JPH08193062A - Production of epsilon-caprolactam - Google Patents

Abstract

PURPOSE: To provide an industrially useful process for producing ε-caprolactam having a quality comparable to that of the conventional products inexpensively. CONSTITUTION: In this process for production of ε-caprolactam where cyclohexanol as a hydration product of cyclohexene is dehydrogenated to cyclohexanone, which is converted into cyclohexanone oxime with hydroxylamine, further, the oxime product is subjected to the Beckmann rearrangement to be converted into ε-caprolactam, the content of methylcyclopentanol is kept lower than 200ppm in the cyclohexanol fed to the dehydrogenation process.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing ε-caprolactam using cyclohexene as a starting material.

[0002]

2. Description of the Related Art ε-Caprolactam is produced by Beckmann rearrangement of cyclohexanone oxime, and cyclohexanone oxime as a raw material is generally produced by reacting cyclohexanone with hydroxylamine.

Conventionally, cyclohexanone, which is a raw material for ε-caprolactam, is prepared by first oxidizing cyclohexane with molecular oxygen to produce a mixture of cyclohexanol and cyclohexanone, and then dehydrogenating cyclohexanol in the mixture to form cyclohexanone. How to do, or
It was industrially produced by a method of partially reducing hydrogen of phenol and then producing cyclohexanone by a rearrangement reaction.

In recent years, as a method for industrially producing cyclohexanol, attention has been paid to a method of hydrating cyclohexene in the presence of a zeolite catalyst. Although such a reaction itself has been known since the 1940s, production on an industrial scale has only recently been carried out (see Chemical Economy, March 1993, pp. 40-45).

[0005]

The method for producing cyclohexanol from cyclohexene is very advantageous in terms of cost if it can be carried out on an industrial scale, and is considered to be a preferable method for producing cyclohexanol. However, ε-caprolactam produced from cyclohexanone using cyclohexanol as a raw material obtained by the method is different from ε-caprolactam produced from cyclohexanone obtained by another conventional method, and is produced from cyclohexene in quality. Our work has revealed that there are unique problems in the method.

[0006]

Means for Solving the Problems As a result of intensive studies on the above problems, the present inventors have found that 200 p of methylcyclopentanol in cyclohexanol to be subjected to a dehydrogenation reaction is used.
The inventors have found that by controlling to pm or less, ε-caprolactam that is comparable to ε-caprolactam produced using conventional raw materials can be obtained, and the present invention has been accomplished. That is,
The gist of the present invention is to prepare cyclohexanol obtained by a hydration reaction of cyclohexene into cyclohexanone by a dehydrogenation reaction, and then react with hydroxylamine into cyclohexanone oxime, and further perform Beckmann rearrangement to produce ε-caprolactam, A method for producing ε-caprolactam is characterized in that the content of methylcyclopentanol contained in cyclohexanol used for the dehydrogenation reaction is 200 ppm or less.

Hereinafter, the present invention will be described in detail. In the production method of the present invention, cyclohexene is first reacted with water to form cyclohexanol. The cyclohexene hydration reaction is usually carried out using a solid acid catalyst as a catalyst. The solid acid catalyst, usually, zeolite and ion exchange resin, and the like, as the zeolite, crystalline aluminosilicate and aluminometallosilicate, various zeolites such as metallosilicate can be used, especially pentasil-type aluminosilicate or Metallosilicates are preferred. Examples of the metal contained in the metallosilicate include metal elements such as titanium, gallium, zirconium, and hafnium, and among them, gallium is preferable.

As the hydration reaction method, for example, a commonly used method such as a fluidized bed system, a stirring batch system or a continuous system is employed. In the case of the continuous system, both a catalyst-filled continuous flow system and a stirring tank flow system can be used. The reaction temperature is advantageously low in terms of equilibrium of cyclohexene hydration reaction and increase in side reactions, and high in terms of reaction rate. The optimum temperature is usually 50 to 250 ° C., though it varies depending on the properties of the catalyst.

Cyclohexanol obtained by the above-mentioned hydration reaction of cyclohexene usually contains a trace amount of methylcyclopentanol. According to the study by the present inventors, surprisingly, this methylcyclopentanol
It was found that even if a trace amount remained in cyclohexanol, when the cyclohexanol was used to finally produce ε-caprolactam, the quality of the product ε-caprolactam was significantly impaired. As one of the causes of this, it is conceivable that the methylcyclopentanol remaining in cyclohexanol becomes methylcyclopentanone oxime in the process of the oximation reaction, and is mixed into the product ε-caprolactam. This methylsilopentanone oxime is converted to methylvalerolactam by Beckmann rearrangement, and it is known that methylvalerolactam is a component that deteriorates the color of 6-nylon obtained by polymerizing ε-caprolactam. . It is difficult to separate these methylcyclopentanone oxime and methylvalerolactam from cyclohexanone oxime or ε-caprolactam. Therefore, the present invention is characterized in that methylcyclopentanol in cyclohexanol is supplied to the dehydrogenation reaction at 200 ppm or less, preferably 150 ppm or less.

