JPH09143155A - Production of epsilon-caprolactam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce the subject high-quality compound at a low cost by synthe sizing cyclohexanol from cyclohexene and water, then carrying out the dehydro genating reaction, providing cyclohexanone and subsequently conducting the Beckmann rearrangement. SOLUTION: Cyclohexanol obtained by carrying out the hydrating reaction of cyclohexene is converted into cyclohexanone according to a dehydrogenating reaction. The oximating reaction of the resultant cyclehexene is then conducted to provide cyclohexanone oxime and the Beckmann rearrangement thereof is further carried out to afford ε-caprolactam. The cyclohexanone oxime with >=50ppm impurity content according to a gas chromatographic analysis is used as that for the Beckmann rearrangement. The analysis is carried out under specific conditions such as use of a capillary column of fused silica (30cm length ×0.53mm inside diameter) having the inner wall coated with a liquid phase comprising dimethyl polysiloxane prepared by substituting 5% methyl with phenyl to 1.5μm film thickness and He as a carrier gas.

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. More specifically, it relates to a method for producing cyclohexanol by reacting cyclohexene with water, dehydrogenating cyclohexanol to give cyclohexanone, and then producing ε-caprolactam by Beckmann rearrangement.

[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, (1) cyclohexane is oxidized with molecular oxygen to produce a mixture of cyclohexanol and cyclohexanone, and cyclohexanol and cyclohexanone are separated by distillation. Then, cyclohexanol is industrially produced by a method of converting cyclohexanone to a cyclohexanone by a dehydrogenation reaction, (2) a method of partially reducing hydrogen of phenol, and a method of producing cyclohexanone by a rearrangement reaction. In recent years, a method of hydrating cyclohexene in the presence of a zeolite-based catalyst has attracted attention as a method for industrially producing cyclohexanol. Although many reports have been made about this method since the 1940s, production on an industrial scale has only recently been carried out.

[0004]

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 industrially useful if the cyclohexanol produced by this method can be used as a raw material for producing ε-caprolactam. However, there is little knowledge so far about ε-caprolactam produced via such a cyclohexene hydration reaction, and in particular, it was unclear what is the factor affecting the quality of ε-caprolactam.

[0005]

The inventors of the present invention studied the production of ε-caprolactam using the cyclohexanol obtained by the above-mentioned production method, and found that it was produced from cyclohexanol obtained by another method. It was revealed that, unlike ε-caprolactam, there is a specific problem in quality in the present production method.

By the way, regarding the quality of ε-caprolactam, there are evaluation items such as PZ. PZ is a potassium permanganate value, and is represented by the time required for adding the potassium permanganate aqueous solution to the aqueous solution of ε-caprolactam until the color becomes the same as that of the comparative standard solution. It is considered that this is due to impurities contained in a very small amount in ε-caprolactam.
Since ε-caprolactam is produced through an extremely long process as described above, various impurities are present in ε-caprolactam even if they are purified even if they are purified. In other words, various impurities are present in the product ε-caprolactam in an extremely small amount, but the quality is not expressed in absolute amounts of individual impurities, but is expressed as a collective numerical value derived from the type and amount of impurities.

The present inventors have studied factors that determine the quality of ε-caprolactam produced through the above-mentioned cyclohexene hydration reaction, and as a result, have found that it does not occur when conventional cyclohexane oxidation is used. The presence of impurities in the product, the impurities having a great influence on the PZ value, which is a quality evaluation item of ε-caprolactam, and the impurities having a boiling point close to that of the product ε-caprolactam. The inventors have found that they cannot be easily separated by the method, and that this impurity is already present in cyclohexanone oxime and it is effective to remove it by this stage, and thus arrived at the present invention.

That is, the gist of the present invention is to provide a method for producing ε-caprolactam in which cyclohexanol obtained by cyclohexene hydration reaction is converted to cyclohexanone by dehydrogenation reaction, then cyclohexanone oxime is converted by oximation reaction, and further Beckmann rearrangement is carried out, The cyclohexanone oxime used in the Beckmann reaction is cyclohexanone oxime having an impurity content of 50 ppm or less under the following gas chromatography analysis conditions, which is a method for producing ε-caprolactam.

