Binary Fatty Acid Mixtures Research Articles

Experimental determination of thermal conductivity of fatty acid binary mixtures and their shape-stabilized composites

Thermal conductivity is an essential property to understand the rate of charging/discharging of thermal energy storage systems, but there is still a lack of experimental studies in this field. The temperature dependence of thermal conductivity of eutectic mixtures capric/myristic acid (CA/MA), lauric/myristic acid (LA/MA), and palmitic/stearic acid (PA/SA), as well as their respective shape-stabilized forms (SS-PCMs), were measured by the hot wire technique. Thermal conductivity presented a linear correlation with temperature for all the materials. Besides, the thermal conductivity of the samples was compared with a commercial SS-PCM finding out that the SS-PCMs produced by the authors exhibit higher thermal conductivity than the commercial sample, with an increase between 10.57% and 33.33%. In addition, the minerals that comprise the clay were acquired and their effect on the thermal conductivity on the support studied. Between the crystalline phases, kaolin governed the thermal conductivity of the support. Afterward, kaolin additions were made, resulting in an increase of thermal conductivity between 6.49% and 17.68% of the SS-PCM. Thus, the novelty of this study relies, first, on the experimental data obtained of thermal conductivity, and second, on the study of the effect of some minerals in the overall thermal conductivity of the samples.

Measurements and Prediction of Melting Temperature and Eutectic Point of Binary Fatty Acids Based on Wilson Activity Model

There is a great technical interest in solid-liquid equilibrium (SLE) of binary fatty acids. Mainly, these substances are used for the design, development, and operation of many industrial processes because of the application in many manufacturing fields such as the cosmetic, pharmaceutical and biotechnology industries. In this study, an approach is presented for binary fatty acid mixtures to estimate the melting temperatures as a function of mole fraction in the solid-liquid phase equilibrium. Derivation of the Wilson model was developed to predict the melting temperatures and latent heat to achieve eutectic points of capric acid, undecylic acid, pentadecylic acid, and margaric acid binary mixtures. The results showed that in the all binary mixtures, the eutectic point is near to a lighter compound except capric+undecylic acid because of lower melting temperature of undecylic acid than capric acid. Comparison of experimental and thermodynamic studies revealed the low deviations between measured and calculated values obtained in this study.

Determination and measurement of solid–liquid equilibrium for binary fatty acid mixtures based on NRTL and UNIQUAC activity models

The estimation of solid–liquid phase equilibrium is important for the design, development, and operation of many industrial processes because of application in many manufacturing fields such as cosmetic, pharmaceutic, and biotechnology industries. In this work, we measured solid–liquid phase equilibrium of six fatty acid binary mixtures using the DSC technique and developed thermodynamic approaches for binary fatty acid mixtures to estimate melting temperatures as a function of mole fraction in solid–liquid phase equilibrium. Derivation of NRTL and UNIQUAC activity models was developed to predict melting temperatures and latent heat to achieve eutectic points of undecylic acid, pentadecylic acid, margaric acid, and stearic acid six pairwise binary mixtures. The fatty acids eutectic mixtures are appropriate for heat water systems, phase clothes, concrete, and other similar applications. The results showed low deviations from experimental data measured in this study.

Research on proportion and thermal storage property of the shape stabilized fatty acid

In the paper, four kinds of fatty acid binary mixtures and liquid paraffin and lauric acid binary mixture were prepared. Fatty acid binary mixtures were made of capric acid and myristic acid, lauric acid, palmitic acid and stearic acid. High-density polyethylene was used as supporting material to prepare the shape-stabilized phase change materials. The 25 kinds of shape stabilized phase change materiasl samples were prepared by adding fatty acid mixtures to high density polyethylene according to the mass addition ratios of 50%, 60%, 70%, 80% and 90%.The phase change temperatures, the phase change latent heats, the uniformity and stability of the 25 kinds of shape-stabilized phase change materials were studied experimentally by using differential scanning calorimeter(DSC), the aim was to find suitable phase change materials for phase change wall energy storage. The results showed that the phase change temperatures and the phase change latent heats were related to the components and contents of fatty acids. The optimum content of fatty acid in the shape stabilized phase change materials was 70%. The homogeneity and stability of the shape stabilized fatty acid phase change materials were better, and they are suitable for use in phase change wall. The results in this paper can provide references and basis for the application of fatty acid phase change materials in the wall.

