Vapour liquid equilibrium measurements for process design

In recent years it has become increasingly important to develop new oxygenate and isooctane technologies and processes that meet the continuously stricter environmental requirements. Some of the new process schemes use renewable raw materials in order to meet the European Union biofuel requirements. One of the most important requirements for the design of such separation processes includes the knowledge of vapour liquid equilibrium (VLE) behaviour. There are methods to estimate VLE but for the final design and with new systems VLE needs to be determined experimentally. Unfortunately, the existing equipment used for the VLE measurements suffer from labour intensiveness. The application of automation to VLE measurement apparatuses provides increasing accuracy and speed, thus reducing the cost for VLE measurements. In the present work three different apparatuses were developed. Using the constructed apparatuses, VLE was measured for relevant systems in the modelling and design of oxygenate and isooctane technologies. Firstly, a static apparatus for VLE measurements was built, which allowed the analysis of samples from the liquid and vapour phases, by means of an automated sampling system. Measurements were made on ethanenitrile + 2-methylpropane and ethanenitrile + 2-methylpropene systems. No VLE measurements were not found in the current literature for the systems measured with the static apparatus in this work. The systems measured disclosed a positive deviation from Raoult's law. In addition, azeotropic behaviour was observed for the ethanenitrile + 2-methylpropane system. Secondly, a circulation still was made. The still was used to obtain isobaric and isothermal VLE data for nine alkane + alcohol and alkene + alcohol binary systems. An on-line system with circulation of the samples was tested with two analysis methods, mass spectrometry and gas chromatography. The on-line system was then applied to the ethanol + 2,4,4-trimethyl-1-pentene and 2-propanol + 2,4,4-trimethyl-1-pentene systems at atmospheric pressure and vapour pressure was determined for 2-methoxy-2,4,4-trimethylpentane. VLE measurements were made for the methanol + 2-methoxy-2,4,4-trimethylpentane system. Again, no VLE measurements were found in existing for most of the systems measured with the recirculation still. The results exhibited positive deviation from Raoult's law. All the systems measured exhibited azeotropic behaviour, with the exception of the methanol + 2-methoxy-2,4,4-trimethylpentane system. Thirdly, a static total pressure apparatus was constructed. With the manual version of the apparatus 12 binary systems consisting of alkanes + 2-butanol and alkenes + alcohols were measured. The static total pressure apparatus was upgraded to one of a computer-controlled level, which requires substantially less labour than the manual version of the apparatus. Using the computer-controlled version, measurements were made for five binary systems consisting of 2-methylpropene + alcohols. Most of the measurements made with the static total pressure apparatus were for systems for which measurements have not been available earlier. The systems measured exhibited positive deviation from Raoult's law and some of the systems exhibited azeotropic behaviour. The gamma-phi approach was used for modelling the systems measured. The vapour phase was calculated with the Soave modification of the Redlich-Kwong-equation and the Wilson activity coefficient model was used for modelling the liquid phase behaviour. Legendre-polynomials were used in the Barker's method for the data reduction of the static total pressure measurements. In addition to the Wilson equation parameters, NRTL and UNIQUAC activity coefficient model parameters were also determined for the C4-alkene + alcohol systems measured with the static total pressure apparatus. The Wilson equation provided the best fit of the measurements, compared to NRTL and UNIQUAC models. The Antoine-equation was used for describing the vapour pressures of the pure components with the exception of the static total pressure measurements, for which the actual measured vapour pressure values were used.reviewe

Vapor-Liquid Equilibrium of Ionic Liquid 7-Methyl-1,5,7-triazabicyclo[4.4.0]dec-5-enium Acetate and Its Mixtures with Water

Ionic liquids have the potential to be used for extracting valuable chemicals from raw materials. These processes often involve water, and after extraction, the water or other chemicals must be removed from the ionic liquid, so it can be reused. To help in designing such processes, we present data on the vapor-liquid equilibrium of the system containing protic ionic liquid 7-methyl-1,5,7-triazabicyclo [ 4.4.0 ] dec-5-enium acetate, water, acetic acid, and 7-methyl-1,5,7-triazabicyclo [4.4.0] dec-5-ene. Earlier studies have only focused on mixtures of water and an ionic liquid with a stoichiometric ratio of the ions. Here, we also investigated mixtures containing an excess of the acid or base component because in real systems with protic ionic liquids, the amount of acid and base in the mixture can vary. We modeled the data using both the ePC-SAFT and NRTL models, and we compared the performance of different modeling strategies. We also experimentally determined the vapor composition for a few of the samples, but none of the modeling strategies tested could accurately predict the concentration of the acid and base components in the vapor phase.Peer reviewe