[Gas Chromatography-Analysis Conditions] (1) Column: A liquid phase made of dimethylpolysiloxane in which 5% of methyl groups were substituted with phenyl groups on the inner wall had a film thickness of 1.
Capillary column of fused silica coated with 5 μm (2) Column size: length 30 m × inner diameter 0.53 mm (3) Column temperature: initial temperature 70 ° C., heating rate 4.0
The temperature is raised at 300 ° C./minute until it reaches 300 ° C. (4) Detection method: Hydrogen flame ionization detection method (FID) (5) Carrier gas: Helium (6) Carrier gas flow rate: The retention time (t _R1 ) of the peak of biphenyl added to the analytical sample as an internal standard substance Adjust the flow rate so that it is (18 ± 2) minutes. (7) the content of impurities: peak at a retention time of biphenyl (t _R1) of (1.15 to 1.30) times the retention time (t _R2)
Quantify the impurity peaks detected in.

[0010]

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 as a catalyst. Examples of the solid acid catalyst generally include zeolite and ion exchange resin. 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 include metal elements such as titanium, gallium, iron, chromium, zirconium, and hafnium, and among them, 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 preferably low in terms of equilibrium of cyclohexene hydration reaction 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 50 to 2
It is selected from the range of 50 ° C.

The cyclohexanol obtained is subjected to a dehydrogenation reaction to form cyclohexanone. The dehydrogenation reaction of cyclohexanol may be carried out by any conventionally known method, but generally, it is carried out in the presence of a dehydrogenation catalyst at 200 to 750.
It is carried out by heating to ℃. Examples of the dehydrogenation catalyst include copper-chromium oxides and copper-zinc oxides. 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.

Next, cyclohexanone is prepared by the above method.
Cyclohexanone oxime is formed by a known oxime-forming reaction. Regarding the method of oxime formation, cyclohexanone oxime is usually obtained by reacting with hydroxylamine. Since hydroxylamine is not a stable compound by itself, it is used in the form of hydroxylamine sulfate or nitrate, for example, to react cyclohexanone with hydroxylamine sulfate in an aqueous solution or a non-aqueous solution.
Further, 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 Cyclohexanone oxime may be obtained by a method of reacting with ammonia in the presence of hydrogen peroxide (see US Pat. No. 4,745,221).

According to the studies by the present inventors, the cyclohexanone oxime obtained by the above-mentioned method contains impurities which have not been noticed in the past, and these impurities improve the quality of the product ε-caprolactam. It was found to be one of the causes of significant loss. It is presumed that this impurity remains as it is even after the subsequent Beckmann rearrangement reaction, or that it is a decomposed product and adversely affects the quality of ε-caprolactam. This impurity is
It is not contained in cyclohexanone oxime produced from cyclohexanone obtained by conventional cyclohexane oxidation, but is a characteristic impurity in the method of the present invention via the hydration reaction of cyclohexene.

Therefore, in the present invention, the cyclohexanone oxime to be subjected to the Beckmann reaction for obtaining ε-caprolactam has an impurity content of 50 ppm or less, preferably 30 ppm or less, and particularly preferably 20 ppm or less according to the above-mentioned gas chromatography analysis conditions. The use of cyclohexanone oxime is
As a method of adjusting the impurities within such a range, a method of distilling and separating the produced cyclohexanone oxime, a method of purifying the impurities by hydrogenation, a precursor of the impurities in a dehydrogenation step which is a step before the oximation, etc. Examples include a method in which the body and the like are removed, and the amount of the above impurities in the cyclohexanone oxime after oximation is set to a specified amount or less. In addition, the above impurities were identified as 2-cyclohexyl-2-cyclohexen-1-one. That is, the impurity peak quantified under the above gas chromatography analysis conditions is a peak corresponding to 2-cyclohexyl-2-cyclohexen-1-one.

