CN115957811A - A kind of in-situ regeneration method of liquid phase Beckmann rearrangement reaction catalyst - Google Patents

Abstract

The invention provides an in-situ regeneration method of a liquid phase Beckmann rearrangement catalyst, wherein an inactivated catalyst is a molecular sieve supported catalyst and comes from a liquid phase Beckmann rearrangement reaction, and the regeneration method comprises the following steps: (1) introducing a cleaning solution A into a reaction tube filled with a catalyst; (2) introducing the cleaning liquid B into a reaction tube filled with a catalyst; (3) Heating a reaction tube filled with a catalyst, and introducing gas; and (4) introducing the regenerated liquid into a reaction tube filled with the catalyst. According to the in-situ regeneration method of the liquid-phase Beckmann rearrangement catalyst, the catalyst regeneration scheme provided by the method can completely recover the activity of the catalyst, has the advantages of obvious method effect, no need of unloading, low cost, small pollution and the like, and is suitable for catalyst treatment in caprolactam industrial production.

Description

In-situ regeneration method for liquid phase Beckmann rearrangement reaction catalyst

Technical Field

The invention belongs to the technical field of chemical synthesis, and in particular relates to an in-situ regeneration method for a liquid-phase Beckmann rearrangement reaction catalyst.

Background Art

Caprolactam is an important organic chemical raw material. Due to its special structure, it is mainly used as a monomer for polymers and is polymerized to produce polyamide 6 (PA6) slices. Caprolactam materials can be used to produce nylon plastics, cotton fibers, artificial leather and other related products. At the same time, it has a very obvious application effect in various medical fields and can be used to produce antiplatelet and other related drugs. PA6 slices of different brands have different performances and their application fields are also different. The processed PA6 is widely used in textiles, packaging, automobiles, electronics, machinery and other fields.

The main raw material routes for the production of caprolactam in the world are benzene, phenol and toluene. Among the three raw materials, the toluene route has the highest production capacity and is the world's main method for producing caprolactam. Represented by the technology of DSM Company of the Netherlands, cyclohexanone is prepared to synthesize cyclohexanone oxime, and caprolactam is obtained through Beckmann rearrangement. In recent years, my country's caprolactam production technology has made great progress, and domestic production capacity has been greatly expanded.

The change in my country's caprolactam production capacity has shown a steady growth trend, from 2250kt/a in 2015 to 4090kt/a in 2019, with a growth rate of 81.8%, and an average annual growth rate of 16.11%, far exceeding the global annual growth average. Domestic caprolactam production enterprises are mainly distributed in the eastern coastal areas, among which Fujian Shenyuan New Materials Co., Ltd., Nanjing Fubont Oriental Chemical Co., Ltd., Haili Chemical Co., Ltd., and Zhejiang Baling Hengyi Caprolactam Co., Ltd. have a production capacity of 400kt/a. Judging from the disclosed capacity expansion plans, the caprolactam industry will usher in a new round of growth from 2020 to 2025, including the 40kt/a capacity expansion project of Lanhua Technology Venture Co., Ltd., the 200kt/a capacity expansion project of Fujian Shenyuan New Materials Co., Ltd., the 200kt/a capacity expansion project of Pingmei Shenma Group, the 200kt/a new construction project of Inner Mongolia Qinghua Group Co., Ltd., the 200kt/a capacity expansion project of Fujian Yongrong Group, and the 600kt/a relocation project of Sinopec Baling Petrochemical Company. It is expected that by the end of 2025, the domestic caprolactam production capacity will exceed 5200kt/a, and market competition will further intensify.

The Beckmann rearrangement reaction is an acid-catalyzed rearrangement reaction in which the reactant oxime is rearranged to an amide under the catalytic action of the acid. There are currently a variety of Beckmann rearrangement catalysts, including inorganic acids, organic acids, acidic molecular sieves, ionic liquids, etc. People have conducted detailed research on these catalyst schemes.

