JP2501603B2 - Method for producing α-methylstyrene - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing α-methylstyrene by a dehydration reaction of cumyl alcohol. α-Methylstyrene is used as an improving agent for styrene resins such as heat-resistant ABS resin or as a raw material for agricultural chemicals.

[Conventional technology]

Conventionally, a method of distilling and recovering from a decomposition reaction product mixture obtained by decomposing cumene hydroperoxide as a method for producing α-methylstyrene (Japanese Patent Publication No. 10142/1988) is known, but in this method, the production amount Since there is a limit to the method, a method for producing α-methylstyrene by dehydrating cumyl alcohol in the presence of a catalyst such as sulfuric acid, an organic carboxylic acid, an organic sulfonic acid, an alkali metal sulfate, TiO ₂ and an ion exchange resin ( JP-B-49-45853 and JP-A-59-67231) have been proposed.

[Problems to be solved by the invention]

However, many of these dehydration catalysts are highly corrosive to equipment materials, and catalysts that are insoluble in the reaction medium such as solid catalysts are generally expensive, have a short catalyst life, or need to be neutralized or excessively separated as a post-treatment. There was a problem such as there.

[Means for solving problems]

The inventors of the present invention, in a method for producing α-methylstyrene by liquid phase dehydration reaction of cumyl alcohol, are easy to handle, have low corrosiveness to equipment materials, and α
The present invention has been accomplished by earnestly researching a catalyst that can obtain methylstyrene in a high yield. That is, the present invention is
In the method for producing α-methylstyrene by dehydrating cumyl alcohol in a liquid phase, using phenols as a dehydration catalyst, suppressing the formation of by-products such as α-methylstyrene oligomer, It is intended to provide a method for efficiently producing α-methylstyrene in a high yield.

The raw material cumyl alcohol used in the method of the present invention does not necessarily have to be highly pure, and may be a composition containing other components. Such a composition does not require any particular purification, but when it is used industrially, it is usually preferable that the purity of cumyl alcohol is 20% by weight or more.

The phenols used as a catalyst in the method of the present invention include phenol, nitrophenol, dinitrophenol and the like. Among them, phenol is preferable because of its large reaction promoting effect. The amount of the catalyst used is not particularly limited, but usually 1.0% by weight in the reaction medium.
Used in an amount of 10 to 10% by weight.

In the method of the present invention, the reaction is carried out by heating cumyl alcohol in the liquid phase in the presence of a catalyst to cause a dehydration reaction. The reaction temperature is 140 ° C or higher, preferably 160
Temperatures above 0 C are used.

As a reaction method, a continuous method or a batch type stirring and mixing method,
Either a tubular flow system or a reactive distillation system may be used, but the reactive distillation system is most preferred because α-methylstyrene can be obtained with a high selectivity and a high yield. That is, since α-methylstyrene produced in the reaction can be rapidly removed from the reaction system, the production ratio of heavy by-products produced from α-methylstyrene can be reduced, and α-methylstyrene yield and the like can be reduced. Can be improved. In the case of carrying out the reactive distillation method, in order to improve the conversion rate of cumyl alcohol and reduce the distillation loss of phenols used as a catalyst, a rectifying tube having an appropriate number of stages may be used or reflux may be applied. can do.

The catalyst may be added directly to the reaction system, but it is usually dissolved in a raw material supplied into the reaction system and then added to the reaction system together with the raw material.

The reaction pressure is not particularly limited, but it is desirable to carry out under reduced pressure in order to remove α-methylstyrene produced in the reaction from the reaction system as quickly as possible.

The α-methylstyrene and water produced by the reaction are liquid-
Liquid separation, stripping or distillation purification yields highly pure α-methylstyrene.

〔The invention's effect〕

The method of the present invention is conventionally inevitable in comparison with a method using a mineral acid, a solid acid, an ion exchange resin, or the like.
Almost no by-products such as methylstyrene oligomers and paracumylphenol are produced, and α-methylstyrene is obtained in high yield.The catalyst used has almost no corrosiveness with respect to the material of the equipment and the raw material cumyl alcohol. It has the advantage that it is soluble in the reaction medium and easy to handle and does not require neutralization or filtration separation.

〔Example〕

The present invention will be specifically described below with reference to examples. The raw materials used in the examples have the following compositions.

Raw material composition: cumyl alcohol 76% by weight, kyumen 23% by weight, other 1% by weight [Example 1] Raw materials for a reactor (500 ml 4-necked flask) equipped with a rectification tube and a reflux device on the upper part and capable of stirring 100 g and 10 g of phenol were charged. The pressure was controlled to 270 mmHg absolute, and the reactor was heated to 170 with an oil bath while stirring.
The temperature was raised to ° C. When the total reflux has started, the reflux ratio is 0.
At the same time as withdrawing at 2, the feed liquid containing 2% by weight of phenol added to the raw material was fed to the reactor at a rate of 100 cc / Hr to carry out a continuous dehydration reaction of cumyl alcohol. The α-methylstyrene and water produced by the reaction passed through the rectification pipe, were condensed in the cooling pipe, and were collected in the distillate recovery receiver. The distillate was sampled every 2 hours, and after the liquid-liquid separation, the oil phase was quantitatively analyzed by gas chromatography to calculate the reaction yield. In this way, when the continuous dehydration reaction was carried out for 32 hours, a steady state in which the amount of the supply liquid and the amount of the distillate recovery liquid were almost balanced after about 22 hours was obtained.

Table 1 shows the reaction results obtained after reaching the steady state according to the following equation.

[Example 2] 76.5% by weight was added to a reactor (500 ml 4-necked flask) equipped with a device capable of distilling and removing only water at the top and stirring.
Take 200 g of cumyl alcohol-containing liquid and add to it phenol
15g was added.

Next, the temperature of the reactor was raised with an oil bath while stirring. Distillation of water begins at around 140 ° C, 152 ° C to 154 ° C
The reaction proceeded within this temperature range. Also, after reaching 140 ℃,
After 1.25 hours, the distillation of water stopped, and when the liquid in the reactor was analyzed by gas chromatography, the conversion of cumyl alcohol was about 99%, and the α-methylstyrene selectivity was 98.5%.
% And heavy by-product selectivity was 1.3%.

Claims (1)

(57) [Claims] 1. A process for producing α-methylstyrene by dehydrating cumyl alcohol in a liquid phase in the presence of a catalyst, wherein a phenol is used as a dehydration catalyst. .