Resin catalyst having nanosphere structure, and preparation method and application thereof, and preparation method of caprolactam

Abstract

The application discloses a resin catalyst with a nanosphere structure and a preparation method and application thereof, and a preparation method of caprolactam; the resin catalyst with the nanosphere structure comprises a polystyrene-divinylbenzene nanosphere structure resin and a sulfonic acid group, and the sulfonic acid group is located on a benzene ring of the polystyrene-divinylbenzene nanosphere structure resin; the catalyst is suitable for the preparation of caprolactam through a Beckmann liquid phase rearrangement, and can exhibit excellent raw material conversion rate and product selectivity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of Beckmann liquid phase rearrangement reaction catalyst, and particularly relates to a resin type catalyst with nanosphere structure, a preparation method and application thereof, and a preparation method of caprolactam. BACKGROUND

[0002] Caprolactam is an important chemical raw material monomer for producing synthetic fibers and engineering plastics. The technical route for preparing caprolactam in industry is mainly divided into gas phase and liquid phase. Among them, the liquid phase Beckmann rearrangement process taking oleum as a catalyst is the most widely used production route. In this process, caprolactam is obtained by Beckmann rearrangement reaction of raw material cyclohexanone oxime with oleum as a catalyst. Ammonia is also introduced in the reaction to neutralize a large amount of strong acid in the reaction system and produce by-product ammonium sulfate with low economic value. The process condition is mature, and the raw material conversion rate and product selectivity are relatively high. However, there are defects such as corrosion of concentrated sulfuric acid to production equipment and low economic value of by-product, which does not meet the concept of sustainable development.

[0003] In the gas phase Beckmann rearrangement reaction, different silica-alumina materials, zeolites and mixed oxides have been used as catalysts. However, the gas phase Beckmann rearrangement usually consumes a lot of energy because it usually needs to be carried out above 300℃, which also causes the catalyst to be quickly deactivated due to coking. Although the liquid phase Beckmann rearrangement process can be carried out under relatively mild reaction conditions and the target amide is easy to obtain, the strong acid cation exchange resin catalyst does not perform well in this reaction. SUMMARY

[0004] The present application provides a resin type catalyst with nanosphere structure, a preparation method and application thereof. The resin type catalyst with nanosphere structure provided by the present application is suitable for preparing caprolactam by Beckmann liquid phase rearrangement and can exhibit excellent raw material conversion rate and product selectivity.

[0005] In the first aspect, the present application provides a resin type catalyst with nanosphere structure, which comprises a polystyrene-divinylbenzene nanosphere structure resin and a sulfonic acid group, and the sulfonic acid group is located on the benzene ring of the polystyrene-divinylbenzene nanosphere structure resin.

[0006] In some embodiments, the resin type catalyst has a mesoporous structure, and the specific surface area of the resin type catalyst is 9-13 m2·g -1 , and the pore volume is 0.01-0.02 cm 3 ·g -1 .

[0007] In some embodiments, the thermal decomposition temperature of the resin type catalyst with nanosphere structure is greater than 200℃.

[0008] In a second aspect, the embodiments of the present application provide a preparation method of a resin catalyst with nanosphere structure, comprising the following steps:

[0009] (1) mixing styrene monomer, divinylbenzene, stabilizer, initiator, pore-forming agent and deionized water, and stirring under constant temperature and inert gas atmosphere to obtain polystyrene-divinylbenzene nanosphere structure resin;

[0010] (2) drying the polystyrene-divinylbenzene nanosphere structure resin, adding the dried polystyrene-divinylbenzene nanosphere structure resin into an organic solvent for sufficient swelling, and then adding a sulfonating agent to incorporate sulfonic acid groups into the polystyrene-divinylbenzene nanosphere structure resin;

[0011] (3) obtaining the resin catalyst with nanosphere structure after filtration, washing and high-temperature drying.

[0012] In some embodiments, the amount of divinylbenzene added in step (1) is 10%-30% of the amount of styrene added, calculated by volume.

