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Tetraisothiocyanatocobaltate-based ionic liquids (ILs) have shown interesting thermophysical properties, mainly surprisingly low melting points and moderate viscosity. In addition, they have been tested to separate aromatics from aliphatics because of the high molar relation between cyano groups per molecule, with highlighted results. In this work, high-pressure density data (ρpT) were measured for bis(1-alkyl-3-methylimidazolium) tetraisothiocyanatocobaltate ILs ([CnC1im]2[Co(NCS)4]) (n = 1, 2) over wide ranges of temperature (283–363 K) and pressure (0.1–95 MPa). The new ρpT data and derivative properties, namely, the isothermal compressibility and isobaric expansivity, were successfully modeled with perturbed-chain statistical association fluid theory (PC-SAFT) and using the so-called volume shift, allowing us to propose a new molecular model and parameters for these solvents. The proposed model for tetraisothiocyanatocobaltate-based ILs is shown to be robust enough to model the phase equilibria of thi...

Extractive distillation using tricyanomethanide-based ionic liquids (ILs) has been shown to be a promising and feasible process for effectively separate aromatics from pyrolysis gasolines. The high performance of these mass agents has been reported by evaluating simple synthetic n-heptane/toluene binary mixtures, on a wide temperature and solvent to feed (S/F) ratio ranges. However, industrial streams are much more complex with the presence of other aromatic and aliphatic compounds, like benzene, xylenes, and shorter and longer linear alkanes, creating further difficulties to the separation and thus must be studied. This work covers the phase equilibrium characterization of {n-hexane + benzene + IL} and {n-octane + p-xylene + IL} ternary systems with two tricyanomethanide-based ILs, namely 1-ethyl-3-methylimidazolium tricyanomethanide ([C2C1im][TCM]) and 1-butyl-4-methylpyridinium tricyanomethanide ([4-C4C1py][TCM]), addressing also the phase characterization of the corresponding {hydrocarbon + IL} binary...

A modified cubic-plus-association equation of state (CPA EoS) has been presented in recent works that enforces the representation of the pure component critical point, is based on an extended Mathi...

Supercritical carbon dioxide (scCO2) is widely used in separation processes applied to the food, chemistry, pharmaceutical and material industries. The knowledge of the solubility of solid solutes in scCO2, with or without cosolvents, is essential for the design and optimization of extraction, fractionation and purification processes. This work evaluates the accuracy of Cubic Plus Association equation of state (CPA-EoS) to predict the solubility of solutes in ternary and/or quaternary systems from the binary interaction parameters. The solubility of 12 solid solutes in scCO2 in presence of different organic cosolvents was investigated, totalizing 19 systems at pressures between 8 and 40 MPa, temperatures ranging from 308 K to 353 K and concentrations of cosolvent varying from 0.73 to 10 mol%. The overall average logarithmic deviation (ALD) between experimental and calculated data with CPA-EoS was 0.47, which is better than that obtained with PR + COSMOSAC previously reported in the literature. Furthermore, the effects of temperature, pressure and of cosolvent type and concentration on the solubility were well estimated with the CPA-EoS.

The energy industry has registered a considerable growth of petroleum production from reservoirs located in deep and ultra-deepwater, mainly in Brazil. The Brazilian Pre-Salt fields, specifically, have shown high carbon dioxide content which favors the precipitation of organic particles such as asphaltenes. This scenario has turned flow assurance into a major technical and economic challenge for the exploitation of those fields. In this work a variable-volume cell equipped with a near-infrared probe was used to study the onset of asphaltene precipitation induced by carbon dioxide, evaluating the effects of pressure, temperature, asphaltene concentration, and system composition. Furthermore, the Cubic Plus Association (CPA) was applied to model the asphaltene precipitation. The results show that temperature and the oil model system composition were the parameters that most influenced the asphaltene stability, and that the CPA adequately described the asphaltene precipitation.