Next, the cyclohexanone oxime is subjected to Beckmann rearrangement into 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 usually heat is removed, but this can be performed by externally circulating the reaction solution and / or by providing a jacket through which cooling water is passed inside. The Beckmann rearrangement can be performed in one or more stages. In addition, the quality of decomposing impurities can be improved by subjecting the reaction solution subjected to Beckmann rearrangement to heat treatment at a temperature of 130 to 200 ° C. for about 0.1 to 10 hours. The ε-caprolactam obtained by any of the above methods is purified to a product by distillation or crystallization.

[0017]

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. Quantification of specific impurities in cyclohexanone oxime in the examples was carried out by gas chromatography.

[Gas Chromatographic Analysis Conditions] Equipment: Hewlett-Packard Gas Chromatography Equipment Column: J & W DB-5 (5 methyl groups on the inner wall)
% Fused with a phenyl group-substituted dimethylpolysiloxane liquid phase with a film thickness of 1.5 μm, fused silica capillary column), length 30 m × inner diameter 0.53 mm Column temperature: initial temperature 70 ° C. Speed 4.0 ℃ /
The temperature is raised to 300 ° C. in minutes. -Detection method: hydrogen flame ionization detection method (FID) -Carrier gas: Helium-Carrier gas flow rate: The retention time (t _R1 ) of the peak of biphenyl added to the analytical sample as an internal standard substance is (18 ± 0.1). ) Minutes, the feed pressure was 50 kPa at a column temperature of 70 ° C., the septum purge flow rate was 1.8 ml / min, and the split flow rate was 10 minutes.
It was set to ml / min. -Injection port temperature: 220 ° C-Detector temperature: 250 ° C-Sample injection amount: 1.0 μl-Impurity determination method: (1.15 to 1.30) times the retention time (t _R1 ) of the peak of biphenyl Retention time (t _R2 )
The amount of impurities was quantified from the peak area of the impurities detected in Example 2 using 2-cyclohexylcyclohexenone as a standard.

Example 1 (1) Partial Hydrogenation Reaction of Benzene 1.4 wt% of supported ruthenium catalyst, 33.9 wt% of benzene, and 6 wt% of zinc sulfate aqueous solution having a concentration of 6 wt% were used.
In the presence of 4.7% by weight, hydrogen gas was supplied from the nozzle opening at a linear velocity of 6.8 cm / sec, and the reaction pressure was 5.0 M.
Partial hydrogenation reaction of benzene was carried out at a temperature of Pa of 150 ° C. with high speed stirring. The reaction was stopped at a reaction time of 20 minutes. After separating the obtained oil phase, cyclohexene was separated and purified by extractive distillation using adiponitrile according to a known method.

(2) Hydration Reaction of Cyclohexene As a hydration catalyst, gallium silicate (Si / Ga atomic ratio = 25/1) was used. 15 parts by weight of cyclohexene, 30 parts by weight of water, and 10 parts by weight of a hydration catalyst were placed in an autoclave equipped with a stirring blade, and the mixture was reacted in a nitrogen atmosphere at 120 ° C. for 1 hour. (3) Purification of cyclohexanol The cyclohexanol mixture obtained above was purified by a 10-stage rectification column to obtain purified cyclohexanol having a purity of 99.9%.

(4) Dehydrogenation Reaction of Cyclohexanol A reaction pressure of 0.17 MPa (0.7 kg / cm ² G) was applied to a tubular reactor filled with a copper-zinc catalyst which was vaporized from purified cyclohexanol and set at 250 ° C. ), LHSV
(Liquid hourly space velocity) The dehydrogenation reaction was performed by supplying at 2.4 hr ^-1 . The yield of cyclohexanone was 60%. (5) Purification of cyclohexanone Cyclohexanone was rectified in a 30-stage rectification column (reflux ratio: 3
The low boiling point component was removed by 0) and then rectified in a 40-stage rectification column (reflux ratio 10; recovery rate 50%) to obtain purified cyclohexanone from the top of the column.

