The influence of hydrogen-bond association on the destruction of hydroperoxides in the autoxidation process of oleyl alcohol, oleic acid, and methyl oleate

The autoxidation process of oleyl alcohol, oleic acid, and methyl oleate at 40, 50, and 60 °C was considered with the special stress laid upon the mechanism of cumulating and destruction of peroxidic products. Interpretation of the observed differences was based on the hydrogen-bond association patterns.     

Spectroscopic and dielectric examination of the oleyl alcohol-oleic acid system

The comparison of association was made for the oleyl alcohol-oleic acid systems composed in several molar ratios. The ir spectroscopy and dielectric constant measurements were applied as analytical techniques. It was stated that oleyl alcohol and oleic acid interact in a number of molar ratios giving the hydrogen-bonded associates. In the range of temparatures 30–60 °C the most stable hydrogen-bonded associate is formed in a ratio of alcohol to acid of 9:1.     

Intermolecular Interactions and the Adhesion of Oleic Acid

The method presented by Good, van Oss, and Chaudhury was applied to characterize intermolecular interactions and the adhesion of oleic acid to selected model surfaces. Interfacial tensions of oleic acid were on the order 11–12 mJ/m² in aqueous solutions and 31–32 mJ/m² at air. The dispersive contribution to the surface tension of oleic acid against different neutral interfaces was determined to be 24–31 mJ/m² in air. Contact angles of oleic acid on selected hydrophilic and hydrophobic model surfaces were measured both in air and in aqueous solution. Van der Waals (dispersive) interactions determined the wetting properties of oleic acid in air both on nonpolar and basic surfaces. As expected, the adhesion of oleic acid to hydrophilic surfaces was much lower and to hydrophobic surfaces higher in aqueous environment than in air. The adhesion in aqueous environment is mainly governed by the cohesive and adhesive properties of water. It was concluded that the GvOC method in this case was only capable to give qualitative information about Lewis acid-base and van der Waals properties of surfaces and liquids, an important limiting factor being the asymmetry of oleic acid and the common probe liquids (diiodomethane and water).     

Adsorption of oleic acid at sillimanite/water interface

The interaction of oleic acid at sillimanite-water interface was studied by adsorption, FT-IR, and zeta potential measurements. The isoelectric point (IEP) of sillimanite obtained at pH 8.0 was found to shift in the presence of oleic acid. This shift in IEP was attributed to chemisorption of oleic acid on sillimanite. Adsorption experiments were conducted at pH 8.0, where the sillimanite surface is neutral. The adsorption isotherm exhibited a plateau around 5 micromol/m2 that correspond to a monolayer formation. Adsorption of oleic acid on sillimanite, alumina, and aluminum hydroxide was studied by FT-IR. Chemisorption of oleic acid on the above substrates was confirmed by FT-IR studies. Hydroxylation of mineral surface was found to be essential for the adsorption of oleic acid molecules. These surface hydroxyl sites were observed to facilitate deprotonation of oleic acid and its subsequent adsorption. Thus protons from oleic acid react with surface hydroxyl groups and form water molecules. Based on the experimental results, the mechanism of oleic acid adsorption on mineral substrate was proposed. Free energy of adsorption was estimated using the Stern-Graham equation for a sillimanite-oleate system.     

Oleic acid-enhanced dissolution of cellulose in high-temperature water

This paper reports, for the first time, the enhanced dissolution of cellulose in subcritical water by addition of a fatty acid. Simply adding oleic acid dramatically promoted the dissolution of cellulose. High-pressure in-situ observation showed that cellulose dissolved in high-temperature water at approximately 500 K, which is 70 K lower than without oleic acid. The yield of oligo and monosaccharides with oleic acid at 473 K was seven times higher than without oleic acid.     

新型Brønsted-Lewis双酸位碳基固体酸的制备及其催化生物柴油的合成

以羧甲基纤维素钠（CMC）与硫酸铁螯合反应生成的螯合物为碳前驱体,以浓硫酸为磺化试剂,制备新型碳基固体酸催化剂。采用红外（FT-IR）、X射线衍射（XRD）、吡啶红外、扫描电子显微镜（SEM）、热重分析仪（TGA）、能谱仪（EDS）对催化剂进行表征。结果表明,该催化剂同时具有Brønsted和Lewis酸位点,是具有双酸位的碳基固体酸催化剂。将其应用到油酸与甲醇的酯化反应制备生物柴油体系中,考察了不同反应条件对油酸转化率的影响。在反应温度为70℃,反应时间为6h,油酸与甲醇物质的量比为1：10,催化剂用量为油酸质量7.5%条件下,油酸的转化率可达到96.8%。此外,对该催化剂的稳定性进行研究发现该催化剂有着良好的重复使用性和疏水性。     

