JPH08157403A - Production of cyclohexanol - Google Patents

Abstract

PURPOSE: To produce cyclohexanol with extremely suppressing isomerization reaction of raw material cyclohexene by catalytically hydrating cyclohexene in the presence of an organic peroxide in a reaction system. CONSTITUTION: Cyclohexene is catalytically hydrated in the presence of a solid acid as a catalyst to give cyclohexanol. The reaction is carried out in the presence of 2-20 milligram equivalent/kg, preferably 3-15 milliequivalent/kg of an organic peroxide based on the raw material cyclohexene in the reaction system so that isomerization reaction of the raw material cyclohexene can be suppressed. A hydroperoxide of the formula RCOOH' (R is an alkyl or a cycloalkyl), a peroxide of the formula ROOR' (R' is R) or a peracid ester of the formula R-C(=O)OOR' is preferable as the organic peroxide. Zeolite, a strongly acidic ion exchange resin or titanium dioxide is used as the solid acid catalyst, By this method, cyclohexanol having a few isomers such as methylcyclopentenes exerting adverse influence on properties of caprolactam can be produced.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing cyclohexanol by hydrating cyclohexene.

[0002]

2. Description of the Related Art As a method for producing cyclohexanol by hydrating cyclohexene, a method using a solid acid catalyst such as zeolite or ion exchange resin has been known for a long time (Japanese Patent Laid-Open No. Sho 58-194828, Japanese Patent Laid-Open No. Hei 1-94828). -110
639 gazette, JP-A-1-190644, etc.).

In order to increase the yield by the above method,
A method of using an acid, phenol or the like together with a solid acid catalyst is also known (JP-A-59-225133, JP-A-62-126141).

[0004]

However, in the method for producing cyclohexanol by the cyclohexene hydration reaction using a solid acid catalyst, cyclohexene undergoes an isomerization reaction in the reaction system to give 1-methylcyclopentene,
It is inevitable that methylcyclopentene such as 2-methylcyclopentene is by-produced (Japanese Patent Laid-Open No. 3-28754).
No. 8, etc.). Furthermore, methylcyclopentenes are
All or part of it undergoes a hydration reaction in the reaction system, and is a structural isomer of the target product, cyclohexanol, 1-
It becomes methylcyclopentanols such as methylcyclopentanol and 2-methylcyclopentanol. The boiling point of methylcyclopentanols is almost the same as that of cyclohexanol, and it is difficult to separate them by ordinary distillation purification. Therefore, the by-product of methylcyclopentanols significantly reduces the purity of the product cyclohexanol. It was the cause.

Cyclohexanol is generally used as a raw material for producing caprolactam. That is, cyclohexanol is dehydrogenated to cyclohexanone, which is further reacted with hydroxylamine to be converted into cyclohexanone oxime, which is subjected to Beckmann rearrangement to obtain caprolactam. According to the study of the present inventors, it was confirmed that one of the impurities in cyclohexanol, methylcyclopentanol, remained in the subsequent reaction step, which was one of the factors that deteriorated the quality of the product caprolactam. are doing. Specifically, it has a serious adverse effect on the Hazen color number, which indicates the degree of purification of caprolactam, the permanganic acid number, and the volatile matter.

[0006]

[Means for Solving the Problems] In the hydration reaction of cyclohexene, as a result of extensive studies on means for suppressing the cyclohexene isomerization reaction, the catalytic hydration of cyclohexene by coexisting an organic peroxide in the reaction system. It was found that the isomerization reaction of the starting material cyclohexene can be remarkably suppressed by carrying out, and the present invention has been completed.

That is, the gist of the present invention is to produce cyclohexanol by catalytically hydrating cyclohexene using a solid acid as a catalyst. A method for producing cyclohexanol is characterized in that 20 mg equivalent / kg is present. Hereinafter, the present invention will be described in detail.

The solid acid catalyst used as a catalyst in the present invention is usually zeolite, strongly acidic ion exchange resin, zirconium dioxide, titanium dioxide, aluminum oxide,
Mention may be made of silicon dioxide, preferably zeolite. Specific examples of zeolites include crystalline aluminosilicates such as mordenite, erionite, ferrilite, ZSM-based zeolites announced by Mobil and boron, iron,
Examples thereof include metalloaluminosilicates and metallosilicates containing foreign elements such as gallium, titanium, copper and silver. As the exchangeable cation species of zeolite, a proton exchange type (H type) is usually used.
8 to 1 such as alkaline earth elements such as a and Sr, rare earth elements such as La and Ce, Fe, Co, Ni, Ru, Pd, Pt and the like
It is also effective that it is exchanged with at least one cation species of the Group 0 element. In addition, Ti, Zr, Hf, Cr,
It is also effective to contain Mo, W, Th and the like. Further, the shape of these zeolites is not particularly limited, and examples thereof include powder and granules. They are,
The carrier or binder may contain alumina, silica, titania, or the like. The amount of the catalyst used is usually 0.005 to 100, preferably 0.05 to 10, by weight ratio with respect to cyclohexene.

A feature of the present invention is that the organic peroxide is present in the reaction system in an amount of 2 to 20 mg / kg, preferably 3 to 15 mg / kg, relative to the starting cyclohexene. In the present invention, the presence of the organic peroxide in the above range suppresses the isomerization reaction for the intended reaction. If the amount of the organic peroxide is less than the above range, the isomerization reaction will not be suppressed, and if it is too large, the active sites will be poisoned more than necessary and the activity of the hydration reaction will decrease. The concentration of the amount of organic peroxide in cyclohexene is a value measured by an iodometric titration method (New Experimental Chemistry Lecture Volume 14, Item 1243, Maruzen), and is equivalent to milligram equivalent of active peroxide oxygen per unit weight. It is expressed as a number.

