The Pyrolysis Property of a Pulsed Plasma of Methane

This study examined the discharge property of methane in a pulsed plasma using single and sequential pulse modes. A pulsed corona discharge occurred, followed by a pulsed spark discharge. An equivalent single channel model (ESC model) for the pulsed plasma of methane was established. The maximum temperature of methane in the discharge channel was estimated. The pyrolysis property of the channel methane was estimated from Senkin simulation and single channel discharge experiment.     

Methane Conversion to Hydrogen and Higher Hydrocarbons by Double Pulsed Glow Discharge

Pulsed atmospheric glow plasma, sustained by corona discharge, was utilized to convert methane. Analysis by gas chromatography showed that hydrogen and C₂-products are the main constituents of outlet mixture while C₂₊-products with small concentrations were also detected. The chemical energy efficiency turned out to be about 9% for the best result obtained by this type of reactor. It has been shown that more improvement of energy efficiency is possible by increasing the pulse repetition rate.     

Plasma Thermal Conversion of Methane to Acetylene

This paper describes a re-examination of a known process for the direct plasma thermal conversion of methane to acetylene. Conversion efficiencies (% methane converted) approached 100% and acetylene yields in the 90–95% range with 2–4% solid carbon production were demonstrated. Specificity for acetylene was higher than in prior work. Improvements in conversion efficiency, yield, and specificity were due primarily to improved injector design and reactant mixing, and minimization of temperature gradients and cold boundary layers. At the 60-kilowatt scale cooling by wall heat transfer appears to be sufficient to quench the product stream and prevent further reaction of acetylene resulting in the formation of heavier hydrocarbon products or solid carbon. Significantly increasing the quenching rate by aerodynamic expansion of the products through a converging–diverging nozzle led to a reduction in the yield of ethylene but had little effect on the yield of other hydrocarbon products. While greater product selectivity for acetylene has been demonstrated, the specific energy consumption per unit mass of acetylene produced was not improved upon. A kinetic model that includes the reaction mechanisms resulting in the formation of acetylene and heavier hydrocarbons, through benzene, is described.     

滑动弧电极放电等离子体作用甲烷制C2烃的工艺

采用刀片式不锈钢电极放电反应器,以Ar气为稀释气,研究了等离子体作用下甲烷转化制C2烃的工艺条件。考察了CH4流量、高频电源输入电压和电极间距等参数对甲烷转化率、C2烃选择性、收率和反应表观能耗的影响。结果表明,增加CH4流量,表观能耗随之降低;当输入电压和电极间距较小时,甲烷转化率随输入电压和电极间距的增大而增大,但输入电压和电极间距过大时,C2烃收率明显下降,积碳严重。在CH4流量14 mL/min、Ar气流量60 mL/min、高频电源输入电压22 V、电流0.44 A、电极间距4 mm的优化条件下,甲烷最高转化率为43.1%,C2烃收率、选择性和表观能耗分别为40.1%、93.2%和2.41 MJ/mol。C2烃中不饱和烃的体积分数可达95%以上。     

Kinetic Modeling of Plasma Methane Conversion Using Gliding Arc

Plasma methane (CH4) conversion in gliding arc discharge was examined. The result data of experiments regarding the performance of gliding arc discharge were presented in this paper. A simulation which is consisted some chemical kinetic mechanisms has been provided to analyze and describe the plasma process. The effect of total gas flow rate and input frequency refers to power consumption have been studied to evaluate the performance of gliding arc plasma system and the reaction mechanism of decomposition.Experiment results indicated that the maximum conversion of CH4 reached 50% at the total gas flow rate of 1 L/min. The plasma reaction was occurred at the atmospheric pressure and the main products were C (solid), hydrogen, and acetylene (C2H2). The plasma reaction of methane conversion was exothermic reaction which increased the product stream temperature around 30～50℃.     

Conversion of Methane to C2 Hydrocarbons via Cold Plasma Reaction

Direct conversion of methane to C2 hydrocarbons via cold plasma reaction with catalysts has been studied at room temperature and atmospheric pressure. Methane can be converted into C2 hydrocarbons in different selectivity depending on the form of the reactor, power of plasma, flow rate of methane, ratio of N2/CH4 and nature of the catalysts. The selectivity to C2 hydrocarbons can reach as high as 98.64%, and the conversion of methane as high as 60% and the yield of C2 hydrocarbons as high as 50% are obtained. Coking can be minimized under the conditions of: proper selection of the catalysts, appropriate high flow rate of inlet methane and suitable ratio of N2 to CH4. The catalyst surface provides active sites for radical recombination.     

