(506f) Towards Understanding Plasma-Assisted Catalytic Enhancement of Ammonia Synthesis over Supported Metal Catalysts
AIChE Annual Meeting
2019
2019 AIChE Annual Meeting
Catalysis and Reaction Engineering Division
Catalysis for Nitrogen Chemistry II: Plasma-Enhanced and Other Non-Thermal Approaches for N2 Activation
Wednesday, November 13, 2019 - 1:50pm to 2:10pm
Non-thermal, plasma-assisted catalysis is an emerging method of driving difficult chemical transformations at mild conditions relative to the thermal reaction.1 Synergistic interactions between the plasma and solid catalysts have been used to enhance reaction rates for the conversion of highly stable gases such as carbon dioxide, methane, and nitrogen.2 Plasma-assisted catalytic ammonia synthesis at atmospheric pressure, in particular, has been demonstrated repeatedly; however, investigations of the mechanism have been largely speculative to date. In this presentation, we will present evidence that the plasma facilitates low pressure ammonia synthesis by activating nitrogen and hydrogen in the gas phase, leading to enhanced adsorption of these reactants on the surface. Kinetic evaluation of the system over different metal catalysts reveals unexpected activity trends for catalysts subjected to the plasma environment. We show that nitrogen activation is the critical step in driving plasma-assisted ammonia synthesis in a dielectric barrier discharge. These results are further supported by temperature programmed reactions and in situ surface characterization. To further interrogate these systems, experiments evaluating the effects of reaction temperature and plasma properties on this system are presented. From these experiments, heating is shown to have a small impact on catalytic activity, while tuning discharge power controls both plasma phase and catalytic ammonia production rates.4 Lastly, we will discuss the proposed pathway by which non-thermal plasma enables low temperature ammonia synthesis, and we will showcase appropriate methodologies to investigate interactions between the plasma and catalyst.
(1) Neyts, E. C.; Ostrikov, K.; Sunkara, M. K.; Bogaerts, A. Chem. Rev. 2015, 115 (24)
(2) Mehta, P.; Barboun, P.; Go, D. B.; Hicks, J. C.; Schneider, W. F. ACS Energy Lett. 2019 5, (4)
(3) Mehta, P.; Barboun, P.; Herrera, F. A.; Kim, J.; Rumbach, P.; Go, D. B.; Hicks, J. C.; Schneider, W. F. Nat. Catal. 2018, No. 4.
(4) Barboun, P. Mehta, P. Herrera, F.A. Go, D.B. Schneider, W.F. Hicks, J.C. ACS Sus Chem & Eng, 2019 (Under Review)