Gas phase rearrangement is a process in which caprolactam is vaporized and then rearranged on a catalyst such as a molecular sieve. Compared with the existing liquid phase rearrangement, this technology does not require the use of ammonia, greatly saving the production cost of caprolactam. It is an important solution for the development of caprolactam rearrangement technology. Molecular sieve catalysts such as ZSM-5 and S-1 are the catalysts that have been studied more in the Beckmann rearrangement reaction.

Takahashi et al. studied the deactivation behavior of HZSM-5 molecular sieves with different silicon-aluminum ratios in the gas-phase Beckmann rearrangement reaction. The study found that when the number of strong acid centers is too large, the conversion rate is very high, but the selectivity is very low, only reaching 46%; when the number is too small, the conversion rate of cyclohexanone oxime and the selectivity of caprolactam are both very low. In addition, the fewer the number of strong acid centers, the smaller the pore size, and the slower the catalyst deactivation. Ichihashi et al. investigated the effect of S-1 molecular sieve on the activity of gas-phase Beckmann rearrangement reaction. It was found that the conversion rate and selectivity reached 100% and 80% respectively. Using methanol as a solvent, the selectivity of caprolactam can reach more than 95%. The author believes that the terminal silanol modified by methanol plays a very important role in improving the selectivity of caprolactam. It can be seen that the terminal hydroxyl group in the molecular sieve is not conducive to the Beckmann rearrangement reaction, but the structure of the silanol nest in the molecular sieve has a significant promoting effect on the gas-phase Beckmann rearrangement reaction and is the active center of the reaction.

Sinopec has made long-term exploration in the gas phase rearrangement of caprolactam and has made some progress. They use S-1 and TS-1 molecular sieves as catalysts. After years of technical iterations, the evaluation results of the Beckmann rearrangement are now 99.9% conversion rate and 96.5% selectivity, which are higher than the technical indicators disclosed by Sumitomo of Japan. The technology was pilot-tested in 2009 and passed the technical appraisal in 2010. Compared with the sulfuric acid method, the biggest advantage of gas phase rearrangement is that the product is easy to dissociate, no ammonia is required, no ammonium sulfate is produced as a by-product, and the atomic economy is high. However, this method has the disadvantages of severe reaction coking, low caprolactam yield, and short catalyst life.

Compared with the gas-phase Beckmann rearrangement reaction, the liquid-phase Beckmann rearrangement reaction has the advantages of mild reaction conditions and high caprolactam yield, but its difficulty lies in the development of an efficient catalyst with a long life.

In the industrial production of caprolactam, sulfuric acid or oleum is mostly used as a catalyst. Caprolactam is produced by the Beckmann rearrangement reaction of cyclohexanone oxime in the presence of sulfuric acid or oleum. The process generally adopts the method of material external circulation heat transfer, that is, oleum is added to the system from the inlet of the circulation pump in the rearrangement reactor and mixed with the rearrangement liquid, and the heat is removed from the reaction system through the circulation pipeline heat exchanger. The circulating liquid with reduced temperature enters the mixer and quickly mixes with the added cyclohexanone oxime to react to form the rearrangement liquid. This process is mature and simple, so it is basically used in industry to produce caprolactam.

Ionic liquids can be used as catalysts for the liquid-phase Beckmann rearrangement reaction. Ionic liquids refer to compounds that are completely composed of anions and cations and are liquid at room temperature or near room temperature. Ionic liquids have the following advantages: high-density reactivity, low volatility, low vapor pressure, high chemical properties, thermal stability, strong solubility and good catalytic activity, as well as adjustable structure, strong design, non-flammable and non-toxic. At present, dialkyl-substituted imidazole salts are the most widely used because they are easy to synthesize, have good physical properties and stable chemical properties. The ionic liquid method generally first rearranges in an ionic liquid/organic solvent, then extracts caprolactam with an organic solvent, and then separates caprolactam from the catalyst by solvent extraction. The ionic liquid, catalyst and organic solvent can be recycled. Despite the above advantages, the catalysts used under ionic liquid conditions, such as V, P, etc., are generally toxic. In addition, there are problems with the stability of ionic liquids and product separation, which are still far from practical application.

