JP2767755B2 - Purification method of α-methylstyrene - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for purifying α-methylstyrene, and more particularly to a method for purifying crude α-methylstyrene by-produced in a cumene phenol plant to improve the color of the crude α-methylstyrene. The present invention relates to a method for purifying α-methylstyrene, which is purified into high-quality α-methylstyrene.

α-Methylstyrene is a very useful substance as a resin raw material such as an ABS resin or as an intermediate raw material such as agrochemicals and surfactants, and is generally produced as a by-product when producing phenol by the cumene method.

[Conventional technology]

Α-Methylstyrene by-produced by the cumene phenol production method is usually separated and purified by distillation, but α-methylstyrene distilled from the top of the distillation column is colored yellow-green, and is a raw material for various materials. There was a quality problem to use. Conventionally, to solve this coloring problem,
-Methylstyrene was washed with alkaline water to remove coloring components, and then purified by distillation. However, the coloring components are also generated by thermal decomposition of heavy substances during distillation purification,
Some of them have a boiling point very close to that of α-methylstyrene.
It acts the same as methylstyrene and cannot be separated. Tokiko
JP-A-48-10142 discloses that in order to improve the hue of α-methylstyrene, an α-methylstyrene fraction having an improved hue is obtained by extracting an α-methylstyrene fraction from a tray below the distillation tower. Have been proposed.

[Problems to be solved by the invention]

However, in such a purification method, a purified α-methylstyrene
Although the purity of methylstyrene decreases and the hue of the purified α-methylstyrene (APHA indication, the same applies hereinafter) is about 15, which is slightly improved in terms of hue compared to the method of extracting from the top of the tower. However, it has not been possible to obtain products of satisfactory quality.

The present invention relates to a method for purifying α-methylstyrene by-produced during the production of cumene-method phenol, a method for producing α-methylstyrene, which has improved hue and can obtain α-methylstyrene of high purity. It is something to offer.

[Means for solving the problem]

The present inventors have made intensive studies to achieve the above object, and as a result, prior to alkali treatment, by removing heavy matter by distillation in advance, the purity and hue of purified α-methylstyrene can be improved. That is, the present invention has been completed.

That is, the present invention provides a method for purifying α-methylstyrene in which crude α-methylstyrene separated as a by-product in the production of phenol by the cumene method is purified by distillation. This is a method for purifying α-methylstyrene, which comprises treating the top solution with an alkali and then rectifying the solution in a second distillation column.

[Specific description of the invention]

(1) Raw Material The raw material in the present invention is crude α-methylstyrene by-produced in the method for producing phenol by the cumene method. The method for producing phenol by the cumene method decomposes cumene hydroperoxide obtained by oxidizing cumene to produce phenol and acetone together, and α-methylstyrene is produced as a by-product in the production process in the method. I do. The by-product α-methylstyrene is supplied to a hydrocarbon recovery tower after separating phenol and acetone from the decomposition product of cumene hydroperoxide by distillation and then removing the light-boiling fraction to obtain crude α-methylstyrene.
Extracted from the bottom of the column as methylstyrene.

The thus obtained crude α-methylstyrene includes:
Usually, in addition to 75 to 95% by weight of α-methylstyrene, a small amount of cumene, butylbenzenes and heavy substances such as dimers or more of α-methylstyrene are contained.

(2) First Distillation In the purification method of the present invention, first, the crude α-methylstyrene is distilled to separate a high-boiling substance to obtain high-purity α-methylstyrene from the top of the column. The distillation conditions at this time can be arbitrarily selected as long as high-purity α-methylstyrene can be obtained.

(3) Alkali treatment High purity α- extracted from the top of the first distillation column
Alkaline treatment of methyl styrene. As the alkali to be used, a hydroxide compound of a monovalent or divalent alkali metal and an alkaline earth metal such as caustic soda,
Solid basic substances such as anion exchange resins and magnesia are used.