[0013] In some embodiments, in step (2), the sulfonating agent comprises at least one of concentrated sulfuric acid and chlorosulfonic acid.

[0014] In some embodiments, in step (1), the stabilizer comprises polyvinylpyrrolidone, the initiator comprises potassium persulfate, and the pore-forming agent comprises at least one of toluene and n-heptane; in step (2), the organic solvent comprises at least one of n-hexane, dichloroethane, acetone, dimethylformamide and toluene.

[0015] In a third aspect, the embodiments of the present application provide an application of a resin catalyst with nanosphere structure in Beckmann liquid phase rearrangement reaction.

[0016] In a fourth aspect, the embodiments of the present application provide a preparation method of caprolactam, comprising the following steps: taking cyclohexanone oxime as a reaction raw material, dimethyl sulfoxide as a reaction solvent, and performing Beckmann reaction under the catalysis of a resin catalyst with nanosphere structure to obtain caprolactam.

[0017] In some embodiments, the reaction temperature is 130-150℃.

[0018] In some embodiments, the amount of the resin catalyst with nanosphere structure added is 37.5%-75% of the cyclohexanone oxime, by mass percentage.

[0019] According to the technical scheme, the resin catalyst with the nanosphere structure is suitable for preparing caprolactam through Beckmann liquid phase rearrangement, and can exhibit excellent raw material conversion rate and product selectivity. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0021] Figure 1 A Fourier infrared spectrum of the resin catalyst with the nanosphere structure provided by some embodiments of the present application is shown;

[0022] Figure 2A An X-ray photoelectron spectrum of the resin catalyst with the nanosphere structure provided by some embodiments of the present application is shown;

[0023] Figure 2B An X-ray photoelectron spectrum corresponding to C1s in the Figure 2A

[0024] Figure 2C An X-ray photoelectron spectrum corresponding to S2p in the Figure 2A

[0025] Figure 3 A thermogravimetric analysis diagram of the resin catalyst with the nanosphere structure provided by some embodiments of the present application is shown;

[0026] Figure 4A A scanning electron microscope diagram of the catalyst prepared by some embodiments of the present application is shown;

[0027] Figure 4B A scanning electron microscope diagram of the catalyst prepared by some embodiments of the present application is shown;

[0028] Figure 4C A scanning electron microscope diagram of the catalyst prepared by some embodiments of the present application is shown;

[0029] Figure 4D A scanning electron microscope diagram of the catalyst prepared by some embodiments of the present application is shown;

[0030] Figure 5 A transmission electron microscope diagram of the catalyst prepared by some embodiments of the present application is shown. DETAILED DESCRIPTION

[0031] ​​To facilitate understanding of this specification, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this specification are shown in the drawings. However, this specification can be implemented in many different forms without departing from the core spirit of this specification and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this specification.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this specification belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this specification. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0033] In a first aspect, embodiments of this application provide a resin-type catalyst with a nanosphere structure, comprising a polystyrene-divinylbenzene nanosphere structure resin and sulfonic acid groups, wherein the sulfonic acid groups are located on the benzene ring of the polystyrene-divinylbenzene nanosphere structure resin.

[0034] Figure 1 Fourier transform infrared spectra of resin-type catalysts with nanosphere structures provided in some embodiments of this application. Figure 1 As shown, 1600cm -1 and 1448cm -1 The peak appearing at 1035 cm⁻¹ is due to the C=C skeletal vibration of the benzene ring. -1 The wavelength at 1216cm belongs to the CS vibration. -1 and 1161cm -1 The frequency bands at these locations represent the asymmetric and symmetric extension signals of the O=S=O bonds of the sulfonic acid group, respectively. These results indicate that sulfonic acid groups have been successfully introduced onto the aromatic ring of the polystyrene-divinylbenzene nanosphere structure resin.

