环氧生物质油开环催化剂的研究进展

环氧生物质油经醇、酸酐和有机酸等亲核试剂攻击,发生开环反应,制备高性能的生物润滑油。近年来,生物质油环氧化-开环的研究主要集中于分子结构对润滑油性能影响和环氧化催化剂的研发,目前,关于环氧生物质油开环催化剂的综述较少。本文总结了环氧生物质油开环催化剂的研究进展,重点论述了液体酸催化剂、固体酸催化剂、离子液体催化剂等。对现有催化体系进行简要分析,并指出各类催化剂的优点、存在的问题及今后的发展方向。     

环氧脂肪酸甲酯合成的研究进展

介绍以不饱和脂肪酸甲酯为原料,在不同给氧体作用下经环氧化,合成新型环保增塑剂—环氧脂肪酸甲酯的方法.评价了不同给氧体与催化体系对不饱和脂肪酸甲酯环氧化过程和产品性能的影响,并对催化环氧化法制备环氧脂肪酸甲酯进行了展望.     

蒜头果油中长链脂肪酸选择性合成大环内酯

研究了蒜头果油脂中长链不饱和脂肪酸的臭氧氧化以及ω-羟基脂肪酸的催化关环合成大环内酯,考察了臭氧氧化切断双键选择性和大环内酯化选择性。结果表明,不饱和脂肪酸的碳链越长,越有利于臭氧氧化反应和生成大环内酯。蒜头果油脂合成大环内酯的产率为:环十五内酯36.9%,环十三内酯为22.4%,环十一内酯1.0%,并探讨了蒜头果油脂中油酸的反应特性。     

脂肪酸甲酯在甲酸自催化体系中的环氧化和开环反应动力学研究

环氧脂肪酸甲酯是一种性能优良的塑料增塑剂,研究了环氧脂肪酸甲酯合成过程中脂肪酸甲酯在甲酸自催化体系中的环氧化和开环反应动力学。在环氧化反应中,双键和过氧甲酸的反应级数分别为1．43级和1级,反应活化能为56．3kJ／mol;在环氧基团的开环反应中,水对开环反应的作用非常微弱,体系中甲酸对开环反应起主导作用;实验得到在环氧基团和甲酸的开环反应中,环氧基团和甲酸的反应级数分别为1级和1．85级,反应活化能为94．7kJ／mol。     

异氰酸酯/环氧树脂的固化机理

详细研究了异氰酸酯/环氧树脂体系的固化反应和固化机理。采用差示扫描量热法（DSC）和红外光谱法（FTIR）跟踪了异氰酸酯/环氧树脂固化反应过程,定量分析了异氰酸酯、环氧基团和新生成的异氰脲酸酯和口恶唑烷酮的变化。DSC分析结果表明,DSC曲线上出现3个放热峰,说明固化过程中存在至少3种反应;FTIR分析结果表明,在140℃以下固化体系主要发生异氰酸酯的三聚反应生成三嗪环（异氰脲酸酯）;在200℃下,异氰酸酯-NCO基团与环氧基团开环反应生成口恶唑烷酮;在230℃ 下,三嗪环（异氰脲酸酯）进一步与环氧基团开环反应生成口恶唑烷酮。研究了不同温度下环氧基团、异氰酸酯基团、异氰脲酸酯基团、口恶唑烷酮基团随反应时间的变化规律。     

ESBS嵌段共聚物的制备及反应机理研究

利用甲酸和过氧化氢原位生成的过氧甲酸对苯乙烯-丁二烯-苯乙烯（SBS）嵌段共聚物进行环氧化,制备了环氧化SBS（ESBS）。采用FT—IR、GPC、TGA和MFR对ESBS进行了表征,分析了环氧化反应机理。结果表明,在环氧化反应过程中,SBS分子链上聚丁二烯链段1,4-结构中C=C双键的反应活性要大于1,2-结构中C=C双键的反应活性。当反应时间较长时,ESBS会发生环氧基开环副反应。在SBS的环氧化反应初期,会有部分分子链发生断裂生成小分子产物,反应后期会发生环氧基或C=C双键引发的分子间偶联反应,容易形成交联不溶物。     

液体聚丁二烯的环氧化研究

采用过氧甲酸原地法、过氧乙酸原地法及单过氧邻苯二甲酸MPPA法合成了一系列具有不同环氧值的液体环氧化聚丁二烯 (LEPB) ,探索了温度、反应时间对环氧化反应影响的规律 ,并通过开环几率和双键反应程度对环氧化反应进行了详细的讨论。IR和NMR谱结果表明 ,1,4-结构双键的环氧化活性高于 1,2 -结构双键     

