Hydrogenation of plasma-excited nitrogen over an alumina catalyst for ammonia synthesis

摘要

Ammonia (NH3) is a potential hydrogen carrier as alternative fuel and feedstock for hydrogen production. In this study, plasma synthesis of NH3was conducted in a packed-bed dielectric barrier discharge (DBD) reactor using Al2O3as the catalyst. In order to explore the mechanism of hydrogenation of plasma-excited nitrogen for NH3synthesis, the whole NH3synthesis process was divided into three steps including N2activation, hydrogenation of plasma-excited N(a), and desorption of NH3(a) from catalyst. The effects of reaction conditions on the three steps and corresponding NH3production were examined. Results showed that more plasma-excited nitrogen species were formed through N2activation at higher N2flow rate, discharge time and discharge power for N2activation. Hydrogenation of plasma-excited N(a) to form NH3(a) was improved by more discharge time at the second step. Higher discharge temperature for N(a) hydrogenation favored NH3(a) desorption from catalyst and increased NH3production at the second step, with the total NH3yield slightly changed. In addition, one-step NH3synthesis in plasma was investigated and compared with the three-step process. The results will provide reference for catalyst and reactor design in plasma synthesis of ammonia.