Direct Conversion of Natural Gas Resources to Nitrogen-Containing Products via Nonthermal Plasma Stimulation

New electrically driven processes to decrease the carbon footprint associated with pharmaceutical, agrochemical, and fine chemical industries are of significant interest. For example, electrocatalysis, photocatalysis, and plasma catalysis are capable of driving C-N bond formation pertinent to these industries, as the high energy electrons in these systems are able to activate stable hydrocarbons and molecular nitrogen. Recently, direct plasma-assisted C-N coupling reactions to produce nitrogen-containing chemicals from CH4/N2 feeds have been identified as a promising approach to combat CO2 emissions and provide an alternative to the multistep processes used industrially. Additionally, the abundance of shale gas in the United States presents an opportunity to utilize this resource for chemical production. This thesis explores the synthesis of nitrogen-containing chemicals from nitrogen, methane, ethane, and propane in a dielectric barrier discharge reactor. Initial studies with a mixed hydrocarbon feed found that in nitrogen-lean regimes, hydrocarbon products dominated, while nitrogen-containing liquids were observed with nitrogen-rich feeds. To improve productivity, Ag and Cu supported on MgO were studied in the plasma reaction. The metal catalysts led to increased liquid formation and nitrogen incorporation compared to MgO. Next, to better understand the contributions of methane, ethane, and propane in the mixed feed, the differences that arise from the individual hydrocarbons in the presence of nitrogen were explored. Methane led to the most nitrogen-rich liquids, while propane led to the highest liquid production rate. Finally, a study on the effect of reaction time showed only minor differences between the liquid formed after 1 minute and after 30 minutes. However, when operated under cooling (-10 °C) or heating (200 °C) conditions, higher molecular weight compounds formed at -10 °C, possibly due to liquid remaining in the plasma zone and continuing to react throughout the experiment. This thesis demonstrates that a plasma-assisted process is a promising approach for upgrading natural gas to nitrogen-containing compounds. Investigating the effect of other possible feed components (i.e. CO2, O2), operating at low conversion to better understand initial products and reaction kinetics, and additional processing of the liquid product post-reaction to improve selectivity could further advance the understanding and applicability of this process.