As the alkali treatment method, any of a stirring tank method and a circulation method may be used, but a monovalent or divalent alkali metal or alkaline earth metal hydroxide compound such as caustic soda is used as an aqueous solution and a stirring tank is used. An alkali washing method is preferred. In the case of a solid basic substance such as an anion exchange resin or magnesia, treatment by a flow system is preferable.

When an alkaline aqueous solution is used, the ratio between the overhead liquid and the alkaline aqueous solution is 1:10 to 10: 1 by volume, preferably,
1: 5 to 1: 1. The processing temperature is 20 to 100 ° C, preferably 60 to 90 ° C. The concentration of the alkaline water to be used is required to be 0.1N or more, preferably 0.5N or more. The processing time should be 30 seconds or more, preferably 2 minutes or more. Further, the alkali treatment may be repeatedly performed.

The alkali washing is efficiently performed on the feed liquid to the second distillation column, but may be performed on the reflux liquid of the first column.

As a cleaning method, alkaline water may be injected into the pipe for cleaning, or a separate cleaning tank may be provided to perform the cleaning.

When using a solid basic substance, the processing conditions are 20
-100 ° C, preferably 60-90 ° C, LHSV is 0.5-30, preferably 3-15.

(4) Second Distillation The α-methylstyrene after the alkali treatment is further distilled to improve the hue. The distillation conditions of the second distillation can be arbitrarily determined. However, when washing with alkaline water is carried out, it is preferable to carry out the distillation under reduced pressure conditions, since it contains water.

The distillation operation may be a batch type or a continuous type, but a continuous type is usually used industrially.

(5) Process FIG. 1 illustrates a process in the case where cleaning with an alkaline aqueous solution is performed.

In FIG. 1, a liquid 1 extracted from a bottom of a hydrocarbon recovery tower or the like is supplied to a crude α-methylstyrene tower 2. In this crude α-methylstyrene tower, a cumene fraction 3 was extracted from the top 2a, and α-methylstyrene 4 was extracted from the bottom 2b.
Is extracted.

The crude α-methylstyrene 4 is mixed with the aqueous caustic soda solution 5, washed in the washing tank 6, and then supplied to the first column 8 of the pure α-methylstyrene tower 7.

In this tower 8, heavy substances 9 such as α-methylstyrene dimer are extracted from the bottom 8b, and a high-purity α-methylstyrene fraction 10 is extracted from the top 8b. The top liquid 10 is markedly colored by coloring components generated by thermal decomposition or the like.

The top solution 10 is mixed with an aqueous solution of caustic soda 11, sent to a washing tank 12, washed with alkali in the tank, and washed α-methylstyrene 13 separated from the alkaline waste liquid,
The purified α-methylstyrene is supplied to the second column 14 of the column 7. In the second column, a high-purity refined α with improved hue than the top 14a
-Methylstyrene 15 is obtained.

At this time, either or both of the first tower and the second tower,
The extraction of the purified α-methylstyrene may be performed at any stage below the top of the column.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to examples.

Example 1 According to the purification process diagram of α-methylstyrene in FIG.
-Purification of methylstyrene.

The composition of the bottom liquid 4 of the crude α-methylstyrene column 2 is α-methylstyrene.
95.5% by weight of methylstyrene, 0.1% by weight of cumene, 1.0% by weight of butylbenzenes, 1.9 dimer of α-methylstyrene
After washing with a 0.5N aqueous solution of caustic soda 5 at 1.5% by weight and other 1.5% by weight, separated in a washing tank 6 and then purified α-
The methylstyrene column 7 was fed at a rate of 50 g / h to the 30th stage from the top 8a of the first column 8.

The first column 8 is a packed column of 55 theoretical stages packed with SUS316 stainless steel packing material, operated under the conditions of atmospheric pressure and reflux ratio of 12, and a high purity α-methylstyrene fraction 10 at a rate of 41 g / h. At the top of the tower.

The purity of the α-methylstyrene fraction 10 in the overhead liquid is 99.5
And 0.1% by weight of cumene and 0.2% by weight of butylbenzenes as impurities. The hue was 20.

