KR790001022B1 - Process for the recovery of -caprolactom from reaction mixture of -caprolactam and sulphuric acid - Google Patents

Abstract

ε-Caprolactam and solid (NH4)2SO4 were recovered from lactam - H2SO4 reaction mixts. by neutralizing the H2SO4 at higher atm. pressure with NH3 in a circulating vol. of (NH4)2SO4 soln.. The neutralized mixt. was separated to lactam and (NH4)2SO4 phases by using the heat absorbed by the water during the neutralization process.

Description

How to Recover Caprolactam

Figure 1: A diagram illustrating an embodiment of adding the resulting ammonium sulfate layer to a reaction mixture of lactam and sulfuric acid in the next batch and recovering the lactam and ammonium sulfate from the reaction mixture at low pressure.

Figure 2: A diagram illustrating an embodiment in which an ammonium sulfate layer is used to lower the acidity of dislocation mixtures in different batches.

-카프로락탐과 황산의 반응혼합물로부터

-카프로락탐을 회수하는 공정과 이때 생성된 황산 암모늄에 관한 것이다.

-카프로락탐은 나이론-6제조의 출발물질로 사용된다.The present invention neutralizes sulfuric acid in the presence of water,

From the reaction mixture of caprolactam and sulfuric acid

-A process for recovering caprolactam and an ammonium sulfate produced at this time.

Caprolactam is used as a starting material for the production of nylon-6.

-카프로락탐과 황산의 반응혼합물은 시클로헥사논 옥심을 황산, 올레움 혹은 삼산화황에 의해

-카프로락탐으로 Beckmann전위시키는 공정에서, 또한 시클로헥산 카복실산 또는 이들의 유도체를 황산 존재하에서 nitrosating 제(劑)와 반응시킴으로서

-카프로락탐을 제조하는 공정에서 얻어진다.

The reaction mixture of caprolactam and sulfuric acid is converted to cyclohexanone oxime by sulfuric acid, oleum or sulfur trioxide.

In the Beckmann dislocation with caprolactam, and also by reacting cyclohexane carboxylic acids or derivatives thereof with nitrosating agents in the presence of sulfuric acid.

It is obtained in the process of manufacturing a caprolactam.

-카프로락탐을 회수하기 위하여 혼합물을 중화제 존재하에 암모니아수로 처리하면 상부의 락탐층과 하부의 농황산암모늄 용액이 형성되며 이 두 층을 분리한다. 또한 중화는 황산암모늄 결정존재하에 가압조건하에서 진행시킬수도 있고 하층으로부터 고체황산암모늄을 제거한 후 얻어지는 황산 암모늄을 포함하는 모액을 재순환시킬수도 있다. 방출되는 중화열은 물을 증기로 전환시키기 위해 사용될 수도 있다. 이러한 전환은 1~2 기압하에서 효과적이다. 왜냐하면 그 이상의 고압은 보다 높은 온도를 필요로 하며 가수분해로 인한 락탐의 손실을 증가시킨다.From this reaction mixture

Treatment of the mixture with ammonia water in the presence of a neutralizing agent to recover caprolactam forms the upper lactam layer and the lower ammonium sulfate solution, separating the two layers. Neutralization may also be carried out under pressurized conditions in the presence of ammonium sulfate crystals, or the mother liquor containing ammonium sulfate obtained after removing solid ammonium sulfate from the lower layer may be recycled. The heat of neutralization released may be used to convert water into steam. This conversion is effective at 1-2 atm. Because higher pressures require higher temperatures and increase the loss of lactam due to hydrolysis.

Neutralization under pressurized conditions in the absence of recirculated ammonium sulfate mother liquor and / or ammonium sulfate crystals can shorten the residence time of the lactam in the neutralization zone, thus increasing the atmospheric pressure above (2-5) to generate steam. Even at high temperatures suitable for working pressure, losses due to hydrolysis of lactams can be slight.

