A correlation for the solubility of hydrocarbons in water

A correlation has been developed for the solubility of C₄ to C₁₀ hydrocarbons in water at 25°C and atmospheric pressure. The excess Gibbs free energy is correlated in terms of an effective molar volume which is related to the actual molar volume adjusted to include the effects of the degree of branching, the number of olefinic and acetylenic bonds and the number of aromatic and cycloalkane rings. The root mean square deviation between 59 correlated and experimental solubilities is 20%. The range of solubilities is from 0.052 to 5150 g hydrocarbon per 10⁶ g water. The correlation provides a rational procedure for the estimation of solubility of other hydrocarbons.     

Description of the mutual solubilities of fatty acids and water with the CPA EoS

Data for the mutual solubilities of fatty acid + water mixtures are scarce and so measurements for seven fatty acid (C₅‐C₁₀, C₁₂) + water systems were carried out. This new experimental data was successfully modelled with the cubic plus association EoS. Using data from C₆ to C₁₀ and the Elliot's cross‐associating combining rule a correlation for the k_ij binary interaction parameter, as a function of the acid chain length, is proposed. The mutual solubilities of water and fatty acids can be adequately described with average deviations inferior to 6% for the water rich phase and 30% for the acid rich phase. Furthermore, satisfactory predictions of solid‐liquid equilibria of seven fatty acids (C₁₂‐C₁₈) + water systems were achieved based only on the k_ij correlation obtained from liquid–liquid equilibria data. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Physicochemical properties of phosphate extracts and mutual solubility of phases in the extraction system with monofunctional aliphatic alcohols

The main physicochemical properties of the extracts, such as density, viscosity, and conductivity, as well as the mutual solubility of the phases in the ROH-H₂O and ROH-H₂O-H₃PO₄ extraction systems, where ROH (R = C₅–C₁₀) stands for higher monofunctional aliphatic alcohols with a different length and structure of the hydrocarbon radical, have been studied in water and aqueous solutions containing phosphoric acid. The properties correlate with the length and structure of the hydrocarbon chain in the aliphatic alcohols, as well as with the concentration of mineral acid in the extracts.     

Solubilities of chlormezanone,metaxalone and methocarbamol in supercritical carbon dioxide

The solubilities of three active pharmaceutical ingredients (APIs) in supercritical carbon dioxide were measured in this study using a semi-flow apparatus. These APIs are chlormezanone (C₁₁H₁₂ClNO₃S), metaxalone (C₁₂H₁₅NO₃) and methocarbamol (C₁₁H₁₅NO₅) that are all used as skeletal muscle relaxants. The solubility data are reported for three isotherms at 308.2, 318.2 and 328.2 K, with the pressure range from 12 to 24 MPa. Most solubility data are within the range of 10⁻⁶ to 10⁻⁴ mole fraction for each API. The crossover phenomena were observed from the experimental results for all three systems. These solubility data satisfied the thermodynamic consistency tests. They were then correlated using three semi-empirical models. With the optimally fitted binary interaction parameters, satisfactory correlation agreement is presented for each binary mixture.     

Alkanes in aqueous systems. II. The accommodation of C12−C36 n-alkanes in distilled water

The accommodation of n-alkanes in the C₁₂ to C₃₆ range in distilled water was measured as a function of hydrocarbon supply, settling time, filtration pore-size, and mode of introduction. Accommodation levels for individual hydrocarbons generally fell in the range of 0.01 to 100 mg/liter; liquids were accommodated to a greater extent than solids. Settling times of many days sharply reduced the measured accommodation, as did millipore filtration. The accommodation of a given n-alkane showed a strong dependence on the supply of the n-alkane in the equilibrating aqueous system. Binary mixtures showed a limited effect of one alkane on another except in the case of mixtures of a liquid alkane and a solid alkane, in which the presence of the liquid greatly enhanced the accommodation of the solid. Similarly supply ratios were reproduced for accommodated liquid alkanes except in those systems where the supply alkanes separated into co-existing liquid and solid phases with compositions as determined by the phase rule for the particular hydrocarbon system. The accommodated alkane composition was the same as that of the liquid hydrocarbon phase. The same pattern was observed for fused mixtures of n-alkanes in the C₁₂ to C₃₆ range, and on long-term settling there was an over-all, clearcut tendency for preferential accommodation of n-alkanes in the C₁₆ to C₂₀ range at the expense of alkanes with both higher and lower carbon numbers. Contribution No. 349, Research Council of Alberta, Edmonton.     

