N-heptane System Research Articles

Weighted Network Degree Screening Method for Low-Temperature Combustion Mechanism Reduction.

A new method is proposed for the reduction mechanism used in the low-temperature negative temperature coefficient region on the basis of the statistical degree screening (SDS) method. Dynamic information is used to redefine network structure and exclude the influence of very weak interactions on node degree according to the statistics character of their distribution as edge weight. Representative low-temperature conditions are used to set weight thresholds to redefine the network structure so that an effective low-temperature oxidation mechanism is covered while negligible interactions are overlooked. Then, the reduction mechanism is obtained by the SDS method through screening out the redundant species and corresponding reactions according to the scale-free character of the degree distribution. This weighted network degree screening (WNDS) method is demonstrated in the n-heptane system. The performance of the reduced mechanism is evaluated in a closed homogeneous reactor for the fuel over T = 600-1000 K, P = 1-30 atm, and φ = 0.5-2. Results show WNDS yields a skeletal mechanism with comparable or even better prediction ability over a wide parameter range than those generated by directed relation graph. WNDS is a novel statistical property-based reduction method that is suitable for low-temperature oxidation reduction. Its good reduction application indicates a brand-new angle for large combustion mechanism reduction.

Chemical conversions of free phytosterols during the bleaching of corn oil

Phytosterols have health benefits; however, they are partially removed during the bleaching of corn oil. We evaluated the chemical conversion of free phytosterols (FPs) during bleaching. FP degradation accelerated with increased time and temperature, following a first-order kinetic model. In the n-heptane system, air and activated clay promoted the chemical conversion of the FPs. Sterenes formation was analysed under different conditions using a zero-order kinetic model. The apparent activation energies revealed sterene formation decreasing in the following order: campesta-3,5-diene ≈ stigmasta-3,5,22-triene > stigmasta-3,5-diene. Isomers of the above were not detected, indicating that these sterenes were the only primary products of FPs. The desorption test indicated that the FP loss from corn oil was not only due to FPs being adsorbed the activated clay, but also FPs adsorbed at acidic activated sites being degraded. This study presents a vital scientific foundation for retaining FPs to develop healthier and more nutritious oils.

Batch distillation for separating the acetone and n-heptane binary azeotrope mixture: Optimization and simulation

A batch distillation column is one of several approaches that have been developed to improve the distillation process's performance. Batch and specialty chemical industries require quick and reliable process simulations to predict the extent of separation of mixtures such as volatile natural compounds. Acetone and n-Heptane found in wastewater are usually associated with solvents from the pharmaceutical industry. At 329.11 K, acetone and n-Heptane easily combine to form an azeotropic mixture. The different distillation and separation techniques were used to separate the azeotropic mixture which requires several plates and columns. In the current work, batch distillation was used to study the separation of the azeotropic mixture (Acetone and n-Heptane).It was observed that the desired separation was not possible for the Acetone and n-Heptane system. To overcome this, a third component such as Butyl propionate or Benzene is added to the mixture of Acetone and n-Heptane system. This system was simulated using Equinox Software and Services Pvt. Ltd. licensed Multi Batch Distillation Software (MBDS™).Different thermodynamic models have been studied for the azeotropic mixtures, such as NRTL, UNIFAC I, UNIFAC II, and UNIFAC III. The batch distillation system for separating the Acetone and n-Heptane was optimized. Various operating factors such as the number of plates, reflux ratio, batch times, and distillate rates were investigated. Based on simulation studies, the optimal parameters were determined to be a reflux ratio of 2.2, 19 number of plates, and a total time of 1 h to separate >99 wt % Acetone purity from the azeotropic mixture.