In the present invention, 2-methylcyclopentanol and 3-methylcyclopentanol are collectively referred to as methylcyclopentanol. The reason why methylcyclopentanol is contained in cyclohexanol is presumed to be that a rearrangement reaction occurs during the hydration reaction of cyclohexene to produce methylcyclopentanol which is an isomer of cyclohexanol.

The content of methylcyclopentanol is 20
As a method of obtaining cyclohexanol of 0 ppm or less, the content of methylcyclopentanol is 200 pp by carefully selecting raw materials, catalysts, reaction conditions and the like used for the hydration reaction.
m or less, or cyclohexanol containing a large amount of methylcyclopentanol may be purified by distillation or the like.

In the present invention, cyclohexanol having a methylcyclopentanol content of 200 ppm or less is subjected to a dehydrogenation reaction to obtain cyclohexanone. The dehydrogenation reaction of cyclohexanol may be carried out by any conventionally known method, but generally, in the presence of a dehydrogenation catalyst, 20
It is carried out by heating to 0 to 750 ° C. Examples of the dehydrogenation catalyst include copper-chromium oxides and copper-zinc oxides. This reaction is an equilibrium reaction, and the product is obtained as a mixture of cyclohexanone and cyclohexanol. Therefore, cyclohexanone and cyclohexanol are separated by distillation or the like, and the recovered cyclohexanol is recycled to the dehydrogenation reaction again.

The cyclohexanone thus obtained is reacted with hydroxylamine under known reaction conditions to give cyclohexanone oxime. Since hydroxylamine is an unstable compound by itself, it is usually used in the form of hydroxylammonium sulfate or nitrate. For example,
Cyclohexanone is reacted with a hydroxylammonium salt in an aqueous solution or a non-aqueous solution to give cyclohexanone oxime.

Then, the cyclohexanone oxime undergoes Beckmann rearrangement into ε-caprolactam by a known method. For example, Beckmann rearrangement in concentrated sulfuric acid or fuming sulfuric acid to form ε-caprolactam sulfate, followed by neutralization with an alkali, cyclohexanone oxime in the presence of a solid catalyst in a gas phase or liquid phase, Beckmann rearrangement, liquid Examples include a method in which Beckmann rearrangement is performed in a state where the catalyst is uniformly dissolved in the phase. In either method, the obtained ε-caprolactam is usually purified by distillation, crystallization or the like to obtain a product.

[0015]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the examples as long as the gist thereof is not exceeded. The amount of methylcyclopentanol used in the examples was determined by gas chromatography using a capillary column.

Example 1 [Hydration reaction of cyclohexene] In an autoclave equipped with a stirring blade, gallium silicate (Si / Ga atomic ratio = 25/1) as a catalyst, 15 parts by weight of cyclohexene, and 30 parts of water.
1 part by weight and 10 parts by weight of a hydration reaction catalyst were added and reacted at 120 ° C. for 1 hour under a nitrogen atmosphere to obtain a cyclohexanol mixture. This cyclohexanol mixture contains methylcyclopentanol at 350 p for cyclohexanol.
It contained pm. The yield of cyclohexanol is 10.
It was 8%.

[Purification of cyclohexanol] The cyclohexanol mixture obtained in the above reaction was distilled in 10 stages to purify cyclohexanol. The purified cyclohexanol contained 50 ppm of methylcyclopentanol with respect to cyclohexanol.

[Dehydrogenation of cyclohexanol] The above-mentioned purified cyclohexanol was vaporized, and a tubular reactor filled with a copper-zinc catalyst set at 250 ° C was charged with a reaction pressure of 0.07 MPa and a GHSV (gas space velocity). ) 2.4 hr
^-1 was supplied to carry out the dehydrogenation reaction. The yield of cyclohexanone was 60%.

[Production of cyclohexanone oxime] A 45% hydroxylamine sulfate aqueous solution was maintained at 85 ° C in a jacketed stirred tank, and the above cyclohexanone was added dropwise. At this time, ammonia water was added dropwise at the same time so that the reaction solution had a pH of 4.0 to 4.5. After the completion of the addition of cyclohexanone, the mixture was stirred for 30 minutes to complete the reaction. After standing, the oil phase was collected as cyclohexanone oxime. Water contained in cyclohexanone oxime was dehydrated under reduced pressure.

