H2S is a kind of impurity in the alternative energy resource of biogas and landfill gas. Among the removal methods, absorption by alkanolamines is the commonly accepted and widely used ones. This is due to the efficient regeneration. In this study, the absorption mechanism of H2S by two alkanolamines, namely diethanolamine (DEA) and N-methyldiethanolamine (MDEA), was proposed in a different way and analyzed by DFT calculations. The structural, energetic, red shifts and topological analysis of the most stable structures were then investigated. The values of electron densities and Laplacian densities at the bond critical points fall in the range of a hydrogen bond. Two kinds of hydrogen bonds S–H···N and O–H···S formed between H2S and DEA/MDEA are considered to be the driving forces during the absorption process. Thus, it can be known that H2S can act as both a hydrogen bond acceptor and a donor. Besides, the S–H···N hydrogen bond is much stronger than the O–H···S hydrogen bond. According to the change rules of Gibbs energies, the formation of hydrogen bond becomes difficult with increasing temperature and deceasing pressure. The absorption mechanism of H2S captured by alkanolamines via hydrogen bond interaction provides a novel theoretical direction for further study.

中文翻译：

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烷醇胺捕获 H2S 的探索

H2S是沼气和垃圾填埋气替代能源中的一种杂质。在去除方法中，烷醇胺吸附是普遍接受和广泛使用的方法。这是由于有效的再生。在这项研究中，以不同的方式提出了两种烷醇胺，即二乙醇胺 (DEA) 和 N-甲基二乙醇胺 (MDEA) 对 H2S 的吸收机理，并通过 DFT 计算进行了分析。然后研究了最稳定结构的结构、能量、红移和拓扑分析。键临界点处的电子密度和拉普拉斯密度值落在氢键范围内。H2S与DEA/MDEA之间形成的两种氢键S–H…N和O–H…S被认为是吸收过程中的驱动力。因此，可知H2S既可以作为氢键受体，也可以作为供体。此外，S-H...N 氢键比 O-H...S 氢键强得多。根据吉布斯能的变化规律，随着温度的升高和压力的降低，氢键的形成变得困难。烷醇胺通过氢键相互作用捕获H2S的吸收机理为进一步研究提供了新的理论方向。