Biomass delignification with green solvents towards lignin valorisation: ionic liquids vs deep eutectic solvents

Abstract

The use of renewable resources as feedstocks to ensure the production of goods and commodities for society has been explored in the last decades to switch off the overexploited and pollutant fossil-based economy. Today there is a strong movement to set bioeconomy as priority, but there are still challenges and technical limitations that must be overcome in the first place, particularly on biomass fractionation. For biomass to be an appellative raw material, an efficient and sustainable separation of its major components must be achieved. On the other hand, the technology development for biomass valorisation must follow green chemistry practices towards eco-friendly processes, otherwise no environmental leverage over traditional petrochemical technologies will be acquired. In this context, the application of green solvents, such as ionic liquids (ILs) and deep eutectic solvents (DES), in biomass fractionation is envisaged as promising technology that encompasses not only efficiency and environmental benefits, but also selectivity, which is a crucial demand to undertake cascade processes at biorefinery level. In particular, this article briefly discusses the disruptive achievements upon the application of ILs and DES in biomass delignification step towards an effective and selective separation of lignin from polysaccharides. The different physicochemical properties of these solvents, their interactions with lignin and their delignification capacity will be scrutinized, while some highlights will be given to the important characteristics of isolated lignin fractions for further valorisation. The advantages and disadvantages between ILs and DES in biomass delignification will be contrasted as well along the article.

Acacia Wood Fractionation Using Deep Eutectic Solvents: Extraction, Recovery, and Characterization of the Different Fractions

“… 8 , 15 Other studies have focused on the extraction of lignin and purification of cellulose. 19 Recently, the effects of different wood origins (such as pine, acacia, sugarcane bagasse, corn stover, etc.) and extraction methods have been explored.…”

“…The acidity of these solvents is crucial for the breakage of the biomass matrix and lignin chemical bonds, particularly β-O-4 ether bonds, leading to the selective separation of lignin from cellulose structures. 19 This study aims at the selective extraction and characterization of cellulose and lignin that result from fractionation of acacia biomass with different green DES-based solvents. The relationship between the DES composition and chemical features and their extraction/selectivity performance will be further addressed.…”

“…In the literature, several studies can be found on the application of DESs in the extraction of aromatic hydrocarbons from alkanes or in the gasoline purification process. , Other studies have focused on the extraction of lignin and purification of cellulose . Recently, the effects of different wood origins (such as pine, acacia, sugarcane bagasse, corn stover, etc.)…”

“…It is also important to keep in mind that the structure of the isolated lignin is affected by the extraction methods and thus high-value products with different properties are possible to be formed. , The acid-based DESs are effective in dissolving technical lignins and can also lead to successful biomass delignification. The acidity of these solvents is crucial for the breakage of the biomass matrix and lignin chemical bonds, particularly β-O-4 ether bonds, leading to the selective separation of lignin from cellulose structures . This study aims at the selective extraction and characterization of cellulose and lignin that result from fractionation of acacia biomass with different green DES-based solvents.…”

Modeling of Pretreatment and Combined Alkaline and Enzymatic Hydrolyses of Blue Agave Bagasse in Corotating Twin‐Screw Extruders

“…that constitute the "platforms" or the products generated (energy or materials). [25] Chemical, mechanical and physical pretreatments, such as Organosolv, [26,27] extrusion, [28] steam explosion (SE), [29,30] and the use of high pressure [31,32] and ionic fluids [33][34][35] have been reported in the literature. SE is probably the most important pretreatment method because it is used in several industrial processes.…”