用过氧乙酸原位法合成环氧化端羟基聚丁二烯

用过氧乙酸原位法制备了不同环氧值的环氧化端羟基聚丁二烯,研究了反应温度,反应时间,过氧化氢与端羟基聚丁二烯(HTPB)、冰乙酸与HTPB及磺酸催化剂与HTPB质量比等对产物环氧值、羟值及开环率的影响,并用红外光谱对其结构进行了表征.结果表明,用过氧乙酸原位法可有效控制产物的开环率.最佳环氧化反应条件为反应温度50℃、反应时间7 h、过氧化氢与HTPB质量比2.50、冰乙酸与HTPB质量比0.90、磺酸催化剂与HTPB质量比0.15.     

环己烯环氧化反应催化剂研究进展

环氧环己烷作为一种重要的中间体在有机合成中具有很高的应用价值。由环己烯环氧化制备环氧环己烷极易发生烯丙基氧化、环氧环己烷开环水解、深度氧化等副反应,因此利用价廉易得的氧化剂高选择性地生产环氧环己烷仍然是一个挑战。从氧化剂类型入手,对近期环己烯环氧化反应体系中催化剂种类进行总结,提出各种催化体系面临的主要问题。分析表明催化剂上自由基激发位点、酸性位点是造成环己烯烯丙基氧化、环氧环己烷开环水解副反应产生的主要原因,为催化剂的设计开发提供研究方向。     

不饱和脂肪酸及其衍生物环氧化研究进展

综述了环氧化不饱和脂肪酸及其衍生物的制备工艺和实验方法,包括过氧酸环氧化法、卤代醇环氧化法、过氧化氢或有机过氧化氢环氧化法、分子氧环氧化法。其中使用过氧酸的方法是工业上使用最为广泛的,可以采用酸或者酶作催化剂;而以过氧化氢为氧化剂的固体催化工艺是目前最有工业化前途的技术。并指出了开发新型、高效、绿色且廉价的催化体系仍是今后的研究方向。     

Revisiting the Enzymatic Epoxidation of Vegetable Oils by Perfatty Acid: Perbutyric Acid Effect on the Oil with Low Acid Value

Enzymatic epoxidation of vegetable oils in the presence of free fatty acids has been well studied in recent years, by mainly using long chain fatty acids (e.g., stearic acid) as the active oxygen carrier. However, for the previous enzymatic processes, the acid value (AV) of final epoxidized oils using long chain fatty acids is high, and the free fatty acid is not easily removed in the post treatment with water. Aiming at developing a more sustainable process, enzymatic epoxidation of sunflower oil was revisited using different free fatty acids catalyzed by Novozym 435 (lipase B from Candida antarctica, provided by Novozymes, Bagsvaerd, Denmark). When long chain stearic acid was introduced into the epoxidation in toluene solvent, the epoxy oxygen group content (EOC) of 6.41 ± 0.19 % was obtained. Due to the poor water solubility of stearic acid, the AV of the final epoxidized oil product was very high (53.40 ± 1.34) after it was washed with water. Alternatively, current study shows that the epoxidation process using short chain butyric acid produced the final epoxidized oil with lower AV of 2.57 ± 0.11. When the enzymatic epoxidation of sunflower oil was optimized in the presence of butyric acid and Novozym 435, EOC of 6.84 ± 0.21 % was obtained, reaching an oxriane conversion of 96.4 ± 3.0 %. Therefore, introducing short chain butyric acid as an active oxygen carrier will provide an alternative to the present enzymatic epoxidation process and produce the desired epoxidized oil products with much lower AV only after simple water‐treatments, which will make the enzymatic epoxidation more attractive.     