Experimental study on thermal storage performance of binary mixtures of fatty acids

We selected five kinds of fatty acids including the capric acid, stearic acid, lauric acid, palmitic acid and myristic acid and mixed them to prepare10 kinds of binary mixtures of fatty acids according to the predetermined proportion,tested the phase change temperature and latent heat of mixtures by differential scanning calorimetry(DSC). In order to find the fatty acid mixture which has suitable phase change temperature, the larger phase change latent heat and can be used for phase change wall. The results showed that the phase change temperature and latent heats of the binary mixtures of fatty acids decreased compared with the single component;The phase change temperature of the binary mixtures of fatty acids containing capric acid were lower, the range was roughly 20∼30°C,and latent heat is large,which are ideal phase change materials for phase change wall energy storage;The phase change temperature of the binary mixtures consisting of other fatty acids were still high,didn’t meet the temperature requirements of the wall energy storage.

Effect of Binary/Ternary Fatty Acids Ratio and Glycerin on the Phase Behaviors of Soap Solutions

AbstractPhase behaviors of liquid soaps prepared with single myristic acid, binary fatty acid mixtures and ternary fatty acid mixtures (with 30% total fatty acids) are described. The influence of glycerin on the phase behaviors of ternary soaps is discussed. Phase behaviors were characterized by combining pH, viscosity, polarization microscopy, X‐ray scattering and differential scanning calorimetry (DSC) analysis. The results showed that the kind and proportion of fatty acids played key roles in the phase behaviors of soaps. Glycerin had a significant influence on the phase behaviors of soaps. Liquid and Cub + Hex (cubic and hexagonal phase) phase were stable, while Liq + Crystal (liquid micelle and crystal phase), Liq + Lam (liquid micelle and lamellar phase), Liq + Hex + Lam (liquid micelle and hexagonal and lamellar phase) phases displayed separation regions, Glycerin was investigated to improve the stability of separation phases for two weeks, appropriate percentage of the fatty acids in soaps application.

Solid liquid phase diagrams of binary fatty acid mixtures—Palmitic/stearic with oleic/linoleic/linolenic acid mixture

The solid liquid phase diagrams of binary mixtures of the five main saturated and unsaturated fatty acids present in most edible plant oils have been determined in this paper. These binary mixtures comprise of a saturated fatty acid, either palmitic (C16:0) or stearic (C18:0) and an unsaturated one, oleic (C18:1), linoleic (C18:2) or linolenic (C18:3) acid. Differential scanning calorimetry (DSC) was used to obtain an overview of the solid liquid transition behaviour including the metastable ranges of these mixtures. In order to describe all the phase transformations in these systems, the boundary functions have been determined and compared. Phase diagrams determined, illustrate characteristic behaviour in accordance to literature. This work specifically focuses on to describe the solid liquid transitions of the mixtures and not on every single transition or reaction. This paper contributes to the elucidation of the phase behaviour of these important mixtures which are applied in diverse industries.

Thermal characteristic reliability of fatty acid binary mixtures as phase change materials (PCMs) for thermal energy storage applications

The thermal characteristic reliability of two binary mixtures of fatty acid, myristic acid/palmitic acid/sodium myristate (MA/PA/SM) and myristic acid/palmitic acid/sodium palmitate (MA/PA/SP), were investigated using a thermal cycling test setup for 0, 1000, 2000, 3000, and 3600 heating/cooling cycles. The changes in thermal properties and chemical bonding of both eutectic PCMs were measured using Differential Scanning Calorimetric (DSC) and Fourier Transform Infrared Spectroscopy (FT-IR) analyzer, respectively. MA/PA/SM and MA/PA/SP eutectic mixtures shows only minor changes in phase transition temperature (Tm, Ts) and in latent heat of fusion (ΔHf). Moreover, the chemical bonding structures of these eutectic PCMs show no degradation and the thermal performance of those PCMs shows a good stability after 3600 thermal cycles. Therefore, it is found that the thermal characteristic stability of prepared MA/PA/SM and MA/PA/SP eutectic mixtures were acceptable for long term performance and economic feasibilities used as a phase change material (PCM) for thermal energy storage (TES) application.

