Separation of Homogeneous Azeotropic Mixtures by Pressure Swing Distillation – Analysis of the Operation Performance

The complex separation of a homogenous azeotropic mixture by pressure swing distillation is analyzed based on a rigorous dynamic model considering the system acetonitrile/water. The model is validated with our own experimental data. Investigations showed that the process can be operated in a very stable and robust manner even when large disturbances set the feed concentration to the other distillation region.     

Separation of tert‐Butyl Alcohol‐Water Mixtures by a Heterogeneous Azeotropic Batch Distillation Process

Tert‐butyl alcohol and water form an azeotrope at normal pressure. Simple distillation cannot be used to separate these two components. In this article, a systematic study of the separation of tert‐butyl alcohol–water mixtures with an entrainer by heterogeneous azeotropic batch distillation was performed. Based upon the thermodynamic behavior of the ternary mixtures, cyclohexane was chosen as the entrainer. It formed ternary and binary heterogeneous azeotropes with the original components. The process feasibility analysis was validated by using rigorous simulation with chemical process simulation software – HYSYS Plant 2.2 and DISTIL 4.1. Simulation results were then corroborated in a batch experimental column for the selected entrainer.     

Process simulator-based optimization of biorefinery downstream processes under the Generalized Disjunctive Programming framework

Downstream processing of biofuels and bio-based chemicals represents a challenging problem for process synthesis and optimization, due to the intrinsic nonideal thermodynamics of the liquid mixtures derived from the (bio) chemical conversion of biomass. In this work, we propose a new interface between the process simulator PRO/II (SimSci, Schneider-Electric) and the optimization environment of GAMS for the structural and parameter optimization of this type of flowsheets with rigorous and detailed models. The optimization problem is formulated within the Generalized Disjunctive Programming (GDP) framework and the solution of the reformulated MINLP problem is approached with a decomposition strategy based on the Outer-Approximation algorithm, where NLP subproblems are solved with the derivative free optimizer belonging to the BzzMath library, and MILP master problems are solved with CPLEX/GAMS. Several validation examples are proposed spanning from the economic optimization of two different distillation columns, the dewatering task of diluted bio-mixtures, up to the distillation sequencing with simultaneous mixed-integer design of each distillation column for a quaternary mixture in the presence of azeotropes.     

On the Relation between Ideal and Real Mixtures in Multicomponent Distillation

A complete mathematical solution exists for the distillation of ideal multicomponent mixtures, i.e., mixtures with constant relative volatilities, allowing to answer all questions arising in the distillation of such mixtures by relatively simple algebraic equations. As shown in this paper, the distillation of a real mixture of any complexity may – at least qualitatively – be reduced to the distillation of an ideal mixture. The understanding of the distillation behavior of complex real mixtures is thus greatly simplified and useful both in the design as well as the operation of multicomponent distillation columns.     

Azeotropic Binary Solvent Mixtures for Preparation of Organic Single Crystals

Here, a new approach is introduced to prepare large single crystals of π‐conjugated organic molecules from solution. Utilizing the concept of azeotropism, single crystals of tri‐isopropylsilylethynyl pentacene (TIPS‐PEN) with dimensions up to millimeters are facilely self‐assembled from homogeneous solutions comprising two solvents with opposing polarities and a positive azeotropic point. At solvent compositions close to the azeotropic point, an abrupt transition of morphology from polycrystalline thin‐films to large single crystals is found. How to adjust the initial ratio of the binary solvents so that the change in solvent composition during evaporation favors the specific H‐aggregation and promotes an efficient self‐assembly of TIPS‐PEN is explained. The charge‐carrier (hole) mobilities are substantially enhanced by a factor of 4 from the morphology of thin‐films to large single crystals used as active layer in field‐effect transistors. Additionally, this approach is extended to other π–π stacked organic molecules to elucidate its broad applicability.     

High pressure vapor-liquid equilibria of binary system 1,1,1-trifluoroethane (HFC-143a)+propane (HC-290)

Isothermal vapor-liquid equilibrium data were measured for the binary mixture of 1,1,1-trifluoroethane (HFC-143a)+propane (HC-290) at six equally spaced temperatures between 268.15 and 318.15 K by using a circulation-type equilibrium apparatus. The phase composition at equilibrium was measured by gas chromatography. The experimental data were compared with the calculated data based on the Carnahan-Starling-De Santis (CSD) equation of state. Good agreement between experimental and calculated data indicates that the CSD equation of state can be used to estimate thermodynamic properties for the mixture of HFC-143a+propane in the range of temperatures between 268.15 and 318.15 K. The binary system of HFC-143a+propane exhibits azeotropes.     

THE EFFECT OF PRESSURE ON AZEOTROPES

Recently determined electrical conductivities of anodic AgCl, A1C1₃, TiBr₄, and MgCl₂ films are compared to well established conductivities of anodic Ta₂O₅; and A1₂O₃. All of these films exhibit high-field barrier layer condition. The exponential constant, β. is about the same value for the salts as for oxides but the preexponential constants and conductivities are orders of magnitude larger for the salts. The salts, AlCl₃, TiBr₄, and MgCl₂, in addition, have a series ohmic resistance which is attributed to an outer, continuously-forming and dissolving, hydrated salt layer.     

Theoretical Investigations on the Quaternary System n‐Butanol,Butyl Acetate,Acetic Acid and Water

Reactive distillation has been established for different processes, for example, the production of MTBE and TAME. Numerous publications have shown experimental and theoretical results of such etherification processes. The present paper deals with a theoretical background for an esterification process. The investigations will be carried out with the quaternary system consisting of n‐butanol, butyl acetate, acetic acid and water. For this system, not often used in literature, the chemical equilibrium constant and a suitable reaction kinetic has to be found. The different singular points will be checked and the kind of singularity will be determined. Residue curve maps will show the shape of simulations from different starting points. The differences between a simple distillation process and a reactive distillation process will be demonstrated.