Fluid Phase Equilibria

Journal: Fluid Phase Equilibria

Abbreviation

Fluid phase equilib.

Publisher

Elsevier

ISSN

0378-3812

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Publications1 - 10 of 22

Quaternary isothermal vapor-liquid equilibrium of the model biofuel 2-butanone + n-heptane + tetrahydrofuran + cyclohexane using Raman spectroscopic characterization
Liebergesell, Bastian; Brands, Thorsten; Koß, Hans-Jürgen; et al. (2018)
Fluid Phase Equilibria
Vapor-liquid equilibrium data of fuel mixtures are of major importance for both fuel production as well as combustion. However, the measurement of vapor-liquid equilibrium data usually requires significant experimental effort. The experimental effort is particularly high if multicomponent mixtures are of interest, as experimental effort rises strongly with a rising number of components. In this work, we efficiently characterize the vapor-liquid equilibrium of a quaternary model biofuel and its binary subsystems. For this purpose, we employ the recently developed milliliter-scale Raman Spectroscopic Phase Equilibrium Characterization (RAMSPEQU)-setup. Vapor pressures are collected at T = 283–333 K, and isothermal pTx-data for mixtures at T = 303.2 K resulting in a pressure range of p = 2.8–81.9 kPa. The PCP-SAFT equation of state is used for thermodynamic modeling. Our binary data agrees well with experimental data from literature. The quaternary phase behavior is predicted with very good accuracy using PCP-SAFT with parameters adjusted to pure substance and binary mixture data only. The milliliter-scale setup allows us to characterize the phase equilibria with just 22 ml (binary) and less than 105 ml (quaternary) of the respective mixtures. The agreement of predicted and experimental quaternary phase equilibrium data indicate the reliability of the employed method for multicomponent vapor-liquid equilibrium measurements. ©2018 Elsevier B.V. All rights reserved.
Concentration-dependent diffusion coefficients from a single experiment using model-based Raman spectroscopy
Bardow, André; Göke, Volker; Koss, Hans-Jürgen; et al. (2005)
Fluid Phase Equilibria ~ PPEPPD 2004 Proceedings
Hexadecane/air partitioning coefficients of multifunctional compounds
Bronner, Guido; Fenner, Kathrin; Goss, Kai-Uwe (2010)
Fluid Phase Equilibria
Thermodynamic properties of aqueous KCl solution at temperatures to 600 K, pressures to 150 MPa, and concentrations to saturation
Zezin, Denis; Driesner, Thomas (2017)
Fluid Phase Equilibria
Optimal experimental design of physical property measurements for optimal chemical process simulations
Fleitmann, Lorenz; Pyschik, Jan; Wolff, Ludger; et al. (2022)
Fluid Phase Equilibria
Chemical process simulations depend on physical properties, which are usually available through property models with parameters estimated from experiments. The required experimental effort can be reduced using the method of Optimal Experimental Design (OED). OED reduces the number of experiments by minimising the expected uncertainty of the estimated parameters. In chemical engineering, however, the main purpose of an experiment is usually not to determine property parameters with minimum uncertainty but to simulate processes accurately. Therefore, this paper presents the OED of physical property measurements resulting in the most accurate process simulations: c-optimal experimental design (c-OED). c-OED aims to minimise the uncertainty of the process simulation results, which is estimated by linear uncertainty propagation from uncertain property parameters through the process model. We use c-OED to design liquid-liquid equilibrium and diffusion experiments minimising thermodynamic and economic performance metrics of three solvent-based processes. In all three case studies, the c-optimal design substantially reduces the experimental effort for the same simulation accuracy compared to state-of-the-art OED that neglects the process. Our findings are confirmed by a Monte-Carlo simulation of the designed experiments. Furthermore, we assess the limits of c-OED for highly nonlinear process models. Thus, the work shows how c-OED can successfully reduce experimental effort required for accurate process simulations by tailoring experimental designs to the process model.
SPT-NRTL: A physics-guided machine learning model to predict thermodynamically consistent activity coefficients
Winter, Benedikt; Winter, Clemens; Esper, Timm; et al. (2023)
Fluid Phase Equilibria
The availability of property data is one of the major bottlenecks in the development of chemical processes and products, often requiring time-consuming and expensive experiments or limiting the chemical space to a small number of known molecules. This bottleneck has been the motivation behind the continuing development of predictive property models. For the property prediction of novel molecules, group contribution methods have been groundbreaking. In recent times, machine learning has joined the more established property prediction models. However, even with recent successes, the integration of physical constraints into machine learning models remains challenging. Physical constraints are vital to many thermodynamic properties, such as the Gibbs-Dunham relation, introducing an additional layer of complexity into the prediction. Here, we introduce SPT-NRTL, a natural language processing model to predict thermodynamically consistent activity coefficients and provide NRTL parameters for easy use in process simulations.SPT-NRTL can be classed as an advanced group contribution model that uses characters of the SMILES code as atom groups and then dynamically constructs higher-order groups. The results show that SPT-NRTL achieves higher accuracy than UNIFAC in the prediction of activity coefficients across all functional groups and is able to predict many vapor–liquid-equilibria with near experimental accuracy, as illustrated for multiple exemplary mixtures. To ease the application of SPT-NRTL, NRTL-parameters of 100 000 000 mixtures are calculated with SPT-NRTL and provided online.