冷等离子体作用下CH_4-CO_2转化制合成气

在常温常压条件下 ,利用电晕放电 ,使 CH4 - CO2 混合气转化生成合成气 .结果表明 ,该过程中 CH4 和 CO2 的转化率与反应体系能量密度、原料气配比和流速等有关 .在 0 .1MPa气压 ,能量密度为 10 50 k J/ mol(反应体系温度低于 50 0 K) ,n( CH4 )∶ n( CO2 ) =1∶ 2条件下 CH4 和 CO2 的转化率分别超过 60 %和 50 % ,超出了热力学平衡转化率的限制 .通过调配原料的配比 ,可以得到不同 n( H2 ) / n( CO)比值的产物 .对该体系的反应机理进行了探讨 .     

Pulsed Plasma Polymerisation of Butylacrylate for Pressure-Sensitive Adhesion

Pulsed plasma polymerisation of butylacrylate monomer is found to lead to the deposition of polymeric films which are structurally very similar to conventional poly(butylacrylate). Carbon dioxide or oxygen plasma post treatment of these surfaces significantly improves their adhesive performance due to greater Lewis acid-base interactions at the interface.     

Direct Non-oxidative Methane Conversion by Non-thermal Plasma: Experimental Study

The direct non-oxidative conversion of methane to higher hydrocarbons in non-thermal plasma, namely dielectric barrier discharge and corona discharge, has been investigated experimentally at atmospheric pressure. In dielectric barrier discharge, the methane is mainly converted to ethane and propane with small amounts of unsaturated and higher hydrocarbons. While in corona discharge, methane was activated mainly to acetylene with small amount of other higher hydrocarbons. Decreasing the gas flow or increasing power input will improve the methane conversion and product yields. It is found that the methane conversion and main product yield against the input specific energy were special functions in both dielectric barrier discharge and corona discharge, independent of the reactor size, and whether fixing flow rate or power input and changing the power input or flow rate. The corona discharge is a promising alternative method for methane conversion to produce acetylene and hydrogen at low temperature.     

甲烷氧化制合成气两段反应新工艺

Interest in conversion of natural gas to liquid hydrocarbons (GTL) by Fischer-Tropsch synthesis has grown significantly over the last decade. Most research and development work has focused on syngas production step, which accounts for more than 50% of the total investment. Reducing the cost of syngas production would have great beneficial effects on GTL process. Catalytic partial oxidation of methane (CPOM) to syngas is a slightly exothermic, highly selective, and energy efficient process. It gives syngas with n(H2)/n(CO)=2, directly suitable for F-T synthesis. However, CPOM process has not yet been used commercially. The major engineering problems are the high temperature gradient and the risk of explosion with premixed CH4-O2 mixture, which is within the ignition and explosion limit. In fluidized-bed reactors, the heat transfer is much better, which ensures a more uniform temperature and safer operation. A technology for syngas production by contacting CH4 with limited amount of steam and O2 in a fluidized-bed reactor has been developed[1].     

Direct Non-oxidative Methane Conversion by Non-thermal Plasma: Modeling Study

The direct non-oxidative conversion of methane to higher hydrocarbons in dielectric barrier discharges has been investigated theoretically at atmospheric pressure. Preliminary modeling of the results is presented, based on a well-stirred reactor model to determine the spatially and time-averaged species composition through the solution of balance equations for species, mass, gas and electron energy. The results show good quantitative agreement between model predications and experimental measurements by considering the glow and after-glow regions. Moreover, the model has predicted that there exists a transition where the main product of ethane will transform to acetylene by increasing the specific energy. The dominant reaction paths and the possibility of selective to C₂ hydrocarbons have been discussed. A list of gas-phase reactions has been compiled for modeling methane conversion in non-thermal plasma and can be employed in more sophisticated two- or three-dimensional plasma simulations.     

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.     

膜反应器中的甲烷转化反应

用ＥＤＴＡ－柠檬酸联合络合法合成了Ｂａ０．５Ｓｒ０．５Ｃｏ０．８Ｆｅ０．２Ｏ３－δ混合导体透氧膜材料,并考察了膜片本身对甲烷的活化性能,结果表明,导体膜对甲烷氧化偶联（ＯＣＭ）反应具有催化活性,研究了膜反应器中甲烷部分氧化（ＰＯＭ）制合成气反应,发现在开始阶段甲烷转化率有两次快速升高,第一次是由于甲烷与二氧化碳重整而产生的;第二次是由于透氧量增加而导致的,透氧量随温度的升高而增加,８５０℃时甲烷转     

Conversion of Methane to Hydrogen via Pulsed Corona Discharge

Experiments are performed to develop a pulsed corona discharge system for the conversion ofmethane to hydrogen at atmospheric pressure (≌760 Torr) without using a catalyst. The corona dischargewas energized by 10-12 μs wide voltage pulses (≤7 kV) at a repetition rate of about 1.0-1.5 kHz. Theresidual gases were characterized by mass spectrometry. The conversion of methane is as high as 50.8% producing the 70% yield of hydrogen. The influences of argon on the discharge of methane were studied.This result could be useful for the mass production of hydrogen in both academic and industrial point ofview.     

