羟基羧酸催化蒎烯水合/乙酯化反应机理研究

Terpineol is one of the three largest turpentine deep processing products.The existing synthetic methods have the problems of low product yield and pollution. Some substituted carboxylic acid , such as halogenated acids and amino acids ,can catalyze the pinene prepared terpineol or terpinyl acetate. The compound catalyst of hydroxyl substituted carboxylic acid and boron compound, which was created by the project group, has good catalytic performance. It is necessary to further study the reaction mechanism of this catalyst. In this project, the influence of the molecular structure, composition, reaction medium and external field will be systematically studied. The aggregation behavior and stability of the catalyst in the reaction medium need to be revealed. Furthermore,the catalyst will be immobilized on the porous carbon based material,and the effect of load conditions on the structure and properties of the catalyst will be investigated. The activated carbon will be expanded and oxidized by Hummers method, to increase acid groups such as carboxyl, hydroxyl, and epoxy group on its surface. At the same time, the hydroxyl carboxylic acid will be loaded in the pore of this activated carbon, and the surface modification will be made to synthesize the high efficiency solid catalyst. We will study the mesoscale behavior and regulation mechanism of solid-liquid and liquid-liquid in the reaction system. Also,we will explore the effects of homogeneous and heterogeneous media on proton transfer and chemical structure formation. The crystallization of terpene and acetic acid mixtures at low temperature will be revealed, and the green recovery of acetic acid and the high efficiency separation of the products may be realized. The research results of this project, will provide theoretical support for the one-step synthesis of terpineol or terpineyl acetate.

松油醇为松节油三大深加工产品之一，现有合成方法存在产品收率不高和污染问题。某些取代基羧酸，如卤代酸和氨基酸，能催化蒎烯进行水合、乙酯化反应。申请者创制了羟基羧酸和硼化合物复合催化剂，能较好的催化蒎烯一步合成松油醇和乙酸松油酯，但机理尚需进一步揭示。本项目研究取代基羧酸分子结构、配合物、反应介质和外场等对催化性能的影响，揭示催化剂在反应介质中的聚集行为和稳定性规律。研究将取代基羧酸固载在多孔碳基材料上，考察负载条件对催化剂结构和性能的影响。采用Hummers法对活性炭进行扩孔和氧化，增加表面羧基、羟基等酸性基团，并进行修饰、改性来制备高效固体羧酸催化剂。探明反应体系中固液、液液的介尺度行为和调控机制。探索均匀、非均匀介质对质子传递过程及产物结构的影响。并揭示萜类、乙酸混合体系低温结晶规律，实现乙酸的绿色回收和产物的高效分离。本研究将为一步法绿色合成松油醇、乙酸松油酯的产业化应用提供理论支撑。

蒎烯、莰烯等萜烯通过水合反应和酯化反应，可以得到松油醇、龙脑、异龙脑、乙酸松油酯、乙酸龙脑酯和乙酸异龙脑酯等林化产品。催化此类反应的传统的催化剂包括硫酸、阳离子交换树脂、离子液体、分子筛等。针对此类反应设计的催化剂，主要集中在强酸和超强酸，而酸性较弱且无毒的α-羟基酸（HCA）很少被涉及。.本项目以α-羟基羧酸母体，通过分别与磷酸为代表的质子酸和以硼酸为代表的路易斯酸结合，考察它们的协同催化能力，筛选出催化活性高的组合体。研究发现HCA-硼酸复合催化剂具有较高的催化活性。通过分析测量硼酸对HCA水溶液的pH和旋光度的影响，考察了硼酸与HCA形成的配合物结构和分布状况，为催化剂的优化设计提供了参考。通过将复合催化剂应用于蒎烯、莰烯的水合和酯化反应，考察和验证了HCA-硼酸复合体系的协同催化作用。作为复合催化剂的组分，以蒎烯转化率和松油醇的选择性来衡量，硼酸优于硫酸、磷酸等无机酸。.以HCA-硼酸作为催化剂，松油醇的选择性都超过了50%，最高的酒石酸-硼酸催化剂，蒎烯转化率为96.1%，松油醇的选择性为58.7%。扁桃酸-硼酸复合催化剂，能够在无溶剂条件下，直接催化蒎烯水合反应，蒎烯转化率可达96.1%,松油醇的选择性为55.5%。通过正交实验，发现影响蒎烯乙酯化反应产物收率的最重要因素为HCA用量。而利用B2O3替代硼酸，可以减少HCA的用量。当乳酸和B2O3的用量分别占蒎烯质量的10%和4%时，蒎烯的转化率可达93.2%，乙酸松油酯的选择性可达47.1%。水对HCA-硼酸复合催化剂是不利的，但适量的水有利于提高HCA-B2O3催化活性。当酒石酸-B2O3作催化剂，水的用量为蒎烯质量的1%时，蒎烯的转化率仍可达89.6%，乙酸松油酯的选择性可达47.5%。对于莰烯乙酯化反应，酒石酸-硼酸作催化剂，较优条件下莰烯的转化率、乙酸异龙脑酯的GC含量和选择性分别为92.9%、88.5%和95.3%。莰烯与含水乙酸反应时，可以得到含异龙脑的产物。它们的催化机理类似，即先通过形成羟基羧酸萜烯酯中间体，再与反应体系中水或乙酸反应得到目标产物，产物的旋光性与萜烯原料保持一致。