Viscosity prediction for fatty systems

Viscosity data have been measured as a function of temperature for two pure polyunsaturated fatty compounds (linoleic acid and trilinolein), for two multicomponent fatty systems, for a commercial-grade oleic acid (approximately 80% pure), and for canola oil. The measurements were performed in Cannon Fenske glass capillary kinematic viscometers. The contents of a large data bank, containing viscosity data for saturated, monousaturated, and polyunsaturated pure fatty substances, were correlated by an equation based on the number of carbon atoms and double bonds. By using this equation for pure compounds and the UNIMOD group contribution method for mixtures, the viscosity data for model fatty systems, commercial oleic acid, and canola oil were predicted. The good results obtained in the present work indicate that this approach can be a valuable tool for designing or evaluating chemical process equipment for the oil industry.     

二元有机混合液体闪点的实验研究

纯物质的闪点一般可通过查取文献获得,混合物的闪点则很难查到。由于混合液体在实际生产中有着广泛的应用,因此,掌握混合液体闪点的变化规律对于其在生产、储存和使用场所中的风险评估有重要意义。文中采用MINIFLASH FLPL全自动闪点测试仪,对由16种纯物质(包含醇类、酸类、酯类、酮类、醚类、烷烃类)组成的14组不同组成和配比的二元混合液体(含完全互溶和部分互溶)的闪点进行实验研究。用图示法分析了不同研究体系的二元有机混合物其闪点随配比和组分变化的经验规律,将二元混合液体闪点的变化规律大致划分为4类,并对每一类的闪点变化特征和机理进行了探讨。研究结果不仅为工程上提供了二元混合液体闪点的可靠实验数据,还为混合液体在生产、储存和使用过程中的火灾风险评估与安全管理提供了重要参考。     

基于Eyring绝对速率理论的流体混合物黏度推算

为了建立起一个统一的、可同时应用于纯质与混合物高压黏度计算的绝对速率理论模型,基于此前已有的纯质黏度模型,提出了相应的混合法则,将其扩展至对混合流体的计算当中。为验证模型精度,首先选取了27种纯质流体,通过拟合其黏度数据得到模型参数。随后,对27种二元混合物以及3种三元混合物的黏度进行了计算。其中,对于二元混合物,仍需要引入额外的二元交互参数,可通过拟合混合体系黏度数据得到。结果表明,该黏度模型对所选纯质、二元混合物和三元混合物的黏度均有着较高的计算精度,其相对偏差的平均绝对值分别为1.54%、2.35%和3.86%,最大偏差为8.62%、12.9%和19.7%。最后,将本文模型与自由体积模型进行了比较,其对高黏度和互缔合流体的计算精度均高于后者。     

Viscosities of fatty acids and methylated fatty acids saturated with supercritical carbon dioxide

The viscosities of several types of lipids saturated with supercritical carbon dioxide (SC-CO₂) were measured with a high-pressure capillary viscometer. Oleic acid and linoleic acid were evaluated from 85 to 350 bar at 40 and 60°C. The more SC-CO₂-soluble methylated derivatives of these fatty acids were evaluated from 90 to 170 bar at 40 and 60°C. The complex mixture of anhydrous milk fat (AMF) was evaluated from 100–310 bar at 40°C. The viscosities of the methylated fatty acids saturated with SC-CO₂ decreased between 5 and 10 times when the pressure increased from 1 to 80 bar, followed by a further decrease by a factor of 2 to 3 when the pressure was increased from 80 to 180 bar. The viscosities of the fatty acids and AMF saturated with SC-CO₂ had viscosity reduction similar to the methylated fatty acids between 1 and 80 bar, but they decreased much less between 80 and 350 bar. At constant pressure, the viscosity of the fatty acids and AMF decreased with increasing temperature, whereas the viscosity of the methylated fatty acids increased with increasing temperature. The lipid/SC-CO₂ mixtures were Newtonian, and their viscosities were best interpreted by using the mass concentration of dissolved SC-CO₂ in the lipids and the pure component viscosities.     

