百里香酚合成薄荷醇副反应研究

Study on side reactions of thymol hydrogenation

l-薄荷醇是世界上销量最大的香料之一,其生产方法主要以百里香酚为原料,先加氢生成薄荷醇8种异构体,再拆分得到l-薄荷醇.现有文献未对百里香酚催化加氢副反应进行深入研究.为加深对百里香酚加氢反应脉络的理解,本实验以雷尼镍为催化剂,观察其在高压反应釜中进行百里香酚合成薄荷醇的副反应,以气质联用方法 (GC-MS)鉴定了副产物结构.并采用量子化学方法研究了副反应机理,对不同副产物生成的可能性大小进行比较.结果表明,在200℃,3MPa时主要副反应为薄荷醇脱水,薄荷醇和百里香酚的连续脱甲基反应.反应机理为催化剂镍原子活化了异丙基上的碳碳键和连接环的碳氧键.主要副产物有烷基环己醇类、烷基苯酚类及烷基环己烷类,生成副产物可能性大小的顺序为烷基苯酚类>烷基环己醇类>烷基环己烷类.

Menthol is one of the most popular perfumes in the world, applied on various areas of the fine chemical in- dustry, such as pharmaceutical, additives and perfumes. One of the industrial synthetic menthol process starts with thymol hydrogenation, followed by distillation of menthol mixture and crystallization of d,l-menthol. To analyze the whole reaction network of thymol hydrogenation, the side reactions of thymol hydrogenation were studied under Raney Ni catalyst in autoclave, and all by products were analyzed by GC-MS. The quantum chemistry method was used to study the mechanism o{ side reactions and predict the possibility of side products. Results showed that the side reactions consist of menthol dehydration and the demethylation of menthol and thymol under 200℃, 3 MPa, due to activated C C bonds and C--O bonds by Ni catalyst. The main byproducts are alkylated phenol, alkylated cyclohexanol and alkylated cyclohexane, and the possibility order of these side products is as follows： alkylated phenol 〉alkylated cyclohexanol〉alkylated cyclohexane.