基于金属有机骨架的高稳定性固体酸催化酯化反应的性能研究及动力学计算

Catalytic Performance Study and Kinetic Calculation of High Stability MOFs-Based Solid Acid for Esterification Reaction

以金属有机骨架UiO-66(Zr)和(NH_(4))_(2)SO_(4)为原料制备了高稳定性固体酸催化剂SUA500,将其用于催化油酸与甲醇的酯化反应生产生物柴油过程,以考察催化活性和稳定性。同时,借助XRD、FTIR、N_(2)吸附-脱附、Py-FTIR和XPS等表征手段分析催化剂理化特性与催化活性之间的内在联系。结果表明,当UiO-66(Zr)与(NH_(4))_(2)SO_(4)质量比为1∶1、活化温度为500℃、研磨时间为40 min和活化时间为4 h时,SUA500的酸量高达11.08 mmol/g,且具有良好的催化活性。具体表现为:在催化剂质量分数6%、甲醇与油酸摩尔比8、反应温度70℃、反应时间2 h时,酯化转化率达到93.62%,多次重复使用后催化活性未出现明显下降;并计算得到SUA500催化酯化反应的活化能为38.21 kJ/mol,指前因子为1144.76 min^(-1)。

A highly stable solid acid catalyst SUA500 is synthesized from MOF-based UiO-66(Zr)and(NH_(4)_(2)SO_(4),which is applied to catalyze the esterification reaction of oleic acid with methanol for biodiesel to investigate its catalytic activity and stability.In the meantime,the physical property and catalytic activity of the catalyst are analyzed by means of XRD,FTIR,N_(2)adsorption and desorption,XPS and Py-FTIR to reveal their inter-relationship.Results indicate that with the mass ratio of UiO-66(Zr)toNH_(4))_(2)SO_(4)of 1∶1 and the activation temperature of 500℃,the grinding time of 40 min and the activation time of 4 h,the acid amount of SUA500 is as high as 11.08 mmol/g,and it has excellent catalytic activity.For specific performance,the esterification conversion of 93.62%is achieved with the catalyst mass fraction of 6%and molar ratio of alcohol to oleic acid of 8 at 70℃for 2 h.No obvious catalytic activity loss is detected during repeated use.The activation energy and pre-exponential factor of catalyzed esterification reaction by SUA500 is 38.21 kJ/mol and 1144.76 min^(-1),respectively.