Methane oxidation in a dielectric barrier discharge. the impact of discharge power and discharge gap filling (original) (raw)
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Journal of Natural Gas Chemistry, 2006
The direct conversion of methane using a dielectric barrier discharge has been experimentally studied. Experiments with different values of flow rates and discharge voltages have been performed to investigate the effects on the conversion and reaction products both qualitatively and quantitatively. Experimental results indicate that the maximum conversion of methane has been 80% at an input flow rate of 5 ml/min and a discharge voltage of 4 kV. Experimental results also show that the optimum condition has occurred at a high discharge voltage and higher input flow rate. In terms of product distribution, a higher flow rate or shorter residence time can increase the selectivity for higher hydrocarbons. No hydrocarbon product was detected using the thermal method, except hydrogen and carbon. Increasing selectivity for ethane was found when Pt and Ru catalysts presented in the plasma reaction. Hydrogenation of acetylene in the catalyst surface could have been the reason for this phenomenon as the selectivity for acetylene in the products was decreasing.
Plasma Chemistry and Plasma Processing, 2011
We have studied the production of synthesis gas and other hydrocarbons in a dielectric barrier discharge using mixtures of helium, methane and carbon dioxide. It was found that helium has a significant influence on the discharge, decreasing the breakdown voltage and increasing the rate of conversion of CH4 and CO2. However it also decreases the selectivities and the range of stable operating conditions for the discharge. The main products obtained were H2, CO, C2H6 and C3H8 but traces of other hydrocarbon, carbon deposition and the formation of condensable products were also detected. The rate of conversion and conversion abilities were obtained by fitting the conversion results to a model.
Plasma-assisted partial oxidation of methane to synthesis gas in a dielectric barrier discharge
Applied Catalysis A: General, 2004
The partial oxidation of methane to synthesis gas was investigated in a dielectric barrier discharge (DBD). The effect of gas temperature, frequency of the applied voltage, input energy, total gas flow rate on the reagent conversions and product distribution was determined. The plasma initiates the reaction at low temperatures. Methane and oxygen conversions depend on temperature and the energy input per unit flow. The product selectivities observed are compared with thermal equilibrium calculations. Carbon monoxide and water are the main products of the plasma-assisted methane oxidation in the DBD in the presence of ␣-Al 2 O 3 catalyst support in the discharge zone. When a Ni/␣-Al 2 O 3 catalyst is present in the plasma zone, the interactions between nickel catalyst and plasma result in oxidation of carbon monoxide to carbon dioxide at 300 • C and above, whereas the selectivity to H 2 and H 2 O remains stable.
Plasma Processes and Polymers
Experimental data are used in theoretical models to study the effects of input voltage and gas flow rate on plasma and background gas parameters in a voltage range where the transition from nondischarge to full‐discharge happens. To this end, a specific methane‐fed dielectric barrier discharge is used as a plasma reactor, and electrical modeling, the Boltzmann equation method, and emission spectrum analysis are employed to calculate plasma parameters and gas heating. The output of this study proves that a uniform plasma with a controllable background gas heating is achievable by the adjustment of input parameters such as voltage and gas flow rate in a well‐designed dielectric barrier discharge.
Conversion of CH4 and CO2 to syngas and higher hydrocarbons using dielectric barrier discharge
Korean Journal of Chemical Engineering, 2003
The conversion of methane to syngas and other hydrocarbons in dielectric barrier discharge plasma under the presence of CO 2 was investigated. Effects of the input voltage on the conversion of methane and CO 2 and the ratio of syngas were analyzed experimentally. The results of numerical simulations showed good quantitative agreement with those of experiments.
Plasma Sources Science and Technology, 2011
The conversion of methane to value-added chemicals and fuels is considered to be one of the challenges of the 21st century. In this paper we study, by means of fluid modeling, the conversion of methane to higher hydrocarbons or oxygenates by partial oxidation with CO 2 or O 2 in a dielectric barrier discharge. Sixty-nine different plasma species (electrons, ions, molecules, radicals) are included in the model, as well as a comprehensive set of chemical reactions. The calculation results presented in this paper include the conversion of the reactants and the yields of the reaction products as a function of residence time in the reactor, for different gas mixing ratios. Syngas (i.e. H 2 + CO) and higher hydrocarbons (C 2 H x ) are typically found to be important reaction products.
A Brief Catalyst Study on Direct Methane Conversion Using a Dielectric Barrier Discharge
2007
A series of metal catalysts was used for methane conversion to higher hydrocarbons and hydrogen in a dielectric barrier discharge. The main goal of this study is to identify the metal catalyst components which can influence the reactions in room-temperature plasma conditions. The catalysts supported by g-Al 2 O 3 and zeolite (ZSM 5x) were prepared by the incipient wetness method with solutions containing the metal ions of the second component. Among the catalysts tested, only Pt and Fe catalysts showed a unique result of catalytic reaction in a reactor bed packed with glass beads.
Chemical Engineering Journal, 2012
Non-oxidative conversion of methane into higher hydrocarbons was studied under argon, at atmospheric pressure, in the non-equilibrium environment of the dielectric barrier discharge (DBD). In this study, two concentric dielectric barriers, a short plasma zone with a wide discharge gap have been used to investigate methane conversion in reactors employing alumina and quartz as dielectrics. As energy transfer to the plasma in a DBD system is determined by the capacitive properties of the dielectrics, discharge energy varies between quartz and alumina reactors at the same applied voltage and the conversion of methane and yield of hydrogen therefore also varies between quartz and alumina reactors. Although the dielectric strength of alumina is lower than that of quartz, this disadvantage is offset by increased dielectric permittivity resulting in greater dielectric capacity, in turn leading to increased gap voltage and associated higher conversion rates. Methane conversion was performed in a majority argon carrier. The addition of methane in low concentrations results in a modified argon discharge, one operating in the transition region between homogeneous glow and filamentary discharge regimes. Under these conditions, methane conversion rates were observed to vary with methane concentration, applied voltage and residence time. Experimental results are presented and interpreted in terms of ionization phenomena, metastable species activity and discharge power.
A review of direct methane conversion to methanol by dielectric barrier discharge
IEEE Transactions on Dielectrics and Electrical Insulation, 2008
The topics of conversion and utilization of methane are important issues to tackle global warming. Several technologies including plasma-based process were proposed to improve the process involving the conversion and utilization of methane. The direct conversion of methane to methanol in the presence of energetic species, i.e. ion, radical, electron, and excited molecules, has attracted many experts' attention in recent years. In this review paper, the concepts and the applications of plasma to synthesize methanol from methane are briefly summarized. The recent advancements in direct conversion of methane are discussed as well as the synthesis of methanol from methane and oxygen, methane and carbon dioxide, methane and water, methane and nitrogen oxide by plasma. Various parameters of feed gas ratio, gas flow rate, applied voltage and inert gas on the conversion and reaction selectivity are also discussed but mainly of the methane-oxygen system. . His research focuses on methanol production by nonthermal plasma-chemistry process as well as developing high-quality catalysts for plasma processes.