Guide to efficient solution of PC-SAFT classical Density Functional Theory in various Coordinate Systems using fast Fourier and similar Transforms
Stierle, Rolf; Sauer, Elmar; Eller, Johannes; et al. (2020)
Fluid Phase Equilibria
Classical density functional theory (DFT) is a powerful tool for studying solvation or problems where resolution of interfacial domains or interfacial properties among phases (or thin films) is required. Many interesting problems necessitate multi-dimensional modeling, which calls for robust and efficient algorithmic implementations of the Helmholtz energy functionals. A possible approach for achieving efficient numerical solutions is using the convolution theorem of the Fourier transform. This study is meant to facilitate research and application of DFT methods, by providing a detailed guide on solving DFT problems in multi-dimensional domains. Methods for efficiently solving the convolution integrals in Fourier space are presented for Cartesian, cylindrical, and spherical coordinates. For cylindrical and spherical coordinate systems, rotational and spherical symmetry is exploited, respectively. To enable easy implementation, our approach is based on fast Fourier, fast Hankel, fast sine and cosine transforms on equidistant grids, all of which can be applied using off-the-shelf algorithms. Subtle details for implementing algorithms in cylindrical and spherical coordinate systems are emphasized. The work covers functionals based on weighted densities exemplarily. Functionals according to fundamental measure theory (FMT) as well as a Helmholtz energy functional based on the perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state are worked out in detail (and given as Supporting Information).
Model-free calibration of Raman measurements of reactive systems: Application to monoethanolamine/water/CO2
Beumers, Peter C.; Brands, Thorsten; Koß, Hans J.; et al. (2016)
Fluid Phase Equilibria
We present a method to calibrate Raman measurements of reactive systems without relying on thermodynamic models. Raman spectroscopy is able to detect multiple species even in reactive mixtures. Classical calibration methods require the knowledge of concentrations of all species as input. Typically, concentrations of intermediates cannot be prepared and fixed independently and are therefore calculated using thermodynamic models. The quality of the results thus depends on the accuracy of the thermodynamic model. In this paper, we present a method based only on stoichiometric balances and electroneutrality. By avoiding the use of thermodynamic models in the calibration step, the risk of overfitting spectroscopic data to a thermodynamic model is avoided. The presented method is demonstrated for the reactive system monoethanolamine, water, and CO2 and is validated by a thermodynamic model taken from the literature. While the model-free calibration is demonstrated for Raman spectroscopy in this work, the approach is generic should thus be applicable to most spectroscopic techniques.
A milliliter-scale setup for the efficient characterization of isothermal vapor-liquid equilibria using Raman spectroscopy
Liebergesell, Bastian; Flake, Carsten; Brands, Thorsten; et al. (2017)
Fluid Phase Equilibria
Experimental vapor-liquid equilibrium data are of major importance for the chemical industry. However, the measurement of vapor-liquid equilibrium data still requires significant experimental effort. Therefore, we present a novel setup and measurement procedure for the rapid determination of isothermal vapor-liquid equilibria using only milliliter samples. The compositions of both liquid and vapor phases are analyzed using Raman spectroscopy. The measurement setup is successfully validated by reproducing vapor pressures of four pure substances and binary vapor-liquid equilibrium data of methyl tert-butyl ether (MTBE) and 2,2,4-trimethylpentane (iso-octane) at T = 318.1 K as test system from literature. The vapor pressures of MTBE, ethanol, iso-octane and toluene agree with literature data within the measurement uncertainties. The measured binary vapor-liquid equilibrium data are modeled using the PCP-SAFT equation of state. Phase equilibrium data calculated from PCP-SAFT are compared to experimental data from literature. The data deviate by less than 1% in terms of pressure and vapor phase composition for given temperature and liquid phase composition demonstrating the reliability of the presented setup for vapor-liquid equilibrium measurements.
High-pressure vaporliquid equilibria of the second generation biofuel blends (2-methylfuran+iso-octane) and (2-methyltetrahydrofuran+di-n-butyl ether) : Experiments and PCP-SAFT modeling
Liebergesell, Bastian; Kaminski, Sebastian; Pauls, Christoph; et al. (2015)
Fluid Phase Equilibria
Vapor–liquid equilibria are investigated for two promising biofuel blends: 2-methylfuran (2-MF) + iso-octane and 2-methyltetrahydrofuran (2-MTHF) + di-n-butyl ether (DNBE). Vapor–liquid equilibria of fuels are of major importance as critical factor for the air–fuel mixture formation in a combustion engine. We collected bubble-point pressures of these two binary biofuel blends. The experiments were conducted in the temperature range of 353–508 K at pressures of up to 3.7 MPa using a visual synthetic method (Cailletet method). A slight positive deviation from ideal behavior was found for the mixture of 2-MF + iso-octane. The extent of the deviation increases with decreasing temperature. A more pronounced negative deviation from ideal behavior was found for the mixture 2-MTHF + DNBE. The extent of the negative deviation increases with increasing temperature. For correlation of the experimental data, the PCP-SAFT equation of state was used in combination with one-fluid mixing rules, using a binary interaction parameter for the dispersion interaction. It was shown that PCP-SAFT correctly predicts the mixture behavior from pure component data only.

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