高压二氧化碳介质中酶促油酸甲酯与香茅醇的酯交换反应研究

酶催化反应的介质由水基介质发展到有机溶剂介质是80年代以来酶催化科学的一个重大突破[1],特别是近年来的大量研究表明酶在许多非极性有机溶剂中不仅可以保持其固有的催化活性而且其热稳定性也大大提高。然而,有机溶剂本身的种种缺点和有机溶剂中酶催化反应必然存在的多?..     

华根霉全细胞脂肪酶催化合成油酸油醇酯

 比较了10种不同来源的脂肪酶催化油酸与油醇酯化合成油酸油醇酯的能力,其中华根霉Rhizopus chinensis CCTCC M201021全细胞脂肪酶的催化能力最强,其反应转化率可达到90%以上. 酯化反应的最佳油酸/油醇底物摩尔比为1.5, 最佳油酸浓度为0.3 mol/L, 细胞干粉含水量为3.0%～7.5%时对酯化反应最为有利. 以生物相容性指数logP值为指标选择不同的有机溶剂作为有机相进行酯化反应,发现logP值为3.5～4.5的有机溶剂促进酯化效果较好. 全细胞脂肪酶的pH适应范围很广,最佳pH在9.0左右; 最佳反应温度为30 ℃.     

不同溶剂中酶催化合成油酸酯研究初探

对几种非水溶剂中脂肪酶催化合成油酸酯 (油酸乙酯、油酸正辛酯和油酸油酯 )进行了初步考察。结果表明 ,在环己烷、正庚烷和甲苯等有机溶剂中 ,上述酯化反应都有很高的转化率 ;在所考察的实验条件下 ,超临界CO2 中反应的转化率略比上述有机溶剂中的低 ,但该结果已初步显示以超临界CO2 替代有机溶剂合成油酸酯具有很大的应用潜力。     

含糖聚合物的酶促合成

介绍含糖聚合物的酶促催化合成研究进展，主要包括主链含糖聚糖酯，支链含糖聚合物，中心为糖的星形取合物，硅烷主链含糖聚合物等。主链含糖聚合物直接由酶促催化酯化或酯交换作用制得；支链含糖聚合物由酶促合成糖酯单体及单体的化学聚合两步制得。     

无溶剂体系中固定化脂肪酶Candida sp. 99-125催化合成油酸低碳醇酯

采用固定化脂肪酶Candida sp.99-125在无溶剂体系中催化合成油酸低碳醇酯,考察了加酶量、温度、酸醇摩尔比和醇结构对油酸酯化率的影响。结果表明,加酶量为底物质量的3%,最适温度为20℃,酸与醇摩尔比为1∶1,甲醇对该酶有一定的毒性,由于空间位阻效应,该酶对伯醇具有高选择性,对仲醇、叔醇的选择性低,且对长链脂肪酸催化活性高,对带支链的多元酸、多元醇活性低。该酶重复使用5次,酶活性基本没有降低。与传统的化学法相比,用该酶催化合成酯类化合物的色泽更浅。     

1,3-丙二醇油酸双酯的合成

以对甲苯磺酸为催化剂,油酸和1,3-丙二醇为原料合成了1,3-丙二醇油酸双酯。最佳反应条件为:油酸60 mmol,n(油酸)∶n(丙二醇)=2.1,催化剂对甲苯磺酸的用量为油酸质量的3.5%,带水剂甲苯20 mL,于160℃反应1 h。在优化反应条件下,酯化率98%,收率77%。     

液相色谱-质谱法分析季戊四醇油酸酯

提出了高效液相色谱-质谱法测定单、双季戊四醇油酸酯中单酯、双酯、三酯和四酯的含量。样品经正己烷-异丙醇(9+1)溶剂溶解后,以Lichrospher Si100-5色谱柱(4.6mm×250mm,5μm)为分离柱,以不同体积比的正己烷和异丙醇混合溶液为流动相梯度淋洗。采用总离子流图的峰面积归一化法对单、双季戊四醇油酸酯中单酯、双酯、三酯和四酯的含量进行定量,用质谱法做鉴别。     

聚(碳酸酯-co-磷酸酯)的酶促合成及性能

以猪胰脂肪酶或假丝酵母皱褶酶为催化剂, 100℃下通过本体聚合成功地合成了三亚甲基碳酸酯(TMC)和2-乙氧基-2-氧-1,3-二氧磷杂环戊烷(EEP)的无规共聚物(poly(TMC-co-EEP)). 研究了酶浓度, 聚合反应时间以及共聚单体投料比等因素对共聚物分子量和产率的影响. 随着酶(PPL或CL)浓度的增加, 共聚物分子量降低. 同时, 随着EEP投料比的增加, 共聚物的分子量也降低. 共聚物数均分子量最大可达到10200. 随着共聚单体投料摩尔比(EEP/TMC)从0增加到5︰10, 共聚物的玻璃化温度从-28℃降低到-41.7℃. 体外降解实验表明: 共聚物中磷酸酯含量越高, 降解速率越快.     

