| Scope and method of study. The purpose of this study was to investigate the potential for forming higher molecular weight hydrocarbons from the reaction of methane in a dielectric barrier discharge plasma reactor. The product composition was measured for a pure methane feed under different operating conditions. Three operating variables were studied: electric field strength (127--180 kV/cm), AC frequency (200--300 Hz), and residence time (2.2--5.1 seconds). A framework for modeling this process was developed using 85 kinetic reaction equations and appropriate mass balances. The model simulates the discharge and relaxation phases that occur in a dielectric barrier discharge and is able to account for changes in AC frequency and residence time.; Findings and conclusions. A variety of higher molecular weight hydrocarbons were formed from the reaction of methane in the dielectric barrier discharge plasma reactor: ethane, ethylene, propane, propylene, isobutane, n-butane, and pentane. A maximum methane conversion of 6% occurred at 180 kV/cm, 250 Hz. and at a residence time of 5.1 seconds. Higher molecular weight liquid and solid products were also formed but were not analyzed. As the electric field, the AC frequency, or residence time was increased, the conversion of methane also increased. At higher electric potentials, the selectivity of paraffins increased at the expense of olefins. Higher AC frequencies increased the selectivity of propane and higher molecular weight hydrocarbons at the expense of ethane and ethylene. Longer residence times also resulted in the increased selectivity of propane and higher molecular weight hydrocarbons at the expense of ethane and ethylene. The model showed good quantitative agreement with experimental data for the range of residence times studied and good qualitative agreement with experimental data for the range of frequencies studied. |
