The method of purifying ethyl alcohol

 

(57) Abstract:

Use: in the production of aliphatic alcohols in particular in the method of purification of ethanol. The inventive product is ethanol, BF C2H6O the content of carbonyl impurities 1 to 4.5 mg/l reaction Conditions: purification of ethanol are processing its hydrocyclon alkali metal and sodium borohydride, taken in an amount of 0.01 to 0.1 and 0.005 to 0.3 wt. accordingly, 1 Il. table 1.

The invention relates to a method of purification of ethanol from carbonyl impurities by treating it with a chemical reagent, rectification and can be used in the production of ethyl alcohol and in the processes of organic synthesis using ethyl alcohol.

Currently, the domestic industry of ethyl alcohol is produced by fermentation of food raw materials, hydrolysis of plant materials, direct hydration of ethylene in the presence of acid catalysts. In all cases, at the stage of synthesis of the target product are formed such side products, such as aldehydes (carbonyl compounds), higher alcohols, with the most contaminated aqueous-alcoholic raw is formed by synthetic ethyl spyrestudios technological scheme and this, along with the purified ethyl alcohol are formed contaminated with aldehydes and other impurities alcoholic solutions, which result in losses of the target product, and the selection of the target product from them effectively can be chemical or adsorption methods. The most difficult is the process of separating the purified ethyl alcohol from water and raw alcohol formed during the direct hydration of ethylene, which, along with the target product contains a number of carbonyl compounds with a wide limit of the boiling points acetaldehyde, acetone, propionic aldehyde, methyl ethyl ketone, CROTONALDEHYDE and other Synthetic ethyl alcohol, manufactured now on THE 38.402-62-117-90 and containing in their structure a wide range of carbonyl compounds, is widely used in the processes of organic synthesis, thus there is often the need for cleaning of the product from the carbonyl impurities.

The most known method of purification of ethanol from organic impurities, including aldehydes, ketones, is the method of cleaning, comprising the stage of dilution of the concentrated ethyl alcohol and water passing through the layer of activated carbon [1] Usually this method is used for the purification of ethanol from the concentration of the cleaning heavily soiled product due to the low sorption capacity of coal and selective absorption of impurities, this method is inefficient, includes stage dilute the alcohol with water, and subsequent concentration of alcohol, which leads to the complexity of the technological scheme, the formation of polluted water and waste coal.

Closest to the present invention is a method of purifying ethyl alcohol from aldehyde impurities, mainly from acetaldehyde by alcohol treatment at the stage of distillation of the aqueous solution of alkali metal hydroxide [2] According to the described method, the process of separating ethanol from water-ethanol raw material containing 0,16-0,19 wt. acetaldehyde, carry out multi-stage scheme, which includes the pre-distillation of the lung and the main quantity of aldehydes in the extractive-distillation column, with further diluted to 5.0-10.0 wt. an aqueous solution of ethyl alcohol in the column concentration of allocation of purified ethyl alcohol, at the same time to ensure a high degree of purity of the alcohol in the middle part of the column serves aqueous solution of alkali metal hydroxide. The highest degree of purity alcohol (content of acetaldehyde below 2.0 mg/l) is achieved when the concentration of alkali metal hydroxide in Cuba what about the metal for the chemical binding of acetaldehyde, i.e., a hydroxide of alkaline metal cleaning processes ethyl alcohol is used only for partial binding of acetaldehyde, and the inability to use this method for the purification of alcohol from other carbonyl compounds.

The process of purification of ethyl alcohol by treating the alcohol with a mixture of alkali metal hydroxide, taken in an amount of 0.01-0.1 wt. and sodium borohydride in an amount of 0.005 to 0.3 wt. when 30-80aboutWith allows you to get ethyl alcohol of high purity. This method can be effectively used for cleaning contaminated carbonyl compounds concentrated ethyl alcohol by preprocessing the dirty product specified reagents followed by separation of the alcohol by distillation.

The upper limit of the concentration of the reagents is limited by the fact that a further increase of hydroxide of an alkali metal higher than 0.1 wt. and sodium borohydride above 0.3 wt. along with providing high purity alcohol only lead to increased consumption of reagents and increasing losses of ethanol on the stage of rectification.

The drawing shows a diagram of the proposed installation.

Evaluation of the effectiveness DSA the tank 2 for storing contaminated ethyl alcohol, capacity 4 to prepare an aqueous solution of alkali metal hydroxide and sodium borohydride, dosing pumps 3 and 5, the heater 6, distillation column 10, the refrigerator 11, reservoir 12, 13 for collecting the purified ethyl alcohol, the pump 14 for pumping a bottom liquid 15; 1 line input ethyl alcohol, 7, 8, 9 line input of an aqueous solution of alkali metal hydroxide and sodium borohydride.

