JPH0987247A - Production of epsilon-caprolactam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce ε-caprolactam of quality not inferior to that of a conventional product at a low cost by using cyclohexene as a raw material. SOLUTION: Methylcyclopentanones contained in cyclohexanone used for reaction with hydroxylamine are regulated to <=400ppm in the method for producing ε-caprolactam by converting cyclohexanol obtained by the hydrating reaction of cyclohexene into cyclohexanone by dehydrogenating reaction, then reacting the resultant cyclohexanone with hydroxylamine, providing cyclohexanone oxime and further carrying out the Beckmann rearrangement of the prepared cyclohexanone oxime.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing ε-caprolactam using cyclohexene as a starting material. Specifically, cyclohexene is converted into cyclohexanol by a hydration reaction, cyclohexanol is converted into cyclohexanone by a dehydrogenation reaction, then cyclohexanone is converted into cyclohexanone oxime by an oximation reaction, and finally cyclohexanone oxime is produced by Beckmann rearrangement reaction to produce ε-caprolactam. Regarding the method.

[0002]

2. Description of the Related Art ε-Caprolactam is mainly produced by oxidizing cyclohexanone and subjecting the produced cyclohexanone oxime to Beckmann rearrangement. This cyclohexanone oxime is generally produced by reacting cyclohexanone with hydroxylamine. Target.

Conventionally, as a method for producing cyclohexanone as a raw material for producing ε-caprolactam, cyclohexane is oxidized with molecular oxygen to produce a mixture of cyclohexanol and cyclohexanone, and cyclohexanol and cyclohexanone are separated by distillation and separated. The method of converting cyclohexanol to cyclohexanone by dehydrogenation is the most commonly used method industrially, and a method of hydrogenating and dehydrogenating phenol to cyclohexanone is also known.

On the other hand, recently, as a method for industrially producing cyclohexanol, cyclohexene is used as a solid acid catalyst,
In particular, a method of hydrating in the presence of a zeolite catalyst has received attention. Although there have been many reports on such a method since the 1940s, production on an industrial scale has only recently been carried out (Chemical Economy, 19
See the March 1993 issue, pages 40-45).

[0005]

The method for producing cyclohexanol by hydrating cyclohexene is a cost-effective method and is one of the preferable methods for producing cyclohexanol. Therefore, it is considered to be industrially useful if the cyclohexanol produced by the method can be used as a raw material for producing ε-caprolactam.Therefore, the present inventors have used cyclohexanol obtained by the production method. Examination of the production of ε-caprolactam revealed that, unlike ε-caprolactam produced from cyclohexanol obtained by other methods, there is a peculiar problem in the present production method in terms of quality.

Generally, when producing ε-caprolactam using cyclohexanol obtained from the hydration reaction of cyclohexene as a raw material, it is necessary to go through a plurality of steps and various by-products are produced. It is extremely difficult to determine which by-product of which manufacturing process should be focused on.

[0007]

Means for Solving the Problems As a result of intensive studies on the above problems, the present inventors have found that, in ε-caprolactam starting from cyclohexene, specific impurities in cyclohexanone, which is a starting material in the oximation reaction step, The inventors have found that the above problems can be solved by controlling the amount in particular, and have reached the present invention.

That is, the gist of the present invention is that cyclohexanol obtained by the hydration reaction of cyclohexene is converted into cyclohexanone by a dehydrogenation reaction, and then reacted by an oximation reaction to give cyclohexanone oxime, and further Beckmann rearrangement is carried out to obtain ε-caprolactam. In the method for producing γ, methylcyclopentanones contained in cyclohexanone subjected to the reaction with hydroxylamine is 400 ppm or less.
-In the method of manufacturing caprolactam.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. 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, sulfuric acid,
The reaction is carried out using hydrochloric acid, phosphoric acid, aromatic sulfonic acid or the like, but it is preferable to use a solid acid catalyst. As the solid acid catalyst, zeolite, ion exchange resin and the like are usually mentioned, and zeolite is particularly preferable. As the zeolite, various zeolites such as crystalline aluminosilicate, aluminometallosilicate, and metallosilicate can be used, and pentasil-type aluminosilicate or metallosilicate is particularly preferable. Examples of the metal contained in the metallosilicate may include metal elements such as titanium, gallium, iron, chromium, zirconium, and hafnium.
Of these, gallium is preferable.

