Molecular shape dependent model of self-diffusion in, and the viscosity of, large molecule liquid systems. 2. Viscosity, temperature, and pressure relationships for model liquid hydrocarbons

1992 ◽  
Vol 114 (17) ◽  
pp. 6785-6790 ◽  
Author(s):  
Deyan Wang ◽  
Kenneth A. Mauritz
Keyword(s):  
Molecular Shape ◽  
Large Molecule ◽  
Liquid Hydrocarbons ◽  
Self Diffusion ◽  
Model Liquid ◽  
Liquid Systems ◽  
Dependent Model ◽  
Temperature And Pressure

scholarly journals Liquid-Liquid Extraction in Systems Containing Butanol and Ionic Liquids – A Review

2017 ◽  
Vol 38 (1) ◽  
pp. 97-110 ◽  
Author(s):  
Artur Kubiczek ◽  
Władysław Kamiński
Keyword(s):  
Ionic Liquids ◽  
Room Temperature ◽  
Liquid Extraction ◽  
Butanol Production ◽  
Model Liquid ◽  
New Class ◽  
Liquid Liquid Extraction ◽  
Liquid Systems ◽  
Nrtl Equation ◽  
Equilibrium Data

AbstractRoom-temperature ionic liquids (RTILs) are a moderately new class of liquid substances that are characterized by a great variety of possible anion-cation combinations giving each of them different properties. For this reason, they have been termed as designer solvents and, as such, they are particularly promising for liquid-liquid extraction, which has been quite intensely studied over the last decade. This paper concentrates on the recent liquid-liquid extraction studies involving ionic liquids, yet focusing strictly on the separation of n-butanol from model aqueous solutions. Such research is undertaken mainly with the intention of facilitating biological butanol production, which is usually carried out through the ABE fermentation process. So far, various sorts of RTILs have been tested for this purpose while mostly ternary liquid-liquid systems have been investigated. The industrial design of liquid-liquid extraction requires prior knowledge of the state of thermodynamic equilibrium and its relation to the process parameters. Such knowledge can be obtained by performing a series of extraction experiments and employing a certain mathematical model to approximate the equilibrium. There are at least a few models available but this paper concentrates primarily on the NRTL equation, which has proven to be one of the most accurate tools for correlating experimental equilibrium data. Thus, all the presented studies have been selected based on the accepted modeling method. The reader is also shown how the NRTL equation can be used to model liquid-liquid systems containing more than three components as it has been the authors’ recent area of expertise.

Self-diffusion of lignite/water under different temperatures and pressure: A molecular dynamics study

2016 ◽  
Vol 30 (01) ◽  
pp. 1550253 ◽  
Author(s):  
Xinjian Liu ◽  
Yu Jin ◽  
Congliang Huang ◽  
Jingfeng He ◽  
Zhonghao Rao ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Water System ◽  
Simulation Method ◽  
The Self ◽  
Dynamics Simulation ◽  
Low Rank ◽  
Self Diffusion ◽  
Change Mechanism ◽  
Different Temperatures ◽  
Temperature And Pressure

Temperature and pressure have direct and remarkable implications for drying and dewatering effect of low rank coals such as lignite. To understand the microenergy change mechanism of lignite, the molecular dynamics simulation method was performed to study the self-diffusion of lignite/water under different temperatures and pressure. The results showed that high temperature and high pressure can promote the diffusion of lignite/water system, which facilitates the drying and dewatering of lignite. The volume and density of lignite/water system will increase and decrease with temperature increasing, respectively. Though the pressure within simulation range can make lignite density increase, the increasing pressure showed a weak impact on variation of density.

scholarly journals Molecular Simulation of the Adsorption and Diffusion in Cylindrical Nanopores: Effect of Shape and Fluid–Solid Interactions

Molecules ◽  
2019 ◽  
Vol 24 (3) ◽  
pp. 608 ◽  
Author(s):  
Harry Cárdenas ◽  
Erich Müller
Keyword(s):  
Decisive Role ◽  
Molecular Shape ◽  
Type I ◽  
Surface Strength ◽  
Bulk Fluid ◽  
Self Diffusion ◽  
Interaction Sites ◽  
Adsorbed Phase ◽  
Dynamics Simulations ◽  
And Diffusion

