(442e) Ionic Liquid Design and Techno-Economic Evaluation for Energy Efficient Extractive Recovery of Bio-Based Glycols

Important bulk chemicals like glycols can be produced from renewable sources through fermentation processes. An important challenge is the energy efficient product recovery from diluted fermentation broths. Low molecular weight diols, such as Mono Ethylene Glycol, Propylene Glycols and Butane Diols are particularly difficult to separate due to their high water affinity. Their recovery by distillation or multiple effect evaporation is associated with high energy consumption. Liquid-Liquid extraction can be a promising alternative since it can be much more energy efficient. However, for conventional solvents the distribution coefficients are generally insufficient to achieve efficient extraction at low broth concentrations. For this reason advanced fluid extractants like ionic liquids are needed that improve the glycol distribution.

In this work COSMO-RS is used to support ionic liquid tailoring to optimize the glycol distribution coefficient (D) and selectivity (S) by employing the sigma electron profile. As a result the glycol distribution coefficients were increased up to >100 times that of conventional solvents. For the best performing ionic liquid tetraoctyl ammonium 2-methyl-1-napthoate liquid-liquid equilibrium data were determined and thermodynamic models constructed for various glycols. These thermodynamic models were used to develop conceptual process designs that demonstrated energy savings >50% compared to the current state-of-the-art three effect evaporation technology. Energy integration appeared crucial to achieve these energy savings in the extraction process. In spite of these significant energy savings the techno-economic evaluation demonstrated that the final economic feasibility of the extraction routes strongly depends on the capital expenditure for the respective glycols, which in turn is strongly dependent on the final glycol distribution coefficient achieved.