Kinematic viscosity of fatty acid methyl esters: Prediction, calculated viscosity contribution of esters with unavailable data, and carbon–oxygen equivalents

Many properties of biodiesel, the mono-alkyl esters of vegetable oils, animal fats or other triacylglycerol-containing feedstocks, are largely determined by its major components, the fatty acid alkyl esters. Therefore, information on the properties of individual components and their interaction is essential to understanding and predicting the properties of biodiesel fuels. Viscosity, which affects flow and combustion of a fuel, is such a property. In previous literature, the effect of the structure of fatty esters on viscosity was discussed. However, these data are largely confined to esters with an even number of carbon atoms in the chain and that are liquid at 40 °C. To gain a better understanding of kinematic viscosity, this work additionally reports data on esters with an odd number of carbons in the fatty acid chain and some unsaturated fatty esters. Furthermore, the kinematic viscosity of some biodiesel fuels is affected by components that are solids at 40 °C. A method based on polynomial regression for determining the calculated viscosity contribution (CVC) of esters that are solid at 40 °C (saturated esters in the C₂₀–C₂₄ range) or esters that are liquids but not available in pure form is presented as these values are essential for predicting the kinematic viscosity of mixtures containing such esters. The kinematic viscosity data of esters are compared to those of aliphatic hydrocarbons in the C₆–C₁₈ range and those of dimethyl diesters. The increase of kinematic viscosity with increasing number of CH₂ groups in the chain is non-linear and depends on the terminal functional groups, chain length and double bonds. To illustrate this effect, carbon–oxygen equivalents (COE) are used in which the numbers of carbon and oxygen atoms are added. A straightforward equation, taking into account only the amounts and kinematic viscosity values of the individual neat components, suffices to predict the viscosity of mixtures of fatty esters (biodiesel) at a given temperature.     

STUDIES OF DYNAMIC VISCOSITY AND GIBBS ENERGY OF ACTIVATION OF BINARY AND TERNARY MIXTURES OF BENZYLCHLORIDE + NITROBENZENE + ISOBUTANOL FROM T = (288.15 TO 313.15) K

Densities and viscosities of ternary mixtures of benzylchloride + nitrobenzene + isobutanol and three corresponding binary mixtures (benzyl chloride + isobutanol, benzyl chloride + nitrobenzene, and nitrobenzene + isobutanol) have been determined over the whole concentration at a temperature range of 288.15 to 313.15 K under atmospheric pressure. Experimental data of resulting mixtures were used to calculate viscosity deviations, Δln η, and excess energies of activation of viscous flow, ΔG*^E, of the ternary system. The calculated data for binary mixtures have been fitted by the Redlich-Kister equation to determine the appropriate coefficients. In order to determine the coefficients of ternary data, Cibulka, Singh, and Nakata equations were used. The results have also provided a test for the Grunberg and Nissan equation for correlating the dynamic viscosities of binary and ternary mixtures with mole fractions.     

Acetone-stable nanofiltration membranes in deacidifying vegetable oil

The separation of different vegetable oil/solvent mixtures with two types of nanofiltration membranes was studied. One type had a PEBAX [poly(amide-b-ether) copolymer] top layer, and the other had a cellulose-type top layer. These membranes were stable in acetone, ethanol, 2-propanol, and hexane, all important to the oleochemical industry. Permeabilities were highest for acetone, ±140 L/m² · h · MPa, and lowest for hexane, which had negligible flux at 2 MPa. Permeabilities decreased with increasing triglyceride or free fatty acid (FFA) concentration. Rejection of triglycerides was constant over the concentration range tested, about 80–95%±5%, depending on the type of membrane used. These properties make membranes applicable for separating triglycerides from acetone by enhancing acetone recovery. Deacidification of triglycerides and FFA mixtures was possible (e.g., fatty acids were retained less than triglycerides). The permeate consisted almost entirely of fatty acids in acetone, and only small traces of triglycerides were found. This makes it feasible to selectively remove the fatty acids and reduce loss of triglycerides normally associated with deacidification.     

Influence of the position of unsaturated fatty acid esterified glycerol on the oxidation rate of triglyceride

The influence of the position of unsaturated fatty acid esterified glycerol on the oxidation rate of triglyceride was investigated at 50 C. Randomized triglycerides used were prepared by random interesterification between saturated and unsaturated monoacid triglycerides using sodium methoxide as catalyst. The monoacid triglycerides used were tripalmitin, tristearin, triolein and trilinolein. The molecular species of the randomized triglycerides were analyzed by high performance liquid chromatography (HPLC) in combination with gas liquid chromatography (GLC) and enzymatic hydrolysis. From the results of oxygen absorption measurement by GLC, the randomized triglycerides were more stable towards oxidation than the triglyceride mixtures which were prepared by mixing the equivalent quantities of the same monoacid triglycerides as used in the random interesterification. This may be due to the decrease in the contents of most unstable unsaturated monoacid triglycerides by random interesterification with saturated monoacid triglycerides. Furthermore, from the results obtained with the detailed analysis of the randomized triglycerides at different stages of oxidation, it became clear that the triglycerides having unsaturated fatty acids linked at the 2-position of glycerol are more stable towards oxidation than those linked at the 1(or 3)-position. The carbon chain length of saturated fatty acids has essentially no influence on the oxidation rates of unsaturated fatty acids esterified in the same glycerol.     

