Peculiarities of Carbamide Hydrolysis and Oxidation in a Water–Oxygen Fluid

IF 1.4 4区 化学 Q4 PHYSICS, ATOMIC, MOLECULAR & CHEMICAL
A. V. Shishkin, S. A. Alekhin, M. Ya. Sokol, A. A. Vostrikov, O. N. Fedyaeva
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Abstract

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%) are studied in a batch reactor when heated to 873 K at a rate of 1 K/min. It is 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 the decomposition of cyanuric acid. From the analysis of the time dependencies 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 is 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.

Abstract Image

水-氧流体中尿素水解和氧化的特性
在间歇反应器中,以1 K/min的速率加热至873 K,研究了尿素在水-氧流体(尿素浓度0.29 ~ 0.39 mol/L,氧过量系数OR = 0.98 ~ 1.25,水摩尔分数70 ~ 91.3%)中的转化。结果表明,这些转化是通过平行反应和顺序反应进行的,包括尿素水解、三聚氰尿酸的生成和分解、氨的氧化和三聚氰尿酸分解产物。从温度和压力的时间依赖性分析可知,尿素的氧化主要发生在反应器壁表面和插入反应体积中心的Pt-Rh / pt热电偶上。结果表明,过量的氧(OR = 1.25)或NaOH的加入会导致氮转化为N2的比例增加,从而阻止三聚尿酸的形成。讨论了试剂浓度对尿素转化途径比例和放热动力学的影响。
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来源期刊
Russian Journal of Physical Chemistry B
Russian Journal of Physical Chemistry B 化学-物理:原子、分子和化学物理
CiteScore
2.20
自引率
71.40%
发文量
106
审稿时长
4-8 weeks
期刊介绍: Russian Journal of Physical Chemistry B: Focus on Physics is a journal that publishes studies in the following areas: elementary physical and chemical processes; structure of chemical compounds, reactivity, effect of external field and environment on chemical transformations; molecular dynamics and molecular organization; dynamics and kinetics of photoand radiation-induced processes; mechanism of chemical reactions in gas and condensed phases and at interfaces; chain and thermal processes of ignition, combustion and detonation in gases, two-phase and condensed systems; shock waves; new physical methods of examining chemical reactions; and biological processes in chemical physics.
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