Ion exchange resin is a polymer compound with functional groups (active groups for exchanging ions), a network structure, and insolubility. Generally, the ion exchange resin with catalytic activity for the Beckmann rearrangement reaction of cyclohexanone oxime is a strong acid ion exchange resin with a sulfonic acid group. This catalyst has the advantages of being environmentally friendly, highly efficient, recyclable, and not using precious metals, but it also has the disadvantages of high cost and difficulty in regeneration after deactivation.

Solid acid catalysts use solid strong acids as functional groups and perform rearrangement reactions in the liquid phase. Compared with sulfuric acid, solid acid catalysts have the advantage of not producing ammonium sulfate byproducts. Patent ZL201811612796.0 discloses a method for preparing a molecular sieve-supported dual-active component solid acid catalyst. Using this catalyst, cyclohexanone oxime can be efficiently catalyzed to produce caprolactam, with high catalytic efficiency, high caprolactam yield, and no ammonium sulfate byproduct. The life of the catalyst is more than 4000 hours. Its deactivation mechanism is not only the coverage of carbon deposits, but is caused by multiple factors.

In order to reduce the production cost of caprolactam, the present invention provides a method for in-situ regeneration of the catalyst, which does not require unloading of the deactivated catalyst and can restore the activity of the catalyst only through multiple liquid phase treatments. The activated catalyst can fully restore its original catalytic performance. The method has the advantages of simple operation, simple method and equipment, mild operating conditions, and low cost, and is suitable for continuous industrial production of caprolactam.

Summary of the invention

In view of this, the present invention aims to propose an in-situ regeneration method for a liquid-phase Beckmann rearrangement reaction catalyst, and provides an in-situ regeneration method for a liquid-phase Beckmann rearrangement reaction catalyst. The present invention uses three solutions to treat the deactivated catalyst in sequence, first using a weak alkaline solution to open up the molecular sieve catalyst pores and remove attached oligomers; then using an acidic solution to remove amide substances attached to the active groups of the catalyst and clean the surface of the metal oxide; finally, using a strong acid solution to replenish the strong acid groups detached from the catalyst.

To achieve the above object, the technical solution of the present invention is achieved as follows:

The deactivated catalyst is a molecular sieve supported catalyst from a liquid phase Beckmann rearrangement reaction, and the regeneration method thereof comprises the following steps: S1 emptying the reactants in a tubular reactor containing a Beckmann rearrangement reaction catalyst;

S2 prepares cleaning solution A and uses the cleaning solution A to clean the reaction tube;

S3: hot air is introduced into the reaction tube obtained in step S2 to dry it;

S4 prepares a cleaning solution B and uses the cleaning solution B to clean the reaction tube;

S5: passing hot air into the reaction tube obtained in step S4 to dry it;

S6: Prepare activation solution C and use the activation solution C to clean the reaction tube;

S7: hot air is introduced into the reaction tube obtained in step S6 to dry it.

In the step S1, the Beckmann rearrangement reaction catalyst is loaded into a tubular reactor, and the loaded catalyst is a molded granular catalyst, preferably, the particle size of the particles is 6-10 mm.

Furthermore, in step S2, the cleaning solution A is a weakly alkaline organic solution; the solvent is one or two or more of methanol, ethanol, isopropanol, tert-butanol, ethylene glycol, glycerol, acetonitrile, benzonitrile, dichloromethane, chloroform, 1,1,2,2-tetrachloroethane, carbon tetrachloride, methyl formate, methyl acetate, and ethyl acetate;

The alkaline component is one or two or more of ammonia, sodium hydroxide, potassium hydroxide, ethylamine, ethylenediamine and triethylamine. The concentration of the alkaline component is 1-10%, preferably 2-5%.

Furthermore, in step S2, the weight ratio of cleaning solution A to the deactivated catalyst in step S1 is 2-100, preferably 10-20; the cleaning time of the reaction tube with cleaning solution A in S2 is 0.5-10h, preferably 2-5h, and the cleaning temperature is 20-80°C, preferably 40-50°C.

