Method for improving stability of cyclohexanone-oxime gas-phase Beckmann rearrangement catalyst and application

Abstract

The invention provides a process for improving the stability of a cyclohexanone-oxime gas-phase Beckmann rearrangement catalyst, which comprises the following steps: placing the catalyst in a fixed bed reactor, and introducing a solution composed of cyclohexanone-oxime and a mixed solvent to carry out a cyclohexanone-oxime gas-phase Beckmann rearrangement reaction, wherein the mixed solvent is formed by mixing at least two of a nitrile solvent, C1-C6 alcohol and water; the catalyst is used for a cyclohexanone-oxime gas phase Beckmann rearrangement reaction. Compared with a single solvent system, the method provided by the invention adopts the mixed solvent, so that the stability of the cyclohexanone-oxime gas-phase Beckmann rearrangement catalyst can be remarkably improved. Raw materials and a mixed solvent of the fixed bed reaction device can be independently fed or mixed to be fed, two reactors connected in parallel are adopted, and when carbon deposition of a catalyst of one reactor is inactivated, the other reactor is switched to continue to react; the deactivated catalyst is switched to a mixed solvent for feeding and is subjected to in-situ treatment, so that the performance regeneration of the catalyst can be realized.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a method for improving the stability of cyclohexanone oxime gas-phase Beckmann rearrangement catalyst, an in-situ catalyst regeneration process, and a continuous production process flow, applicable to industrial production scenarios of cyclohexanone oxime gas-phase Beckmann rearrangement to prepare caprolactam and caprolactam amination to 6-aminohexanonitrile. Background Technology

[0002] The cyclohexanone oxime Beckmann rearrangement is a typical acid-catalyzed process. Traditional liquid-phase rearrangements often use concentrated sulfuric acid or fuming sulfuric acid as catalysts, which not only causes severe corrosion to reaction equipment but also poses a serious threat to the environment. In contrast, gas-phase rearrangements use solid acid catalysts, which not only have higher atom utilization and reduce resource waste but also avoid the pollution problems associated with liquid catalysts. Under gas-phase reaction conditions, the product and catalyst are easier to separate, significantly reducing subsequent processing costs and representing a new process route that aligns with the principles of green development.

[0003] Solid acid catalysts commonly used in the gas-phase Beckmann rearrangement of cyclohexanone oxime can be broadly classified into two categories: oxides and molecular sieves. Catalyst stability directly affects reaction efficiency, product selectivity, production costs, and process sustainability. Specifically, catalyst stability impacts the reaction in several ways: First, it affects reaction efficiency: Stable catalysts (such as modified ZSM-5 molecular sieves) can maintain the number and strength of active sites (such as acidic sites) for extended periods, ensuring the continuous and efficient conversion of cyclohexanone oxime to caprolactam. Stable catalysts can maintain high conversion rates (typically >95%), reducing downtime due to frequent catalyst replacements. If catalyst stability decreases, deactivation due to carbon deposition, framework dealuminization, or acid site loss leads to a decrease in reaction conversion, resulting in incomplete conversion of cyclohexanone oxime, increasing feedstock waste and subsequent separation costs. Secondly, the impact on product selectivity: Stable catalysts maintain a suitable distribution of acidic sites and pore structure, maximizing the promotion of the Beckmann rearrangement main reaction and reducing side reactions (such as the decomposition of cyclohexanone oxime into cyclohexanone, nitriles, or tar), which can maintain caprolactam selectivity above 90%. Conversely, decreased catalyst stability or deactivation leads to changes in acid site strength or pore structure, promoting an increase in side reactions. For example, carbon buildup clogging pores may cause cyclohexanone oxime to decompose at non-selective sites, resulting in decreased selectivity, increased byproducts, and reduced product quality. Thirdly, the impact on process economics: Highly stable catalysts have a long lifespan, reducing replacement frequency and lowering production costs. Stable catalysts can also operate under wider reaction conditions (such as high temperatures or water-containing atmospheres), simplifying process control; while low-stability catalysts require periodic regeneration or replacement due to frequent deactivation, increasing operating costs and downtime losses. Fourth, the impact on process sustainability: Stable catalysts reduce the generation of spent catalysts, meeting the requirements of green chemistry; gas-phase Beckmann rearrangement is already more environmentally friendly than traditional liquid-phase processes (concentrated sulfuric acid process), and catalyst stability further reduces the need for by-product and waste treatment. However, low-stability or deactivated catalysts may require frequent treatment due to carbon buildup or structural damage, increasing the waste treatment burden; if by-products increase, additional separation and waste treatment processes are required, increasing the environmental load. Fifth, the impact on reaction conditions and operational flexibility: Stable catalysts (such as high Si / Al ratio or phosphorus-modified ZSM-5) can operate for a long time at high temperatures (250~400 ℃), allowing for more flexible optimization of reaction conditions (such as increasing the temperature to improve the reaction rate); while low-stability catalysts are sensitive to high temperatures or moisture (such as skeleton dealumination), limiting the range of reaction conditions, requiring stricter control of temperature, pressure, or raw material purity, increasing operational difficulty. In the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime, carbon deposition is one of the important reasons for catalyst deactivation. This is mainly reflected in the degradation of catalyst performance caused by the covering of acidic sites on the surface of solid catalyst by carbon species. Catalyst stability and regeneration efficiency are key bottlenecks restricting industrialization.In existing technologies, catalyst deactivation due to carbon buildup often requires interrupting the reaction process or dismantling the reactor for regeneration, making true continuous production difficult. For example, Chinese patent CN1273971A provides a gas-phase Beckmann rearrangement method for cyclohexanone oxime using a fluidized bed process, where the deactivated catalyst is regenerated using oxygen-containing gas. However, this catalyst regeneration method suffers from insufficient raw material utilization due to the calcination process, thus reducing the economic efficiency of the process. Chinese patent CN102806103A proposes a process scheme using "parallel reactor + solvent regeneration + alkali regeneration," where the regeneration process requires first lowering the reactor temperature from the reaction temperature (approximately 330°C) to 100°C for solvent treatment, and then gradually raising the temperature to 450°C to complete the regeneration of alkali and mixed gas. However, this method has the following drawbacks: firstly, the multiple heating and cooling operations are complex, requiring precise control of the temperature gradient, increasing operational difficulty; secondly, frequent temperature fluctuations lead to a significant increase in reactor energy consumption; and thirdly, the regeneration process requires the introduction of an alkaline solution, increasing the complexity of the raw material system and subsequent separation costs. Therefore, it is evident that the study of the stability of cyclohexanone oxime gas-phase Beckmann rearrangement catalysts is of great significance, and in view of this, this patent application is hereby filed. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of poor stability in existing catalysts used for the gas-phase Beckmann rearrangement of cyclohexanone oxime.