Molecular Dynamics and Phase Transitions Behavior of Binary Mixtures of Fatty Acids and Cetyltrimethylammonium Bromide as Studied Via Davydov Splitting of Molecular Vibrational Modes

The 1:1 solid phase complexes of stearic (SA) and behenic (BA) fatty acids (FA) with cationic surfactant cetyltrimethylammonium bromide (CTAB) are prepared from an equimolar ethanol solution of their binary mixtures. A supramolecular complexation between FA and CTAB molecules is proven with FTIR spectroscopy, X-ray diffraction (XRD), and differential scanning calorimetry (DSC). A single-phase layered crystalline structure of both CTAB:SA and CTAB:BA complexes is revealed by XRD. The greatly enhanced thermal stability of the CTAB:FA complexes over the pure FA (by about 40–50oC) is found with DSC along with a number of successive solid-solid phase transitions. The temperature-dependent FTIR study of the Davydov splitting for CH2 rocking (720–730 cm^-1) vibrations revealed a significant difference in the conformational disorder of methylene chains and the molecular packing in successive solid phases of CTAB:SA and CTAB:BA complexes. Our research provides a molecular basis for a prospective application of such class of binary mixtures of oppositely charged cationic and anionic surfactants in thermo-sensitive supramolecular systems.

The thermal properties of shape-stabilized fatty acid mixtures used for wallboard

In this paper, four kinds of shape-stabilized phase-change material (PCM), consisting of fatty acid binary mixtures and high-density polyethylene (HDP), were prepared and studied. The fatty acid binary mixtures used in the experiment are CA (20%)–MA (80%), CA (20%)–LA (80%), CA (30%)–PA (70%) and CA (30%)–SA (70%), and they are not eutectic mixtures. HDP was mixed in proportions of 50%, 60%, 70%, 80% and 90% with fatty acid mixtures. The phase-change temperatures, the phase-change latent heats, and the uniformity and stability of the shape-stabilized PCMs were studied experimentally using a differential scanning calorimeter (DSC). The results showed that the suitable mass content of fatty acid mixtures in the shape-stabilized PCM is 70%. The prepared shape-stabilized fatty acid mixtures have good stability and uniformity, and they are the ideal thermal storage materials to be used in wallboard. The results in this paper can provide references and a basis for the application and development of a PCM wall.

Experimental determination of the (vapor + liquid) equilibrium data of binary mixtures of fatty acids by differential scanning calorimetry

(Vapor + liquid) equilibrium (VLE) data for three binary mixtures of saturated fatty acids were obtained by differential scanning calorimetry (DSC). However, changes in the calorimeter pressure cell and the use of hermetic pans with holes ( ϕ = 250 mm) in the lids were necessary to make it possible to apply this analytical technique, obtaining accurate results with smaller samples and shorter operational times. The systems evaluated in this study were: myristic acid (C 14:0) + palmitic acid (C 16:0), myristic acid (C 14:0) + stearic acid (C 18:0), and palmitic acid (C 16:0) + stearic acid (C 18:0), all measured at 50 mm Hg and with mole fractions between 0.0 and 1.0 in relation to the most volatile component of each diagram. The fugacity coefficients for the components in the vapor phase were calculated using the Hayden and O’Connell method [J.G. Hayden, J.P. O’Connell, Ind. Eng. Chem. Process Design Develop. 14 (3) (1975) 209–216] and the activity coefficients for the liquid phase were correlated with the traditional g E models (NRTL [H. Renon, J.M. Prausnitz, Aiche J. 14 (1968) 135–144], UNIQUAC [D.S. Abrams, J.M. Prausnitz, Aiche J. 21 (1975) 116–128], and Wilson [J.M. Prausnitz, N.L. Linchtenthaler, E.G. Azevedo, Molecular Thermodynamics of Fluid-phase Equilibria, River-Prentice Hall, Upper Saddle, 1999]). The sets of parameters were then compared in order to determine which adjustments best represented the VLE.

