# Fractionation of Lignocellulosic Biomass by Selective Precipitation from Ionic Liquid Dissolution
## 3 Results and Discussion
### Catalytic Activity
This fact indicates that the pretreated sample (Solid I) can more easily hydrolyze hemicellulose, obtaining a higher yield of xylose more quickly, although the differences are less evident than with glucose (Figure 12A). This is because hemicellulose (polymer of origin of xylose) is much easier to hydrolyze than glucose and, therefore, even without treatment, hydrolysis can be effectively performed. In addition, presenting behavior typical of an intermediate reaction compound in consecutive reactions, the source of the  
Figure 12: Yield of glucose (**A**) and levulinic acid (**B**) from the hydrolysis of cellulose, untreated barley straw and barley straw treated (Solid I) with [EMIMAcO]. xylose is consumed when in contact with the acid catalyst in the medium; then, dehydration takes place, and the material is transformed into furfural (Figure 13B). The furfural yield profiles indicate that the yield increases with reaction time, reaching, 36% with Solid I and 20% with untreated barley straw at 5 h. The Solid I sample had a higher concentration because the xylose concentration was higher than in the untreated sample. In the hydrolysis process, the polymeric chains of cellulose and hemicellulose become smaller, and some of them become soluble in water; therefore, the reaction medium not only contains monomers such as glucose or xylose but can also contain oligomers with several units that are soluble. For this reason, we analyzed the final reaction samples and calculated the total reducing sugars (TRS) content, including the sugars in monomeric and oligomeric forms. The obtained results are shown in Table 4. The values of TRS are clearly higher than those obtained by the sum of sugars measured with HPLC (monomeric), which indicates that in the reaction medium, there is an appreciable amount of oligomeric sugars; this discrepancy is more evident for straw samples (original and Solid I). The yield to sugars decreases according to the order Solid I\(>\) original barley straw \(>\) cellulose, which coincides with the conversion values described in Table 3. However, the selectivity of total reducing sugars does not follow this trend (Table 4). It is clear that the selectivity of TRS is much higher for the Solid I sample than the untreated samples of cellulose and barley straw. The combination of high conversion and high selectivity in the Solid I sample produced one of the highest sugar yields in acid catalyzed hydrolysis of lignocellulosic biomass among those described in the literature [72; 73; 74; 75; 76; 77; 78]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multirow{2}{*}{**TRS (g/L)**} & \multicolumn{2}{c}{**\% Yield of Sugars**} & \multicolumn{2}{c}{**\% Selectivity of**} & **Total Monomeric** \\  & & **(TRS)** & **Sugars (TRS)** & **Sugars (g/L)** \\ \hline Cellulose & 1.7 & 15 & 60 & 1.5 \\ Barley Straw & 2.9 & 45 & 54 & 1.8 \\ Solid I (WA 1:1) & 6.1 & 72 & 80 & 3.4 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Total reducing sugars (TRS) measurements obtained from the samples after the hydrolysis reaction. Figure 13: Yields of xylose (**A**) and furfural (**B**) of barley straw treated and not treated with [EMIMAcO]