JPS6021980B2 - Caprolactam manufacturing method - Google Patents

Description

[Detailed description of the invention] The present invention is totally rich in sulfur.

The present invention relates to a method for producing caprolactam that does not produce carbon dioxide. More specifically, the present invention relates to a method for producing cabrolactam using adipic acid and adiponitrile as raw materials and substantially free from by-products. Conventionally, as an industrial production method for caprolactam, cyclohexane is converted into an oxime with hydroxylamine.
The most widely used method is to obtain cabrolactam by subjecting the generated cyclohexanone oxime to Beckmann rearrangement. However, this method has a major drawback in that ammonium sulfate is unavoidably produced as a by-product in all steps, including the hydroxylamine production step, the oxime conversion step, and the Beckmann rearrangement step. Therefore, various technological improvements are aimed at suppressing ammonium sulfate in each process. For example, in the production method of hydroxylamine, the Raschig method, in which ammonium nitrite is reduced with S02 and then hydrolyzed, has been improved. It is possible to replace the method of reducing N03- with hydrogen in an acid buffer, or to neutralize the sulfuric acid aqueous solution containing caprolactam after Beckmann rearrangement with N and extract it with citron. The creation of ammonium sulfate has been significantly suppressed by directly extracting caprolactam using caprolactam as an extractant. However, rich in ammonium sulfate. However, the disadvantage of producing cabrolactam still remains, and the development of a new method for producing cabrolactam without producing by-products has been awaited.
One method is to acetylate cyclohexanone with ketene/acetic anhydride to give cyclohexenyl acetate, then nitrate to liberate acetic acid to obtain nitrocyclohexanone, which is then hydrolyzed and reduced to aminocaproic acid in a water droplet. There is a method of producing cabrolactam by adding acid (Hakama Kosho 47-8542).

However, in this method, the ketene that acetylates cyclohexanone is regenerated from acetic acid and reused, but the regeneration cost is high, and there is no suitable citrus agent that can efficiently extract caprolactam from an aqueous solution, so it is difficult to isolate caprolactam. Removal of the yuzu agent by distillation requires extensive labor costs, and it cannot be said to be an economically superior method, so it has not yet been commercialized. Alternatively, a method of reducing cyanocyanic acid or cyanocyanic acid ester to form aminocaproic acid or aminocaproic acid ester, and then cyclizing it to form caprolactam can be considered; and cyclization to produce caprolactam, each of which has many problems and is not practical.

In other words, there is no established industrial method for producing cyanovaleric acid or cyanochelic acid ester, and there is no laboratory method for producing cyanobelargonic acid (Bg.S. Th., M, Paper 7).
Shea/valeric acid can be obtained from adipic acid by applying
The yield is low and it is not practical for industrial use.

Alternatively, a method for producing cyanocephalic acid or cyanovaleric acid ester by oxo reaction of bentenenitrile (Hakama Sekisho 52
-36625) has also been disclosed, but this also has a low yield and cannot be said to be a practical production method yet. Furthermore, another method for producing cyanide/cyanic acid is a method using an exchange reaction between adipic acid and cyanide (sleeve m.0 technique hchei
Khim. 29 3350 (1959) Unexamined Japanese Patent Publication No. 50-4
However, in an attempt to increase the conversion rate of adipic acid, if the reaction time is increased or the amount of cyanide is increased, the yield of cyanovaleric acid decreases, and instead, azibonitrile is the main product. Become a thing.

Further, even if adipic acid and adiponitrile are subjected to an exchange reaction, a sufficient yield of cyanocyanic acid has not been achieved. Another problem with this technique is the low yield of cyanide exchange-reacted with adipic acid to carboxylic acid.

Reaction to obtain adiponitrile from adipic acid by exchange reaction (
U.S. Patent No. 2,377,795, cost, price n. Chem.
716 78 (19 Iso)) mentions the yield of adiponitrile based on adipic acid, but does not mention the yield of cyanide to carboxylic acid. As a result of a confirmation experiment, only about 50% of the theoretical value of acetic acid was obtained, and the production of amides was also observed. These amides are sublimable compounds, making separation and purification of the product extremely difficult. Improved technology for the exchange reaction between adipic acid and cyanide (Tsubaki Publication No. 43-13201, J.0rg.Chem., 36 3050 (19
71)) has also been studied, but although it contributes to improving the yield of dinitrile, it is clear that it is unsuitable for the production of cyanovaleric acid.

