杂多酸催化微晶纤维素水解制备葡萄糖

Hydrolysis of Microcrystalline Cellulose into Glucose over Heteropolyacid Catalysts

以磷钨酸、磷钼酸和硅钨酸3种典型Keggin型杂多酸为催化剂,考察其对微晶纤维素在水热条件下水解制备葡萄糖反应的催化性能。杂多酸催化作用下,微晶纤维素水解主要生成葡萄糖、果糖、5-羟甲基糠醛、乙酰丙酸和甲酸等产物。以葡萄糖收率和选择性为评价标准,杂多酸催化性能从大到小为磷钨酸,硅钨酸,磷钼酸,与其酸强度顺序一致。磷钨酸催化体系中,适中的反应温度、较短的反应时间及较多的催化剂用量有利于葡萄糖的生成。磷钨酸催化纤维素水解的最佳反应条件为:磷钨酸用量0.7 mmol,反应温度170℃,反应时间4 h。葡萄糖收率最大为34.7%,选择性为57.5%。采用乙醚萃取法从液相产物中回收磷钨酸循环使用,其催化性能基本保持稳定。

The hydrolysis of cellulose into glucose over heteropolyacid catalysts with Keggin structure including H_(3)PW_(12)O_(40),H_(3)PMo_(12)O_(40) and H_(4)SiW_(12)O_(40) were investigated under hydrothermal conditions.Microcrystalline cellulose was mainly converted into glucose,fructose,5-hydroxymethylfurfural,levulinic acid and formic acid.The catalytic performance of three heteropolyacid catalysts in terms of glucose yield and selectivity were in order of H_(3)PW_(12)O_(40),H_(4)SiW_(12)O_(40),H_(3)PMo_(12)O_(40),which was consistent with the order of acid strength in three heteropolyacid catalysts.Stronger acidity,moderate reaction temperature and shorter reaction time are favorable for the hydrolysis of cellulose into glucose.The optimal reaction conditions over H_(3)PW_(12)O_(40) should be H_(3)PW_(12)O_(40) dosage of 0.7 mmol at 170℃ for 4 h.The maximum glucose yield reached 34.7%with selectivity of 57.5%.The H_(3)PW_(12)O_(40) catalyst could be readily separated from the hydrolysate by extraction with diethyl ether for reuse and remained good catalytic activity during recycle tests.