JPS6020375B2 - Lactam manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing lactams by Beckmann rearrangement of cycloalkanone oximes.

As a method for producing a lactam by subjecting a cycloalkanone oxime to Beckmann rearrangement, a method of heating a cycloalkanone oxime with a mineral acid such as concentrated sulfuric acid, oleum, or polyphosphoric acid has been conventionally known.

However, when such mineral acids are used, it is necessary to neutralize them with an alkali when recovering the lactam from the Beckmann rearrangement reaction product, and a large amount of by-product salts are generated. There is a method of sufficiently diluting the Beckmann rearrangement reaction product with water, extracting and separating the lactam contained therein, and then dehydrating and concentrating the citrus residue, but this method does not yield a sufficient lactam recovery rate. However, there are drawbacks such as the fact that it requires a large amount of thermal energy. Therefore, without producing such a creation salt, the inventors
Moreover, as a result of intensive research into a method for recovering the rearrangement agent through simple operations and recycling it for use in the rearrangement reaction, the present invention was achieved.

That is, the present invention relates to a method for producing a lactam, which is characterized by subjecting a cycloalkanone oxime to Beckman rearrangement using barium ditetrafluoroborate or tincture ditetrafluoroborate in an acetone-acetic acid mixed solvent. The reaction of this invention proceeds as shown in the following reaction formula.

(However, M in the formula represents the gunwale or Zn, and n is 3 to
(representing an integer of 11) That is, once a cycloalkanone oxime and barium ditetrafluoroborate or tincture ditetrafluoroporate are reacted, the cycloalkanone oxime: boron fluoride key body and barium monofluoroborate or The cycloalkanone oxime/boron difluoride is converted into a lactam/boron difluoride key by Betzkmann rearrangement, and the lactam/boron difluoride and barium monofluoroborate or tinc monofluoride are formed. The lactam reacts with the fluoroporate to produce barium ditetrafluoroborate or tincture ditetrafluoroborate.

Thus, the lactam is liberated and the barium ditetrafluoroborate or tincture ditetrafluoroborate is recovered and recycled to the Beckmann rearrangement reaction. Siku used in the method of this invention.

The alkanone oxime has the following general formula, (where n in the formula
is the same as above) and is expressed as "For example, cyclobutanone oxime,
Cyclobentanone oxime, cyclohexanone oxime, cyclohef.

Examples include tanone oxime, cyclooctanone oxime, cyclononanone oxime, cyclodecanone oxime, cycloundecanone oxime, and cyclododecanone oxime. Further, the rearrangement agent used in the method of the present invention is barium ditetrafluoroborate or tinku ditetrafluoroborate represented by the following general formula.

M(BF4)2 (However, M in the formula is the same as above) These rearrangement agents are required to have high purity, so for example, as a method for preparing barium ditetrafluoroborate, anhydrous barium fluoride is added in excess. It is appropriate to react with an ether of boron fluoride or acetic acid and boron trifluoride, and a method for preparing tintetrafluoroporate is to react anhydrous zinc fluoride with an excess of lactam or boron trifluoride. It is appropriate to make the key body react.

As for the ratio of the rearrangement agent to the cycloalkanone oxime, it is appropriate to use an excess amount of 2 to 10 moles, particularly 3 to 10 moles, of the rearrangement agent to 1 mole of the cycloalkanone oxime.
5 mol is preferred.

Below this range, the lactam selectivity decreases, and above this range, a large amount of mixed solvent is required to dissolve the rearrangement agent, which is not preferable. This reaction is carried out in an acetone-acetic acid mixed solvent, and the preferred mixing ratio of acetone and acetic acid is 40-60 mol% acetone and 40-60 mol% acetic acid.
It is in the range of 90 mol%.

The reaction temperature is suitably 120 to 160 oo, especially 13
0 to 150 qo is preferable. If the reaction temperature is lower than this range, the lactam selectivity will decrease, and if it is higher than this range, the mixed solvent will decompose, which is not preferable. Further, the pressure generated when heating the mixed solvent is sufficient as the reaction pressure, but further pressure may be applied. By carrying out the method of this invention, almost all of the cycloalkanone oxime is reacted, so lactam can be produced in high yield, but a small amount of cycloalkanone is created.

Therefore, the reaction product liquid contains lactam, cycloalkanone, mixed solvent, and rearrangement agent, and in order to obtain the lactam from such reaction product and recover the rearrangement agent, direct distillation is required by normal operations. However, it is more advantageous to carry out the following operation.

That is, the reaction product liquid is distilled at normal pressure to first remove only acetone or a portion of acetone and acetic acid, and then the liquid is poured into the solution.

By adding chlorinated hydrocarbons such as roform and carbon tetrachloride, or aromatic hydrocarbons such as benzene, toluene, and xylene, the solubility of the rearrangement agent contained in the reaction product liquid is reduced and the rearrangement agent is precipitated. This is passed through a vacuum furnace to almost quantitatively recover the rearrangement agent as crystals, and one of the furnace liquids is distilled under reduced pressure to remove the previously added chlorinated hydrocarbons or aromatic hydrocarbons, acetic acid, and cyclohydrocarbons. This is an operation in which the lactam is obtained as a residue after distilling off the alkanone. The lactam obtained by the method of this invention has the following general formula: (
However, n in the formula is the same as above) It is a lactam corresponding to the raw material cycloalkanone oxime.

