Bachelor Assignments

Deep Eutectic Solvent Screening for Aromatic-Aliphatic Separations

BSc-project description tutor: Thomas Brouwer

Supervisor: Boelo Schuur

Deep Eutectic Solvent Screening for Aromatic-Aliphatic Separations

Sometimes, distillation is impractical to separate mixtures due to high energy consumption, or even it might be impossible due to azeotropes. Alternatively, affinity separation processes such as extractive distillation (ED) and Liquid-Liquid Extraction (LLX) can be applied. The separation of aromatic from aliphatic compounds is one example where ordinary distillation can be impractical. The addition of an affinity agent, or solvent, can bring a solution by increasing the relative volatility or even breaking azeotropes.

This BSc-project is part of a larger project where we try to understand molecular interactions between solvents and mixtures that we want to separate. In order to do so, we study both common solvents such as sulfolane that have been industrially used for decennia already and innovative new solvents. Deep Eutectic Solvents (DES) are a relatively new concept [1, 2], they consist of two solids that upon mixing become a liquid, because the melting point of the mixture is significantly lower than the melting points of the two constituents. Additionally, It is possible to make DESs from biobased molecules making it a potential green solvent.


To increase the understanding of using Deep Eutectic Solvents (DES) in extraction processes, and in particular aromatic-aliphatic extractions, a large amount of different DESs has to be created and analyzed. In the end, we want to understand the effect of changing the molecular structure of the DES to the extraction performance. In this Bsc-project we will start with the investigation of 2 hydrogen bond donors and 2 hydrogen bond acceptors, namely;

Hydrogen Bond Acceptors (HBA)

Hydrogen Bond Donors (HBD)

Glycine


L-Lactic acid


Alanine


Levulinic acid

We will attempt to create DESs with these four possible combinations by mixing them in various ratios. However, it may be possible to investigate even more DESs with different HBA or HBD. The newly made DESs will be characterized with:

  • a)FT-IR to investigate the hydrogen bonding in the DES.
  • b)Melt point determination with glycol bath.
  • c)Karl-Fischer Titration to determine the water content of the DES.

The extraction potential of the newly made DESs in aromatic-aliphatic mixtures will be investigated by liquid-liquid extraction (LLX) of a model system, n-heptane-toluene. The LLX extraction experiments will be analyzed with the Gas Chromatograph (GC).

Objectives:

  • 1.1.Literature study on affinity agents, e.g. solvents, of close boiling mixtures, in particular aliphatic-aromatic mixtures.
  • 1.2.Literature study on affinity agents separation processes, e.g. Extractive Distillation, Liquid-Liquid Extraction.
  • 1.3.Literature study on Deep Eutectic Solvents (DESs)
  • 1.4.Obtaining the partition coefficients, KD, and selectivity’s, S, for all DESs
  • 1.5.Compare the KD and S of all DESs and explain according to the molecular structure of the DES.
  • 1.6. Give the potential of these DESs in affinity agents separation processes.

References:

[1] Y. Wang, Y. Hou, W. Wu, D. Liu, Y. Ji, S. Ren, Roles of a hydrogen bond donor and a hydrogen bond acceptor in the extraction of toluene from n-heptane using deep eutectic solvents, Green Chemistry, 18 (2016) 3089-3097.

[2] M. Francisco, A. van den Bruinhorst, M.C. Kroon, New natural and renewable low transition temperature mixtures (LTTMs): screening as solvents for lignocellulosic biomass processing, Green Chemistry, 14 (2012) 2153-2157.