The hydration reaction is carried out by a commonly used method such as a fluidized bed system, a stirred batch system or a continuous system. In the case of the continuous system, both a catalyst-filled continuous flow system and a stirring tank flow system are possible. The reaction temperature is advantageously low in terms of equilibrium of cyclohexene hydration and increase in side reactions, and high in terms of reaction rate. The optimum temperature varies depending on the properties of the catalyst, but is usually selected from the range of 50 to 250 ° C, preferably 80 to 200 ° C.

The cyclohexanol obtained is subjected to a dehydrogenation reaction to give cyclohexanone. The dehydrogenation reaction of cyclohexanol may be carried out by any conventionally known method, but generally, it is usually 150 to 7 in the presence of a dehydrogenation catalyst.
It is carried out by heating to 50 ° C, preferably 200 to 450 ° C. Examples of the dehydrogenation catalyst include metals such as nickel, cobalt, platinum, zinc, calcium, chromium and copper, and oxides thereof. Further, a mixture thereof may be used. Preferably, zinc oxide, calcium oxide,
It is a metal oxide catalyst such as chromium oxide and copper oxide. Furthermore,
These catalysts may be supported on a carrier such as alumina. This reaction is an equilibrium reaction, and since the product is obtained as a mixture of cyclohexanone and cyclohexanol, cyclohexanone and cyclohexanol are separated by distillation or the like, and the separated cyclohexanol is reused as a raw material for the dehydrogenation reaction.

The cyclohexanone thus obtained contains a small amount of methylcyclopentanones, a component that has not been noticed in the past. It was found that this impurity reacts as the lactamization process progresses and changes into a substance that is much more difficult to separate than ε-caprolactam, so that it is mixed in the product ε-caprolactam and the quality is significantly impaired.

Therefore, in the method for producing ε-caprolactam using cyclohexene as a starting material of the present invention, methylcyclopentanones contained therein are 400 ppm or less, preferably 300 ppm or less, as cyclohexanone to be subjected to oximation. , Particularly preferably 5
It is characterized by using 100 ppm. The amount of methylcyclopentanones used in the present invention is 2
-The total amount of methylcyclopentanone and 3-methylcyclopentanone. Methylcyclopentanones are 400p
In the case where ε-caprolactam is produced by carrying out a post-process using cyclohexanone exceeding pm as a raw material, impurities derived from methylcyclopentanones cannot be removed in the post-process as described above, so that a satisfactory quality is obtained. It becomes difficult to obtain ε-caprolactam. Note that ε
From the viewpoint of the quality of caprolactam, the smaller the content of methylcyclopentanones in cyclohexanone is, the more desirable it is.However, the labor of the separation operation of methylcyclopentanones and the quality target of ε-caprolactam are Depending on the relationship, the content of methylcyclopentanones may be set appropriately, and normally it is not necessary to completely remove methylcyclopentanones.

400 ppm of methylcyclopentanones
As a method of obtaining cyclohexanone of m or less, 400 ppm of methylcyclopentanone is selected by carefully selecting the raw material, catalyst and reaction conditions used for the dehydrogenation reaction of cyclohexanol.
The following may be used, or cyclohexanone obtained by the dehydrogenation reaction may be purified by distillation or the like.

Further, it is presumed that the methylcyclopentanones are produced by dehydrogenating a small amount of methylcyclopentanols by-produced by the rearrangement reaction when hydrating cyclohexene to cyclohexanol. Therefore, reducing the amount of methylcyclopentanols in cyclohexanol to be subjected to the dehydrogenation reaction in advance is also an effective method. The content of methylcyclopentanols in cyclohexanol is preferably 200 ppm or less, particularly preferably 150 ppm or less. In this case, the methylcyclopentanols mean the total amount of 2-methylcyclopentanol and 3-methylcyclopentanol.

Cyclohexanone used for the oxime-forming reaction is cyclopentanecarbaldehyde.
It is preferable to use one of 0 ppm or less. By using such cyclohexanone, higher quality ε-caprolactam can be produced. In addition, in order to produce high quality ε-caprolactam,
The cyclohexanone used for oxime formation usually has a cyclohexanol content of 1,000 which is an unreacted raw material in distillation or the like.
It is desirable that the content be less than or equal to ppm, preferably less than or equal to 600 ppm.

