Comparative Plasma Chemical Reaction Studies of CH sub(4)/Ar and C sub(2)H sub(m)/Ar (m = 2,4,6) Gas Mixtures in a Dielectric Barrier Discharge

Plasma chemical reactions in CH4/Ar and C sub(2)H sub()m/Ar (m = 2, 4, 6) gas mixtures in a dielectric barrier discharge at medium pressure (300 mbar) have been investigated. From mass spectrometry the production of H sub(2) and formation of larger hydrocarbons such as C sub(n)H sub()mwith up to n = 12 is inferred. Hydrogen release is most pronounced for CH sub(4) and C sub(2)H sub(6) gas mixtures. Fourier Transform InfraRed (FTIR) spectroscopy reveals the formation of substituted alkane (sp super(3)), alkene (sp super(2)), and alkyne (sp) groups from the individual gases which are used in this work. Abundant formation of acetylene occurs from C sub(2)H sub(4) and to a lesser extent from C sub(2)H sub(6) and CH sub(4) precursor gases. The main reaction pathway of acetylene leads to the formation of large molecules via C sub(4)H sub(2) and, eventually, to nano-size particles. The experimental results are in reasonable agreement with simulations which predict a pronounced electron temperature and gas pressure dependency. ( copyright 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)