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DFT Study on Thermodynamic Parameters of CO2 Absorption into Aqueous Solution of Aliphatic Amines
Monireh Hajmalek,Hossein Aghaie*,Karim Zare,Mehran Aghaie
Author NameAffiliationE-mail
Monireh Hajmalek Department of Chemistry, Science and Research Branch, Islamic Azad University, Tehran, Iran  
Hossein Aghaie* Department of Chemistry, Science and Research Branch, Islamic Azad University, Tehran, Iran h.aghaie@srbiau.ac.ir, hn aghaie@yahoo.com 
Karim Zare Department of Chemistry, Science and Research Branch, Islamic Azad University, Tehran, IranDepartment of Chemistry, Faculty of Science, Shahid Beheshti University, Tehran, Iran  
Mehran Aghaie Faculty of Chemistry, North Tehran Branch, Islamic Azad University, Tehran, Iran  
Abstract:
Using density functional theory (DFT), the thermodynamic parameters of the CO2 absorp-tion into the aqueous solution of the aliphatic amines including some alkylamines, alka-nolamines, diamines and a type of aminoamide were calculated. The geometry optimiza-tion and the calculation of vibrational frequencies in the gas phase were performed at the B3LYP/6-311+ G(d,p) level of theory. Moreover, the standard solvation free energies of the studied species were computed upon the solution phase optimized geometries through the latest continuum solvation model (SMD/IEF-PCM) at the HF/6-31G(d) level of theory. With this approach, two important properties of the CO2 absorption into the aqueous so-lutions of the studied amines were evaluated: the acid dissociation constant (pKa) of the parent amines and the standard enthalpy change (ΔH?abs) related to the CO2 absorption process. A roughly linear relationship was observed between pKa and ΔH?abs. This finding suggests that a raise in the basicity of an amine leads to an increase in the heat released in CO2 absorption and consequently in the required energy for the regeneration of amine.
Key words:  Density functional theory, Amine, CO2 absorption, Heat of absorption, SMD solvation model
FundProject:
脂肪胺水溶液吸收CO2的热力学参数的密度泛函理论研究
Monireh Hajmale,Hossein Aghaie*,Karim Zare,Mehran Aghaie
摘要:
采用密度泛函理论研究CO2在脂肪胺水溶液热力学参数.研究的脂肪胺包括烷基胺、链烷醇胺、二胺以及氨基酰胺.在B3LYP/6-311+ G(d,p)水平计算脂肪胺在CO2气相中的振动频率.通过连续介质模型在HF/6-31G(d)水平计算了溶剂几何优化的标准自由能,评价了CO2吸收到脂肪胺水溶液过程有关的两个重要参数:酸解离常数和标准焓变二者之间大致呈线性关系.随着胺碱度的提高,CO2吸收过程释放的热量增加,则胺再生所需的能量增加.
关键词:  密度泛函理论,脂肪胺,CO2吸收,吸收热,连续介质模型
DOI:10.1063/1674-0068/27/06/672-678
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