Diagnosis of atmospheric pressure low temperature plasma and application to high efficient methane conversion

Direct dehydrogenation of methane to produce more useful chemicals was examined using low temperature plasmas such as DBD, corona and spark discharge under the conditions of room temperature and atmospheric pressure. In spark discharge, acetylene was produced with the selectivity higher than 85% and small amount of deposited carbon. The energy efficiency in spark discharge was much higher than that in DBD and corona discharge. By the emission spectroscopy, it was found that methane was highly dissociated to atomic carbon and hydrogen in spark discharge. The gas temperature in spark discharge channel remained as low as 420–460 K determined by Boltzmann plot method of CH rotational band (431 nm). The specific energy requirement for acetylene was improved by the optimization of reactor size and residence time and reached 12.1 kW h/kg-C2H2, which was as same as Huels process with DC arc plasma.