Cyclohexanone having a methylcyclopentanone content of 400 ppm or less is oxime-formed under known reaction conditions and reacted to give cyclohexanone oxime. Regarding the method of oxime formation,
React with hydroxylamine to give cyclohexanone oxime. Since hydroxylamine is an unstable compound by itself, it is usually used in the form of hydroxylamine sulfate or nitrate. For example, cyclohexanone is reacted with hydroxylamine sulfate in an aqueous solution or a non-aqueous solution. The oximation is not limited to the reaction with hydroxylamine, but a method of reacting cyclohexanone with nitric oxide and hydrogen in the presence of a platinum group metal catalyst (see US Pat. No. 4,929,756),
Cyclohexanone oxime may be obtained by a method of reacting cyclohexanone with ammonia in the presence of hydrogen peroxide (see US Pat. No. 4,745,221).

Then, the above cyclohexanone oxime undergoes Beckmann rearrangement to give ε-caprolactam by a known method. For example, Beckmann rearrangement in concentrated sulfuric acid or fuming sulfuric acid to give ε-caprolactam sulfate, followed by neutralization with an alkali, cyclohexanone oxime in the presence of a solid acid 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. When cyclohexanone oxime is brought into contact with sulfuric acid or fuming sulfuric acid, the amount of sulfuric acid or fuming sulfuric acid to cyclohexanone oxime is usually 1.0 to 2.0 in molar ratio. Usually, it is preferable to contact with fuming sulfuric acid. The concentration of free sulfur trioxide in fuming sulfuric acid is usually 1 to 30% by weight. The reaction temperature for Beckmann rearrangement is usually 60 to 130 ° C., preferably 70 to 100 ° C., but lower temperatures tend to yield better yields. This reaction is an exothermic reaction and normally heat is removed, but this can be performed by externally circulating the reaction solution and / or by providing a jacket with cooling water inside. The Beckmann rearrangement can be performed in one or more stages. In addition, the reaction solution after Beckmann rearrangement is usually
The quality of decomposing impurities can be improved by performing heat treatment at a temperature of 0 to 200 ° C. for about 0.1 to 10 hours. Ε obtained by any of the above methods
-Caprolactam is purified by distillation, crystallization, etc. to obtain a product.

[0019]

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 components such as methylcyclopentanones in cyclohexanone and methylcyclopentanols in methyl or cyclohexanol were quantified by gas chromatography using a capillary column.

Example 1 (1) Hydration Reaction of Cyclohexene A gallium silicate (SiO ₂ / Ga ₂ O ₃ atomic ratio = 50/1), 15 parts by weight of cyclohexene and 30 parts by weight of water were used as a catalyst in an autoclave equipped with a stirring blade. Then, 10 parts by weight of the hydration reaction catalyst was added and reacted at 120 ° C. for 1 hour under a nitrogen atmosphere to obtain a cyclohexanol mixture. The yield of cyclohexanol was 10.8%. (2) Purification of cyclohexanol The cyclohexanol mixture obtained above was purified by a 10-stage rectification column. This purified cyclohexanol contained 500 ppm of methylcyclopentanols.

(3) Dehydrogenation of cyclohexanol The purified cyclohexanol was vaporized, and a tubular reactor filled with a copper oxide-chromium oxide catalyst set at 250 ° C. was charged with a reaction pressure of 0.17 MPa and GHSV ( Gas space velocity) was supplied at 2.4 hr ⁻¹ to carry out the dehydrogenation reaction. The yield of cyclohexanone was 60%. (4) Purification of cyclohexanone The obtained reaction liquid was purified by the following distillation operation so that the purity of cyclohexanone was 99.5% or higher. First column: 30 column trays, batch distillation with a reflux ratio of 20 to remove low boiling components. Second tower: Cyclohexanone is purified by continuous distillation with 40 trays and a reflux ratio of 10. Third tower: Purification of cyclohexanone is performed by batch distillation of 30 towers. In the purified cyclohexanone obtained by the above method, 2
It contained 5 ppm of methylcyclopentanone, 31 ppm of 3-methylcyclopentanone, and 5 ppm of cyclopentanecarbaldehyde.

(5) Production of cyclohexanone oxime A 45% hydroxylamine sulfate aqueous solution charged in a stirring tank with a jacket was heated to 85 ° C., and purified cyclohexanone was added dropwise. At this time, the pH of the reaction solution is 4.0 to
Ammonia water was added dropwise at 4.5 at the same time. After the addition of cyclohexanone was completed, in order to complete the reaction, an excess of 45% hydroxylamine sulfate aqueous solution was further added, and stirring was continued for 30 minutes, after which it was allowed to stand and separate to collect the oil phase as cyclohexanone oxime. Water contained in cyclohexanone oxime was dehydrated under reduced pressure.

