(393b) Extractive Distillation with Ionic Liquids: Continuous Vs. Batch Operation
AIChE Annual Meeting
2023
2023 AIChE Annual Meeting
Computing and Systems Technology Division
Sustainable Process Synthesis, Design, and Intensification
Wednesday, November 8, 2023 - 3:48pm to 4:06pm
In BED operation, both the solvent and the azeotropic mixture are fed at the still pot (i.e., the reboiler) at the beginning of the operation [6]. Then the still pot is heated to create the vapor-liquid equilibrium. Due to its low vapor pressure, IL solvents may fail to attain the required separation purity in BED operation. To examine the feasibility of ILs in BED, we have investigated two different configurations, batch still pot without any stages and with multiple stages. Additionally, we have also investigated a semi-batch process where the ILs are fed to the column continuously from the top. While separating the azeotropic refrigerant mixture R-410A, both batch configurations fail with IL as the solvent. Conversely, the semi-batch configuration attains more than 99 wt.% product purity. However, it requires a significantly higher amount of IL and heat duty compared to a continuous process. We have also investigated the feasibility of the BED process for the dehydration of ethanol with both organic solvent and IL. Our results show that while the organic solvent, ethylene glycol can produce higher-purity ethanol in a BED process, the IL-based process fails to attain the required purity. The main difficulty of IL-solvents is that they do not vaporize and so the additional stages above the still pot (or reboiler) are not used. This summarizes the fact that ILs are not a feasible entrainer in BED operation for any azeotropic separations. In order to take advantage of ILs, the process must be converted into a scaled-down continuous process. In this work, we have also investigated the economic feasibility of the scaled-down continuous ED process.
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