无溶剂体系中固定化脂肪酶催化合成香茅醇酯

在无溶剂体系中以大孔树脂NKA吸附固定的褶皱假丝酵母脂肪酶(Candida rugosalipase)为催化剂,以脂肪酸为酰基供体,酶法合成香茅醇脂肪酸酯。考察了褶皱假丝酵母脂肪酶对酰基供体的选择性,以及反应温度、摇床转速、酶用量、底物比例及微量水添加等对酯化反应的影响,建立了无溶剂中香茅醇酯的酶法合成工艺。研究表明,在酸醇物质的量比为1,摇床转速为200 r/min,固定化酶用量为1250 U/L,反应温度为50℃,微量水添加量为4μL的条件下,反应10h,月桂酸香茅酯及油酸香茅酯的转化率分别可达95.6%和87.6%,明显高于在有机溶剂体系中的酯化率。     

有机相中脂肪酶催化转酯化反应动力学拆分左旋帕罗醇

研究了在有机相中脂肪酶催化转酯化反应动力学拆分左旋帕罗醇,考察了酶种类、溶剂、酰基供体、温度、底物与酰基供体摩尔比等因素对反应的影响。结果表明:以Novozym 435为催化剂,在30℃下,以乙腈为反应溶剂,乙酸乙烯酯为酰基供体,底物浓度40mmol/L及其与酰基供体摩尔比为1:8时,反应8h后,底物转化率为48.1%,ee_s为53.3%,E值为6.20。     

在α-蒎烯生物环氧化反应过程中酯对反应的影响及机理探讨

在以过氧化脲(UHP)为氧源、Nov435为催化剂的体系中进行α-蒎烯生物环氧化反应的研究,重点考察不同酯作为酰基供体对反应的影响。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℃下α-蒎烯3h的环氧转化率可达到87%左右,经6批次反应后仍可达到47.6%,发现过酸和H₂O₂的协同作用对酶稳定性的影响要高于单一因素。酶催化乙酸乙酯、丙酸乙酯、乙酸戊酯、己酸乙酯等不同酰基供体过水解反应均可在60min达到平衡,但过酸平衡浓度和α-蒎烯化学环氧化反应速率受酯影响较大,进而对总反应化学-酶法联合催化环氧化产生影响。最后探讨了丙酸乙酯为唯一酰基供体时的反应机制,认为酶利用丙酸产过酸的反应速率和过酸平衡浓度远低于酯;丙酸乙酯的水解和过水解反应为一对竞争性反应,因此有机体系更有利于环氧化反应。     

叔丁醇体系中化学酶法催化α-蒎烯环氧化

采用叔丁醇作为α-蒎烯环氧化的反应溶剂,使过氧化氢水溶液和其他疏水性反应底物形成均相,构建单相体系以代替传统有机-水“双相”系统。首先在摇瓶中对单相体系进行优化,在α-蒎烯浓度为0.3mol/L时,乙酸乙酯的最适浓度为3.5mol/L,过氧化氢的最适浓度为0.5mol/L,束酸剂为柠檬酸三钠,在40℃下,反应90min,环氧化转化率为92%,收率为88%。此工艺条件下Novozym435重复使用6次后,仍保持64%的相对活力。然后以摇瓶实验为基础,构建了一种连续搅拌釜式反应器（CSTR）,探索反应器的最适运行条件,测试了其长期运行性能,结果表明：当Novozym435酶量为2.0g、过氧化氢浓度为0.5mol/L、停留时间为3h时,釜式反应器的运行效果最好,其转化率可达83%,收率可达79%,在此条件下反应器连续运行十天后依然可以保持70%以上的转化率和55%以上的收率。     

AOT逆胶束体系脂肪酶催化合成油酸乙酯

在二-(2-乙基己基)琥珀酸酯磺酸钠和异辛烷构建的逆胶束体系中,以Lipex脂肪酶为催化剂,合成了油酸乙酯,考察了各影响因素对其产率的影响,并进行了脂肪酶紫外荧光检测和体系粒度分析. 结果表明,Lipex脂肪酶具有良好的催化活性,反应条件优化选用异辛烷为溶剂,在反应温度25℃、缓冲液pH 6.5、水/表面活性剂(摩尔比)10、乙醇/油酸(摩尔比)20及Lipex脂肪酶浓度0.035 g/L、油酸浓度0.005 mol/L、摇床转速150 r/min、反应36 h的条件下,油酸乙酯产率达到71.25%. 逆胶束粒度和酶构象直接影响酶活性,最适逆胶束粒度约为80 nm.     