This top solution 10 was treated with an equal volume of a 0.5 N aqueous solution of caustic soda at a temperature of 70 to 80 ° C. for 10 minutes and then treated 13
Had a hue of 10.

Further, this treatment liquid 13 was placed at the fourth stage from the top of the second column 14 having eight theoretical plates packed with stainless steel packing,
It was fed at a rate of 50 g / h and distilled at a reflux ratio of 2 under a reduced pressure of 50 mmHg. In this way, the hour 4 from the top 14a of the second tower 14
Purified α-methylstyrene obtained at a speed of 9 g has a purity of 9
It contained 9.6% by weight, containing 0.2% by weight of cumene and 0.2% by weight of butylbenzenes as impurities, and had a hue of 5 or less.

Example 2 The top liquid 10 obtained from the first column of the purified α-methylstyrene column 7 of Example 1 was washed for 10 minutes at a temperature of 25 ° C. using an equal volume of 0.5 N caustic soda water. , Treatment liquid 13
Had a hue of 15.

This treatment liquid was distilled in the second column 14 packed with a stainless steel packing material having eight theoretical plates in the same manner as the treatment liquid 13 of Example 1, and the hue of the purified α-methylstyrene obtained from the column top 14a was obtained. Was 5.

Example 3 KW-20 was used instead of the alkali washing of the top liquid 10 in Example 1.
00 (synthetic hydrotalcite manufactured by Kyowa Chemical Co., Ltd.) 83.5
The top liquid 10 obtained in Example 1 was supplied to the bottom of the glass tube filled with g at a temperature of 80 ° C. at a rate of 1200 ml / h for alkali treatment, and the processing liquid was extracted from the top. The hue of the obtained treatment liquid was 25.

This treated liquid was distilled in the second column 14 of the purified α-methylstyrene column 7 packed with stainless steel packing having eight theoretical plates in the same manner as the treated liquid 13 of Example 1, and was obtained from the top 14a. The hue of the purified α-methylstyrene was 5 or less.

Comparative Example 1 The top liquid 10 obtained in Example 1 was washed at 25 ° C. for 10 minutes using an equal volume of distilled water instead of alkali washing. The color of the obtained treatment liquid was 20.

This treated liquid was distilled in the second column 14 of the purified α-methylstyrene column 7 packed with stainless steel packing having eight theoretical plates in the same manner as the treated liquid 13 of Example 1, and was obtained from the top 14a. The hue of the purified α-methylstyrene was 15.

〔The invention's effect〕

In the method for producing α-methylstyrene of the present invention, crude α-methylstyrene by-produced in a cumene phenol plant is distilled in two stages, and the first-stage overhead is treated with alkali to obtain α-methylstyrene. The hue of methylstyrene is greatly improved, and it can be purified with high purity and at low cost.

The α-methylstyrene purified by the method of the present invention does not color the product even when used as various materials such as an ABS resin, so that a high quality product can be obtained.

[Brief description of the drawings]

FIG. 1 is a purification process chart used in the method for producing α-methylstyrene of the present invention. 1: bottom liquid of hydrocarbon recovery tower, 2: crude α-methylstyrene tower, 3: cumene fraction, 4: crude α-methylstyrene 5,11: aqueous sodium hydroxide solution, 6,12: washing tank, 7: Purified α-methylstyrene tower, 8: First tower, 9: Heavy matter, 10: High-purity α-methylstyrene fraction, 12: Wash tank, 13: Washed α-methylstyrene, 14: Second tower, 15: Purified α-methylstyrene.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C07C 15/44 C07C 7/04 C07C 7/10

Claims (1)

(57) [Claims] In a method for purifying α-methylstyrene, wherein crude α-methylstyrene separated as a by-product in the production of phenol by the cumene method is purified by distillation, distillation is carried out in two stages, and the top of the first distillation column is obtained. A method for purifying α-methylstyrene, comprising treating a liquid with an alkali and then rectifying the liquid with a second distillation column.