A method for synthesizing valerolactam

Abstract

The present invention relates to the chemical industry field, and particularly relates to a method for synthesizing valerolactam. The steps are as follows: cyclopentanone and the reaction auxiliary cyclohexanone are mixed in a certain proportion, and then through ammoximation reaction, Beckmann rearrangement reaction, hydrolysis and neutralization reaction, and then through separation, valerolactam is obtained. The method of the present invention has a high atom utilization rate and a high product extraction rate, and has the prospect of actual industrial production.

Description

Technical Field

[0001] The present invention relates to the chemical industry field, and particularly relates to a method for synthesizing valerolactam. Background Art

[0002] Valerolactam is a chemical product with wide applications and is also one of the important organic chemical raw materials. It can be used to produce plastics, fibers, films, etc. through polymerization and further processing, and has great application potential in the fields of synthetic fiber and plastic production.

[0003] Currently, the methods for synthesizing lactam include Beckmann rearrangement reaction, piperidine oxidation, 1 - amino acid cyclization, and lactone amidation. Among these methods, the Beckmann rearrangement reaction is the main method for synthesizing lactam and is also the current industrial production method for valerolactam. Approximately 90% of the world's valerolactam is prepared by the Beckmann rearrangement reaction of cyclopentanone oxime. The other several methods have disadvantages such as using complex and expensive noble metal catalysts, expensive and scarce starting materials, and too harsh and unsafe production conditions. Taking the preparation of valerolactam as an example, the process of the Beckmann rearrangement reaction is as follows: Fuming sulfuric acid is used to make cyclopentanone oxime form valerolactam sulfate. In this process, an excessive amount of fuming sulfuric acid needs to be added to obtain a high yield of valerolactam, and then the mixture is neutralized with ammonia water to obtain valerolactam and ammonium sulfate. Currently, there is a lack of research on industrial large - scale production methods for valerolactam, and the current valerolactam synthesis methods also have the following practical production problems: (1) The content of oxime in the wastewater from cyclopentanone ammoximation is high, and the loss of oxime is high; (2) The selectivity of the Beckmann rearrangement of cyclopentanone oxime is poor, the consumption of fuming sulfuric acid is high, and the output of ammonium sulfate is large; (3) It is difficult to obtain a benzene solution by benzene extraction of the valerolactam oil after neutralization. In summary, there is an urgent need in the industry to develop an industrial production method for valerolactam. Summary of the Invention

[0004] To solve the technical problems such as high loss of oxime, poor selectivity of Beckmann rearrangement, large output of ammonium sulfate, and difficulty in extraction existing in the existing valerolactam synthesis process, the present invention aims to provide a brand - new method for synthesizing valerolactam, aiming to reduce the oxime content in wastewater, improve the product selectivity, reduce the output of ammonium sulfate, and improve the extraction and separation effect.

[0005] The conversion rate of the valerolactam ammoximation reaction is not ideal, the atom utilization rate is not high, and the extraction rate of the product oil and synthetic wastewater is not high. To address this technical problem, the present invention provides the following improvement solutions:

[0006] A method for synthesizing valerolactam, which mixes cyclopentanone with a reaction assistant, and successively conducts an ammoximation reaction, a Beckmann rearrangement reaction, a hydrolysis and neutralization reaction, then conducts an extraction treatment to obtain a loaded organic phase enriched with valerolactam, and then separates valerolactam from the loaded organic phase;

[0007] The reaction promoter described above is a C6-C 12 aliphatic ketone.

[0008] The present invention has found through research that using the described reaction promoter to assist in the oximation, rearrangement, and neutralization reactions of cyclopentanone helps to improve the atom utilization rate and reduce the content of oxime in the production wastewater; it helps to reduce the acid-oxime ratio of the rearrangement and reduce the output of ammonium sulfate. Moreover, it can also improve the extraction separation selectivity of the product oil and wastewater; it helps to improve the product yield and reduce the difficulty of wastewater treatment. The technical solution of the present invention is applicable to industrial scale-up production.

