α蒎烯生物环氧化反应影响因素探讨.pdf

、可作为高级香料,也是一种重要精细化工中间体,可进一步合成多种高附加值、具有生理活性的化学品。化学法实现环氧化虽反应迅速,但副反应多,设备腐蚀大,环境污染严重; 而以酶为催化剂的生物法环氧化具有反应温和、收率高、绿色工艺等优势。,确定选择以酯为溶剂及过水解底物、过氧化脲(唧)为氧源的有机溶剂体系为最优选择,反应过程中均可保持95%以上的反应选择性。考察酯的种类、温度、酶量等因素对反应的影响,从反应速率和酶批次稳定性综合考虑, 以丙酸乙酯为最佳溶剂、30。%左右,%。探讨了丙酸乙酯为唯一酰基供体时的反应机制,无外加水时, mmol/L; 认为酶利用丙酸产过酸的反应速率和过酸平衡浓度远远低于酯,平衡浓度仅为7mmol/L;丙酸乙酯的水解和过水解反应为一对竞争性反应,因此有机体系中更有利于环氧化反应。在丙酸乙酯体系中考察各个因素对酶活的影响,发现脲素、溶剂等因素对酶毒害作用不大;对H202与过酸单因素对酶活影响结果如下:H202浓度在220~525mmol/L,剩余酶活900min内均为92%左右;过酸浓度为60 mmol/L时,900min后剩余酶活为93%。过酸与H202协同毒害作用更为明显: 保持过氧乙酸浓度为60 mmol/L,当H202浓度为分别为220、320、525 mmol/L 时,900min后剩余90%、70%、1 1%酶活。酶催化乙酸乙酯、丙酸乙酯、乙酸戊酯、己酸乙酯过水解,反应几乎万方数据均在60min后达到平衡,其过酸平衡浓度依次递减,分别为434mmol/L、 234mmol/L、l Olmmol/L和82mmol/L。而对于0【.蒎烯Chemical epoxidation 反应,测定丙酸乙酯、乙酸乙酯、乙酸丁酯体系反应速率常数,三种体系中速率常数都随温度升高而变大,如丙酸乙酯体系中当温度从30℃升至 60℃时,。同一温度下(例如50℃)丙酸乙酯反应速率常数最大(),乙酸乙酯次之();。关键词:丙酸乙酯叶蒎烯环氧化反应脂肪酶过水解万方数据 Influencing factors ofchemo-·enzymatic epoxidation ofa--pinene ABSTRACT O【-pineneepoxide iscool and refreshing as aseniorspices,and itis ahigh value—added,physiologically active intermediate forfinechemical synthesis. Although the reaction rateofchemical epoxidation isfast,itsdisadvantages such as low yield,equipment corrosion and environmental pollution should not be thiscase,chemo-enzymatic epoxidation has show grester superiority:a mild reactionandhigh yield. Based on parison among the immobilized lipase-mediated epoxidation processes of a-pinene indifferentsystems,anic solvent system isdetermined,which employs esters as solvent andperhydrolysis substrate,and urea-hydrogen peroxide(L刀皿)as an oxygen source,wherein a reaction selectivity of over 95%can bemaintained during Was studied here theeffect ofvarious kinds ofester,theamount oflipaseand the temperature on thereaction,the optimal reaction condition was 30℃for the te