shell edges during heating in air, with some remaining in the spheres; oxygen penetration increased with treatment temperature.

ChemInform Abstract: Chemisorption and Thermal Decomposition of Benzene on Pd(110): High- Resolution Electron Energy Loss Spectroscopy, Low-Energy Electron Diffraction, and Thermal Desorption Studies.

The adsorbed state of benzene on Pd(110) at 300 K and its thermal decomposition process in the temperature region up to 700 K have been investigated by using high-resolution electron energy loss spectroscopy, low-energy electron diffraction, and multiplexed thermal desorption spectroscopy. Vibrational spectra show the existence of two adsorbed states of benzene on Pd(110) at 300 K. In one state, benzene is adsorbed with its C ring nearly parallel to the surface (flat benzene), and in the other state, at some angle (tilted benzene). The tilted benzene is located in the c(4{times}2) domains. For a small exposure ({approx lt}0.3 langmuir; fractional coverage {theta}{sub C{sub 6}H{sub 6}}{approx lt}0.07), the flat benzene predominates. With increasing exposure, conversion from flat to tilted benzene occurs, and the amount of tilted benzene is increased relative to that of flat benzene. For the saturation exposure (3 langmuirs: {theta}{sub C{sub 6}H{sub 6}} {approximately} 0.27), the tilted benzene predominates; the flat benzene also exists. Thermal decomposition of benzene on Pd(110) has been studied in detail. For a small exposure (0.3 langmuir), heating to 380-600 K forms the C{sub x}H{sub y}(x {ge} 1, y = 0,1) species as the decomposition products. By heating the sample to 600 K, theymore » find only C adatoms exist on Pd(110). For the saturation exposure (3 langmuirs), by heating the sample to 400 K, they find the C(4{times}2) structure is well developed and the Pd(110) surface is mostly covered by tilted benzene. Heating to 400-650 K forms the C{sub x}H{sub y} (x = 1 or {ge} 3, y = 0,1) species. The decomposition temperature is shifted toward higher temperatures by the site-blocking effect of benzene admolecules themselves. The decomposition is accompanied by h{sub 2} desorption.« less

The equation of state and nonmetal–metal transition of benzene under shock compression

We employ quantum molecular dynamic simulations to investigate the behavior of benzene under shock conditions. The principal Hugoniot derived from the equation of state is determined. We compare our first principles results with available experimental data and provide predictions of chemical reactions for shocked benzene. The decomposition of benzene is found under the pressure of 11 GPa. The nonmetal–metal transition, which is associated with the rapid C–H bond breaking and the formation of atomic and molecular hydrogen, occurs under the pressure around 50 GPa. Additionally, optical properties are also studied.

Biodegradation of benzene by pure and mixed cultures of Bacillus spp.

Benzene has a wide range of industrial applications, but it is also a major source of environmental pollution. The most eco-friendly/cost-effective method of remediation is biodegradation. In the present study, we used a variety of microbial strains in different combinations on a selection of substrate concentrations to determine the most effective degradation processes. Bacterial strains of pure culture (L4, N3, and N6) were isolated from oil sludge in both Luria–Bertani buffer (LB) and nutrient broth media, and identified by 16S-rRNA analysis (≥98% similarity). The degradation experiments were performed using different combinations of bacterial strains (L4, N3, N6, L4 + N3, L4 + N6, N3 + N6, and L4 + N3 + N6) in modified carbon-free media with different concentrations of benzene as a carbon source (60, 100, and 160 mg l−1) at 30 °C. The isolates of L4 (Acc no: FJ686821), N3 (FJ686825) and N6 (FJ868628) were identified as Bacillus spp. using 16S-rRNA gene sequence analysis. All combinations of isolates have the capacity to degrade benzene. However, the L4 + N3 combination was more efficient than the other mixed or single cultures. In the presence of N6 isolate, the degradation rate of benzene decreased, possibly due to inter- and/or intra species interaction amongst the bacteria. The kinetic parameters ‘Km’ of the Lineweaver–Burk regressions conducted as part of this experiment showed that the lower the level of Km was, the better the biodegradation achieved. The results of this study showed that the use of Bacillus strains in benzene decomposition is feasible. In addition, different strain combinations exhibited different degradation patterns, which are attributed to the most efficient mixed cultures of Bacillus spp.

