Development of cellulose-derived HMF production catalyzed by ion exchange resin in ionic liquid

采用离子交换树脂和离子液体等多相催化剂作为催化剂和溶剂，开发了包括纤维素水解、葡萄糖异构化和果糖脱水等多步骤反应的纤维素基HMF生产工艺。研究发现，连续加水对纤维素水解法选择性生产葡萄糖是有效的。结果表明，通常对水溶液中葡萄糖异构化反应有效的碱性催化剂在离子液体中失活。这可能是由于非均相催化剂中的碱(或碱土)金属离子与离子液体(如[Bmim][Cl])中的Cl-发生强烈的相互作用而使材料上的活性中心中毒所致。此外，葡萄糖异构化为果糖的反应是平衡反应，在较低的温度下，由于平衡约束，果糖的产量受到限制。为了克服这些问题，从葡萄糖直接生产HMF是有效的，必须尝试使用Lewis酸催化剂。采用液-液萃取与精馏相结合的方法，可以实现能量利好的产物分离和溶剂循环利用。

To develop cellulose-derived HMF production process, which includes multi-step reaction (cellulose hydrolysis, glucose isomerization and fructose dehydration), heterogeneous catalysts such as ion exchange resin and ionic liquid were employed as catalysts and solvent, respectively. It was found that sequential water addition was effective for selective glucose production via cellulose hydrolysis. It was revealed that alkali catalyst, which is normally effective for glucose isomerization in aqueous solution, became inactive in ionic liquid. Probably, this can be explained by strong interactions between alkali (or alkaline-earth) metal ion in heterogeneous catalysts and Cl- in ionic liquid (such as [Bmim][Cl]) such that active sites on the materials are poisoned. In addition, glucose isomerization into fructose is equilibrium reaction and fructose yield is limited at lower temperature because of the equilibrium constraint. To overcome these issues, direct production of HMF from glucose is effective and Lewis acid catalyst must be attempted. To accomplish energetically-favorable products separation and recycle of solvent, combination of liquid-liquid extraction with distillation would be appropriate and effective.