[0035] Figures 2A-2C X-ray photoelectron spectroscopy (XPS) spectra of resin-type catalysts with nanosphere structures provided in some embodiments of this application. Figures 2A-2C As shown, characteristic signals of C, S, and O elements in the sample can be observed. The S2p and S2s peaks at 169.1 eV and 232.1 eV are related to SO and S=O bonds, respectively. The C 1s spectrum shows two binding energies, with peaks at 284.8 eV and 286.4 eV, which are related to C-C and C-S bonds, respectively. These results indicate the presence of sulfonic acid groups in the resin-type catalyst with the nanosphere structure, which is consistent with the Fourier transform infrared spectroscopy results.

[0036] In some embodiments of the present application, the volume ratio of divinylbenzene to styrene in the synthesis of the polystyrene-divinylbenzene nanosphere structured resin is 10%-30%.

[0037] In some embodiments of the present application, the resin catalyst has a mesoporous structure, and the specific surface area of the resin catalyst is 9-13m 2 -1 3 -1

[0038] The resin catalyst provided in the embodiments of the present application has a nanosphere structure, and the diameter of the nanosphere is between 100-500nm. The resin catalyst has a mesopore, and the pore diameter of the mesopore is in the range of 10-30nm, for example, the pore diameter of the mesopore can be 10nm, 15nm, 20nm, 25nm, 30nm, or any value between any two of the above pore diameters. The nitrogen adsorption and desorption test (BET test) is performed on the resin catalyst, and the specific surface area of the resin catalyst is in the range of 9-13m 2 -1 2 -1 2 -1 2 -1 2 -1 2 -1 3 -1 3 -1 3 -1 3 -1 3 -1 3 -1 3 -1

[0039] Therefore, the resin catalyst has a loose and porous structure inside, can accommodate a large amount of gas, and provides a large number of active adsorption sites, thereby exhibiting good catalytic activity. ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​

[0040] Figure 3 This is a schematic diagram of thermogravimetric analysis (TG) of resin-type catalysts with nanosphere structures provided in some embodiments of this application. Figure 3 As shown, the initial mass loss observed at 200°C corresponds to the elimination of physically adsorbed molecular water; then, the mass loss occurring in the 200-400°C range corresponds to the decomposition of sulfonic acid groups; subsequent mass losses mainly correspond to the collapse of the polymer backbone. The resin-type catalyst with a nanosphere structure provided in this application exhibits high thermal decomposition temperatures exceeding 200°C for its sulfonic acid groups. This temperature exceeds the suitable temperature range for liquid-phase Beckmann rearrangement, indicating that the resin-type catalyst with a nanosphere structure provided in this application is suitable for liquid-phase Beckmann rearrangement reactions.

[0041] Secondly, embodiments of this application provide a method for preparing a resin-type catalyst with a nanosphere structure, comprising the following steps:

[0042] (1) Styrene monomer, divinylbenzene, stabilizer, initiator, pore-forming agent and deionized water are thoroughly mixed and stirred under constant temperature and inert gas atmosphere to obtain polystyrene-divinylbenzene nanosphere structure resin.

[0043] (2) The polystyrene-divinylbenzene nanosphere structure resin is dried and then added to an organic solvent to fully swell. After that, a sulfonating agent is added to incorporate sulfonic acid groups into the polystyrene-divinylbenzene nanosphere structure resin.

[0044] (3) After filtration, washing and high-temperature drying, a resin-type catalyst with a nanosphere structure is obtained.

[0045] Specifically, this application provides a method for preparing a resin-type catalyst with a nanosphere structure, which may include the following steps:

[0046] (1) Styrene monomer, divinylbenzene, stabilizer, initiator, pore-forming agent and deionized water are thoroughly mixed and stirred in a constant temperature (50-90℃) and inert gas (at least one of nitrogen or helium) atmosphere (mechanical stirring intensity of 150rpm-500rpm, stirring time of 12-48h) to obtain polystyrene-divinylbenzene nanosphere structure resin.

