Ethanol/water separation distillation

Ethanol/water separation distillation. 387, 394, 424 reverse osmosis, 642 Ethylene... 

ETBE is recovered as the bottoms product of the distillation unit. The ethanol-rich C4 distillate is sent to the ethanol recovery section. Water is used to extract excess ethanol and recycle it back to process. At the top of the ethanol/water separation column, an ethanol/water azeotrope is recycled to the reactor section. The isobutene-depleted C4 stream may be sent to a raffinate stripper or to a molsieve-based unit to remove oxygenates such as DEE, ETBE, ethanol and tert-butanol. 

Ethanol produced by fermentation is conventionally dehydrated by distillation, an inefficient process that consumes energy equivalent to a large fraction of the energy content of the product ethanol.(X) Reverse osmosis (RO) has been considered before for ethanol-water separation because of its inherent energy efficiency. However, a difficulty encountered in using RO is the high osmotic pressures associated with concentrated ethanol solutions. For example, the osmotic pressure of a 15-volX ethanol solution is about 960 psi, and that of a 50-volX solution is about 3700 psi.(2,) Because most... 

The first commercial application of pervaporation was for ethanol-water separation. The dilute solution produced by fermentation is distilled to produce an overhead product with 90 to 95 percent alcohol (close to the azeotrope), and this solution is fed to the membrane unit to give nearly pure ethanol (99.9 percent). The permeate stream with about 20 to 40 percent alcohol is recyled to the distillation column. The vapor-liquid equilibrium curve and the vapor and liquid compositions for a poly(vinyl alcohol) membrane are shown in Fig. 26.16. The membrane gives a permeate that is always richer in water than the liquid, in contrast to distillation, where alcohol is the more volatile component over most of the range. The shape of the curve for permeate composition indicates strongly... 

Figure 2.11 Comparison of the primary energy usage for ethanol/water separation using traditionai distillation/adsorption process (Fig. 2.9) and hybrid membrane-assisted vapor stripping (MAVS Fig. 2.10) process. Minimum energy (from minimum work calculation) shown as reference. Assumptions 37% and 85% efficient conversion of primary energy to electrical energy and thermal energy, respectively, 0.02 wt% ethanol in stripping column bottoms, and 99.5 wt% ethanol product (0.5 wt% water).

If a desired ethanol-water separation by distillation requires a minimum of 17 theoretical stages at total reflux, how many theoretical stages would be recommended for a first-pass design of a plant column using a computer simulation ... 

Vane, L. M., Alvarez, F. R., Huang, Y., Baker, R. W. (2009). Experimental vahdation of hybrid distillation-vapor permeation process for energy efficient ethanol-water separation. Journal of Chemical Technology and Biotechnology, 85, 502—511. 

In the same extractive distillation category, recent research developments have shown that it is possible to use nonvolatile hyperbranched polymers or ionic liquid as entrainers in the extractive distillation process. An example in the literature (Seiler et al." ) is for ethanol-water separation using hyperbranched polyglycerol or ionic liquid like [EMIM] [BF4] as entrai-ner. Because the entrainer is nonvolatile, the recovery of entrainer is much easier than saline extractive distillation. 

Many papers point out the economic advantages of pervaporation over conventional processes. A quantitative economic comparison between azeotropic distillation and hybrid column-pervaporation is presented by Guerreri," whose results show higher capital cost but much lower energy cost for the ethanol-water separation. A review of industrial applications of pervaporation, coupled with either distillation columns or chemical reactors, is... 

Franken, A. C. M., Nolten, J. A. M., Mulder, M. H. V., and Smolders, C. A. (1987a). Ethanol-water separation by membrane distillation Effect of temperature polarization. In B. Sedlacek and J. Kahovec (Eds.) Synthetic Polymeric Membranes, Walter de Gruyter, Berlin, p. 531. 

The diethyl fumarate is readily prepared as follows. Reflux a mixture of 146 g. of fumaric acid (Section 111,143), 185 g. (236 ml.) of absolute ethanol, 450 ml. of boizene and 20 g. of concentrated sulphuric acid for 12 hours. Pour into a large volume of water, separate the benzene layer, wash successively with water, saturated lodium bicarbonate solution and water, dry with anhydrous magnesium sulphate, and remove the solvent on a steam bath. Distil the residue and collect the diethyl fumarate at 213-215° the yield is 150 g. 