In the present invention, the reason why the cyclohexene isomerization reaction can be suppressed is not clear, but it is considered as follows. Both the hydration reaction and the isomerization reaction of cyclohexene occur at acidic points on the solid catalyst. These reactions are competitive reactions, and the balance of both reactions changes depending on the nature of the acidic point. It is generally considered that the stronger the acidic point is, the more accelerated the cyclohexene isomerization reaction is. When a specific amount of organic peroxide coexists in the reaction system, the organic peroxide acts on a stronger acidic point and poisons the acidic point. Therefore, if the amount of the organic peroxide coexisting in the reaction system is controlled to an appropriate amount, it is possible to selectively poison only the strong acidic points that mainly cause the isomerization reaction of cyclohexene. It is presumed that only the isomerization reaction can be suppressed without reducing the activity of cyclohexene hydration reaction.

The organic peroxide in the present invention usually means
An organic compound having a single bond of oxygen-oxygen in the molecule is shown, preferably a hydroperoxide represented by R-OOH, a peroxide represented by R-OO-R ', and R-C.
Peracid represented by (= O) OOH, R-C (= O) OO
Examples thereof include peresters represented by R ′. In these general formulas, R and R ′ each represent an alkyl group or a cycloalkyl group which may have an unsaturated bond.

These organic peroxides may be mixed with cyclohexene and fed to the reactor or may be fed separately.
When mixed with cyclohexene and fed, the organic peroxide is usually contained in cyclohexene fed to the reactor in an amount of 2%.
It is desirable that -20 mg equivalent / Kg, preferably 3-15 mg equivalent / Kg be present.
For example, there is a method in which an oxidant such as molecular oxygen, hydrogen peroxide, or ozone is allowed to act on cyclohexene, and an organic peroxide derived from cyclohexene such as 2-cyclohexene hydroxide is present in the starting cyclohexene.

The hydration reaction in the present invention is carried out in a commonly used format such as a batch system or a continuous system. Regarding the reaction temperature, a low temperature is advantageous from the aspect of equilibrium of cyclohexene hydration reaction and an increase in side reactions, but a high temperature is advantageous from the aspect of reaction rate, but usually 50 to 250 ° C.
Preferably 60 to 200 ° C., more preferably 70 to 18
0 ° C. The reaction pressure is not particularly limited, and cyclohexene and water may exist as a gas phase or a liquid phase, but preferably exist as a liquid phase.

The molar ratio of cyclohexene as a raw material to water is selected from a wide range and varies depending on whether the reaction system is a continuous system or a batch system. However, a large excess of either cyclohexene or water reduces the reaction rate and is not practical. Therefore, the molar ratio of water to cyclohexene in the reactor is usually 0.01 to
It is 100, preferably 0.1 to 30. The reaction time or residence time is usually 3 to 300 minutes, preferably 10 to 180 minutes.

In addition to cyclohexene which is a reaction raw material and water, it is preferable that an inert gas such as nitrogen, hydrogen, helium, argon or carbon dioxide is present in the reaction system.
In this case, the smaller the oxygen content in the inert gas, the more preferable, but the oxygen content is usually 100 ppm or less, preferably 50 ppm or less, more preferably 20 ppm or less. Further, an aliphatic hydrocarbon such as hexane, an aromatic hydrocarbon such as benzene, and an oxygen-containing organic compound such as a benzoic acid derivative may coexist in the reaction system.

[0016]

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples as long as the gist thereof is not exceeded. Example Substantially free of methylcyclopentenes (10 pp
m or less) After cyclohexene was purified by distillation, air was allowed to act at 50 ° C. to adjust the concentration of organic peroxide such as 2-cyclohexene hydroxide to 5 mg / kg. .

In a stainless steel autoclave with an internal volume of 2.5 L equipped with a stirrer, 100 g of gallium silicate (SiO ₂ / Ga ₂ O ₃ ratio = 50) and 300 g of water were used as catalysts.
Was charged, and the inside of the system was replaced with nitrogen gas. Rotation speed 300 rp
The temperature of the reactor is raised with stirring at m, and the reaction temperature is 120 ° C.
Then, the cyclohexene was added at 150 g / h
Was continuously fed to the reactor at a rate of. After liquid-liquid separation of the reaction mixture, only the oil phase was continuously withdrawn from the system.

The concentration of methylcyclopentenes (the total of 1-methylcyclopentene, 2-methylcyclopentene and 3-methylcyclopentene, the same applies hereinafter) in the discharged oil phase 20 hours after starting the supply of the starting material cyclohexene was 50 p.
The concentrations of pm and cyclohexanol were 10.1% by weight. Comparative Example Instead of cyclohexene having an organic peroxide concentration of 2 mg / kg, cyclohexene substantially free of methylcyclopentenes (10 ppm or less) was purified by distillation (organic peroxide concentration 0.5 mg equivalent / k
The same procedure as in Example was performed except that g) was used.

The concentration of methylcyclopentenes in the discharged oil phase 20 hours after the start of feeding the starting material cyclohexene was
The concentration of 220 ppm and cyclohexanol was 10.1% by weight.

[0020]

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to produce cyclohexanol containing few isomers such as methylcyclopentenes which adversely affect the physical properties of caprolactam.

Claims (2)

[Claims] 1. A method for producing cyclohexanol by catalytically hydrating cyclohexene using a solid acid as a catalyst, wherein an organic peroxide is present in the reaction system in an amount of 2 to 20 mg equivalent / kg based on the starting cyclohexene. A method for producing cyclohexanol, comprising: 2. The method for producing cyclohexanol according to claim 1, wherein the organic peroxide in the cyclohexene fed to the reactor is 2 to 20 milligram equivalent / kg.