Article

The Separation of Acetone-Methanol Mixture by Extractive Distillation

Chemical Engineering Communications (Impact Factor: 1.1). 06/1988; 68(1):69-79. DOI: 10.1080/00986448808940398

ABSTRACT

Acetone and methanol can not be readily separated by ordinary distillation because of the presence of the minimum boiling azeotrope. Either acetone or methanol can be the overhead product when an appropriate agent is applied in extractive distillation. An unusual phenomenon, “temperature inversion”, was observed when ketones were used as the extractive distillation agents. The dissolving of the vapors into the liquid phase could be the cause for the overhead at a temperature higher than that of the stillpot.

    • "In the case of ED, efficient separation is strongly influenced by the choice of a more efficient entrainer. Individual (one compound) and mixed (two or more substances) entrainers can be used (Berg & Yeh, 1984; Berg et al., 1985, 1988, 1990). Mixed entrainers can be used for maintaining the moderate temperatures in the ED column (Liao et al., 2001), decreasing the viscosity (Gil et al., 2014) and solubility for inhibiting adverse reactions, etc. "
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    ABSTRACT: The separation of two systems containing minimum boiling azeotropes (acetone-methanol and tetrahydrofuran (THF)-water) was performed using extractive distillation with a heavy boiling mixed entrainer consisting of two compounds. The entrainer constituents did not form new azeotropes with each other and with the components of the original mixture. An analysis of the mixed entrainer influence on the vapor-liquid equilibrium (VLE) and relative volatility provides an understanding of the cases in which the separation by extractive distillation (ED) in the presence of the mixed entrainer revealed energy benefits over their individual constituents. New results for application of the mixed entrainer monoethanolamine (MEA)-ethylene glycol (EG) and dimethylsulphoxide (DMSO)-glycerol for the separation of THF-water and acetone-methanol, respectively, are presented for the first time. The individual selective agents were chosen from the efficient entrainers discussed in the literature. The calculations were performed using the platform Aspen Plus 7.3. Different extractive distillation flowsheets are provided for the zeotropic mixed agents, viz. with two or three columns. For the ED of the binary mixtures investigated, the structures of the different separation schemes, the operating parameters of the columns, and the energy consumptions are presented and compared. The application of the mixed entrainer MEA-EG fed into the ED column with pre-mixing can be recommended, providing up to 1.7 % of energy saving for acetone-methanol separation. In the case of THF-water, the mixed entrainer DMSO-glycerol provides 0.8 % of energy saving. The separate inputs of the individual constituents of the mixed entrainer led to a significant increase in the energy consumptions of the flowsheet because of the third regeneration column, hence this flowsheet cannot be recommended for use in the separation of both mixtures.
    No preview · Article · Jan 2015 · Chemical Papers- Slovak Academy of Sciences
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    ABSTRACT: In addition to a minimum reflux, every extractive distillation exhibits a maximum reflux, above which the desired separation is impossible, and a minimum entrainer flow rate, below which the separation is also impossible. Both of these quantities correspond to bifurcations of the finite difference equations describing the middle section of the column and, given a VLE model, can be easily calculated knowing only information about the column feed and the desired product compositions, that is, prior to any column design calculations. Both maximum reflux and minimum entrainer flows have important implications for the design and operation of extractive distillations. By limiting the range of feasible operating reflux ratios, the maximum reflux affects the flexibility, operability and controllability of the column. Ranking a set of feasible extractive entrainers according to their minimum entrainer flows provides a simple effective method for identifying the most promising candidates. Near optimal design values of the entrainer flow can then be estimated using the heuristic presented.
    No preview · Article · Feb 1994 · AIChE Journal

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