Methane Decomposition in a Barium Titanate Packed-Bed Nonthermal Plasma Reactor

The behavior of lattice oxygen species of the ferroelectric material during methane oxidation was investigated using a nonthermal plasma reactor packed with BaTiO ₃ pellets. Lattice oxygen species in BaTiO ₃ play an important role in the formation of N ₂ O and the oxidation of CH ₄ . The oxidation products such as CO and CO ₂ were formed from independent reaction pathways. Lattice oxygen species were able to preferentially oxidize the carbon species deposited on the pellet surface into CO. Also, N ₂ O and NO _x were independently formed in the N ₂–O ₂ reaction, suggesting that different oxygen species give N ₂ O and NO _x. N ₂ O was produced by the oxidation of molecular nitrogen with lattice oxygen species.     

Gas-Phase Removal of Acetaldehyde via Packed-Bed Dielectric Barrier Discharge Reactor

The effectiveness of applying packed-bed dielectric barrier discharge(PBDBD) technology for removing acetaldehyde from gas streams wasinvestigated. Operating parameters examined in this study include appliedvoltage, oxygen content, and gas-flow rate. Experimental results indicatethat the destruction efficiency of acetaldehyde predominantly depends onthe applied voltage. Removal of 99% of acetaldehyde has been achieved forgas streams containing 1000 ppmv acetaldehyde, 5% oxygen, with nitrogen asthe carrier gas. The oxygen content in the gas stream plays an importantrole in removing acetaldehyde within PBDBD. A higher CH3CHO removalefficiency is achieved for the gas stream containing less oxygen, since itwill dissipate energy due to its electronegative property. Carbon dioxideis the major end product, which is less hazardous to the environment and tohuman health. However, undesirable products, e.g., NO₂ and N₂O,CH₃OC₂H₅, CH₃COOH, CH₃NO₂,HCN, CH₃NO₃, and CH₃OH, are detected as well.     

By-Products NOx Control and Performance Improvement of a Packed-Bed Nonthermal Plasma Reactor

NO_x are main toxic by-products in the effluent gas whendecomposing volatile organic compounds in air by a packed-bed plasmareactor. Several types of materials such as 13X zeolite, BaTiO₃and Pd/Pt catalysts have been selected to be packed in the reactor, andmethane decomposition and NOx by-products in discharged gases areinvestigated at different range of reaction temperature and dischargeenergy density at atmospheric pressure. The ratios of methane decompositionpercentage/NO_x concentration are used to assess these packed bedmaterials and reaction conditions. The results show that usingPd/-Al₂O₃ with lower percentage Pd as packedbed, and discharging with lower discharge density at higher reactiontemperature can reduce NO_x output effectively and greatly improveperformance of the reactor.     

The Chemistry of Gaseous Dodecane Degradation in a BaTiO3 Packed-Bed Plasma Reactor

Plasma Chemistry and Plasma Processing - The plasma decomposition of gaseous dodecane has been investigated in a non-thermal BaTiO3 packed-bed plasma reactor in the atmospheric pressure streams of...     

Experimental Study of CO2 Decomposition in a DC Micro-slit Sustained Glow Discharge Reactor

Plasma Chemistry and Plasma Processing - Carbon dioxide decomposition in a micro-slit sustained glow discharge reactor operated at low pressure of 8 Torr was studied experimentally. A...     

Humidity Effect on Toluene Decomposition in a Wire-plate Dielectric Barrier Discharge Reactor

Laboratory-scale experiments were performed to evaluate the humidity effect on toluene decomposition by using a wire-plate dielectric barrier discharge (DBD) reactor at room temperature and atmospheric pressure. The toluene decomposition efficiency as well as the carbon dioxide selectivity with/without water in a gas stream of N₂ with 5% O₂ was investigated. Under the optimal humidity of 0.2% the characteristics of toluene decomposition in various background gas, including air, N₂ with 500 ppm O₂, and N₂ with 5% O₂ were observed. In addition, the influence of a catalyst on the decomposition was studied at selected humidities. It was found that the optimum toluene removal efficiency was achieved by the gas stream containing 0.2% H₂O, since the presence of water enhanced the CO₂ selectivity. In addition, the toluene removal efficiency increased significantly in a dry gas stream but decreased with an increase in the humidity when the Co₃O₄/Al₂O₃/nickel foam catalyst was introduced into the discharge area.     

Decomposition of Heptane by Dielectric Barrier Discharge (DBD) Plasma Reactor Having the Segmented Electrode: Comparison of Decomposition Mechanisms to Toluene

Plasma Chemistry and Plasma Processing - The effect of the structure of VOC and the exposed surface area on the decomposition of VOCs adsorbed on the zeolite by dielectric barrier discharge plasma...     