Furthermore, in step S3, the drying temperature is 50-200° C., preferably 80-120° C., and the drying time is 2-4 hours.

In step S4, the cleaning solution B is a strongly acidic aqueous solution, and the solvent is one or two or more of methanol, ethanol, isopropanol, tert-butanol, ethylene glycol, glycerol, acetonitrile, benzonitrile, dichloromethane, chloroform, 1,1,2,2-tetrachloroethane, carbon tetrachloride, methyl formate, methyl acetate, and ethyl acetate;

The acidic component is one or two or more of formic acid, acetic acid, trichloroacetic acid, sulfuric acid, picric acid, methanesulfonic acid, benzenesulfonic acid, toluenesulfonic acid and trifluorobenzenesulfonic acid. The concentration of the acidic component is 0.2-15%, preferably 1-5%.

Furthermore, in step S4, the weight ratio of the cleaning liquid B to the deactivated catalyst in step S1 is 5-200, preferably 20-50;

The cleaning time of the test tube with cleaning solution B is 10-50 hours, preferably 10-20 hours, and the cleaning temperature is 50-150°C, preferably 80-120°C.

Furthermore, in step S5, the drying temperature is 50-200°C, preferably 80-120°C, and the drying time is 2-4h;

In step S6, the activation solution C is an aqueous solution of a strong acid, wherein the acid is one or two or more of trichloroacetic acid, methanesulfonic acid, aminosulfonic acid, mellitic acid, picric acid, benzenesulfonic acid, toluenesulfonic acid, and trifluorobenzenesulfonic acid, and the concentration of the activation solution C is 0.1-20%, preferably 5-10%.

In step S6, the weight ratio of the activation solution C to the deactivated catalyst in step S1 is 1-10, preferably 2-4; the activation time is 10-50h, preferably 10-20h, and the activation temperature is 30-100°C, preferably 50-70°C.

In step S7, the drying temperature is 80-200° C., preferably 100-120° C., and the drying time is 8-10 hours.

Compared with the prior art, the in-situ regeneration method of a liquid-phase Beckmann rearrangement reaction catalyst described in the present invention has the following beneficial effects:

1. The regeneration method for the liquid-phase Beckmann rearrangement reaction catalyst described in the present method can be regenerated in situ, without the need to unload the catalyst loaded in the reaction tube, and the operation labor is small.

2. The catalyst regeneration method for the liquid-phase Beckmann rearrangement reaction described in the present invention can completely restore the activity and service life of the catalyst.

3. The method for regenerating the catalyst for the liquid-phase Beckmann rearrangement reaction described in the present invention has simple raw materials, low price, and is suitable for industrial production.

DETAILED DESCRIPTION

It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

The present invention will be described in detail below with reference to examples.

Example 1

Cyclohexanone oxime was dissolved in acetonitrile to prepare a 25% cyclohexanone oxime acetonitrile solution, the catalyst was placed in a fixed bed reactor, the fixed bed reactor was heated to 110°C, and the cyclohexanone oxime solution was passed through the fixed bed at a reaction space velocity of 1h ^-1 . The obtained cyclohexanone oxime conversion rate was 99.98%, the caprolactam selectivity was 99.87%, and after 4105h of reaction, the catalyst was deactivated and the cyclohexanone oxime conversion rate was 95.00%.

Example 2

The deactivated liquid phase Beckmann rearrangement reaction catalyst is from Example 1.

The reactants in the fixed bed were emptied. The fixed bed was filled with 10 kg of catalyst, which was in granular form with a particle diameter of 6 mm.

Prepare a total of 100 kg of cleaning liquid A, which is a methanol solution of ammonia with a concentration of 5%. Heat the fixed bed reactor to 50°C, and slowly pass the cleaning liquid A into the fixed bed reactor for cleaning, and the cleaning time is 5 hours. After cleaning, pass hot air at 100°C into the fixed bed reactor for drying, and the drying time is 2 hours.