-카프로락탐과 황산의 반응 혼합물로부터

-카프로락탐을 회수하는 공정에 관한 것이다. 본 발명에 의한 공정을 대기압하에서 진행되는 종래의 중화기술에 비해 다음과 같은 잇점이 있다.The present invention is a process for neutralizing sulfuric acid with ammonia under atmospheric pressure above atmospheric pressure in the presence of water in the absence of a mother liquor containing ammonium sulfate crystals and / or ammonium sulfate, and neutralizing the mixture by removing heat of neutralization by evaporating water to produce steam. To a lactam layer and a water-soluble ammonium sulfate layer

From the reaction mixture of caprolactam and sulfuric acid

It relates to a process for recovering caprolactam. The process according to the present invention has the following advantages over the conventional neutralization technology that proceeds under atmospheric pressure.

a. The heat of neutralization is removed even without a heat exchanger.

b. The heat of neutralization is used to produce steam.

c. Mixing becomes good by boiling in the reaction mixture.

d. The removal of the heat of neutralization takes place at a substantially constant temperature and is therefore very rapid compared to the removal of heat using a cooling water and heat exchanger capable of depositing crystals.

The process of the present invention can be run under a variety of pressures (pressures higher than atmospheric pressure). The higher the pressure, the higher the pressure vapor is obtained, but the higher the rate of lactam loss due to increased hydrolysis. Pressures of up to about 10 atmospheres are acceptable. In practice, 2-5 atmospheres are particularly suitable. Usually the neutralized reaction mixture contains 1.3-1.7 moles of sulfuric acid per mole of caprolactam. More preferably, ammonia is added to the gas phase.

If water-soluble ammonia is added, 20-25% by weight is possible but not suitable. The water-soluble ammonium sulfate layer and lactam layer obtained according to the process of the present invention are treated by a known method.

In an embodiment of the invention, the aqueous ammonium sulfate layer is treated in a special manner. That is, the aqueous layer, if necessary, is heat-exchanged with water for steam production, and then added to the next batch of reaction mixtures of lactam and sulfuric acid and neutralized in the presence of recycled ammonium sulfate solution to neutralize the original amount of the reaction mixture of lactam and sulfuric acid. By neutralizing sulfuric acid under a pressure lower than that which can be achieved, preferably at atmospheric pressure, ammonium sulfate crystals are continuously formed, recovering lactam and ammonium sulfate from the reaction mixture and removing the heat of neutralization by evaporation of the door from the solution.

If the aqueous ammonium sulfate layer obtained in the neutralization of the original amount of the reaction mixture (lactam and sulfuric acid) is treated as described above, no fractionation crystallizer is necessary.

According to another embodiment of the present invention, an aqueous ammonium sulfate layer is added to a reaction mixture of lactam and sulfuric acid in the following batch, and the reaction mixture is extracted with an extractant such as chloroform to form an aqueous layer and a lactam solution in the extract, Lactam can be recovered from this solution. This process has the advantage that ammonium sulfate formed in the initial neutralization of the reaction mixture of lactam and sulfuric acid can recover the lactam from the reaction mixture of the next batch and form an aqueous solution containing ammonium hydrogen sulfate. Thus, there is no need to prepare ammonium sulfate with lactam. Firing the final solution containing ammonium hydrogensulfate yields sulfur dioxide.

In this embodiment, the lactam layer obtained from the initial amount of the reaction mixture of lactam and sulfuric acid may be added to the mixture to be extracted, if necessary.

The present invention can be best described as a bucheon drawing when describing two embodiments of the present invention.

-카프로락탐과 황산의 반응혼합물을, 도관 4를 통해 암모니아를 공급한다. 락탐과 황산 암모늄용액의 혼합물은 도관 6을 통해 반응기로부터 분리기 B로 이동된다.In Figure 1, the first neutralization reactor A contains neutralizer 1 and wash zone 2. The head of the secondary neutralization reactor C is connected to the spherical boiling vessel D through a side tube, in which the side tube extends vertically. The condenser E with the cooling jacket 20 fitted is fitted to the head of the boiling vessel E described above. Boiling vessel D is connected to sedimentation tank F at the bottom via a sedimentation tube. The settling tank is in turn connected to the bottom of the secondary neutralization reactor. When the unit is in operation, the neutralizer 1, which is operated under atmospheric pressure,

The reaction mixture of caprolactam and sulfuric acid is fed ammonia through conduit 4. The mixture of lactam and ammonium sulfate solution is transferred from reactor to separator B through conduit 6.