(6) Production of cyclohexanone oxime A 45% hydroxylamine sulfate aqueous solution charged in a stirring tank with a jacket was heated to 85 ° C., and the above 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 completion of the dropwise addition of cyclohexanone, stirring was continued for 30 minutes to complete the reaction, and then the mixture was allowed to stand and separated to collect an oil phase as cyclohexanone oxime. Water contained in cyclohexanone oxime was dehydrated under reduced pressure. When the cyclohexanone oxime obtained by the above method was analyzed, the impurities analyzed by the above analysis method were below the detection limit (about 0.1 ppm).

(7) Beckmann rearrangement The Beckmann rearrangement solution should have a acidity of 57% and a free SO ₃ concentration of 7.5%, and a residence time in the reactor of 1 hour. The 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 1000 rpm or more.
Cooling water is flowed through the jacket so that the reaction temperature is 70 to 100 ° C.
Maintained. (8) SO ₃ treatment The Beckmann rearrangement solution thus obtained was transferred to a jacketed stirring tank (500 ml), and the SO ₃ concentration was adjusted to 7.0.
While maintaining at 7.5%, while stirring at a stirring speed of 300 rpm or more, a treatment is performed at a treatment temperature of 90 to 125 ° C. for 2 hours, and SO
_Three treatment liquids were obtained.

(9) 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. Then, the neutralized solution was extracted with benzene. For the extraction, the neutralizing solution and benzene were placed in a separating funnel, shaken for 10 minutes, and allowed to stand for 5 minutes to collect only the oil phase, and the aqueous phase was extracted again with benzene. At this time, the amount of benzene used was adjusted so that the theoretical concentration of ε-caprolactam was 18% by weight. Thus, extraction with benzene was performed three times in total, and then benzene was distilled off by a conventional method to obtain crude ε-caprolactam. Finally the crude ε-caprolactam was purified by distillation. Distillation was carried out by adding an appropriate amount of 25% aqueous caustic soda solution to crude ε-caprolactam, then dividing into 3 parts of 10% by weight of initial distillation, 80% by weight of main distillation, and 10% by weight of bottom residue, and the main distillation was evaluated for quality. Was targeted.

(10) Quality evaluation method of ε-caprolactam The quality of the obtained purified ε-caprolactam was evaluated according to the following standards. The results are shown in Table 1. 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.
₂ · 6H ₂ O) 3.0g and copper sulfate (CuSO ₄ · 5H ₂ O)
The time until the same color as that of 2.00 g diluted with water to 1000 ml) is taken as the PZ value. The results are shown in Table 1. In addition, in the step (5), when the rectification at 40 stages and the reflux ratio of 10 was not carried out, the above-mentioned impurity concentration in the cyclohexanone oxime was 100 ppm.

Example 2 With respect to the cyclohexanone oxime obtained in the step (6) of Example 1, a fraction containing 3 to 6% of the above impurities obtained by the rectification of purified cyclohexanone in (5) was added, The PZ value was measured in the same manner as in Example 1 except that the above impurities in cyclohexanone oxime were added so as to be 40 ppm. The results are shown in Table 1.

Comparative Example 1 A fraction containing 3 to 6% of the above impurities obtained by rectifying the purified cyclohexanone of (5) with respect to the cyclohexanone oxime obtained in the step (6) of Example 1, The PZ value was measured in the same manner as in Example 1 except that the above impurities in cyclohexanone oxime were added so as to be 160 ppm. The results are shown in Table 1.

[0028]

[Table 1]

Example 3 The PZ value was measured in the same manner as in Example 2 except that the SO ₃ treatment in the step (8) of Example 2 was not performed for 2 hours. The amount of the impurities in the main fraction of the caprolactam refined thus obtained was 3 ppm. Table 2 shows the results.

Comparative Example 2 The PZ value was measured in the same manner as in Comparative Example 1 except that the SO ₃ treatment in the step (8) of Comparative Example 1 was not performed for 2 hours. The amount of impurities in the main fraction of the caprolactam refinement obtained at this time was 90 ppm. Table 2 shows the results.