丙酮液相氨肟化连续流反应

在液相条件下,以丙酮、氨水和双氧水为原料,钛硅分子筛（TS-1）为催化剂,叔丁醇为溶剂,在具有特殊微结构的连续流微通道反应器中一步氧化合成丙酮肟。实验考察了双氧水浓度、氨水用量、双氧水用量、溶剂用量、助催化剂用量以及温度对氨肟化的影响,结果表明：AFR微通道反应器中,反应器出口压力5 bar,温度100 ℃,催化剂浓度8 g/mol（mol为丙酮的单位）,氨水/双氧水/叔丁醇/丙酮摩尔比=3:1.1:6:1,双氧水浓度70 wt.%,氨水浓度25 wt.%,助催化剂浓度3 mg/mol（mol为丙酮的单位）,停留时间72 s,获得丙酮转化率为80%,丙酮肟选择性为97%,丙酮肟的收率为77%。AFR微通道反应系统持液量小、停留时间短、强传质传热等特点,强化了反应物料和催化体系之间的协同效应,提高了氨肟化反应速率,解决了双氧水分解带来的氨肟化反应本质安全问题,实现了丙酮氨肟化的绿色安全高效合成。     

响应面法优化生物酶法制备环氧蓖麻油

以蓖麻油为研究对象,在甲苯溶剂体系中,以Novozyme435为催化剂制备环氧蓖麻油。探究了反应温度、反应时间、双氧水含量、蓖麻油酸含量、甲苯含量以及催化剂Novozyme435含量等因素对环氧蓖麻油环氧值的影响,并经响应面进一步优化得到合成环氧蓖麻油的最优条件。结果表明,最优条件为:反应温度42℃,反应时间18 h,过氧化氢与双键摩尔比2∶1,蓖麻油酸添加量8%,甲苯添加量43%以及催化剂Novozyme435添加量5%;在此条件下,环氧蓖麻油的环氧值可达5.20%,环氧转化率达97.93%。     

响应面法优化生物酶法制备环氧蓖麻油

以蓖麻油为研究对象,在甲苯溶剂体系中,以Novozyme435为催化剂制备环氧蓖麻油。探究了反应温度、反应时间、双氧水含量、蓖麻油酸含量、甲苯含量以及催化剂Novozyme435含量等因素对环氧蓖麻油环氧值的影响,并经响应面进一步优化得到合成环氧蓖麻油的最优条件。结果表明,最优条件为:反应温度42℃,反应时间18 h,过氧化氢与双键摩尔比2∶1,蓖麻油酸添加量8%,甲苯添加量43%以及催化剂Novozyme435添加量5%;在此条件下,环氧蓖麻油的环氧值可达5.20%,环氧转化率达97.93%。     

天然固定化木瓜脂肪酶催化芳香仲醇动力学拆分的研究

将木瓜来源的廉价天然固定化脂肪酶CPL用于手性拆分芳香仲醇,以4-苯基-2-丁醇作为模式底物,考察了反应温度、反应溶剂、酰基供体以及底物摩尔比对CPL拆分能力的影响,结果表明,适宜的反应温度30~45℃,酰基供体为活性乙烯酯,正己烷或环己烷作为反应溶剂,底物/酰基供体摩尔比1∶2,在该条件下底物的转化率接近50%,e.es大于99%,反应的对映体比值E大于200。CPL对其他结构类似的芳香仲醇也具有很好的拆分能力。该研究为手性芳香仲醇的酶催化制备提供了新的催化剂选择。     

固定化脂肪酶Candida sp99-125催化合成己酸乙酯

采用实验室自制的脂肪酶Candida sp 99-125在有机溶剂中催化合成乙酸乙酯,考察了有机溶剂种类、加酶量、酸醇物质的量之比、已酸浓度、反应时间和温度等对己酸转化率的影响.结果表明:以5 mL正已烷为溶剂的反应体系中,酶0.123 g,已酸浓度0.3 mol/L,醇酸物质的量之比1.6,硅胶0.6 g,于40℃在...     

Synthesis of monoterpene esters by alcoholysis reaction with Mucor miehei lipase in a solvent-free system

The syntheses of geranyl acetate and citronellyl acetate by alcoholysis reaction catalyzed by immobilized lipase from Mucor miehei was studied for the first time in a solvent-free system. Reactions were carried out at a terpene alcohol/acyl donor molar ratio of 1:5 with Lipozyme at 10% of the total weight of the reactants in a solvent-free system. Incubations were carried out at 55 to 60°C for ethyl and butyl acetates as acyl donors, whereas for methyl acetate the incubation temperature was 40 to 45°C. Excess concentration of acyl donor increases the percentage of geranyl acetate and citronellyl acetate, while excess of terpene alcohol concentration decreases the same. Yields from 75 to 77% molar conversion (90 to 98% conversion, w/w) were obtained after 8 to 28 h of reaction time.     

Optimization of the chemoenzymatic epoxidation of soybean oil

The lipase Candida antarctica (Novozyme 435) immobilized on acrylic resin was used as an unconventional catalyst for in situ epoxidation of soybean oil. The reactions were carried out in toluene. The peracid used for converting TG double bonds to oxirane groups was formed by reaction of FFA and hydrogen peroxide. The reaction conditions were optimized by varying the lipase concentration, solvent concentration, molar ratio of hydrogen peroxide to double bond, oleic acid concentration, and reaction temperature. The kinetic study showed that 100% conversion of double bonds to epoxides can be obtained after 4 h. The addition of free acids was not required for the reaction to proceed to conversions exceeding 80%, presumably owing to generation of FFA by hydrolysis of soybean oil. The enzyme catalyst was found to deteriorate after repeated runs.     