Viscosimetric studies on 2-methoxyethanol + 1,2-dimethoxyethane binary mixtures from −10 to 80°c

The kinematic viscosities (v) were measured for nine binary solvent mixtures of 2-methoxyethanol (ME) + 1,2-dimethoxyethane (DME) at nineteen temperatures ranging from ?10 to +80°C. The experimental data have been used to test some empirical equations of the type v = v(T), v = v(X₁) and v = v(T, X₁). The viscosities of all the mixtures increase from the values of pure DME to that of ME as the mole fraction of ME increases, and always yield a negative excess property (v^E) at all the investigated temperatures. Furthermore, thermodynamic parameters of viscous flow have been evaluated on the basis of the Eyring theory. The excess free energy of activation of viscous flow (ΔG^E) vs X₂ plot suggests the presence of a stable hetero-adduct, having ME : DME = 1 : 1 stoichiometric ratio.     

基于ASOG-VISCO模型的醚类混合溶液黏度预测

基于44种二元含醚类物质混合溶液的运动黏度实验数据,采用ASOG-VISCO黏度模型回归得到了新的基团对O-CH₂,O-CyCH,O-ArCH,O-OH,O-COO,O-CCl₃,O-CCl₄的交互作用参数,所研究溶液体系为醚类与正烷烃、异烷烃、环烷烃、芳香族、醇类、氯仿、四氯化碳和酯类的混合物,黏度计算值与实验值的绝对平均偏差为3.31%。同时,为了验证回归得到的新交互作用参数对醚类混合溶液黏度预测的通用性,对11种其他醚类混合溶液的黏度进行了推算,计算值与实验值的绝对平均偏差为5.95%,可以满足实际工程需要。     

Medium-chain fatty acid-rich glycerides by chemical and lipase-catalyzed polyester-monoester interchange reaction

Medium-chain triglycerides (MCT) that contain caprylic acid (C_8:0) and capric acid (C_10:0) have immense medicinal and nutritional importance. Coconut oil can be used as a starting raw material for the production of MCT. The process, based on the interchange reaction between triglycerides and methyl esters of medium-chain fatty acids by chemical catalyst (sodium methoxide) or lipase (Mucor miehei) catalyst, appears to be technically feasible. Coconut oils with 25–28.3% (w/w) and 22.1–25% (w/w) medium-chain fatty acids have been obtained by chemical and lipase-catalyzed interchange reactions. Coconut olein has also been modified with C_8:0 and C_10:0 fatty acids, individually as well as with their mixtures, by chemical and lipase-catalyzed interchange reactions. Coconut olein is a better raw material than coconut oil for production of mediumchain fatty acid-rich triglyceride products by both chemical and lipase-catalyzed processes.     

Deacidification of olive oils by supercritical carbon dioxide

An investigation of the application of supercritical carbon dioxide (SC-CO₂) extraction to the deacidification of olive oils has been made to verify that the nutritional properties of the oil remain unchanged when this technique is applied. Preliminary runs at 20 and 30 MPa in the temperature range of 35–60°C were performed on fatty acids and triglycerides as pure compounds or mixtures, to determine their solubility in SC-CO₂. The solubility data obtained show that CO₂ extracts fatty acids more selectively than triglycerides under specific conditions of temperature and pressure (60°C and 20 MPa). It has been noted that the physical state of the solutes plays an important role in determining the solubility trends as a function of temperature and pressure. Extraction of free fatty acids from olive oil was performed on samples with different free fatty acid (FFA) contents at 20 and 30 MPa and at 40 and 60°C. Experimental data suggest that the selectivity factor for fatty acids is higher than 5 and increases significantly as the fatty acid concentration of the oil decreases. For a FFA content of 2.62%, the selectivity reaches a value of 16. In order to evaluate any variations in the composition, several SC-CO₂ extractions of husk oil with high FFA content (29.3%) were made. The results show that selectivity is still significant (≈5) and the composition in the minor component of the deacidified oil has not changed. On the basis of the experimental results and preliminary process evaluations, the authors conclude that SC-CO₂ extraction could be a suitable technique for the deacidification of olive oils, especially for oils with relatively high FFA (<10%).     

