Synthesis of urea with NH₃ and CO₂ mixtures by pulsed dielectric barrier discharge plasma

Abstract This study explored urea synthesis using a dielectric barrier discharge (DBD) plasma with mixed gas (NH 3 + CO 2 ). The white crystals were characterized by 1 H NMR spectrum and SEM analysis. Plasma process parameter optimization (applied voltage, total flow rate, length of electrode, and frequency) was carried out to enhance the urea production. Among these factors, the electrode length was the most significant one. Lowering the gas hourly space velocity significantly impacted to weight and yield of white crystals. The results were 0.153 grams and 6.01%, respectively. The highest conversion of CO 2 and NH 3 was found to be 57.29% and 25.37%, respectively. To investigate the reaction mechanism of urea synthesis in DBD plasma, an Ansys Chemkin model with modified Arrhenius equations was used. This modeling collects various reaction kinetics and validates them against experimental data. The values predicted by the model had good agreement with the experiment results, especially at a total flow rate of 100 ml min −1 . Underlying the reaction mechanism, the most important reaction for urea synthesis is 2NH 2 + CO → CO(NH 2 ) 2 .