A total of 300 kg of cleaning liquid B was prepared. The cleaning liquid B was composed of a methanol solution of acetic acid with a concentration of 5%. The fixed bed reactor was heated to 100°C and the cleaning liquid B was slowly introduced into the fixed bed reactor for cleaning. The cleaning time was 20 hours. After the cleaning was completed, hot air at 100°C was introduced into the fixed bed reactor for drying. The drying time was 4 hours.

A total of 80 kg of activation solution C was prepared. The component of activation solution C was an aqueous solution of aminosulfonic acid, and the concentration of aminosulfonic acid was 10%. The fixed bed reactor was heated to 50°C, and the activation solution C was slowly introduced into the fixed bed reactor for activation. The activation time was 18 hours. After the activation was completed, hot air at 120°C was introduced into the fixed bed reactor for drying. The drying time was 10 hours.

Example 3

The deactivated liquid phase Beckmann rearrangement reaction catalyst is from Example 1.

The reactants in the fixed bed were emptied. The fixed bed was filled with 10 kg of catalyst, which was in granular form with a particle diameter of 6 mm.

Prepare a total of 150 kg of cleaning liquid A, which is an acetonitrile solution of ammonia with a concentration of 5%. Heat the fixed bed reactor to 80°C, and slowly pass the cleaning liquid A into the fixed bed reactor for cleaning, and the cleaning time is 4 hours. After cleaning, pass hot air at 100°C into the fixed bed reactor for drying, and the drying time is 2 hours.

Prepare a total of 200 kg of cleaning liquid B, which is an ethanol solution of sulfuric acid with a concentration of 2%. Heat the fixed bed reactor to 100°C, and slowly pass the cleaning liquid B into the fixed bed reactor for cleaning, and the cleaning time is 15 hours. After cleaning, pass hot air at 100°C into the fixed bed reactor for drying, and the drying time is 2 hours.

A total of 40 kg of activation solution C was prepared. The components of activation solution C were an aqueous solution of sulfuric acid and a concentration of 10% aminosulfonic acid. The fixed bed reactor was heated to 50°C and the activation solution C was slowly introduced into the fixed bed reactor for activation. The activation time was 15 hours. After activation, hot air at 120°C was introduced into the fixed bed reactor for drying. The drying time was 10 hours.

Example 4

The deactivated liquid phase Beckmann rearrangement reaction catalyst is from Example 1.

The reactants in the fixed bed were emptied. The fixed bed was filled with 10 kg of catalyst, which was in granular form with a particle diameter of 6 mm.

Prepare a total of 150 kg of cleaning liquid A, which is composed of ethylene glycol solution of sodium hydroxide, and the concentration of sodium hydroxide is 5%. Heat the fixed bed reactor to 80°C, and slowly pass the cleaning liquid A into the fixed bed reactor for cleaning, and the cleaning time is 2 hours. After cleaning, pass hot air at 120°C into the fixed bed reactor for drying, and the drying time is 4 hours.

Prepare a total of 200 kg of cleaning liquid B, which is a benzenesulfonic acid ethylene glycol solution with a benzenesulfonic acid concentration of 5%. Heat the fixed bed reactor to 80°C, and slowly pass the cleaning liquid B into the fixed bed reactor for cleaning, and the cleaning time is 20 hours. After cleaning, pass hot air at 100°C into the fixed bed reactor for drying, and the drying time is 4 hours.

A total of 80 kg of activation liquid C was prepared. The component of activation liquid C was an aqueous solution of mellitic acid, and the concentration of mellitic acid was 5%. The fixed bed reactor was heated to 70° C., and the activation liquid C was slowly introduced into the fixed bed reactor for activation. The activation time was 10 hours. After the activation was completed, hot air at 120° C. was introduced into the fixed bed reactor for drying. The drying time was 8 hours.

Example 5

The deactivated liquid phase Beckmann rearrangement reaction catalyst is from Example 1.

The reactants in the fixed bed were emptied. The fixed bed was filled with 10 kg of catalyst, which was in granular form with a particle diameter of 6 mm.