Liquid–Liquid Equilibrium for Systems Containing Epoxidized Oils,Formic Acid,and Water: Experimental and Modeling

Epoxidized oils are eco-friendly plasticizers, which are industrially produced through the epoxidation reaction in a formic acid-hydrogen peroxide autocatalyzed system. The fundamental knowledge to describe the phase equilibrium of systems after epoxidation reaction is lacking, which is crucial for the design of the purification facilities. This work reported experimental data for the liquid–liquid equilibrium of three systems, i.e., epoxidized fatty acid methyl esters + formic acid + water, epoxidized fatty acid 2-ethylhexyl esters + formic acid + water, and epoxidized soybean oil + formic acid + water, in the temperature range (303.15–348.15) K under atmospheric pressure. The results indicated that the liquid–liquid equilibrium constant of formic acid in the systems followed the order of epoxidized fatty acid 2-ethylhexyl esters > epoxidized fatty acid methyl esters > epoxidized soybean oil. Moreover, the obtained experimental data were correlated using nonrandom two liquid (NRTL) and universal quasi chemical (UNIQUAC) models. The maximum root mean square deviation (RMSD) values as low as 0.0052 and 0.0263 were estimated using the NRTL and UNIQUAC model, respectively. The NRTL model is more suitable than the UNIQUAC model to describe the liquid–liquid equilibrium behavior of these ternary systems.     

Monitoring the Epoxidation of Canola Oil by Non-aqueous Reversed Phase Liquid Chromatography/Mass Spectrometry for Process Optimization and Control

Non-aqueous reversed phase liquid chromatography/electrospray mass spectrometry (NARP-LC/ESI–MS) was used to monitor the epoxidation of canola oil by performic acid. The reaction was sampled at regular intervals over 28?h and analyzed by NARP-LC/ESI–MS in order to observe the formation of partially epoxidized reaction intermediates and the fully epoxidized products. The experiment focused on the transformation of triacylglycerols (TAG) with 54 carbons in the fatty acyl chains and between 2 and 7 double bonds which account for >93?% of the oil. NARP-LC/ESI–MS allowed determination of the time required for full epoxidation of the oil. It was shown that complete epoxidation of TAG with low numbers of double bonds occurs more rapidly than for those with many double bonds. Furthermore, it was observed that epoxidation of multiply unsaturated TAG occurs via a sequential process in which partially epoxidized intermediates are consumed to form other more highly epoxidized compounds as the reaction proceeds. Data obtained by flow-injection ESI–MS was found to be comparable to that obtained from NARP-LC/ESI–MS for monitoring intermediates and products and could be adapted for in-process reaction monitoring.     

Effects of Vegetable Oil Composition on Epoxidation Kinetics and Physical Properties

In this article, we investigate the role of triacylglycerol composition on the properties of epoxidized vegetable oils and the kinetics of the epoxidation process under conditions comparable to commercial epoxidation. Commodity soybean oil (24% oleic acid, 50% linoleic acid, and 7% linolenic acid), high‐oleic soybean oil (75% oleic acid, 8% linoleic acid, and 2.5% linolenic acid), and linseed oil (11% oleic acid, 15% linoleic acid, and 64% linolenic acid) were each epoxidized to various extents. Epoxidation rate, viscosity, differential calorimetry, and X‐ray diffraction data are presented for these oils and interpreted in the context of their fatty acid profile (mostly oleic, linoleic, or linolenic). While fully epoxidized soybean oil is widely commercially available and used in an increasing array of industrial applications, information relating to partially epoxidized oils and epoxidized oils of other cultivars is less well known.     

Epoxidation ofLesquerella andLimnanthes (Meadowfoam) oils

Lesquerella gordonii (Gray) Wats andLimnanthes alba Benth. (Meadowfoam) are species being studied as new and alternative crops. Triglyceride oil from lesquerella contains 55–60% of the uncommon 14-hydroxy-cis-11-eicosenoic acid. Meadowfoam oil has 95% uncommon acids, includingca. 60%cis-5-eicosenoic acid. Both oils are predominantly unsaturated (3% saturated acids), and have similar iodine values (90–91), from which oxirane values of 5.7% are possible for the fully epoxidized oils. Each oil was epoxidized withm-chloro-peroxybenzoic acid, and oxirane values were 5.0% (lesquerella) and 5.2% (meadowfoam). The epoxy acid composition of each product was examined by gas chromatography of the methyl esters, which showed that epoxidizedL. gordonii oil contained 55% 11,12-epoxy-14-hydroxyeicosanoic acid, and epoxidized meadowfoam oil contained 63% 5,6-epoxyeicosanoic acid, as expected for normal complete epoxidation. Mass spectrometry of trimethylsilyloxy derivatives of polyols, prepared from the epoxidized esters, confirmed the identity of the epoxidation products and the straightforward nature of the epoxidation process. Synthesis and characterization of these interesting epoxy oils and derivatives are discussed.     