千金子油理化性质及其脂肪酸和挥发油成分分析

对千金子油理化性质进行了系统的分析测试,并利用气相色谱法分析了千金子油脂肪酸及千金子挥发油,结果表明,千金子油中油酸含量最高占78.158%,其次是软脂酸、硬脂酸,分别为8.513%和5.523%;千金子挥发油中油酸、亚油酸和油酸-2-丙三醇酯含量较高,分别为17.747%,15.852%和13.196%.     

脂肪酸在超临界甲醇中的酯化反应研究

超临界甲醇中的酯化和酯交换反应是利用植物油、动物油或废油脂制备生物柴油的新工艺.它的最大特点是不需要添加催化剂,超临界甲醇既是反应媒介,又是反应物.     

卵磷脂-水-油酸体系液晶对胆固醇的增溶作用

Formation and structure of liquid crystal in lecithin-water-oleic acid system were studied. It was found that different from the lecithin-water system, there are two types of liquid crystal present. The lamellar liquid crystal was formed at lower content of oleic acid, the values of interlayer spacing are larger than the values in the corresponding liquid crystal without oleic acid. The inverse hexangonal liquid crysta1 was formed at higher content of oleic acid. In lecithin-water-oleic acid(containing 15℅ cholesterol) system the phase behavior of liquid crystal is similar to that in the lecithin-water-oleic acid system. The solubilization rate of solid cholesterol in lamellar liquid crystal of lecithin-water-oleic acid system is more faster than that of lecithin-water system.     

The uptake of O3 by myristic acid-oleic acid mixed particles: evidence for solid surface layers

The oleic acid ozonolysis in mixed oleic and myristic acid particles was studied in a flow tube reactor using single particle mass spectrometry. The change in reactivity was investigated as a function of the myristic acid concentration in these 2 micron particles. For pure oleic acid aerosol, the reactive ozone uptake coefficient, gamma, was found to be 3.4 (+/-0.3) x 10(-4) after taking secondary reactions into account. At the myristic acid crystallization point, where only 2.5% of the particle is in the solid phase, the uptake coefficient was reduced to 9.7 (+/-1.0) x 10(-5). This dramatic drop in the uptake coefficient is explained by the presence of a crystalline monolayer of myristic acid, through which ozone diffusion is reduced by several orders of magnitude, relative to liquid oleic acid. Scanning electron microscope images of the mixed particles confirm that the particle surface is crystalline when the myristic acid mole fraction exceeds 0.125. The findings of these experiments illustrate that particle morphology is important to understanding the reactivity of species in a mixed particle. The decay of myristic acid during the course of ozonolysis is explained in terms of a reaction with stabilized Criegee intermediates, which attack the acidic groups of the oleic and myristic acids with equal rate constants.     

Compositions of the seed oil of the Borago officinalis from Iran

In order to investigate the composition of borage (Borago officinalis L.) seed oil, this research was performed under the field conditions at Shahriyar and Garmsar zones, Iran during the 2012 planting year. The oil yield of borage was 31.46% and 33.7% at Shahriyar and Garmsar zone, respectively, and nine and eight fatty acids were identified in the seed oil of borage at Shahriyar and Garmsar, respectively – palmitic, linoleic, stearic and γ-linolenic acids were dominant in the seed oil of borage from both zones. Unsaturated fatty acid content was more than the saturated fatty acids in both zones. The ratio of linoleic acid and α-linolenic acid in the borage cultivated at Shahriyar and Garmsar zones was 2.13 and 2.29. The fatty acid profile of Garmsar borage, oleic and oleic/linoleic acid ratio, increased. Locations with different ecological conditions resulted in changes in both seed oil content and fatty acid profile of borage.     