Asphaltene precipitation under controlled mixing conditions in a microchamber

Solvent exchange is a controlled process for dilution-induced phase separation. This work utilizes the solvent exchange method to reveal the effect of the mixing dynamics on the asphaltene precipitation process under 20 different mixing conditions using a model system of n-heptane and asphaltene in toluene. The external mixing between the asphaltene solution and the paraffinic solvent is strictly controlled. We employed high-spatial resolution total internal reflection fluorescence microscope to detect asphaltene precipitates with a resolution up to ∼ 200 nm. A multiphysics model is used to simulate the evolution of oversaturation pulse in the solvent exchange process. Based on the simulation results, we predicted the effect of the flow rate, dimension, orientation of the microfluidic chamber, and temperature on the surface coverage and size distribution of asphaltene precipitates. The model predictions of all factors corroborate with the experimental observations. Local concentration of the solvent and shear forces are found to be the two main reasons for the change of asphaltene precipitation caused by mixing dynamics. However, the influence of thermodynamics is more critical than the mixing dynamics as temperature changes. Through a combination of experimental and simulation studies, this work illuminates the significance of the transportation process for the final morphology of asphaltene precipitates and provides a in-depth insight into the mechanism of mixing dynamics on the asphaltene precipitation. A smart mixing may be to boost new phase formation without excessive solvent consumption.

Exploration of new olefin production process: Effects of the addition of CO2 and H2O on n-heptane pyrolysis

In order to study the new cracking process characteristics of hydrocarbon feedstock to light olefins by direct flue gas heating, the pyrolysis experiments of n-heptane in CO2 and H2O atmosphere were performed in pretreated STS316L flow reactor (ϕ10 mm × 2.5 mm × 700 mm) at a temperature range of 1073–1373 K, pressure range of 0.1–1.0 MPa. By changing the n-heptane flow and system pressure to adjust the residence time, results show that the latter is not conducive to olefin formation, but the residence time range about high olefin formation of the latter is wider than that of the former. Due to the promotion of CO and the high-temperature solubility of CO2, the types and contents of PAHs in tar under H2O&CO2 atmosphere are higher. Based on the analysis of n-heptane cracking products stream, the reactivity of H2O and CO2 gradually appears at high temperature and the reactivity of H2O is significantly higher than that of CO2, resulting in higher yields of H2 and CO. The mainstream of the process is the cracking of n-heptane, in which H2O is the supply source of •OH and •H, and CO2 acts as a coking agent. High olefin yields can be achieved in either H2O-rich or CO2-rich atmosphere, and the ratio of the two needs to be properly regulated.

Ternary Liquid–Liquid Equilibrium Data for the n-Heptane + Toluene + (Butane-1,4-diol or Glycerol) Systems at 298.2, 313.2, and 333.2 K and 0.1 MPa

Liquid–liquid equilibrium (LLE) phase compositions (tie-line data) were experimentally measured and thermodynamically modeled for the systems n-heptane + toluene + (butane-1,4-diol or glycerol) at 298.2, 313.2, and 333.2 K and 0.1 MPa. The direct analytical method was used to obtain the LLE data using a double-walled glass cell. The phase equilibrium samples were quantitatively analyzed using gas chromatography. The ternary systems were successfully correlated using the NRTL and UNIQUAC thermodynamic models. The effectiveness of using butane-1,4-diol or glycerol as an alternative solvent to extract toluene from alkanes was evaluated by determining selectivity and solvent capacity. All systems studied were found to demonstrate type II ternary LLE behavior. The selectivity for the solvents studied was found to be comparable or superior to conventional solvents, but solvent capacities were poor, suggesting that the use of a cosolvent might be required to reduce solvent-to-feed ratios.