Pyrolysis of used sunflower oil in the presence of sodium carbonate by using fractionating pyrolysis reactor

Pyrolysis of used sunflower oil was carried out in a reactor equipped with a fractionating packed column (in three different lengths of 180, 360 and 540 mm) at 400 and 420°C in the presence of sodium carbonate (1, 5, 10 and 20% based on oil weight) as a catalyst. The use of packed column increased the residence times of the primer pyrolysis products in the reactor and packed column by the fractionating of the products which caused the additional catalytic and thermal reactions in the reaction system and increased the content of liquid hydrocarbons in gasoline boiling range. The conversion of oil was high (42–83 wt.%) and the product distribution was depended strongly on the reaction temperature, packed column length and catalyst content. The pyrolysis products consisted of gas and liquid hydrocarbons, carboxylic acids, CO, CO₂, H₂ and water. Increase in the column length increased the amount of gas and coke–residual oil and decreased the amount of liquid hydrocarbon and acid phase. Also, increase of sodium carbonate content and the temperature increased the formation of liquid hydrocarbon and gas products and decreased the formation of aqueous phase, acid phase and coke–residual oil. The major hydrocarbons of the liquid hydrocarbon phase were C₅–C₁₁ hydrocarbons. The highest C₅–C₁₁ yields (36.4%) was obtained by using 10% Na₂CO₃ and a packed column of 180 mm at 420°C. The gas products included mostly C₁–C₃ hydrocarbons.     

Predicting phase behavior in aqueous systems without fitting binary parameters I: CP‐PC‐SAFT EOS,aromatic compounds

This study examines an accuracy of CP‐PC‐SAFT attached by the 4C cross‐association scheme and zero values of binary parameters in predicting the high temperature‐high pressure phase behavior in aqueous systems of aromatic compounds containing one and two benzoic rings, CO₂ and cis‐decalin. In spite of the noteworthy complexity of these systems and the entirely predictive nature of the current approach, it correctly predicts the topology of phase behavior and typically yields the quantitatively accurate estimations of critical loci and the hydrocarbon–rich liquid phases in wide range of conditions. The available single phase volumetric data are also predicted accurately. Unfortunately, it is not a case of the water–rich phases exhibiting very small hydrocarbon concentrations. Nevertheless, the model is still capable of capturing the solubility minima characteristic for these phases around the room temperature. Predictions of the recent version of Simplified PC‐SAFT proposed by Liang et al. (2014) are also discussed. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4124–4135, 2017     

Critical evaluation and thermodynamic optimization of the Si-N,Si-C,C-N and Si-C-N systems and its applications to high purity SiC production

Thermodynamic optimization of the Si-N, Si-C, C-N and Si-C-N systems were performed using the CALculation of PHAse Diagrams (CALPHAD) method based on critical evaluation of all available experimental data. The liquid and solid solutions within the Si-C-N system were described using the Modified Quasichemical Model and Compound Energy Formalism, respectively. The Gibbs energies of β-Si₃N₄ and β-SiC were carefully optimized to resolve inconsistencies among existing thermodynamic properties and phase equilibria data. The solubilities of C and N in both solid and liquid Si solutions were critically optimized. Besides, the solubility of N in β-SiC to form a narrow homogeneity range of β-Si(C,N) solid solution is considered for the first time in the present thermodynamic modeling. Based on the present thermodynamic database, experimentally unexplored phase diagrams and thermodynamic properties within the Si-C-N alloys were predicted. As an application of the database, the influences of various operation conditions on high purity SiC production using sublimation process were calculated.     

