Azeotropic distillation minimum

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

Levy SG, Van Dongen DB and Doherty MF (1985) Design and Synthesis of Homogeneous Azeotropic Distillation 2. Minimum Reflux Calculations for Non-ideal and Azeotropic Columns, Ind Eng Chem Fund, 24 463. 

An important topic in azeotropic distillation regards the purity. This can be managed by means of both entrainer and reflux ratios. For a given purity there is a minimum entrainer ratio that can be determined from a RCM plot. In... 

A weighed amount of lignin is acetylated overnight at room temperature with a mixture of purified pyridine-acetic anhydride (1 1, v/v). Excess acetic anhydride is decomposed by the addition of methanol-ice water. After evaporation of the mixture to dryness, the residue is suspended in toluene and again evaporated (repeated three times). In this process, the remaining traces of acetylation mixture are removed by azeotropic distillation. Subsequently, the toluene can be removed by addition of methanol and evaporation. This method allows complete recovery of the sample with a minimum of added impurities. 

Ethanol-water Minimum-boiling azeotrope None Alternative to extractive distillation, salt extractive distillation, heterogeneous azeotropic distillation must reduce pressure to less than 11.5 kPa for azeotrope to disappear... 

A second example of the use of liquid-liquid immiscibilities in an azeotropic distillation sequence is the separation of the ethanol-water minimum-boiling homogeneous azeotrope. For this separation, a number of entrainers have been proposed, which are usually chosen to be immiscible with water and form a ternary minimum-boiling... 

The first step in testing the material for suitability of the demulsify-ing, dehydrating process is to dilute the crude oil with a solvent which is used by itself or mixed with another in azeotropic dehydration of the emulsion. The minimum amount of solvent which is sufficient for the first step is that which cuts the viscosity of the crude enough to allow azeotropic distillation without excessive foaming. This may require about 40-60 volumes solvent per 100 volumes of crude, but this ratio of solvent, however, may not be sufficient to reduce the gravity of the crude below that of water to allow preliminary decantation of some of the water. 

The boiling points of benzene and cyclohexane are 80.1 °C and 80.8°C, respectively, and they form a minimum boiling azeotrope at 100 kPa, 77°C, and 54 mole% benzene. It is proposed to separate them by adding acetone as an entrainer, which forms a minimum boiling azeotrope with cyclohexane at 100 kPa, 53°C, 73.9 mole% acetone and 25.1 mole% cyclohexane. The azeotrope is taken as the overhead stream in a distillation column, and the benzene is recovered as the bottoms product. Further processing will be used to separate the cyclohexane and acetone in the azeotrope distillate. 

Benzene and cyclohexane are separated by azeotropic distillation using acetone as an entrainer. At the column pressure of 1 atm, acetone forms a minimum boiling azeotrope with cyclohexane at 74.6 mole% acetone and 25.4 mole% cyclohexane. The feed contains 75 kmol/h benzene and 25 kmol/h cyclohexane. The entrainer, pure acetone, is mixed with the feed and sent to the column. The distillate is 99.5 mole% azeotrope and 0.5 mole% benzene. The bottoms is 99 mole% benzene and 1 mole% cyclohexane. Determine the entrainer flow rate. 

Anhydrous p-toluenesulfonic acid was prepared from the monohydrate (obtained from Aldrich Chemical Company, Inc.) by solution in hot benzene with the aid of ethyl acetate and azeotropic distillation to 50% volume to remove water. The solution was then concentrated to a syrup on a rotary evaporator. The syrup was dissolved in a minimum volume of acetone and excess benzene was added to... 

If a mixture of ethanol and water is distilled, eventually it will form a solution that is 95 % ethanol regardless of the starting composition. Hydrochloric acid and water will form a 20.22 % HCl solution, and chloroform and acetone will form a 65.5 % CHCI, solution. These solutions are called azeotropes (Gr a + zeo to boil, trope more at). Webster s dictionary defines an azeotrope as a liquid mixture that is characterized by a constant maximum or minimum boiling point which is lower or higher than that of any of the components and that distills without change in composition. An azeotropic distillation involves the formation of an azeotrope with at least one of the components of a liquid mixture, which then can be separated more readily because of the resulting increase in the difference between the volatilities of the components of the mixture. Figure 4-1, p. 44, shows the water-ethanol system (A) and the HCl-water system (B). 

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. 

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