CO2 absorption features of 1-ethyl-3-methylimidazolium ionic liquids with 2,4-pentanedionate and its fluorine derivatives
CO2 absorption features of 1-ethyl-3-methylimidazolium ionic liquids with 2,4-pentanedionate and its fluorine derivatives
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DOI：
10.1016/j.jcou.2019.02.020
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发表时间：
2019-05-01
影响因子：
7.7
通讯作者：
Kanakubo, Mitsuhiro
中科院分区：
文献类型：
--
作者：
Umecky, Tatsuya;Abe, Mitsutoshi;Kanakubo, Mitsuhiro
碱性2，4-戊二酮阴离子是一种新型的CO2化学吸收剂。然而，关于2，4-戊二酸盐离子液体的CO2吸收性能和物化性能的研究报道很少。本研究以2，4-戊二酮及其氟衍生物为原料，制备了1-乙基-3-甲基咪唑离子液体，1-乙基-3-甲基咪唑鎓 2，4-戊二酮盐（[C（2）mim] [acac]）、1-乙基-3-甲基咪唑鎓 1，1，1-三氟-2，4-戊二酮盐（[C（2）mim][tfacac]）和1-乙基-3-甲基咪唑鎓 1，1，1，5，5，5-六氟-2，4-戊二酮盐（[C（2）mim][hfacac]）。将上述离子液体与三种常规离子液体1-乙基-3-甲基咪唑乙酸盐（[C（2）mim] [AcO]）、1-乙基-3-甲基咪唑2，2，2-三氟乙酸盐（[C（2）mim][TFA]）和1-乙基-3-甲基咪唑双（[C（2）mim][TFA]）的H-1 NMR谱进行了比较。（三氟甲基磺酰基）酰亚胺（[C（2）mim][Tf 2N]）的研究表明，[C（2）mim]（+）阳离子（H2（c））的2-位氢原子与阴离子相互作用，相互作用的强度从[Tf_2N]（-）< [TFA]（-）到[tfacac]（-）再到[hfacac]（-）< [acac]（-）< [AcO]（-）。[C（2）mim][acac]和[C（2）mim][AcO]在常压下都能化学吸附CO2，但前者的CO2溶解度低于后者。另一方面，[C（2）mim][Tf 2N]、[C（2）mim][TFA]、[C（2）mim][tfacac]和[C（2）mim][hfacac]在相同条件下仅吸收可忽略量的CO2。[C（2）mim][acac]的化学吸附较小是由于H2（c）原子与[acac]（-）中氧原子的相互作用较弱。离子液体中的阳离子和阴离子之间的较强相互作用允许在CO2化学吸附的初始阶段吸引H2（c）原子。
Basic 2,4-pentanedionate anion is one of candidates for task-specific ionic liquids as CO2 chemical absorbents. However, there have been few reports on not only CO2 absorption but also physicochemical properties of 2,4-pentanedionate ionic liquids. In this study, we prepared 1-ethyl-3-methylimidazolium ionic liquids with 2,4-pentanedionate and its fluorine derivatives, i.e., 1-ethyl-3-methylimidazolium 2,4-pentanedionate ([C(2)mim] [acac]), 1-ethyl-3-methylimidazolium 1,1,1-trifluoro-2,4-pentanedionate ([C(2)mim][tfacac]), and 1-ethyl-3-methylimidazolium 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate ([C(2)mim][hfacac]). A comparison of H-1 NMR spectra among the above and three conventional ionic liquids, 1-ethyl-3-methylimidazolium acetate ([C(2)mim] [AcO]), 1-ethyl-3-methylimidazolium 2,2,2-trifluoroacetate ([C(2)mim][TFA]), and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([C(2)mim][Tf2N]), showed that the hydrogen atom at the 2-position of [C(2)mim](+) cation ( H2(c)) interacts with the anions, and the strength of the interaction increases in the order of [Tf2N](-) < [TFA](-) approximate to [tfacac](-) approximate to [hfacac](-) < [acac](-) < [AcO](-). [C(2)mim][acac] chemically absorbed CO2 as well as [C(2)mim][AcO] at atmospheric pressure, although the CO2 solubility of the former was lower than the latter. On the other hand, [C(2)mim][Tf2N], [C(2)mim][TFA], [C(2)mim][tfacac], and [C(2)mim][hfacac] absorbed only a negligible amount of CO2 under the same conditions. The smaller chemisorption of [C(2)mim][acac] is attributable to the weaker interactions of the H2(c) atom with the oxygen atoms of [acac](-). The stronger interaction between the cation and anion in the ionic liquids allows to draw the H2(c) atom at the initial stage of CO2 chemisorption.