No abstract

No abstract

No abstract

Methane reforming by carbon dioxide in pulsed glow discharge at atmospheric pressure is examined. The plasma pulse is compressed to less than 50ns. This compression enables one to work at higher frequencies, over 3kHz, without glow-arc transition. The main products of the reaction are synthetic gases (H2, CO) and C2 hydrocarbons. Approximately 42% of plasma energy goes to the chemical dissociation, when the reactant ratio is CO2∕CH4=1. At this point, the energy expense is less than 3.8eV per converted molecule while reactant conversions are relatively high reaching to 55% (CH4) and 42% (CO2). The reactor energy performance even gets better at higher CO2∕CH4 ratios. While energy efficiency reached about 45%, at feed ratio of CO2∕CH4=5, the conversions of about 65% and 45% were obtained for methane and carbon dioxide, respectively. A model describing dissociation through molecular vibrations is introduced. According to the model, the high nonequilibrium state of vibrational energy at short pulses leads to this improvement, especially in carbon dioxide.

The efficient production of syngas from a CH4+CO2 mixture in an atmospheric pulsed glow discharge, sustained by corona pre-ionization, has been investigated. The products were mainly syngas (CO, H2) and hydrocarbons up to C4, with acetylene having the highest selectivity. The energy efficiency was within 15–40% for different experimental conditions, which demonstrates a comprehensive improvement relative to the achievements of other types of non-equilibrium plasma. These values are, however, comparable with the efficiencies obtained by gliding arc plasmas but this plasma operates at near room temperature. Furthermore, it has been shown that the energy efficiency is increased by decreasing the effective residence time. The effects of molar ratio CH4 : CO2, voltage, repetition rate and gas flow rate on conversion, energy efficiencies and the selectivities have also been investigated. The higher efficiency obtained in this kind of plasma is discussed and attributed to the short pulse regime and electric field uniformity.