Decomposition of Benzene in Air in a Plasma Reactor: Effect of Reactor Type and Operating Conditions

The decomposition of benzene was carried out in two types of plasma reactors packed with BaTiO₃ pellets: one reactor had two stainless steel electrodes (SUS reactor), and the other reactor had a glass layer between two concentric electrodes (GL reactor). The decomposition efficiency and the suppression of formation of N₂O and NO_x were greater in the GL reactor than in the SUS reactor. In contrast, the suppression of O₃ formation and the oxidation to CO_x in the SUS reactor were superior to those in the GL reactor. The effect of wa eform and frequency of applied ac power was in estigated for each reactor.     

Photochemical Removal of Gaseous Elemental Mercury in a Dielectric Barrier Discharge Plasma Reactor

The plasma process has the potential to serve as a low cost mercury oxidation technology that will facilitate elemental mercury removal in a downstream of Flue Gas Desulfurization system. The performance of the main gas constituents, such as H₂O, O₂ and HCl on elemental mercury oxidation under plasma atmosphere was investigated in simulated flue gas. Experiments were carried out in a dielectric barrier discharge reactor operated at 140?°C. Photochemical effects of nanocrystalline titania on oxidation of elemental mercury were also tested. The results indicated that both H₂O and O₂ promote the oxidation of elemental mercury significantly. Active radicals generated by ionization, such as O, O₂ and OH, play the crucial roles in oxidation process. The presence of HCl in N2/O2 stream in plasma system is a very effective way of oxidizing elemental mercury, the nearly complete oxidation of elemental mercury was observed by 4?kV of applied voltage only. The best photocatalytic activity of anatase TiO₂ which was calcined at 600?°C was found in our tests. Compared with the plasma process alone, the oxidation efficiency increased 18.7?C26.3?% with the addition of photocatalyst.     

Effect of Water Vapor on Benzene Decomposition Using a Nonthermal-Discharge Plasma Reactor

The effect of water vapor on benzene decomposition in air was investigatedusing a nonthermal-discharge plasma reactor packed with ferroelectricmaterials. The conversion of benzene was found to decrease with an increaseof water concentration. On the other hand, the selectivity to CO₂ in thedecomposition products increased with an increase of water concentration. Acomparison between the benzene conversion to CO and CO₂ suggested that COformation was suppressed by water to a greater extent than was CO₂formation. N₂O formation also decreased with an increase of waterconcentration. These results suggest that the activity of oxygen speciesresponsible for the formation of CO and N₂O is reduced by water.     

Hydrogen Production from Methane Decomposition Using a Mobile and Elongating Arc Plasma Reactor

Plasma Chemistry and Plasma Processing - Hydrogen and solid carbon were produced through methane decomposition in a plasma reactor with a parallel set of screw type helix and rod-like electrodes....     

Plasma Assisted Catalytic Conversion of CO2 and H2O Over Ni/Al2O3 in a DBD Reactor

Plasma Chemistry and Plasma Processing - We present an innovative approach for reacting carbon dioxide and water to give syngas by combining heterogeneous catalysis and non-thermal plasma...     

Investigation of CO2 Splitting Process Under Atmospheric Pressure Using Multi-electrode Cylindrical DBD Plasma Reactor

Plasma Chemistry and Plasma Processing - In this paper, the CO2 splitting process was performed under atmospheric pressure in a multi-electrode cylindrical dielectric barrier discharge (DBD) plasma...     

Oxidation of Elemental Mercury by Active Species Generated From a Surface Dielectric Barrier Discharge Plasma Reactor

A surface dielectric barrier discharge plasma reactor was employed to study Hg⁰ oxidation in coal-fired flue gas. The experimental results showed that 98 % of Hg⁰ oxidation efficiency and 13.7 μg kJ^?1 of energy yield were obtained under a specific energy density (SED) of 7.9 J L^?1. Increasing SED was beneficial for Hg⁰ oxidation due to higher production of active species. Higher initial concentration resulted in lower Hg⁰ oxidation efficiency, but higher amount of Hg⁰ oxidation. Water vapor inhibited Hg⁰ oxidation because the generation of O₃ was suppressed. The presence of NO remarkably restrained Hg⁰ oxidation, while SO₂ showed little effect on Hg⁰ oxidation. Roles of active species in Hg⁰ oxidation were examined under different gas atmospheres (O₂ and air), indicating that O₃ played an important role in Hg⁰ oxidation. Deposits on the internal surface of the reactor were analyzed by energy dispersive spectroscopy and the product was identified as HgO.     