Intensification of the processes of dehydrogenation and dewaxing of middle distillate fractions by redistribution of hydrogen between the units

The dehydrogenation and dewaxing of hydrocarbons of middle-distillate fractions, which proceed in the hydrogen medium, are of great importance in the petrochemical and oil refining industries. They increase oil refining depth and allow producing gasoline, kerosene, and diesel fractions used in the production of hydrocarbon fuels, polymer materials, synthetic detergents, rubbers, etc. Herewith, in the process of dehydrogenation of hydrocarbons of middle distillate fractions (C₉–C₁₄) hydrogen is formed in the reactions between hydrocarbons, and the excess of hydrogen slows the target reaction of olefin formation and causes the shift of thermodynamic equilibrium to the initial substances. Meanwhile, in the process of hydrodewaxing of hydrocarbons of middle distillate fractions (C₅–C₂₇), conversely, hydrogen is a required reagent in the target reaction of hydrocracking of long-chain paraffins, which ensures required feedstock conversion for production of low-freezing diesel fuels. Therefore, in this study we suggest the approach of intensification of the processes of dehydrogenation and dewaxing of middle distillate fractions by means of redistribution of hydrogen between the two units on the base of the influence of hydrogen on the hydrocarbon transformations using mathematical models. In this study we found that with increasing the temperature from 470 °C to 490 °C and decreasing the hydrogen/feedstock molar ratio in the range of 8.5/1.0 to 6.0/1.0 in the dehydrogenation reactor, the production of olefins increased by 1.45–1.55%wt, which makes it possible to reduce hydrogen consumption by 25,000 Nm³/h. Involvement of this additionally available hydrogen in the amount from 10,000 to 50,000 Nm³/h in the dewaxing reactor allows increasing the depth of hydrocracking of long-chain paraffins of middle distillate fractions, and, consequently improving low-temperature properties of produced diesel fraction. In such a way cloud temperature and freezing temperature of produced diesel fraction decrease by 1–4 °C and 10–25 °C (at the temperature of 300 °C and 340 °C respectively). However, when the molar ratio hydrogen/hydrocarbons decreases from 8.5/1.0 to 6.0/1.0 the yield of side products in the dehydrogenation reactor increases: the yield of diolefins increases by 0.1–0.15%wt, the yield of coke increases by 0.07–0.18%wt depending on the feedstock composition, which is due to decrease in the content of hydrogen, which hydrogenates intermediate products of condensation (the coke of amorphous structure). This effect can be compensated by additional water supply in the dehydrogenation reactor, which oxidizes the intermediate products of condensation, preventing catalyst deactivation by coke. The calculations with the use of the model showed that at the supply of water by increasing portions simultaneously with temperature rise, the content of coke on the catalyst by the end of the production cycle comprises 1.25–1.56%wt depending on the feedstock composition, which is by 0.3–0.6%wt lower that in the regime without water supply.     

Effect of water on the solubilities and mass transfer coefficients of gases in a heavy fraction of fischer-tropsch products

The effects of water on the solubilities, C^*, and volumetric mass transfer coefficients, k_La, for CO, H₂, CH₄ and CO₂ in a heavy fraction of Fischer-Tropsch liquid were examined at elevated pressures and temperatures at different mixing power inputs. For these gases, higher solubilities were measured in the hydrocarbon mixture saturated with water than those obtained in the hydrocarbon free of water. The k_La values for the four gases were slightly affected by the presence of dissolved water in the hydrocarbon mixture; and they were strongly dependent on the power input per unit liquid volume. Two empirical correlations for k_La as a function of turbine speed and pressure are proposed.     

Separation of Multicomponent Hydrocarbon Mixtures Spreading on a Water Surface

Abstract

The separation of multicomponent hydrocarbon mixtures spreading on a water surface is related to the spreading coefficients of the hydrocarbons, taking into account relative volatilities and solubilities. In both synthetic and crude oil systems, the separation can be explained by the differences in spreading coefficients.     