Prepare a total of 120 kg of cleaning liquid A, which is a 1,1,2,2-tetrachloroethane solution of potassium hydroxide, with a potassium hydroxide concentration of 2%. Heat the fixed bed reactor to 50°C, and slowly pass the cleaning liquid A into the fixed bed reactor for cleaning, and the cleaning time is 4 hours. After cleaning, pass 120°C hot air into the fixed bed reactor for drying, and the drying time is 4 hours.

A total of 150 kg of cleaning liquid B was prepared. The cleaning liquid B was composed of a tert-butyl alcohol solution of toluenesulfonic acid, and the concentration of toluenesulfonic acid was 5%. The fixed bed reactor was heated to 100°C, and the cleaning liquid B was slowly introduced into the fixed bed reactor for cleaning. The cleaning time was 16 hours. After the cleaning was completed, hot air at 120°C was introduced into the fixed bed reactor for drying. The drying time was 4 hours.

A total of 80 kg of activation solution C was prepared. The component of activation solution C was an aqueous solution of trifluorobenzenesulfonic acid, and the concentration of trifluorobenzenesulfonic acid was 5%. The fixed bed reactor was heated to 50° C., and the activation solution C was slowly introduced into the fixed bed reactor for activation. The activation time was 12 hours. After the activation was completed, hot air at 120° C. was introduced into the fixed bed reactor for drying. The drying time was 10 hours.

Example 6

The deactivated liquid phase Beckmann rearrangement reaction catalyst is from Example 1.

The reactants in the fixed bed were emptied. The fixed bed was filled with 10 kg of catalyst, which was in granular form with a particle diameter of 6 mm.

Prepare a total of 120 kg of cleaning liquid A, which is an ethyl acetate solution of ethylenediamine with a concentration of 2.5%. Heat the fixed bed reactor to 50°C, and slowly pass the cleaning liquid A into the fixed bed reactor for cleaning, and the cleaning time is 5 hours. After cleaning, pass hot air at 100°C into the fixed bed reactor for drying, and the drying time is 4 hours.

A total of 200 kg of cleaning liquid B was prepared. The cleaning liquid B was composed of an ethyl acetate solution of trichloroacetic acid, and the concentration of trichloroacetic acid was 5%. The fixed bed reactor was heated to 140°C, and the cleaning liquid B was slowly introduced into the fixed bed reactor for cleaning. The cleaning time was 20 hours. After the cleaning was completed, hot air at 120°C was introduced into the fixed bed reactor for drying. The drying time was 4 hours.

A total of 60 kg of activation solution C was prepared. The component of activation solution C was an aqueous solution of picric acid with a concentration of 10%. The fixed bed reactor was heated to 70°C, and the activation solution C was slowly introduced into the fixed bed reactor for activation. The activation time was 20 hours. After the activation was completed, hot air at 120°C was introduced into the fixed bed reactor for drying. The drying time was 10 hours.

Example 7

Dissolve cyclohexanone oxime in acetonitrile to prepare a 25% cyclohexanone oxime acetonitrile solution. Use the catalyst obtained in Example 2-6. Heat the fixed bed reactor to 110°C, pass the cyclohexanone oxime solution through the fixed bed, and perform reaction evaluation at a reaction space velocity of 1h ^-1 . When the cyclohexanone oxime conversion rate is lower than 95%, the catalyst is considered to be deactivated. The evaluation results are shown in Table 1.

Comparative Example 1

The deactivated liquid phase Beckmann rearrangement reaction catalyst is from Example 1.

The reactants in the fixed bed were emptied. The fixed bed was filled with 10 kg of catalyst, which was in granular form with a particle diameter of 6 mm.

A total of 120 kg of cleaning liquid A was prepared, and the component of cleaning liquid A was ethanol. The fixed bed reactor was heated to 50°C, and the cleaning liquid A was slowly introduced into the fixed bed reactor for cleaning, and the cleaning time was 5 hours. After the cleaning was completed, hot air at 100°C was introduced into the fixed bed reactor for drying, and the drying time was 4 hours.