Fig. 18. Separation of ethanol from an ethanol—water—benzene mixture using benzene as the entrainer. (a) Schematic representation of the azeo-column (b) material balance lines where I denotes the homogeneous and the heterogeneous azeotropes D, the end points of the Hquid tie-line and A, the overhead vapor leaving the top of the column. The distillate regions, I, II, and III, and the boundaries are marked. Other terms are defined in text.

Fig. 19. Separation of ethanol and water from an ethanol—water—benzene mixture. Bottoms and are water, B is ethanol, (a) Kubierschky three-column sequence where columns 1, 2, and 3 represent the preconcentration, azeotropic, and entrainer recovery columns, respectively, (b) Material balance lines from the azeotropic and the entrainer recovery columns, A and E, respectively, where represents the overall vapor composition from the azeo-column, 2 1SP Hquid in equiUbrium with overhead vapor composition from the azeo-column, Xj, distillate composition from entrainer...

Wines and other alcoholic beverages such as distillates represent very complex mixtures of aromatic compounds in an ethanol-water mixture. Once an extract or concentrate of the required compounds is prepared, a suitable chromatographic system must be used to allow separation and resolution of the species of interest. Many applications have been developed that use MDGC. 

Water and ethanol form a low boiling point azeotrope. So, water cannot be completely separated from ethanol by straight distillation. To produce absolute (100 per cent) ethanol it is necessary to add an entraining agent to break the azeotrope. Benzene is an effective entrainer and is used where the product is not required for food products. Three columns are used in the benzene process. Column 1. This column separates the ethanol from the water. The bottom product is essentially pure ethanol. The water in the feed is carried overhead as the ternary azeotrope of ethanol, benzene and water (24 per cent ethanol, 54 per cent benzene, 22 per cent water). The overhead vapour is condensed and the condensate separated in a decanter into, a benzene-rich phase (22 per cent ethanol, 74 per cent benzene, 4 per cent water) and a water-rich phase (35 per cent ethanol, 4 per cent benzene, 61 per cent water). The benzene-rich phase is recycled to the column as reflux. A benzene make-up stream is added to the reflux to make good any loss of benzene from the process. The water-rich phase is fed to the second column. 

Figure 12.22 Distillation sequence for the separation of an ethanol-water mixture using ethylene glycol as entrainer is infeasible using single-feed column.

Keyes A process for separating water from ethanol, using azeotropic distillation with benzene. Invented in 1922 by D. B. Keyes. 

Add with stirring 22.5 g S0C12 in 100 ml ether in 20 ml portions to a solution of 15 g 3,5-dimethoxybenzyl alcohol, 1 ml pyridine and 200 ml ether. Let stand and wash with 2X100 ml cold water separate and dry, evaporate in vacuum the ether to get 16 g 3,5-dimethoxybenzyl chloride (I). Recrystallize from petroleum ether. 16 g (I), 300 ml ethanol, 30 g NaCN, 75 ml water reflux three hours and pour onto 400 g ice. After ice melts, filter and recrystallize precipitate from petroleum ether to get about 14 g 3,5-dimethoxybenzyl CN (II). 5 g 50% NaH in mineral oil wash three times with pentane or hexane fill flask with N2 or argon and add dimethoxyethane or dimethylformamide (freshly distilled from K if possible). Stir and add 9 ml methyl iodide. Carefully add 8 g (II) and stir twelve hours. Add ice water and neutralize with NaHC03 to pH 7-8. Extract with ether and dry, evaporate in vacuum the ether (can distill 170/0.1) to get about 9 g alpha, alpha-dimethyl-3,5-... 

If, for example, a mixture of ethanol and water is distilled, the concentration of the alcohol steadily increases until it reaches 96 per cent by mass, when the composition of the vapour equals that of the liquid, and no further enrichment occurs. This mixture is called an azeotrope, and it cannot be separated by straightforward distillation. Such a condition is shown in the y — x curves of Fig. 11.4 where it is seen that the equilibrium curve crosses the diagonal, indicating the existence of an azeotrope. A large number of azeotropic mixtures have been found, some of which are of great industrial importance, such as water-nitric acid, water-hydrochloric acid, and water-alcohols. The problem of non-ideality is discussed in Section 11.2.4 where the determination of the equilibrium data is considered. When the activity coefficient is greater than unity, giving a positive deviation from Raoult s law, the molecules of the components in the system repel each... 

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