Green Processing of Lignocellulosic Biomass and Its Derivatives in Deep Eutectic Solvents

Abstract

The scientific community has been seeking cost-competitive and green solvents with good dissolving capacity for the valorization of lignocellulosic biomass. At this point, deep eutectic solvents (DESs) are currently emerging as a new class of promising solvents that are generally liquid eutectic mixtures formed by self-association (or hydrogen-bonding interaction) of two or three components. DESs are attractive solvents for the fractionation (or pretreatment) of lignocellulose and the valorization of lignin, owing to the high solubility of lignin in DESs. DESs are also employed as effective media for the modification of cellulose to afford functionalized cellulosic materials, such as cellulose nanocrystals. More interestingly, biomassderived carbohydrates, such as fructose, can be used as one of the constituents of DESs and then dehydrated to 5-hydroxymethylfurfural in high yield. In this review, a comprehensive summary of recent contribution of DESs to the processing of lignocellulosic biomass and its derivatives is provided. Moreover, further discussion about the challenges of the application of DESs in biomass processing is presented.

Deep Eutectic Solvent Aqueous Solutions as Efficient Media for the Solubilization of Hardwood Xylans

“…The eutectic mixture composed of choline chloride and urea has attracted significant attention as a reference DES owing to its unique properties . The properties of DESs, along with their straightforward preparation, make them an ideal medium for a variety of applications, such as catalysis, organic synthesis, electrochemistry, materials chemistry, and extraction processes, including biomass fractionation and processing …”

A Bibliometric Study of Scientific Publications regarding Hemicellulose Valorization during the 2000–2016 Period: Identification of Alternatives and Hot Topics

“…In a similar way to the application of ionic liquids, research about deep eutectic solvents for biomass fractionation has been focused on the dissolution of cellulose and lignin and the extraction of these constituents from lignocellulosic biomass [156]. These solvents have displayed outstanding performance for the dissolution of lignin, whereas cellulose can barely be dissolved [157]. The combination of deep eutectic solvents and microwave irradiation had a significant synergetic effect on efficiently cleaving the lignin-carbohydrate complex [141].…”

Development of Betaine‐Based Sustainable Catalysts for Green Conversion of Carbohydrates and Biomass into 5‐Hydroxymethylfurfural

“…This was probably because the solubility of microcrystalline cellulose decreased in the presence of the DES system, which was formed by hydrogen‐bond donors and acceptors such as ChCl, AlCl 3. 6H 2 O, H 2 O and the produced glucose, fructose and HMF . Encouraged by all the above results, we proceeded to convert lignocellulosic biomass directly into HMF and furfural, which would be a more cost‐effective process.…”