Search

To develop efficient ionic liquid (IL)-based separation processes like extractive distillation, the knowledge of IL-involved vapor–liquid equilibria (VLE) is necessary. Since experimental measureme...

A study is performed of the accuracy of free energy F of a vapor–liquid system, calculated with modified fluid models in the quasi-chemical approximation (QCA) of the lattice gas model. Two ways of modifying the fluid model are discussed: (1) allowing for the softness of the lattice, which alters its weighted average parameter according to the density of the fluid and (2) jointly considering the translational and vibrational molecular motions in a rigid lattice. The effect the model of introducing the weighted average parameter of a soft lattice has on the calculated characteristics is analyzed. Calculations of the free energy using the analytical QCA formula (which contains no such modifications) are compared to thermodynamic relationships obtained with a chemical potential that considers them. It is found that both modifications of the fluid model result in distinctions between the two ways of calculating the free energy that grow along the density of the system. These distinctions are apparent at high densities and on the concentration dependence of pressure. The analytical QCA expression quantitatively estimates F values when there are small contributions from model modifications.

The problem of comparing thermosyphons in terms of engineering solutions used for cooling the pile foundations of residential buildings in the regions of the Far North is considered. For comparison, specific self-cooling units (SCU) of two types were selected, including liquid SCU 1 with a pipe diameter of 120 mm and a vapor-liquid SCU 2 with a pipe diameter of 50 mm. Simple analytical calculations proved the thermal efficiency of SCU 2 to be 1.4 times less than that of SCU 1, which is primarily related to the pipe diameter. Numerical calculations using the TEMPA software package have demonstrated that, despite the slightly greater cooling effect of SCU 1, the temperature field for September of the third calculation year is leveled for both devices.

New phase equilibrium data of CO2 in n-hexadecane, n-heptadecane, n-octadecane, n-nonadecane, and n-eicosane were measured at temperatures from 333.15 to 373.15 K up to 23.73 MPa by a constant-volu...

The isobaric binary vapor–liquid equilibrium (VLE) data for the mixture of 2-phenylethanol (2PEA) with 1-phenylethanol (1PEA), 2-phenylpropan-2-ol (2P2P), ethylbenzene (ETB), and isopropylbenzene (...

Isoprenol (3-methyl-3-buten-1-ol) is an important intermediate in the chemical industry and is used, for example, in the production of various scent and flavor chemicals. Isoprenol is produced from aqueous formaldehyde and isobutene and is separated by distillation from mixtures containing formaldehyde, water, and isobutene in the process. As formaldehyde forms oligomers with both water and isoprenol, these mixtures are complex reacting systems, which are not easy to separate. Hence, for understanding and modeling the process, information on the vapor–liquid equilibria and the chemical equilibria in the system (formaldehyde + water + isoprenol) is essential. However, only very limited data on this system are available in the literature. Therefore, in the present work, vapor–liquid equilibria were measured in the following systems: system (water + isoprenol) at 20 and 90 kPa, system (formaldehyde + isoprenol) at 373 and 393 K, and system (formaldehyde + water + isoprenol) at 373 K. Furthermore, the chemical equilibria of the oligomerization reactions of formaldehyde and isoprenol were studied with 13C-NMR spectroscopy at temperatures ranging from 283 to 353 K. The experimental data were used to extend a physico-chemical model of the system (formaldehyde + water) from the literature to include isoprenol.

Because of their toxicity, flammability, and chemical instability, the vapor–liquid equilibria of the group V hydrides, phosphine, arsine, and stibine are underexplored. Gibbs ensemble Monte Carlo ...

Several industries have steadily gained interest in gas hydrate technologies for their potential use in natural gas transport and storage applications. Additives which optimize the efficiencies of ...

Pigging technology is widely used in the oil and gas industry. During the course of pigging, after a water pressure test, the instability of the pig caused by terrain fluctuation can affect the stable operation of the pipeline and even cause burst accidents. This paper describes the four stages of pig movement in an inclined pipeline, with vapor-liquid eruption occuring in the last stage. A hydraulic transient model of the pigging operation after a water pressure test is established based on mass conservation and motion equations, the dynamic equation of the pig, and the vapor-liquid eruption model. The model can simulate the status of fluid flow in the pipeline, track the movement of the pig, and predict the pressure pulses. The simulation results are consistent with the data of two burst accidents, which verifies the correctness of the established model and the reliability of the calculated results. It can therefore provide a reliable and effective theoretical basis for developing a pigging plan on site.

