Enhancing synthesis of urea from ammonia–carbon monoxide gas mixtures via pulsed-dielectric barrier discharge plasma

Abstract The direct synthesis of urea from ammonia (NH 3 ) and carbon monoxide (CO) at atmospheric pressure presents a promising yet challenging route for sustainable chemical production. In this study, pulsed dielectric barrier discharge (DBD) plasma was employed as a green and energy-efficient approach to facilitate the formation of urea from NH 3 and CO. Building upon previous success with NH 3 and CO 2 precursors, we optimize key plasma process parameters, including applied voltage, frequency, NH 3 /CO molar ratio, and gas hourly space velocity, to enhance urea yield. The resulting solid product was characterized using ¹H nuclear magnetic resonance spectroscopy, X-ray diffraction, high-performance liquid chromatography, and scanning electron microscopy, confirming the successful formation and high purity of urea crystals. A urea purity of 89% was achieved, with conversion rates of 34.39% for CO and 23.57% for NH 3 . The highest of urea yield achieved was 785 mg h⁻¹. These findings highlight the feasibility of using pulsed-DBD plasma for urea synthesis from NH 3 and CO, offering a sustainable approach to nitrogen–carbon coupling under ambient conditions.