[0009] In the present invention, in addition to the innovative use of the described reaction promoter, reaction steps such as the ammoximation reaction, Beckmann rearrangement reaction, and hydrolysis and neutralization reaction can all be achieved based on existing means.

[0010] In the present invention, the reaction promoter described above is a C6-C 12 aliphatic chain ketone or cyclohexanone; preferably cyclohexanone; more preferably cyclohexanone.

[0011] In the present invention, the molar ratio of the reaction promoter to cyclopentanone is greater than or equal to 1, preferably 1-10:1.

[0012] In the present invention, the cyclopentanone, reaction promoter, solvent A, hydrogen peroxide, ammonia, and catalyst are subjected to an ammoximation reaction to obtain an oximation product.

[0013] Preferably, the solvent A is a C1-C6 aliphatic alcohol;

[0014] Preferably, in the starting solution of the ammoximation reaction, the volume concentration of the solvent A is 20%-60%;

[0015] Preferably, the total molar ratio of hydrogen peroxide to cyclopentanone and the reaction promoter is 1-2, preferably 1.1-1.3;

[0016] Preferably, the total molar ratio of ammonia to cyclopentanone and the reaction promoter is 1-3, preferably 1.2-1.5;

[0017] Preferably, the catalyst is titanium silicalite; preferably, the dosage of the catalyst is 1-6% by weight of the total weight of the reaction system, more preferably 2-4% by weight.

[0018] Preferably, in the ammoximation reaction, the reaction temperature is 60-100°C, preferably 70-90°C. Preferably, the pressure is 0.1-0.6 MPa, preferably 0.2-0.4 MPa. Preferably, the reaction residence time is 1-3 h, preferably 1.5-2.5 h.

[0019] In the present invention, after the ammoximation reaction, the oxime product therein can be collected based on existing means. For example, the reaction system is filtered to recover the catalyst therein, and then distillation treatment is carried out to recover the solvent A therein. The remaining system is then subjected to oil-water separation, or oil-water separation (extraction) is assisted by a hydrophobic solvent to obtain the oxime product and the wastewater from the ammoximation reaction.

[0020] In the present invention, the oxime product of the ammoximation reaction is mixed with fuming sulfuric acid to carry out a Beckmann rearrangement reaction to obtain a corresponding sulfate product.

[0021] Preferably, the Beckmann rearrangement reaction system is also allowed to contain a solvent B, and the solvent B is a hydrophobic organic solvent. The solvent B can be the hydrophobic solvent that assists in oil-water separation during the oxime treatment process. For example, the system for recovering the solvent A from the ammoximation reaction can be extracted with the solvent B, and the obtained organic phase loaded with the oxime product is directly subjected to the subsequent Beckmann rearrangement reaction.

[0022] Preferably, the solvent B is a hydrophobic organic solvent recovered during the preparation process;

[0023] Preferably, the solvent B is at least one of an alkane, a cycloalkane, and an aromatic hydrocarbon; preferably at least one of cyclopentane and cyclohexane.

[0024] Preferably, in the starting system of the Beckmann rearrangement reaction, the mass concentration of the oxime product is 10-60%, preferably 20-40%.

[0025] Preferably, in the Beckmann rearrangement reaction: the reaction temperature is 70-140 °C, preferably 90-120 °C. Preferably, the pressure is 5-400 KPa, preferably 10-300 KPa. Preferably, the fuming sulfuric acid has a free SO3 content of 3-50% (by weight), and the molar ratio of fuming sulfuric acid to the oxime product (acid-oxime molar ratio) is 1-4, preferably 1.1-1.5. Preferably, the reaction residence time is 5-60 minutes.

[0026] After the rearrangement reaction is completed, optionally, a solvent recovery operation is carried out to obtain the rearrangement product.

[0027] In the present invention, deionized water, ammonia are contacted with the sulfate product of the Beckmann rearrangement reaction to carry out a hydrolysis and neutralization reaction, and then an organic solvent extraction treatment is carried out to obtain a loaded organic phase and an ammonium sulfate aqueous phase.