Cumene extraction separation from alkanes using DMSO: Influence of the alkane structure

In this study, the liquid-liquid equilibrium of dimethyl sulfoxide (DMSO)-cumene-alkanes (including n-alkanes and cycloalkanes) systems are measured at 30 °C under atmospheric pressure. Following NRTL/UNIQUAC activity coefficient model correlation and the Gibbs energy minimization test are conducted. Moreover, the influence of alkane structure on the extraction results is elaborated. Finally, a set of wave function analyses are enacted to visualize the intermolecular interactions and quantify the physical contribution of different intermolecular effects. These investigations show that: The distribution coefficient and overall selectivity of cumene escalate with the increase of molecular weight, for both linear and cyclic alkane homologues. Meanwhile, the entrainment of alkane in the extraction phase decreases. The aromatic selectivity coefficient β for cycloalkane systems is lower than linear n-alkane with similar carbon number, regardless of more extracted model oil, which owes to high entrainment. The aromatic distribution coefficient Kar for cycloalkanes rises faster and eventually surpasses that of n-heptane system in terms of absolute value, which is verified by UNIFAC simulation. The interactions between cumene and n-alkanes/cycloalkanes are van der Waals interaction, driven by dispersion (70.10∼71.50%) and electrostatic (23.58∼24.66%) effect. As the molecular weight of the alkane increases, the dispersion contribution decreases, while the electrostatic interaction increases.

The Design and Optimization of Extractive Distillation for Separating the Acetone/n-Heptane Binary Azeotrope Mixture.

Acetone and n-heptane are common solvents in the pharmaceutical industry and they have been found in wastewater. Under atmospheric conditions, the mixture of these compounds creates a minimum-boiling azeotrope. The extractive distillation process with a high boiling solvent is commonly utilized to separate the azeotropes in the industry to minimize waste, reuse resources, achieve clean production, and preserve the environment. In this work, extractive distillation was applied to separate the binary azeotropic system of acetone and n-heptane in wastewater using butyl propionate as a solvent. The characteristics of the process are designed and simulated via Aspen Plus. The simulation results showed that to get a distillate containing at least 99.5 mass% acetone, a solvent-to-feed ratio of 1.4, a reflux ratio of 1.5, a number of stages of 30, a feed stage of 26, a solvent stage of 10, and a solvent temperature of 298.15 K were required. The optimum operating parameters of the process were also obtained using the NLP optimization method, with the minimum total annual cost as the objective function. While the process was operating in optimal mode, CO2 emissions were calculated to be 0.0780 kg CO2/kg feed.

Separation of toluene from a toluene/n-heptane mixture using ethylene glycol containing deep eutectic solvents

Deep eutectic solvents (DESs) were synthesized and used to separate toluene from n-heptane. DES3 and DES4 were synthesized using choline chloride, urea, and ethylene glycol with a molar ratio of 1: 2: 1 and methyltriph-enylphosphonium bromide and ethylene glycol with a 1: 3 ratio, respectively. While dynamic viscosity of DES2 ranged from 575.9 to 73.8 over temperatures 293.2 to 323.2 K, respectively, that of DES3 ranged from 219.5 to 39.44 [mPa·s]. The viscosity of both DES3 and DES4 follows the Arrhenius equation with respect to temperature from 293.2 to 323.2 K. The liquid-liquid equilibrium (LLE) of the pseudoternary system of toluene, n-heptane, and DES3 were performed at temperature of 303.2 K at ambient pressure. Another LLE of the pseudoternary system of toluene, n-heptane, and DES4 were was obtained over a temperature range of 298.2–313.2 K with a 10 K interval at atmospheric pressure. The experimental LLE data were correlated using the non-random two-liquid (NRTL) model. DESs were not detected in the raffinate phase, and as a result no further separation process for DES was necessary in the toluene separation process. The values of selectivity in the presence of DES 4 changed in a range from 24.4 to 147.5, however, those in the presence of DES3 from 4.1 to 18.7 at 313.2 K. The values of selectivity of toluene with DES applied in this study were far higher than those with other conventional solvents.

