Methane Conversion Into Light Hydrocarbons With Dielectric Barrier Discharge Microplasma Reactor

Methane is the primary component of natural gas. In recent years, methane hasalso become increasingly relevant in chemistry and industry, both as a hydrogensource and as raw material for producing other complex hydrocarbons. However, themethane conversion is a challenging problem because of the strong bond energy ofC-H in methane. A more favorable alternative is the dielectric barrier dischargemicroplasma technique (micro-DBD), in which the plasma is confined to criticaldimensions below approximately1mm, and the energy density comparatively higher.Additionally, micro-DBD combines the advantages of non-thermal plasma with thoseof micro-reactors, offering better control of processing parameters for the selectivesynthesis of products. In this work, the influence of the reactor configuration andprocess parameters were studied.The conversion of methane could be divided into three stages: an increase stage, astable stage and a decrease stage. The wall temperature of reactor increased fromroom temperature to220℃during the first10min.The process parameters and power parameters in the pure methane system, theCH4/Ar system and the multistage micro-DBD system were investigated. The resultsindicated that a larger input power, a longer residence time and a lower dischargefrequency had a positive effect on the conversion of methane. Nine micro-DBDreactors were investigated for methane conversion. The micro-DBD reactor with asmaller discharge gap would be suitable for methane conversion because of the highenergy efficiency and the high methane conversion rate. The conversion of methanewas high and the selectivity of C was small in the CH4/Ar system. In the multistagemicro-DBD system, due to the longer residence time, the conversion of methanecould be reached40.1%. The addition of catalytic packing could enhance theconversion of CH4and product selectivity as a result of changes in the physicalproperties of the discharge. In the presence of γ-Al2O3and quartz wool, the formationof light hydrocarbons was inhibited due to shape-selectivity determined by catalystspore size, and the selectivity of C2H2+C2H4was improved. The Pd/Al2O3catalyst waseffective, the conversion of methane and C2H6selectivity increased with this catalyst. A simplified global chemical kinetic model according to methane concentrationwas proposed. The chemical kinetic model showed that the conversion of methanewas an exponential function of the plasma energy for a low methane inletconcentration, and was a linear function of the input energy for a high methane inletconcentration. The chemical kinetic in different micro-DBD reactors was inveatigated.The reaults showed that a micro-DBD reactor with smaller discharge gap had highrate of production radicals and high energy efficiency. A nonlinear multipleregression analysis was appropriate for data regression and for the correlation ofsystem variables with both the conversion of methane and product selectivity.