Study of Thermodynamic Modeling of Isothermal and Isobaric Binary Mixtures in Vapor-Liquid Equilibrium (VLE) of Tetrahydrofuran with Benzene (303.15 K) Cyclohexane (333.15 K), Methanol (103 kPa), and Ethanol (100 kPa)

Tetrahydrofuran (THF) is an aprotic solvent with multiple applications in diverse areas of chemical, petrochemical, and pharmaceutical industries with an important impact in chemical waste liquid with other solvents. In this work, 51 available VLE data, for isothermal binary mixtures of THF(1) + Benzene(2) and THF(1) + Cyclohexane(2) at 303.15 and 333.15 K, respectively, and isobaric THF(1) + Methanol(2) at 103 kPa and THF(1) + Ethanol(2) at 100 kPa were used in the development of the activity coefficient models. The quality of experimental data was checked using the Herington test. VLE binary data was correlated with models Wilson, NRTL UNIQUAC, and UNIFAC to obtain binary parameters and activity coefficients. The best thermodynamic consistency when conducting the Herington test for the VLE data was found for the THF(1) +Cyclohexane(2) isothermal system and THF(1) + Ethanol(2) isobaric system. The UNIQUAC model for isothermal systems THF(1) + Benzene(2) and THF(1) + Cyclohexane(2), the NRTL model for the isobaric system THF(1) + Methanol(2), and the UNIQUAC model for THF(1) + Ethanol(2) perform better than the other models.

Soluciones globales para sistema isotérmico con fuente

In this short note, we are concerned with the global existence of solutions to the isothermal system with source, where the inhomogeneous terms f(x,t,ρ,u)=b(x,t)ρ+(a′(x)/a(x))*ρu^2+α(x,t)ρu|u| are appeared in the momentum equation. Our work extended the results in the previous papers “Resonance for the Isothermal System of Isentropic Gas Dynamics” (Proc. A.M.S.139(2011),2821-2826), “Global Existence and Stability to the Polytropic Gas Dynamics with an Outer Force” (Appl. Math. Let-ters, 95(2019), 35-40) and “Existence of Global Solutions for Isentropic GasFlow with Friction” (Nonlinearity, 33(2020), 3940-3969), where the global solution was obtained for the source f(x,t,ρ,u)=(a′(x)/a(x))*ρu^2, f(x,t,ρ,u)=b(x,t)ρ, f(x,t,ρ,u)=α(x,t)ρu|u| respectively.

Atomistic investigation on the kinetics behavior of vapour adsorption and cluster evolutions using statistical rate theory approach

The kinetics behavior of vapor adsorption on solid surface in an isobaric-isothermal system are investigated by means of molecular dynamics simulations combined with theoretical studies through statistical rate theory approach....

QUASI-INVARIANTS OF CHEMICAL REACTIONS IN DISTRIBUTED SYSTEMS WITH DIFFUSION

For reactions occurring in distributed systems with longitudinal and radial diffusion, the relations between the concentrations of reagents and temperature remaining practically constant in time and space (space-time kinetic quasi-invariants) are found. A method for determining such quasi-invariants for chemical reactions occurring in the mixing reactor taking into account the diffusion of reagents and temperature changes in the longitudinal and radial directions has been developed and tested. The quasi-invariants found relate nonequilibrium concentrations of diffusing reagents and temperatures measured in two or more experiments with different initial conditions (multi-experiments), and practically do not change throughout the reaction both in length and in radius of the reactor. Analytical expressions for quasi-invariants are obtained, allowing a priori to estimate the corresponding constants (initial values). It is shown that the number of basic quasi-invariants is determined by the number of reagents. The application of the method is illustrated by the reaction of isomerization A=B in a non-isothermal system with diffusion of reagents. Found for this reaction quasiinvariant based on three-dimensional (surface) matched with three-dimensional variations of concentrations and temperature given the diffusivity in the course of the reaction. It is shown that quasi-invariants change in a smaller spatial range than their corresponding concentrations and temperatures in different experiments, i.e. remain practically constant in time and space. Visually, quasi-invariants are four-dimensional structures, three-dimensional projections of which are similar to "recumbent" waves, pillows, lenses, etc. Elaborated method for determining quasi-invariants of chemical reactions in systems with diffusion develops D.A. Frank-Kamenetsky's macrokinetic methods for approximate study of temporal and spatial characteristics of distributed dynamic systems. The obtained results can be used to solve inverse problems and optimize the operation modes of chemical mixing reactors with longitudinal and radial diffusion of reagents and temperature changes.

KINETICS OF HYDROGEN SEPARATION FROM REFINERY OFF-GAS

Adsorption and desorption kinetic curves for equimolar hydrogen – methane mixture on molecular sieve type 5A were experimentally obtained for pressure range 0.122 – 3.546 MPa.The linear driving force rate expression model was used to simulate the dynamic of adsorption and desorption in adiabatic fixed bed adsorber. The model takes into account the interference effects for non-linear isotherms and non-isothermal system. The equations were solved by backward finite difference method with a fixed gridding technique. The individual mass transfer parameters were obtained by matching the theoretical with the experimental data and found to be equal to 8.510 s-1 and 0.783 s-1 for hydrogen and methane, respectively.The predicted effluent histories were shown to be in close agreement with the experimental data for the system. The lowest relative capacity of the bed for methane was almost approximately 95% of that predicted equilibrium capacity. The predicted temperature profiles tracked the experimental temperature data points, but with higher values. Furthermore, the maximum temperature increasing was observed for the adsorption of methane onto 5A molecular sieve at 35 atmospheres and was recorded as 44 K.

A Formulation of L-Isothermic Surfaces in Three-Dimensional Minkowski Space

The Cartan structure equations are used to study space-like and time-like isothermic surfaces in three-dimensional Minkowski space in a unified framework. When the lines of curvature of a surface constitute an isothermal system, the surface is called isothermic. This condition serves to define a system of one-forms such that, by means of the structure equations, the Gauss-Codazzi equations for the surface are determined explicitly. A Lax pair can also be obtained from these one-forms for both cases, and, moreover, a nonhomogeneous Schrödinger equation can be associated with the set of space-like surfaces.

Nonequilibrium self-assembly induced Liesegang rings in a non-isothermal system

A formalism based on nonequilibrium self-assembly processes is proposed to understand the structures formation composing the Liesegang rings in a non-isothermal system.