Molecular Recognitive Photocatalysis Driven by the Selective Adsorption on Layered Titanates

The composition of layered alkali titanates (M(x)Ti(2-x/3)Li(x/3)O(4); M = K(+), Li(+), Na(+)) was tuned to control the swelling of the titanates in water and subsequently achieve molecular-sieve-like molecular recognitive photocatalytic decomposition of aqueous organic compounds on the titanates. Layered potassium lithium titanates with different layer charge density, K(x)Ti(2-x/3)Li(x/3)O(4) (x = 0.61, 0.67, and 0.74), was first synthesized and then the interlayer K(+) was quantitatively exchanged with Li(+) and Na(+) to form Li(x)Ti(2-x/3)Li(x/3)O(4) (x = 0.61, 0.67, and 0.76) and Na(x)Ti(2-x/3)Li(x/3)O(4) (x = 0.61, 0.67, and 0.76). The water adsorption/desorption isotherms and X-ray diffraction patterns of the titanates revealed that the pristine K(+)-type titanates hardly hydrated, while the Li(+)- and Na(+)-exchanged titanates expanded the interlayer space upon the hydration and the degree in the hydration was larger for the Na forms than for the Li ones and depended on the layer charge density. The present titanates were found to selectively adsorb benzene from an aqueous mixture of benzene, phenol, and 4-butylphenol and subsequently decompose benzene upon UV irradiation. The efficiency of the molecular recognitive photocatalytic benzene decomposition was related to the degree in the swelling of the titanates in water.

Highly stable Fe–Ni alloy nanoparticles encapsulated in carbon nanotubes: Synthesis, structure and magnetic properties

Highly stable Fe–Ni alloy nanoparticles encapsulated in carbon nanotubes have been synthesized by in situ catalytic decomposition of benzene over Fe–Ni alloy nanoparticles generated through procedures of sol–gel fabrication and hydrogen reduction. The phases of graphite and γ-FeNi solid solution (face centered cubic) were identified by X-ray diffraction. The results of FE-SEM and HRTEM characterization revealed that Fe–Ni nanoparticles encapsulated in carbon nanotubes are generated in large quantity. The composites are highly stable in air and show soft magnetic property, with saturation magnetization affected by the composition of Fe–Ni alloy and the temperature of benzene decomposition.

Sr0.4H1.2Nb2O6·H2O nanopolyhedra: An efficient photocatalyst

A photocatalyst Sr(0.4)H(1.2)Nb(2)O(6)·H(2)O (HSN) nanopolyhedra with high surface area has been successfully prepared by a simple hydrothermal method. The as-prepared samples were characterized by XRD, BET, SEM, TEM and XPS. The electronic structure of HSN determined by DFT calculations and electrochemical measurement revealed that HSN is an indirect-bandgap and n-type semiconductor, respectively. HSN samples showed high photocatalytic activities for both pure water splitting and the decomposition of benzene. The rate of H(2) evolution over HSN was 15 times higher than that of P25 and the conversion ratio of benzene exceeded twice that of P25. The photocatalytic activities for water splitting can be greatly improved by loading various co-catalysts on HSN, such as Au, Pt, and Pd. The photocatalytic mechanisms were proposed based on the band structure and characterization results of the photocatalyst.

Enhanced photocatalytic activity of quantum-confined tungsten trioxide nanoparticles in mesoporous silica

Due to quantum confinement effects, tungsten trioxide nanoparticles approximately 1.4 nm in diameter prepared in channels of mesoporous silica exhibited a widened bandgap and enhanced photocatalytic performance in the decomposition of benzene.

Preparation, characterization and photocatalytic performance of TiO 2/Ce xZr 1− xO 2 toward the oxidation of gaseous benzene