A rapid method for concentrating highly unsaturated fatty acid methyl esters in marine lipids as an aid in their identification by GLC

The selective solubility of unsaturated fatty acid methyl esters in nitromethane at temperatures down to −20C can be used to concentrate highly unsaturated methyl esters. With a typical sample of marine oils methyl esters having an iodine value of 110–190, a concentrate can be ready for GLC analysis in an hour or less and the nitromethane layer can be injected directly for analysis in GLC apparatus with ionization detectors. Examples of the use of the method in the identification of component fatty acids in herring oil are given.     

Studies on Herbaceous Seed Oils XI

Seeds from eight species were analysed by standard procedures for oil and protein contents. The fatty acid composition of the oils was determined by GLC. Five species were found to contain oils above 20% and none of them is rich in protein. Some of the oils have a composition fairly similar to the oils at present in common use. Five seed oils are interesting in having more than 50% of saturated acids of the total fatty acids. T. involucrata seed seems to be a promising species because of its high oil and linoleic acid (61.7%) contents.     

Chemoenzymatic epoxidation of unsaturated fatty acid esters and plant oils

In the presence of an immobilized lipase fromCandida antacrtica (Novozym 435^R) fatty acids are converted to peroxy acids by the reaction with hydrogen peroxide. In a similar reaction, fatty acid esters are perhydrolyzed to peroxy acids. Unsaturated fatty acid esters subsequently epoxidize themselves, and in this way epoxidized plant oils can be prepared with good yields (rapeseed oil 91%, sunflower oil 88%, linseed oil 80%). The hydrolysis of the plant oil to mono- and diglycerides can be suppressed by the addition of a small amount of free fatty acids. Rapeseed oil methyl ester can also be epoxidized; the conversion of C=C-bonds is 95%, and the composition of the epoxy fatty acid methyl esters corresponds to the composition of the unsaturated methyl esters in the substrate. Based partly on a lecture at the 86th AOCS Annual Meeting & Expo, San Antonio, Texas, May 7–11, 1995.     

The effect of fatty acid composition on the acrylation kinetics of epoxidized triacylglycerols

Epoxidized oils, epoxidized triacylglycerols, and epoxidized fatty acid methyl esters were made by reaction with performic acid formed in situ. The extent of epoxidation was ca. 95% for all of the epoxidized samples, as determined by ¹H nuclear magnetic resonance. The epoxidized samples were reacted with an excess of acrylic acid for different reaction times. The acrylation reaction was found to have a first-order dependence on the epoxide concentration for all oils, pure triacylglycerols, and fatty acid methyl esters. However, the rate constant of acrylation was found to depend on the composition of the epoxidized material. The acrylation rate constant for 9,10-epoxystearic acid was 96 L²/(mol²·min). The rate constant of acrylation for the epoxides on 9,10,12,13-diepoxystearic acid was 60 L²/(mol²·min). The acrylation rate constant for the epoxides on 9,10,12,13,15,16-triepoxystearic acid was 50 L²/(mol²·min). Thus, the rate constant of acrylation increased as the number of epoxides per fotty acid decreased. Multiple epoxides per fatty acid decrease the reactivity of the epoxides because of steric hindrance effects, and the oxonium ion, formed as an intermediate during the epoxyacrylic acid reaction, is stabilized by local epoxide groups. These results were used to derive an acrylation kinetic model that predicts rate constants from fatty acid distributions in the oil. The predictions of the model closely match the experimentally determined rate constants.     

Polyhydroxy fatty acids and their derivatives from plant oils

A novel process for the industrial production of hydroxylated fatty acids involves epoxidation of plant oils and their derivatives, followed by catalytic epoxy ring opening in the presence of water or other hydrogen donors, such as alcohols, diols, and amines. Depending on the starting material, epoxidation followed by opening of the oxirane ring leads to fatty acids that contain vicinal diol groups or to other substituted hydroxylated fatty acid derivatives. As an example for the preparation of a substituted hydroxylated fatty acid derivative, the reaction of epoxidized rapeseed oil with monobutylamine as hydrogen donor is described. Apart from the intended formation of hydroxyl groups with vicinal aminoalkyl groups, partial aminolysis of the ester compound was also observed. Another example describes the reaction of epoxidized rapeseed oil with different molar proportions of 1,4-butanediol as hydrogen donor. Depending on the molar proportion of the hydrogen donor, interesterification, or intermolecular ether formation were observed as side reactions. The properties of various technical hydroxylated fatty acids and their derivatives, prepared according to this novel process, are given, and potential applications of these products are suggested.