## 3 Results and Discussions
### Furfural Production from Acidified RH Hydrolysate  
Furfural is a major derivative of xylose that can be used in a wide range of industrial applications as a platform chemical or as a raw material in plastics, pharmaceuticals, etc. The pentose polymer (mainly xylan) extracted from hemicellulose is acid-hydrolyzed to xylose, which is then converted to furfural by dehydration [21]. In this study, the Fr. hydrolysate obtained from the alkaline fractionation at optimized conditions (maximizing xylose concentration and recovery) was also subjected to acidification with sulfuric acid adjusted to an acid concentration of 4%, and heat treatments were performed for furfural production. The variations in xmg production, its consumption, and furfural production at different temperatures as a function of reaction time are presented in Figure 4. At a reaction temperature of 150 \({}^{\circ}\)C, prior to reaching the reaction time of 60 min, xmg accumulated up to 1.28 g/L due to the hydrolysis of XMG in the Fr. hydrolysate and showed a tendency toward gradual consumption. However, furfural started to accumulate at the beginning of the reaction and increased to 2.05 g/L until about 120 min, but it decreased slightly to 1.89 g/L at 180 min. At this time, considering that the furfural stoichiometric coefficient is 0.64, it can be deduced that more than 3.20 g/L xmg was produced and consumed (Figure 4a).  
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Components**} & \multirow{2}{*}{
\begin{tabular}{c} **Solid** \\ **Remaining** \\ **(\%)** \\ \end{tabular} } & \multicolumn{4}{c}{**Fractionated Solid (\%)**} & \multicolumn{4}{c}{**Fractionated Liquid (\%)**} & \multicolumn{4}{c}{**EMB (\({}^{\text{a}}\))**} \\ \cline{3-10}  & & **Glucan** & **XMG (\({}^{\text{b}}\))** & **L Lignin** & **Ash** & **Glucan** & **XMG** & **Ash** & **Glucan** & **XMG** & **Ash** \\ \hline Raw RH & 100 & 35.6 & 13.6 & 22.7 & 15.7 & & & & & & \\ \hline Fractionated RH & 34.1 & 80.1 & 12.3 & 12.0 & - & 0.5 & 1.1 & 14.4 & 78.1 & 38.9 & 91.7 \\ Fractionated RH (\({}^{\text{c}}\)) & 27.3 & 4.2 & 4.1 & - & & & & & & \\ \hline Component retention & 76.7 & 30.9 & 18.1 & - & & & & & & \\ \hline NaOH fractionated at optimized reaction conditions; reaction temperature of 150 \({}^{\circ}\)C, reaction time of 45 min, and NaOH concentration of 6 wt.%. \({}^{\text{a}}\) Extraction mass balance: \(\frac{\Sigma C\text{i}+\text{i}\text{-}\text{-}\text{-}\text{-}\text{-}\text{-} \text{-}\text{-}\text{-}\text{-}\text{-}\text{-}\text{-}\text{-}\text{-} \text{-}\text{-}\text{-At higher reaction temperatures (180 and 210 \({}^{\circ}\)C), these trends of xmg and furfural production and consumption proceeded more rapidly. In the heat treatment at 180 \({}^{\circ}\)C (Figure 4b), the highest concentration of xmg was 0.88 g/L at 10 min, and it decreased sharply and remained at a very low concentration after reaching 60 min. Correspondingly, furfural also peaked at 1.86 g/L at 30 min and gradually decreased until the end of the reaction, with a final concentration of 0.89 g/L.  
Under harsher reaction conditions (210 \({}^{\circ}\)C), little xmg was generated throughout the heat treatment. The furfural concentration was 1.46 g/L at 10 min and then decreased dramatically to a low concentration (Figure 4c). The results above confirm that the conversion rate to furfural was much faster than that of xylose in the high-temperature heat treatment. In addition, the rapid decrease in the furfural concentration after the peak indicates that more furfural is consumed as the reaction intensity increases, which has been shown to be due to side reactions such as condensation, cleavage, isomerization, and resinization [39].