Next, the problem with the method of producing caprolactam by cyclizing aminocaproic acid or aminocaproic acid ester is that the concentration of aminocaproic acid or amino/caproic acid ester during branization is kept low in order to suppress the polymer. This is a must. That is, a method of heating aminocaproic acid or aminocaproic acid ester in water or an organic solvent to produce caprolactam (Hakama Kosho 49-ban 73, Samurai Kosho 30-16112, Hakama Kosho 38)
-14563, Hakama Seki Sho 51-43780, ln
d. End. Chem. Process ratio s. Dev.
, 17 9 (1978)), for example, when aminocaproic acid in an aqueous solvent is heated at a low concentration, caprolactam is obtained as a dilute aqueous solution, so in order to produce caprolactam alone, a large amount of water must be removed, or It is necessary to extract using a citrus agent such as chloroform or benzene. The utility costs required to remove water or citrus chemicals are enormous. Even when an organic solvent is used, the utility costs required for solvent removal remain high, and the yield is also unsatisfactory. As a result of intensive research into a method for manufacturing caprolactam that overcomes these drawbacks and uses inexpensive raw materials, the inventors have discovered nylon 6.
The present invention was based on the discovery that cabrolactam can be obtained using adipic acid and adiponitrile, which are available at low cost as raw material precursors of No. 6, as starting materials without forming a synthetic compound.

That is, according to the present invention, adipic acid and adiponitrile are heated to perform an exchange reaction, and alcohol is directly added to the exchange reaction solution without isolating the product cyanocyanic acid from the exchange reaction solution obtained. A cyanovaleric acid ester is produced by esterification, and the cyanovaleric acid ester is reduced using a catalyst to produce an aminocaproic acid ester.The aminocaproic acid ester is heated in a polyhydric alcohol having a boiling point higher than that of caprolactam to produce caprolactam. By removing the caprolactam and circulating the distillation residue to a system that heats a polyhydric alcohol with a higher boiling point than caprolactam and an aminocaproic acid ester, caprolactam can be obtained in high yield without producing created organisms. It is possible.

More specifically, by passing through the following three steps of the present invention, economically advantageous caprolactam without by-products can be produced.

That is, the first step is to heat adipic acid and adiponitrile to cause an exchange reaction, and without isolating the product cyanovaleric acid from the nuclear reaction mixture, alcohol is directly applied to the exchange reaction solution, followed by heating. This is a process of esterification to produce shea/valerate ester. The second step is a step in which the obtained cyanocephalic acid ester is reduced to an aminocaproic acid ester in the presence of a catalyst, with or without using a solvent. In the third step, the obtained aminocaproic acid ester is heated using a polyhydric alcohol with a higher boiling point than caprolactam as a solvent, and the generated caprolactam is separated by distillation. The distillation residue containing the converted product and caprolactam oligomer (hereinafter referred to as the converted product) is circulated to the system that heats the aminocaproic acid ester, and caprolactam is produced from the converted product to caprolactam and the aminocaprolactam ester. This is the process of
In the first step of the present invention, the details of the method for producing cyanovaleric acid ester by subjecting adipic acid and adiponitrile to an exchange reaction and esterifying them with alcohol are as follows. In the exchange reaction between adipic acid and adiponitrile, the quantitative relationship can be chosen arbitrarily, but if esterification after the exchange reaction is not considered, conditions with an excess of adiponitrile are preferable. ~100 mol, preferably 1 to 70 mol, more preferably 1 to 50 mol is used.

Even if adiponitrile is used in an amount of 100 moles or more, it only increases the size of the reactor and there is no particular advantage.

The temperature in the exchange reaction is usually 100 qo or more, preferably 150 to 270 oo, more preferably 200 to 2
The temperature is 50°C.

Below 100 oo, the reaction rate is slow, and above 270°C, the conditions are only caustic and there is no advantage.

The reaction time varies depending on the quantity of adiponitrile used and the reaction temperature, but is usually 0.1 to 20 hours, preferably . It is 5 to 1q hours, more preferably 1 to 5 hours. When esterifying the exchange reaction solution with alcohol to obtain sia/valeric acid ester, it is essential to directly add alcohol to the exchange reaction solution and esterify it without using the sia/valeric acid produced in the exchange reaction alone. .

The reason for this will be explained using a diagram. Figure 1 shows adipic acid 1
Yield of cyanovaleric acid produced by heating 10 moles of adiponitrile at 230°C for the reaction time shown in the drawing Voice Ashiru)X
.oo) and its exchange reaction were esterified at 20 ppm for 2 hours with the addition of methanol.

(Yield of cyanocyanoacetate - Mugijo Hishikishikishisilkworm E Poison Tei Keyword Harmful Hayabusa E≧X・〇.

) As is clear from FIG. 1, the yield of shea/cyanic acid produced when adipic acid and adiponitrile are heated and subjected to an exchange reaction reaches a maximum of about 160% and decreases over time; By adding methanol to the exchange reaction solution and esterifying it according to the method, it is possible to obtain cyanocyanoacetate with a yield of about 190%. It is impossible to proceed with the exchange reaction and esterification simultaneously because esterification of adipic acid proceeds preferentially.