(6) Beckmann rearrangement The Beckmann rearrangement solution has a acidity (as converted to sulfuric acid) of 57% and a free SO ₃ concentration of 7.5%, and a residence time in the reactor of 1 hour. So that cyclohexanone oxime and 25% fuming sulfuric acid (orium) were simultaneously added dropwise to a jacketed stirring tank. At this time, in order to suppress local heat generation, stirring is performed at a stirring speed of 100 rpm or more,
Also, cooling water is flown through the jacket to increase the reaction temperature to 70-1.
Maintained at 00 ° C.

(7) SO ₃ Treatment The Beckmann rearrangement solution thus obtained was transferred to a stirring tank with a jacket (500 ml), and the SO ₃ concentration was adjusted to 7 to 7.5.
%, The mixture was treated at a treatment temperature of 90 to 125 ° C. for 2 hours while stirring at a stirring speed of 300 rpm or more to obtain a SO ₃ treatment liquid. (8) Post-treatment The obtained SO ₃ treatment liquid was neutralized with aqueous ammonia. Neutralization reaction is performed by passing warm water through a jacketed stirring tank at a neutralization temperature of 7
It carried out at 0 degreeC and pH 7.0-7.5. Subsequently, the neutralized solution was extracted with benzene three times in total. For the extraction, the neutralizing solution and benzene were placed in a separating funnel, shaken for 10 minutes, allowed to stand for 5 minutes, only the oil phase was collected, and the aqueous phase was extracted again with benzene. At this time, the amount of benzene used is the theoretical amount of ε-
The caprolactam concentration was adjusted to 15 to 20% by weight. The extract thus obtained was stirred and mixed at 40 ° C., and then allowed to stand for 30 minutes to separate the aqueous phase again. An appropriate amount of caustic soda was added to the obtained ε-caprolactam-benzene solution, and benzene was distilled off under reduced pressure to obtain crude ε-caprolactam. The distillation was divided into three parts of 10% by weight for the initial distillation, 80% by weight for the main distillation, and 10% by weight for the bottom of the distillation. The results are shown in Table 1.

(9) Quality evaluation method for ε-caprolactam The quality of the obtained ε-caprolactam was evaluated according to the following four standards. Table 1 shows the obtained results. 1 g of PZ (potassium permanganate) ε-caprolactam was dissolved in 100 ml of water,
Add 1 ml of 0.01N potassium permanganate solution to this.
Was added, and the mixture was stirred, and a comparative standard solution (cobalt chloride (CoCl
₂ · 6H ₂ O) 3.0g and copper sulfate (CuSO ₄ · 5H ₂ O)
Time (sec) until the same color as 2.00 g diluted to 1000 ml with water). 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 2N caustic soda aqueous solution and boiled for 1 hour, and the generated decomposition gas and distilled water were blown into 500 ml of demineralized water in which 4 ml of 0.02N hydrochloric acid aqueous solution was dissolved. Let Then, this demineralized water was titrated with 0.1N caustic soda, and the amount of decrease in hydrochloric acid was converted to ammonia. Ammonium Sulfate Quality Adjust the pH of ammonium sulphate water to 5.2 with 8M sulfuric acid. 5 ml of the prepared sample is diluted to 500 ml, and this diluted solution is diluted to 10 ml.
It is put in a quartz cell of mm and the absorbance at a wavelength of 255 nm is measured. Comparison target: Demineralized water, ammonium sulfate quality = absorbance x dilution rate

Example 2 The cyclohexanol of (2) was not rectified, and the total amount of low-boiling components in cyclohexanone was 0.12% in the cyclohexanone purification step of (4).
Example 1 was repeated except that the distillation conditions for the first column were changed and the distillation for the third column was not performed. Table 1 shows the obtained results. The purified cyclohexanone obtained by the above method contained 110 ppm of 2-methylcyclopentanone, 180 ppm of 3-methylcyclopentanone, and 30 ppm of cyclopentanecarbaldehyde.

Comparative Example 1 In the cyclohexanone purification step of (4), the same procedure as in Example 2 was carried out except that the distillation in the first column was not performed. The obtained results are shown in Table-2. The purified cyclohexanone obtained by the above method contained 210 ppm of 2-methylcyclopentanone, 280 ppm of 3-methylcyclopentanone, and 87 ppm of cyclopentanecarbaldehyde.

