二氧化硅负载磷钨酸催化罗汉柏木烯的异构反应

Silica-supported phosphotungstic acids catalyze isomerization reaction of thujopsene

甲基柏木酮为柏木系最重要的香料之一,具有珍贵的木香-麝香-龙涎香气息,其中Isomer G成分的香气最为出色,它是由罗汉柏烯先异构为Olefin B,再乙酰化得到。采用溶胶-凝胶法制备二氧化硅负载磷钨酸固体催化剂制备Olefin B,研究磷钨酸负载量、焙烧温度和焙烧时间对催化剂活性的影响,用比表面积及孔径分析(BET)、X-射线多晶衍射(XRD)进行表征;通过单因素及正交试验优化罗汉柏木烯异构反应工艺,并用气相色谱-质谱(GC-MS)联用仪对产物进行表征。研究表明:催化剂制备最佳工艺条件为磷钨酸负载量40%、焙烧温度200℃和焙烧时间3 h时,催化活性最强;异构化单因素最佳条件为反应温度70℃、反应时间7 h、溶剂质量分数50%和催化剂质量分数10%;正交试验最佳工艺条件为反应温度80℃、反应时间7 h、乙酸质量分数50%和催化剂质量分数10%,平均得率58.1%,产物Olefin B(7,10-桥亚乙基-4,4,7-三甲基-1,9-八氢化萘)的选择性为97.7%,催化剂可循环使用3次。

Methyl cedryl ketone（ MCK） is one of the most important cedar spice,which has woody-musk-ambergris aromas. Isomer G,the most excellent aroma component of the MCK,was the product of acetylation of Olefin B isomerized by thujopsene. Previous studies on thujopsene isomerization have many problems,such as complex intermediates,lowselectivity. In this study,we used sol-gel method to prepare silica-supported phosphotungstic acid catalyst to make Olefin B,and the effects of phosphotungstic acid loading amount,calcination temperature and calcination time on catalyst activity were investigated,in addition,the catalyst was characterized by the specific surface area and pore size analyzer（ BET） and X-ray diffraction（ XRD）. The isomerization reaction process was optimized through the orthogonal test and single factor study to improve the yield and selectivity of Olefin B. The isomerization product was characterized by gas chromatography-mass spectrometer（ GC-MS）. The results of this study showed that the optimum conditions of preparation of catalyst are as follows： phosphotungstic acid loading is 40%,calcination temperature is200℃ and calcination time is 3 h,and the catalyst illuminates the strongest isomerization activity. The single factor optimum isomerism conditions are： reaction temperature of 70℃,reaction time of 7 h,the mass fraction of solvent of50%,the mass fraction of catalyst of 10%. The optimum orthogonal test conditions are： reaction temperature of 80℃,reaction time of 7 h,the mass amount of solvent of 50%,the mass amount of catalyst of 10%,and average yield up to 58.1%. The selectivity of main product Olefin B is 97.7%,and catalyst can be recycled for three times. The results indicate that the sol-gel H3 PW12 O40/Si O2 has good catalytic activity on isomerization,and would be useful for synthesis of Isomer G if Olefin B is further purified.