Influence of C atom concentration for acetylene production in a CH4/N-2 afterglow

The dissociation of methane in the nitrogen flowing afterglow of a microwav e plasma has been studied. The yields of C-2 hydrocarbons were analysed by gas chromatography and were calculated by numerical simulation. The modelli ng was based on a macroscopic kinetic approach including a set of 166 react ions and 45 species. A good agreement is obtained between measurements and modelling. Acetylene formation (6-9%) shows a different behaviour compared to the formation of ethane and ethene (0.3-1.1%). By means of the computer modelling, an interesting result was obtained concerning the important role of atomic carbon in the production of acetylene. The main reaction leading to C atom formation is CH4 + N-2(a ') --> C + 2H(2) + N-2. Then C atoms can react with CH, or CH, radicals and thus give acetylene. (C ) 2001 Elsevier Science Ltd. All rights reserved.