Stowe Haley M, Vilčiauskas Linas, Paek Eunsu, Hwang Gyeong S
Materials Science and Engineering Program, University of Texas at Austin, Austin, Texas 78712, USA.
McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712, USA.
Phys Chem Chem Phys. 2015 Nov 21;17(43):29184-92. doi: 10.1039/c5cp04876a.
AMP and its blends are an attractive solvent for CO2 capture, but the underlying reaction mechanisms still remain uncertain. We attempt to elucidate the factors enhancing bicarbonate production in aqueous AMP as compared to MEA which, like most other primary amines, preferentially forms carbamate. According to our predicted reaction energies, AMP and MEA exhibit similar thermodynamic favorability for bicarbonate versus carbamate formation; moreover, the conversion of carbamate to bicarbonate also does not appear more favorable kinetically in aqueous AMP compared to MEA. Ab initio molecular dynamics simulations, however, demonstrate that bicarbonate formation tends to be kinetically more probable in aqueous AMP while carbamate is more likely to form in aqueous MEA. Analysis of the solvation structure and dynamics shows that the enhanced interaction between N and H2O may hinder CO2 accessibility while facilitating the AMP + H2O → AMPH(+) + OH(-) reaction, relative to the MEA case. This study highlights the importance of not only thermodynamic but also kinetic factors in describing CO2 capture by aqueous amines.
AMP及其混合物是一种有吸引力的二氧化碳捕集溶剂，但潜在的反应机制仍不确定。我们试图阐明与MEA相比，在AMP水溶液中促进碳酸氢盐生成的因素，MEA与大多数其他伯胺一样，优先形成氨基甲酸盐。根据我们预测的反应能量，AMP和MEA在形成碳酸氢盐与氨基甲酸盐方面表现出相似的热力学优势；此外，与MEA相比，在AMP水溶液中氨基甲酸盐向碳酸氢盐的转化在动力学上也没有更有利。然而，从头算分子动力学模拟表明，在AMP水溶液中形成碳酸氢盐在动力学上更有可能，而在MEA水溶液中更有可能形成氨基甲酸盐。对溶剂化结构和动力学的分析表明，相对于MEA的情况，N与H2O之间增强的相互作用可能会阻碍CO2的可及性，同时促进AMP + H2O → AMPH(+) + OH(-)反应。这项研究强调了在描述胺水溶液捕集CO2时，不仅热力学因素而且动力学因素的重要性。