[0028] Preferably, the temperature of the sulfate hydrolysis and neutralization reaction is 30-80 °C, preferably 40-60 °C. Preferably, the pH value of the aqueous phase during the reaction process and at the end point is controlled to be 4-8, preferably 5-7. Preferably, the reaction pressure is the saturated vapor pressure of water at the reaction temperature.

[0029] In the present invention, the organic solvent for extraction is at least one of benzene and toluene.

[0030] It is found in the research of the present invention that with the assistance of the reaction auxiliary agent, the extraction separation effect of the extractant on valerolactam and wastewater can be unexpectedly improved.

[0031] In the present invention, the loaded organic phase is rectified to recover benzene and valerolactam, and further recover the amide therein.

[0032] A preferred method for preparing valerolactam according to the present invention comprises the following steps:

[0033] Step (1) Ammoximation reaction unit:

[0034] Under the ammoximation reaction conditions, a certain proportion of cyclopentanone, the reaction auxiliary agent cyclohexanone, solvent A, hydrogen peroxide and ammonia are contacted in the presence of a catalyst to carry out an oximation reaction to obtain an ammoximation product (ammoximation reactant, reaction system) containing cyclopentanone oxime;

[0035] Wherein, the molar ratio of the cyclopentanone to the cyclohexanone is 1:1 to 10, preferably 1:1 to 5;

[0036] Wherein, the ammoximation reaction conditions include: the reaction temperature is 60 to 100 °C, preferably 70 to 90 °C; the pressure is 0.1 to 0.6 MPa, preferably 0.2 to 0.4 MPa; the reaction residence time is 1 to 3 h, preferably 1.5 to 2.5 h.

[0037] Wherein, the solvent A is a C1-C6 fatty alcohol, preferably at least one of tert-butanol and isopropanol.

[0038] Wherein, the concentration of the ammoximation reaction solvent A is 20% to 60% by mass percentage; the molar ratio of hydrogen peroxide to ketone is 1 to 2, preferably 1.1 to 1.3; the molar ratio of ammonia to ketone is 1 to 3; preferably 1.2 to 1.5.

[0039] Wherein, the catalyst is titanium silicalite; the dosage of the catalyst is such that based on the total weight of the reaction system, the dosage of the catalyst is 1 to 6% by weight, more preferably 2 to 4% by weight.

[0040] Step (2) Ammoximation separation unit:

[0041] After the ammoximation reactant is rectified to recover the solvent A, the oil and water are phase-separated, or extracted with the solvent B to obtain an organic phase containing the product, and the oximation product is obtained.

[0042] Step (3) Beckmann rearrangement unit:

[0043] Contact oleum with the oximation product in step (2) (the oil-water phase separation product or the organic phase) to carry out the Beckmann rearrangement reaction to obtain the corresponding sulfate product; meanwhile, under the action of the reaction heat, solvent B is recovered through evaporation and condensation;

[0044] Among them, the conditions for the Beckmann rearrangement reaction include: the reaction temperature is 70-140°C, preferably 90-120°C; the pressure is 5-400 KPa, preferably 10-300 KPa, the oleum contains 3-50% (by weight) of free SO3, and the molar ratio of acid to oxime is 1-4, preferably 1.1-1.5; the reaction residence time is 5-60 minutes.

[0045] Among them, the solvent B is at least one of alkanes, cycloalkanes, and aromatic hydrocarbons; preferably at least one of cyclopentane and cyclohexane.

[0046] Among them, the concentration of the oxime in solvent B is 10-60%, preferably 20-40%.

[0047] (4) Hydrolysis and neutralization unit:

[0048] Contact the rearrangement product sulfate with demineralized water and ammonia to obtain an organic phase containing valerolactam and an aqueous phase containing ammonium sulfate crystals;

[0049] Among them, the hydrolysis and neutralization reaction of the sulfate can be carried out simultaneously in a reactor, the reaction temperature is 30-80°C, preferably 40-60°C; the pH value of the aqueous phase is 4-8, preferably 5-7; the reaction pressure is the saturated vapor pressure of water corresponding to the reaction temperature.