The explosion characteristics of vapor-liquid two-phase n-heptane inside and outside (the boundary is the junction of premixed fuel and air) the original premixed zone studied, and the effects of concentration and initial temperature on the explosion development have been analyzed using a numerical method. The explosion overpressure increases with distance in a certain range outside the premixed zone with the change of premixed vapor-liquid two-phase n-heptane concentrations. The peak overpressure of rich fuel is larger than that of lean and stoichiometric fuel. The fuel rich explosion outside the premixed zone results in a so-called "secondary explosion", and the explosion overpressure has two peaks with similar values. The initial temperature has a significant effect on the flame length (characterization by combustion rate) of two-phase n-heptane explosion. The flame length of a lean fuel explosion decreases with the increase of initial temperature. At an initial temperature of 253 K, the flame length is 4.15 times that of the premixed zone. With stoichiometric and rich fuel, the flame length increases with the initial temperature in the range of 273−333 K, and at 333 K the flame length is 5.26 and 5.99 times that of the premixed zone, respectively.

Separation vessels are traditionally designed based on rules of thumb that guide the designer to a feasible solution. Despite its widespread use, this approach presents important limitations, which...

Because of the outstanding physical and chemical properties of biomass-originated γ-valerolactone (GVL), it has been characterized as a promising alternative platform molecule, which can be utilize...

This work studied the separation effect of 1-hexyl-3-methylimidazolium-based ionic liquids (1-hexyl-3-methylimidazolium tetrafluoroborate [HMIM][BF4] and 1-hexyl-3-methylimidazolium trifluoromethan...

A unified description of three types of two-phase interfaces (vapor–liquid, solid–vapor, and solid–liquid) at a vapor–liquid meniscus inside a slit-like pore are considered on the basis of the lattice gas model. This approach allows equally accurate calculations of molecular distributions in heterogeneous distributed models of transitional regions at all interfaces. It is assumed that pore walls cannot be deformed, and they create an external field for a stratifying fluid. Adsorption films form at solid–mobile phase interfaces due to the potential of adsorbate–adsorbent interaction. The state of the coexisting vapor-in-a-pore and liquid-in-a-pore phases satisfy the equality of the chemical potential that excludes the appearance of metastable states. Conditions for distinguishing regions of the system that lie beyond solid–liquid–vapor three-phase contact are discussed. A procedure is discussed for introducing a contact angle into a liquid–vapor–solid pore wall system through molecular distributions of the adsorbate in a slit-like pore. Dependences of the width of the considered interfaces and the contact angle as a function of the pore width and pore wall potential are found.

The computation methods of the thermodynamic properties are used for theoretical studies of multicomponent refrigerant blends (MRBs) for low-temperature throttling refrigeration units, providing cryostatting modes for cooled objects in the temperature range of –90 – –160 °С. The article presents the comparative analysis of the state equations for calculating thermodynamic properties of multicomponent refrigerant mixtures. Quantitative and qualitative differences in the results of calculations in the lowtemperature region are determined.

A compilation of available experimental data for acetone-water mixtures with the reciprocal salt system Na+, K+ || Cl−, SO4 2− is presented. Significant inconsistencies among experimental data are pointed out. New freezing point measurements are reported for the binary acetone-water system at 12 different compositions. UNIQUAC parameters are determined on the basis of the available data from literature. Modeling results are presented. Vapor-liquid, liquid-liquid, and solid-liquid equilibria together with thermal properties are reproduced well by the model using only 14 parameters. The major drawback of the model is that the calculated liquid-liquid equilibrium regions of systems with KCl and NaCl are larger than the experimentally determined regions. The model is valid in the temperature range from −16 to 100 °C.

The continuum quasichemical approximation is used to improve the accuracy of describing molecular distributions in a vapor–liquid system. It considers displacements of the molecular center of mass from the center of a cell within the lattice gas model. It also allows for (as in its discrete variant) direct correlations of interacting molecules. The probability density of a molecule being inside the cell is used as a continuous function of its coordinate. An algorithm for solving a system of integral equations is developed with respect to the pair distribution function. The effect the continuum description of the particle distribution has on the concentration dependences of the main thermodynamic functions is investigated. The approach is shown to explain the concentration dependence of the parameter of effective lateral interaction.

Methanol and methylal form a minimum boiling point azeotrope and cannot be separated by conventional distillation. In this paper, the azeotrope was separated by extractive distillation with cyclohe...

The experimental vapor–liquid equilibrium (VLE) data for a ternary system of β-caryophyllene + dipentene + α-pinene and two binary systems composed of β-caryophyllene (1) + dipentene (2) and dipent...