The total content of carbonyl compounds in the source of ethyl alcohol was determined by chromatographic specifications 38.402-62-117-90 using a flame ionization detector. Sorbent diglycerin and polietilenglikolsuktsinata on chromatone, the column length was 3 m, the velocity of the carrier gas 25-30 cm3/min, the temperature of thermostat 55-65aboutWith the temperature of the evaporator 50aboutC. the Content of carbonyl compounds in terms of acetic aldehyde in a purified ethanol depending on their concentration was determined analogizes according to GOST 10749.3-80 and GOST 5964-82.

P R I m e R 1 (comparative). Clearing of carbonyl impurities is subjected to synthetic ethyl alcohol conforming to the requirements of THE 38.402-62-117-90 and containing in its composition of 0.14 wt. acetaldehyde, a 0.012 wt. methyl ethyl ketone, 0,009 wt. acetone, 0 prepare a 5.0% solution of sodium hydroxide by filing a 20% aqueous NaOH solution and distilled water. The contaminated alcohol from the tank 2 by the pump 3 with a flow rate of 0.2 l/h is fed through the heater 6 in rectification column. The average length of stay alcohol-flow heater 6 is 1 o'clock Constantly in the contaminated alcohol dosed at 5.0% aqueous sodium hydroxide solution by feeding it the pump 5 to the suction side of pump 3. The consumption of alkali is about 4.0 to 4.5 ml/h and provides the content of sodium hydroxide in an alcohol thread about 0,10-0,12 wt. (analysis of the sampler 16).

In the heater 6 liquid stream is heated to 70aboutAnd then enters the distillation column 10 of the Packed type (column filled with a nozzle made of spiral size 2,h,0 mm). Modes of rectification of ethanol following: temperature of top 78,0-78,4aboutTemperatures cube 91-93aboutWith, reflux number of 6.0. CBM product from the column output periodically by the pump 14.

Test this mode should be performed within 10 hours as a result providing 1850 purified ethanol: volume fraction of ethyl alcohol to 96.3% of the total carbonyl content in terms of acetic aldehyde 158 mg/l

P R I m m e R 2 (comparative). The cleaning process is carried out in the conditions of example 1. Consumption of alcohol 0.2 l/h, GI is from the pump 3. In the heater 6 liquid stream is heated to 70aboutWith, time 1 h

The test results for 10 h emit 1822 alcohol with the following characteristics: volume fraction of ethyl alcohol 96,2% of the total carbonyl content in terms of acetic aldehyde 204 mg/l

P R I m e R 3. Cleaning is subjected to synthetic ethyl alcohol of example 1 and test conditions similar to examples 1 and 2. In the vessel 4 is prepared aqueous solution of sodium hydroxide and sodium borohydride containing 2.0 wt. sodium hydroxide and 4.0 wt. sodium borohydride. The resulting solution with a flow rate of 5 cm3/h pump 5 is supplied to the suction side of the pump 3. Consumption of alcohol flow rate of 0.2 l/H. the Content of sodium hydroxide in ethanol stream is 0.05-0.06 wt. and sodium borohydride 0,10-0,12 wt. liquid flow in the heater 6 is heated to 70aboutC. the result of this mode is selected 1836 purified ethyl alcohol with the following characteristics: volume fraction of ethyl alcohol to 96.3% of the total carbonyl content of impurities in terms of acetic aldehyde 1.5 mg/l

P R I m e R s 4-12. The cleaning process ethanol is conducted similarly to examples 1-3. During the tests varied the heater 6 in the range of 30-70aboutC.

The test conditions and the results obtained are presented in the table.

A comparative analysis of the results shows that the process of purification of ethyl alcohol by pre-treatment with a mixture of alkali metal hydroxide and sodium borohydride, taken in an amount of 0.01-0.1 and 0.005-0.3 wt. at a temperature of 30-70aboutWith subsequent isolation of the desired product by distillation provides a high degree of purification of ethanol from a wide range of carbonyl compounds. The decrease in the concentration of these reagents below 0.01 wt. for a hydroxide of an alkali metal and 0.005 wt. for sodium borohydride in the process of purification of the desired result does not.

The advantages of this method compared to known are its high efficiency, the need to use simplified process flowsheet absence stages of pre-treatment water, which leads to reduced losses of alcohol and the formation of additional contaminated streams.

This method can be used for purifying polluted carbonyl impurities alcohol and processes of ethanol production stages of the separation of the hydroxide of an alkali metal, followed by distillation, characterized in that the treatment is carried out with a mixture of alkali metal hydroxide and sodium borohydride, taken in an amount of 0.01 to 0.1 wt. and 0.005 to 0.3 wt. respectively.

 

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