SU1710541A1 - Phenol rectification technique - Google Patents

Abstract

The invention relates to the production of phenol by the puppet method, in particular its purification. The goal is a higher quality phenol. For etsego, the initial phenol is subjected to primary distillation in 2 consecutive columns into two fractions [with the ratio of the first and second fractions / 1:

Description

The invention relates to the production of phenol by the cumene method, in particular the production of high purity phenol.

Phenol by the cumene method is obtained by the oxidation of isopropylbenzene to hydroperoxide, the concentration of hydroperoxide and its subsequent decomposition into phenol and acetone in the presence of a catalyst — sulfuric acid. The initial isopropylbenzene contains 0.1-0.5% of impurities of various hydrocarbons, acetophenone and dimethylphenylcarbinol are formed at the stage of oxidation and at the stage of acid decomposition, hydroperoxide, side reactions occur with the formation of a number of compounds: acetaldehyde, mesityl oxide, diacetone alcohol, L-methylstyrene, methylbenzofurans, dimers of methylstyrene, cumylphenols and others with boiling temperatures higher than that of phenol. The content of a number of components is relatively small, but they significantly impair the quality of phenol and are removed by conventional distillation methods difficult or not at all. These include mesityl oxide, diacetone SP1FT, Ob-methylstyrene, methylbenzofurans, and a number of non-identified

compounds. Acetophenone and dimethylphenylcarbinol should also be attributed to impermeable impurities. Phenol, derived from the decomposition reaction mass (crude phenol), can be;% by weight; wt.%:

Acetone0.02-0.5

Mesityl oxide 0.005-0.3 Diacetone alcohol 0.002-0.04 Isopropylbenzene 0.04-1.0 oi-Methylstyrene 0.3-0.2 Methyperbenzofuran 0.01-0.003 Acetophenone 0.02-0.4 Dimetyphenylcarbinol0, 01- 0.2

Unidentified compounds 0.05-0.1 Total impurities 0.45-4.0 A number of methods are known for removing impurities from crude phenol in order to increase its quality. In the USSR, the method of stripping is widespread: impurities are azeotropic by distillation with water in combination with subsequent purification on cation exchanger and distillation with obtaining high purity phenol. The applied technology does not provide a sufficient degree of distillation of the impurities by azeotropic distillation with water, which limits the removal efficiency of impurities by cation cleaning and reduces the service life of the cation exchanger.

There is a method according to which the purification of raw phenol from impurities is carried out by extractive distillation with glycols. The process is carried out in a two-column system with the supply of phenol in the middle of the extractive distillation column, and the glycol in the middle of the upper part. A distillate containing impurities present in the starting material and some amount of phenol is taken on top. The main part of the phenol goes along with the glycol bottoms prod and arrives in the next distillation column to separate the purified phenol from: the extractant (glycol), which is returned to the first column flj.

Industrial hight. the implementation of this method using diethylene glycol as an extractant showed effective removal of impurities boiling up the phenol to the boiling point. The total content of impurities in the purified phenol is 20-150 million,

(0,002-0,015%), mainly mesityl oxide, metnbenzofurans ,.

The disadvantages of this method are the high energy costs associated with maintaining the required temperature in the bottom of the extractant recovery column, and also the loss of the extractant due to its resinification in the process. Since the tarification of the glycol leads to a deterioration of the extracting properties, it is necessary either to ensure the distillation of the extractant under the vacuum or replace it with fresh,

Closest to the invention is a method 21, according to which high purity phenol is obtained, in particular with a reduced content of methyl benzofurans, with a supply of water, solvent and phenol in the ratio

(O, 05-0,8) :( O, 005-0,1): 1 to the distillation column. The solvent used is preferably aromatic hydrocarbons (isopropyl benzene and oi methyl styrene). From the top of the distillation column, the distillate containing impurities, solvent and water is distilled off, it is stratified into aqueous and organic layers. In the latter, impurities are extracted. This organic layer is removed and purified from phenol. The aqueous phase is returned to the column as irrigation. A cubic product is obtained with phenol containing a relatively small amount of impurities, higher than 1 boiling point below the boiling point of phenol. The total content of these impurities is not more than 40 million (0.004%), including

the number of methylbenzofurans less than 20 million (0,0026%). A high degree of purification of phenol from mesityl oxide and methylbenzofuran is achieved.

At the same time, the oi-methylstyrene content is still high, and may require additional purification to improve quality.

The disadvantage of this method is that acetophenone and dimethylphenylcarbinol

practically not removed, the content of acetophenone in phenol after purification increases, for example, from 2544.5 million (0.254%) to 2955 ppm, 2955%), and the content of dimethylphenylcarbinol is reduced only from 104 to 63 million

(0,0104-0,0063%). General content

impurities reduced from 3542 to

3070 ppm (0.3542-0.307%). Effective51

The value of the process largely depends on the ratio of water and phenol. Increasing this ratio causes an increase in energy consumption, so it is 1. limited to relatively low values of up to 0.8: 1. This limits the possibility of increasing the efficiency of purification of phenol during distillation with water in the azeotropic distillation mode.