If necessary, induction cylinder 5 can be fixed in the neutralizer 1 and mixed in the reactor. An ammonium sulfate solution is obtained in the lower layer in separator B, which is transferred to a secondary neutralization reactor through conduit 12 with a diffusion valve 11 and recycled through conduit C.

The steam generated in the neutralizer by the heat of reaction taken out is recovered through conduit 10 with valve 9 installed via washing zone 2 with plate 7. Pour the water needed to clean the lactam and ammonia in the vapor through conduit 8 to the head of wash zone 2.

The neutralized mixture flows through conduit 6 to separator B, where it separates into the lower layer consisting of an upper layer of lactam and ammonium sulfate solution.

The lactam bed is discharged as product through conduit 14. Ammonium sulfate solution is fed to the secondary neutralization reactor C through conduit 12. The reactor is also fed a secondary batch of potential mixture via conduit 17. Ammonia is supplied through conduit 15 and, if necessary, via conduit 16. Secondary neutralization reactor C is operated at a lower pressure than reactor A, for example at atmospheric pressure.

The boiling mixture in which ammonium sulfate is suspended in a lactam solution saturated with ammonium sulfate is returned to the bottom of tube C through boiling vessel D and sedimentation tank F. The supplied strong acid is moderately diluted by this circulating fluid, thus eliminating the risk of hydrolysis of the lactam due to too high acid concentration.

The recirculation flow in the device shown is maintained by supplying nitrogen with ammonia gas through conduit 15 to ensure that the bubbles generated create a desirable circuit. In practice, the recycle flow may be maintained by a pump.

Water vapor generated in the boiling vessel D is discharged through conduit 21 to condenser E. Preferred cooling of the condenser E is by means of a cooler 20, where the coolant is supplied through conduit 18 and discharged through conduit 19. If necessary, water may be supplied to the system via conduit 21.

Plate 23, placed at the bottom of condenser E, washes out the lactam.

The settling tank F, the space between the wall and the outside of the submerged tube 22, is a separate storage of lactam oil, the upper layer of lactam oil being discharged through conduit 24.

The crystal suspension is discharged through conduit 25 to centrifuge G and the centrifuge is supplied with wash water through conduit 26. Mother liquor and wash water are recycled through conduit 27, and a portion of the recycle stream is periodically discharged through conduit 28. The washed ammonium sulfate crystals are discharged as product through conduit 29.

-카플로락탐과 황산의 혼합물 도관 2를 통해서는 암모니아가 공급된다. 도관 3을 통해 물을 공급하여 수증기에 섞여나오는 락탐과 암모니아를 세척한 후에, 생성된 증기를 도관 4를 통해 배출시킨다. 생성된 락탐은 도관 5를 통해 배출되며 황산 암모늄용액은 도관 6및 확산밸브 7을 통해 희석용기 B로 이동된다. 용기 B에는 도관 8을 통해 락탐과 황산의 혼합물의 새로운 뱃치가 공급되며 필요한 경우에는 도관 9를 통해 물을 공급한다.In Figure 2, A is a neutralizer operating under pressure above atmospheric pressure, B is a dilution vessel operating under atmospheric pressure, and C is an extractor. Neutralizer A, via conduit 1

Ammonia is supplied via conduit 2, a mixture of caprolactam and sulfuric acid. The water is fed through conduit 3 to wash the lactam and ammonia mixed with the water vapor, and then the resulting vapor is discharged through conduit 4. The resulting lactam is discharged through conduit 5 and the ammonium sulfate solution is transferred to dilution vessel B through conduit 6 and diffusion valve 7. Vessel B is supplied with a fresh batch of a mixture of lactam and sulfuric acid via conduit 8 and water if necessary via conduit 9.

The calorific value of the ammonium sulfate solution is for example supplied through conduit 3 and used to preheat the water. The temperature in the dilution vessel is maintained at about 30 ° C. The amount of the ammonium sulfate solution and the potential mixture of lactam and sulfuric acid supplied to the dilution vessel B is such that the molar ratio of ammonium sulfate in the final mixture is between 0.4: 1 and 0.6: 1 relative to the content of ammonium sulfate and sulfuric acid.

