Screening of Deep Eutectic Solvents (DES) for the fractionation/delignification

Screening of Deep Eutectic Solvents (DES) for the fractionation / delignification


The aim of this project was to develop a fast screening process to study the delignification capability of novel Deep Eutectic Solvents. Although acidic, basic and neutral conditions were studied, the focus was especially on neutral and alkaline systems. Fast screening was done using a heat block system and different analytical methods to determine the lignin content were studied.

Not all studied solvents did stand alkaline conditions (as imposed by adding alkaline additives) and degradation was observed. The best method to determine the lignin content was conventional composition analysis which is rather time consuming analysis. A lot faster method, UV-Vis spectroscopy at 280 nm, resulted in too high yields for soluble lignin. It is assumed that the degradation products are interfering the absorption.

The tested alkaline systems were able to dissolve up to 25 % of original lignin based on conventional composition analysis of the undissolved wood meal. Although solvent systems were able to delignify to some extent, the delignification degree was not enough to produce separated fibres. The solvent systems were not particularly selective towards lignin (also hemicellulose was dissolved). To continue with alkaline systems, the solvent system is advised to:

  • Have good delignification ability
  • Be selective for lignin
  • Tolerate alkaline conditions

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