Characterization of Hemicelluloses Obtained from Partially Delignified Eucalyptus Using Ionic Liquid Pretreatment

Abstract

Lignocellulosic biomass is a relatively inexpensive and abundant feedstock for biofuel production. The key to unlocking the recalcitrance of lignocelluloses is an effective pretreatment process. A promising new pretreatment method for lignocellulosic biomass is the use of ionic liquids (ILs). In this study, wood flour was partially dissolved in the novel ionic liquid 1-butyl-3-methylimidazolium acesulfamate ([BMIM]Ace) mixed with different organic solvents (1,4-dioxane, acetone, methanol, DMSO, and DMF) followed by precipitation in water. Hemicelluloses were successfully extracted from the carbohydrate-enriched residues by an alkaline ethanol solvent. Sugar analysis of the hemicellulosic fractions indicated that xylose (63.25-74.85%) was the major sugar component, while small amounts of glucose (4.85-14.40%) and galactose (4.49-7.32%) were also observed. Molecular weights of these fractions varied between 49.330 and 60.760 g/mol as determined by GPC. NMR studies revealed that the hemicelluloses had a backbone of β-(1→4)-linked-Dxylopyranosyl units and were branched mainly through 4-O-methyl-α-Dglucuronic acid. The thermal degradation behavior of the hemicellulosic fractions showed that the most significant degradation occurred between 242 and 300 °C. Chemistry and Technology, Beijing Forestry University, Beijing 100083, China; b: State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou 510640, China; *Corresponding author: rcsun3@bjfu.edu.cn Keywords: Pretreatment; Ionic liquid; Hemicelluloses; Characterization Contact information: a: Institute of Biomass INTRODUCTIONToday, the world's fossil fuel-based economy is facing problems and challenges. The depletion of fossil resources and global warming concerns have led to an intensified search for alternative resources to supply modern society. A potential solution to the problem is the utilization of lignocellulosic biomass as an alternative, sustainable energy source. Therefore, extensive research on the conversion of lignocellulosic biomass is currently being undertaken all over the world. In addition to its renewability, it can be used to produce chemicals and biofuels that do not compete with food production (Huber et al. 2006;Lynd et al. 1999). The term "lignocellulosic biomass" is often used to describe the material that composes the plant cell wall and is made up of cellulose, hemicelluloses, and lignin. In recent years, hemicelluloses have received greater attention because of their practical applications for bioconversion into fuels and chemicals.Hemicelluloses, the second most abundant constituent of lignocellulosic biomass, are not chemically well-defined compounds, but rather a family of polysaccharides, composed of different five-and six-carbon monosaccharide units (Rubin 2008). In general, hemicelluloses are mainly composed of pentoses (β-D-xylose, α-L-arabinose), PEER-REVIEWED ARTICLE bioresources.com Xu et al. (2013). "Ionic liquid pretreatment," BioResources 8(2), 1946-1962. 1947hexoses (β-D-mannos...

Fractionation and Structural Characterization of Hemicellulose from Steam-Exploded Banana Rachis

“…Several hemicellulose extraction techniques are described in the literature. Chemical extraction methods includes alkaline extraction [8,[10][11][12], soluble acid extraction [13,14] and ionic liquid extraction [15][16][17].…”

The Hydrolysis of Cellulosic Materials in Ionic Liquids

“…7). and 960-cm -1 regions, which is identified by specific vibration absorption of polysaccharides (Xu et al 2013).…”

“…A potential solution to the world's energy shortage is the utilization of lignocellulosic biomass as an alternative, sustainable energy source used to produce high value-added chemicals and biofuels (Xu et al 2013).…”

“…Studies have shown that ionic liquids can dissolve various types of agricultural biomass, such as rice husk (Ang et al 2011), corn stover (Kaar and Holtzapple 2000), switchgrass (Li et al 2010), and Eucalyptus species (Xu et al 2013).…”

Flax nanofibrils production via supercritical carbon dioxide pre‐treatment and enzymatic hydrolysis

“…Each pre‐treatment process has a different specificity on altering the physical and chemical structure of lignocellulosic materials. These various pre‐treatment processes can be broadly categorized into the following: Physical, such as mechanical processes and irradiation, which aim to increase the accessible surface area of lignocellulosic materials by reducing particle size or disrupting their structural regularity; Chemical, such as alkaline, dilute acid, oxidative delignification, organo‐solvent, and ionic liquids pre‐treatments, to partially solubilize hemicelluloses or/and lignin and improve the accessibility to the extraction of cellulosic fibres; Physico‐chemical, such as steam explosion, hydrothermal pre‐treatments, and ammonia and supercritical CO 2 explosion pre‐treatments . During these pre‐treatments, hemicelluloses and lignin are partially decomposed and solubilized and therefore removed from lignocellulosic materials.…”