Prepare a total of 200 kg of cleaning liquid B, the composition of which is 1,1,2,2-tetrachloroethane. Heat the fixed bed reactor to 140°C, and slowly pass the cleaning liquid B into the fixed bed reactor for cleaning, and the cleaning time is 20 hours. After cleaning, pass hot air at 120°C into the fixed bed reactor for drying, and the drying time is 4 hours.

A total of 60 kg of activation solution C was prepared. The component of activation solution C was an aqueous solution of benzenesulfonic acid, and the concentration of benzenesulfonic acid was 10%. The fixed bed reactor was heated to 80°C, and the activation solution C was slowly introduced into the fixed bed reactor for activation. The activation time was 20 hours. After the activation was completed, hot air at 120°C was introduced into the fixed bed reactor for drying. The drying time was 10 hours.

Comparative Example 2

The deactivated liquid phase Beckmann rearrangement reaction catalyst is from Example 1.

The reactants in the fixed bed were emptied. The fixed bed was filled with 10 kg of catalyst, which was in granular form with a particle diameter of 6 mm.

A total of 100 kg of activation solution C was prepared. The component of activation solution C was an aqueous solution of benzenesulfonic acid with a concentration of 10%. The fixed bed reactor was heated to 80°C, and the activation solution C was slowly introduced into the fixed bed reactor for activation. The activation time was 20 hours. After the activation was completed, hot air at 120°C was introduced into the fixed bed reactor for drying. The drying time was 10 hours.

Comparative Example 3

The deactivated liquid phase Beckmann rearrangement reaction catalyst is from Example 1.

The reactants in the fixed bed were emptied. The fixed bed was filled with 10 kg of catalyst, which was in granular form with a particle diameter of 6 mm.

A total of 200 kg of cleaning liquid B was prepared. The cleaning liquid B was composed of an ethanol solution of acetic acid with a concentration of 5%. The fixed bed reactor was heated to 80°C and the cleaning liquid B was slowly introduced into the fixed bed reactor for cleaning. The cleaning time was 20 hours. After the cleaning was completed, hot air at 120°C was introduced into the fixed bed reactor for drying. The drying time was 4 hours.

A total of 100 kg of activation solution C was prepared. The component of activation solution C was an aqueous solution of benzenesulfonic acid with a concentration of 10%. The fixed bed reactor was heated to 80°C, and the activation solution C was slowly introduced into the fixed bed reactor for activation. The activation time was 20 hours. After the activation was completed, hot air at 120°C was introduced into the fixed bed reactor for drying. The drying time was 10 hours.

It can be seen from Examples 2-6 and Comparative Examples 1-3 that the life of the catalyst after regeneration is almost the same as that of the original catalyst, and the cyclohexanone oxime conversion rate and caprolactam selectivity can also be guaranteed. The method for regenerating the catalyst for the liquid-phase Beckmann rearrangement reaction of the present invention can completely restore the activity and service life of the catalyst. The method for regenerating the catalyst for the liquid-phase Beckmann rearrangement reaction of the present invention has simple raw materials, low price, and is suitable for industrial production.

Table 1

Claims (10)