Applicability of the Perturbed Hard Chain Equation of State for Simulation of Distillation Processes in the Oleochemical Industry. Part I: Separation of Fatty Acids

Abstract

Fatty acids constitute an important group of chemicals with extensive end-use markets, either for their direct uses or for the intermediate uses of their numerous derivatives. These oleochemical products are currently purified or fractionated using distillation at subatomspheric pressures. Due to the increasing interest of the pharmaceutical industry in some fatty acids with high purity, supercritical fluid extraction followed by appropriate fractionation steps are also employed. It would therefore be convenient to utilize a single thermodynamic model that is capable of predicting all thermodynamic properties needed, and covering the whole pressure range which is currently applied in both industries. Different equations of state and activity coefficient models were scanned, and the perturbed hard chain equation of state (PHC-EOS) provided results which are as good as those obtained using activity coefficient models, and in some cases better. Since there are very scarce experimental data on the behavior of binary mixtures containing species with associative tendency, an attempt was also made to incorporate a correlation for the dimerization constants to account for chemical association of these higher carboxylic acids. Using a comprehensive and thermodynamically screened vapor pressure data base, pure component parameters for the C₆-C₂₀ fatty acids were computed. The fitted parameters were incorporated in the PHC-EOS and resulted in good reproduction of binary vapor-liquid equilibria. Calculations of multicomponent mixtures were performed using these binary parameters. A flow-sheeting program was utilized to simulate a distillation process consisting of two integrated columns, operated at subatmospheric pressures, for the purification of different hydrogenated fatty acid feedstocks. The simulated flow rate, concentration, and temperature profiles were compared with some real operating data obtained from a major oleochemical plant. Analysis of this comparison revealed that the PHC-EOS is very well suited for simulating different distillation processes for the purification and fractionation of C₆-C₂₀ fatty acids. Furthermore, the need for more accurate thermodynamic information describing the chemical association of these compounds was also accentuated.     

Partial argentation resin chromatography (PARC): II. Separation of saturated and Mono-, Di-, Tri- and tetraenoic fatty esters

Partial argentation resin chromatography (PARC) was used to separate a mixture of saturated and monoenoic, dienoic, trienoic and tetraenoic fatty esters. A series of columns containing XN1010 sulfonic acid resin silvered in the range of 17~91% of theoretical (meaning 17~91% of the sulfonic acid protons were replaced by silver ions) were prepared and were used to correlate the percentage silver with the separation and the retention times of unsaturated fatty esters.cis-Trienoic and tetraenoic fatty esters were eluted with methanol on PARC columns containing 36 and 17% silver. Partial silvering of the resin improved peak shapes while sample elution time and elution volume were reduced. Application of PARC to the separation of mixtures of fatty acids and mixtures of triglycerides was investigated and found to be not feasible with the present system.     

Simple high performance liquid chromatography methods for monitoring lipase reactions

This paper describes three simple high performance liquid chromatography methods to separate mixtures of free fatty acids, mixtures of different triglycerides and mixtures of all fat classes (monoglycerides, diglycerides, triglycerides and free fatty acids). It is possible with our methods to identify and quantify each peak of the chromatogram. These methods have been designed to monitor lipase reactions. Using a first set of conditions, we have been able to separate five fatty acids: linolenic, linoleic, palmitic, oleic and stearic, without any specific preparation of the samples. With a second set of conditions, we showed that the same mobile phase and the same column could separate both triglyceride species and fat classes. However, in the latter case, a flow gradient was used.     

Palmöle und Palmöl-Fraktionen und ihre analytische Differenzierung

Palm Oils and Palm Oil Fractions and their Analytical Differentiation Due to the increasing production of palm oils and the correlating production of palm oil fractions there is a need to differentiate analytically between palm oils and palm oil fractions. The analytical differentiation of these products on the one hand and the detection of unwanted additions and mixtures on the other hand is intended to be achieved. Palm oils of different origin and palm oil fractions, fractionated by different procedures, were examined in this context. The composition of total fatty acids, fatty acids in 2-position of the triglycerides, slip point, iodine value, composition of triglycerides by gaschromatography as well as saturated triglycerides were determined. The slip point, which can easily be determined, and the palmitic acid content in 2-position of t he triglycerides proved to be most suitable for the analytical practice.     

