# Fractionation of Lignocellulosic Biomass by Selective Precipitation from Ionic Liquid Dissolution
###### Abstract  
We propose the treatment of barley straw with 1-ethyl-3-methylimidazolium acetate [EMIMAcO] ionic liquids (ILs) and subsequent precipitation with antisolvent mixtures, thus allowing the separation of the sugar-rich fractions (cellulose and hemicellulose) from the lignin fraction. For this purpose, different concentration ranges of acetone:water antisolvent mixtures were studied. In all cases, a high recovery percentage and a high and effective separation of fractions was achieved for 1:1 acetone:water. The fractionated lignocellulosic compounds were studied by using infrared spectroscopy, scanning electron microscopy and \({}^{1}\)H nuclear magnetic resonance characterization techniques. This method allows the possibility of reusing IL, confirming the versatility of the established method. The fraction rich in cellulose and hemicellulose was subjected to acid hydrolysis (0.2 mol/L H\({}_{2}\)SO\({}_{4}\)) for 5 h at 140 \({}^{\circ}\)C, obtaining a yield of total reducing sugars of approximately 80%, much higher than those obtained in non-pretreated samples.  
l g  
fractionate the lignocellulosiculose [10; 12; 13; 14; 15; 16; 17]. The presence of lignin is considered to be a major barrier to achieving efficient cellulosic bioconversion because of its negative interaction with the biocatalyst during enzymatic hydrolysis and microbial fermentation [18; 19]. Lignin acts as a cement around cellulose fibrils, and it is difficult to separate the two components. Typically, harsh conditions are used, causing chemical and structural changes [20]. Once lignin is isolated as a solid (technical lignin), the resulting material is even more recalcitrant than its native state. One of the more interesting lignocellulosic residues are barley wastes. These residues are the second largest biomass feedstock in Europe [21; 22]. The estimated amounts of environmental sustainable of barley straw in the European Union for 2030 are 25 million tons [23].  
Ionic liquids (ILs) are effective in solubilizing crystalline cellulose and lignocellulosic biomass [24; 25; 26; 27; 28; 29; 30; 31; 32], and dissolved cellulose can be regenerated by precipitation with antisolvents. Interestingly, regenerated cellulose shows lower crystallinity and enhanced subsequent hydrolysis rates [33; 34]. ILs can also deconstruct and fractionate lignocellulosic. Once lignocellulosic biomass is dissolved, it can be fractionated into its principal components by the addition of antisolvents, which leads to the selective precipitation of lignin, cellulose or hemicellulose [35; 36; 37; 38; 39; 40; 41]. There is a plethora of studies of IL dissolution of lignocellulosic biomass, where ionic liquids of the imidazolium type are the best solvents [33; 42; 43; 44; 45; 46; 47]. Among them 1-ethyl-3-methylimidazol acetate [EMIMAcO] is the most popular, because of his physical properties (low boiling point and viscosity) and chemical properties, absence of halogen as an anion, is not corrosive and practically no reactive with the biomass [30; 48; 49; 50; 51; 52; 53; 54].  
In this work, we studied the dissolution of barley straw in [EMIMAcO] and subsequent precipitation with different concentrations of water:acetone mixtures to improve the fractionation of lignocellulosic biomass. This combination may be interesting because the presence of water favors the precipitation of all the main components of biomass (cellulose, hemicellulose and lignin), while acetone does not favor the precipitation of lignin, according to the literature [55].