JPH08176102A - Production of epsilon-caprolactam - Google Patents

Abstract

PURPOSE: To provide the method for producing the ε-caprolactam useful on industry, enabling to produce the ε-caprolactam not inferior to the conventional quality at a low cost. CONSTITUTION: The method for producing the ε-caprolactam by hydrating cyclohexene, subjecting the obtained cyclohexanol to a dehydrogenation reaction, reacting the obtained cyclohexanone with hydroxylamine and subsequently subjecting the obtained cyclohexanone oxime to a Beckmann rearrangement, is characterized by reducing indene compounds contained in the cyclohexanol fed to the dehydrogenation reaction to <=15ppm.

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 of ε-caprolactam, is first a method of oxidizing cyclohexane with molecular oxygen to produce a mixture of cyclohexanol and cyclohexanone, and further dehydrogenating cyclohexanol in the mixture to cyclohexanone,
Alternatively, it has been industrially produced by a method of producing cyclohexanone by partially reducing phenol with hydrogen and then carrying out 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).

[0004]

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.

[0005]

Means for Solving the Problems As a result of intensive studies on the above problems, the inventors of the present invention used conventional raw materials by controlling the indenes in cyclohexanol used for dehydrogenation reaction to 15 ppm or less. The present inventors have found that ε-caprolactam, which is comparable to the ε-caprolactam produced by the above-mentioned method, can be obtained, and thus reached the present invention. That is, the gist of the present invention is
Cyclohexanol obtained by the hydration reaction of cyclohexene is converted to cyclohexanone by dehydrogenation, then reacted with hydroxylamine to cyclohexanone oxime, and further subjected to Beckmann rearrangement to produce ε-caprolactam. 15 pp of indene contained in cyclohexanol
It exists in the manufacturing method of (epsilon) -caprolactam characterized by making it m 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 hydration reaction of cyclohexene usually contains indenes as impurities. According to the study by the present inventors, surprisingly, when the indene is produced in the final production of ε-caprolactam by using the cyclohexanol even if a very small amount remains in cyclohexanol, It adversely affects the quality of the product ε-caprolactam, especially the UV value which is generally used as a quality standard item. Therefore, in the present invention, the content of indene in cyclohexanol is 1
The dehydrogenation reaction is characterized in that the concentration is 5 ppm or less, preferably 10 ppm or less.

The indenes in the present invention are indene skeletons such as indene and 2-methylindene (a 9-carbon skeleton formed from bicyclo [4,3,0], and a structure in which the 6-membered ring is an aromatic ring). Is a compound having Specific examples of the indenes in the present invention are compounds of the following formula.

[0010]

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In the formula, R ^{1 to} R ⁷ are usually each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 1 to 6 carbon atoms, a cycloalkyl group having 4 to 6 carbon atoms or a carbon number of 4 To 6 cycloalkenyl groups, preferably hydrogen or methyl groups. Indene content is 15ppm
As a method for obtaining cyclohexanol as described below, the raw materials, catalysts, reaction conditions, etc. used for the hydration reaction may be carefully selected so that the indene content is 15 ppm or less, or the indene content is high. Cyclohexanol may be purified by distillation or the like.

Cyclohexanol having an indene content of 15 ppm or less is subjected to a dehydrogenation reaction to form cyclohexanone. The dehydrogenation reaction of cyclohexanol may be carried out by any conventionally known method, but it is generally carried out by heating to 200 to 750 ° C. in the presence of a dehydrogenation catalyst. As the dehydrogenation catalyst, a copper-chromium oxide,
A copper-zinc type oxide etc. can be illustrated. 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 quantification of indenes in the examples was carried out 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, 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 contained 28 ppm in total of indene and methylindene with respect to cyclohexanol. Indenes other than indene and methylindene were not detected. The yield of cyclohexanol was 10.8%.

[Purification of cyclohexanol] Cyclohexanol was purified by subjecting the cyclohexanol mixture obtained in the above reaction to seven-stage distillation. The purified cyclohexanol contained 7 ppm in total of indene and methylindene with respect to cyclohexanol. [Dehydrogenation reaction of cyclohexanol] The 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 0.07MP.
a, GHSV (gas hourly space velocity) was supplied at 2.4 hr ⁻¹ to carry out the dehydrogenation reaction. The yield of cyclohexanone is 60%
Met.

[Production of cyclohexanone oxime] 45% hydroxylamine sulfate 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 added to a jacketed stirring tank with a Beckmann rearrangement solution having an acidity of 57% and free SO.
_The Beckmann rearrangement reaction was carried out while supplying the mixture at a ratio such that the concentration was 7.5% so that the residence time was 1 hour, and stirring and cooling the reaction temperature to 80 to 85 ° C.

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 distillate was 10% by weight, the main distillate was 80% by weight,
The residue was collected in 3 parts of 10% by weight, 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. 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 is dissolved in 400 ml of 2N caustic soda aqueous solution and boiled for 1 hour, and the generated decomposition gas and distilled water are blown into 500 ml of demineralized water in which 4 ml of 0.02N hydrochloric acid aqueous solution is dissolved. 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.

Example 2 The same procedure as in Example 1 was carried out except that cyclohexene of Example 1 was purified by 5-step distillation to obtain cyclohexene, and cyclohexanol of Example 1 was purified by simple distillation. The cyclohexanol used for the dehydrogenation reaction contained 8 ppm of indene and methylindene in total. Table 1 shows the evaluation results of ε-caprolactam. Comparative Example 1 Among 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 cyclohexanol used for the dehydrogenation reaction contained 18 ppm of indene and methylindene in total. Table 1 shows the quality evaluation results of ε-caprolactam.

Example 3 Indene was added to cyclohexanol in an amount of 3 ppm with respect to cyclohexanol, and the indene content was adjusted to 10 pp.
The same procedure as in Example 1 was performed except that m was used. Table 1 shows the quality evaluation results of ε-caprolactam. Comparative Example 2 Indene was added to cyclohexanol at 43 ppm with respect to cyclohexanol, and the content of indene was 50 p.
The same procedure as in Example 1 was carried out except that pm was used. Table 1 shows the quality evaluation results of ε-caprolactam.

[0022]

[Table 1]

[0023]

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 process for producing ε-caprolactam, characterized in that the indene contained in cyclohexanol used for elementary reaction is 15 ppm or less.