[0047] (2) drying the polystyrene-divinylbenzene nanosphere structure resin (drying temperature: 90-140℃, drying time: 6-24h), and adding the dried polystyrene-divinylbenzene nanosphere structure resin into an organic solvent to swell it (swelling time: 1-5h), and then adding a sulfonating agent to incorporate sulfonic acid groups into the polystyrene-divinylbenzene nanosphere structure resin (sulfonation temperature: 70-130℃, sulfonation time: 1-5h);

[0048] (3) obtaining the resin type catalyst with nanosphere structure through filtration, washing and high-temperature drying.

[0049] In some embodiments of the present application, the amount of divinylbenzene added in step (1) is 10%-30% of the amount of styrene added, calculated by volume. For example, in step (1), the volume of divinylbenzene added can be 10%, 15%, 20%, 25%, 30% of the volume of styrene added, or a value between any two of the above-mentioned volume ratios.

[0050] In some embodiments of the present application, in step (2), the sulfonating agent includes at least one of concentrated sulfuric acid and chlorosulfonic acid. The mass percentage of sulfuric acid in the concentrated sulfuric acid is greater than or equal to 98%.

[0051] In some embodiments of the present application, in step (1), the stabilizer includes polyvinylpyrrolidone, the initiator includes potassium persulfate, and the pore-forming agent includes at least one of toluene and n-heptane; in step (2), the organic solvent includes at least one of n-hexane, dichloroethane, acetone, dimethylformamide and toluene.

[0052] In a third aspect, the embodiments of the present application provide an application of the resin type catalyst with nanosphere structure in Beckmann liquid phase rearrangement reaction. The application of the resin type catalyst with nanosphere structure provided by the embodiments of the present application in Beckmann liquid phase rearrangement reaction can avoid the shortcomings of the production process of caprolactam caused by the use of fuming sulfuric acid as the catalyst for Beckmann liquid phase rearrangement reaction, and at the same time, a simple and efficient method for preparing caprolactam is provided.

[0053] In a fourth aspect, the embodiments of the present application provide a preparation method of caprolactam, which includes the following steps: taking cyclohexanone oxime as a reaction raw material, dimethyl sulfoxide as a reaction solvent, and performing Beckmann reaction under the catalysis of the resin type catalyst with nanosphere structure to obtain caprolactam.

[0054] In some embodiments of the present application, the reaction temperature is 130-150℃. It is found through a large number of experiments that, in the process of preparing caprolactam by Beckmann reaction, the reaction temperature needs to be controlled within an appropriate range, so as to show excellent raw material conversion rate and product selectivity.

[0055] In some embodiments of the present application, the amount of the resin-type catalyst with nanosphere structure added is 37.5%-75% of cyclohexanone oxime by mass percentage. Through a large number of experiments, it is found that in the process of preparing caprolactam by Beckmann reaction, the amount of the resin-type catalyst with nanosphere structure added directly affects the raw material conversion rate and product selectivity. Controlling the amount of the resin-type catalyst with nanosphere structure added in the range of 37.5%-75% of the mass of cyclohexanone oxime can make the reaction exhibit excellent raw material conversion rate and product selectivity.

[0056] The following are specific preparation examples related to the above content of the present disclosure. It needs to be made clear that the following examples are only for illustrating the resin-type catalyst with nanosphere structure and its preparation method and application disclosed above, and the specific embodiments and parameters used are only one or several methods among the numerous processes and methods disclosed above. Those skilled in the art can use other parameters to prepare the resin-type catalyst with nanosphere structure according to the above method without departing from the core spirit disclosed in the application.

[0057] For the convenience of illustration, SP(St-DVB)-X is used in the following examples and comparative examples to represent the resin-type catalyst with nanosphere structure prepared by different amounts of divinylbenzene. Among them, S represents sulfonic acid functionalization, P(St-DVB) represents copolymerization of styrene and divinylbenzene, and X represents the volume ratio of divinylbenzene to styrene when the resin-type catalyst with nanosphere structure is synthesized.