After dilution in dilution vessel B, the mixture is fed through conduit 10 to extractor C, which is supplied with lactam extractant such as chloroform via conduit 11. If necessary, the lactam released from the neutralizer A through conduit 5 may be supplied to the extraction unit C. The lactam solution in the organic solvent is released through conduit 12.

Lactam is recovered from this solution by a known method. Ammonium hydrogensulfate can be withdrawn from the system through conduit 13. This solution is treated by known methods such as the process of conversion to solid ammonium sulfate by neutralization and crystallization. The ammonium hydrogen sulphate in the solution may be pyrolyzed to recover with ammonia and sulfur trioxide or calcined to form a mixture of nitrogen, sulfur dioxide and water vapor. Sulfur trioxide and sulfur dioxide formed in this process can be made into sulfuric acid or oleum which can be used again in the manufacture of lactams. The following examples illustrate the invention.

Example 1

-카프로락탐 및 1.3kg/시간의 황산의 전위혼합물을 도관 3을 통해 150℃에서 3.4기압하에 동작하는 1차 중화반응장치에 공급하고, 도관 4를 통해서 0.45kg/시간의 암모니아를, 도관 8을 통해서는 2.51kg/시간의 물을 공급한다. 중화반응장치 A에서 락탐을 약 20분간 체류시킨다. 이 조건하에서는 0.5중량%미만의 락탐이 가수분해된다. 도관 10을 통해 3.4기압의 0.86kg/시간의 증기가 회수된다.1 kg / hour in the embodiment of the form shown in Figure 1

A potential mixture of caprolactam and sulfuric acid of 1.3 kg / hour is fed through conduit 3 to a primary neutralization unit operating at 3.4 ° C. at 150 ° C., and 0.45 kg / hour of ammonia through conduit 4, It supplies 2.51 kg / hour of water. The lactam is held in the neutralization reactor A for about 20 minutes. Under this condition, less than 0.5% by weight of lactam is hydrolyzed. Conduit 10 recovers 0.86 kg / hr of steam at 3.4 atmospheres.

Secondary neutralization reactor C, operating at atmospheric pressure at 180 ° C., was charged with 1.75 kg / h ammonium sulfate and 1.43 kg / h water through conduit 12, 0.93 kg / h lactam and 1.21 kg / h through conduit 17. Sulfuric acid is fed 0.42 kg / hour of ammonia through conduit 15. The amount of water supplied to the system through conduits 16 and 26 is 0.26 kg / hour. 1.33 kg / hr of water vapor is discharged through conduit 21. Exhaust flow 28 contains 0.1 kg / hour water and 0.1 kg / hour ammonium sulfate. Ammonium sulphate crystals are discharged through conduit 29 at a rate of 3.28 kg / hour.

Example 2

1 kg / hour lactam and 1.3 kg / hour sulfuric acid through conduit 1, 0.45 kg / hour ammonia through conduit 2 Feeds 2.51 kg / hr of water. 0.84 kg / hr of steam at 3-4 atmospheres is withdrawn via conduit 4. Dilution vessel B is fed a secondary batch of 1 kg / lactam and 1.3 kg of sulfuric acid via conduit 8 and 1.7 kg of ammonium sulfate and 1.43 kg of water through conduit 6. The mixture is transferred via conduit 10 to extractor C, where the lactam is extracted with 3 kg of chloroform supplied via conduit 11. A solution of ammonium bisulfate containing 3.05 kg NH ₄ HSO ₄ and 3.05 kg water is discharged through conduit 13.

Claims (1)

As described above, the process of neutralizing sulfuric acid using ammonia in the presence of moisture under pressure conditions higher than atmospheric pressure in the absence of a mother liquor containing ammonium sulfate crystals or ammonium sulfate, and the neutralized mixture is used as a lactam layer and an aqueous ammonium sulfate layer. To remove the heat of neutralization by evaporating the water to form water vapor that can be separated by

From reaction mixtures of caprolactam and sulfuric acid

How to recover the caprolactam.

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