An approach to calculate solid–liquid phase equilibrium for binary mixtures

An approach is presented to calculate solid–liquid phase equilibrium for binary mixtures, using expressions for the temperature as a function of the molar fraction. For Margules model the expression gives explicitly the temperature, while for other liquid phase activity models an iterative procedure is required to calculate the temperature. The method is very easy to apply and it can be used for mixtures that have peritectic and eutectic points, or just a eutectic point. The approach was applied to five case studies with binary mixtures of fatty acids and triglycerides. The results were in good agreement with experimental data.

Solid−Liquid Equilibrium of Binary Fatty Acid Mixtures

In the present work the phase diagrams of seven fatty acid binary mixtures were obtained by differential scanning calorimetry (DSC). These mixtures were formed by capric acid (C10:0) with lauric acid (C12:0), myristic acid (C14:0), palmitic acid (C16:0), or stearic acid (C18:0) and by lauric acid (C12:0) with myristic acid (C14:0), palmitic acid (C16:0), or stearic acid (C18:0). The spline technique was used to compare the results of this work with prior results available in the literature for some of the investigated systems. The occurrence of the eutectic point in all systems and of the peritectic point in some of the systems was observed. The occurrence of the peritectic point can be associated with the difference in the number of carbon atoms of the fatty acid chains used in the mixture. The approach suggested by Slaughter and Doherty (Chem. Eng. Sci. 1995, 50, 1679−1694) was used to model the solid phase, and the liquid phase was modeled using the Margules-2-suffix, Margules-3-suffix, UNIFAC Dortmund...

Solid–liquid phase behavior of binary fatty acid mixtures: 3. Mixtures of oleic acid with capric acid (decanoic acid) and caprylic acid (octanoic acid)

Solid–liquid phase behavior of binary mixtures of oleic acid (OA)/capric acid (C10A) and OA/caprylic acid (C8A) were investigated by means of differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction. The phase diagram of OA/C10A mixture constructed from the DSC results suggested that a molecular compound with the composition of OA:C10A = 3:2 is formed in a solid phase, and OA and the molecular compound are miscible, while C10A and the molecular compound are completely immiscible. The formation of the molecular compound was supported by the IR spectroscopic observation, and a possible model of the structure was proposed on the basis of X-ray diffraction spectrum in small angle region. This compound formation is characteristic of the OA/C10A mixture, and may be attributed to the similarity of the acyl chain length of C10A to the lengths of Δ- and ω-chains of OA (i.e., the chain segments divided by cis-double bond). The mixture of OA and C8A, whose chain length is close to but shorter than the two chain segments of OA, provided a eutectic-type phase diagram showing a partial mixing of the two components in OA-rich region. Thermodynamic analysis of the liquidus line in the phase diagram exhibits a systematic trend for the non-ideality parameter of mixing with the variation of the chain length difference between OA and saturated fatty acid species.

Solid–liquid phase behavior of binary fatty acid mixtures: 2. Mixtures of oleic acid with lauric acid, myristic acid, and palmitic acid

Solid–liquid phase behavior was investigated for binary fatty acid mixtures composed of oleic acid (OA; cis-9-octadecenoic acid) and saturated fatty acids, lauric acid (LA; dodecanoic acid), myristic acid (MA; tetradecanoic acid), and palmitic acid (PA; hexadecanoic acid), by means of differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR). When the mixture was heated immediately after the solidification from the melt, the heat effect due to the γ-to-α transformation of OA varied depending on the composition of the mixture. However, the mixture subjected to an annealing at the temperature slightly below the melting temperature provided the transformation at constant temperature which corresponds to the γ-to-α transformation temperature of pure OA. This suggests that a solid phase formed by cooling of the melt of the mixture is not in an equilibrium state, but it relaxes to a stable solid during the annealing process. The T– X phase diagrams of these mixtures constructed from the DSC measurements demonstrate that the two fatty acid species are completely immiscible in a solid phase regardless of the type of polymorphs of OA, α- or γ-form. According to a thermodynamic analysis of liquidus line basing on the regular solution model for the melt, the non-ideality of mixing tends to increase with the decrease in the acyl chain length of the saturated fatty acid, although the mixing is rather close to ideal.

