Densities of urea–ammonia–water–carbon dioxide solutions in chemical equilibrium at and above urea synthesis conditions

Broers, Jan N.; Lemkowitz, Saul; Berg, Pieter J. Den Van

doi:10.1002/jctb.5020251009

Cited by 6 publications

(3 citation statements)

References 10 publications

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“…Kassenbrood and Lemkowitz and coworkers − have presented a detailed investigation of the phase behavior of the NH 3 + CO 2 mixture, and some limited experimental data for the vapor−liquid equilibria of the mixture is reported. From this body of work, it is clear that the NH 3 + CO 2 mixture exhibits positive azeotropy.…”

Section: Resultsmentioning

confidence: 99%

Modeling the Fluid Phase Behavior of Carbon Dioxide in Aqueous Solutions of Monoethanolamine Using Transferable Parameters with the SAFT-VR Approach

Dowell

Llovell

Adjiman

et al. 2009

Ind. Eng. Chem. Res.

133

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The current method of choice for large-scale carbon dioxide (CO2) capture is amine-based chemisorption, typically in packed columns, with the benchmark solvent being aqueous solutions of a primary alkanolamine: monoethanolamine (MEA). In this contribution, we use the statistical associating fluid theory for potentials of variable range (SAFT-VR) to describe the fluid phase behavior of MEA + H2O + CO2 mixtures. The physical chemistry of CO2 in aqueous solutions of amines is highly complex owing to the chemical equilibria between the various species that are formed in solution at ambient conditions. We explicitly consider the multifunctional nature of MEA and, in so doing, are able to represent accurately the thermodynamic properties and phase equilibria of this highly nonideal mixture over a wide range of temperatures, pressures, and compositions. MEA is modeled as an associating chain molecule formed from homonuclear spherical segments with six distinct association sites incorporated to mediate the asymmetric hydrogen bonding interactions exhibited by this molecule. The models for H2O and CO2 are taken from previous work. In order to describe the chemisorption, which is the key to the CO2 capture process, two additional effective sites are incorporated on the otherwise nonassociating CO2 molecule to describe the chemical interaction between the MEA and CO2, so that the correct maximal stoichiometry of two amine molecules per CO2 molecule is retained. The vapor−liquid phase equilibria of the various binary mixtures and of the MEA + H2O + CO2 ternary mixture are accurately described with our approach, including the degree of absorption of CO2 in the solvent for wide ranges of temperature and pressure. This suggests that the underlying complexity of the chemical equilibria associated with this system are correctly captured by the model and provides great promise for the modeling of the overall process of CO2 capture.

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Section: Resultsmentioning

confidence: 99%

Modeling the Fluid Phase Behavior of Carbon Dioxide in Aqueous Solutions of Monoethanolamine Using Transferable Parameters with the SAFT-VR Approach

Dowell

Llovell

Adjiman

et al. 2009

Ind. Eng. Chem. Res.

133

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“…To model the ternary mixtures of interest, the intermolecular parameters characterizing the CO 2 −NH 3 and CO 2 − n -alkyl-1-amine binary interactions need to be determined. Unfortunately, there are very limited experimental data for these systems, with the exception of a few data points along the azeotropic line of the CO 2 + NH 3 mixture. − Instead, a good set of data for the ternary mixture NH 3 + H 2 O + CO 2 is available; we use these to estimate the binary unlike interactions needed.…”

Section: Ternary Mixturesmentioning

confidence: 99%

“…Unfortunately, there are very limited experimental data for these systems, with the exception of a few data points along the azeotropic line of the CO 2 þ NH 3 mixture. [110][111][112][113][114][115][116][117] Instead, a good set of data for the ternary mixture NH 3 þ H 2 O þ CO 2 is available; 56 we use these to estimate the binary unlike interactions needed.…”

Section: Ternary Mixturesmentioning

confidence: 99%

Transferable SAFT-VR Models for the Calculation of the Fluid Phase Equilibria in Reactive Mixtures of Carbon Dioxide, Water, and n-Alkylamines in the Context of Carbon Capture

et al. 2011

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The amine functional groups are fundamental building blocks of many molecules that are central to life, such as the amino acids, and to industrial processes, such as the alkanolamines, which are used extensively for gas absorption. The modeling of amines and of mixtures of amines with water (H(2)O) and carbon dioxide (CO(2)) is thus relevant to a number of applications. In this contribution, we use the statistical associating fluid theory for potentials of variable range (SAFT-VR) to describe the fluid phase behavior of ammonia + H(2)O + CO(2) and n-alkyl-1-amine + H(2)O + CO(2) mixtures. Models are developed for ammonia (NH(3)) and n-alkyl-1-amines up to n-hexyl-1-amine (CH(3)NH(2) to C(6)H(13)NH(2)). The amines are modeled as homonuclear chain molecules formed from spherical segments with additional association sites incorporated to mediate the effect of hydrogen-bonding interactions. The SAFT-VR approach provides a representation of the pure component fluid phase equilibria, on average, to within 1.48% of the experimental data in relative terms for the saturated liquid densities and vapor pressures. A simple empirical correlation is derived for the SAFT-VR parameters of the n -alkylamine series as a function of molecular weight. Aqueous mixtures of the amines are modeled using a model of water taken from previous work. The models developed for the mixtures are of high fidelity and can be used to calculate the binary fluid phase equilibrium of these systems to within 2.28% in relative terms for the temperature or pressure and 0.027 in absolute terms for the mole fraction. Regions of both vapor-liquid and liquid-liquid equilibria are considered. We also consider the reactive mixtures of amines and CO(2) in aqueous solution. To model the reaction of CO(2) with the amine, an additional site is included on the otherwise nonassociating CO(2) model. The unlike interaction parameters for the NH(3) + H(2)O + CO(2) ternary mixture are obtained by comparison to the experimental data available for this system. The resulting model is found to correlate and predict the liquid-phase loading (moles of CO(2) per mole of amine) to within 0.091 of experimental data in absolute terms. The parameters describing the NH(3)-CO(2) interaction are then transferred to other n-alkyl-1-amines, and sample predictions of the fluid phase equilibria for the n-propyl-1-amine + H(2)O + CO(2), n-butyl-1-amine + H(2)O + CO(2), and n-hexyl-1-amine + H(2)O + CO(2) mixtures are presented. The latter mixture is found to exhibit regions of liquid-liquid immiscibility.

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A phase model for the gas–liquid equilibria in the ammonia–carbon dioxide–water–urea system in chemical equilibrium at urea synthesis conditions. II. Experimental verification

Lemkowitz¹,

Vet²,

Berg³

1977

J. Biochem. Toxicol.

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Densities of urea–ammonia–water–carbon dioxide solutions in chemical equilibrium at and above urea synthesis conditions

Cited by 6 publications

References 10 publications

Modeling the Fluid Phase Behavior of Carbon Dioxide in Aqueous Solutions of Monoethanolamine Using Transferable Parameters with the SAFT-VR Approach

Modeling the Fluid Phase Behavior of Carbon Dioxide in Aqueous Solutions of Monoethanolamine Using Transferable Parameters with the SAFT-VR Approach

Transferable SAFT-VR Models for the Calculation of the Fluid Phase Equilibria in Reactive Mixtures of Carbon Dioxide, Water, and n-Alkylamines in the Context of Carbon Capture

A phase model for the gas–liquid equilibria in the ammonia–carbon dioxide–water–urea system in chemical equilibrium at urea synthesis conditions. II. Experimental verification

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