The purpose of the invention is to improve the quality of phenol.

The goal is achieved by the fact that the initial phenol is subjected to primary distillation in two successive columns into two fractions with a ratio of the first and second fractions 1: (1-4) and the bottom product, while the first fraction with an increased content of impurities is subjected to noBT (distilled distillate In the 3rd column of C. boron distillate, which is split into the aqueous and organic layer containing impurities, it is removed from the system, and the aqueous is returned to the third column for irrigation. water and phenol in the ratio (0.15-2): 1, mixed with the second fraction of the primary distillation and subjected to distillation in the 4th column with all distillate - a mixture of phenol and impurities, which is returned to the 3rd column, and the bottoms-residue - phenol.

The method is illustrated by the following examples.

The drawing is a flow chart of the method.

К .1 and К 2 - columns in the fission of phenol fractions, К 3 - rectification column of the 1st fraction with water, К 4 - rectification column and drying of the 1st and 2nd fractions, Е 1 - Florentine vessel. Streams: 1 - phenolic stream - raw materials, 2 - phenolic resin, 3 - fraction of impurities, 4 - purified phenol.

Example 1. The phenol stream obtained by the disintegrant decomposition method is distilled in columns K-1 and with the release of two fractions of phenol and bottom residue (resin) in the amount of 157, 628 and 102 g / h, respectively, 157 g / h of the first fraction with impurities of 3.06% and 542 g / h of phenolic WATER with a phenol content of 8.7% are fed into a distillation column K-3 of continuous action. At the top

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the column is maintained at a temperature of 98.5 ° C, at the bottom. The distillate is taken from above and stratified in E-1 with the separation of 15 g / h of hydrocarbon (upper) layer containing selected impurities and phenol, and 162 g / h of aqueous (lower) layer, which are returned to column K-3. From the bottom of the column is entered

522 g / h of the bottom product containing 346 g / h of water and 176 g / h of phenol purified from impurities (the ratio of water: phenol is 2: 1). The bottom product is mixed with 628 g / h of the second phenolic fraction from a column with an impurity content of 0.087% and subjected to azeotropic distillation in the rectification column K-4. . This phenolic water with a phenol content of 8.9% is returned to column K-3. From the cube of the column K-4. outputs 770 g / h of dried phenol. The total consumption of water for the distillation of phenol is 63% for the purified phenol. The composition of the raw material (phenol after separation of the resin) and its fractions, as well as the composition of the purified phenol are given in this and subsequent examples.

in the table.

Example 2. A phenol stream is separated by distillation in columns K-1 and K-2 to obtain 200 g / h of the first fraction, 200 g / h of the second fraction of phenol and 52 g / h of resin.

1 i

200 g / h of the first fraction of phenol containing 1.3% of impurities, and 133 g / h of phenolic water containing phenol

9.7% is fed to the continuous distillation column K-3. A distillate is taken from the top of the column, from which, after separation, 8 g / h of a hydrocarbon layer consisting of impurities and phenol are separated, a. 100 g / h of water (lower) layer is returned to column K-3. From the bottom, 225 g / h of the bottom product containing 29.0 g / h of water and 196 g / h of phenol (0.15: 1 ratio), which is mixed with 200 g / h of the second phenolic fraction from column K-2 containing impurities 0,066% and subjected to azeotropic distillation in a distillation column K-4.

The distillate (phenolic water with a phenol content of 12.1%) is taken in an amount of 33 g / h and fully returned to column K-3. From the bottom of the K-4 column, 392 g / h of purified phenol was obtained. Suction steam consumption for the distillation of phenol is 33% for crude phenol.

Example 3. The phenol stream is separated by distillation in columns K-1 and IC-2 to obtain 300 g / h of the first fraction, 700 g / h of the second phenolic fraction and 130 g / h of resin.

300 g / h of the first fraction containing 2.09% of impurities and 679 g / h of phenolic water with a phenol content of 8.9% are fed to the distillation column K-3. From the top of the column after condensation and distillation separation, the distillate is discharged. 17 g / h the hydrocarbon layer, and the water layer in the amount of 329 g / h is returned to the column K-3. A bottom product containing 317 g / h of water and 316 g / h of phenol (1: 1 ratio), | Output 533 g / h from the bottom of the column, mixed with 700 g / h of the second phenolic fraction from K- 2, containing 0.078% of impurities, for azeotropic distillation in the next column. Distil t (phenolic water with a phenol content of 9.4%) in an amount of 350 g / h enters the K-3 column. 983 g / h of purified phenol were removed from the bottom of the column. The total consumption of water for the purification of phenol was 62% for crude phenol.

Clause 4. The phenol stream is separated by distillation in columns K-1 and K-2 to obtain 300 g / h of the first fraction, 700 g / h of the second fraction and 130 g / h of resin.

