Plasma-catalytic ammonia synthesis: Packed catalysts act as plasma modifiers

We studied the plasma-catalytic production of NH3 from H2 and N2 in a dielectric barrier discharge plasma reactor using five different Co-based catalysts supported on Al2O3, namely Co/Al2O3, CoCe/Al2O3, CoLa/Al2O3, CoCeLa/Al2O3 and CoCeMg/Al2O3. The catalysts were characterized via several techniques, including SEM-EDX, and their performance was compared. The best performing catalyst was found to be CoLa/Al2O3, but the dif-ferences in NH3 concentration, energy consumption and production rate between the different catalysts were limited under the same conditions (i.e. feed gas, flow rate and ratio, and applied power). At the same time, the plasma properties, such as the plasma power and current profile, varied significantly depending on the catalyst. Taken together, these findings suggest that in the production of NH3 by plasma catalysis, our catalysts act as plasma modifiers, i.e., they change the discharge properties and hence the gas phase plasma chemistry. Importantly, this effect dominates over the direct catalytic effect (as e.g. in thermal catalysis) defined by the chemistry on the catalyst surface.

Automated summary

We investigated the production of NH3 from H2 and N2 in a dielectric barrier discharge plasma reactor using different Co-based catalysts supported on Al2O3. The catalysts were characterized using various techniques and their performance was compared. CoLa/Al2O3 was found to be the best performing catalyst, but the differences in NH3 concentration, energy consumption, and production rate between the catalysts were limited under the same conditions. The plasma properties, such as power and current profile, varied significantly depending on the catalyst, indicating that the catalysts act as plasma modifiers.