Abstract: Direct conversion of methane to more useful chemicals and fuels remains a challenge for the 21st century because of the high stability of methane molecule. In this work, direct conversion of methane and carbon dioxide using dielectric barrier discharge plasma was investigated. The discharge gaps applied are 1.8 mm and 1.1 mm, respectively. The product includes gaseous hydrocarbons (C2 to C5), syngas, liquid hydrocarbons (C5 to C11) and oxygenates. The liquid hydrocarbons are highly branched which presents a high octane number as liquid fuel; and oxygenates mainly consist of alcohols and acids. With the increasing of carbon atoms in the molecule, selectivity of hydrocarbons and oxygenates decreases accordingly. A detailed analysis of product distribution has been conducted under variable feed conditions with different discharge gaps. Higher CH4 concentration in the feed is more favored for production of hydrocarbons, while the highest selectivity of alcohols and acids is obtained at the methane feed concentration of 75.1％ (volume fraction) and 67.4％ (volume fraction),respectively. To achieve a large conversion of CH4 and CO2 and a high yield of hydrocarbons and acids, the narrower discharge gap (1.1 mm) is preferred, while a wider discharge gap (1.8 mm) induces a more selectivity production of alcohols.

Key words: Methane, Carbon dioxide, Dielectric barrier discharge, Cold plasma