有机相中α-氰基-3-苯氧基苄醇乙酯的酶促醇解反应

研究了有机相中脂肪酶催化α-氰基-3-苯氧基苄醇乙酯的醇解化反应。制备α -氰基-3-苯氧基苄醇。考察了酶、溶剂、醇、醇用量、溶剂水含量以及底物浓度等 因素对反应的影响，结果表明Novozym435脂肪酶催化活性最高，经实验确定的最佳 条件为：脱水甲苯为溶剂，正辛醇为酰基受体，正辛醇、酯的摩尔比为1.5:1，酶 量为8 mg/mL时的最佳底物浓度为108.13 mmol/L，在上述条件下反应30 h酯的转化 率 > 96%。     

立体异构单萜醇油酸酯的制备及促透活性评价

本文以互为立体异构体的香叶醇(GER)、橙花醇(NER)为先导化合物,采用酰氯酯化法合成油酸香叶醇酯(GER-dC18)、油酸橙花醇酯(NER-dC18),并考察GER、NER、GER-dC18、NER-dC18作为促透剂对多奈哌齐(DNP)的促透活性差异.通过体外释放试验、红外光谱法和分子模拟技术初步探究其促透机制,...     

皮革的CO2超临界流体脱灰

浸灰和脱灰是皮革制造过程的重要工序。在浸灰工序中,通过高浓度石灰乳液对动物皮的长时间处理,使其纤维介质被溶解,胶原纤维得到分散。脱灰是其后续工序,目的是除去动物皮中吸附和沉积的Ｃａ2+;调节ｐＨ值至中性并使其肿胀状态得以消除;促进鞣铬剂的发渗而与胶原纤维有效结合。常规制革工艺中,铵盐被广泛用作脱灰剂,其缺点是中和作用不充分不能有效除去Ｃａ2+,Ｃａ2+与动物油脂反应会产生“钙斑”,并产生令人不愉快的氨污染环境。而硼酸、甲酸、乙酸、柠檬酸等以单独或组合方式与铵盐一道用于脱灰[1]价格昂贵,还易引起裸皮的酸肿影响皮…     

超临界CO2技术制备微孔聚合物中的基本问题

微发泡聚合物材料以环境友好的超临界CO₂为发泡剂, 具有优异的材料性能. 本文对本课题组的研究工作做了归纳总结, 对聚合物微发泡中CO₂的传质、微发泡过程中泡孔结构参数的变化以及多相/多组分聚合物体系的微发泡行为等内容做了针对性的综述. 结合对聚合物微发泡过程理论模拟研究工作的评述, 展望了超临界CO₂微发泡技术未来的发展方向.     

Sorption and swelling of semicrystalline polymers in supercritical CO2

The equilibrium sorption and swelling behavior of four different polymers—poly(methyl methacrylate), poly(tetrafluoroethylene), poly(vinylidene fluoride), and the random copolymer tetrafluoroethylene–perfluoromethylvinylether–in supercritical CO₂—are studied at different temperatures (from 40 to 80 °C) and pressures (up to 200 bar). Swelling is measured by visualization, and sorption through a gravimetric technique. From these data, the behavior of amorphous and semicrystalline polymers can be compared, particularly in terms of partial molar volume of CO₂ in the polymer matrix. Both poly(methyl methacrylate) and the copolymer of tetrafluoroethylene exhibit a behavior typical of rubbery systems. On the contrary, polymers with a considerable degree of crystallinity, such as poly(tetrafluoroethylene) and poly (vinylidene fluoride), show larger values of partial molar volume. These can be related to the limited mobility of the polymer chains in a semicrystalline matrix, which causes the structure to “freeze” during the sorption process into a nonequilibrium state that can differ significantly from the actual thermodynamic equilibrium. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1531–1546, 2006     