Structure of submonolayer oleic acid coverages on inorganic aerosol particles: evidence of island formation

A series of submonolayer deposition studies of oleic acid on both hydrophobic and hydrophilic surfaces has shown that oleic acid self-associates into islands rather than uniformly covering the surfaces. The studies were performed by vapor deposition on 1.6 mum diameter polystyrene aerosol particles as well as on polystyrene and silica surfaces. The surfaces were investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), ellipsometry and contact-angle goniometry. After timescales of minutes to hours of vapor deposition at 70 degrees C, the oleic acid arranged itself in the form of islands with diameters of about 100 nm. Many of the islands are 25-30 A high, suggesting that the oleic acid sits vertically on the surface. The surface structure of oleic acid on particles is expected to impact on several atmospherically relevant properties such as the reactivity of the oleic acid and the hygroscopicity of the particles.     

Phase transfer of oleic acid capped Ni(core)Ag(shell) nanoparticles assisted by the flexibility of oleic acid on the surface of silver

The phase transfer protocols in vogue for the oleic acid capped silver nanoparticles, viz., salt-induced precipitation and redispersion or phosphoric acid-induced method, are examined and compared thoroughly. A comprehensive evaluation with respect to the mechanistic aspects involved is made and the merits and demerits of the different procedures are delineated. It is found that the salt-induced precipitation and redispersion is more versatile in that the precipitate can actually be redispersed in both aqueous and organic media. However, in terms of mechanism both the routes seem to be very similar wherein the orientational change of oleic acid on the silver surface in the two different environments-organic and aqueous-plays a crucial role in the adaptability of the system to the different environments. Subsequently, this change of orientation of oleic acid on silver surface in aqueous and organic media has been utilized to phase transfer Ni-based nanoparticulate systems. The nascent oleic acid-capped Ni nanoparticles, which were synthesized by a foam-based protocol, were dispersible in water but not in nonpolar organic media such as cyclohexane or toluene. Then, just by coating a thin shell of silver on them we could achieve complete phase transfer of the Ni(core)Ag(shell) from aqueous to organic media following similar procedures used for oleic acid-capped silver nanoparticles. Here, the phase transfer seems to be facilitated by the orientational flexibility of oleic acid on the silver surface as opposed to other metal surfaces as evidenced from the infrared and thermogravimetric analyses of oleic acid-capped Ni and Ni(core)Ag(shell) nanoparticles. This orientation-assisted phase transfer method could be generalized and can be adapted to other systems where, if the nascent nanoparticles cannot be phase transferred as is, they can be coated by a silver shell and oleic acid making them suitable for dispersion in both aqueous and organic media.     

Formation and Characterization of Reversed Micelles Composed of Phospholipids and Fatty Acids

The formation of reversed micellar systems composed of phosphatidylcholine (PC) and fatty acid was newly demonstrated by a significant increase in water content in the organic ethyl oleate phase when the micelles were prepared by the contact method. The solubilized water concentration in the reversed micellar organic phase reached 3 wt%. The new systems are expected to be used as highly biocompatible reversed micellar systems. The structure of the reversed micelles composed of PC and oleic acid was characterized by determining the water concentration and by small-angle X-ray scattering analysis. The reversed micelles composed of PC and oleic acid formed in ethyl oleate were spherical. The radius of gyration was between 30 and 50 Å. The size of the reversed micelles decreased with an increase in the oleic acid concentration and was independent of the PC concentration. Experimental results indicated that the structure of the reversed micellar system was determined by the oleic acid concentration. An increase in the PC concentration caused an increase in the number of reversed micelles of the same size. These reversed micellar systems are expected to be used as solubilization media in pharmaceutical and food industries because they are not toxic.     

Lipozyme 435-Mediated Synthesis of Xylose Oleate in Methyl Ethyl Ketone

In this paper, we have performed the Lipozyme 435-catalyzed synthesis of xylose oleate in methyl ethyl ketone (MEK) from xylose and oleic acid. The effects of substrates’ molar ratios, reaction temperature, reaction time on esterification rates, and Lipozyme 435 reuse were studied. Results showed that an excess of oleic acid (xylose: oleic acid molar ratio of 1:5) significantly favored the reaction, yielding 98% of xylose conversion and 31% oleic acid conversion after 24 h-reaction (mainly to xylose mono- and dioleate, as confirmed by mass spectrometry). The highest Lipozyme 435 activities occurred between 55 and 70 °C. The predicted Ping Pong Bi Bi kinetic model fitted very well to the experimental data and there was no evidence of inhibitions in the range assessed. The reaction product was purified and presented an emulsion capacity close to that of a commercial sugar ester detergent. Finally, the repeated use of Lipozyme 435 showed a reduction in the reaction yields (by 48 and 19% in the xylose and oleic acid conversions, respectively), after ten 12 h-cycles.     