Measurements of critical properties of ethyl propionate with the gasoline components

Ethyl propionate is a good choice as additive to improve the combustion performance of gasoline. In this work, the critical temperature (Tc) and critical temperature (pc) of five binary systems (ethyl propionate + n-hexane, ethyl propionate + n-heptane, ethyl propionate + n-octane, ethyl propionate + n-propanol, ethyl propionate + n-butanol) and one ternary system (ethyl propionate + n-hexane + n-propanol) were measured. The results show that the addition of ethyl propionate increases the Tc of n-hexane, n-propanol and n-heptane while decreases the Tc of n-octane and n-butanol. The binary system of ethyl propionate and n-heptane and the ternary system of ethyl propionate + n-hexane + n-propanol are positive azeotropes. The pc of all studied systems changes linearly with the concentration of ethyl propionate. The applicability of Redlich–Kister equations, Cibulka equations and Singh-Sharma equations were checked.

Liquid-liquid equilibria and mechanism exploration for the extraction of sulfides from FCC naphtha via organic solvent as extractant

Separation of sulfides from fluid catalytic cracking (FCC) naphtha is of great significance for environmental protection. In this work, the organic solvents N-methyl-2-pyrrolidone (NMP), sulfolane (SUL), and their mixtures were selected to extract sulfides (3-methylthiophene) from model FCC naphtha (n-heptane). Correspondingly, the liquid-liquid phase equilibrium (LLE) data of the systems n-heptane +3-methylthiophene + SUL/NMP/(NMP + SUL) were experimentally obtained at 298.15 K and 101.3 kPa. The distribution coefficient and separation factor were calculated to assess the extraction performance of the solvents. The results showed that mixed solvent (NMP + SUL) could be used as a potential solvent to extract 3-methylthiophene due to its suitable selectivity and solubility. Meanwhile, the density functional theory (DFT) method was applied to explore the extraction mechanism of 3-methylthiophene from n-heptane by NMP or SUL. Electrostatic potential (ESP) analysis, interaction energies, and reduced density gradient (RDG) analysis showed that the main interactions between NMP/SUL and 3-methylthiophene were van der Waals and weak hydrogen bond forces. In addition, the LLE data were correlated by the NRTL and UNIQUAC thermodynamic models with the RMSD values were all <0.30%. Also, the binary interaction parameters were regressed which could be applied for the optimization and design of the separation process.

Insight into separation of azeotrope in wastewater to achieve cleaner production by extractive distillation and pressure-swing distillation based on phase equilibrium

There are a large number of azeotropes in the binary system of alkanes and alcohols in the industrial wastewater from the reaction of vanadium pentoxide with alkanes to produce alkylvanadate. In order to protect the environment, utilize resources and clean production, the extractive distillation process with high boiling solvent as extractant is usually used to separate the azeotropes in industrial products. However, some intermediate-boiling solvents compared with the two key components to be separated are used as extractant in extractive distillation. In this work, the binary azeotropic system of n-heptane and isoamyl alcohol in wastewater was separated by extractive distillation with intermediate-boiling solvents, pressure-swing distillation and pressure-swing distillation with thermal integration. The binary interaction parameters of isoamyl alcohol and butyl acetate were obtained by correlating and regressing the experimental data of vapor-liquid equilibrium at atmospheric pressure. Taking total annual cost minimum as the objective function, the optimal design parameters of the three processes were obtained by sequential iteration method. Compared with the extractive distillation and pressure-swing distillation, pressure-swing distillation with thermal integration can save the cost up to 29.38%, increase the thermodynamic efficiency up to 445.39%, reduce the global warming potential up to 39.34% and the decrease the acidification potential up to 39.34%. This work provides an effective reference for better separation of azeotropes and wastewater treatment.