One of the major flow assurance problems afflicting the oil industry is the asphaltene precipitation during the production, transportation and storage of oil. The precipitation of these heavy compounds is responsible for changes in crude oil properties, increases in oil viscosity, and formation of deposits that reduce oil production and disable equipment leading to significant operational costs. In Algeria, the deposition of asphaltene in res- ervoirs and pipelines is a severe problem. During production the depressurization of reservoir fluid and the variations of thermodynamic conditions create the need to frequently pig the lines and, in some cases, to inject solvents and dispersants to maintain the production. The understanding of the asphaltene behavior and the prediction of its deposition in flow conditions is crucial to implement appropriate strategies for the prevention or remediation, especially in the wellbore region. In this work we used the CPA EoS to describe the asphaltene phase envelope and predict the PT regions of stability for five Algerian live oils. The model provides a very good description of the experimental behavior of live oils without and with gas injection. The sensitivity to SARA analysis data and its effect on the asphaltene phase boundaries were also analyzed. BC Advanced Technologies Limited, Sonatrach published

The description of the critical data of a mixture is of importance for various applications such as supercritical processes, reactions close to the critical temperature, or safety design in piping. In a previous work, we have shown that a modified cubic-plus-association (CPA) equation of state is able to provide an accurate representation of critical points for mixtures of associating compounds or for mixtures of associating compounds with hydrocarbons. In the present work, this study is extended to mixtures containing associating and solvating compounds. Binary and ternary mixtures of alkanols, diethylamine or water with ketones, aromatics, ethers, tetrahydrofuran, or diethyl carbonate are studied. Binary interaction parameters are fitted from subcritical LLE or VLE data. For the binary mixtures, when analyzing the curves of Tc and Pc versus composition, the average deviation on Pc is below 2.4%, while the average ΔTc is below 2.5 K. Three ternary mixtures are also investigated. For these, deviations are...

This work evaluated the solubility of caffeic acid (CA) in mixtures of supercritical carbon dioxide (scCO2) and ethanol at different temperatures (313, 323 and 333 K), pressures (20, 30 and 40 MPa) and concentrations of ethanol (2.2, 5.4 and 10.2 mol%). The Soave-Redlich-Kwong and Cubic Plus Association (CPA) equations of state were used to correlate the binary mixture data and to predict the ternary system data. CA solubility in ethanol is approximately 106 times higher than its solubility in pure scCO2. By using 10.2 mol% ethanol in scCO2, CA solubility increased 30,000 times at 313 K and 20 MPa. Both models provided reasonable descriptions of the experimental data for the binary systems. However, CPA-EoS can better describe the strong interactions between acid molecules and ethanol, and can predict that the addition of small amounts of ethanol to scCO2 provides a large increase in CA solubility.

In a phase envelope, an adequate description of the critical point is of high importance. It identifies the conditions where the bubble and dew curves meet, and where the nature of the single phase region outside the phase envelope changes. The knowledge of the mixture critical point is relevant to preventing production and transport problems, as well as to optimizing near-critical and supercritical processes. A modified cubic plus association (CPA) model was recently shown to accurately describe the vapor–liquid equilibrium (VLE) critical temperatures and pressures of pure compounds. The model is usually fitted to pure component data between 0.45Tr and 0.85Tr, while forcing the correct description of both Tc and Pc. Here, the performance of the model is evaluated for mixtures. Interaction parameters are regressed from VLE/liquid–liquid equilibrium (LLE) data at lower temperatures. Accurate results, for binary and ternary mixtures, were obtained. These results concern mainly mixtures containing, water, al...

One of the major challenges of an equation of state lies in the description of water and aqueous systems. Its abundance and unique properties turn water into one of the most important molecules in the industry. However, because of these peculiar characteristics, its modeling is far more complex than for any other common solvent. In this work, a modified cubic plus association (CPA) model, which includes the correct description of the pure component critical temperature and critical pressure, is expanded to water and its systems. A brief analysis of the predicted water purity properties is conducted, comparing those to a previous version of the model. Results for a group of binary systems, including liquid–liquid equilibria with alkanes and alcohols, highlighting their minima in aqueous solubility, and gas solubility in water/water solubility in gas, are also presented. Finally, ternary and multicomponent systems of water + hydrocarbons and water + polar compound + hydrocarbons are also modeled and discussed.