The vapor–liquid–solid (VLS) mechanism is probably the most versatile method to fabricate semiconductor nanowires and several investigations assume a compositionally homogeneous catalyst particle. In this investigation we address the compositional homogeneity of the catalyst particle during growth of nanowires. Using diffusion calculations, we show that the particle is indeed homogeneous during VLS growth, but can have a strong concentration gradient during vapor–solid–solid growth, that is, growth with a solid particle. We also show that the response to a concentration change is extremely fast, meaning that if the concentration at the surface of the particle changes, the entire particle reaches this new concentration effectively instantaneously.

Ethyl propionate is usually produced from esterification of propionic acid and ethanol in the industry. However, the purification of ethyl propionate remains a challenge because the unreacted ethan...

It is a considerable challenge for the phase behavior of chemical separation industry to correlate and predict the vapor–liquid equilibria (VLE) data of the binary and ternary systems containing as...

Vapor–liquid equilibrium (VLE) data (T, p, x, y) are vital for the development of mixture thermodynamic models. Herein, we demonstrate the use of nuclear magnetic resonance (NMR) spectroscopy as an...

Isobaric vapor–liquid equilibria (VLE) at 50.0, 101.3, and 200.0 kPa, have been measured for the binary system methyl nonafluorobutyl ether (x1) HFE-7100 + (1 – x1) 2-propanol. Thermodynamic consis...

A new experimental methodology has been developed to measure bulk mass densities and interfacial tensions of mixtures at vapor−liquid−liquid equilibria (VLLE). This technique considers the use of a...

Data of vapor–liquid equilibria are essential in the design of a separation unit in the technology of cyclic alkene indirect hydration in the presence of formic acid. This work aims at measuring th...

In the present work, vapor–liquid phase equilibrium (VLE) analyses of binary systems of aniline with four isomers of xylene, comprising p-xylene, m-xylene, o-xylene, and ethylbenzene, are reported ...

Direct growth of single-crystal compound semiconductors on nonepitaxial substrates is a promising route for device processing simplification in electronic and optoelectronic applications. However, the nonepitaxial growth technique for 2D single crystals is still a fundamental challenge. Here, we demonstrate that the macroscopic 2D interface of liquid metals and nonepitaxial solid substrates could be universally designed for the chemical vapor deposition growth of crystalline compound semiconductors. By adopting a sandwiched solid metal/liquid metal/solid substrate environment, millimeter-scale 2D GaS, 2D GaSe, and 1D GaTe single crystals of high quality were synthesized at the interface of liquid gallium and nonepitaxial substrates. Evidence shows that the particle-catalyst-free vapor–liquid–solid growth is driven by screw dislocations. Furthermore, we successfully extend the growth strategy to various metal chalcogenides (Sn, In, Cu, and Ag) and pnictides (Sb). Our work opens up a new route for the direct growth of single-crystalline compound semiconductors on nonepitaxial substrates.

The thermodynamic properties of novel natural deep eutectic solvents (NDESs) based on amino acids are of great importance in extraction of pharmaceutical compounds. In this work, the vapor–liquid e...

This paper presents modified views on the vapor–liquid–solid mechanism of nanowire growth, relying on new experimental data on the wettability of a crystal surface by metal catalyst droplets presaturated with the crystallizing substance.

In this article we compare results from different heuristics approaches for the design of VLE separation vessels. In addition, we present an MILP model that embeds the aforementioned heuristics and considers the discrete nature of the geometric variables. We show that different heuristics render different results. In addition, while results from heuristics and MILP often coincide sometime, departures take place. Finally, we show that straight enumeration is viable option for stand-alone design.

γ-Valerolactone (GVL) has recently been considered as a suitable solvent for synthesis and catalysis. By the application of GVL in scaled-up processes, it can be mixed with various components, incl...

In this study, the experimental vapor?liquid equilibria data of the ternary Pb?Sn?Sb alloy system are determined using a new experimental method. The experimental VLE data passed the thermodynamic consistency test (Van Ness test), suggesting that the experimental results are reliable. The activities of the components of Pb?Sn?Sb ternary alloy and those of the corresponding three constituent binaries were calculated using the Wilson equation. The predicted values are in good agreement with the data determined from the experiments, and the average relative deviation and average standard deviation were smaller than ? 4.00% and ? 0.03 for all constituent binaries, respectively, which indicates that the Wilson equation is reliable for calculating the activity of the components of the Pb?Sn?Sb ternary alloy. The VLE data of the Pb? Sn and Sb?Sn binary alloys and Pb?Sn?Sb ternary alloy were calculated based on the VLE theory and the Wilson equation. The calculated VLE data were in good agreement with the data determined from the experiments, indicating that this method is reliable for calculating the VLE of alloy systems. The proposed study offers a valid method for analyzing the composition of products that are dependent on the distillation temperature and system pressure during vacuum distillation, which is of great significance to the experimental design of this process.