Isothermal Vapor-Liquid Equilibrium Measurement of Isobutanol + Isooctane/N-Heptane Binary Mixtures at Temperatures Range of 303.15-323.15 K

The addition of alcohol as an oxygenated compound in gasoline blends may increase the vapor pressure of gasoline mixture. As a result, the study of vapor-liquid equilibrium for gasoline component and alcohol is necessary. In this study, the vapor-liquid equilibrium of isobutanol – isooctane/n-heptane blends were obtained experimentally at temperatures in the range 303.15 to 323.15 K using modified simple quasi-static ebulliometer. The apparatus was validated by comparing the vapor pressure of pure isobutanol, isooctane, and n-heptane with the published data and giving average absolute deviation (AAD) between experimental and calculated ones with magnitude less than 1.0%. The addition of isobutanol with the mole fraction range from 0.2 to 0.6 would increase the vapor pressure of the isooctane and n-heptane up to 12% and 14% respectively. The vapor pressure of binary mixtures was correlated with the Wilson, Non-random two-liquid (NRTL), and Universal quasi-chemical (UNIQUAC) equations with AAD 1.6%, 1.5%, and 1.7%, respectively for isobutanol + isooctane system and 1.8%, 1.7%, and 2.0%, respectively for isobutanol + n-heptane system. The systems studied show positive deviation from Raoult’s Law.

Measurement and Thermodynamic Modeling of Ternary (Liquid + Liquid) Equilibrium for Extraction of Phenols from Alkane with Furfural

The extraction process as a kind of energy-saving and environmental protection technology can be used to separate phenols from low-temperature coal tar. The liquid–liquid equilibrium (LLE) data regarding ternary systems n-heptane + phenols + furfural were determined experimentally at 303.2, 323.2, and 343.2 K under the atmospheric pressure condition, where phenols refer to phenol, p-cresol, and 2,6-xylenol. The solvent extraction capacity was assessed by the solute distribution coefficient and selectivity. Othmer–Tobias and Bachman equations were utilized to validate the consistency of the measured data, which the linear correlation (R2) ≥ 0.99. Experimental LLE data were correlated utilizing the NRTL and UNIQUAC thermodynamic models with all of the RMSD and AARD values below 0.01, meaning that each ternary system is satisfactorily in agreement at temperatures studied and the NRTL model gives better agreement than the UNIQUAC model for ternary systems.

An efficient method for the preparative separation and isolation of ginkgolic acids from the sarcotesta of Ginkgo biloba L by pH-zone-refining counter-current chromatography coupled with inner-recycling mode

An efficient method for the preparative separation and isolation of ginkgolic acids (GAs) from the sarcotesta of Ginkgo biloba L was developed by combining pH-zone-refining counter-current chromatography (PZRCCC) with inner-recycling mode. Two grams of GAs extract were separated by PZRCCC using a two-phase solvent system of n-heptane–ethyl acetate–methanol–water (2:1:3:1, v/v) with 10 mM HCl added to the upper phase as the retention acid and 10 mM triethylamine (TEA) in the lower phase as the elution base. In a one-step PZRCCC separation, two GA compounds, C15:1 and C17:2, were obtained with purities over 98% along with two mixtures. The mixtures were further separated by inner-recycling CCC mode with n-heptane–ethyl acetate–methanol–acetic acid (5:4:1:1, v/v) as the solvent system. Five main GAs were successfully separated with purities over 98%. The structures of the separated GAs were determined based on standard samples coupled with Electrospray Ionization Mass Spectrometry (ESI-MS) results. This separation method of coupling PZRCCC with inner-recycling CCC is effective for the preparation of GAs from the sarcotesta of G. biloba and could be further applied to separate organic acids of low polarity in other natural products.

Dependence of Interfacial Tension on the Temperature and Concentration of Stearic Acid in a Water–n-Heptane System

The dependence of interfacial tension on the temperature and concentration of surfactant (stearic acid) in a water–n-heptane system is investigated. Studies are performed in the temperature range from room temperature to 100°C without the surfactant and at four different concentrations of it. The dependence of the excess surface chemical potential of stearic acid molecules on temperature and concentration is determined, based on the experimental results.

