Carbamates of primary or secondary amines play a central role in amine CO₂ absorbents. The equilibrium constant of a carbamate hydrolysis reaction, K_ch, is important for evaluating the performance of absorbents. However, few K_ch values have been reported to date. We determined the K_ch values of normal amines, such as monoethanolamine (MEA), diethanolamine (DEA), and hindered amines, such as 2-amino-2-methyl-1-propanol (AMP) and 2-(isopropylamino)ethanol (IPAE), using a method involving a combination of ¹³C NMR spectroscopy and a chemical equilibrium analysis. The Gibbs energy changes derived from K_ch for AMP and IPAE at 25 °C were negative, whereas those for normal amines, MEA and DEA, were positive. These properties are characteristic of hindered amines. We determined the standard enthalpy and entropy changes of the carbamate hydrolysis reactions from the temperature dependence of the equilibrium constant. The equilibrium constants and standard enthalpies obtained using the present method will be valuable for evaluating the performance of amine CO₂ absorbents.

伯胺或仲胺的氨基甲酸酯在胺CO ₂吸收剂中起核心作用。氨基甲酸酯水解反应的平衡常数K _ch对于评估吸收剂的性能很重要。但是，迄今为止，几乎没有报道过K _ch值。我们确定了ķ _CH正常胺，如单乙醇胺（MEA），二乙醇胺（DEA）的值，和受阻胺，如2-氨基-2-甲基-1-丙醇（AMP）和2-（异丙基氨基）乙醇（ IPAE），使用¹³ C NMR光谱学和化学平衡分析相结合的方法。由K _ch得出的吉布斯能量变化AMP和IPAE在25°C时为阴性，而普通胺，MEA和DEA则为阳性。这些性质是受阻胺的特征。我们根据平衡常数的温度依赖性确定了氨基甲酸酯水解反应的标准焓和熵变化。用本方法获得的平衡常数和标准焓对于评估胺CO ₂吸收剂的性能将是有价值的。