Aerobic Biodegradation of a Sulfonated Phenylazonaphthol Dye by a Bacterial Community Immobilized in a Multistage Packed-Bed BAC Reactor

A microbial community able to aerobically degrade the azo dye Acid Orange 7 was selected from riparian or lacustrine sediments collected at sites receiving textile wastewaters. Three bacterial strains, pertaining to the genera Pseudomonas, Arthrobacter, and Rhizobium, constitute the selected community. The biodegradation of AO7 was carried out in batch-suspended cell culture and in a continuously operated multistage packed-bed BAC reactor. The rapid decolorization observed in batch culture, joined to a delay of about 24 h in COD removal and cell growth, suggests that enzymes involved in biodegradation of the aromatic amines generated after AO7 azo-bond cleavage (1-amino-2-naphthol [1-A2N] and 4-aminobenzenesulfonic acid [4-ABS]), are inducible in this microbial consortium. After this presumptive induction period, the accumulated byproducts, measured through COD, were partially metabolized and transformed in cell mass. At all azo dye loading rates used, complete removal of AO7 and 1-A2N was obtained in the multistage packed-bed BAC reactor (PBR).; however, the overall COD (η _COD ) and 4-ABS (η _ABS ) removal efficiencies obtained in steady state continuous culture were about 90%. Considering the toxicity of 1-A2N, its complete removal has particular relevance. In the first stages of the packed-bed BAC reactor (Fig. 4a–c), major removal was observed. In the last stage, only a slight removal of COD and 4-ABS was obtained. Comparing to several reported studies, the continuously operated multistage packed-bed BAC reactor showed similar or superior results. In addition, the operation of large-packed-bed BAC reactors could be improved by using several shallow BAC bed stages, because the pressure drop caused by bed compaction of a support material constituted by small and fragile particles can be reduced.     

介质阻挡放电等离子体脱除氮氧化物的发射光谱研究

在大气压下, NO/N2体系中, 利用发射光谱技术对50 Hz和5 kHz交流介质阻挡放电等离子体在200～900 nm范围内进行了诊断. 在632、674.5、715.5和742 nm等处测得了N原子的谱线. 利用化学发光法NOx分析仪, 模块式红外吸收气体分析检测仪, 大气压下直连质谱多种检测手段对放电前后的稳定物种进行了分析, 观察到O2的生成. 初步讨论了无氧条件下介质阻挡放电等离子体中NO脱除的反应机制.     

Characterization of ZnO Nanotube Fabricated by the Plasma Decomposition of Zn(OH)2 Via Dielectric Barrier Discharge

Here, we report a new and rapid way to decompose Zn(OH)₂ for the fabrication of ZnO nanotube using dielectric barrier discharge (DBD) plasma initiated at ambient condition. X-ray diffraction, field emission scanning electron microscope and high-resolution transmission electron microscopy were employed to characterize the fabricated ZnO nanotube. The results show that hexagonal hollow tubes in a wurtzite phase are obtained. Compared to the ZnO powder prepared by the thermal calcination, the DBD plasma made ZnO nanotube shows an enhanced performance for H₂S removal at low temperature.     

The CO2 Reforming of Natural Gas in a Silent Discharge Reactor

The conversion of a 1:1 CH ₄ /CO ₂ mixture to H ₂ and CO was shown to occur at ambient temperature in a silent discharge reactor. Conversions of up to 50% were achieved with two reactors in series with a total residence time of 3 min at 13kV and 25 mA.     

Characterization of Polypropylene Surface Treated in a CO2 Plasma

The polypropylene modification in CO₂ plasma mainly contributes to degradation, functionalization, and cross-linking. The degradation, whose rate is depending on CO₂ dissociation and oxygen atom formation, is a quite slow reaction and it is associated with surface topography alteration, especially of the amorphous phase of the polypropylene. The surface roughness increases with the treatment duration and the amorphous phase is more degraded than the crystallized part. The functionalization, corresponding to an increase of the surface energy (57.3 mJ m ^{– 2} in 30 s), and to an oxidation (23 oxygen at.%) with the appearance of alcohol, ketone, and acid functions is a much faster phenomenon. Cross-linking takes also place during this type of treatment and will reinforce the stability of the modified surface.     

Analytical Model of a Plasma Reactor

This paper presents a simple analytical model to estimate the effect of theboundary layer on the performance of a dc plasma reactor. A graphite linerwas inserted inside the reactor to raise the wall temperature. The model wasused to predict the Destruction and Removal Efficiency (DRE) of the reactorwith and without the graphite liner. The DRE of the device was measured forboth conditions and was found to be in close agreement with the predictedvalues. The model has shown that the DRE is a strong function of the walltemperature of the flight tube and is insensitive to the change in thetube's diameter.