The Catalytic Formation of 5-Hydroxymethyl Furfuraldehyde from Glucose with Nano-TiO₂ Gel

Nano TiO₂ gel and PEG-TiO₂ gel were synthesized with the sol-gel method and were used as catalysts for glucose conversion into 5-hydroxymethyl furfuraldehyde (HMF). The catalytic properties of nano TiO₂ gel and TiO₂ powder were compared. The results show that with nano TiO₂ gel as catalyst, the conversion rate of glucose into HMF was 93.7%, and the yield of HMF was 21.7% and with nano TiO₂ as catalyst, the glucose conversion rate was close to 100%, while the yield of HMF was only 1.4%. PEG-TiO₂ with higher gelid content of TiO₂ was prepared using polyethylene glycol (PEG 200) and ethyl titanate as raw materials, which was convenient for transportation, storage and use. Under the optimal conditions, with PEG-TiO₂ gel and formic acid as catalyst and water as reaction liquid, the glucose conversion rate reached 92.0%, the yield of HMF reached 56.2%, the reaction temperature was 100 ℃, and the reaction time was 12 h. The results provide a new method for large-scale green and efficient catalytic conversion of glucose into HMF in industry.