离子液体(ILs)-CO_2作为一种新型吸收制冷工质对,ILs种类的选择对其工质对性能及吸收式制冷循环特性至关重要。ILs对CO_2的吸收性能与ILs种类、阳离子结构、体系温度及CO_2分压有直接关系。本文建立了一套ILs吸收CO_2的实验台,并以低粘度、较优吸收性能为原则初选了4种咪唑双三氟甲磺酰亚胺盐ILs([emim][Tf_2N]、[bmim][Tf_2N]、[hmim][Tf_2N]和[omim][Tf_2N])为研究对象。在温度298.15 K、313.15 K及328.00 K,压力2.0~5.0 MPa条件下,分别测定了CO_2在以上4种ILs中的溶解特性。结果表明:咪唑双三氟甲磺酰亚胺盐ILs对CO_2有较好的吸收性能;CO_2在同族ILs中的溶解度随阳离子烷基链长度的增加而增大,其在4种ILs中的溶解度顺序为:[emim][Tf_2N]〈[bmim][Tf_2N]〈[hmim][Tf_2N]〈[omim][Tf_2N];随着温度和压力的逐渐升高,CO_2溶解度的变化幅度逐渐减小。本文还给出了3种温度下CO_2在[omim][Tf_2N]中的溶解度与压力的关联式。
The selection of ionic liquids( ILs) is crucial to the performance of new absorption working pairs( ILs-CO_2) and cycle characteristics of absorption refrigeration. The properties of ILs absorbing CO_2 are affected directly by ILs' s species,cation structure,temperature and CO_2 partial pressure. In this paper,an experimental system was designed and built to measure CO_2 solubility in the ILs. On the principle of low viscosity and better absorption performance,four imidazole bis trifluoromethanesulfonimide ILs( [emim][Tf_2N ],[bmim][Tf_2N],[hmim][Tf_2N]and [omim][Tf_2N]) were selected and the CO_2 solubility in them was measured within 2. 0 MPa to 5.0 MPa at 298. 15 K,313. 15 K and 328. 00 K,respectively. The results show that imidazole bis trifluoromethanesulfonimide ILs have a better performance of absorbing CO_2; the longer the alkyl chain of the same family ILs is,the larger the solubility is,and the CO_2 solubility increases in the order of [emim][Tf_2N][bmim][Tf_2N][hmim][Tf_2N][omim][Tf_2N]; the rangeability of CO_2 solubility decreases as the temperature and pressure gradually increase. The correlations of pressure and CO_2 solubility in [omim][Tf_2N] at three temperatures are also given.