[0058] The calculation formulae of the conversion rate of cyclohexanone oxime and the selectivity of caprolactam involved in Test Example 1-Test Example 4 are as follows:

[0059] Cyclohexanone oxime conversion rate (%) = (molar amount of reacted cyclohexanone oxime / molar amount of added cyclohexanone oxime) x 100%;

[0060] Caprolactam selectivity (%) = (molar amount of generated caprolactam / molar amount of reacted cyclohexanone oxime) x 100%.

[0061] Examples 1-6

[0062] Examples 1-6 respectively provide a resin-type catalyst with nanosphere structure, and the preparation method thereof includes the following steps:

[0063] (1) 13 ml of styrene, different amounts of divinylbenzene, 1.1 g of polyvinylpyrrolidone, 0.3 g of potassium persulfate and 13 ml of n-heptane were thoroughly mixed in a nitrogen atmosphere. The mixture was kept at 70 °C and mechanical stirring intensity of 350 rpm for 24 h, then cooled to room temperature, filtered, washed with water, and dried at 120 °C for 12 h to obtain polystyrene-divinylbenzene nanosphere resin.

[0064] (2) Add 3g of polystyrene-divinylbenzene nanosphere resin to 40ml of dichloroethane and let it swell for 1h. Then add 62.5g of concentrated sulfuric acid (GR, wt%: 98%) and stir thoroughly at 90℃ for 3h.

[0065] (3) The mixture was cooled to room temperature, then vacuum filtered, washed with deionized water and anhydrous ethanol until the filtrate was neutral, and dried thoroughly in air at 120°C for 12 hours to obtain a resin catalyst with a nanosphere structure.

[0066] The reagents used in Examples 1-6 were sourced from the following sources:

[0067] Styrene: 99%, containing 10-15 ppm 4-tert-butylcatechol stabilizer, brand name S817905, purchased from Shanghai Maclean Biochemical Technology Co., Ltd., purified with 0.1M NaOH aqueous solution before use;

[0068] Divinylbenzene: 80%, isomer mixture, containing 0.1% TBC stabilizer, brand name D806655, purchased from Shanghai Maclean Biochemical Technology Co., Ltd., distilled under vacuum conditions before use;

[0069] Polyvinylpyrrolidone: Average molecular weight: 58,000, K29-32, grade P816205, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0070] Potassium persulfate: Purity: >99.5%, grade 82459A, purchased from Beijing Innocare Technology Co., Ltd.;

[0071] n-Heptane: Purity: >99%, Grade: H108111, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0072] Dichloroethane: Purity: 99.5%, grade D807843, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0073] Concentrated sulfuric acid: purity: 98.0%, grade: 10021608, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0074] Table 1 shows the amount of divinylbenzene added in step (1) of different examples from Examples 1 to 6, as well as the corresponding resin-type catalysts with nanosphere structures prepared.

[0075] Table 1. Preparation details of Examples 1-6

[0076] Number Amount of divinylbenzene used / ml Catalyst product Example 1 0.65 SP (St-DVB) - 5 Example 2 1.3 SP (St-DVB) - 10 Example 3 1.95 SP (St-DVB) - 15 Example 4 2.6 SP (St-DVB) - 20 Example 5 3.25 SP (St-DVB) - 25 Example 6 3.9 SP (St-DVB) - 30

[0077] The Fourier transform infrared spectra of the SP(St-DVB)-X catalysts prepared in Examples 2-6 are shown below. Figure 1 As shown, 1600cm -1 and 1448cm -1 The peak appearing at 1035 cm⁻¹ is due to the C=C skeletal vibration of the benzene ring. -1 The wavelength at 1216cm belongs to the CS vibration. -1 and 1161cm -1 The frequency bands at these locations represent the asymmetric and symmetric extension signals of the O=S=O bonds of the sulfonic acid group, respectively. These results indicate that sulfonic acid groups have been successfully introduced onto the aromatic ring of the polystyrene-divinylbenzene nanosphere structure resin.