[0050] Step (5) Refining unit:

[0051] Extract the organic phase containing valerolactam with benzene, recover benzene in the benzene recovery tower, separate valerolactam in the distillation column and separate to obtain caprolactam.

[0052] The method described in the present invention can reduce the oxime content in the ammoximation wastewater, improve the conversion rate of cyclopentanone oxime and the selectivity of valerolactam, reduce the yield of by-product ammonium sulfate, and can carry out the extraction operation of the neutralized amide oil with benzene.

[0053] Beneficial effects

[0054] With the technical solution of the present invention, with the assistance of the described reaction promoter, the atomic utilization rate of the oximation and rearrangement reactions can be improved, and it is also helpful to improve the extraction effect. Brief description of the drawings

[0055] Figure 1 It is a schematic flow chart of the present invention. Detailed implementation manners

[0056] The present invention will be specifically described below in conjunction with embodiments and the accompanying drawings, but the embodiments do not constitute a limitation to the present invention.

[0057] In the following embodiments, it is carried out in the Figure 1 system shown.

[0058] Ammoximation reaction unit:

[0059] Used for the ammoximation reaction to prepare cyclohexanone oxime and cyclopentanone oxime products;

[0060] Ammoximation separation unit:

[0061] The ammoximation product is treated with a distillation column. Solvent A is recovered from the top of the column, and the bottom material is subjected to oil-water phase separation or extraction with solvent B to remove the ammoximation wastewater, obtaining the oxime product;

[0062] Beckmann rearrangement unit:

[0063] The oxime product is contacted with fuming sulfuric acid to carry out the Beckmann rearrangement reaction to obtain the corresponding sulfate ester product; meanwhile, under the action of the reaction heat, solvent B is recovered through evaporation and condensation;

[0064] Hydrolysis and neutralization unit:

[0065] Desalted water and ammonia are contacted with the rearrangement product sulfate ester to obtain an organic phase containing valerolactam and an aqueous phase containing ammonium sulfate crystals;

[0066] Refining unit:

[0067] The organic phase containing valerolactam is subjected to benzene extraction, benzene recovery in a benzene recovery column, and separation in a distillation column to obtain the target product. For example, valerolactam and caprolactam are obtained.

[0068] The contents of cyclohexanone oxime and cyclopentanone oxime are measured by gas chromatography analysis method;

[0069] The contents of caprolactam and valerolactam are measured by gas chromatography analysis method.

[0070] Unless otherwise specified, the reagents and materials involved in the following embodiments are commercially available.

[0071] In the following embodiments, based on NH3, the concentration of ammonia water is 25% by weight.

[0072] The titanium silicalite molecular sieve used in the following embodiments is purchased from the Research Institute of Petroleum Processing, Sinopec.

[0073] Example 1

[0074] (1) Ammoximation reaction unit: The reaction auxiliaries (cyclohexanone), cyclopentanone, hydrogen peroxide, ammonia water, tert-butanol and TS-1 titanium silicalite molecular sieve carry out the ammoximation reaction in a continuously stirred reaction kettle, and the reaction product is separated from the catalyst by membrane filtration. Among them, the dosage of the catalyst is such that based on the total weight of the reaction system, the dosage of the catalyst is 3% by weight; the mass concentration of tert-butanol in the system is 35%, the molar ratio of cyclohexanone to cyclopentanone is 5, the molar ratio of hydrogen peroxide to ketone (cyclohexanone and cyclopentanone) is 1.1; the molar ratio of ammonia to ketone is 1.2; based on H2O2, the concentration of hydrogen peroxide is 27% by weight; the catalytic ammoximation reaction temperature is 80 °C; the pressure is 300 KPa, and the residence time is 1.5 h.