The alcohol used for esterification of the exchange reaction solution of adipic acid and adiponitrile may be any primary alcohol, such as methanol, ethanol, n-propanol,
Examples include i-propanol, n-butanol, sec-butanol, t-butanol, etc.;
Particularly preferred are methanol and ethanol.

The amount of alcohol used for esterification of the exchange reaction solution may be at least twice the mole of adipic acid used in the exchange reaction, but it is usually 2 to 400 moles, preferably 2 to 400 moles per mole of adipic acid. 200 mol, more preferably 2-1
00 moles are used.

If the amount is more than 400 moles, the reactor will become larger, which is not practical.

The reaction temperature is usually 70 to 35,000, preferably 100 to 3
0 pi 0, more preferably 150 to 230 q○ is used. Below 70 qo, the reaction rate is slow, and above 300°C, there is no benefit except that the reaction pressure increases.

The reaction time is usually 0.5 to 2 q hours, preferably 1 to 10 q hours.
It's time. It is also possible to use adipic acid monoester in place of the adipic acid used in the exchange reaction of the present invention.

In addition, the distilled residue after removing the generated cyanoacetic acid ester from the reaction solution can be converted into adiponitrile, which can be further exchange-reacted, and converted into the distilled cyanocyanoacidic acid ester. By adding the same amount of adipic acid and adibonitrile to the distilled liquid and conducting an exchange reaction and esterification, cyanoacetic acid ester can be obtained with a yield of about 200% based on the newly added adipic acid. is possible. In addition, the adipic acid gester created during esterification can be taken out of the reaction solution and removed from the system, or it can be recycled to the exchange reaction system and reused. It is particularly advantageous for the process of the invention to provide a process for producing caprolactam that does not result in formation.

In the second step of the present invention, the details of the method for producing aminocaproic acid ester by reducing the cyanoacetic acid ester obtained in the previous step using a catalyst are as follows.

Generally, nickel, palladium, platinum, rhodium, cobalt, etc. are used for reducing nitrile to primary amine, but Raney catalysts, namely Raney nickel and Raney cobalt, are preferably used, and Raney cobalt is more preferably used.
In reducing cyanovalerate ester using Raney cobalt as a catalyst, it is also possible to use ammonia as a cocatalyst. The amount of Raney cobalt in the reduction reaction is chosen arbitrarily relative to the shea/green ester.

The reaction temperature is usually 20 to 100 pm, preferably 40 to 8 pm.
Pi0 is used. When the reaction temperature is lower than 20° C., the reaction rate is slow, and when the reaction temperature is 10 pi or higher, side reactions become significant, leading to a decrease in yield. The reaction pressure is preferably 5 to 100 k9/m, preferably 10 to 50 k9/m as hydrogen pressure. If it is lower than 5k9/h, the reaction rate is slow, and if it is higher than 100k9/h, there is no advantage to the yield or reaction rate by increasing the hydrogen pressure, and only the strength of the pressure vessel is required.

As the solvent, alcohols, ethers, dioxane, etc. used for esterification of the exchange reaction solution can be used, and a solvent-free solvent may also be used. The reaction format can be either a batch process or a continuous process.
In the continuous process, most of the aminocaproic acid ester obtained after the hydrogenation reaction is circulated back into the reaction system, and the cyanocyanoacetic acid ester is reduced in a large amount of the aminocaproic acid ester. In the third step of the present invention, details of the method for producing caprolactam by heating the aminocaproic acid ester obtained in the previous step in a polyhydric alcohol having a higher boiling point than caprolactam are as follows.

That is, the significance of using a polyhydric alcohol with a higher boiling point than cabrolactam is that after heating aminocaproic acid ester in a polyhydric alcohol with a higher boiling point than cabrolactam to form caprolactam, the product, cabrolactam, is distilled off. The unconverted substance to caprolactam is present in the distillation residue in a diluted state with a polyhydric alcohol having a boiling point higher than that of caprolactam, and the distillation residue is returned to the system in which the aminocaproic acid ester is heated, thereby converting it to caprolactam. This makes it possible to obtain caprolactam quantitatively from amide/caproic acid ester.

It goes without saying that even if the distiller's clear liquid is heated alone, the unconverted substance to caprolactam will be converted to caprolactam and will be false. In this way, the polyhydric alcohol with a higher boiling point than caprolactam in the present invention refers to a polyhydric alcohol containing unconverted caprolactam as a residue after caprolactam is distilled off as described above. For example, triethylene glycol, tetraethylene glycol, polypropylene glycol, batyl alcohol, glycerin, diglycerin, bentaerystol, 1, 2, 3.
-butanetriol, 2,3,4-benthanetriol, and the like.