Deactivation and regeneration of TS-1/SiO2 catalyst for epoxidation of propylene with hydrogen peroxide in a fixed-bed reactor

TS-1/SiO₂ catalyst for the epoxidation of propylene with hydrogen peroxide in a fixed-bed reactor has been investigated. The catalyst activity decreases gradually with the online reaction time, but the selectivity of propylene epoxide is kept at about 93%. The fresh, deactivated and regenerated catalysts were characterized with X-ray diffraction, Fourier transform infrared spectroscopy, ultra-violet-visible diffuse reflectance, Brunner-Emmett-Teller method and thermogravimetric analysis, and the deactivated catalyst was regenerated with H₂O₂/methanol solution. Compared with the fresh catalyst, both the framework structure and the content of titanium in the framework of the deactivated and regenerated TS-1/SiO₂ catalysts were not changed. The major reason of the catalyst deactivation was the blockage of the channels of the catalyst by bulky organic by-products, which covered the active centers of titanium in TS-1. The deposited materials on the deactivated TS-1/SiO₂ catalyst could be removed by treatment with hydrogen peroxide/methanol solution or pure methanol; the higher the treatment temperature and the higher the concentration of H₂O₂ in methanol, the higher the extent of the regeneration. The regeneration treatment did not influence the product selectivity in the propylene epoxidation.     

ACETIC ACID AS AN OXYGEN CARRIER BETWEEN TWO PHASES FOR EPOXIDATION OF OLEIC ACID

Acetic acid was found to be an effective oxygen carrier for epoxidation of oleic acid. The reaction model of oleic acid epoxidation in the two-phase reaction system was systematically analyzed and the rate determining step was experimentally identified.

The results indicated that the rate of oxidation of the unsaturated acid was independent of the concentration of oleic acid and depended on the mixing rate and the rate of formation peracetic acid which in turn depended on the concentration of acetic acid, strength of acid catalyst and the oxygen source, hydrogen peroxide. In the region of reaction control, the rate equation of epoxidation was found to be

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where k = 2.98 × 10^-2 M^-2 min^-1 at temperature of 35^°C.     

Epoxydationen mit Peressigsäure I: Zur Kenntnis der Peressigsäure und vergleichende Epoxydationen von Sojabohnenöl

Epoxidations with Peracetic Acid I: The Peracetic Acid and Related Epoxidations of Soybean Oil Progressive formation of peracetic acid by the action of hydrogen peroxide on acetic acid was studied. In the presence of ethyl acetate and by employing acetic anhydride, water free peracetic acid was obtained. In the epoxidation of soybean oil the maximum epoxide content of the same is dependent on the reaction conditions, especially on the degree of homogeneity of the reaction partners and the acidic catalyst.     

水合肼中间体丁酮连氮的合成工艺研究

以丁酮、氨气和过氧化氢为原料,研究了在催化剂条件下水合肼中间体丁酮连氮合成的不同工艺条件;考察了催化剂种类及其用量、反应时间、反应温度、双氧水用量各因素对反应收率的影响,结果显示,当催化剂选用甲酰胺,催化剂用量0.5mol,反应时间6h,双氧水用量为0.5mol时,反应温度60℃,丁酮连氮收率达到83.49%。     

Optimization and kinetic modeling of lipase catalyzed enantioselective N‐acetylation of ( ± )‐1‐phenylethylamine under microwave irradiation

BACKGROUND: Optically pure amines are used in the fine chemical industry as resolving agents, chiral auxiliaries, and chiral synthetic building blocks for pharmaceuticals as well as agrochemicals. Lipase‐catalyzed kinetic resolution of ( ± )‐1‐phenylethylamine with ethyl acetate as an acyl donor was achieved using immobilized lipase (Novozyme 435) as a biocatalyst under microwave irradiation. RESULTS: Response surface methodology was employed with a four‐factor‐three‐level Box‐Behnken design to evaluate the effect of synthesis parameters (speed of agitation, enzyme loading, temperature and acyl donor:amine molar ratio) on conversion, enantiomeric excess, enantioselectivity and initial rate. The optimum reaction conditions obtained were mole ratio of acyl donor:amine 1:1, temperature 49.86 °C, 0.03 g of catalyst loading and 345 rpm speed of agitation, giving 49.12% conversion, 78.83% enantiomeric excess and an enantioselectivity of 38.21. R‐stereopreference of lipase was analyzed in detail from the aspects of enzymatic kinetic mechanism and reaction activation energy of both enantiomers. CONCLUSION: Novozyme 435 was found to be the most active chiral catalyst for resolution of ( ± )‐1‐phenylethylamine under microwave irradiation. Statistical analysis was satisfactorily used to determine the optimum reaction conditions. It was found that lipase has R‐stereopreference and the reaction matches the Ping Pong Bi Bi mechanism with dead‐end inhibition of 1‐phenylethylamine. Copyright © 2011 Society of Chemical Industry