학술논문
多元胺-TFSA型质子化离子液体吸收CO2的理论分析 / Theoretical analysis of CO2 absorption by polyamines-TFSA type protic ionic liquids
Document Type
Academic Journal
Source
化工进展 / Chemical Industry and Engineering Progress. 42(11):6015-6030
Subject
Language
Chinese
ISSN
1000-6613
Abstract
开展了以质子化的正己胺(HHexam+)、己基乙二胺(HHexen+)及己基二亚乙基三胺(HHexdien+)为阳离子的TFSA[＝(CF3SO2)2N-]型质子化离子液体(PILs),即[Hhexam][TFSA]、[Hhexen][TFSA]及[Hhexdien][TFSA]型PILs吸收CO2的研究.首先,选择密度泛函理论,在M06-2X/6-311G(d,p)水平下,对上述3种PILs的构型进行优化,分别得到了其较稳定构象,结果显示,PILs的阳离子中N—H和阴离子中N原子间主要形成N—H···N型较强氢键.然后,分别利用其中最稳定构象,创建并优化PILs-Nco2构型,PILs和Nco2分子间主要形成N—H···O型弱或中等强度氢键.主要氢键部位N—H···O中N—H键的振动频率的变化值、电子密度值及二阶微扰能的计算结果显示,[Hhexam][TFSA]、[Hhexen][TFSA]及[Hhexdien][TFSA]分别与2、3、4分子CO2结合时将不再形成氢键网络.采用COSMOtherm软件计算的CO2 在3种PILs中的亨利常数(kPa)大小为[Hhexam][TFSA](1.91×104)>[Hhexen][TFSA](1.68×104)>[Hhexdien][TFSA](1.51×104),即3种PILs对CO2的溶解能力大小为极性头部具有3个氨基的[Hhexdien][TFSA]>2个氨基的[Hhexen][TFSA]>1个氨基的[HHexam][TFSA].以上结果中可以看出,PILs结构中氨基数目的多少对其吸收CO2的能力有较显著影响,即随着PILs结构中氨基数目的增多,其对CO2的溶解能力随之增大.
Three protic ionic liquids(PILs)composed of the same anion of[TFSA＝(CF3SO2)2N-]and different cations of N-hexylammonium(HHexam+),monoprotic hexylethylenediaminium(Hhexen+)and hexyldiethylenetriaminium(Hhexdien+),[HHexam][TFSA],[Hhexen][TFSA],and[Hhexdien][TFSA]were studied for the absorption of CO2.First,the more stable configurations of the three PILs were optimized via the M06-2X/6-311G(d,p)of the density functional theory.The results indicated that the stronger N—H···N-type hydrogen bonds were formed mainly between the N-atoms in the cations and the N-atoms in the anion of the PILs.Then,the configurations of PIL-Nco2 were optimized.The N—H···O-type weak-or moderate-strength hydrogen bonds were formed mainly between the N—H bond in the cation of the PIL and the O atoms of CO2.The results of the vibrational frequency of the N—H bond,and the electron density and the second-order perturbation energy of N—H···O showed that a single molecule of[HHexam][TFSA],[Hhexen][TFSA]and[Hhexdien][TFSA]was saturated when bonded with 2,3 and 4 CO2 molecules,respectively.Meanwhile,the results calculated by COSMOtherm software found that the Henry constants(kPa)for CO2 in the three PILs varied as 1.91×104 for[HHexam][TFSA]>1.68×104 for[Hhexen][TFSA]>1.51×104 for[Hhexdien][TFSA],indicating that the solubility of CO2 in the PILs followed the order of[Hhexdien][TFSA]with three amino groups in the polar head>[Hhexen][TFSA]with two amino groups>[HHexam][TFSA]with one amino group.These results suggested that the number of amino groups in the PIL structure had a significant effect on its ability to absorb CO2.With increasing number of amino groups in the structure of PILs,its solubilization capacity for CO2 increased.
Three protic ionic liquids(PILs)composed of the same anion of[TFSA＝(CF3SO2)2N-]and different cations of N-hexylammonium(HHexam+),monoprotic hexylethylenediaminium(Hhexen+)and hexyldiethylenetriaminium(Hhexdien+),[HHexam][TFSA],[Hhexen][TFSA],and[Hhexdien][TFSA]were studied for the absorption of CO2.First,the more stable configurations of the three PILs were optimized via the M06-2X/6-311G(d,p)of the density functional theory.The results indicated that the stronger N—H···N-type hydrogen bonds were formed mainly between the N-atoms in the cations and the N-atoms in the anion of the PILs.Then,the configurations of PIL-Nco2 were optimized.The N—H···O-type weak-or moderate-strength hydrogen bonds were formed mainly between the N—H bond in the cation of the PIL and the O atoms of CO2.The results of the vibrational frequency of the N—H bond,and the electron density and the second-order perturbation energy of N—H···O showed that a single molecule of[HHexam][TFSA],[Hhexen][TFSA]and[Hhexdien][TFSA]was saturated when bonded with 2,3 and 4 CO2 molecules,respectively.Meanwhile,the results calculated by COSMOtherm software found that the Henry constants(kPa)for CO2 in the three PILs varied as 1.91×104 for[HHexam][TFSA]>1.68×104 for[Hhexen][TFSA]>1.51×104 for[Hhexdien][TFSA],indicating that the solubility of CO2 in the PILs followed the order of[Hhexdien][TFSA]with three amino groups in the polar head>[Hhexen][TFSA]with two amino groups>[HHexam][TFSA]with one amino group.These results suggested that the number of amino groups in the PIL structure had a significant effect on its ability to absorb CO2.With increasing number of amino groups in the structure of PILs,its solubilization capacity for CO2 increased.