Jeffrey B. Harrison

Activation of methane in microwave plasmas at high pressure

Methane is converted to C2 products in a microwave plasma under pressure up to 400 torr at maximum plasma power of 100 W. Steam is introduced with methane into the plasma zone in order to suppress coke formation. Major products are C2 hydrocarbons. Small amounts of benzene are also formed. Very small amounts of some unusual highly unsaturated hydrocarbons are also formed. Oxygenated products are CO and CO2. The conversion and yields are related to experimental variables by an empirical second order linear model. The conversion of methane ranges from 10 to 60%. The yield of C2 products ranges from 5 to 68%. The major C2 product is acetylene.

Selecting oxygen source for partial oxidation of methane to methanol using microwave plasmas

The methanol selectivity in partial oxidation of methane in microwave plasma reactors is improved by using H2O in the presence or absence of O2. The use of H2O2 as an oxygen source has a similar effect, although it is less effective than H2O. The addition of H2 to the system has little effect on selectivity. Two pathways are suggested for the formation of methanol. One involves a CH3O* or CH3O2* intermediate, while the other involves a direct combination of CH3* and OH* radicals. The first pathway is favored in the presence of O2 while the latter is favored in the presence of H2O or H2O2. The best results are obtained for the CH4-O2-H2O system when methanol is formed through both pathways.

Stabilization of microwave arc plasmas of hydrocarbons at atmospheric pressure

Pure hydrocarbon plasmas have been generated at low pressures with good efficiency using methane as a reactant. Hydrocarbon plasma discharges containing high energy, free radical, and ionized intermediates were analyzed in situ using emission spectroscopy. Emission spectra were correlated with analytical data obtained from resultant product mixtures and literature assignments of emission bands in order to identify these intermediates. Stabilization of atmospheric methane plasmas using argon as a diluent has also been demonstrated in this study. Emission spectroscopy has also been used to identify reaction intermediates formed in plasmas at high pressures. Distinct differences in plasma discharges have been observed as a function of pressure, power, and methane concentrations at the molecular level using in situ spectroscopic techniques.