[0075] (2) Ammoximation separation unit: The ammoximation reaction product is separated from the catalyst by membrane filtration, and then the tert-butanol is recovered by atmospheric distillation in a distillation column. The top temperature of the column is 79 °C, the bottom temperature of the column is 103 °C, and the tert-butanol recovered from the top of the column is returned to the ammoximation unit for recycling. The bottom material of the column is separated into oil and water phases by a phase separator or cyclohexane is added for extraction to obtain a cyclohexane solution with a mass concentration of 20% oxime. The oxime content in the separated ammoximation wastewater is less than 0.1%.

[0076] The ammoximation conversion rate and selectivity are measured, and the specific results are shown in Table 1.

[0077] (3) Beckmann rearrangement unit: Oleum containing free SO3 is added to the cyclohexane solution with a mass concentration of 20% oxime obtained in step (2) to carry out the Beckmann rearrangement reaction to obtain a rearranged reaction product. Among them, the molar ratio of oleum (calculated as sulfuric acid based on SO3 in oleum) to oxime is 1.2, and the concentration of free SO3 in oleum is 5% by weight; the rearrangement reaction temperature is 100 °C, the pressure is 50 KPa (gauge), and the reaction residence time is 30 minutes; during the reaction process, cyclohexane evaporates to the top of the reactor, is condensed and recovered by a condenser and returned to the ammoximation separation unit for recycling.

[0078] (4) Hydrolysis and neutralization unit: The sulfuric acid ester solution obtained in step (3) is added to a hydrolysis and neutralization reactor, and demineralized water and gaseous ammonia are continuously introduced to control the pH value of the aqueous phase to 5. By adjusting the reaction pressure, the reaction temperature is ensured to be 50 °C; the oil and water are phase-separated in the reactor, the upper oil phase is sent to the benzene extraction in the refining unit, and the lower aqueous phase is continuously centrifuged to obtain ammonium sulfate crystals, and the mother liquor is returned to the hydrolysis and neutralization reactor.

[0079] (5) Refining unit: Benzene is added to the oil phase obtained in step (4) for extraction to obtain a benzene solution of caprolactam and valerolactam with a mass concentration of 30%. The raffinate is returned to the hydrolysis and neutralization unit; the benzene solution of caprolactam and valerolactam is stripped of benzene through a distillation column to obtain a mixture of crude caprolactam and valerolactam, and the mixture of crude caprolactam and valerolactam is further separated and refined through a distillation column to obtain caprolactam and valerolactam products.

[0080] The conversion rate and selectivity of the Beckmann rearrangement were measured, and the specific results are shown in Table 2.

[0081] Example 2

[0082] (1) Ammoximation reaction unit: Cyclohexanone, cyclopentanone, hydrogen peroxide, ammonia water, tert-butanol and TS-1 titanium silicalite molecular sieve are subjected to ammoximation reaction in a continuously stirred reaction kettle, and the reaction product is separated from the catalyst by membrane filtration. Among them, the dosage of the catalyst is such that based on the total weight of the reaction system, the dosage of the catalyst is 6% by weight; the mass concentration of tert-butanol in the system is 60%, the molar ratio of cyclohexanone to cyclopentanone is 10, the molar ratio of hydrogen peroxide to ketone is 1; the molar ratio of ammonia to ketone is 3; based on H2O2, the concentration of hydrogen peroxide is 27% by weight; the catalytic ammoximation reaction temperature is 100 °C; the pressure is 600 KPa, and the residence time is 1 h.

[0083] (2) Ammoximation separation unit: The ammoximation reaction product is separated from the catalyst by membrane filtration, and then isopropanol is recovered by atmospheric distillation using a distillation column. The top temperature of the column is 79 °C, the bottom temperature of the column is 105 °C, the tert-butanol recovered from the top of the column is returned to the ammoximation unit for recycling, and the bottom material of the column is separated into oil and water phases through a phase separator or cyclohexane is added for extraction to obtain a cyclohexane solution with a mass concentration of 60% oxime, and the oxime content in the separated ammoximation wastewater is less than 0.1%.

