Rapid pretreatment of Miscanthus using the low-cost ionic liquid triethylammonium hydrogen sulfate at elevated temperatures

Abstract

Deconstruction with low-cost ionic liquids (ionoSolv) is a promising method to pre-condition lignocellulosic biomass for the production of renewable fuels, materials and chemicals. This study investigated process intensification strategies for ionoSolv pretreatment of Miscanthus × giganteus with the low-cost ionic liquid triethylammonium hydrogen sulfate ([TEA] [HSO 4 ]) in the presence of 20 wt% water, using high temperatures and a high solid to solvent loading of 1 : 5 g/g. The temperatures investigated were 150, 160, 170 and 180°C. We discuss the effect of pretreatment temperature on lignin and hemicellulose removal, cellulose degradation and enzymatic saccharification yields. We report that very good fractionation can be achieved across all investigated temperatures, including an enzymatic saccharification yield exceeding 75% of the theoretical maximum after only 15 min of treatment at 180°C. We further characterised the recovered lignins, which established some tunability of the hydroxyl group content, subunit composition, connectivity and molecular weight distribution in the isolated lignin while maintaining maximum saccharification yield. This drastic reduction of pretreatment time at increased biomass loading without a yield penalty is promising for the development of a commercial ionoSolv pretreatment process.

Combining Cost‐Efficient Cellulose and Short‐Chain Carboxylic Acid Production: The Polyoxometalate (POM)‐Ionosolv Concept

“…An on‐going challenge for ionosolv technology is deriving stable value from the hemicellulose. In the acidic [HSO 4 ]‐containing ionic liquid medium, hemicellulose sugars are either isolated as furfural or form humins . Separating dissolved hemicellulose sugars from the ionic liquid is feasible but requires expensive column chromatography .…”

“…In the acidic [HSO 4 ]-containing ionic liquid medium, hemicellulose sugars are either isolated as furfural or form humins. [21,24] Separating dissolved hemicellulose sugars from the ionic liquid is feasible but requires expensive column chromatography. [25] While furfural is a valuable chemical, used as a reactive solvent or starting material for furfuryl resins, its market is relatively small (~300 kt) and could easily be oversaturated if several new biorefineries produced substantial amounts of furfural.…”

Ionic Liquids in Biomass Processing

“…The use of neutral ionic liquids such as 1‐butyl‐3‐methylimidazolium chloride and 1‐ethyl‐3‐methylimidazolium acetate results in minimum depolymerization of polysaccharides during the pretreatment . On the other hand the use of acidic ionic liquids in the pretreatment of biomass may result in some depolymerisations, especially in the hemicellulose fraction . The use of ILs with a co‐solvent such as DMSO, DMF, alcohols and also with a controlled amount of water is also known …”

“…On the other hand the use of acidic ionic liquids in the pretreatment of biomass may result in some depolymerisations, especially in the hemicellulose fraction . The use of ILs with a co‐solvent such as DMSO, DMF, alcohols and also with a controlled amount of water is also known …”

“…[64,65,66,67] On the other hand the use of acidic ionic liquids [52] in the pretreatment of biomass may result in some depolymerisations, especially in the hemicellulose fraction. [68] The use of ILs with a co-solvent such as DMSO, DMF, [64] alcohols [69] and also with a controlled amount of water is also known. [68] Moyer and co workers have studied the relationship between lignocellulosic biomass solubility and pretreatment properties of a series of ionic liquids.…”