When a compound other than a polyhydric alcohol with a higher boiling point than caprolactam (hydrocarbons, monohydric alcohol, etc.) is used as a solvent, an insoluble polymer is formed, and when a compound with a lower boiling point than caprolactam is used as a solvent, a solvent polymer is formed. After the caprolactam is removed, the product converted to caprolactam undergoes polymerization and other alterations, making it impossible to convert it to caprolactam.

The reaction temperature for heating aminocaproic acid ester is usually 8
0 to 300 qo, preferably 100 to 280 qo, more preferably 180 to 250 qo. At temperatures above 300°C, the conditions will simply become rough and there will be little benefit in terms of yield.

The reaction time is usually 0.1 to 1q, preferably 0.5 to
5. It's G time. The concentration of aminocaproic acid ester used in the reaction is usually 0.5-3%, preferably 3-2%.
Skin t%, more preferably 5 to 15 wt%, and if the concentration is higher than 3 fins %, a large amount of non-falling polymer will be produced, which is not preferable.

When aminocaproic acid ester is heated in the above solvent to convert it into caprolactam, alcohol is produced along with it, but the reaction may proceed while removing this alcohol, or the reaction may be carried out using a closed reaction diamond bottom. The reaction may proceed while the alcohol remains in the system.

As described above, the method of the present invention is completely different from conventional caprolactam production techniques, and provides a high-yield method for producing caprolactam that uses adipic acid and adiponitrile as starting materials and does not produce any by-products. , its practical value is extremely high.

Next, the method for producing caprolactam from adipic acid and adiponitrile of the present invention will be explained in the first step based on the preferred embodiment using the flow sheet shown in the drawings as an example.
The process will be divided into three steps: a step for producing methyl cyanoacetate, a second step for producing methyl aminocaproate, and a third step for producing caprolactam.

Figure 2 shows that the exchange reaction solution of adipic acid and adiponitrile is esterified with methanol, the ring formation of methyl cyanoacetate is carried out in a continuous manner without a solvent, and methyl aminocaproate is heated while removing methanol. This is a flow sheet shown as an example of a method for producing caprolactam from adipic acid and adiponitrile in the case of converting it into caprolactam.

In the first step of producing methyl cyanovalerate, 1
is an exchange reactor, in which adipic acid and adiponitrile are each sent to exchange reactor 1 via conduits 10 and 11, and dimethyl adipate and adiponitrile extracted from distillation columns 5 and 6 are circulated. .

The exchange reaction between adipic acid and adiponitrile is carried out in the exchange reactor 1, and no separation or other operations are performed, and the mixture is directly sent to the esterification reactor 2, where it is passed through the distillation column 3 and the moat reactor 8.
methanol is circulated from Pressurized esterification reactor 2
The reaction solution containing cyanoacetate produced in step 3 is sent to a distillation column 6 after removing methanol, water, and dimethyl adipate in a demethanol tower 3, a dehydration tower 4, and a dimethyl adipate tower 5, respectively. The methanol removed is circulated to the esterification reactor through conduit 13, water is extracted from the system through conduit 14, and dimethyl adipate is circulated through conduit 1.
5 to the exchange reactor 1. In the distillation column 6, cyanocyanate is distilled, and the distilled cyano/cyanochloride is sent to the water addition reactor 7, and the distilled clear liquid containing adiponitrile as a main component is extracted from the lower part of the distillation column 6. It is discharged and recycled via conduit 20 to exchange reactor 1. Next, in the second step of producing methyl aminocaproate, the distillation column 6
The cyanocyanate chloride sent through conduit 16 from Raney cobalt supplied through conduit 17 and conduit 2
By contacting the hydrogen supplied from 1 in the hydrogenation reactor 7, it is reduced to methyl aminocaproate and guided to the cyclization reactor 8.

In the third step of producing caprolactam, methyl aminocaproate sent from the hydrogenation reactor 7 is heated in the cyclization reactor 8 together with a polyhydric alcohol with a higher boiling point than caprolactam led from the distillation column 9 to produce caprolactam. Manufactured.

The polyhydric alcohol containing caprolactam and having a boiling point higher than caprolactam is sent to the distillation column 9, where caprolactam is extracted from the upper part. It is then recycled to the cyclization reactor 8, where it is heated together with newly supplied methyl aminocaproate and converted into caprolactam.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 First, the following liquids A and B were prepared as raw material liquids.