Solid–liquid phase behavior of binary fatty acid mixtures: 1. Oleic acid/stearic acid and oleic acid/behenic acid mixtures

Solid–liquid phase behavior of binary fatty acid mixtures was investigated by means of differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR) for the mixture composed of oleic acid (OA) and stearic acid (SA) and that composed of OA and behenic acid (BA). The DSC results provided a monotectic type T– X phase diagram for these mixtures, from which it was suggested that the two fatty acid species are completely immiscible in a solid phase regardless of the two polymorphs of OA, i.e., α-form or γ-form. The solid phase immiscibility was confirmed by the FT-IR observation that the spectra obtained for the mixtures correspond to the superposition of the two spectra for respective components. Thermodynamic analysis of liquidus line demonstrated that OA and SA form an ideal mixture in a liquid phase, whereas the mixing of OA and BA in a liquid phase is slightly non-ideal.

Observation of CO2 in Fourier transform infrared spectral measurements of living Acholeplasma laidlawii cells

In monitoring the time course of conformational disorder by Fourier transform infrared spectroscopy for intact Acholeplasma laidlawii cells grown at 37°C on binary fatty acid mixtures containing oleic acid and for cells grown on pure palmitic acid, an absorption band at 2343 cm−1 was observed. The band intensity was found to increase with time. This band was not observed in the spectra for isolated membranes. It is suggested that the 2343 cm−1 band is due to CO2 dissolved in water, most likely produced at the final point of fermentation of amino acid by this microorganism.

Triacylglycerol assembly from binary mixtures of fatty acids byApiotrichum curvatum

AbstractTo observe how the stereospecific distribution of acyl groups in triglycerides is affected by the composition of fatty acids available for esterification, the oleaginous yeastApiotrichum curvatum was grown on various binary mixture of palmitic, stearic, oleic and linoleic acids as carbon sources, and the yeast triglycerides were analyzed. When oleic acid‐linoleic acid mixtures in various ratios were used as substrates, the yeast grew well, and the composition of the intracellular triglycerides reflected the substrate composition, but more linoleate than oleate was deposited in the triglycerides. Oleate was favored over linoleate at thesn‐2 position of the glycerol. With substrates containing palmitic and stearic acids, the yeast accumulated less oil, and incorporation of stearic acid into the triglycerides also was very limited. When mixtures of palmitic acid‐oleic acid and palmitic acid‐linoleic acid were used as substrates, the yeast triglyceride composition did not reflect that of the substrate, and the accumulation in the yeast of the unsaturated acid in the substrate was favored. Possibly, the yeast had more limited access to solid than to liquid substrates. For oleic acid‐linoleic acid substrates, when the percentages of oleate and linoleate at the three glycerol positions were plottedvs. the percentage of these acyl groups in the total triglyceride, apparent linear relations were observed for most of the range, and the sums of the intercepts and slopes of the three lines for each acyl group were 0 and 3, respectively. Two mathematical models of triglyceride assembly are proposed, both of which fit the experimental data. One model assumes that for a certain proportion of the glycerol molecules, the acyl composition of the threesn positions is rigidly controlled independently of the substrate concentration. The other assumes that the various acyl groups are distributed on the threesn positions of glycerol with different affinities.

Erratum: Compound Formation in Binary Fatty-Acid Mixtures

Erratum: Compound Formation in Binary Fatty-Acid Mixtures

Compound formation in binary fatty-acid mixtures

Long crystal spacings d 1 and short spacings d 2 and d 3 of C 12 –C 14 , C 14 –C 16 and C 16 –C 18 fatty - acid mixtures have been determined using a high resolution X -ray diffractometer in an attempt to elucidate the question of compound formation in these mixtures. Both d 1 and d 3 spacings showed significant changes in relation to the composition of the mixtures whereas d 2 spacings remained practically unchanged. The changes in d 1 and d 3 spacings are interpreted as denoting limited intersolubility of the component fatty acids and partial compound formation. Numerical correlation found between the above changes seems to indicate a shortening of the distance between alternate carbon atoms of the higher melting component in mixtures containing 30 to 70 mol. percent of this component.