Prediction of Partition Coefficients of Organic Compounds in Ionic Liquids Using a Temperature-Dependent Linear Solvation Energy Relationship with Parameters Calculated through a Group Contribution Method

This article discusses the prediction of partition coefficients of organic compounds in ionic liquids

Addition of the Sulfur Dioxide Group (SO₂), the Oxygen Group (O₂), and the Nitric Oxide Group (NO) to the <i>E</i>‑PPR78 Model

The <i>E</i>-PPR78 model is a predictive version of the widely used Peng–Robinson equation of state in which the binary interaction parameters are estimated by a group-contribution method. With the 24 groups available before the writing of this paper, such a model could be used to predict fluid phase equilibrium of systems containing hydrocarbons, permanent gases (CO₂, N₂, H₂S, H₂, CO, He, and Ar), mercaptans, alkenes, and water. During the process of the Carbon dioxide Capture and Storage (CCS), it is often necessary to know thermodynamic properties of mixtures containing carbon dioxide, water, hydrocarbons, and trace gases, such as nitrogen, argon, hydrogen, carbon monoxide, sulfur dioxide, oxygen, or nitric oxide. Basically, except sulfur dioxide, oxygen, and nitric oxide, most components encountered in systems regarding CCS processes could be modeled with the <i>E</i>-PPR78 model. So in order to predict the phase behavior and estimate energetic properties (e.g., enthalpy or heat capacity changes on mixing) of such systems, the applicability range of the <i>E</i>-PPR78 model is extended through the addition of three new groups: “SO₂,” “O₂,” and “NO.

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Prediction of Thermodynamic Properties of Alkyne-Containing Mixtures with the <i>E</i>‑PPR78 Model

The thermodynamics of alkyne-containing mixtures is fundamental to the petroleum and chemical industries. Such mixtures are made complex both by the quantity and the variety of the species present thus justifying the need for a predictive model capable of guesstimating energetic and phase-equilibrium mixture properties. In this respect, the <i>E</i>-PPR78 (<i>enhanced</i>-predictive 1978, Peng–Robinson equation of state) model appears as a suitable candidate since it combines the well-established Peng–Robinson equation of state and an original group-contribution method making it possible to estimate the temperature-dependent binary interaction parameters, <i>k</i>_<i>ij</i>(<i>T</i>), involved in the van der Waals one-fluid mixing rules. With the 37 groups defined in previous works, such a model could be used to predict fluid-phase equilibria and energetic properties of systems containing hydrocarbons, permanent gases (CO₂, N₂, H₂S, H₂, CO, He, Ar, SO₂, O₂, NO, COS, NH₃, NO₂/N₂O₄, N₂O), mercaptans, fluoro-compounds, and water. In this study, three alkyne groups (“HCCH”, “CCH”, and “CC”) are added in order to accurately predict phase-equilibrium properties and enthalpies of mixing of alkyne-containing multicomponent mixtures. The determination of the group-interaction parameters (involved in the <i>k</i>_<i>ij</i>(<i>T</i>) expression) between two groups including at least one alkyne group is performed with the help of a comprehensive database of binary-system phase-equilibrium and mixing-enthalpy data

Enthalpy and Heat Capacity Changes on Mixing: Fundamental Aspects and Prediction by Means of the PPR78 Cubic Equation of State

The PPR78 model is a predictive cubic equation of state relying on the group-contribution concept. Our previous studies have highlightened its capacity to predict the phase behavior of mixtures containing a large variety of compounds: alkanes, alkenes, aromatic compounds, permanent gases, sulfur compounds, etc. In this paper, it is attempted for the first time to answer the question “<i>can the PPR78 model be safely used in energy-rate balances?</i>”. To do so, the largest possible number of enthalpy of mixing data and isobaric heat capacity of mixing data were collected in the open literature and predicted using the PPR78 model. It is shown that although certainly perfectible, this model generally provides from acceptable to accurate estimations of these properties depending on the nature of the mixtures and the conditions of temperature and pressure as well. Furthermore, this paper proposes some general reflections both on conceptual and practical issues: Is it always possible to claim that the excess enthalpy and the enthalpy of mixing are two strictly equivalent quantities? Does an equation of state have the same capacity to reproduce enthalpy of mixing data in one-phase and in two-phase regions? Which criterion should be used for evaluating the accuracy of an equation of state in terms of energy-rate balances

Predicting Binary-Interaction Parameters of Cubic Equations of State for Petroleum Fluids Containing Pseudo-components

Cubic equations of state (EoS) are widely used for the prediction of thermodynamic properties of petroleum fluids containing both well-defined and <i>pseudo</i>-components. Such EoS require as input parameters the critical temperature (<i>T</i>_c), the critical pressure (<i>P</i>_c), and the acentric factor (ω) of each compound. For well-defined components, such properties are known from experiments and easily obtained. For pseudo-components they are routinely estimated using one of the numerous characterization methods (CM) available in the open literature. A CM is nothing more than a set of correlations which makes it possible to estimate <i>T</i>_c, <i>P</i>_c, and ω of a pseudo-component (PC) from the knowledge of its normal boiling point (NBP), molecular weight (MW), or specific gravity (SG). Regarding the binary-interaction parameters (BIP) <i>k</i>_<i>ij</i> (where <i>i</i> and/or <i>j</i> are/is a pseudo-component(s)) which appear in classical mixing rules, they are either set to zero or estimated by a specific correlation. Most of the proposed correlations are however purely empirical and usually only make possible the estimation of the <i>k</i>_<i>ij</i> between light components (H₂S, CO₂, N₂, C₁, C₂, and C₃) and a pseudo-component. The full <i>k</i>_<i>ij</i> matrix is thus beyond reach and the BIP are usually temperature-independent. In this work, the PPR78 model is used to predict BIP suitable for the Peng–Robinson EoS whereas the PR2SRK model is used to predict BIP suitable for any other cubic EoS. Since these models can be seen as group-contribution methods (GCM) to estimate the <i>k</i>_<i>ij</i>, one needs to access the chemical structure of each PC. The chemical structure of PC is however too complex to be precisely determined. For this reason, it was assumed that each PC was made of only three groups: C_PAR, C_NAP, and C_ARO in order to take into account their paraffinic, naphthenic, and aromatic characters, respectively. The occurrences (<b>N</b>) of the three aforementioned groups are determined from the knowledge of <i>T</i>_c,CM, <i>P</i>_c,CM, and ω_CM (issuing from a CM). To reach this goal, GC methods aimed at estimating <i>T</i>_c, <i>P</i>_c, and ω of hydrocarbons were developed. Such methods have the ability to consider only three elementary groups: C_PAR, C_NAP, and C_ARO. In the end, the three known properties (<i>T</i>_c,CM, <i>P</i>_c,CM, and ω_CM) can be expressed as functions of <i>N</i>_PAR, <i>N</i>_NAP, and <i>N</i>_ARO (the occurrences of the groups) and we thus only need to solve a system of three equations with three unknowns. To check its validity, the present approach is applied to the prediction of the phase behavior of real petroleum fluids containing pseudo-components. The test results show the pertinence of the proposed method to predict the <i>k</i>_<i>ij</i> when <i>i</i> and/or <i>j</i> is a pseudo-component

Activity Coefficients at Infinite Dilution of Organic Compounds in Four New Imidazolium-Based Ionic Liquids

Article on activity coefficients at infinite dilution of organic compounds in four new imidazolium-based ionic liquids