Comparative Example 2 The same as Example 1 except that cyclohexanol obtained by the oxidation of cyclohexane was distilled and refined in a 30-stage rectification column at a reflux ratio of 30 to remove low boiling point components by 27%. To assess the quality of ε-caprolactam. Table 2 shows the results. In the purified cyclohexanone obtained by the above method, 2-methylcyclopentanone, 3-
Neither methylcyclopentanone nor cyclopentanecarbaldehyde was detected.

Comparative Example 3 The same as Example 1 except that 12% of low boiling point components were removed by distillation purification using a cyclohexanol obtained by oxidation of cyclohexane at a reflux ratio of 30 in a 30-stage rectification column. To assess the quality of ε-caprolactam. Table 2 shows the results. In addition, in the cyclohexanone obtained by the above method, 2-methylcyclopentanone, 3
Neither methylcyclopentanone nor cyclopentanecarbaldehyde was detected.

[0031]

[Table 1]

[0032]

[Table 2]

From Tables 1 and 2, it is possible to obtain higher quality ε-caprolactam by using a cyclohexanone having a methylcyclopentanone content of 400 ppm or less and a cyclopentanecarbaldehyde content of 50 ppm or less. it can. It is also understood that the quality of ammonium sulfate produced as a by-product is improved at the same time. It can also be seen that the effect of using cyclohexanone containing less specific impurities is particularly remarkable when cyclohexene is used as the starting material. It should be noted that the quality of ammonium sulfate generally correlates with the quality of ε-caprolactam. That is, if the quality of ammonium sulfate is poor, if it is improved, the quality of ε-caprolactam is relatively reduced. In other words, even if the quality evaluation of ε-caprolactam itself is the same, if the ammonium sulfate quality is poor, it is judged that the quality of ε-caprolactam is not good as a whole.

Example 3 The purified cyclohexanol obtained in (2) was further added with 30
Cyclohexanol purified to a plate column extraction purity of 99.99% or more was subjected to dehydrogenation, and commercially available 2-methylcyclopentanone and 3-methylcyclopentanone were added to cyclohexanone purified in (4). The same procedure as in Example 1 was carried out except that the addition was adjusted so that the total amount was 380 ppm at a ratio of about 1: 1. The obtained results are shown in Table-3. Comparative Example 4 The procedure of Example 3 was repeated, except that the concentration of the methylcyclopentanones in cyclohexanone was adjusted to 1000 ppm. The obtained results are shown in Table-3.

[0035]

[Table 3]

From Table 3, even if highly purified cyclohexanone is used as a raw material, if a slight amount of methylcyclopentanone is contained in the cyclohexanone, the quality of ε-caprolactam, especially ammonium sulfate quality You can see that it is adversely affecting.

Example 4 The purified cyclohexanol obtained in (2) was further added with 30
Cyclohexanol purified to a plate tray extraction purity of 99.99% or more was subjected to dehydrogenation, and cyclohexanone purified in (4) was adjusted to 250 ppm of commercially available cyclopentanecarbaldehyde. Example 1
I went the same way. The obtained results are shown in Table 4. Example 5 The procedure of Example 4 was repeated, except that the concentration of cyclopentanecarbaldehyde in cyclohexanone was adjusted to 350 ppm. The obtained results are shown in Table 4.

[0038]

[Table 4]

Table 4 shows that cyclopentanecarbaldehyde in cyclohexanone also adversely affects the quality of ε-caprolactam, especially VB. Example 6 (1) Hydration Reaction of Cyclohexene A gallium silicate (Si / Ga atomic ratio = 25/1) as a catalyst in an autoclave equipped with a stirring blade, 15 parts by weight of cyclohexene, 30 parts by weight of water, and 10 parts by weight of a hydration reaction catalyst. Parts were added and reacted at 120 ° C. for 1 hour under a nitrogen atmosphere to obtain a cyclohexanol mixture. This cyclohexanol mixture contained 350 ppm of methylcyclopentanols with respect to cyclohexanol. The yield of cyclohexanol was 10.8%.

(2) Purification of cyclohexanol The cyclohexanol mixture obtained above was purified by a 10-stage rectification column. The purified cyclohexanol contained 50 ppm of methylcyclopentanols. (3) Dehydrogenation reaction of cyclohexanol The purified cyclohexanol was vaporized, and a tubular reactor filled with a copper oxide-zinc oxide catalyst set at 250 ° C was charged with a reaction pressure of 0.17 MPa and GHSV (gas space velocity). ) 2.4 hr ⁻¹ was supplied to perform dehydrogenation reaction, and cyclohexanone was separated and obtained. The yield of cyclohexanone is 60%, and the methylcyclopentanones are 80 pp
It contained m.

