Nonequilibrium plasma for the production of hydrogen from methane

Methane is an abundant molecule in the environment that is produced naturally by a variety of biological and nonbiological processes. Natural gas that comes from wells is from 75 to 90 mol. % methane. The production of hydrogen without CO₂ emission has regained interest in recent years as urgency for action on climate change is increasing. The production of hydrogen from methane is much less energy intensive than splitting water into hydrogen and oxygen, and so processes to split methane driven by renewable electricity are attractive in this context. Thermal plasmas have been explored for the synthesis of hydrogen and carbon products from methane. These processes operate by heating the gas to very high temperatures on the order of thousands of degrees Celsius, and then rapidly quenching the resulting gas to supress the reverse reaction. Energy efficiency, based on the power input and enthalpy of reaction, for these thermal plasma processes can be as high as 40%. We are exploring the idea that nonequilibrium plasmas may be able to achieve higher energy efficiency for methane splitting because the gas temperature remains much lower than in thermal plasmas. In other words, the idea is that the energy supplied to the nonequilibrium plasma is more effectively focused into the chemical reaction with less going to unwanted gas heating, when compared to thermal plasmas. If this idea is correct, then it should be feasible to realize an energy conversion efficiency greater than the thermal plasma benchmark of 40% for methane splitting to generate hydrogen. Results from experiments conducted by our group will be presented.