Dissolution of Soap Scum by Surfactant Part I: Effects of Chelant and Type of Soap Scum

The equilibrium solubilities of two model soap scums [calcium stearate and magnesium stearate: Ca(C₁₈)₂ and Mg(C₁₈)₂] were measured in aqueous solutions containing three different types of surfactants: methyl ester sulfonate (MES) as an anionic; alcohol ethoxylate (EO9) as a nonionic; and dimethyldodecylamine oxide (DDAO) as an amphoteric with and without a chelating agent [disodium ethylenediaminetetraacetate (Na₂EDTA)]. The solubility of calcium soap scum was generally higher than that of magnesium soap scum, the exception being some DDAO systems. The use of the DDAO surfactant with the Na₂EDTA chelating agent at high pH gives the highest solubilities of both studied soap scums. The soap scum solubility is on the order of 2,000 times that in water at high pH. The DDAO is the most effective surfactant under all conditions. The MES is more effective than the EO9 at low pH with the opposite trend observed at high pH. The synergism from added chelant is generally greater at higher pH and is greatest for DDAO followed by EO9.     

Solubility of propane in N-formyl morpholine

N-formyl morpholine (NFM) is a solvent that has been used to separate acid gases from gas streams. An advantage of NFM is the high solubility of acid gases compared with the low solubility of light hydrocarbons. The solubility of the light hydrocarbons in NFM is important, as the hydrocarbons constitute a loss to the process, and result in hydrocarbon emissions to the atmosphere. However, there are only a few experimental data sets dealing with the solubility of hydrocarbons in NFM. To provide data to be used in the design of plants in the natural gas processing industry, the solubility of propane (C₃H₈) in NFM was measured at 298.15, 313.15, and 343.15 K at pressures up to 20.15 MPa. The Peng-Robinson equation of state was employed to correlate the experimental data and to obtain binary interaction parameters. The binary interaction parameters were used to obtain the parameters of the Krichevsky-Ilinskaya equation and Henry's law constants for propane were calculated. Henry's law constants for propane were compared with those of hydrogen sulphide, carbon dioxide, methane, and ethane in NFM.     

THE SOLUBILITY OF PARAFFINIC HYDROCARBONS AND THEIR DERIVATIVES IN SUPERCRITICAL CARBON DIOXIDE

The solubilities of twenty-five paraffinic model compounds, octadecane (C₁₈H₃₈) through tetracosane (C₂₄H₅₀) and related monofunctional derivatives, were measured in supercritical carbon dioxide at 310 and 320 K. The derivatives included sulfides, amines, phosphines, ketones and other functional groups. Several of the solutes were liquids at the extraction temperatures and pressures, and both liquid and fluid phase binary composition data are reported in some cases. A systematic attempt was made to explore how the presence of a particular functional group on the solute molecule affected the solubility of the compound relative to the parent hydrocarbon of equivalent chain length.     

Prediction of gas solubility in binary polymer+solvent mixtures

This paper is devoted to a theory of gas solubility in highly asymmetrical mixed solvents composed of a low molecular weight (such as water, alcohol, etc.) and a high molecular weight (such as polymer, protein, etc.) cosolvents. The experimental solubilities of Ar, CH₄, C₂H₆ and C₃H₈ in aqueous solutions of polypropylene glycol and polyethylene glycol were selected for comparison with the theory. The approach for predicting these solubilities is based on the Kirkwood-Buff formalism for ternary mixtures, which allowed one to derive a rigorous expression for the Henry constant in mixed solvents. Starting from this expression, the solubilities could be predicted in terms of those in each of the two constituents and the properties of the mixed solvent. This expression combined with the Flory-Huggins equation for the activity coefficient in a binary mixed solvent provided very accurate results, when the Flory-Huggins interaction parameter was used as an adjustable quantity. A simple expression in which the solubility could be predicted in terms of those in each of the two constituents and the molar volumes of the latter was also derived. While less accurate that the previous expression, it provided more than satisfactory results.     

