碱性离子液体协同配合剂催化葡萄糖异构化制备果糖

Efficient isomerization of glucose to fructose co-catalyzed with basic ionic liquid and sodium borate

糖类是生物质的重要组成部分,可经催化转化制得一系列高附加值化学品,具有经济价值高、对环境友好和可持续性强等优点。葡萄糖异构为果糖是该过程的关键步骤。本文合成了四种碱功能性离子液体,用红外光谱、核磁共振谱仪和热重分析进行了表征,并用于催化葡萄糖异构化制备果糖,结果表明碱性离子液体具有较好的催化活性,但易使果糖进一步催化降解,同时加入硼酸钠可提高葡萄糖的转化率和果糖的产率,说明硼酸钠既起配合保护剂的作用,也有一定的协同催化作用。考察了离子液体用量、硼酸钠用量、时间、温度等因素对果糖选择性和产率的影响,结果表明,在离子液体和硼酸钠与葡萄糖的摩尔比分别为3∶1和0.08∶1、反应温度为70℃、反应时间为7 min的最佳反应条件下果糖的产率可高达64.7%,选择性为73.1%。

Carbohydrates are an important part of biomass and can be converted into a series of high value-added chemicals through catalytic conversion,which has the advantages of high economic value,environmental friendliness and sustainability.Isomerization of glucose into fructose is a key step in the process.Herein,four basic functional ionic liquids:[HOEtMim]Phen,[EMim]Phen,[HOEtMim]Im,[Ch]Phen were synthesized and their catalytic performances on glucose isomerization were investigated.A comparison of direct transformation and catalysts combined with sodium borate complex was discussed.It showed that four basic ionic liquids exhibit good catalytic activities,but fructose is easily to be further degraded.While ionic liquids added with sodium borate obtain much higher fructose yields.It indicates that sodium borate plays an important role in both protective agent and synergistic catalysis.[Ch]Phen added with sodium borate is the most efficient.The basic structure parameters of[Ch]Phen were further characterized by 1H NMR,FT-IR and TG-DTG techniques.The effects of reaction temperature,reaction time,the dosage of catalyst and sodium borate on the isomerization and the optimal reaction conditions were investigated by single factor method.The yield of fructose is up to 64.7%with a high selectivity of 73.1%under the optimum condition at 70℃within 7 min.