300 g / h of the first fraction containing 2.09% of impurities and 367 g / h of phenolic water with a phenol content of 9.5% are fed to a distillation column. After condensation, distillate is stratified with the separation of 16 g / h of a hydrocarbon layer and 335 g / h of an aqueous layer, which is returned to column K-3. The bottom product, containing 29 g / h of water and 287 g / h of phenol (0.1: 1 ratio) was extracted in the amount of 316 g / h from the bottom of the column, is mixed with 700 g / h of the second phenolic fraction from K-2 containing 0.078% impurity, for azeotropic distillation

in column K-4 .. Distil t (pheno-na water with a phenol content of 9.4%) in an amount of 32 g / h enters column K-3. 984 g / h of dried phenol were removed from the cube. A milliliter consumption of water for the purification of phenol is 33% for phenol.

An example with the use of water in quantities exceeding the proposed limits (with a multiplicity of more than 2) is not given due to the non-profitability of the option. An increase in the multiplicity causes an increase in the energy consumption for the distillation of water with a relatively small increase in the purification efficiency.

The proposed method allows to obtain phenol with an impurity content of not more than 0.2%, which is 5 times less than in the prototype.

Formula of the invention. The method of purification of phenol obtained by the cumene method by distillation with water and separation of impurities in the form of distillate, characterized in that, in order to improve the quality of the target product, the initial phenol is subjected to primary distillation in two consecutive columns into two fractions when the ratio of the first and second fractions is 1 :() and the bottom product, the first fraction with a high content of impurities is subjected to repeated distillation in the 3rd column with the selection of distillate, which is layered on an aqueous and organic layer containing impurities is removed from the system, and the aqueous is returned to the 3rd column for irrigation, while the bottom product of the 3rd column containing water and phenol in a ratio of (O, 15-2): 1 is mixed with the second fraction of the primary rectification and Distilled in the 4th column with separation of the distillate mixtures of phenol and impurities, which is returned to the 3rd column, and the bottom residue - phenol.

Claims (2)

SUMMARY OF THE INVENTION A method for purifying phenol obtained by the cumene method by distillation with water and isolating impurities in the form of a distillate, characterized in that, in order to improve the quality of the target product, the initial phenol is subjected to primary rectification in two successive columns into two fractions in the ratio of the first and the second fraction 1: (1-4) and per cubic product, while the first fraction with a high content of impurities is subjected to re-distillation in the 3rd column with the selection of the distillate, which is stratified into water the organic and organic layer containing impurities, it is removed from the system. we, and water, return the 3rd column for irrigation, while the bottoms product of the 3rd column, containing water and phenol in the ratio (0.15-2): 1, is mixed with the second fraction of the primary distillation and subjected to distillation in the 4th a column with distillate separation of a mixture of phenol and impurities, which is returned to the 3rd column, and the bottom residue - phenol. Process conditions, composition of raw materials and phenol purification end products p / p Ox ratio:: phenol in a cube Flow Yield, Z on raw materials Ratio of fractions The content of impurities, wt. X acetone mesityl oxide unidentified isopropylbenzene ob-methylstyrene methylbenzofuran acetophenone dimethylphenylcarbinol 1 2: 1 Raw materials - - 0.14 0.0104 0.004 0,042 0.4305 0.010 0.0211 0,0242 amount of impurities 0.6822 Example 1 2 3 I fraction II fraction ", 1 4 0.7 0.037 0.012 0.21 2.0 0,038 0.05 0.03 0.019 0,025 0,024 3,064 0.0868 0.0038 0.002 4 The organic phase of the distillate 2.0 7.25 0.48 0.21 2.2 22.38 0.52 0.61 0.97 34.62 5 Diluted phenol 98 0.001 0.001 0.003 0.01 0.0057 0,0207 6 0.15: 1 I fraction 1 Example 2 0.28 0.017 0.009 0,084 0.83 0.02 0.03 0,048 1,301 7 II fraction - 1 0.004 - - 0,033 0,029 - 0,066 8 The organic phase of the distillate 2.0 6.95 0.03 0.21 2,075 20.96 0.52 0.33 0.85 32,23 9 Dried Phenol 98.0 , 0.001 0.004 0.0005 0.012 0.015 0.0074 0,040 ! ° 1: 1 I fraction 1 Example 3 0.47 0.028 0.014 1.4 1.3 0.033 0.028 0.08 2,098 AND II fraction - 2,33 0.003 - - 0,057 0.018 - 0,078 12 The organic phase of the distillate 3 7.6 0.55 0.25 '2.47 24.7 0.59 1.01 1.09 38.26 thirteen Dried Phenol 97 0.001 0.001 0.009 0.004 0.0057 0.21 14 0.1: 1 I freight - 1 Example 4 0.47 0.028 0.14 1.3 0.033 0.028 0.08 2,093 fifteen II fraction - 2,38 0.003 - - 0,057 0.018 0,078 16 The organic phase of the distillate 2 8.69 0.28 0.189 2,56 25.47 '0.59 6.069 0.406 38.25 17 Dried Phenol 98 - 0.001 0.006 - 0.001 0,0235 0.0005 0.020 0.018 0,07