Catalyst-free production of ammonia by means of interaction between a gliding arc plasma and water surface

Abstract

This work reports a study on using a gliding arc plasma reactor to produce ammonia from nitrogen plasma and a water medium without using a catalyst. During the gliding arc plasma discharge, a plasma plume was formed, and vibrational and rotational excitation was observed at the tip of the plasma plume that touched the water below. This arrangement helped the formation of ammonia. The ammonia concentration was 2.12–5.69 ppm, and its production rate varied in the range of 0.63–0.68 mg h−1, having energy efficiency in the range of 0.0249–0.0268 g-NH3 kWh−1, depending on the plasma exposure time. The vibrational temperature increased from 2632 K (near the gas entry zone) to 3778 K (at the tip of the plasma plume interacting with the water), corroborated by the enhanced distribution of electron energy for vibration excitation (≈24%), compared to that for electronic excitation (≈0.03%). The electron temperature dropped from 1.38 eV to 0.76 eV at the plasma zone interacting with the water. This work demonstrates the application of gliding arc plasmas to generate eco-friendly ammonia (green ammonia), and the reactor proves to be promising for further optimization in the future.