[0031]

[Table 2]

From Tables 1 and 2, it can be seen that the quality of ε-caprolactam can be improved by using cyclohexanone oxime in which specific impurities in cyclohexanone oxime are in specific amounts or less.

Reference Example 1 The PZ value was measured in the same manner as in Example 1 except that the ε-caprolactam obtained in Example 1 was purified by crystallization. The results are shown in Table-3. Reference Example 2 PZ was carried out in the same manner as in Example 1 except that 2-cyclohexyl-2-cyclohexen-1-one was added to the ε-caprolactam obtained in Reference Example 1 in an amount of 1 ppm.
The value was measured. The results are shown in Table-3.

Reference Example 3 P was prepared in the same manner as in Example 1 except that 2-cyclohexyl-2-cyclohexen-1-one was added to the ε-caprolactam obtained in Reference Example 1 so that the concentration was 10 ppm.
The Z value was measured. The results are shown in Table-3. Reference Example 4 P was carried out in the same manner as in Example 1 except that 2-cyclohexyl-2-cyclohexen-1-one was added to the ε-caprolactam obtained in Reference Example 1 in an amount of 20 ppm.
The Z value was measured. The results are shown in Table-3.

Reference Example 5 P was prepared in the same manner as in Example 1 except that the amount of 2-cyclohexyl-2-cyclohexen-1-one added to the ε-caprolactam obtained in Reference Example 1 was adjusted to 30 ppm.
The Z value was measured. The results are shown in Table-3.

[0036]

[Table 3]

[0037]

Industrial Applicability According to the method of the present invention, it is possible to inexpensively produce high-quality ε-caprolactam using cyclohexene as a starting material, which is industrially useful.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kuniko Kira 1-1 Kurosaki Shiroishi, Hachiman Nishi-ku, Kitakyushu, Fukuoka Prefecture Mitsubishi Chemical Corporation Kurosaki Development Laboratory

Claims (2)

[Claims] 1. A method for producing ε-caprolactam in which cyclohexanol obtained by a hydration reaction of cyclohexene is converted into cyclohexanone by a dehydrogenation reaction and then into a cyclohexanone oxime by an oximation reaction, and cyclohexanone to be subjected to the Beckmann reaction in the method for Beckmann rearrangement. As an oxime, the content of impurities is 50p under the following gas chromatography analysis conditions.
A method for producing ε-caprolactam, which comprises using cyclohexanone oxime having a pm or less. [Gas Chromatography-Analysis Conditions] (1) Column: A liquid phase made of dimethylpolysiloxane in which 5% of methyl groups were substituted with phenyl groups on the inner wall had a thickness of 1.
Capillary column of fused silica coated with 5 μm (2) Column size: length 30 m × inner diameter 0.53 mm (3) Column temperature: initial temperature 70 ° C., heating rate 4.0
The temperature is raised at 300 ° C./minute until it reaches 300 ° C. (4) Detection method: hydrogen flame ionization detection method (FID) (5) Carrier gas: Helium (6) Carrier gas flow rate: The retention time (t _R1 ) of the peak of biphenyl added to the analytical sample as an internal standard substance Adjust the flow rate so that it is (18 ± 2) minutes. (7) the content of impurities: peak at a retention time of biphenyl (t _R1) of (1.15 to 1.30) times the retention time (t _R2)
Quantify the impurity peaks detected in. 2. A method for producing ε-caprolactam in which cyclohexanol obtained by a hydration reaction of cyclohexene is converted into cyclohexanone by a dehydrogenation reaction and then into cyclohexanone oxime by an oximation reaction, and further cyclohexanone to be subjected to the Beckmann rearrangement in the method for producing Beckmann rearrangement. A method for producing ε-caprolactam, characterized in that an oxime containing 2-cyclohexyl-2-cyclohexen-1-one in an amount of 50 ppm or less is used.