WHAT IS PLASMA-ASSISTED CHEMICAL SYNTHESIS?
Electric discharge applied to gases generates a variety of short-lived but highly reactive species such as radicals, atoms, and vibrationally excited molecules which react more readily at lower temperatures. This feature enables diverse and alternate chemical reaction pathways, making reactions feasible at lower temperatures, not possible in traditional thermal or catalytic reaction activation.
The special features of plasmas permit significant intensification of chemical processes, essentially with an increase in thermal efficiency, and often successful stimulation of chemical reactions impossible in conventional thermal chemistry.
Further, synergistic effects in chemical synthesis are expected if catalysts are placed in the plasma, i.e., the combined reaction rate using plasma and catalysis is higher than the summation of the reaction rate of each individual approach. In recent studies of plasma-assisted Dry Methane Reforming (DMR), we find that with a combination of plasma and catalysts, we can achieve such synergistic multiple factor enhancements in chemical product yields as shown in Figure 3, with high thermodynamic efficiency.
Plasma Technology and Renewable Energy
Plasma technology also enables the use of renewable energy to drive reactions at less harsh conditions of temperature and pressure to store renewable energy as chemical energy, by producing valuable chemicals. Plasma technology can enable Carbon Capture and Storage (CCS) processes using renewable energy.
Plasma Reactivity Levels
It is possible to achieve high levels of reactivity not possible with just the plasma or catalyst by combining a catalyst with plasma. Figure 4 shows how the activation energies for a reaction could be altered in an environment with just a catalyst and with both plasma and catalyst. By vibrational and other forms of excitation (electronic, dissociation etc.), the plasma can greatly reduce the activation energy required for a reaction in the presence of a catalyst. In recent years there has been intense, ongoing research to fully exploit the potential of PC for chemicals synthesis using low quality (low temperature) energy from waste heat and renewable sources such as solar and wind energy. At ACT we are developing technologies to synthesize chemicals using greenhouse gases as feedstock (methane and carbon dioxide). The chemicals of interest include syngas (CO+H2), ammonia, various alcohols, formaldehyde, MTBE (methyl tertiary-butyl ether).
Pearlman, H. et al. Plasma-Assisted Dry Methane Reforming for Syngas Production. in Spring Technical Meeting Eastern States Section of the Combustion Institute (2018).
Mehta, P., Barboun, P., Go, D. B., Hicks, J. C. & Schneider, W. F. Catalysis Enabled by Plasma Activation of Strong Chemical Bonds: A Review. ACS Energy Letters 4, 1115–1133 (2019).