1. Biomass fractionation using Deep Eutectic Solvents
Ir. Laura Kollau

2. Deep Eutectic Solvents (DESs) are Low Transition Temperature Mixtures (LTTMs) consisting of at least one Hydrogen Bond Donor (HBD) and one Hydrogen Bond Acceptor (HBA) which results in a liquid mixture showing an unusual low melting point.
ΔT ≈ 300°C
0:1
1:2
1:1
2:1
1:0
Melting point of Choline Chloride/ Urea mixture as a function of the composition
Left: A.P. Abbott et al. J. Am. Chem. Soc., 2004;

3. Due to the high hydrogen bonding interactions, some of the promising characteristics of ionic liquids are shared by DESs, for example:
Wide liquid range
Low of negligible vapor pressure
Good solvation properties
Water can be used as anti-solvent
Ability to customize properties as a function of:
DES constituents nature
DES constituents ratio
Water content
Temperature
Malic Acid + Choline Chloride mixtures showing the phase transition for different HBD:HBA ratios at RT

4. Additionally, unlike ionic liquids, DESs possess a number of beneficial properties:
Easy Preparation
Readily available and inexpensive starting materials
No need of purification
Water compatibility
Non-flammability
Non-toxicity
Biocompatible
Biodegradable
Considered environmentally benign solvents
Melting point of Choline Chloride / Organic acid mixtures as a function of composition.

5. The constituents can be selected to keep the right functionalities to pursuit the best performance for a certain application.
DESs can be formed by mixing HBA, e.g. amino acids and salts, with HBD, e.g. acids alcohols and amines.
The proton affinity (pKa) plays a role in the strength of the H-bond.
The lower acidity of the HBD is also responsible for the formation of DES instead of an ionic liquid.

6. So far, various constituents have already proven to result in DESs.
Examples of combinations of HBD : HBA which were forming (green) or not (red) a clear liquid upon mixing and heating at ºC depending on viscosity
DSC curves for some representative mixtures described in the screening table:
Glass Transition Temperature instead of melting point

7. Hypothesis: DESs are formed in plant cells in periods of water scarcity, as a substitute for water. Hence, high solubilities for plant metabolites, like biopolymers and CO2, are expected.
Cellulose
Lignin
Hemicellulose

8. In a number of DESs the solubility of lignin has been tested.

9. The process of lignin extraction on lab-scale.
60 or 85 °C
Overnight
Vigorous stirring
+ 10 g LTTM

10. Separation of the cellulose rich biomass and the lignin-containing DESs.
Centrifuge
Supernatant
Biomass
Precipitated BM
(Lignin)
Washed BM
(HC-rich)
Filtration

11. The cellulose rich biomass is washed and filtrated, resulting in clean biomass.
Filtration
Mainly cellulose (pulp)
Biomass washing

12. The lignin is precipitated from the DESs and filtrated.
Lignin Precipitation upon water addition
Filtration

13. Regeneration of the DES is possible upon anti-solvent addition, e. g
Regeneration of the DES is possible upon anti-solvent addition, e.g. ethanol
Malic Acid + Glycine (1:1)
2 mL Ethanol / 1.5 gr DES
9 mL Ethanol / 1.5 gr DES

14. Final Goal: Integration of DESs in Pulp Mill / Biorefinery.
Lignocellulosic biomass
Lignin
Pulp
HC-enriched biomass
Catalytic Hydrolysis
Enzymatic Hydrolysis
Sugars for fermentation

15. Thank You