扁桃油中脂肪酸组成的GC-MS法分析

以正己烷为提取剂,采用超声法提取油脂,经KOH-甲醇甲酯化处理后,以气相色谱-质谱(GC-MS)联用技术鉴定出陕西蒲城3个品种扁桃油中的脂肪酸主要组成为:油酸、亚油酸、9-十六碳烯酸、硬脂酸、棕榈酸,其中不饱和脂肪酸总量占91.4%以上,主要成分油酸占73.3%以上。     

Cleaning Away the Oleic Acid Contaminant from Glass Surface by Negative Glow Plasma

Glass surfaces are contaminated by exposure to overheated oleic acid vapor and then cleaned by low-pressure plasma of a dc glow discharge in either air or argon. In this study, the oleic acid is used as model for hydrophobic organic contaminant and glass as a model for inorganic hydrophilic substrate. The processes of contamination and plasma cleaning are studied by atomic force microscopy (AFM), which revealed formation of oleic acid nanodroplets during contamination and, then, their removal during a few minutes of plasma cleaning. Water contact angle measurements show a much faster effect of plasma cleaning treatment, the contaminated surface changing from slightly hydrophobic to superhydrophilic in less than 30 s. This effect can be attributed to oxidation and hydroxylation of the oleic acid, as indicated by infrared absorption measurements. Also, the AFM indentation of the oleic acid nanodroplets after short plasma treatment indicates solidification of the remnant contaminant material.     

The effect of humidity on the ozonolysis of unsaturated compounds in aerosol particles

Atmospheric aerosol particles are important in many atmospheric processes such as: light scattering, light absorption, and cloud formation. Oxidation reactions continuously change the chemical composition of aerosol particles, especially the organic mass component, which is often the dominant fraction. These ageing processes are poorly understood but are known to significantly affect the cloud formation potential of aerosol particles. In this study we investigate the effect of humidity and ozone on the chemical composition of two model organic aerosol systems: oleic acid and arachidonic acid. These two acids are also compared to maleic acid an aerosol system we have previously studied using the same techniques. The role of relative humidity in the oxidation scheme of the three carboxylic acids is very compound specific. Relative humidity was observed to have a major influence on the oxidation scheme of maleic acid and arachidonic acid, whereas no dependence was observed for the oxidation of oleic acid. In both, maleic acid and arachidonic acid, an evaporation of volatile oxidation products could only be observed when the particle was exposed to high relative humidities. The particle phase has a strong effect on the particle processing and the effect of water on the oxidation processes. Oleic acid is liquid under all conditions at room temperature (dry or elevated humidity, pure or oxidized particle). Thus ozone can easily diffuse into the bulk of the particle irrespective of the oxidation conditions. In addition, water does not influence the oxidation reactions of oleic acid particles, which is partly explained by the structure of oxidation intermediates. The low water solubility of oleic acid and its ozonolysis products limits the effect of water. This is very different for maleic and arachidonic acid, which change their phase from liquid to solid upon oxidation or upon changes in humidity. In a solid particle the reactions of ozone and water with the organic particle are restricted to the particle surface and hence different regimes of reactivity are dictated by particle phase. The potential relevance of these three model systems to mimic ambient atmospheric processes is discussed.     

烷基咪唑啉硼酸酯与常用切削液添加剂的配伍性能研究

在四球试验机和攻丝扭矩模拟评定试验机上考察了新型多功能金属加工液添加剂烷基咪唑啉硼酸酯(MB 1 )与常用金属加工液添加剂复配后的承载、极压和攻丝扭矩试验性能。所选择的常用金属加工液添加剂有 :油性剂 :油酸 ;极压剂 :二硫代氨基甲酸钠。结果表明 ,烷基咪唑啉硼酸酯与上述两种添加剂存在程度不同的复配作用。     

pH-Responsive Aqueous Foams of Oleic Acid/Oleate Solution

Aqueous foams of oleic acid/oleate solution were found to be pH-responsive with pH changes. Detailed characterization of the aqueous foams of oleic acid/oleate solution was conducted with respect to their stability, structure, and pH response. The pH values required for foam circulation were studied through pH adjustment. The foaming and defoaming activities of oleic acid/oleate solution were explained by microscopic analysis and oil defoaming mechanisms. Because of the reversibility of oleic acid losing or receiving protons, the foaming and defoaming cycles could be readily repeated many times.