## 3 Results and Discussion  
### Determination of Optimum Conditions for Glucose Conversion  
Glucose conversion was conducted in [DBDIm]I-based IL, which has high hydrophobic properties due to its three butyl chains and three aromatic rings in its structure, as shown in Figure 1. The effects of [DBDIm]I as a solvent (also as a Lewis acid) and H\({}_{2}\)SO\({}_{4}\) (Brensted acid) in glucose conversion were observed at a temperature of 80 \({}^{\circ}\)C, with a reaction time ranging from 20 to 120 min. The results showed that a longer reaction time is essential for a better glucose conversion in [DBDIm]I (Figure 2a). The optimum reaction time of glucose conversion in [DBDIm]I supported by 1M H\({}_{2}\)SO\({}_{4}\) was 120 min, which showed a yield of 76.3% HMF. The results also indicated that the glucose conversion in only water as a solvent without an acid catalyst at the same reaction conditions did not produce HMF. It is hard to dehydrate glucose in the presence of water; thus, it is also not feasible to form HMF in the absence of a dehydrating agent, such as Lewis acid or Brensted acid catalysts. Nevertheless, the increase in temperature affected the HMF production, even in the system containing only glucose and water (Figure 2b). It was apparent that the higher temperature would promote the dehydration of glucose due to the vaporization of water. The combination of a Lewis acid of [DBDIm]II and Brensted acid of H\({}_{2}\)SO\({}_{4}\) showed better glucose conversion than the Lewis acid or Brensted acid alone. This study developed a strategy for integrating the sequential catalytic process for biomass transformation in a single-step reaction. The effect of temperature on glucose conversion was studied. The temperatures studied were with 5 \({}^{\circ}\)C increments from 80 to 105 \({}^{\circ}\)C, and the results are shown in Figure 2b. The % yield of HMF increased with increasing temperature. A high temperature was usually needed to promote the dehydration reaction of glucose; however, at the highest temperature tested, the HMF yield slightly decreased due to HMF transformation into LA and FA, as reported by others [8; 34; 41; 45; 46]. We conclude from this study that the optimum temperature for glucose conversion to HMF in [DBDIm]I with or without H\({}_{2}\)SO\({}_{4}\) was 100 \({}^{\circ}\)C. The best glucose conversion conditions were the operating temperature of 100 \({}^{\circ}\)C and the reaction time of 120 min in [DBDIm]I as both the solvent and Lewis acid, and H\({}_{2}\)SO\({}_{4}\) as a Brensted acid catalyst. These conditions produced 82.2% HMF. [PERSON] et al. [46] reported that the optimum temperature to convert lignocellulosicoses to HMFwas 160\({}^{\circ}\). [PERSON] et al. [41] reported the optimum temperature to convert lignocellulosicoses into HMF was 100 \({}^{\circ}\)C. This study showed notable improvement in the HMF yield compared to previously reported studies. There were few reports available on the sugar conversion to HMF. Fructose conversion to HMF supported by metal halides as a Lewis acid within 3 h gave a 70.0% HMF yield [16]. HMF from cellulose conversion reported by [PERSON] et al. [24] produced a yield of 54.9% within 9 h at 150 \({}^{\circ}\)C in [BMIm]Cl-based IL. Cellulose conversion in [BMIm]Cl supported by \(\mathrm{TiOSO_{4}}\) catalyst at 100 \({}^{\circ}\)C for 3 h produced 38.0% HMF [44; 28; 45; 46]. [PERSON] et al. [46] reported a yield of 43.7% HMF from cellulose in the presence of tetrabutylammoniumchloride (TBAC) and chromium(III) trichloride (CrCl\({}_{3}\cdot\)6H\({}_{2}\)O) catalyst at a 140 \({}^{\circ}\)C and 90 min reaction time. These reports showed lower HMF yields with relatively longer reaction times at higher temperatures compared to our study. The other glucose conversion products in [DBDIm]I or water at 80 \({}^{\circ}\)C with and without the addition of H\({}_{2}\)SO\({}_{4}\) were LA and FA, as presented in Figure 3. The highest %mole yield of LA and FA were 13.8% and 2.7%, respectively.