Biomass fractionation using Deep Eutectic Solvents Ir. Laura Kollau

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;

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

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.

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.

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 60-100ºC depending on viscosity DSC curves for some representative mixtures described in the screening table: Glass Transition Temperature instead of melting point

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

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

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

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

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

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

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

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

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