Predicting Solubility of Military,Homemade, and Green Explosives in Pure and Saline Water using COSMO‐RS

The conductor‐like screening model for real solvents (COSMO‐RS) has previously been shown to give accurate aqueous solubilities for a range of organic compounds using only quantum chemical simulation data. Application of this method for solid organic explosives, however, faces two difficulties; it requires correction for the free energy of fusion (a generally unknown quantity for these compounds) and it shows considerable error for common explosive classes such as nitramines. Herein we introduce a correction factor for COSMO‐RS that is applicable to a wide range of explosives, and requires no data beyond a quantum chemistry calculation. This modification allows COSMO‐RS to be used as a predictive tool for new proposed explosives or for systems lacking experimental data. We use this method to predict the temperature‐dependent solubility of solid explosives in pure and saline water to an average accuracy of approximately 0.25 log units at ambient temperature. Setschenow (salting‐out) coefficients predicted by this method show considerable improvement over previous COSMO‐RS results, but are still slightly overestimated compared to the limited experimental data available. We apply this method to a range of military, homemade, and “green” explosives that lack experimental seawater solubility data, an important property for environmental fate and transport modeling.     

Effect of self-association on liquid—liquid equilibria. Correlation of mutual solubility for methanol—saturated hydrocarbon systems

The continuous linear association model of the Kretschmer—Wiebe type is used to examine the effects of self-association on liquid-liquid equilibria. The results of the calculation show that the self-association enhances the phase separation and decreases the mole fraction of the self-associating component in a binary mixture at the critical solution point. The application of the theory to the binary systems of methanol—saturated hydrocarbons has yielded good correlations for both the critical solution points and the mutual solubilities at temperatures below the critical. The values of the association constant and enthalpy obtained for methanol are 1030 at 25°C and ?3·5 kcal/mol, respectively. The temperature dependence of the physical interaction parameter for each hydrocarbon is represented by a reduced form. The applicabilities of the theory to both vapour—liquid and liquid—liquid equilibria are better than those of NRTL equation for the systems of methanol—saturated hydrocarbons.     

Thermodynamic Modeling of Imidazolium-Based Ionic Liquids with the [PF6]− Anion for Separation Purposes

There is an increased interest in developing accurate tools to relate the physicochemical properties of ionic liquids (ILs) to their microscopic structure as this information is needed to speed up the design of new ionic liquids for chemical and industrial processes. Molecular models can be used for this purpose. We explore here the extended capabilities of a model previously developed in the context of soft-SAFT, by Andreu and Vega in 2007 to reproduce the thermodynamic behavior of imidazolium hexafluorophosphate-based ([C_nmim][PF₆]) ionic liquids. The molecular parameters optimized in the previous work have been used here in a transferable manner; some new members of the [C_nmim][PF₆] family have also been added, as new recent experimental data has been published. The interfacial tensions have been calculated using a Density Gradient Approach and the results have been compared with available experimental data. The solubility of carbon monoxide and hydrogen in those ILs has been studied in the range of temperatures and pressures of application for separation processes. Binary mixtures with other imidazolium ionic liquids with different anions have been calculated, in a predictive manner. Finally, calculations of mixtures of ionic liquids with water also show very good agreement with experimental data. This work highlights the importance of using a simple but robust thermodynamic model, including the right level of interactions, to accurately describe the properties of these highly non-ideal systems.     

Calculation of the solubilities of gases in paraffin hydrocarbons

A semiempirical equation is proposed to calculate the solubilities of gas systems containing H₂, CO, CO₂, N₂, Ar, CH₄, C₂H₆, and C₃H₈ in normal paraffin hydrocarbons from C₅ to C₂₀ and higher over wide temperature and pressure ranges. The applicability of the equation proposed is evaluated.