Computer-Free Group-Addition Method for pKa Prediction of 73 Amines for CO2 Capture

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• 作者：Juan QianRui Sun ; Shaozeng Sun ; Jihui Gao
• 刊名：Journal of Chemical & Engineering Data
• 出版年：2017
• 出版时间：January 12, 2017
• 年：2017
• 卷：62
• 期：1
• 页码：111-122
• 全文大小：832K
• ISSN：1520-5134

文摘

The pK_a value of an amine aqueous solution is directly related to the rate of its chemical reaction with CO₂. A quick and accurate pK_a predicted method can provide a shortcut for efficient screening of CO₂ absorbents. The original and updated Perrin–Dempsey–Serjeant (PDS) pencil-and-paper group-addition methods were used to predict the pK_a. The errors in pK_a predictions of some cyclic, tertiary, and multihydroxy amine solutions were larger than that of the linear primary and secondary amines whether the original PDS or the updated PDS method was used. Another computer-free group-addition method (called QSSG) was proposed to predict the pK_a values of 73 CO₂-relevant alkanolamines/amines and cyclic amines, including piperazine and morpholine derivatives. Intramolecular hydrogen-bonding, hyperconjugation, solvent, and steric effects were analyzed. Six extra parameters were added, and 10 parameters were changed to improve the accuracy of the predicted pK_a values, based on a linear free energy relationship, of a training set of 73 amines for industrial CO₂ capture. The root-mean-square errors (rms) were 0.13 pK_a units for a set of 73 relevant industrial CO₂-capture amines. The rms errors in the pK_a values of nine multihydroxy amines were 0.45 for the original PDS, 0.28 for Sumon’s updated PDS method, and 0.12 for our QSSG method; for cyclic tertiary amines the corresponding values were 0.47, 0.22, and 0.12, respectively. The 10 amines outside the training set agreed well with the experimental results with QSSG predictions.