A liquid containing 43.8 moles of adivic acid (0.300 moles), 52.2 moles of dimethyl adipate (0.300 moles), and 324.0 moles of adiponitrile (3.000 moles) was placed in a stainless steel autoclave with a content of 1. , 2 at 230℃ after nitrogen substitution
．． Immediate lighting was performed (high performance liquid chromatography analysis confirmed the production of 58.6 cyanovaleric acid).

) After cooling, 160.0 methanol (5.000 moles) was added, and the mixture was dried at 200 mm for 2 hours. After the esterification reaction was completed, the production of 76.1 units (0.540 mol) of dimethyl cyanoacetate and 51.8 units (0.298 mol) of dimethyl adipate was confirmed by gas chromatography. Methanol, water, dimethyl adipate, and shea/tertyl cyanate were removed from the reaction solution by a conventional method to obtain a distillation residue of 301.2 mm. (This distilled liquid is referred to as Liquid A.) Liquid B: Methyl aminocaproate 82.42 (0.5 mole) and tetraethylene glycol 741.6 mm were placed in a stainless steel autoclave with an internal volume of 2, and the mixture was directly exchanged with nitrogen. After, 23
The lights were on for one hour at 0:00.

After the reaction was completed, methanol and 565 moles (0.500 mol) of cabrolactam were removed from the reaction solution by distillation under reduced pressure to obtain a distillation residue of 749.3 moles. (This distillation residual liquid is referred to as liquid B.) A liquid: 301.2 hours, adipic acid: 39.4 hours (0.2 hours)
70 moles), 51.8 moles of dimethyl adipate (0.2 pseudomoles) and 29.2 moles of adiponitrile (0.270 moles) were placed in a stainless steel autoclave with a content of 1.
I prayed for 2.5 hours at 3000. After cooling, methanol 1
Adding 60.0 evening, Toazusa was performed for 2 hours at 20 and 0.
By distilling the reaction solution under reduced pressure, cyanocyanoacetate 7
7.5 moles (0.550 mol) were obtained. (This corresponds to a yield of 203.7% based on the charged adipic acid.) Next, in a stainless steel autoclave with an internal capacity of 300 ml, 70.5 mol of cyanovalerate (0.500 mol) and Raney cobalt ( OF, a trade name manufactured by JIIken Fine Chemical Co., Ltd., was developed by a conventional method.

) methanol slurry (Raney Cobalt 20.02,
Add methanol (20.0 methanol), and after nitrogen exchange, hydrogen pressure was reduced to 3.
The reaction was carried out at 0 K9', at a reaction temperature of 60 DEG C., and while supplying hydrogen to maintain a hydrogen pressure of 30 kg/min, the reaction was carried out until hydrogen absorption stopped. After the reaction was completed, the reaction solution was analyzed by gas chromatography, and the results showed that methyl aminocaproate was 69.6 moles (0.480 mol) and cabrolactam was 1.9 moles (0.0 mole).
The production of 17 mol) was confirmed. (Total yield of methyl aminocaproate and caprolactam 99.4%). While washing the catalyst with methanol, this reaction solution was poured into a stainless steel autoclave with a content of 2, and then B solution was added to a 749.3
The methanol was distilled off at room temperature under reduced pressure. After replacing the tube with nitrogen, the tube was heated at 230℃ for 1 hour. As a result of analyzing the reaction solution by gas chromatography, it was confirmed that 56.4 moles (0.499 mol) of caprolactam were produced. (Yield 99.8 based on cyanocyanate methyl used for ring reaction)
%, indicating that substances that were not recognized as reduction products can also be converted to caprolactam. ) Comparative Example 1 In the same manner as in Example 1, 70.5 ml of cyanocyanic acid (0.5
A reaction solution (containing 69.8 moles of methyl aminocaproate and 1.9 moles of caprolactam) and 652.5 moles of ethylene glycol were placed in a stainless steel autoclave and mixed with methanol at room temperature under reduced pressure. After removing the crabs, the pressure was brought to normal with nitrogen, and the temperature was kept at 230 oo for 1 hour.

As a result of analyzing the reaction solution, cabrolactam was 49.1 hours (0
．． The production of 435 mol) was confirmed. The reaction solution was then distilled to remove 48.2 moles (0.427 mol) of methanol, ethylene glycol, and caprolactam.

The presence of caprolactam was not observed in the distillation residue. This distiller and cyanoacetic acid teril 60.2 hours (0.
A reaction solution obtained by reducing 427 mol) of ethylene glycol and 652.5 mol of ethylene glycol were placed in a stainless steel autoclave having an internal capacity of 22 mol, and the same operation as above was carried out. Analysis of the reaction solution confirmed the production of 42.5 moles (0.376 mol) of caprolactam. (This corresponds to a caprolactam yield of 88.1% based on the newly added cyanovalerate.) Example 2 Tetraethylene containing caprolactam obtained in Example 1 instead of Solution B used in Example 1 methanol and caprolactam from glycol solution 56.1 m (0.49
Gas chromatography analysis revealed no presence of caprolactam.

