Nuclear Magnetic Resonance Analysis of Hydrothermal Reactions of Ethyl- and Octylamine in Sub- and Supercritical Water
Nuclear Magnetic Resonance Analysis of Hydrothermal Reactions of Ethyl- and Octylamine in Sub- and Supercritical Water
复制标题
乙胺和辛胺在亚临界和超临界水中的水热反应的核磁共振分析
DOI：
10.1021/acs.jpca.3c01213
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Nakahara Masaru
中科院分区：
文献类型：
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作者：
Yoshida Ken;Doi Ayato;Yoshioka Haruka;Hirano Tomohiro;Nakahara Masaru
近年来，脂肪族胺的水热反应在胺作为蒸汽-水循环成膜缓蚀剂的应用方面变得越来越重要。研究了乙基铵离子（EtAH+）和正辛基铵离子（OctAH+）的水热反应动力学和机理，并与相应的中性胺进行了比较，阐明了它们在300-400℃亚临界和超临界温度下的反应产物和反应途径作为脂肪族铵离子的模式反应。利用核磁共振光谱分析了13c - 15n标记的EtAH+的反应，发现其水解为乙醇的主要途径是先发生消除反应生成乙烯，然后发生歧化反应生成二乙基铵阳离子。OctAH+生成辛烯和辛醇，每一种都异构化为热力学上更稳定的主要产物。比较了中性胺和铵离子的反应，突出了它们不同的反应活性。在低ph条件下，水解、烯烃形成和醇类脱水成烯烃的过程都加快了，而低分子量有机酸如乙酸和甲酸的形成则没有观察到。这些结果表明，在pH值高达9 ~ 10的实际条件下，成膜胺的防腐效果将保持不变，从而抑制副产物的副反应。
Hydrothermal reactions of aliphatic amines have recently gained importance in relation to the application of amines as film-forming corrosion inhibitors for steam–water cycles. The kinetics and mechanism of the hydrothermal reactions of ethylammomiun cation (EtAH+) andn-octylammonium cation (OctAH+) were studied for comparison with the corresponding neutral amines to elucidate their reaction products and pathways at sub- and supercritical temperatures of 300–400 °C as model reactions of aliphatic ammonium cations. We analyzed the reaction of13C-15N-labeled EtAH+using NMR spectroscopy and revealed that the initial hydrolysis to ethanol, known as the main path, is followed by the elimination reaction producing ethene and the disproportionation reaction giving diethylammonium cation. The OctAH+yields octene and octanol, each of which isomerizes to thermodynamically more stable species as the major products. Comparisons were made between the reactions of the neutral amines and ammonium cations to highlight their different reactivity. The hydrolysis, alkene formation, and dehydration of alcohols to alkenes were all found to be accelerated at low pH. The formation of low-molecular-weight organic acids such as acetic acid and formic acid was not observed. These results indicate that the corrosion protection effect of film-forming amines will be maintained under practical conditions with pH values as high as around 9 to 10, and hence side reactions involving byproducts will be suppressed.