Physical Properties of 7-Methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (mTBD)

7-Methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (mTBD) has useful catalytic properties and can form an ionic liquid when mixed with an acid. Despite its potential usefulness, no data on its thermodynamic and transport properties are currently available in the literature. Here we present the first reliable public data on the liquid vapor pressure (temperature from 318.23K to 451.2K and pressure from 11.1Pa to 10000Pa), liquid compressed density (293.15K to 473.15K and 0.092MPa to 15.788MPa), liquid isobaric heat capacity (312.48K to 391.50K), melting properties, liquid thermal conductivity (299.0K to 372.9K), liquid refractive index (293.15K to 343.15K), liquid viscosity (290.79K to 363.00K), liquid-vapor enthalpy of vaporization (318.23K to 451.2K), liquid thermal expansion coefficient (293.15K to 473.15K), and liquid isothermal compressibility of mTBD (293.15K to 473.15). The properties of mTBD were compared with those of other relevant compounds, including 1,5-diazabicyclo(4.3.0)non-5-ene (DBN), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), and 1,1,3,3-tetramethylguanidine (TMG). We used the PC-SAFT equation of state to model the thermodynamic properties of mTBD, DBN, DBU, and TMG. The PC-SAFT parameters were optimized using experimental data.Peer reviewe

Hydrogen solubility measurements of analyzed tall oil fractions and a solubility model

Knowledge of hydrogen solubility in tall oil fractions is important for designing hydrotreatment processes of these complex nonedible biobased materials. Unfortunately measurements of hydrogen solubility into these fractions are missing in the literature. This work reports hydrogen solubility measured in four tall oil fractions between 373 and 597 K and at pressures from 5 to 10 MPa. Three of the fractions were distilled tall oil fractions their resin acids contents are respectively 2, 20 and 23 in mass-%. Additionally one fraction was a crude tall oil (CTO) sample containing sterols as the main neutral fraction. Measurements were performed using a continuous flow synthetic isothermal and isobaric method based on the visual observation of the bubble point. Composition of the flow was changed step-wise for the bubble point composition determination. We assume that the tall oil fractions did not react during measurements, based on the composition analysis performed before and after the measurements. Additionally the densities of the fractions were measured at atmospheric pressure from 293.15 to 323.15 K. A Henry's law model was developed for the distilled tall oil fractions describing the solubility with an absolute average deviation of 2.1%. Inputs of the solubility model are temperature, total pressure and the density of the oil at 323.15 K. The solubility of hydrogen in the CTO sample can be described with the developed model with an absolute average deviation of 3.4%. The solubility of hydrogen increases both with increasing pressure and/or increasing temperature. The more dense fractions of the tall oil exhibit lower hydrogen solubility in comparison to the less dense fractions. The increase in the density of a fraction corresponds to an increased resin acid and sterol content of the sample. Sterols and resin acids exhibit lower hydrogen solubility in comparison to fatty acids

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- 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.

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

Distillable Protic Ionic Liquid 2‑(Hydroxy)ethylammonium Acetate (2-HEAA): Density, Vapor Pressure, Vapor–Liquid Equilibrium, and Solid–Liquid Equilibrium

Recently it has been found that certain ionic liquids (ILs) have notable vapor pressures (Earle et al. <i>Nature</i> <b>2006</b>, <i>439</i>, 831–834). These ILs may be important in various novel technologies, but they may also be important in postcombustion carbon captures as side products. In this work a distillable protic ionic liquid (PIL) 2-(hydroxy)­ethylammonium acetate (2-HEAA) was prepared from monoethanolamine (MEA) and acetic acid (HAc) and it was purified with a Vigreaux type distillation column under vacuum. Density was measured for the MEA + 2-HEAA and HAc + 2-HEAA systems with a DMA HP densimeter from 293 to 363 K. The Redlich–Kister polynomial was used to model the density data. Vapor–liquid equilibrium was measured for the H₂O + HAc + 2-HEAA system with a static total pressure apparatus at 347 K. Solid–liquid equilibrium was measured for the H₂O + HAc + 2-HEAA system with a visual method. The NRTL activity coefficient model was used to model the vapor–liquid and solid–liquid equilibrium data