Development of vapour liquid equilibrium calculation methods for chemical engineering design

This thesis deals with the development of computational methods for vapour liquid equilibrium (VLE) and volumetric properties. The VLE in this thesis can be divided into the low- and medium-pressure VLE with an experimental part and into the high-pressure VLE with a modelling and simulation part. The volumetric properties in this thesis deal with the extension of the model for compressed liquid densities. At low-pressure VLE, the emphasis was on the optimisation of model parameters. Two apparatus were built, a circulation still and an automated total pressure apparatus for the vapour liquid equilibrium measurements. The measurements were correlated with activity coefficient models for the liquid phase and with equations of state for the vapour phase. A program for correlating the vapour liquid equilibrium was developed. The measurements and VLE models optimised were needed in developing gasoline additives to replace methyl tertiary-butyl ether (MTBE). At near-critical VLE, the emphasis was on the robustness of the VLE and simulation routines. There was a need for a simulator to find out the dynamics of several vessels and buffer tanks when vessels were in a runaway condition, exposed to fire and imbalance of flows, or all of these events simultaneously. In addition, the operation point near the VLE critical point was of special interest. A dynamic simulator where the vapour and liquid phases were assumed to be in equilibrium was developed. The pressure relieving devices were assumed to be the only devices to control the flow of material. The effect of the pipe network was not included in the simulator. The temperature range of the model for the compressed liquid density of mixture was extended. The rigorous bubble point pressure and the critical point computed from the cubic equation of state were more consistent with the experimental data than the pseudo-bubble point and pseudo critical point of the original model. The application range of the model was extended at the expense of accuracy, but the extended model was better than a cubic equation of state.reviewe

A comparative study of water-immiscible organic solvents in the production of furfural from xylose and birch hydrolysate

Furfural (FUR) was produced from xylose using a biphasic batch reaction system. Water-immiscible organic solvents such as isophorone, 2-methyltetrahydrofuran (2-MTHF) and cyclopentyl methyl ether (CPME) were used to promptly extract FUR from the aqueous phase in order to avoid the degradation to humins as largely as possible. The effect of time, temperature, organic solvent and organic-to-aqueous ratio on xylose conversion and FUR yield were investigated in auto-catalyzed conditions. Experiments at three temperatures (170, 190 and 210 degrees C) were carried out in a stirred microwave-assisted batch reactor, which established the optimal conditions for achieving the highest FUR yield. The maximum FUR yields from xylose were 78 mol% when using CPME, 48 mol% using isophorone and 71 mol% in the case of 2-MTHF at an aqueous to organic phase ratio of 1:1 (v/v). Birch hydrolysate was also used to show the high furfural yield that can be obtained in the biphasic system under optimized conditions. The present study suggests that CPME can be used as a green and efficient extraction solvent for the conversion of xylose into furfural without salt addition. (C) 2019 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.Peer reviewe

DOI:10.1068/htwu303 Accuracy of vapour ^ liquid critical points computed from cubic equations of state

Abstract. The calculation methods for the critical point of vapour ^ liquid mixtures can be classified into empirical and rigorous methods. Both methods are briefly presented and calculated critical points are compared to measured ones. The rigorous methods are found to be more accurate. The rigorous methods are divided into indirect and direct methods and they utilise some equation of state. In the indirect method the whole phase envelope is calculated and the critical point is interpolated. In this work the direct method of Heidemann and Khalil is studied with three equations of state: Soave ^ Redlich ^ Kwong (SRK), Peng ^ Robinson (PR), and Adachi ^ Lu ^ Sugie (ALS), together with volume translation added to SRK and PR. These equations of state are accurate in critical temperature and pressure but PR and ALS are more accurate in critical molar volume than SRK.

Isobaric Vapor-Liquid Equilibrium of the Binary Mixtures Toluene + Styrene and Styrene + α-Methylstyrene

Funding Information: Roshi Dahal acknowledges the financial support of Fortum and Neste Foundation for the postgraduate studies and Business Finland for the project. Many thanks to Jerald Foo for determining the water content in pure components. Publisher Copyright: © 2023 The Authors. Published by American Chemical Society.Isobaric vapor-liquid equilibria of the binary mixtures toluene + styrene at 30 and 40 kPa and styrene + α-methylstyrene at 20 and 25 kPa were measured applying a recirculation still. The measured vapor-liquid equilibrium data were modeled adopting the non-random two-liquid (NRTL) excess Gibbs energy model with the RK (Redlich-Kwong) equation of state. The NRTL binary interaction parameter optimization was carried out employing own measured data and literature data for the toluene + styrene system. The applied model correlates well with the experimental data at the pressure range of 101-30 kPa. Moreover, the NRTL binary parameter regression was performed applying own measured data and literature data separately for the styrene + α-methylstyrene system. The model fitted with the parameters obtained from own measured data described the multiphase behavior of the system better than the parameters obtained from literature data. Additionally, the binary systems showed ideal behavior over the whole range of investigation as the calculated activity coefficients approached unity and no azeotropes were observed.Peer reviewe

Vapor- liquid equilibrium for the n-dodecane + phenol and n-hexadecane + phenol systems at 523 K and 573 K