The knowledge of critical properties is fundamental in engineering process calculations for the estimation of thermodynamic properties and phase equilibria. A literature survey shows a large number of methods for predicting critical properties of different classes of compounds, but no previous study is available to evaluate their suitability for terpenes and terpenoids. In this work, the critical properties of terpenes and terpenoids were first estimated using the group-contribution methods of Joback, Constantinou and Gani, and Wilson and Jasperson. These were then used to calculate densities and vapor pressure through the equations of state Peng-Robinson (PR) and Soave-Redlich-Kwong (SRK) and then compared with the experimental values. On other hand, density and vapor pressure experimental data were used to estimate the critical properties directly by the same equations of state (EoSs), allowing a comparison between the two estimation procedures. For this purpose densities for 17 pure terpenes and terpenoids were here measured at atmospheric pressure in the temperature range (278.15 to 368.15) K. Using the first approach, the best combination is the Joback's method with the Peng-Robinson EoS, despite the high relative deviations found for vapor pressure calculations and difficulties to predict density at low temperatures. Following the second approach, the set of critical properties and acentric factors estimated are able to adequately correlate the experimental data. Both equatio ns show a similar capability to correlate the data with SRK EoS presenting a global %ARD of 3.16 and 0.62 for vapor pressure and density, respectively; while the PR EoS presented 3.61 and 0.66, for the same properties, both giving critical properties estimates also closer to those calculated by the Joback method, which is the recommended group-contribution method for this type of compounds. This work was developed in the scope of the projects POCI-01- 0145-FEDER-007679-CICECO-Aveiro Institute of Materials (ref. FCT UID/CTM/50011/2013), POCI-01-0145-FEDER- 006984−Associate Laboratory LSRE-LCM both funded by European Regional Development Fund (ERDF) through COMPETE2020, Programa Operacional Competitividade e Internacionalização (POCI), and by national funds through FCT (Fundação para a Ciência e a Tecnologia). This work is also a result of project “AIProcMat@N2020 (Advanced Industrial Processes and Materials for a Sustainable Northern Region of Portugal 2020)”, with the reference NORTE-01- 0145-FEDER-000006, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through ERDF. M.A.R.M. acknowledges FCT for her Ph.D. grant (SFRH/BD/87084/ 2012) and COST for the STSM Grant from COST action CM1206. P. J. Carvalho also acknowledges FCT for a contract under the Investigador FCT 2015, Contract No. IF/00758/ 2015. A.M.P. acknowledges Infochem-KBC for his Ph.D. grant. The software Multiflash from Infochem-KBC was applied in some of the calculations info:eu-repo/semantics/publishedVersion

To create a predictive method for an associative equation of state, the parameters of a specific associative group should be transferrable among molecules. The hydroxyl group, one of the most common associative groups, is a good starting point for this development. On the basis of a previous study where a modified version of the Cubic Plus Association (CPA) EoS was shown to present accurate results for alkanols with almost constant association parameters, this work addresses branched, secondary alcohols, 1,ω-alkanediols, and glycerol to evaluate how CPA can handle steric hindrances and the presence of more than one hydroxyl group. The pure component properties studied here are vapor pressure, saturated liquid density, saturated liquid isobaric heat capacity, and heat of vaporization. Some VLE, LLE, and GLE of binary systems are also analyzed, showing how the modifications affect the description of binary/multicomponent systems. Some systems containing petroleum fluids are also analyzed.

