# Fractionation of Lignocellulosic Biomass by Selective Precipitation from Ionic Liquid Dissolution
## 2 Materials and Methods  
All chemicals were of reagent grade and purchased from Meck Milipore Sigma-Aldrich (Darmstadt, Germany), except xylan (from beechwood), which was purchased from TCI-Europe, N. V. (Zwijndrecht, Belgium) and used without any further purification. The lignocellulosic biomass (barley straw) used was provided and characterized by the Biofuels Unit of CIEMAT. **Analysis of Barley Straw. ** The methods of characterization of barley straw are procedures adapted from the standard methods for the analysis of biomass published by the National Renewable Energy Laboratory (NREL; Colorado, USA) [56]. Determinations of extractives were made in quadruplicate, and component analysis of the collected samples was performed in triplicate. The average values for dried samples are summarized in Table 1. \begin{table}
\begin{tabular}{l l} \hline
**Extractives** & **13.37** \\ \hline Aqueous & 10.99 \(\pm\) 0.31 \\ Organic & 2.38 \(\pm\) 0.26 \\ \hline
**Cellulose** & **31.09 \(\pm\) 1.25** \\ \hline
**Hemicellulose** & **27.23 \(\pm\) 0.44** \\ \hline Xylose & 22.06 \(\pm\) 0.47 \\ Galactose & 1.3 \(\pm\) 0.01 \\ Arabinose + Mannose & 3.87 \(\pm\) 0.03 \\ \hline
**Insoluble Lignin** & **16.67 \(\pm\) 1.13** \\ \hline
**Soluble Lignin** & **2.1 \(\pm\) 0.03** \\ \hline
**Ash** & **3.89 \(\pm\) 0.05** \\ \hline
**Acetyl Goups** & **1.72 \(\pm\) 0.02** \\ \hline \end{tabular}
\end{table} 
Table 1: Composition analysis (wt.%) of samples of barley straw dried at 105 \({}^{\circ}\)C.  
**Dissolution and Precipitation. ** A total of 0.50 g of barley straw was dissolved in 9.50 g of ionic liquid (1-ethyl-3-methylimidazol acetate, [EMIMAcO]) at 105 \({}^{\circ}\)C in a Mettler-Toledo Easy Max 102\({}^{\circledR}\) reactor equipped with mechanical stirring at atmospheric pressure [34; 47; 57; 58]. Complete visual dissolution was observed at 3.5 h, and then the carbohydrate-rich material was precipitated by the addition of an antisolvent (25 mL). The antisolvents tested were water, acetone and mixtures thereof. The obtained Solid I was separated by vacuum filtration with a nylon membrane (20 \(\mu\)L) such that the lignin dissolved in the ionic liquid (IL) was not retained in the filter. The filtered solid, which was rich in carbohydrates, was washed several times with distilled water to remove the remaining IL. Solid II (carbohydrate-free lignin) was recovered by evaporation of acetone, vacuum filtration with a nylon membrane (0.2 \(\mu\)L) and washing with distilled water (Figure 1). The scheme of the dissolution process of barley straw in the ionic liquid [EMIMAcO] and subsequent precipitation with mixtures of water:acetone is shown in Figure 1, which shows the methods used to obtain the two types of solids. Solid I (rich in cellulose and hemicellulose) was obtained after Filtration I, and Solid II (rich in lignin) was obtained after Filtration II from the liquid obtained in the first filtration after the evaporation of acetone. **Hydrolysis. ** Hydrolysis reactions were carried out batchwise in a magnetically stirred 100 mL thermostatic Teflon-lined steel Berghof reactor equipped with a pressure addition funnel [33; 34; 57]. In a typical run, 0.5 g of barley straw and 40 mL of water were mixed in the reactor, the suspension was heated to the reaction temperature (140 \({}^{\circ}\)C), and 10 mL of H\({}_{2}\)SO\({}_{4}\) (0.2 mol/L) was added to the reactor. These are the optimal conditions obtained from previous works [33; 57]. The reaction time was measured from this moment; the reaction was stopped at 5 h, and the suspension was quickly cooled. Aliquots were periodically taken from the reactor. The solution was filtered off and washed with distilled water, and finally, the solid was dried at 80 \({}^{\circ}\)C overnight. The amount of solid isolated was determined by weighing. The liquid was analyzed by HPLC (Agilent Technologies (Santa Clara, California, USA) HPLC 1200 and 1260 series).