Non-thermal atmospheric plasma synthesis of ammonia in a DBD reactor packed with various catalysts

Abstract

Abstract Plasma synthesis of ammonia (NH 3 ) is a potential and sustainable pathway for nitrogen fixation. In this study, non-thermal plasma (NTP) synthesis of NH 3 was conducted in a packed-bed dielectric barrier discharge (DBD) reactor. Different catalysts, including alumina (Al 2 O 3 ), light magnesium oxide (L-MgO), heavy magnesium oxide (H-MgO), Ru/Al 2 O 3 and Ru/L-MgO, were filled in the reactor and compared for NH 3 production. Various characterization techniques were used to determine the specific surface area and pore size, surface morphology, and surface acidity of the catalysts. The effects of reaction conditions on NH 3 production were examined. Results showed that the optimal N 2 /H 2 volume ratio was 2:1 since a greater quantity of N 2 favored the generation of plasma-excited nitrogen species. The synthesized NH 3 can be adsorbed by the acid sites on Al 2 O 3 , which reduced the NH 3 yield. Higher total gas flow rate improved the NH 3 production over various catalysts, mainly due to the reduced external diffusion resistance. More plasma-excited nitrogen and hydrogen species for NH 3 synthesis were formed at higher discharge power, yet the increasing rate of NH 3 yield became slower when the discharge power was higher than 32 W. Additionally, the NH 3 desorption from the catalyst was enhanced at higher temperature, which resulted in higher NH 3 yield.