Pentafluoroethane Dehydration with Ionic Liquids

Ionic liquids (ILs) were proposed as promising separating agents for the hydrofluorocarbons (HFCs) pentafluoroethane (R125) dehydration. Taking into account the H2O solubility and selectivity of H2O to R125 in a variety of IL candidates, we determined the hydrophilic [EMIM]­[BF4] as a satisfactory absorbent. Besides, some theoretical insights into separation mechanism at the molecular level were explored by means of the combination of COSMO-RS model and quantum chemistry calculation. The gas–liquid equilibrium (GLE) data for the binary R125-[EMIM]­[BF4] and ternary R125-H2O-[EMIM]­[BF4] systems were measured, and the experimental data were compared with the predicted results by COSMO-RS model. The R125 dehydration experiment with IL was carried out. Furthermore, the continuous processes for R125 dehydration with [EMIM]­[BF4] and the conventional benchmark solvent tetraethylene glycol (TeEG) as absorbents were simulated and optimized with the rigorous equilibrium (EQ) stage model, in which COSMO-SAC model was selected. It was confirmed that the R125 gas dehydration with IL presented in this work is a typical process intensification technology.本研究提出将离子液体（Ionic liquids, ILs）作为氢氟烃（hydrofluorocarbons, HFCs）五氟乙烷（pentafluoroethane, R125）脱水工艺的高性能分离介质。基于多种候选离子液体对水的溶解度以及水对R125的选择性，我们筛选出亲水性的[EMIM][BF4]作为适宜的吸收剂。此外，结合COSMO-RS模型与量子化学计算，从分子层面深入探究了该分离过程的理论机制。本研究测定了二元体系R125-[EMIM][BF4]与三元体系R125-水-[EMIM][BF4]的气液平衡（gas–liquid equilibrium, GLE）数据，并将实验结果与COSMO-RS模型的预测值进行了对比验证。随后开展了基于离子液体的R125脱水实验。进一步地，采用COSMO-SAC模型，借助严格平衡级模型，对以[EMIM][BF4]与常规基准溶剂四甘醇（tetraethylene glycol, TeEG）作为吸收剂的R125连续脱水工艺进行了模拟与优化。最终证实，本研究采用离子液体进行R125气体脱水属于典型的过程强化技术。