Increasing environmental pollution caused by the volatile organic compounds due to their toxicity makes their removal imperative. So it is crucial to develop processes which can degrade these compounds effectively. The paper demonstrates that the photocatalytic activity of TiO 2 toward the decomposition of gaseous benzene in a batch reactor can be greatly enhanced by loading TiO 2 onto the surface of Ce x Zr 1− x O 2 ( x ≥ 0.25) using sol–gel technology. This research investigated the relationship between x amount and the photocatalytic activity of TiO 2. The prepared photocatalysts were characterized by BET, XRD, UV–vis diffuse reflectance and XPS analyses. The specific surface area of photocatalyst decreases as x decreases. XRD results reveal the no peaks of titania were detected. Among the five catalysts prepared, only the binding energy values of Ti2p 3/2 of TiO 2/Ce 0.5Zr 0.5O 2 shift toward lower value. The order of photocatalytic activity is TiO 2/Ce 0.5Zr 0.5O 2 > TiO 2/Ce 0.75Zr 0.25O 2 > TiO 2/CeO 2 ≈ TiO 2/Ce 0.25Zr 0.75O 2 > TiO 2/ZrO 2 ≈ TiO 2. The mechanism role of Ceria–Zirconia mixed oxides in photocatalytic reaction was speculated.

Lowering of photocatalytic activity of TiO2 particles during oxidative decomposition of benzene in aerated liquid

TiO2-photocatalyzed reaction was conducted in pure benzene in which TiO2 particles were suspended. Benzene was oxidatively decomposed into CO2, as most of organic compounds. However, the rate of CO2 evolution from benzene was gradually lowered as the reaction continued, which was in contrast to the cases of other non-aromatic organic compounds, such as alcohols or acids. To clarify the reason for the decrease in activity of TiO2, intermediates produced in the solution phase and on the surface of TiO2 were analyzed using chemical and physical techniques. Several kinds of intermediates were identified: phenolic compounds, aldehydes, carboxylic acids, and polymeric substance. Of these products, catechol and polymeric substance, which were observed only on the surface of TiO2 powder, were found to be responsible for the lowering of the photocatalytic activity of TiO2.

Synthesis and Properties of Magnetic Composites of Carbon Nanotubes/Fe Nanoparticle

Magnetic composites of carbon nanotubes (CNTs) are synthesized by the in situ catalytic decomposition of benzene at temperatures as low as 400°C over Fe nanoparticles (mean grain size = 26 nm) produced by sol-gel fabrication and hydrogen reduction. The yield of CNT composite is up to about 3025% in a run of 6 h. FESEM and HRTEM investigations reveal that one-dimensional carbon species are produced in a large quantity. A relatively high value of magnetization is observed for the composite due to the encapsulation of ferromagnetic Fe3C and/or α-Fe. The method is suitable for the mass-production of CNT composites that contain magnetic nanoparticles.

IR laser-induced metal ablation and dielectric breakdown in benzene

IR laser-induced irradiation of Co and Ni sheets leads to metal ablation and when carried out in gaseous benzene (1–10 Torr) to dielectric breakdown which is accompanied by metal plasma and deposition of nanostructured carbon. The metal plasma (metal atoms and ions) as well as transients of benzene decomposition (neutral and ionic carbon and C 2 species) were detected by optical emission spectra. Different features of carbon deposited at benzene pressure 5–10 Torr on a distant glass and on the irradiated metal sheets were revealed by FTIR, Auger and Raman spectroscopy and electron microscopy and explained by surface assisted carbonization. The reported process suggests a novel approach to gas-phase carbonization of organic molecules.

Photocatalytic Decomposition of Benzene by Porous Nanocrystalline ZnGa2O4 with a High Surface Area

Porous nanocrystalline ZnGa2O4 catalysts were synthesized by a simple soft-chemical method at low temperature. The catalysts were characterized by XRD, nitrogen adsorption, SEM, TEM, UV/ vis, and FT-IR spectroscopy. The activity of the photocatalysts was evaluated by decomposition of benzene and its derivatives in the gas phase. It was found that hydrothermal treatment resulted in the formation of spinel ZnGa2O4 with a large surface area of 43-201 m2 x g(-1) depending on the synthetic temperature. The optimum synthetic temperature was found to be 80 degrees C, at which the sample possessed a surface area of 201 m2 x g(-1) and had the highest photocatalytic activity for degrading benzene. A comparison with TiO2 and Pt/TiO2 showed that the ZnGa2O4 (synthesized at 80 degrees C) had improved photocatalytic activity and durability over the TiO2-based catalysts. No remarkable deactivation of the ZnGa2O4 catalyst was observed in 80 h photoreaction, whereas the TiO2 deactivated remarkably in 24 h reaction. The high photocatalytic performance of porous ZnGa2O4 catalysts can be explained by the large specific surface area, the accessible porous framework, and the high redox power.