[0084] The conversion rate of the ammoximation reaction and the selectivity of the product were measured, and the specific results are shown in Table 1.

[0085] (3) Beckmann rearrangement unit: Oleum containing free SO3 is added to the cyclohexane solution with a mass concentration of 60% oxime obtained in step (2) for Beckmann rearrangement reaction to obtain a rearrangement reactant. Among them, the molar ratio of oleum (calculated as sulfuric acid based on SO3 in oleum) to oxime is 4, and the concentration of free SO3 in oleum is 50% by weight; the rearrangement reaction temperature is 140 °C, the pressure is 400 KPa (gauge), and the reaction residence time is 5 minutes; during the reaction process, cyclohexane evaporates to the top of the reactor, is condensed and recovered through a condenser and returned to the ammoximation separation unit for recycling.

[0086] (4) Hydrolysis and Neutralization Unit: Add the sulfate ester solution obtained in step (3) into the hydrolysis and neutralization reactor, continuously introduce demineralized water and gaseous ammonia, control the pH value of the aqueous phase to be 8, and ensure the reaction temperature is 60 °C by adjusting the reaction pressure; the oil and water are separated in the reactor, the upper oil phase is discharged and sent to the benzene extraction in the refining unit, and the lower aqueous phase is continuously centrifuged to obtain ammonium sulfate crystals, and the mother liquor is returned to the hydrolysis and neutralization reactor.

[0087] (5) Refining Unit: Add benzene to the oil phase obtained in step (4) for extraction to obtain a benzene solution of caprolactam and valerolactam with a mass concentration of 35%; the raffinate is returned to the hydrolysis and neutralization unit; the benzene solution of caprolactam and valerolactam is distilled in a distillation column to remove benzene to obtain a mixture of crude caprolactam and valerolactam, and the mixture of crude caprolactam and valerolactam is further separated and refined in a distillation column to obtain caprolactam and valerolactam products.

[0088] The conversion rate and selectivity of the Beckmann rearrangement were measured, and the specific results are shown in Table 2.

[0089] Example 3

[0090] This example is used to illustrate the method for co-producing caprolactam and valerolactam according to the present invention

[0091] (1) Oximation Reaction Unit: Cyclohexanone, cyclopentanone, hydrogen peroxide, ammonia water, tert-butanol and TS-1 titanium silicalite are subjected to an ammoximation reaction in a continuously stirred reaction kettle, and the reaction product is separated from the catalyst by membrane filtration. Among them, the dosage of the catalyst is such that based on the total weight of the reaction system, the dosage of the catalyst is 1% by weight; the mass concentration of tert-butanol in the system is 20%, the molar ratio of cyclohexanone to cyclopentanone is 1, the molar ratio of hydrogen peroxide to ketone is 2; the molar ratio of ammonia to ketone is 1; based on H2O2, the concentration of hydrogen peroxide is 27% by weight; the catalytic oximation reaction temperature is 60 °C; the pressure is 100 KPa, and the residence time is 3 h.

[0092] (2) Ammoximation Separation Unit: The ammoximation reaction product is separated from the catalyst by membrane filtration, and then the tert-butanol is recovered by atmospheric distillation in a distillation column. The top temperature of the column is 79 °C, the bottom temperature of the column is 102 °C, and the tert-butanol recovered from the top is returned to the ammoximation unit for recycling. The material at the bottom of the column is extracted with cyclopentane to obtain a cyclopentane solution with a mass concentration of 10% oxime, and the oxime content in the separated ammoximation wastewater is less than 0.1%.

[0093] The ammoximation conversion rate and product selectivity were measured, and the specific results are shown in Table 1.

