8 research outputs found
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 (SO<sub>2</sub>), the Oxygen Group (O<sub>2</sub>), 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 (CO<sub>2</sub>, N<sub>2</sub>, H<sub>2</sub>S, H<sub>2</sub>, 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: “SO<sub>2</sub>,”
“O<sub>2</sub>,” 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><sub><i>ij</i></sub>(<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 (CO<sub>2</sub>,
N<sub>2</sub>, H<sub>2</sub>S, H<sub>2</sub>, CO, He, Ar, SO<sub>2</sub>, O<sub>2</sub>, NO, COS, NH<sub>3</sub>, NO<sub>2</sub>/N<sub>2</sub>O<sub>4</sub>, N<sub>2</sub>O), mercaptans, fluoro-compounds, and
water. In this study, three alkyne groups (“HCCH”,
“CCH”, and “CC”)
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><sub><i>ij</i></sub>(<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><sub>c</sub>), the critical pressure (<i>P</i><sub>c</sub>), 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><sub>c</sub>, <i>P</i><sub>c</sub>, 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><sub><i>ij</i></sub> (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><sub><i>ij</i></sub> between light
components (H<sub>2</sub>S, CO<sub>2</sub>, N<sub>2</sub>, C<sub>1</sub>, C<sub>2</sub>, and C<sub>3</sub>) and a pseudo-component. The full <i>k</i><sub><i>ij</i></sub> 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><sub><i>ij</i></sub>, 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<sub>PAR</sub>, C<sub>NAP</sub>, and C<sub>ARO</sub> 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><sub>c,CM</sub>, <i>P</i><sub>c,CM</sub>, and ω<sub>CM</sub> (issuing from a CM). To reach this goal, GC methods aimed at estimating <i>T</i><sub>c</sub>, <i>P</i><sub>c</sub>, and ω
of hydrocarbons were developed. Such methods have the ability to consider
only three elementary groups: C<sub>PAR</sub>, C<sub>NAP</sub>, and
C<sub>ARO</sub>. In the end, the three known properties (<i>T</i><sub>c,CM</sub>, <i>P</i><sub>c,CM</sub>, and ω<sub>CM</sub>) can be expressed as functions of <i>N</i><sub>PAR</sub>, <i>N</i><sub>NAP</sub>, and <i>N</i><sub>ARO</sub> (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><sub><i>ij</i></sub> 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