) was used, and 69.9 hours (0.4
96 mol) was placed in a stainless steel autoclave having an internal capacity of 2 with a reaction solution reduced in the same manner as in Example 1, and the reaction was carried out in the same manner as in Example 1. As a result of analysis of the reaction solution, 56.3 mol (0.4 mol) of caprolactam was found. This corresponds to a caprolactam yield of 100.4% based on the tertylated cyanovalerate freshly subjected to the reaction.
(Repeat experiment 1) In the same manner, the reaction solution obtained by reducing the same mole of cya/silyl cyanide as the caprolactam that had been distilled off was sequentially added to the residue from the previous distillation, and the reaction and distillation were repeated.

(Repeated Experiments 2 to 6) The results are shown in Table 1. No.
Table 1 Example 3 29.2 mm (0.200 mol) of adipic acid and 324.0 mol (3000 mol) of adiponitrile were placed in a stainless steel autoclave with a content of 1, and after exchange with nitrogen, the mixture was heated to 24 and 0.
I did the time rope azusa.

(As a result of analysis by high performance liquid chromatography, it was confirmed that 11.5 mol of cyanocyanic acid was produced.) After cooling, 138.0 mol of ethanol (3.000 mol) was added.
In the afternoon, we performed lantern worship for three hours. After the esterification reaction is completed,
Ethyl cyanoacetate 60% by gas chromatography
．． The production of 1.0 mole (0.005 mole) of diethyl adipate was confirmed. From the reaction solution, ethanol, water, jetyl adipate and shea/
Ethyl valerate was removed. Next, 29.1 mols (0.199 mol) of adipic acid and 2 mols adiponitrile were added to the distillation residue.
1.0 mol (0.194 mol) was added thereto, and the mixture was placed in a stainless steel autoclave with a content of 1, and after nitrogen conversion, it was heated at 24,000 ℃ for 3 hours.

After cooling, 138.0 ml (3.000 mol) of ethanol was added, and the mixture was incubated at 190 qo for 3 hours. As a result of analysis, 60.3 mols (0.389 mol) of ethyl cyanoacetate,
The production of 1.2 moles (0.006 mol) of diethyl adipate was confirmed. One female of the shea/ethyl cyanate obtained in the above two reactions. (0.700 mol) and an ethanol slurry of Raney cobalt (Raney cobalt 21.
7 evenings, ethanol 60.6 evenings) and ethanol 374.
Put 0 ml into an autoclave with a content of 1, and after purging with nitrogen, the hydrogen pressure was 60 k9 at a reaction temperature of 45°C.
While replenishing hydrogen to maintain the temperature, the reaction was carried out until hydrogen absorption stopped.

After the reaction was completed, gas chromatography analysis of the reaction solution revealed that ethyl aminocaproate was 109.42 (0.688
The production of 1.1 moles (0.010 moles) of caprolactam was confirmed. (Total yield of ami/ethyl caproate and caprolactam: 997%).The catalyst was separated from this reaction solution, washed with ethanol, and added to the reaction solution for 700 mL.
．． It was made into an ethanol solution. This ethanol solution 1
00.0 yen (0 as ethyl cyanocyanoacetate subjected to reduction)
．． 100 mol) and diglycerin 90.0 mol in content 3
The mixture was placed in a three-necked flask on top of a 3-necked flask, and the internal temperature was brought to 800 ml to remove the ethanol, and then the mixture was heated at 200 qo for 4 hours while removing the distilled ethanol. After the reaction was completed, the reaction solution was distilled under reduced pressure, and caprolactam was added at 9.3 hours (0.
．． 082 mol) was obtained. (The yield was 82.0% based on the cyanoethyl cyanoacetate standard used in the reduction. Hereinafter, in this example, the caprolactam yield is shown based on the cyano/ethyl cyanoacetate standard.) Furthermore, the above-mentioned aminocaprone was added to the distillation residue. An ethanol solution of ethyl chloride (82.0 mol) (0.082 mol as ethyl cyanoacetate subjected to reduction) was added, and reaction and distillation were carried out under the same conditions to yield 9.2 mol (0.0 mol) of caprolactam.
．． 081 mol) was obtained.

This is a yield variation that traces back to the newly added ethyl aminocaproate and ethyl cyanocephalate. It is 8%. (Repeat experiment 1) In the same manner, the above ethanol solution in which the distilled caprolactam was reduced with equimolar ethyl cyanovalerate was sequentially added to the previous distillation residue, and the reactive distillation was repeated. (Repeated Experiments 2 to 5) The results are shown in Table 2. Examples 4 to 6 The solvent in Example 3 was changed from diglycerin to tetraethylene glycol (Example 4) and bentaerythritol (Example 5).
), 1,2,3-butanetriol (Example 6), but otherwise the reaction was carried out in the same manner as in Example 3.