[0094] (3) Beckmann Rearrangement Unit: Oleum containing free SO3 is added to the cyclopentane solution of oxime with a mass concentration of 10% obtained in step (2) to carry out the Beckmann rearrangement reaction, and a rearranged reaction product is obtained. Among them, the molar ratio of oleum (calculated as sulfuric acid based on SO3 in oleum) to oxime is 1, and the concentration of free SO3 in oleum is 3% by weight; the rearrangement reaction temperature is 70 °C, the pressure is 5 KPa (gauge), and the reaction residence time is 60 minutes; during the reaction process, cyclopentane evaporates to the top of the reactor, is condensed and recovered by a condenser and returned to the ammoximation separation unit for recycling.

[0095] (4) Hydrolysis and Neutralization Unit: The sulfuric acid ester solution obtained in step (3) is added to a hydrolysis and neutralization reactor, and demineralized water and gaseous ammonia are continuously introduced. The pH value of the aqueous phase is controlled to be 4, and the reaction temperature is ensured to be 30 °C by adjusting the reaction pressure; the oil and water are phase-separated in the reactor, the upper oil phase is sent to the benzene extraction in the refining unit, and the lower aqueous phase is continuously centrifuged to obtain ammonium sulfate crystals, and the mother liquor is returned to the hydrolysis and neutralization reactor.

[0096] (5) Refining Unit: The oil phase obtained in step (4) is added with benzene for extraction to obtain a benzene solution of caprolactam and valerolactam with a mass concentration of 20%. The raffinate is returned to the hydrolysis and neutralization unit; the benzene solution of caprolactam and valerolactam is distilled to remove benzene to obtain a mixture of crude caprolactam and valerolactam, and the mixture of crude caprolactam and valerolactam is further separated and refined by a distillation column to obtain caprolactam and valerolactam products.

[0097] The conversion rate and selectivity of the Beckmann rearrangement were measured, and the specific results are shown in Table 2.

[0098] Example 4

[0099] The operation was carried out according to the method of Example 1, except that isopropanol with the same concentration was used instead of tert-butanol in the ammoximation unit.

[0100] The measurement results are shown in Table 1

[0101] Example 5

[0102] The operation was carried out according to the method of Example 1, except that in the ammoximation separation unit, instead of using solvent B to extract oxime, the ammoximation reaction product was distilled to recover solvent A, and the oil and water were phase-separated to remove the ammoximation wastewater to obtain an oxime product; in the Beckmann rearrangement unit, the rearrangement reaction was carried out under the same acid-oxime ratio, reaction temperature and pressure and other conditions.

[0103] The measurement results are shown in Tables 1 and 2.

[0104] Comparative Example 1

[0105] Compared with Example 1, the only difference is that no reaction auxiliary cyclohexanone is added to the ammoximation unit, the oxime content in the ammoximation wastewater after separation by the ammoximation separation unit is greater than 3%; the selectivity of valerolactam in the Beckmann rearrangement unit is reduced to 95.1%; the valerolactam concentration in the benzene extract of the refining unit is lower than 1%.

[0106] The measurement results are shown in Tables 1 and 2.

[0107] Comparative Example 2

[0108] Compared with Example 1, the only difference is that no reaction auxiliary cyclohexanone is added to the ammoximation unit, the oxime content in the ammoximation wastewater after separation by the ammoximation separation unit is greater than 3%; the acid-oxime molar ratio in the Beckmann rearrangement unit is increased to 3, and the selectivity of valerolactam is increased to 99.5%; the valerolactam concentration in the benzene extract of the refining unit is lower than 1%.

[0109] The measurement results are shown in Tables 1 and 2.

[0110] Table 1

[0111]

[0112] Table 2

[0113]

[0114] It can be seen from the results of Table 1 and Table 2 that by using the method of the present invention, not only can high conversion rates and selectivities be ensured when preparing caprolactam and valerolactam, but also the oxime concentration in the ammoximation wastewater can be reduced, the loss of oxime can be reduced, and the yield of ammonium sulfate when preparing valerolactam alone can be significantly reduced.