[0078] Thermogravimetric analysis (TG) schematic diagrams of the SP(St-DVB)-X catalysts prepared in Examples 2, 4, and 6 are shown below. Figure 3 As shown, the initial mass loss observed at 200°C corresponds to the elimination of physically adsorbed molecular water; then, the mass loss occurring in the 200-400°C range corresponds to the decomposition of sulfonic acid groups; subsequent mass losses mainly correspond to the collapse of the polymer backbone. The resin-type catalyst with a nanosphere structure provided in this application exhibits high thermal decomposition temperatures exceeding 200°C for its sulfonic acid groups. This temperature exceeds the suitable temperature range for liquid-phase Beckmann rearrangement, indicating that the resin-type catalyst with a nanosphere structure provided in this application is suitable for liquid-phase Beckmann rearrangement reactions.

[0079] Figure 4A This is a scanning electron microscope image of the catalyst prepared in Example 1. Figure 4B This is a scanning electron microscope image of the catalyst prepared in Example 2. Figure 4C This is a scanning electron microscope image of the catalyst prepared in Example 4. Figure 4D This is a scanning electron microscope (SEM) image of the catalyst prepared in Example 6. Figures 4A-4DAs shown, the SP(St-DVB)-5 catalyst's main framework is polystyrene, which is dissolved and destroyed by dichloroethane during sulfonation, forming a dense amorphous structure with numerous particles on its surface. The SP(St-DVB)-10 catalyst exhibits a smooth surface and dispersed polymer microspheres. With increasing divinylbenzene addition, the surface of the SP(St-DVB)-X catalyst gradually becomes rougher, and the spherical structure gradually deforms. Therefore, a 10% divinylbenzene addition helps stabilize the SP(St-DVB)-X catalyst's framework, while excessively high amounts can lead to nanosphere deformation, affecting the catalytic activity of the solid acid.

[0080] Figure 5 This is a transmission electron microscope (TEM) image of the catalyst prepared in Example 2. Figure 5 As shown, the SP(St-DVB)-10 catalyst is a dispersed microsphere with a smooth surface.

[0081] The SP(St-DVB)-X catalysts prepared in Examples 1-6 were subjected to nitrogen adsorption-desorption tests (BET tests), and the test results are shown in Table 2.

[0082] Table 2. BET test results of SP(St-DVB)-X catalysts in Examples 1-6

[0083]

[0084] Table 2 shows that mesopores exist in the SP(St-DVB)-X catalyst, which promotes the free diffusion of reactants and products within the catalyst. The polymer pore size and the number of acidic sites do not change linearly with the amount of divinylbenzene added. Both the pore size and the number of acidic sites reach their maximum values ​​of 29.01 nm and 4.46 mmol / g, respectively, when the divinylbenzene addition is 20%. The amount of divinylbenzene added has a significant impact on the microstructure and the number of acidic sites of the synthesized solid acid catalyst. A divinylbenzene addition of 20% helps to form larger pores and introduce a large number of sulfonic acid groups into the solid acid.

[0085] Test Example 1

[0086] In this test example, the SP(St-DVB)-X catalyst prepared in Examples 1-6 was used in the Beckman liquid-phase rearrangement reaction. Cyclohexanone oxime was used as the reactant and dimethyl sulfoxide was used as the reaction solvent. The reaction was carried out under the catalysis of the SP(St-DVB)-X catalyst to obtain the reaction product caprolactam.

[0087] Specifically, the method for preparing caprolactam using the Beckmann reaction includes the following steps: 2g of cyclohexanone oxime and 20ml of dimethyl sulfoxide are added to a 50ml high-pressure reactor, then 1g of SP(St-DVB)-X catalyst is added, nitrogen gas is purged to replace the original gas in the high-pressure reactor three times, and finally the reaction pressure in the high-pressure reactor is maintained at 0.5MPa. The reaction temperature is set to 130℃, and after reacting for 1h, the reactor is cooled and the upper liquid phase reaction product is collected. After thorough centrifugation, the product composition is quantitatively analyzed by gas chromatography. The results are shown in Table 3.