The Design Optimization of a Plasma Reactor for Chemical Waste Destruction

The heat flux and destruction and removal efficiency (DRE) measurements have been made on 100, 150 and 200 mm diameter plasma reactors to optimize the performance. The DRE was measured for pressure and gas atomization techniques of waste injection using both argon and CO₂ gases. As a result, the design of the reactor was optimized and the waste throughput was increased by ~17% with improved destruction performance. The 150 mm diameter reactor was found to perform better using gas atomization of feed injection using carbon dioxide at the given power and waste feed rate.     

常压辉光放电等离子体转化CH4制C2烃的研究

采用新型的旋转电极辉光放电反应器, 在常温常压下对辉光等离子体作用下的甲烷转化制C₂烃进行了研究. 在氢气共存条件下, 考察了反应器电极的结构、材料, 输入电场峰值电压和反应物流率等参数对甲烷转化率和C₂烃单程收率及其选择性的影响规律, 同时比较了不同反应器的能量效率. 结果表明: 在本实验条件下, 金属铜材料好于不锈钢, 螺旋形结构优于三排圆盘结构. CH₄转化率和C₂烃选择性和收率均随输入电场峰值电压的升高而增大, 随反应物流量的增加而减小. 从CH₄转化率、C₂烃的收率和选择性的指标来评价这些反应器, 采用旋转螺旋状铜电极反应器时最好, 当反应物流量为60 mL/min时, 甲烷最高转化率为77.31%, 对应的C₂烃收率和选择性分别为75.66%和97.88%; 当能量密度为800 kJ/mol时, 能效最高为13.5%.     

Methane coupling in microwave plasma under atmospheric pressure

Methane coupling in microwave plasma under atmospheric pressure has been investigated.The effects of molar ratio n(CH4)/n(H2),flow rate and microwave power on the reaction have been studied.(1)With the decrease of n(CH4)/n(H2)ratio,methane conversion,C2 hydrocarbon yield,energy yield and space-time yield of acetylene increased,but the yield of carbon deposit decreased.(2)With the increase of microwave power,energy yield of acetylene decreased,but space-time yield of acetylene increased.(3)With the increase of flow rate,energy yield and space-time yield of acetylene increased first and then decreased.Finally,under the reaction conditions of CH4 flow rate of 700 mL/min,n(CH4)/n(H2)ratio of 1/4 and microwave power of 400 W,the energy yield and space-time yield of acetylene could reach 0.337 mmol/kJ and 12.3 mol/(s m3),respectively.The reaction mechanism of methane coupling in microwave plasma has been investigated based on the thermodynamics of chemical reaction.Interestingly,the acetylene yield of methane coupling in microwave plasma was much higher than the maximum thermodynamic yield of acetylene.This phenomenon was tentatively explained from non-expansion work in the microwave plasma system.     

流化床反应器中甲烷部分氧化制合成气

Most previous studies on the partial oxidation of methane (POM) have used either fixed beds or monolith catalysts[1].     

Plasma Treatment of Ni Catalyst for Partial Oxidation of Methane

The 10%Ni/Al2O3 catalyst for partial oxidation of methane was treated by DBD (dielectric barrier discharge) plasma in a continuous system under atmospheric pressure and room temperature by flowing He. It was found that 10%Ni/Al2O3 catalyst treated by plasma presents a higher catalytic activity and an enhanced stability than the catalysts prepared without plasma treatment. The methane conversion over the catalyst treated by plasma is 3%-5% higher than the catalysts untreated by plasma. Moreover,the enhanced dispersion of the catalyst can be achieved by plasma treatment, which can improve the interaction between active species and supports, catalytic activity and the resistance to carbon deposition.     

微波复合直流等离子体转化天然气制乙炔的研究

利用微波复合直流等离子体对天然气转化制乙炔反应进行了研究. 考察了氢烷比、气体流量、功率等参数对装置的能量利用率以及天然气转化反应的影响, 并考核了微波复合直流等离子体转化天然气制乙炔工艺的稳定性. 实验结果表明: 微波复合直流等离子体装置的能量利用率随等离子体工作气体的流量的增加而提高; 由于微波的作用使传统直流柱状等离子体分化为多根丝状等离子体, 从而使得电极的烧蚀方式由传统的点烧蚀变为面烧蚀, 并大幅度提高等离子体转化天然气工艺的稳定性和电极寿命; 甲烷的转化率和乙炔的收率随功率的增加而提高, 随CH₄/H₂比和气体流量的增加而降低, 在氢烷比为0.9、总气体流量为760 L/min、微波源输出电功率6 kW、直流电源输出功率90 kW时, 甲烷转化率可达84.4%, 乙炔选择性为75.6%, 乙炔收率为63.8%, 乙炔能耗达10.8 kWh•kg^－1; 电极寿命超过200 h.