http://www.nt.ntnu.no/users/skoge/publications/2003/azeotrope_survey_kiva_ces/submitted_version/uncorrected_proof.pdf

Azeotropic phase equilibrium diagrams: a survey

The separation of ternary nonideal systems with multi‐azeotrope is very important because they are often found in the waste of chemical and pharmaceutical industries, which is much more difficult due to the formation of multi‐azeotrope and distillation boundary. We propose a systematic procedure for design and control of a triple‐column pressure‐swing distillation for separating ternary systems with three binary minimum azeotropes. This procedure involves thermodynamic insights, a two‐step optimization method, and effective control strategy. The separation of tetrahydrofuran (THF)/ethanol/water is used to illustrate the capability of the proposed procedure. It is found that the pressure limits in columns can be determined through the analysis of residue curve maps, distillation boundary, and isovolatility curves. The optimal triple‐column pressure‐swing distillation is generated with the minimum total annual cost (TAC) of $2.181 × 106 in sequence A. The operating conditions are well controlled approaching their desired specifications in an acceptable time when disturbances occur.

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Design and control of pressure-swing distillation for separating ternary systems with three binary minimum azeotropes

Extractive distillation processes enable the separation of non-ideal mixtures, including minimum or maximum boiling azeotropes and low relative volatility mixtures. Unlike azeotropic distillation, the entrainer fed at another location than the main mixture induces an extractive section within the column. A general feasibility criterion shows that intermediate and light entrainers and heterogeneous entrainers are suitable along common heavy entrainers. Entrainer selection rules rely upon selectivity ratios and residue curve map (rcm) topology including univolatility curves. For each type of entrainer, we define extractive separation classes that summarize feasibility regions, achievable products and entrainer – feed flow rate ratio limits. Case studies are listed as supplementary materials. Depending on the separation class, a direct or an indirect split column configuration will allow to obtain a distillate product or a bottom product, which is usually a saddle point of rcm. Batch and continuous process operations differ mainly by the feasible ranges for the entrainer – feed flow rate ratio and reflux ratio. The batch process is feasible under total reflux and can orient the still path by changing the reflux policy. Optimisation of the extractive process must systematically consider the extractive column along with the entrainer regeneration column that requires energy and may limit the product purity in the extractive column through recycle. For the sake of reducing the energy cost and the total cost, pressure change can be beneficial as it affects volatility, or new process structures can be devised, namely heat integrated extractive distillation, extractive divided wall column or processes with preconcentrator.

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Review of Extractive Distillation. Process design, operation optimization and control

▪ Abstract This review discusses the preparation, characterization, and application of amorphous porous mixed oxides, a rapidly growing class of materials with wide applications and a huge potential for the tailoring of chemical composition, microstructure, porosity, and surface properties. In contrast to crystalline materials, these amorphous mixed oxides are prepared under mild reaction conditions in ambient atmosphere. An ever-increasing variety of precursors, additives, modifiers, solvents, catalysts, and posttreatment conditions provide ample fine-tuning options. These materials often display properties commonly associated with well-defined crystalline phases. The functional properties of such solids are largely unexplored and provide a tremendous opportunity for the development of new or alternative materials (solids with a function). Here, emphasis is paid to micro- and mesoporous mixed oxides and their catalytic properties. Easy access to these materials is offset by their much more problematic ch...

AMORPHOUS POROUS MIXED OXIDES: Sol-Gel Ways to a Highly Versatile Class of Materials and Catalysts

Extractive distillation is one of the most attractive approaches for separating azeotropic mixtures. Few contributions have been reported to design an extractive distillation for separating maximum-boiling azeotropes and no systematic approaches for entrainer screening have been presented. A systematic approach to design of two-column extractive distillation for separating azeotropes with heavy entrainers has been proposed. A thermodynamic feasibility analysis for azeotropes with potential heavy entrainers was first conducted. Then, five important properties are selected for entrainer evaluation. Fuzzy logic and develop membership functions to calculate attribute values of selected properties have been used. An overall indicator for entrainer evaluation is proposed and a ranking list is generated. Finally, the top five entrainers from the ranking list have been selected and use process optimization techniques to further evaluate selected entrainers and generate an optimal design. The capability of the proposed method is illustrated using the separation of acetone–chloroform azeotropes with five potential entrainers.

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Systematic design of an extractive distillation for maximum‐boiling azeotropes with heavy entrainers

The classification of ternary vapor-liquid equilibrium (VLE) diagrams is a key to simple azeotropic distillation analysis. All ternary mixtures reported so far to be occurring in nature can be qualitatively represented by a combination of only four elementary cells. This greatly reduces the number of VLE diagram structures that need to be analyzed in order to reveal the qualitative characteristics of any ternary azeotropic mixture.

Topology of ternary VLE diagrams: Elementary cells

Analysis of closed multivessel batch distillation of ternary azeotropic mixtures using elementary VLE cells

An analysis of the structural properties of vapor–liquid equilibrium (VLE) diagrams provides a fundamental understanding of the thermodynamic behavior of azeotropic mixtures upon distillation. In addition to a review of well-known fundamental work on the analysis of VLE diagrams, this survey comprises less-known published results, especially from the Russian literature. Some new results are also presented for the 6rst time. ? 2003 Elsevier Science Ltd. All rights reserved.

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E. K. Hilmen

Papers

Azeotropic phase equilibrium diagrams: a survey

Topology of ternary VLE diagrams: Elementary cells

Analysis of closed multivessel batch distillation of ternary azeotropic mixtures using elementary VLE cells

Review Azeotropic phase equilibrium diagrams: a survey