磁性固体碱K_(2)O/LDO-γ-Fe_(2)O_(3)催化甘油合成碳酸甘油酯

Synthesis of glycerol carbonate by transesterification of glycerol catalyzed with magnetic solid base K_(2)O/LDO-γ-Fe_(2)O_(3)

为了解决甘油合成碳酸甘油酯产率较低及反应完成后催化剂的回收问题,制备磁性水滑石LDH-Fe3O4,以KNO3为活性组分前驱体对其改性制备磁性固体碱催化剂K_(2)O/LDO-γ-Fe_(2)O_(3),对KNO3的负载量进行考察,对K_(2)O/LDO-γ-Fe_(2)O_(3)进行X射线衍射、扫描电子显微镜、 CO_(2)程序升温脱附、BET及磁化强度表征,采用单因素试验对K_(2)O/LDO-γ-Fe_(2)O_(3)催化甘油酯交换合成碳酸甘油酯的工艺条件进行了优化,并对K_(2)O/LDO-γ-Fe_(2)O_(3)的重复使用性能进行了考察。结果表明:KNO3负载提供了大量的碱性位点,有利于催化剂催化活性的提高,KNO3的最佳负载量为10%(以LDH-Fe3O4质量计),K_(2)O/LDO-γ-Fe_(2)O_(3)的饱和磁化强度为10.47 emu/g;K_(2)O/LDO-γ-Fe_(2)O_(3)催化酯交换最佳反应条件为反应温度100℃、反应时间2 h、催化剂用量3%(以甘油质量计)、甘油与碳酸二甲酯物质的量比1∶2,在此条件下碳酸甘油酯产率为92.12%;催化剂重复使用5次后碳酸甘油酯产率高达89.35%,相比镁铝水滑石,K_(2)O/LDO-γ-Fe_(2)O_(3)催化反应时间短,反应试剂用量少。K_(2)O/LDO-γ-Fe_(2)O_(3)催化剂具有磁性,可在外加磁场作用下与反应体系分离,并且在数次循环使用中保持较高的活性,经济成本降低,在工业生产碳酸甘油酯中有很好的应用前景。

In order to solve the problems of the low yield of glycerol carbonate synthesized with glycerol and the recovery of the catalyst after the reaction,the magnetic hydrotalcite LDH-Fe3O4 was prepared and modified by KNO3 as the active component precursor to prepare magnetic solid base catalyst K_(2)O/LDO-γ-Fe_(2)O_(3).The KNO3 loading amount of the catalyst was studied.The K_(2)O/LDO-γ-Fe_(2)O_(3) was characterized by X-ray diffraction,scanning electron microscopy,CO_(2)-TPD,BET and magnetization intensity.The process conditions of the K_(2)O/LDO-γ-Fe_(2)O_(3)-catalyzed transesterification of glycerol for the synthesis of glycerol carbonate were optimized using single factor experiment.The reusability of K_(2)O/LDO-γ-Fe_(2)O_(3) was investigated.The results showed that KNO3 provided a large number of alkaline sites,which facilitated the catalytic activity of the catalyst,and the optimal loading amount was 10%(based on the mass of LDH-Fe3O4).The saturation magnetization intensity of K_(2)O/LDO-γ-Fe_(2)O_(3) was 10.47 emu/g.The optimal transesterification conditions were as follows:reaction temperature 100℃,reaction time 2 h,catalyst dosage 3%(based on the mass of glycerol),and molar ratio of glycerol to dimethyl carbonate 1∶2.Under the optimal conditions,the glycerol carbonate yield was 92.12%.The yield of glycerol carbonate reached 89.35%after five repetitions of the catalyst.The K_(2)O/LDO-γ-Fe_(2)O_(3) catalytic reaction time was shorter and the amount of reaction reagent was less than that of Mg-Al hydrotalcite.In conclusion,the magnetic catalyst prepared is magnetic and can be separated from the reaction system under the action of an applied magnetic field,and can maintain high activity in several cycles with reduced economic costs,and has a good application prospect in industrial production of glycerol carbonate.