[0088] As a control, this test example also used a commercially available strong acid cation exchange resin catalyst (Amberlyst 15) in the Beckman liquid-phase rearrangement reaction, including the following steps: 2g of cyclohexanone oxime and 20ml of dimethyl sulfoxide were added to a 50ml high-pressure reactor, followed by the addition of 1g of Amberlyst 15. Nitrogen gas was purged three times to replace the original gas in the high-pressure reactor, and the reaction pressure in the high-pressure reactor was finally maintained at 0.5MPa. The reaction temperature was set to 130℃, and after 1h of reaction, the reactor was cooled and the upper liquid phase reaction product was collected. After thorough centrifugation, the product composition was quantitatively analyzed by gas chromatography. The results are shown in Table 3.

[0089] Table 3. Reaction results of Test Example 1

[0090]

[0091] As shown in Table 3, compared with Comparative Example 1, the SP(St-DVB)-X catalyst prepared by Examples 1-6 has better catalytic performance than the commercial strong acid cation exchange resin catalyst (Amberlyst 15).

[0092] Test Example 2

[0093] This test example uses the SP(St-DVB)-10 catalyst prepared in Example 2 in the Beckmann liquid-phase rearrangement reaction to investigate the effect of different catalyst dosages on the reaction. Specifically, the method for preparing caprolactam using the Beckmann reaction includes the following steps: 2g of cyclohexanone oxime and 20ml of dimethyl sulfoxide are added to a 50ml high-pressure reactor, then different amounts of SP(St-DVB)-10 catalyst are added, nitrogen gas is purged to replace the original gas in the high-pressure reactor three times, and finally the reaction pressure in the high-pressure reactor is maintained at 0.5MPa. The reaction temperature is set to 130℃, and after reacting for 1h, the reactor is cooled and the upper liquid phase reaction product is collected. After thorough centrifugation, the product composition is quantitatively analyzed by gas chromatography, and the results are shown in Table 4.

[0094] Table 4. Reaction results of Test Example 2

[0095]

[0096] As shown in Table 4, the conversion rate of cyclohexanone oxime increases with the increase of catalyst dosage, but the selectivity of caprolactam fluctuates. Furthermore, the selectivity of caprolactam begins to decrease as the catalyst dosage increases from 1g to 1.5g.

[0097] Test Example 3

[0098] This test example uses the SP(St-DVB)-10 catalyst prepared in Example 2 in the Beckmann liquid-phase rearrangement reaction to investigate the effect of different reaction temperatures on the product. Specifically, the method for preparing caprolactam using the Beckmann reaction includes the following steps: 2g of cyclohexanone oxime and 20ml of dimethyl sulfoxide are added to a 50ml high-pressure reactor, then 1g of SP(St-DVB)-10 catalyst is added. Nitrogen gas is purged three times to replace the original gas in the high-pressure reactor, and the reaction pressure in the high-pressure reactor is finally maintained at 0.5MPa. After reacting for 1h at different reaction temperatures, the reactor is cooled and the upper liquid phase reaction product is collected. After thorough centrifugation, the product composition is quantitatively analyzed by gas chromatography. The results are shown in Table 5.

[0099] Table 5. Reaction results of Test Example 3

[0100]

[0101] As shown in Table 5, the conversion rate of cyclohexanone oxime increases significantly with increasing reaction temperature, but the selectivity of caprolactam first increases and then decreases. At a reaction temperature of 130℃, a high conversion rate of cyclohexanone oxime and a high selectivity of caprolactam can be achieved.