(4) Production of cyclohexanone oxime A 45% hydroxylamine sulfate aqueous solution was maintained at 85 ° C. in a jacketed stirring 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 dropwise addition of cyclohexanone, in order to complete the reaction, excess hydroxylamine sulfate aqueous solution was further added, and the mixture was stirred for 30 minutes. After standing, the oil phase was collected as cyclohexanone oxime. Water contained in cyclohexanone oxime was dehydrated under reduced pressure.

(5) Beckmann rearrangement reaction In a stirring tank with a jacket, the above cyclohexanone oxime and 25% fuming sulfuric acid (orium) were added so that the Beckmann rearrangement solution had an acidity of 57% and a free SO ₃ concentration of 7.5%. The Beckmann rearrangement reaction was carried out at such a ratio that the residence time was 1 hour, and the reaction temperature was 80 to 85 ° C. with stirring and cooling. The Beckmann rearrangement solution thus obtained had a temperature of 70 ° C. and a pH of 7.0 to 70 using ammonia water.
It was set to 7.5 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, put the neutralizing solution and benzene in a separating funnel and
After shaking for 1 minute and 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 by adding an appropriate amount of 25% caustic soda to the crude lactam, then dividing it into 3 parts of 10% by weight of initial distillation, 80% by weight of main distillation and 10% by weight of kettle residue, and the main fraction was used as product ε-caprolactam. The quality of the product was evaluated. The results are shown in Table-5.

Comparative Example 5 Among the purification of cyclohexanol of Example 6, the same procedure as in Example 6 was carried out except that the distillation was simple distillation. The cyclopentanol in cyclohexanol used for the dehydrogenation reaction was 300 ppm, and the methylcyclopentanone in cyclohexanone used for the oximation reaction was 450 ppm.
Met. The results are shown in Table-5. Example 7 Example 6 was repeated except that 100 ppm of methylcyclopentanols was added to purified cyclohexanol, and the content of methylcyclopentanols relative to cyclohexanol in cyclohexanol was 150 ppm.
The methylcyclopentanones in cyclohexanone used for the oxime formation reaction at this time were 220 ppm. The results are shown in Table-5.

Comparative Example 6 The same procedure as in Example 6 was carried out except that 200 ppm of methylcyclopentanols were added to purified cyclohexanol so that the amount of methylcyclopentanols in cyclohexanol was 250 ppm. At this time, the methylcyclopentanones in cyclohexanone subjected to the oxime formation reaction were 410
It was ppm. The results are shown in Table-5.

[0045]

[Table 5]

Table 5 shows that methylcyclopentanols in cyclohexanol also adversely affect the quality of ε-caprolactam.

[0047]

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, using cyclohexene as a starting material, and is industrially useful.

Front page continued (72) Inventor Toshio Uchibori 1-1, Kurosaki Shiroishi, Hachimansai-ku, Kitakyushu, Fukuoka Prefecture Mitsubishi Chemical Corporation Kurosaki Plant (72) Inventor Hidefumi Sano 1-1, Kurosaki Shiroishi, Hachimansai-ku, Kitakyushu, Fukuoka Prefecture Mitsubishi Kurosaki Plant, Chemical Co., Ltd.

Claims (6)

[Claims] 1. A method for producing ε-caprolactam by cyclohexanol obtained by a hydration reaction of cyclohexene to cyclohexanone by a dehydrogenation reaction and then to cyclohexanone oxime by an oximation reaction, and further producing Beckmann rearrangement to produce ε-caprolactam. The method for producing ε-caprolactam is characterized in that the content of methylcyclopentanones contained in cyclohexanone used in step 1 is 400 ppm or less. 2. The method according to claim 1, wherein a solid acid catalyst is used in the hydration reaction of cyclohexane. 3. The method according to claim 1, wherein a zeolite catalyst is used in the hydration reaction of cyclohexane. 4. The method according to claim 1, wherein cyclohexanone is oxime-ized by reacting it with hydroxylamine. 5. The method according to claim 1, wherein cyclohexanone oxime is subjected to Beckmann rearrangement reaction in sulfuric acid or fuming sulfuric acid to obtain ε-caprolactam sulfate. 6. The method according to claim 1, wherein the cyclohexanol in cyclohexanone used for the oximation reaction is 1000 ppm or less.