1. An in-situ regeneration method for a liquid-phase Beckmann rearrangement reaction catalyst, characterized in that: the deactivated catalyst is a molecular sieve-supported catalyst from a liquid-phase Beckmann rearrangement reaction, and the regeneration method comprises the following steps: S1 emptying the reactants in a tubular reactor containing the Beckmann rearrangement reaction catalyst; S2 preparing a cleaning liquid A and using the cleaning liquid A to clean the reaction tube; S3: hot air is introduced into the reaction tube obtained in step S2 to dry it; S4 prepares a cleaning solution B and uses the cleaning solution B to clean the reaction tube; S5: hot air is introduced into the reaction tube obtained in step S4 to dry it; S6: Prepare activation solution C and use the activation solution C to clean the reaction tube; S7: hot air is introduced into the reaction tube obtained in step S6 to dry it. 2. The in-situ regeneration method of a liquid-phase Beckmann rearrangement reaction catalyst according to claim 1, characterized in that: in the step S1, the Beckmann rearrangement reaction catalyst is loaded in a tubular reactor, and the loaded catalyst is a molded granular catalyst, preferably, the particle size is 6-10 mm. 3. The in-situ regeneration method of a liquid-phase Beckmann rearrangement reaction catalyst according to claim 1, characterized in that: in the step S2, the cleaning liquid A is a weakly alkaline organic solution; The solvent is one or two or more of methanol, ethanol, isopropanol, tert-butanol, ethylene glycol, glycerol, acetonitrile, benzonitrile, dichloromethane, chloroform, 1,1,2,2-tetrachloroethane, carbon tetrachloride, methyl formate, methyl acetate, and ethyl acetate; The alkaline component is one or two or more of ammonia, sodium hydroxide, potassium hydroxide, ethylamine, ethylenediamine and triethylamine. The concentration of the alkaline component is 1-10%, preferably 2-5%. 4. The in-situ regeneration method of a liquid-phase Beckmann rearrangement reaction catalyst according to claim 1, characterized in that: in the step S2, the weight ratio of the cleaning liquid A to the deactivated catalyst in the step S1 is 2-100, preferably 10-20; The cleaning time of the reaction tube with the cleaning solution A in S2 is 0.5-10 hours, preferably 2-5 hours, and the cleaning temperature is 20-80°C, preferably 40-50°C. 5. The in-situ regeneration method of a liquid-phase Beckmann rearrangement reaction catalyst according to claim 1, characterized in that: in the step S3, the drying temperature is 50-200°C, preferably 80-120°C, and the drying time is 2-4h. 6. The in-situ regeneration method of a liquid-phase Beckmann rearrangement reaction catalyst according to claim 1, characterized in that: in the step S4, the cleaning liquid B is a strongly acidic aqueous solution, and the solvent is one or two or more of methanol, ethanol, isopropanol, tert-butanol, ethylene glycol, glycerol, acetonitrile, benzonitrile, dichloromethane, chloroform, 1,1,2,2-tetrachloroethane, carbon tetrachloride, methyl formate, methyl acetate, and ethyl acetate; The acidic component is one or two or more of formic acid, acetic acid, trichloroacetic acid, sulfuric acid, picric acid, methanesulfonic acid, benzenesulfonic acid, toluenesulfonic acid and trifluorobenzenesulfonic acid. The concentration of the acidic component is 0.2-15%, preferably 1-5%. 7. The in-situ regeneration method of a liquid-phase Beckmann rearrangement reaction catalyst according to claim 1, characterized in that: in the step S4, the weight ratio of the cleaning liquid B to the deactivated catalyst in the step S1 is 5-200, preferably 20-50; The cleaning time of the test tube with cleaning solution B is 10-50 hours, preferably 10-20 hours, and the cleaning temperature is 50-150°C, preferably 80-120°C. 8. The in-situ regeneration method of a liquid-phase Beckmann rearrangement reaction catalyst according to claim 1, characterized in that: in the step S5, the drying temperature is 50-200°C, preferably 80-120°C, and the drying time is 2-4h; In step S6, the activation solution C is an aqueous solution of a strong acid, wherein the acid is one or two or more of trichloroacetic acid, methanesulfonic acid, aminosulfonic acid, mellitic acid, picric acid, benzenesulfonic acid, toluenesulfonic acid, and trifluorobenzenesulfonic acid, and the concentration of the activation solution C is 0.1-20%, preferably 5-10%. 9. The in-situ regeneration method of a liquid-phase Beckmann rearrangement reaction catalyst according to claim 1, characterized in that: in the step S6, the weight ratio of the activation solution C to the deactivated catalyst in the step S1 is 1-10, preferably 2-4; The activation time is 10-50h, preferably 10-20h, and the activation temperature is 30-100°C, preferably 50-70°C. 10. The in-situ regeneration method of a liquid-phase Beckmann rearrangement reaction catalyst according to claim 1, characterized in that: in the step S7, the drying temperature is 80-200°C, preferably 100-120°C, and the drying time is 8-10h.