Nitrogen fixation with renewable electricity: Plasma catalysis as an alternative for small-scale ammonia synthesis?

This PhD thesis presents an investigation into plasma-catalytic ammonia synthesis in a dielectric barrier discharge (DBD) plasma reactor. Ammonia (NH3) can be synthesized from hydrogen gas (H2) and nitrogen gas (N2). Ammonia has current applications as intermediate for the fertilizer industry and the chemical industry. About 45% of the current pure hydrogen demand in industry is used for ammonia production. Future applications of ammonia include its use as zero-carbon fuel and as hydrogen carrier. Thus, ammonia may play a significant role in a decarbonized energy landscape. Ammonia is currently produced via the Haber-Bosch process.

This PhD thesis investigates whether pre-activation by a non-thermal plasma can loosen the nitrogen-nitrogen bond before reacting on the catalyst, thereby allowing for operation under milder conditions as compared to the Haber-Bosch process. A non-thermal plasma can be operated in a dielectric barrier discharge (DBD) plasma reactor at near-ambient temperatures. Highly energetic electrons are formed through electric fields and collisions with molecules, such as molecular nitrogen. The bulk of the gas will remain at near-ambient temperatures. Low temperature operation of the plasma reactor implies that the equilibrium shifts towards ammonia formation, implying the process can be operated at ambient pressure. Another benefit of the plasma reactor is that it is fed with electricity, and the mild operating conditions imply that the reactor can be easily started up and shut down.