Carbon dioxide is among the most crucial impurity in natural gas and must be removed from the gas before any use to avoid environmental damage and problem. The CO₂ absorption with the alkanolamine process is widely used for this purpose. This study has been dedicated to modeling the aqueous CO₂+ N-methyldiethanolamine (MDEA) system's vapor-liquid equilibrium within the temperature range 297.7-413.15 K and gas loading in the range of 0.000249-1.507 CO₂ mole/MDEA mole. In combination with the Wong-Sandler mixing rule and the NRTL activity coefficient model, the Peng-Robinson equation of state has been applied as an EOS/G^E approach for modeling of vapor-liquid equilibrium of the CO₂-MDEA-H₂O system. For improving the performance of the model, five alpha,α, functions have been considered for the Peng-Robinson equation of state.

Moreover, ions in the aqueous phase have been accounted for by contributions of the short-range, long-range interactions and the Born term in the Wong-Sandler mixing rule through the Peng-Robinson equation of state. Initially, the binary interactions of the CO₂+H₂O and MDEA+H₂O systems are optimized. Using 283 experimental data of carbon dioxide solubility in the MDEA solution, one can calculate the other binary, and energy interaction parameters by applying simultaneous chemical and phase equilibrium computations. Consequently, to achieve the present modeling's predictability, the obtained parameters were used to predict the other 313 point data's phase equilibrium. The present model results showed that a good agreement is obtained between the calculated and experimental data. The Coquelet and Chapoy (C&C) and Twu alpha, α, functions present more accurate results than the others.

二氧化碳是天然气中最关键的杂质之一，在使用前必须将其从天然气中清除，以免造成环境破坏和问题。为此，广泛使用链烷醇胺法吸收CO ₂。这项研究致力于模拟在297.7-413.15 K温度范围内的CO ₂ + N-甲基二乙醇胺（MDEA）水溶液系统的气液平衡以及在0.000249-1.507 CO ₂摩尔/ MDEA摩尔范围内的气体负载。结合Wong-Sandler混合规则和NRTL活度系数模型，将Peng-Robinson状态方程作为EOS / G ^E方法用于模拟CO ₂ -MDEA-H ₂的气液平衡O系统。为了改善模型的性能，已经为彭-罗宾逊状态方程考虑了五个α，α函数。

此外，水相中的离子是通过Peng-Robinson状态方程通过Wong-Sandler混合规则中的短程，长程相互作用和Born项的贡献来解释的。最初，CO ₂ + H ₂ O和MDEA + H ₂的二元相互作用O系统已优化。利用283种在MDEA溶液中二氧化碳溶解度的实验数据，可以通过同时进行化学和相平衡计算来计算其他二元和能量相互作用参数。因此，为了获得当前模型的可预测性，所获得的参数可用于预测其他313点数据的相位平衡。目前的模型结果表明，在计算和实验数据之间获得了很好的一致性。Coquelet和Chapoy（C＆C）和Twu alpha，α，函数比其他函数提供更准确的结果。