Key words: carbamide, ammonia, water-oxygen fluid, oxidation, hydrolysis
The transformations of carbamide in a water-oxygen fluid (at a carbamide concentration of 0.29—0.39 mol/l, oxygen excess coefficient OR = 0.98—1.25, mole fraction of water 70.0—91.3 %) was studied in a reactor periodic type when heated to 873 K at a rate of 1 K/min. It has been shown that the transformations proceed via the mechanism of parallel and sequential reactions, including carbamide hydrolysis, formation and decomposition of cyanuric acid, oxidation of ammonia and products of cyanuric acid decomposition. From the analysis of the time dependences of temperature and pressure, it follows that the oxidation of carbamide occurs predominantly heterogeneously on the surfaces of the reactor wall and the Pt—Rh/Pt-thermocouple inserted into the center of the reaction volume. It has been established that excess oxygen (OR = 1.25) or the addition of NaOH leads to an increase in the fraction of nitrogen converted into N2 and prevents the formation of cyanuric acid. The influence of the concentration of reagents on the ratio of carbamide conversion pathways and the dynamics of heat release is discussed.
doi:10.1134/S1990793124700994