The results are shown in Table 2. (The yield is the caprolactam yield based on the sia/ethyl cyanate as in Example 3.) Table 2 Example 7 Adipic acid 730 moles (blood.500 moles) and adiponitrile 432.0 moles (4 moles) .000 mol) and dimethyl adipate (0.150 mol) were placed in a stainless steel autoclave with a content of 2, and after purging with nitrogen, the mixture was heated at 220°C for 5 mol.
Koji Azusa was carried out for an hour, and after cooling, methanol 320.0 t (1
0.000 mol) was added thereto, and lanternization was performed at 220°C for 1 hour.

By distilling this reaction solution, 114.2 units (0.810 mol) of dimethyl cyanocephalic acid and 26.8 units (0.154 mol) of dimethyl adipate were obtained. Next, 59.1 moles (0.405 moles) of adipic acid, 43.7 moles (0.405 moles) of adiponitrile, and 26.8 moles (0.1 moles) of dimethyl adipate were added to the distillation residue. The mixture was placed in the above autoclave, and the reaction was carried out in the same manner. As a result of distillation, 120.0 ml of cyanocyanate (0.
851 mol), dimethyl adipate 256 mol (0.41
7 mol) was obtained. (Repeated experiment - ■) Hereinafter, by operating the same machine, the same amount of adipic acid as in the repeated experiment ■ and the grass adiponitrile shown in Table 3 were added to the distilled liquid from which cyanoacetic acid and dimethyl adipate had been distilled off. was added, and the reaction and distillation were repeated. (Repeated experiments ① to ②) The results are shown in Table 3. Third, 141.0 units of the obtained methyl cyanoacetate (1.
000 mol) and Rane' cobalt methanol slurry
(Raney cobalt 14.1 evening, meta/r 40.0 evening)
was placed in a stainless steel autoclave with an internal capacity of 500 ml, methanol was completely distilled off at room temperature under reduced pressure, the pressure was brought to normal pressure with nitrogen, and nitrogen exchanged twice to reduce the hydrogen pressure to 20 k.
The reaction was carried out at a reaction temperature of 80° C. and hydrogen was replenished to maintain a hydrogen pressure of 20 k9/mm until hydrogen absorption stopped.

The catalyst was filtered from the reaction solution, washed with methanol, added to the reaction solution, and 200.0% of the mixed solution was analyzed by gas chromatography. As a result, methyl aminocaproate was 125%.
0 mole (0.862 mol), caprolactam 15.3 mole (
The production of 0.135 mol) was confirmed. Reduction reaction solution 100
．． Pour the contents into a three-necked flask with 480.0 methanol and triethylene glycol, raise the internal temperature to 70 oz to remove methanol, and then boil for 1 hour at 250 qo while removing the distilled methanol. did.

After completion of the reaction, the reaction solution was distilled under reduced pressure, and 50% caprolactam was added.
9 (0.450 mol) was obtained. This is a yield of 90.0%, which is based on cyanovalerate. Next, 90.0 ml of the reduction reaction solution was added to the distillation residual solution, and the reaction was carried out in the same manner. As a result of vacuum distillation, 50.9 ml (0.450 mol) of caprolactam was obtained. This is a yield of 100.0 based on the newly added reduction reaction solution.
Corresponds to %. Example 8 In the same manner as in Example 7, 141.0 g of shea/green grass acid was obtained.

Next, this tertylated cyanocyanate was reduced under the conditions shown in Table 4. (Experiment Nos. 1 to 5) The results are shown in Table 4. Table 4 Hydrogen Shoichi 3 0kg/reaction whiteness 40°C Next, Experiment No. The reaction solution obtained in step 1 and 500.0 g of tetraethylene glycol were placed in a stainless steel autoclave with a content of 1, and the solvent was completely removed at room temperature under reduced pressure. After purging with nitrogen, the mixture was heated at 210°C for 5 hours. did.

After completion of the reaction, caprolactam (181%) was distilled under reduced pressure.
0.160 mol) was obtained. Thereafter, a hydrogenation solution (mixed hydrogenation experiment Nos. 2 to 5 and divided into 5 equal parts) was added to the nuclear distillation residual liquid, the solvent was similarly distilled off, and then the reaction and distillation were repeated.

As a result, 99.6%, 101.4%, and 97.2% were unemployed. Caprolactam was obtained with a yield of 1% and 100.8%.

