Theoretical Investigations of Methane Conversion to Heavier Hydrocarbons in a Plasma Reactor

Abstract

In this study, mathematical modeling of Oxidative Coupling of Methane (OCM) to C2 hydrocarbons (C2H6 and C2H4) over La2O3/CaO catalyst in a fixed-bed reactor operated under isothermal and non-isothermal conditions was investigated. The kinetic model proposed for OCM process consisted of 10 elementary reactions and 8 chemical species. In this process, methane and acetylene were the inputted feed and ethane, ethylene, propylene, propane, i- butane and n-butane were the output products. The amount of methane conversion obtained was 12.7% for the former feed, however, if pure methane was inputted this conversion rose to 13.8%. Furthermore, the plasma process would enhance the conversion, selectivity towards desired product and yield. In the present study, when methane and acetylene were fed at a molar ratio of CH4/C2H2=10 to the reactor, the selectivity of C2, C3 and C4 hydrocarbons was determined to be 30, 24 and 44% respectively. Concurrently, a higher yield was obtained for n-butane at about 3.9% and the minimum yield achieved for propylene was approximately 0.7%. A comparison between the thermal and the plasma process showed that the methane conversion and yield production in the plasma were higher than in the thermal process under the same operating conditions. On the other hand, product selectivity in the plasma process was determined to be lower than that of the thermal process. Finally, the results of the catalytic OCM and methane conversion processes in the plasma phase were compared with one another.