极性非质子溶剂中酸强度对纤维素降解制备脱水糖的影响

Effect of acidity on anhydrosugars preparation from cellulose in polar aprotic solvent

在极性非质子溶剂中,酸催化剂对于纤维素降解制备脱水糖的反应起到重要作用。本文考察不同强度酸催化剂在极性非质子溶剂1,4-二氧六环中对纤维二糖、纤维素降解制备左旋葡聚糖(levoglucosan, LGA)以及LGA脱水制备左旋葡萄糖酮(levoglucosenone, LGO)的影响。结果表明:酸性过强(pK_(a)<-3)或酸性过弱(pK_(a)>-2)的催化剂对脱水糖制备催化性能较差,而pK_(a)为-3~-2的酸催化剂,如,对甲苯磺酸、甲磺酸、浓硫酸等对纤维素、纤维二糖制备LGA以及LGA脱水制备LGO的反应催化效果较好。以纤维二糖为反应物,甲磺酸为催化剂时,可得到最高的LGA碳收率为45.87%。

Acidic catalyst plays an important role in cellulose degradation in polar aprotic solvents to produce anhydrosugars.Here,the degradation of cellobiose and cellulose to levoglucosan(LGA)and the dehydration of LGA to levoglucosenone(LGO)in 1,4-dioxane with different acid catalysts were investigated.The results show that all acidic catalysts with pK_(a)<-3 or pK_(a)>-2 have poor catalytic performance for anhydro-sugars preparation,whereas acids with pK_(a) value between-3 and-2,such as p-toluenesulfonic acid,methanesulfonic acid and sulfuric acid,have better catalytic efficiency to cellulose degradation and LGA dehydration.The highest carbon yield of LGA was 45.87%when cellobiose was the reactant and methane sulfonic acid was the catalyst.