By carrying out the method of this invention, it is possible to produce lactams from cycloalkanone oximes without generating salts, and at the same time, the rearrangement agent used in the process can be recovered almost quantitatively in its original form. and can be recycled for Beckmann rearrangement reaction.

Note that acetone and acetic acid recovered by distillation can also be recycled and used as a mixed solvent. Next, examples and comparative examples of the present invention will be shown.

Example 1 Barium ditetrafluoroborate 50% acetone-acetic acid mixed solvent (acetone mole fraction 40%) 1
50' was heated to 13,000 ℃ in an autoclave, and 50 ml of acetone-acetic acid mixed solvent (acetone molar fraction 40%) of 4.0 cyclohexanone oxime was press-fitted therein at 135 to 14 mm over 7 minutes.

After the reaction was completed, mainly acetone was distilled off from the reaction product liquid, and then 300 g of chloroform was added to precipitate barium ditetrafluoroborate, which was then separated by furnace. This crystal was 49 days old, and the recovery rate was 98%. One of the furnace liquids was distilled to remove chloroform and acetic acid, and 0.3 liters of cyclohexanone was distilled out, yielding 3.60 liters of caprolactam as a residue. The yield was 90%. Example 2 Barium ditetrafluoroborate 50 ml of acetone-acetic acid mixed solvent (acetone molar fraction 28%) 150 ml was heated to 130 ml in an autoclave, and cyclohexanone oxime 4.0 ml of acetone-acetic acid mixture was heated to 130 ml in an autoclave. Solvent (acetone mole fraction 28%) 50 I to 136 to 1
It was press-fitted at 45°C for 7 minutes.

After completion of the reaction, mainly acetone was distilled off from the reaction product liquid, and then 300 m' of carbon tetrachloride was added to precipitate barium ditetrafluoroborate, which was then separated in a furnace. This crystal was 49.5 days old, and the recovery rate was 99%. One of the furnace liquids was distilled to remove carbon tetrachloride and acetic acid, yielding 3.5 g of caprolactam as a residue. The yield was 87.5%. Example 3 Barium ditetrafluoroborate recovered in Example 2 was heated to 130°C in an autoclave, and cyclohexanone was added to it. oxime 4.0
Acetone-acetic acid mixed solvent (acetone molar fraction 30%)
) 50' was press-fitted in 7 minutes at 130 to 150 qo.

After the reaction was completed, acetone was distilled off from the reaction product solution, and 300% of xylene was added to precipitate barium ditetrafluoroborate, which was then separated by furnace. This crystal had an age of 49.0 mm and a recovery rate of 99%. One of the furnace liquids was distilled under reduced pressure to obtain 3.4 hours of caprolactam.
The yield was 85%. Example 4 Barium ditetrafluoroborate 4.0 ml of acetone-acetic acid mixed solvent 150 ml was heated in an autoclave at 130°C.
Heated to
．． 0 qo and barium ditetrafluoroborate 10 qo acetone-acetic acid mixed solvent 50 qo at 13 o ~ 150 qo 7
It was press-fitted in minutes.

The acetone molar fraction of the reaction solution at this time was 26%. After the reaction was completed, post-treatment was carried out in the same manner as in Example 1 to obtain barium ditetrafluoroporate of 13.8 kg (recovery rate of 98.5
%) and z-caprolactam 0.85% (yield 85%)
) was obtained. Example 5 Example 1 Acetone-acetic acid mixed solvent (acetone mole fraction 30%) containing 39% of tincture ditetrafluoroborate and 150% of cyclohexanone oxime and 4.0% of cyclohexanone oxime were mixed in an acetone-acetic acid mixed solvent (acetone mole fraction 30%). reacted in the same way.

After the reaction was completed, the product was post-treated in the same manner as in Example 1 to obtain 38.6 units of tincture ditetrafluoroporate (99% recovery rate) and 3.5 units of caprolactam (yield 87.5%). Comparative Example 1 Barium ditetrafluoroborate 25
Evening acetic acid solvent 100 Z and cyclohexanone oxime 3
．． The reaction was carried out in the same manner as in Example 1 with 50% of acetic acid solvent.

After the reaction was completed, the reaction product liquid was distilled to obtain 1.8 g of caprolactam (yield: 60%). Comparative Example 2 50 parts of barium ditetrafluoroporate and 150 parts of acetone solvent were reacted in the same manner as in Example 1 with 4.0 parts of cyclohexanone oxime and 50 parts of acetone solvent.

Claims (1)

[Claims] 1. A method for producing a lactam, which comprises subjecting a cycloalkanone oxime to Beckman rearrangement using barium ditetrafluoroborate or tincture ditetrafluoroborate in an acetone-acetic acid mixed solvent.