A study of methane plasma reactors and the catalytic effect of the tubular dielectric barrier discharge reactor

Date of Completion

January 2004


Engineering, Chemical




It is important to look at converting methane into larger molecular weight hydrocarbons because the worlds' supply of natural gas is equivalent to the worlds' crude oil reserves. There are known processes such as the Fischer Tropsch process that can convert methane into larger molecular weight hydrocarbons but this process and other known processes are generally multistep processes. The study of using methane plasmas to produce larger molecular weight hydrocarbons is important because the plasma process converts methane to larger molecular weight hydrocarbons in a single step. ^ A methane plasma can produce liquid, polymeric, and gaseous hydrocarbon products. Previous plasma research has focused on characterizing only one product. In this study all the products that form in a methane plasma in both a microwave plasma and in a tubular dielectric barrier discharge reactor were studied. A new sampling system was developed for the microwave plasma system to better determine product selectivity and conversion. ^ Using the new sampling system the overall conversion of methane in both plasma systems could be modeled as a zero order plug flow reactor. The reaction rate constant was modified to be dependent on pressure and voltage or power. The modifications to the reaction rate constants were consistent with Huang and Suib. ^ Previous plasma studies reported either acetylene or ethane as the most abundant gaseous hydrocarbon product. Only one person has been able to produce either ethane or acetylene as the most abundant hydrocarbon gaseous product. The microwave plasma system was able to produce either acetylene or ethane as the most abundant gaseous hydrocarbon product. The specific energy (kJ/mole) of methane was important in determining whether ethane or acetylene is the most abundant gaseous hydrocarbon product. ^ In microwave systems, high surface area catalysts have been used to convert methane into larger hydrocarbons. In the tubular reactor the electrode was coated with different metals and even though the electrode had a relatively low surface area catalytic affects have been reported for water splitting, CO2 decomposition, and NO reduction. By studying all the products and reactor conditions the specific energy of the tubular reactor was reduced to prevent polymer formation so that a catalytic effect was found with methane by using electrodes of different metals. A catalytic cycle was also demonstrated in the plasma system, which no plasma catalyst study had ever reported. ^