We report on molecular simulations of model fluids composed of three tangentially bonded Lennard-Jones interaction sites with three distinct morphologies: a flexible “pearl-necklace” chain, a rigid “stiff” linear configuration, and an equilateral rigid triangular ring. The adsorption of these three models in cylindrical pores of diameters 1, 2, and 3 nm and with varying solid–fluid strength was determined by direct molecular dynamics simulations, where a sample pore was placed in contact with a bulk fluid. Adsorption isotherms of Type I, V, and H1 were obtained depending on the choice of pore size and solid–fluid strength. Additionally, the bulk-phase equilibria, the nematic order parameter of the adsorbed phase, and the self-diffusion coefficient in the direction of the pore axis were examined. It was found that both the molecular shape and the surface attractions play a decisive role in the shape of the adsorption isotherm. In general, the ring molecules showed a larger adsorption, while the fully flexible model showed the smallest adsorption. Morphology and surface strength were found to have a lesser effect on the diffusion of the molecules. An exceptional high adsorption and diffusion, suggesting an enhanced permeability, was observed for the linear stiff molecules in ultraconfinement, which was ascribed to a phase transition of the adsorbed fluid into a nematic liquid crystal.

scholarly journals Silicon Self-Diffusion in Stishovite: Calculations of Point Defect Parameters Based on the cBΩ Thermodynamic Model

2021 ◽  
Vol 6 (1) ◽  
pp. 6
Author(s):  
Vassilios Saltas ◽  
Filippos Vallianatos
Keyword(s):  
Point Defect ◽  
Thermodynamic Model ◽  
Diffusion Processes ◽  
Activation Entropy ◽  
Temperature Range ◽  
Self Diffusion ◽  
Dimensionless Constant ◽  
The Mean ◽  
Temperature And Pressure ◽  
Cbω Model

In the present work we apply the cBΩ thermodynamic model to study the diffusion of Si in stishovite crystal at high pressure and in a wide temperature range. According to this model, the point defect activation Gibbs free energy is expressed as a function of the bulk properties of the material, i.e., gact = cBΩ, where B is the isothermal bulk modulus, Ω is the mean atomic volume, and c is a dimensionless constant. In this way, other important point defect parameters, such as the activation volume vact, the activation entropy sact, and the activation enthalpy hact may be estimated if the thermoelastic properties of the material are known over a wide temperature and pressure range. Our calculations are based on previously reported self-diffusion coefficients in stishovite single crystals measured at 14 GPa and at temperatures from 1400 to 1800 °C, in the [110] and [001] directions, by Shatskiy et al. (Am. Mineral. 2010, 95, 135–43). Furthermore, the EOS of stishovite, proposed by Wang et al. (J. Geophys. Res. 2012, 117, B06209) has been used for the accurate implementation of the cBΩ model. Our results suggest that the aforementioned point defect parameters exhibit considerable temperature dependence over the studied temperature range (1000–2000 °C). The estimated activation volumes (4.4–5.3 cm3/mol, in the range of 1400–1800 °C) are in agreement with reported experimental results. Our study confirms the potential of the cBΩ model for the theoretical investigation of diffusion processes in minerals, in order to overcome the experimental difficulties and the lack of experimental diffusion data in mantle conditions.

Note on the thermodynamic state of laminar flow and on the viscosity of liquids

1968 ◽  
Vol 46 (2) ◽  
pp. 249-255 ◽  
Author(s):  
E. A. Flood ◽  
R. F. Bartholomew
Keyword(s):  
Molecular Weight ◽  
Steady State ◽  
Laminar Flow ◽  
Flow Shear ◽  
Adjacent Layer ◽  
Static State ◽  
Self Diffusion ◽  
Avogadro’S Number ◽  
Ideal Gases ◽  
Temperature And Pressure

Fluids in a steady state of laminar flow (shear) are not in their thermodynamic equilibrium states. They have more energy and (or) less entropy than their corresponding static states.Phenomenological considerations suggest that in the case of 'ideal' liquids, shear states involve dilational energy increases, while in the case of ideal gases shear states involve entropy decreases associated with distortions of momentum fluxes.It is shown that the viscosities of some liquids (metals, hydrocarbons, water, etc.) can be described approximately by the equation[Formula: see text]where η is the viscosity, β the compressibility, D the coefficient of self-diffusion, M the molecular weight, ρ the density, and Nv Avogadro's number. F measures the strain or effective dilation necessary for a 'layer' to flow over an adjacent 'layer'. Ideally F should be about 0.06 but varies from about 0.05 for metals to 0.14 for water.Equation [a] implies that liquids in a state of laminar flow are somewhat dilated compared with the static state at the same temperature and pressure. The density change as a function of the velocity gradient u′ is given by[Formula: see text]

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