A continuous flow apparatus was applied to measure the phase equilibrium at 523 K and 573 K. The performance of the apparatus was analysed with the determination of vapor pressures of water at the temperatures (T = 453 K and 473 K). The measured water vapor pressures deviated from the literature values less than 1 %. Vapor pressures of n-dodecane, n-hexadecane and phenol were measured at the temperatures (T = 523–623 K) and, the bubble point pressures of n-dodecane + phenol and n-hexadecane + phenol were measured at the temperatures (T = 523 K and 573 K). The measured vapor pressures of the pure components were compared with the literature values. Relative vapor pressure deviated from the literature value less than 2 % for all the measured vapor pressures. The measured vapor pressures value in this work agreed well with the literature, which indicates that the measurement apparatus and the method can produce good-quality data. The measured bubble point pressures for the n-dodecane + phenol and n-hexadecane + phenol systems were modeled with Peng-Robinson and Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) equations of state and Non-random Two-liquid (NRTL) activity coefficient model. The measured systems were at first modeled with Peng-Robinson and Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) equations of state without binary interaction parameters. Additionally, the parameters were regressed to optimize the performance of the models. The NRTL activity coefficient model described the behaviour of the measured and the literature data better than the equations of state. Furthermore, the Peng-Robinson equation of state resulted in better predictions than PC-SAFT equation of state even without binary interaction parameters regression. Both equations of state modeled the phase equilibrium behaviour of the system well. The n-dodecane + phenol system showed azeotropic behaviour.

Liquid – liquid equilibria in binary and ternary systems of phenol + hydrocarbons (n–dodecane or n–hexadecane) and water + phenol + hydrocarbons (n–dodecane or n–hexadecane) at temperatures between 298K and 353K

Funding Information: Roshi Dahal acknowledges Fortum and Neste Foundation for the financial support. Many thanks to Dr. Pia Lappalainen for reading and providing suggestions for language improvements. Publisher Copyright: © 2022This study reports liquid–liquid equilibrium (LLE) and liquid–liquid–liquid equilibrium (LLLE) data for binary (phenol + n-dodecane, or n-hexadecane) and ternary (water + phenol + n-dodecane, or n-hexadecane) systems measured under atmospheric pressure. The compositions of coexisting phases were determined with analytical and cloud point methods at temperatures 298 K – 353 K. The Non–Random Two–Liquid (NRTL) excess Gibbs energy model was employed to correlate the measured systems. The binary interaction parameters were regressed using analytical LLE and cloud point data. In addition, the parameters were also calculated using the binary LLE data combined with the isothermal vapor–liquid data from the literature applying the NRTL–RK (Redlich–Kwong) property method. The average absolute deviations in liquid mole fraction obtained with the NRTL model (using six adjusted parameters) for the LLE and VLE experimental data were 0.006 and 0.014 respectively. The phase equilibria of binary phenol + hydrocarbon (n-dodecane or n-hexadecane) systems were modeled at the temperature range of 313 K – 573 K.Peer reviewe

Vapor pressures, densities, and PC-SAFT parameters for 11 bio-compounds

One major sustainable development goal is to produce chemicals and fuels from renewable resources, such as biomass, rather than from fossil fuels. A key part of this development is data on the properties of chemicals that appear in this bio-based supply chain. Many of the chemicals have yet to be studied thoroughly, and data on their properties is lacking. Here we present new experimental data on the properties of 11 bio-compounds, along with PC-SAFT parameters for modeling their properties. The measured data includes vapor pressures, compressed densities, and refractive indexes. The 11 bio-compounds are tetrahydrofuran, 2-pentanone, furfural, 2-methoxy-4-methylphenol, 2-methylfuran, dihydrolevoglucosenone, cyclopentyl methyl ether, 2-sec-butylphenol, levoglucosenone, γ-valerolactone, and 2,6-dimethoxyphenol

110th Anniversary

A new improved apparatus is presented for measurements of critical points and vapor pressures of pure compounds. Additionally, with this apparatus it is possible to measure bubble and critical points of mixtures. The experimental temperature range is from 298 to 673 K, and the experimental pressure range is from 0 to a maximum of 20 MPa. Measurements of pure component vapor pressures and critical points are presented for ethanol, n-hexane, furan, 2-methylfuran, 2-methoxy-2-methylpropane (MTBE), and 2-ethoxy-2-methylbutane (TAEE). The measured properties are compared to literature data if available. The vapor pressure correlation of Wagner is used to correlate the measured vapor pressure data. Measurements of critical and bubble point of mixtures are presented for the ethanol + n-hexane system and are well in-line with literature data. Bubble and critical point measurements are presented for the furan + n-hexane mixture, where no literature data is available. The measured bubble points of mixtures are modeled with the Soave-Redlich-Kwong equation of state. The optimization of its binary interaction parameters is based on the bubble point measurements enabling the modeling of the critical loci of the mixture.Peer reviewe

Conceptual design of a distillation process for the separation of styrene monomer from polystyrene pyrolysis oil: experiment and simulation

This study presents experiments and modeling of batch distillation for the separation of styrene monomer from polystyrene pyrolysis oil. The bottoms obtained from the batch distillation was further fractionated applying a short-path distillation unit to study the separation efficiency of styrene from the polystyrene pyrolysis oil. GC-FID and GCMS were applied for the composition analysis of the polystyrene pyrolysis oil, distillate, and bottom fractions. Styrene monomer was obtained with a purity of 99.9 wt% from the batch distillation. The batch distillation was modeled employing the NRTL–RK thermodynamic model. A good agreement was achieved for the purity of styrene between the experimental analysis and model prediction. Additionally, a continuous distillation column was modeled for the scale-up of the process. Furthermore, viscosities and densities of the bottoms fraction were measured at the temperature range of 298–348 K.</p