Production of synthesis gas through plasma-assisted reforming of greenhouse gases

Low temperature conversion of the two major greenhouse gases CO2 and CH4 to synthesis gas (a mixture of H-2 and CO) is investigated theoretically and experimentally in a high power dielectric-barrier discharge (DBD). Utilising this nonequilibrium discharge technique high conversion rates can be achieved in this special gas mixture. A pronounced synergetic effect caused by free radical reactions was observed using these two gases simultaneously. This way CO2 separated from flue gases could be combined with methane to produce syngas which then can be processed to yield liquid fuels like e.g. methanol or dimethyl ether. Parameters studied are CH4/CO2 mixing ratio (0 - 100% of CO2), electric power(100 - 800 W), flow rate (0.1 - 4 Nl/min), gas pressure (0.35 - 2 bar) and reactor wall temperature (80 degrees C 250 degrees C). This technique of plasma reforming of methane with carbon dioxide can produce syngas with different H-2/CO ratios depending mainly on the CH4/CO2 mixing ratio. The amount of syngas produced rises almost linearly with increasing discharge power. Up to 66 moles of syngas with a H-2/CO ratio of 3.7 were obtained from 100 moles of feed gas in a single pass through the DBD reactor of 31 cm active length. The minimum required specific energy was 40 eV/molecule for the production of syngas (H-2 plus CO) and the highest energy efficiency (electric energy converted to chemical energy in the syngas) reached so far was about 7%.