Optimal selection of operating pressure for distillation columns

Optimal design of distillation columns is complex because of many entangled design variables, such as operating pressure, reflux ratio, number of stages, product specifications, etc. Amongst these parameters, operating pressure is the premise towards more economic performance related to not only capital investment but also energy cost. A common heuristic is to arbitrarily fix the pressure if inexpensive cooling water can be used at condenser. However, it cannot always guarantee an optimum column. The traditional way to obtain the optimum pressure is to perform time-consuming iterative rigorous simulations. That is, basically no handy systematical method is available to quick determine optimum column pressure. To eliminate this research gap, this study is devoted to provide an equation-oriented shortcut optimization model to determine optimum pressure avoiding manual iterative calculation. The proposal pathway can estimate column total annualized cost considering capital and energy costs simultaneously before being used to initialize rigorous design. Feasibility and accuracy of this approach are perfectly verified on Aspen Plus through five case studies — propylene–propane, benzene–toluene, cyclohexane–cyclohexanol, methanol–water, and n-pentane–n-hexane–n-heptane systems.

Electrochemistry in Reverse Microemulsions and the Concentration of the Electroactive Probe

Introduction Reverse microemulsions are homogeneous dispersion of water droplets (1 to 100 nm diameter) in an oil, stabilized by a surfactant. In order to improve their stability, aliphatic alcohols (cosurfactants) are often added to the microemulsions1 . Among the different applications of the microemulsions, the use as a reaction media to synthesize nanoparticles has attracted attention in the last decade2 . Since the size and shape of nanoparticles are directly affected by those of the water droplets in the reverse microemulsions3 , the characterization of the reverse microemulsion is necessary. Among the techniques to characterize a reverse microemulsion, cyclic voltammetry has been proposed as an alternative. For this, it is considered that, in most of the cases, the electroactive probes are insoluble in the oil phase, and accordingly the current will depend on the concentration and the diffusion towards the electrode of the water droplets4 and on the concentration of the probe as well. It is important to point out that in order to obtain reliable results for other systems, the concomitant contribution of these factors must be comprehended. For this, a proposal is founded on: i) the concentration ratio water/surfactant determines the size, and hence the diffusion of the water droplets 5,6 ii) the occupancy number, defined as the number of probe units per water droplets in the reverse microemulsion7 . In this work, the effect that both variables have on the electrochemical behavior of reverse microemulsions is studied. The results suggest that cyclic voltammetry can be used as a characterization method of reverse microemulsions as long as these variables are considered. Methodology Hexadecyltrimethylammonium tosilate (CTAT), n-pentanol, hexanes, potassium ferricyanide and double distilled water were used as received. A platinum microelectrode (25 µm diameter) was used as working electrode, a platinum foil as counter-electrode and a platinum wire as pseudo-reference electrode. The cyclic voltammetries were performed in a potentiostat PGSTAT 128N. The sweep rate was varied between 2 and 5 mV/s. Results It has been proposed that the limiting current in a reverse microemulsion decreases as the water content increases, this is because the droplets are the carriers of the electroactive probe and as they grow they diffuse slower, therefore the electrical current declines as the water content increases. Contrary to the expected, the limiting current clearly has a positive slope, see figure 1, passing through a maximum that changes its location with the amount of the aqueous phase and the probe concentration. As reported in the literature, the parameter that links these two variables is known as the occupancy number, and its physical meaning is the average number of ions contained by each droplet. But in order to choose the best concentration of the probe to be used in the characterization of the reverse microemulsion it is necessary to understand the correlation between the water content, the probe concentration, the occupancy number and the limiting current. Conclusions The limiting current measured in a reverse microemulsion depends on the concomitant effect of the diffusion of the water droplets and the occupancy number. Figure 1. Limiting current as function of the water content for two different concentrations of potassium ferricyanide Bibliography (1) Moldes, Ó. A.; Morales, J.; Cid, A.; Astray, G.; Montoya, I. A.; Mejuto, J. C. Electrical Percolation of AOT-Based Microemulsions with N -Alcohols. J. Mol. Liq. 2016, 215, 18–23.(2) Gutiérrez-Becerra, A.; Martínez-Martínez, F.; Bárcena-Soto, M.; Casillas, N.; Ceja, I.; Prévost, S.; Gradzielski, M.; Escalante, J. I. Direct Synthesis of Different Metal Hexacyanoferrate Nanoparticles in Reverse Microemulsions by Using a Ferrocyanide Functionalized Surfactant. Colloids Surfaces A Physicochem. Eng. Asp. 2014, 444, 63–68.(3) Lemyre, J.-L.; Ritcey, A. M. Synthesis of Lanthanide Fluoride Nanoparticles of Varying Shape and Size. Chem. Mater. 2005, 17 (11), 3040–3043.(4) Charlton, I. D.; Doherty, A. P. Electrochemistry in True Reverse Micelles. Electrochem. commun. 1999, 1 (5), 176–179.(5) Martínez-Martínez, F.; Gutiérrez-Becerra, A.; Casillas, N.; Gradzielski, M.; Escalante, J. I.; Bárcena-Soto, M. Characterization of Reverse Microemulsion Formed with Functionalized Surfactants Based on Ferrycianide Ions. Colloids Surfaces A Physicochem. Eng. Asp. 2018, 541 (January), 10–16.(6) Giustini, M.; Palazzo, G.; Colafemmina, G.; Monica, M. Della; Ceglie, A. Microstructure and Dynamics of the Water-in-Oil CTAB / N-Pentanol / N-Hexane / Water Microemulsion : A Spectroscopic and Conductivity Study. J. Phys. Chem. 1996, 100 (8), 3190–3198.(7) Florez Tabares, J. S.; Correa, N. M.; Silber, J. J.; Sereno, L. E.; Molina, P. G. Droplet–droplet Interactions Investigated Using a Combination of Electrochemical and Dynamic Light Scattering Techniques. The Case of water/BHDC/benzene:n-Heptane System. Soft Matter 2015, 11 (15), 2952–2962. Figure 1