[Beckmann rearrangement reaction] The above-mentioned cyclohexanone oxime and 25% fuming sulfuric acid (orium) were put in a jacketed stirring tank, and the Beckmann rearrangement solution had an acidity of 57%.
The reaction was carried out at a reaction temperature of 80 to 85 at a ratio such that the free SO ₃ concentration was 7.5% and the residence time was 1 hour.
The Beckmann rearrangement reaction was carried out while stirring and cooling so that the temperature became ℃.

The Beckmann rearrangement solution thus obtained has a temperature of 70 ° C.
Then, the pH was adjusted to 7.0 to 7.5 using ammonia water and neutralized. Next, the neutralized Beckmann rearrangement solution was extracted with benzene in an amount such that the concentration of ε-caprolactam was 18% by weight, assuming that all the cyclohexanone oxime was rearranged to ε-caprolactam. For extraction, add neutralizing solution and benzene to a separating funnel, shake for 10 minutes,
After standing for 5 minutes, only the oil phase was collected. The aqueous phase was extracted twice more with benzene. Then, benzene was distilled off by a conventional method to obtain a crude lactam.

Finally, the crude lactam was purified by distillation.
Distillation was carried out after adding an appropriate amount of 25% caustic soda to the crude lactam, then the initial distillation was 10% by weight, the main distillation was 80% by weight, and the residual residue was 10% by weight.
Samples were divided into three parts and the main fraction was subjected to quality evaluation.

[Method for evaluating quality of ε-caprolactam] The quality of the obtained ε-caprolactam was evaluated by the following method. 1 g of PZ (permanganate value) ε-caprolactam sample was dissolved in 100 ml of water,
Add 1 ml of 0.01N potassium permanganate solution to this.
Was added and stirred, and the comparative standard solution (cobalt chloride (CoCl ₂
・ 6H ₂ O) 3.000 g and copper sulfate (CuSO ₄・ 5H ₂
O) 2.000 g diluted with water to 1000 ml)
The number of seconds until it becomes the same color as.

PM (permanganate consumption) A solution of 100 g of ε-caprolactam dissolved in 150 ml of 8M sulfuric acid was titrated with a 0.1N potassium permanganate aqueous solution to measure the consumption of potassium permanganate,
It is expressed in units of ml / kg · ε-caprolactam.

VB (volatile base) 30 g of ε-caprolactam was dissolved in 400 ml of a 2N aqueous solution of caustic soda and boiled for 1 hour, and the generated decomposition gas and distilled water were added to 500 ml of demineralized water in which 4 ml of a 0.02N hydrochloric acid aqueous solution was dissolved. Let it blow. Then, this demineralized water was titrated with 0.1N caustic soda, and the amount of decrease in hydrochloric acid was converted to ammonia. The results are shown in Table 1.

Comparative Example 1 In the purification of cyclohexanol of Example 1, the same procedure as in Example 1 was carried out except that the distillation was simple distillation. The content of methylcyclopentanol to cyclohexanol in cyclohexanol subjected to dehydrogenation reaction is 300 ppm.
Met. Table 1 shows the quality evaluation results of ε-caprolactam.
Shown in

Example 2 Methylcyclopentanol 1 was added to purified cyclohexanol.
The same procedure as in Example 1 was performed, except that the amount of methylcyclopentanol added to the cyclohexanol in the cyclohexanol was changed to 150 ppm. ε-
Table 1 shows the results of quality evaluation of caprolactam.

Comparative Example 2 Purified cyclohexanol and methylcyclopentanol 2
The same procedure as in Example 1 was carried out except that the amount of methylcyclopentanol added to the cyclohexanol in the cyclohexanol was adjusted to 250 ppm by adding 00 ppm. ε-
Table 1 shows the results of quality evaluation of caprolactam.

[0029]

[Table 1]

[0030]

Industrial Applicability According to the method of the present invention, it is possible to inexpensively produce ε-caprolactam which is not inferior to the conventional quality and is industrially useful.

Claims (1)

[Claims] 1. A method for producing ε-caprolactam by cyclohexanol obtained by hydration reaction of cyclohexene to cyclohexanone by dehydrogenation reaction, then reaction with hydroxylamine to cyclohexanone oxime, and further Beckmann rearrangement to produce ε-caprolactam. A method for producing ε-caprolactam, characterized in that the content of methylcyclopentanol contained in cyclohexanol used for elementary reaction is 200 ppm or less.