[0115] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for synthesizing valerolactam, characterized in that, Perform an ammoximation reaction on cyclopentanone, a reaction auxiliary, solvent A, hydrogen peroxide, ammonia, and a catalyst to obtain an oxime product; mix the oxime product with fuming sulfuric acid to perform a Beckmann rearrangement reaction to obtain a corresponding sulfate product; contact the sulfate product with demineralized water and ammonia to perform a hydrolysis and neutralization reaction, and then perform an organic solvent extraction treatment to obtain a loaded organic phase and an ammonium sulfate aqueous phase; separate valerolactam from the loaded organic phase. The reaction auxiliary is cyclohexanone. The molar ratio of the reaction auxiliary to cyclopentanone is 1 - 10:

1. The organic solvent for extraction is at least one of benzene and toluene. Solvent A is a C1 - C6 fatty alcohol.

2. The method according to claim 1, characterized in that In the starting solution of the ammoximation reaction, the volume concentration of solvent A is 20% - 60%.

3. The method according to claim 1, characterized in that, The total molar ratio of hydrogen peroxide to cyclopentanone and the reaction auxiliary is 1 - 2. The total molar ratio of ammonia to cyclopentanone and the reaction auxiliary is 1 - 3. The catalyst is titanium silicalite molecular sieve. The dosage of the catalyst is 1 - 6% by weight of the total weight of the reaction system.

4. The method according to claim 3, characterized in that The total molar ratio of hydrogen peroxide to cyclopentanone and the reaction auxiliary is 1.1 - 1.

3. The total molar ratio of ammonia to cyclopentanone and the reaction auxiliary is 1.2 - 1.

5. The dosage of the catalyst is 2 - 4% by weight of the total weight of the reaction system.

5. The method according to claim 1, characterized in that, In the ammoximation reaction, the reaction temperature is 60 - 100°C; the pressure is 0.1 - 0.6 MPa; the reaction residence time is 1 - 3 h.

6. The method according to claim 5, characterized in that In the ammoximation reaction, the reaction temperature is 70 - 90°C; the pressure is 0.2 - 0.4 MPa; the reaction residence time is 1.5 - 2.5 h.

7. The method according to claim 1, wherein The Beckmann rearrangement reaction system further contains solvent B, and the solvent B is a hydrophobic organic solvent.

8. The method according to claim 7, characterized in that Solvent B is a hydrophobic organic solvent recovered during the preparation process.

9. The method according to claim 7, characterized in that, The solvent B is at least one of alkanes, cycloalkanes, and aromatic hydrocarbons.

10. The method according to claim 7, wherein The solvent B is at least one of cyclopentane and cyclohexane.

11. The method according to claim 1, wherein In the starting system of the Beckmann rearrangement reaction, the mass concentration of the oxime product is 10 - 60%.

12. The method according to claim 11, wherein In the starting system of the Beckmann rearrangement reaction, the mass concentration of the oxime product is 20 - 40%.

13. The method according to claim 1, wherein In the Beckmann rearrangement reaction: the reaction temperature is 70 - 140°C; the pressure is 5 - 400 KPa; the fuming sulfuric acid has a free SO3 weight content of 3 - 50%, and the molar ratio of the fuming sulfuric acid to the oxime product is 1 - 4; the reaction residence time is 5 - 60 minutes.

14. The method according to claim 13, wherein In the Beckmann rearrangement reaction: the reaction temperature is 90 - 120°C; the pressure is 10 - 300 KPa; the molar ratio of the fuming sulfuric acid to the oxime product is 1.1 - 1.

5.

15. The method according to claim 1, wherein The temperature of the sulfate hydrolysis and neutralization reaction is 30 - 80°C; Control the pH value of the aqueous phase during the reaction process and at the end point to be 4 - 8; The reaction pressure is the saturated vapor pressure of water corresponding to the reaction temperature.

16. The method according to claim 15, wherein The temperature of the sulfate hydrolysis and neutralization reaction is 40 - 60°C; Control the pH value of the aqueous phase during the reaction process and at the end point to be 5 - 7.

17. The method according to claim 1, characterized in that, Perform rectification on the loaded organic phase to recover benzene and valerolactam, and further recover the amide therein.

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