Home – Home – Jornals – Chemistry for Sustainable Development 2019 number 1

Research was carried out on non-oxidative conversion of methane and its mixture with water into gaseous and liquid products in the barrier discharge (BD) plasma. The major products of methane conversion are hydrogen (~60 %) and ethane (~29 %), and also gaseous C3–C4 hydrocarbons (~10 %) and С₅₊ alkanes (~1 %), of mainly isomeric composition. The conversion of methane is 9.5–9.7 % in both cases, which corresponds to the energy consumption for CH4 reforming in the order of 46 eV/molecule. The presence of water on plasma-chemical reactor walls makes conditions for the efficient withdrawal of products from the discharge zone and prevents the formation of a deposit on the surface of the electrodes, which is proven by IR spectroscopy data. The paper deals with the redox mechanism of methane conversion in the BD plasma. As demonstrated, there is reaction initiation resulting from the collision of methane molecules with discharge electrons. Methyl and methylene radicals, and also atomic and molecular hydrogen, are mainly generated as a consequence of dissociation of the electron-excited methane molecule. Reaction products are further formed via the radical mechanism. The kinetics of transformation of the methane-water vapour-gas mixture into BD was modelled using the effective rate constant of the electron-molecular reaction and a simple expression to assess the value of the former. The expression for assessing the effective rate constant links the actual constant of the electron-molecular reaction rate to key parameters of the BD plasma and allows simplification of the simplification procedure of the modelling of the first. The chemical kinetics model for methane conversion involves 74 reactions. The calculation results are in good agreement with experimental data. As demonstrated by the analysis of reaction sensibility coefficients, there is an increase in the molecular mass of products mainly due to processes with methylene radical involvement.