Abstract
It was proved that atmospheric non-equilibrium plasma can be deemed as “reaction carrier”, and is an effective method of partial oxidation of methane to methanol and other higher hydrocarbons. In this paper, hydrogen peroxide vapor is selected as oxygen-containing oxidizer and used to activate and convert methane into methanol in an atmospheric dielectric barrier discharge. A detailed axisymmetric 2D fluid model in CH4/H2O/H2O2 gas mixture is developed, with an emphasis on gas-phase plasma chemistry for partial oxidation of methane and methanol formation. Especially, the effect of hydrogen peroxide concentration on the conversion of methane to methanol is studied. The spatial and temporal distributions of various plasma species are shown as a function of hydrogen peroxide concentration. In addition, the main plasma species and reaction pathways governing the production and loss of CH3OH and OH are determined. It is shown that the increasing hydrogen peroxide concentration results in increase of OH and CH3OH production. Hydroxyl appears to play a significant role during the process of methanol synthesis, which is primarily produced by electron-impact dissociation of H2O2 and H2O molecules.
Highlights
Atmospheric dielectric barrier discharges (ADBDs) as a source of non-equilibrium low temperature plasma, have attracted increasing interests due to its great potential for practical applications, including surface modification,[1,2] thin film deposition,[3,4] plasma medicine,[5,6,7,8] plasmaassisted combustion ignition.[9,10] atmospheric dielectric barrier discharges (ADBDs) is a promising method in producing the homogeneous room temperature plasma, while the electrons are fast energetic with a typical temperature of 1-10 eV.[11]
Basic streamer discharge parameters It has been demonstrated that the energetic electrons and reactive species generated by ADBD, are crucial to the physical and chemical reaction process
Key plasma species and chemical pathways governing the CH3OH and OH production and loss in a thin methane-hydrogen peroxide vapor mixture at atmospheric pressure are reported for the needle-to-plate electrode geometry
Summary
Atmospheric dielectric barrier discharges (ADBDs) as a source of non-equilibrium low temperature plasma, have attracted increasing interests due to its great potential for practical applications, including surface modification,[1,2] thin film deposition,[3,4] plasma medicine,[5,6,7,8] plasmaassisted combustion ignition.[9,10] ADBD is a promising method in producing the homogeneous room temperature plasma, while the electrons are fast energetic with a typical temperature of 1-10 eV.[11]. Conventional catalytic method requires a nickel base catalyst and high reaction pressure and temperature (>800 ◦C).[14] And, the conversion of reactants and selectivity towards the targeted products need to be improved in atmospheric pressure non-equilibrium plasma process. The catalytic effect of the electrode surface is studied in an ADBD of CO2 and CH4, which suggests the occurrence of CO2 hydrogenation reactions on the metal (copper and nickel) surface.[22] Non-catalytic conversion of CH4 and NO2 into methanol in ADBD was presented, and high yield production of methanol was obtained (18-20% mol) with maximum selectivity of 32% mol.[23] the drawback with this oxidizer is that it involves the manipulation of highly toxic gases (HCN and N2O). The focus of this paper is to numerically study the effect of hydrogen peroxide at low concentrations on the conversion process of methane to methanol in ADBD. A better insight into the role played by OH radicals in the formation of CH3OH would be of great value
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