超临界CO_2在化学反应中的应用进展

本文详细地综述了最近几年来有关超临界CO2流体中的化学反应的研究成果，展望了超临界CO2化学反应的开发应用前景，试图让这一崭新的研究领域受到更加广泛的关注。     

用超临界CO2萃取香草兰香料

香草兰是一种多年生藤本热带香料植物 ,有“食品香料之王”的美称 ,经济价值很高 ,要靠进口满足国内需求[1 ] 。在水果制品中添入香草兰 ,可使果香味增浓 ,但不增加热量[2 ] ;香草兰还用于化妆品业、烟草业和药品业等[3] 。它是由提取香草兰豆荚制备的。传统方法是用有机溶剂萃取 ,成本高、费时、溶剂会残留。近 2 0年才发展起来的超临界流体萃取 (Ｓｕｐｅｒｃｒｉｔｉｃａｌｆｌｕｉｄｅｘｔｒａｃｔｉｏｎ ,简称ＳＣＦＥ)技术 ,在天然产物提取以及食品工业的应用方面取得较好效果[4] 。本文用超临界ＣＯ2萃取香草兰香料 ,研究了压力、温…     

超临界CO2萃取香草兰化学成分分析

香草兰 ,学名 :ＶａｎｉｌｌａｐｌａｎｉｆｏｌｉａＡｎｄｒ.,又名香荚兰 ,香子兰 ,属兰科香子兰属 ,是一种名贵的多年生热带藤本植物 ,有独特的香味 ,被称誉为“食品香料之王”。香草兰经加工后 ,是食品工业的重要天然香料 ,也用于烟草业、化妆品业和药物[1,2 ] 。香草兰原产于墨西哥 ,主产国还有马达加斯加、印尼、牙买加等[3 ] 。近年来 ,我国海南、云南等地也大力种植和推广。超临界流体萃取 (ＳｕｐｅｒｃｒｉｔｉｃａｌＦｌｕｉｄＥｘｔｒａｃｔｉｏｎ ,简称ＳＣＦＥ)是近 2 0年发展起来的现代提取分离技术 ,具有工艺简单、成本低、…     

Interaction of pharmaceutical hydrates with supercritical CO2

The aim of this work was to study the solubility in supercritical CO₂ of the hydrated phase of three model drugs, namely theophylline, carbamazepine, and diclofenac sodium, in comparison with the respective anhydrous form. Possible solid-state modifications, stemming from the interaction with supercritical CO₂, were investigated by differential scanning calorimetry, thermogravimetric analysis, hot stage microscopy, Fourier Transform infrared spectroscopy and Karl-Fischer titrimetry. It was found that all three pharmaceutical hydrates exhibited higher solubility in supercritical CO₂ than the relevant anhydrous phases. In the case of theophylline monohydrate, the instability of the crystal phase at the experimental temperature adopted has been evidenced. Diclofenac sodium tetrahydrate represents a peculiar case of chemical interaction with the acid supercritical fluid, mediated by crystal water. This revised version was published online in July 2006 with corrections to the Cover Date.     

Viscosity studies of poly(DL‐lactic acid) in supercritical CO2

The effect of supercritical CO₂ on the viscosity and activation energy to viscous flow of P_DLLA is investigated, using a high pressure parallel plate rheometer, over a range of temperatures (50–140 °C) and pressures (5–12 MPa). The Cross model is fitted to the data to enable calculation of the zero shear viscosity and critical shear rate. A significant decrease in the viscosity is observed on increasing both variables; however, at high temperatures, the pressure effect becomes negligible. An increase in the critical shear rate is also observed on raising the pressure, indicative of a reduction in the relaxation time of the polymer. Manipulation of the Arrhenius equation shows a reduction in the activation energy to viscous flow as the pressure is increased. Together, these results show that the melt processing temperature of P_DLLA can be reduced in the presence of supercritical and high pressure CO₂. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Graft copolymerization of maleic anhydride/styrene onto isotactic polypropylene using supercritical CO2

The free‐radical grafting of maleic anhydride (MAH) and styrene (St) onto isotactic polypropylene (iPP) was studied by thermal decomposition of dicumyl peroxide (DCP) using supercritical CO₂ as a solvent and swelling agent. Several effects of molar ratio of monomer, soaking temperature and time, reaction time, and reaction pressure on the graft degree were discussed. It was found that the addition of St to the grafting system as a comonomer could significantly enhance the graft degree of the grafted PP. Under the optimal reaction condition, the maximum of iPP grafting MAH and St in supercritical CO₂ medium was 10.58%. The chemical structures and properties of grafting copolymers were characterized by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The results showed that the supercritical CO₂ method had noticeable advantages over the existed method when compared, such as a lower temperature, a higher graft degree, easy separation, and environmentally benign. Copyright © 2007 John Wiley & Sons, Ltd.