Although the CPA EoS was initially developed 20 years ago to meet industrial solicitations, namely the need to describe mixtures of hydrocarbons and water, including the formation and dissociation of hydrates, it has only recently received a widespread use in mid-stream and downstream oil and gas processing, or in the petrochemical and chemical industries. One of the reasons for such limited use of the model in the industry is the necessity to parameterize every associating component from saturation data. This involves access to pure component databases and some advanced knowledge in thermodynamics and numerical methods, which are often behind the scope of process design engineers. This work revisits the CPA model, evaluating its strengths and weaknesses and attempting at identifying some opportunities for improvement. Using n-alkanols from C1 to C10 and their mixtures with other n-alkanols and n-alkanes, it investigates the description of the pure component critical points, saturated liquid densities as a function of temperature and some second-order derivative properties. It also explores new methodologies to regress the CPA parameters in a more systematic way, making it easier to generate parameters with less intervention from the user.

Despite the large spectrum of applications being reported for DESs over the last decade, their thermodynamic characterization is often neglected, hindering a better understanding of their nature, and the development of accurate and robust thermodynamic models to describe them, essential for the conceptual and design stages of new industrial processes. This work aims at decreasing such a gap in literature by reporting new experimental density and viscosity data in wide temperature and pressure ranges for the three archetypal DESs of cholinium chloride, as hydrogen bond acceptor, combined with either ethylene glycol, glycerol, or urea, as hydrogen bond donor. The experimental data measured in this work were then correlated using the Perturbed Chain - Statistical Associating Fluid Theory equation of state coupled with the Free Volume Theory to assess the performance of existing coarse-grained models when applied to the description of DESs. The modelling results obtained highlight the limitation of the existing models, since a correct prediction of DES density could not be achieved, reinforcing the need for viable alternative approaches for the development of coarse-grained models that are appropriate for the thermodynamic modelling of DESs.

Tricyanomethanide-based ionic liquids (ILs) are, probably, the most interesting ILs for separation purposes considering their low viscosity and high thermal stability, but mainly due to their enhanced performance in a wide number of applications. However, the scarce high pressure density data (ρpT) limits the development of robust models for process simulation implementation and consequently process development. In this work, high pressure density data of 1-ethyl-3-methylimidazolium tricyanomethanide ([C2C1im][TCM]) and 1-butyl-4-methylpyridinium tricyanomethanide ([4-C4C1py][TCM]) are reported in a wide range of temperature (283–363) K and pressure (0.1–95) MPa. The new ρpT data and its derivative properties, namely isothermal compressibility (kT) and isobaric thermal expansivity (αP), of the studied ILs and that reported for the 1-butyl-3-methylimidazolium tricyanomethanide ([C4C1im][TCM]), were successfully modelled using the Perturbed-Chain Statistical Association Fluid Theory (PC-SAFT). New molecular parameters for the tricyanomethanide-based ILs are here proposed allowing a good description of the studied properties while assessing the well-known non-volatile character of the ILs.

The aromatic/aliphatic separation using ionic liquids (ILs) has been proposed as an enhanced technology when compared to conventional liquid-liquid extraction and extractive distillation processes. Some ILs show extractive properties (distribution ratios and selectivities) greater than those of conventional solvents, like sulfolane and N- methylpyrrolidone, positioning these solvents to address challenging separations. Methylcycloalkanes and benzene are close-boiling mixtures in the petrochemical industry, presented at the hydrogenated pyrolysis naphtha where benzene is at a high concentration (ca. 70 wt%). Aiming to tackle this separation, cyano-based ILs were tested as mass agents in the benzene separation from methylcycloalkanes. A complete phase equilibria characterization with the most promising ILs, [C2C1im][DCA] and [C2C1im][SCN], were done, using a recently developed experimental-modelling strategy. Isothermal vapour-liquid equilibria for binary, ternary and qua- ternary systems was measured by Headspace Gas-Chromatography (HS-GC) and modelled using the Cubic Plus Association (CPA) Equation of State (EoS). The presence of the ILs improved the methylcycloalkane/benzene relative volatilities by one order of magnitude, whereas homogeneous and heterogeneous regions were de- termined by HS-GC, leading to a consistent model. Ministerio de Economía y Competitividad (MINECO) of Spain published