Ethanol azeotropic distillation

Absolute Ethanol.. Supplies ot iibsolutc cthnnol, which is frec ucntly required in <>rj> mic chemiciil work, nrc now freely iiwiihible commercially as a result of azeotropic distillation methods. If however it should be... 

The first successful appHcation of heterogeneous azeotropic distillation was in 1902 (87) and involved using benzene to produce absolute alcohol from a binary mixture of ethanol and water. This batch process was patented in 1903 (88) and later converted to a continuous process (89). Good reviews of the early development and widespread appHcation of continuous azeotropic distillation in the prewar chemical industry are available (90). 

Ethanol-water Minimum-hoiling azeotrope Ethylene glycol, acetate salts for salt process Alternative to azeotropic distillation, pressure swing distillation... 

Consider azeotropic distillation to dehydrate ethanol with benzene. Initial steady-state conditions are as shown in Fig. 13-108. The overhead vapor is condensed and cooled to 298 K to form two hquid phases that are separated in the decanter. The organic-rich phase is returned to the top tray as reflux together with a portion of the water-rich phase and makeup benzene. The other portion of the water-rich phase is sent to a stripper to recover organic compounds. Ordinarily, vapor from that stripper is condensed and recycled to the decanter, but that coupling is ignored here. 

FIG. 13-108 Initial steady state for dynamic azeotropic distillation of ethanol-water with benzene. 

Ethanol [64-17-5] M 46.1, b 78.3 , d 0.79360, d 0.78506, n 1.36139, pK 15.93. Usual impurities of fermentation alcohol are fusel oils (mainly higher alcohols, especially pentanols), aldehydes, esters, ketones and water. With synthetic alcohol, likely impurities are water, aldehydes, aliphatic esters, acetone and diethyl ether. Traces of benzene are present in ethanol that has been dehydrated by azeotropic distillation with benzene. Anhydrous ethanol is very hygroscopic. Water (down to 0.05%) can be detected by formation of a voluminous ppte when aluminium ethoxide in benzene is added to a test portion. Rectified... 

The mother liquorsand washings of fractions I and II are concentrated froma volume of about 1.7 liters to 250 ml, the pH is adjusted to 2.5 with 100% formic acid and the solution is stored overnight in a refrigerator, whereby further substance crystallizes. This is filtered off under suction and washed with a small amount of water. The residue on the suction filter is azeotropically distilled with ethanol. There is obtained solid, almost colorless title substance which is denoted as 8. 8 is purer than A according to thin-layer chromatography. 

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. 

Enanthaldehyde, -METHYL-/3-OXO-, DIMETHYL ACETAL, 32, 79 Enanthic acid, e-oxo, 31, 3 Epichlorohydrin, 31, 1 Esterification, by azeotropic distillation with toluene, 30, 30, 31 of ethanol with phosphorus trichloride, 31, 111... 

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

The ethanol-water azeotrope (95%ethanol-5%water) is an example of a minimum boiling azeotrope. Its boiling point is lower than that of the components (Fig. 143). If you ve ever fermented anything and distilled the results in the hopes of obtaining 200 proof (100%) white lightning, you d have to content yourself with getting the azeotropic 190 proof mixture, instead. Fermentation usually stops when the yeast die in their own 15% ethanol solution. At room temperature, this is point A on our phase diagram. When you heat the... 

Figure 11.44. Azeotropic distillation for the separation of ethanol from water using benzene as entrainer. Compositions are given in mole per cent. E = Ethanol, B = Benzene, W = Water, S = Steam...

Figure 11.45. Composition profile for the azeotropic distillation of ethanol and water, with benzene as entrainer...

Norman, W. S. Trans. Inst. Chem. Eng. 23 (1945) 66. The dehydration of ethanol by azeotropic distillation. Ibid. 89. Design calculations for azeotropic dehydration columns. 

Highest yields are obtained when the reaction is carried out in boiling toluene until all water and ethanol are eliminated by azeotropic distillation. Other /S-ketocarboxylic esters such as ethyl benzoyl acetate, o-methoxybenzoyl acetate and ethyl acetonedicarboxylate react similarly with aromatic amidoximes (50). 

A 4-arm polyethylene glycol having an Mn of 10,000 Da (8 mmol of hydroxyl groups) was dried by azeotropic distillation using 400 ml of chloroform. The residue was then redissolved in 300 ml chloroform and cooled to 4°C and then treated with triethylamine (14.4 mmol) and methanesulfonyl chloride (13.2 mmol). The mixture was stirred overnight at ambient temperature and then treated with 5 ml of ethanol and stirred an additional 30 minutes. It was dried using sodium carbonate (10.0 g), concentrated, and filtered. The filtrate was concentrated to dryness and treated with 400 ml of 2-propanol. The precipitate was collected and 20.0 g product isolated having a 95.3% methanesulfonate substitution. 

The step 2 product (2.0 mmol) was dried by azeotropic distillation, redissolved in 80 ml ethanol, and treated with the step 1 product (7.2 mmol). The mixture was... 

Ethanol forms an azeotrope containing 5 wt % water. In older installations, dissolved salts were employed to break the azeotrope. Typical data are in Figure 13.28(c). Several substances form ternary azeotropes with ethanol and water, including benzene, gasoline, and trichlorethylene. The first is not satisfactory because of slight decomposition under distillation conditions. A flowsketeh of a... 

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