# Fractionation of Lignocellulosic Biomass by Selective Precipitation from Ionic Liquid Dissolution
## 3 Results and Discussion
### Catalytic Activity  
Original barley straw, cellulose and Solid I were subjected to hydrolysis in water media at 140 \({}^{\circ}\)C with 0.2 mol/L H\({}_{2}\)SO\({}_{4}\). In Table 3, a comparison of the conversion values obtained with Solid I, the original barley straw and Avicel cellulose without treatment are shown. The conversion values were calculated by the weight difference between the sample initially added to the reaction and the sample obtained after reaction. The conversion values were different among the three samples studied; the lowest value was obtained for the cellulose sample, while the conversion values were higher for the other two samples. This trend is expected because the most complicated material to hydrolyze is cellulose, and samples of untreated barley straw only contain approximately 31% cellulose (Table 3). In Solid I, impurities of lignin in the sample were not taken into account to avoid complicating the calculations and reduce error since the amount of lignin in the sample was very small. The conversion of 90% in Solid I appears to be slightly high. However, the conversion data are not conclusive because the hydrolysis schemes of cellulose and hemicellulose are complicated by consecutive reactions and can lead to the formation of humics and other products. For this reason, it is interesting to analyze the yields of the main products derived from  
Figure 11: Scanning electron microscopy (SEM) images of raw barley straw (**left**) and barley straw treated with [EMIMAcO] (Solid I, WA 1:1) (**right**). \begin{table}
\begin{tabular}{c c} \hline \hline
**Sample** & **\% Conversion** \\ \hline Cellulose & 25 \\ Barley Straw & 83 \\ Solid I & 93 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Results of conversion obtained after hydrolysis of untreated cellulose, untreated barley straw and barley straw treated (Solid I) with [EMIMAcO]. Reaction conditions: H\({}_{2}\)SO\({}_{4}\) (0.2 mol/L), 140 \({}^{\circ}\)C and 5 h.  
gluucas, glucose and levulinic acid, and the main products of xylans, xylose and furfural. It should be noted that under these reaction conditions and in aqueous media in the presence of an acid, the concentration of 5-hydroxymethylfurfural is very small because it easily transforms into levulinic acid. In Figure 12A, the yield of glucose decreases in the following order: Solid I \(>\) original barley straw \(>\) cellulose. Cellulose gave a very low yield of glucose (11%) after 5 h of reaction. The barley straw sample gave a higher yield of approximately 30%. However, with the Solid I sample, a yield of 65% was reached, which substantially affects acid hydrolysis to sugars. These glucose yield values follow an order inverse to that of sample crystallinity, as shown in Figure 10. This is because greater crystallinity (order) hinders the breakdown of the 8(1\(\rightarrow\)4)-b-glucoside bonds of cellulose because they are less accessible. However, treatment that reduces the crystallinity and increases the accessibility of said bonds favors hydrolysis, giving rise to higher yields of glucose [33; 34; 46; 71]. The yield of levulinic acid follows a profile very similar to that of glucose (Figure 12B) because levulinic acid is a byproduct of glucose; therefore, at higher glucose concentrations, more levulinic acid can be formed, but in all cases, the yield of levulinic acid is low with respect to that of glucose. We compared the raw barley straw sample without treatment and Solid I in acid hydrolysis to obtain the concentration curves of the compounds xylose and furfural (Figure 13A,B) in both cases. The yield of xylose increased quickly with reaction time, reaching a maximum in both cases (Figure 13A). At 2 h, the barley straw obtained a yield of 45%, and Solid I achieved a yield of 58%, but the yield of Solid I reached a maximum of 60% at 3 h and then decreased until the end of the reaction, at which point the yield of xylose was 25% in barley straw and 35% in Solid I.