[Brief explanation of drawings]

FIG. 1 is a graph showing changes over time in the yield of cya/cyanocyanic acid and the yield of cyanocyanic acid in the exchange reaction of adipic acid with adiponitrile. FIG. 2 is a flow sheet showing an example of a method for producing caprolactam from adipic acid and adiponanitrile. Figure 2

Claims (1)

[Claims] 1. Adipic acid and adiponitrile are heated to perform an exchange reaction, and alcohol is added to the exchange reaction solution to produce an ester without isolating the product cyanovaleric acid from the exchange reaction solution. to produce a cyanovalerate ester, reduce the cyanovalerate to an aminocaproate ester using a catalyst, and heat the aminocaproate ester in a polyhydric alcohol having a higher boiling point than caprolactam to produce caprolactam; A method for producing caprolactam from adipic acid and adiponitrile, which comprises distilling off the caprolactam produced and circulating the distillation residue liquid to a system that heats a polyhydric alcohol with a higher boiling point than caprolactam and an aminocaproic acid ester. 2. The method according to claim 1, wherein the exchange reaction is carried out with 1 to 70 mol of adiponitrile per 1 mol of adipic acid. 3. The method according to claim 2, wherein the exchange reaction is carried out with 1 to 50 mol of adiponitrile per 1 mol of adipic acid. 4. The method according to claim 1, wherein the exchange reaction is carried out at 150-270°C. 5. The method according to claim 4, wherein the exchange reaction is carried out at 200 to 250°C. 6. The method according to claim 1, wherein the reaction time of the exchange reaction is 1 to 5 hours. 7. The method according to claim 1, wherein the exchange reaction is carried out using 1 to 70 mol of adiponitrile per 1 mol of adipic acid, at a temperature of 150 to 270°C, and for a reaction time of 1 to 5 hours. 8. The method according to claim 7, wherein the exchange reaction is carried out using 1 to 50 mol of adiponitrile per 1 mol of adipic acid, at a temperature of 200 to 250°C, and for a reaction time of 1 to 5 hours. 9. The method according to claim 1, wherein the alcohol for esterifying the exchange reaction solution is methanol or ethanol. 10. The method according to claim 1, wherein the alcohol for esterifying the exchange reaction solution is methanol. 11. The method according to claim 1, wherein the amount of alcohol used to esterify the exchange reaction solution is 2 to 200 moles per mole of adipic acid used in the exchange reaction. 12. The method according to claim 11, wherein the amount of alcohol used to esterify the exchange reaction solution is 2 to 100 moles per mole of adipic acid used in the exchange reaction. 13. The method according to claim 1, wherein the esterification of the exchange reaction solution is carried out at 150 to 230°C. 14. Claim 1, wherein the alcohol used to esterify the exchange reaction solution is 2 to 100 moles per mole of adipic acid subjected to the exchange reaction, and the reaction temperature is 150 to 230°C. the method of. 15. The method according to claim 1, wherein the distillation residue after distilling off the cyanovaleric acid ester obtained by esterifying the exchange reaction solution under reduced pressure is recycled to the exchange reaction system. 16. The method according to claim 1, wherein the exchange reaction solution is esterified, the adipic acid diester produced as a by-product is isolated by distillation, and the adipic acid diester is recycled to the exchange reaction system. 17 Claim 1 in which the catalyst is Raney cobalt
The method described in section. 18 Reaction temperature 40-80 using Raney cobalt as a catalyst
18. The method according to claim 17, wherein cyanovalerate is reduced to aminocaproate at a hydrogen pressure of 10 to 50 kg/cm^2. 19. The method according to claim 1, wherein the aminocaproic acid ester is heated in a polyhydric alcohol having a higher boiling point than caprolactam at a concentration of 3 to 20 wt%. 20. The method of claim 19, wherein the aminocaproic acid ester is heated in a polyhydric alcohol having a higher boiling point than caprolactam at a concentration of 5 to 15 wt%. 21 Aminocaproic acid ester in a polyhydric alcohol with a higher boiling point than caprolactam at 180-250°C, 3-2
20. The method of claim 19, wherein the method is heated to a concentration of 0 wt%. 22 Aminocaproic acid ester in a polyhydric alcohol with a higher boiling point than caprolactam at 180-250°C, 5-1
21. The method of claim 20, wherein the method is heated to a concentration of 5 wt%. 23. The method according to claim 1, wherein the polyhydric alcohol having a higher boiling point than caprolactam is tetraethylene glycol. 24 A patent claim in which alcohol produced along with caprolactam produced by heating aminocaproic acid ester in a polyhydric alcohol with a boiling point higher than that of caprolactam is recycled to a system for esterifying an exchange reaction solution of adipic acid and adiponitrile with alcohol. The method described in item 1.