JPS5818321B2 - Hydrogen halide recovery method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for recovering hydrogen halides, and more specifically, the present invention relates to a novel method for recovering hydrogen halides. The present invention relates to a method for industrially recovering hydrogen halide dissolved in a reaction solution after liquid phase oxidation in the presence of.

BACKGROUND ART Conventionally, a method for producing phenols and ketones by liquid-phase oxidation of an aromatic hydrocarbon having a secondary alkyl group or a cycloalkyl group as a substituent in the presence of hydrogen halide is known.

For example, as a liquid phase oxidation method of aromatic hydrocarbons, a method of producing phenol and acetone using cumene, a method of producing phenols and cyclohexanone through hydroperoxide using matacyclohexylbenzene or dicyclohexylbenzene, etc. are known.

In addition, the hydrogen halides used are dissolved in the solution after the reaction in a free state or in an admixture with by-product shidaketones, and especially hydrogen bromide is dissolved in these. Often dissolved in both forms.

It is difficult to recover hydrogen halide dissolved in the solution after the reaction, especially hydrogen bromide in an adduct state with ketones, by ordinary physical treatment.

Therefore, from the reaction solution obtained by liquid phase oxidation of an aromatic hydrocarbon having a secondary alkyl group or cycloalkyl group as a substituent in the presence of hydrogen halide, the hydrogen halide used for use can be industrially extracted. The reality is that no method has been developed for separating and recovering it.

In view of this situation, the present inventors conducted various studies with the aim of establishing a technology that can industrially separate and recover hydrogen halides from the system after this reaction.

As a result, by skillfully combining the steps of recovering hydrogen halide in a free state in the liquid and recovering hydrogen halide in an adducted state with ketones, hydrogen halide can be produced extremely effectively. The inventors discovered that hydrogen can be recovered and arrived at the present invention.

That is, the present invention provides a method for liquid-phase oxidation of an aromatic hydrocarbon having a secondary alkyl group or a cycloalkyl group as a substituent in the presence of hydrogen halide, which involves introducing an inert gas into the liquid after the reaction. The first step is to treat the reaction solution with an alkali and the second step is to separate the alkali halide salt produced.

Then a third step of treating the alkali halide salt with phosphoric acid.
This is an industrially excellent hydrogen halide recovery method consisting of the following treatment steps.

The method of the invention comprises isopropylbenzene (cumene), 5
Secondary alkyl aromatic hydrocarbons such as ec-butylbenzene, 5eC-amylbenzene, cyclobutylbenzene, cyclopentylbenzene, cyclohexylbenzene, cycloheptylbenzene, cyclooctylbenzene, cyclononylbenzene, cyclodecylbenzene, cyclododecylbenzene , a method of liquid-phase oxidation of cycloalkyl aromatic hydrocarbons such as dicyclohexylbenzene and tricyclohexylbenzene, in which multiple cycloalkyl groups are substituted on the oyohihenzene nucleus, in the presence of hydrogen halide, which dissolves in the liquid after the reaction. It can be effectively employed for the recovery of hydrogen halides.

Next, the present invention will be explained in more detail.

First, in the first step, an inert gas is introduced into the liquid after the reaction.

In this process, by introducing an inert gas while stirring or flashing the reaction solution, the hydrogen halide dissolved in the free state in the solution is almost completely entrained in the inert gas and recovered. can do.

The term "inert gas" as used herein means a gas that hardly reacts with hydrogen halide in the reaction system in this treatment step; for example, oxygen, air, nitrogen, etc. are useful.

Next, in the second step, the hydrogen halide in the addition state with the ketones is separated from the reaction system as a crystalline alkali halide salt.

This step can be carried out satisfactorily under mild conditions, ie, at room temperature and under normal pressure.

Alkali is also halogenated water. Compounds that react with hydrogen to form crystalline salts can be used, such as ammonia, sodium oxide, sodium carbonate, ammonium carbonate, calcium carbonate, etc. It is sufficient to use the theoretical quantities necessary for the summation.

Next, in the third step, the alkali halide salt separated and obtained in the second step is treated with phosphoric acid.

In this step, an alkali halide salt and phosphoric acid are reacted to recover hydrogen halide in the form of a gas, and this treatment is preferably carried out while the reaction system is stirred and heated.

The amount of phosphoric acid used is preferably slightly in excess of the alkali halide salt.

In the second and third steps, the hydrogen halide that is in the addition state with the ketones in the liquid after the reaction can be recovered in high yield.

As explained above, the present invention provides a method for producing phenols and ketones by liquid phase oxidation of aromatic hydrocarbons having a secondary alkyl group or cycloalkyl group as a substituent. This is an extremely industrially significant invention, as it has established a technique for recovering it at a high yield, and has the advantage that the recovered gaseous hydrogen halide can be reused in the reaction.

Next, examples of the present invention will be given.

Example Hydrogen bromide and hydrogen chloride were added to a solution of cyclohexylbenzene in ethylene dichloride, followed by liquid phase oxidation using oxygen to synthesize phenol and cyclohexanone.

Obtained 2.50 mmol of hydrogen bromide and 43 mmol of hydrogen chloride
, 5 mmol of the reaction solution containing 59 cc of
Oxygen was introduced at a rate of 40 CC/min for 10 minutes.

As a result of measuring the amount of hydrogen bromide and hydrogen chloride recovered together with oxygen, the amount of hydrogen bromide was 0.39 mmol, and the amount of hydrogen chloride was 43.4 mmol.

Next, the reaction solution was saturated with ammonia gas at 1 atm at room temperature, and the resulting ammonium bromide crystals were roasted.

Next, 1 cc of phosphoric acid was added to the collected ammonium bromide (0.20 g), and the mixture was stirred at a temperature of 40° C. for 30 minutes, and the generated hydrogen bromide was purged with nitrogen.

As a result of measuring the amount of hydrogen bromide recovered together with nitrogen, 2.
It was 0.05 mmol.

The recovery rate of total hydrogen bromide in this example was 97.
5%, and the recovery rate of total hydrogen chloride is as high as 99.8%.

Claims (1)

[Claims] 1 In a method of liquid phase oxidation of an aromatic hydrocarbon having a secondary alkyl group or a cycloalkyl group as a substituent in the presence of hydrogen halide, the first step of introducing an inert gas into the liquid after the reaction , a second step of treating the reaction solution with an alkali and separating the generated alkali halide salt;
Then a third step of treating the alkali halide salt with phosphoric acid.
A hydrogen halide recovery method characterized by comprising each treatment step.