Self- and mutual diffusion coefficient equation for pure fluids, liquid mixtures and polymeric solutions

Transport properties are important information not only for industrial equipment design but also for many research areas. While there is a well-developed theory for gases at low densities, there is no established theory to calculate diffusion coefficients for dense fluids, especially for polymeric solutions. Recently, a database of 96 self-diffusion coefficient data points were obtained from molecular dynamics (MD) simulations for freely jointed Lennard-Jones chains (LJC) with lengths of 2, 4, 8 and 16 at reduced densities ranging from 0.1 to 0.9 and in the reduced temperature interval of 1.5 to 4. These data were used to develop an equation that correlates MD self-diffusion coefficient points with an overall absolute average deviation of 15.3%. The aim of this work is to show that this equation can be used to calculate diffusivities of pure liquids and liquid mixtures, including polymeric solutions. The proposed equation is used for correlating self-diffusion coefficients for 22 pure real substances and then for predicting mutual diffusion coefficients for 12 binary liquid mixtures. The proposed equation is also used to calculate mutual diffusion coefficients for polymeric systems as: polystyrene-toluene at 110 °C, poly(vinyl acetate)-toluene at 35 °C, and poly(vinyl acetate)-chloroform at 35 and 45 °C. Results show that the model developed here seems to be a promising approach for correlating mutual diffusion coefficients not only for small-molecule systems but also for polymer-solvent systems. One advantage of the equation proposed here is that the parameters have physical meaning and most of them can be estimated without any information on binary diffusion data.     

On the prediction of surface tension for multicomponent mixtures

A prediction method for surface tension of real mixtures was developed based on the Davis theory, and tested with the molecular dynamics simulation results of Mecke et al. (1997) for surface tension of the Lennard‐Jones fluid. An effective Lennard‐Jones potential was introduced for correlating surface tension for real pure liquids and binary liquid mixtures, leading to prediction of surface tension of multicomponent systems, including aqueous mixtures. The overall average absolute percentage deviations (AAPD) obtained in the correlated results for 62 pure liquids, 91 non‐aqueous and 11 aqueous binaries are 0.66, 0.80, and 1.75, respectively. In the prediction of the surface tension for 9 ternary and 4 quaternary systems, using the molecular parameters of pure liquids and the adjustable binary parameters, the overall AAPDs are 1.75 and 1.03, respectively.     

ESTIMATION OF CRITICAL PROPERTIES OF BINARY MIXTURES USING GROUP CONTRIBUTION METHODS

A new method for estimating critical temperature (T_c), critical pressure (P_c), and critical volume (V_c), of both nonpolar and polar binary mixtures displaying continuous critical loci is proposed. The methodology is based on the group contribution concept for estimation of critical constants of pure compounds, and the combining rule concept for estimation of mixture properties. Lydersen group contribution method is used to demonstrate the application of this methodology. The combining rules are formulated and their adjustable parameters are determined using 43 nonpolar and polar binary mixtures including 417 data points for (T_c), 390 data points for (P_c), and 219 data points for (V_c), respectively. The method is then evaluated with 15 independently selected binary mixtures containing hydrocarbons, alcohols, ethers, amine, carbon dioxide, nitrous oxide, sulfur dioxide, chloroform, and hydrogen sulfide. The average deviations of the estimated (T_c), (P_c), (V_c) are 1.60%, 7.26%, and 3.64%, respectively. The present procedure does not require experimentally adjusted interaction parameters for estimation of the critical properties of a given binary mixture.     

A SIMPLE CALCULATION OF THE PRESSURE AND LIQUID MOLE FRACTION AT THE VLE OF ETHANE/LIGHT HYDROCARBON BINARY MIXTURES

An analytical expression for the calculation of the pressure and liquid mole fraction at the VLE of ethane/light hydrocarbon binary mixtures is proposed. The model is based on a simple analytical expression for the vapor pressure of pure non-polar fluids, which, for a given temperature, only requires as input the values of the Lennard-Jones molecular parameters and the acentric factor. A properly modified Lorentz-Berthelot mixing rule is used, the interaction parameters being given as simple functions of the temperature and composition with eight constants for each binary mixture. The model is shown to reproduce accurately and simply the pressure (for a given liquid mole fraction) or the liquid composition (for a given pressure) of six ethane + hydrocarbon systems at different temperatures.