Ethanol binary azeotropes with

The quantity of hexane necessary to entrain water, methanol, ethanol, acetone, and acetaldehyde dimethyl acetal to the top was estimated as the sum of the hexane quantities required to form the binary azeotropes with the quantities of water, methanol, ethanol, acetone, and acetaldehyde dimethyl acetal in the mixture. 

Liquid with pungent odor. bp7 81.4. tig 1.4086. dj 0.8636 dj5 0 8407. Easily soluble in water, methanol, ethanol, ether, acetone, glacial acetic acid. Slightly sol in hydrocarbons. Forms a binary azeotrope with water, bp 75 (12% water), uv spectrum and electric moments Rogers, J. Am. Chem. Soc. 69, 2544 (1947). Polymerizes on standing, LDm in mioe and rats 35 mg/kg, C.A. 72, 124809b 0970). 

Many investigations of the extraction of ethanol from water have postulated that a very high selectivity is needed to enrich the solvent-free extract to an ethanol content near or above the binary azeotrope with water. However, this degree of enrichment is not necessary. The extraction step can be followed by an extractive-distillation dewatering step similar to the process shown for acetic acid recovery in Fig. 15.2-3. 

However, there is a problem. Water and ethanol form an azeotrope, as mentioned before, but benzene also forms a binary azeotrope with ethanol. The benzene-ethanol binary azeotrope boils at 67.8°C and consists of 67.6% benzene and 32.4% ethanol. This means that as the benzene-water azeotrope is distilled, ethanol is also removed. An excess of ethanol is therefore essential. 

Water is the most common azeotropic component In the bible of azeotropic information, the reference given in Ref. 3, Appendix 2, there are 64 pages devoted to lists of binary azeotropes with water Each page has approximately 50 entries of different azeotropes with water as one component. For comparison, there are 30, 35, 10, and 13 pages for methanol, ethanol, n-propanol, and isopropanol, respectively... 

The emerging biofuel processes typically have fermentation products that form azeotropes with flie water, which is present in large excess in the fermentor. The most important example is ethanol, which forms a minimum-boiling homogeneous binary azeotrope with water. Butanol is anoflier biofuel example that forms an azeotrope with water. The nonideality in this system is so large that the azeotrope is heterogeneous, forming two liquid phases. 

Ethanol prepared by distillation is only about 96% pure because it forms a low-boiling binary azeotrope with water. "100%" ethanol can be made by adding a specific amount of benzene to form a ternary azeotrope that boils at 54.9°C. However, this ethanol should not be ingested Why ... 

The azeotrope in the ethanol-water binary system has a composition of 89 mole per cent of ethanol(14). Starting with a mixture containing a lower proportion of ethanol, it is not possible to obtain a product richer in ethanol than this by normal binary distillation. Near azeotropic conditions exist at points marked in Figure 11.44. The addition of the relatively non-polar benzene entrainer serves to volatilise water, a highly polar molecule,... 

B. Ethyl a-(bromomethyl)acry late. In a nitrogen-flushed, 1-L, round-bottomed flask equipped with a magnetic stirrer, Dean-Stark trap, and condenser are placed 42.0 g (0.25 mol) of a-(bromomethyl)acrylic acid and 300 mL of benzene. Approximately 50 mL of a binary azeotrope of benzene and water is distilled (Note 7). The Dean-Stark trap is removed and 100 mL of absolute ethanol (Note 8) and 1 mL of concentrated sulfuric acid are added slowly. The contents of the flask are boiled in a nitrogen atmosphere for 36 hr, the condensate being passed through 100 g of molecular sieves (Linde 3A) before being returned to the flask. About 125 mL of a mixture of benzene and ethanol is removed from the reaction... 

By far, the most common prejudice (sometimes completely overlooking the other alternative) is to propose the most volatile composition (low-boiling node) as distillate (Fig. 28). In this region containing the decant aqueous layer, the lightest composition is the ternary azeotrope. With enough stages, all of the azeotropic composition in the decant aqueous layer may be recovered, and the underflow will contain only a binary ethanol-water mixture. If the distillate of... 

MgS04, CaO, K2CO3, Ca or solid NaOH, followed by refluxing with, and distn from, calcium, magnesium activated with iodine, aluminium amalgam or sodium. Can also dry with molecular sieves, or by refluxing with n-butyl phthalate or succinate. (For method, see Ethanol.) n-Butanol can also be dried by efficient fractional distn, water passing over in the first fractn as a binary azeotrope (contains about 37% water). An ultraviolet-... 

An example of azeotropic distillation is the use of benzene to permit the complete separation of ethanol and water, which forms a minimum-boiling azeotrope with 95.6 weight percent alcohol. The alcohol-water mixture with about 95 percent alcohol is fed to the azeotropic distillation column with a benzene-rich stream added at the top. The bottom product is nearly pure alcohol, and the overhead vapor is a ternary azeotrope. The overhead vapor is condensed and separated into two phases. The organic layer is refluxed, and the water layer is sent to a benzene recovery column. All the benzene and some alcohol is taken overhead and sent back to the first column, and the bottoms stream is distilled in a third column to give pure water and some of the binary azeotrope. 

Whether an azeotrope is a binary or a ternary it is desirable that it should be fractionated easily from the other component(s) of the system. In the absence of vapour/liquid data the boiling point gap is the best indication of how easy the split is. The comparative complexity of the column contents can be illustrated by the ethanol/water system with cyclohexane added as a dewatering entrainer (Table 7.5). 

In a situation in which fractionating power is known to be barely adequate, the two solvents (DIPE and chloroform) with low-boiling binary azeotropes including water rather than ethanol have the advantage that it is positively helpful to have their water binaries admixed with the ternary in the decanter (Table 7.6). 

The boiling points of the pure components at atmospheric pressure are as follows ethyl acetate (ETAC) 77.2 C ethanol (ETOH) 78.3 C water (H20) 100.0 C acetic acid (HAG) 118.0 G. There are three binary azeotropes and one ternary azeotrope summarized in Table 10.2, with respective boiling points at atmospheric pressure. The normal boiling points for the pure components as well as the compositions of the azeotropes are obtained from ASPEN Properties Plus using UNIQUAG and show satisfactory agreement with the data available elsewhere [105]. 

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