Experimental Vapor–Liquid Equilibria and Thermodynamic Modeling of the Methanol + n-Heptane and 1-Butanol + Aniline Binary Systems

Isobaric vapor–liquid equilibria (VLE) of the binary systems of methanol + n-heptane and 1-butanol + aniline were measured at 85 kPa. The experiments were carried out using an Othmer still with the objective of measuring the equilibrium temperature, as well as the composition of the vapor and liquid phases as determined by gas chromatography analysis. According to the experimental results obtained, both of the binary mixtures studied demonstrate positive deviation from ideal behavior. Furthermore, a point of minimum-boiling azeotrope was observed for the methanol + n-heptane system. The VLE data measured have been verified to be thermodynamically consistent based on the Wisniak modification of the Herington area test for isobaric VLE data. Additionally, the two systems were thermodynamically modeled. Because of the relatively low pressure involved in this work, the modified Raoult’s law was utilized for this purpose. In this regard, the experimental vapor–liquid equilibrium data were correlated with diffe...

Facile and Efficient Acylation of Bioflavonoids Using Whole-Cell Biocatalysts in Organic Solvents

Bioflavonoids have many biological and pharmacological activities, but many of them display low bioavailability after oral administration owing to poor lipophilicity of glycoside forms. To improve their lipophilicity, as well as their bioactivity, a new efficient approach was developed for fatty acyl-modification of four vitamin P-like bioflavonoids (troxerutin, rutin, hesperidin, and naringin) using whole-cell biocatalysts in binary solvent systems. Using troxerutin as a typical important bioflavonoid, the acylation activities of 15 strains of different sources were evaluated and Pseudomonas aeruginosa GIM 1.46 showed the highest acylation activity in nonaqueous mediums. 13C NMR, ESI-MS, and FT-IR analysis confirmed that P. aeruginosa catalyzed acylation of troxerutin to produce troxerutin monopropionate (dominant product) and troxerutin dipropionate. In a binary system of n-heptane and pyridine, the cells showed much higher catalytic activity and operational stability than in other solvents, attributing...