[0102] Test Example 4

[0103] This test example uses the SP(St-DVB)-10 catalyst prepared in Example 2 in the Beckmann liquid-phase rearrangement reaction to investigate the effect of different reaction times on the product. Specifically, the method for preparing caprolactam using the Beckmann reaction includes the following steps: 2g of cyclohexanone oxime and 20ml of dimethyl sulfoxide are added to a 50ml high-pressure reactor, then 1g of SP(St-DVB)-10 catalyst is added. Nitrogen gas is purged three times to replace the original gas in the high-pressure reactor, and the reaction pressure in the high-pressure reactor is finally maintained at 0.5MPa. The reaction temperature is set to 130℃. After different reaction times, the reactor is cooled and the upper liquid phase reaction product is collected. After thorough centrifugation, the product composition is quantitatively analyzed by gas chromatography. The results are shown in Table 6.

[0104] Table 6. Reaction results of Test Example 4

[0105]

[0106] As shown in Table 6, the conversion rate of cyclohexanone oxime increases with increasing reaction time, but the selectivity of caprolactam decreases. In practical applications, the reaction time can be adjusted according to the actual situation to achieve a higher conversion rate of cyclohexanone oxime and a higher selectivity of caprolactam.

[0107] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0108] The above-described embodiments are merely illustrative of several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided by the present invention through logical analysis, reasoning, or limited experimentation are all within the protection scope of the appended claims. Therefore, the protection scope of this invention patent should be determined by the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A method for preparing a resin-type catalyst with a nanosphere structure, characterized in that, Includes the following steps: (1) Styrene monomer, divinylbenzene, stabilizer, initiator, pore-forming agent and deionized water are thoroughly mixed and stirred under constant temperature and inert gas atmosphere to obtain polystyrene-divinylbenzene nanosphere structure resin, wherein, calculated by the added volume, the amount of divinylbenzene added is 10%-30% of the amount of styrene added, the stabilizer includes polyvinylpyrrolidone, the initiator includes potassium persulfate, and the pore-forming agent includes at least one of toluene and n-heptane; (2) The polystyrene-divinylbenzene nanosphere structure resin is dried, and the dried polystyrene-divinylbenzene nanosphere structure resin is added to an organic solvent to make it fully swollen. Then, a sulfonating agent is added to incorporate sulfonic acid groups into the polystyrene-divinylbenzene nanosphere structure resin. The sulfonating agent includes at least one of concentrated sulfuric acid and chlorosulfonic acid, and the organic solvent includes at least one of n-hexane, dichloroethane, acetone, dimethylformamide and toluene. (3) The resin catalyst with nanosphere structure is obtained after filtration, washing and high-temperature drying.

2. A resin-type catalyst with a nanosphere structure prepared by the preparation method according to claim 1, characterized in that, It includes a polystyrene-divinylbenzene nanosphere structure resin and sulfonic acid groups, wherein the sulfonic acid groups are located on the benzene ring of the polystyrene-divinylbenzene nanosphere structure resin.

3. The resin-type catalyst with a nanosphere structure as described in claim 2, characterized in that, The resin-type catalyst has a mesoporous structure and a specific surface area of ​​9-13 m². 2 ·g -1 The pore volume is 0.01-0.02 cm. 3 ·g -1 .

4. The resin-type catalyst with a nanosphere structure as described in claim 2, characterized in that, The thermal decomposition temperature of the resin-type catalyst with nanosphere structure is greater than 200℃.

5. The application of the resin-type catalyst with nanosphere structure prepared by the preparation method according to claim 1 in the Beckmann liquid-phase rearrangement reaction.

6. The application of the resin-type catalyst with a nanosphere structure prepared by the method according to claim 1 in the preparation of caprolactam, characterized in that, Includes the following steps: Using cyclohexanone oxime as the reactant and dimethyl sulfoxide as the solvent, a Beckmann reaction was carried out under the catalysis of a resin-type catalyst with a nanosphere structure to obtain caprolactam.

7. The application as described in claim 6, characterized in that, The reaction temperature is 130-150℃; the amount of the resin-type catalyst with nanosphere structure added is 37.5%-75% of the cyclohexanone oxime by mass percentage.

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