[0005] To achieve the above-mentioned objectives, the solution of this invention is: A process for improving the stability of cyclohexanone oxime gas-phase Beckmann rearrangement catalysts includes the following steps: The cyclohexanone oxime gas-phase Beckmann rearrangement reaction is carried out by placing the catalyst in a fixed-bed reactor and then introducing a solution composed of cyclohexanone oxime and a mixed solvent; wherein the mixed solvent is composed of at least two of a nitrile solvent, a C1-C6 alcohol and water; and the catalyst is a catalyst for the cyclohexanone oxime gas-phase Beckmann rearrangement reaction.

[0006] Preferably, the C1-C6 alcohol solvent includes one of methanol, ethanol, propanol, isopropanol, butanol, or cyclohexanol.

[0007] Preferably, the nitrile solvent is composed of one or a mixture of acetonitrile or hexanonitrile.

[0008] Preferably, the catalyst is selected from one of aluminosilicate molecular sieves, pure silicon molecular sieves, silicon-phosphorus-aluminum molecular sieves, or titanium-silicon molecular sieves, or molecular sieves derived from these molecular sieves after acid-base modification.

[0009] Preferably, the conditions for the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime are as follows: using a 5-25 wt% cyclohexanone oxime-mixed solution as raw material, the reaction temperature is 320-400 °C, the reaction pressure is 0.1-2.0 MPa, and the mass hourly space velocity is set to 0.5-3.0 h⁻¹. -1 The process was carried out under the condition that the carrier nitrogen flow rate was 10~100 mL / min.

[0010] Preferably, when the mixed solvent is composed of a nitrile solvent and water, the water content in the mixed solvent is 5-20 wt%; when the mixed solvent is composed of C1-C6 alcohol and water, the water content in the mixed solvent is 1-30 wt%; when the mixed solvent is composed of a nitrile solvent and C1-C6 alcohol solvent, the alcohol content in the mixed solvent is 1-10 wt%.

[0011] An in-situ regeneration process for a carbonized deactivated catalyst includes: placing the carbonized deactivated catalyst in a fixed-bed reactor, and then introducing a mixed solvent to treat it at a reaction temperature; wherein the mixed solvent is composed of at least two of a nitrile solvent, C1-C6 alcohol, and water.

[0012] An in-situ regeneration process for a carbon-deactivated catalyst is disclosed. The feedstock and mixed solvent of the fixed-bed reactor can be fed separately or in combination. The reactor is equipped with two reactors connected in parallel. When the catalyst in one reactor becomes carbon-deactivated, the reactor is switched to the other reactor to continue the reaction. The carbon-deactivated catalyst is switched to the mixed solvent feed and the deactivated catalyst is regenerated in situ at the reaction temperature for a regeneration time of 1 to 48 hours.

[0013] An in-situ regeneration process for carbon-deactivated catalysts is applicable to the regeneration of carbon-deactivated catalysts in the gas-phase Beckmann rearrangement of cyclohexanone oxime to caprolactam and the amination of caprolactam to 6-aminohexanonitrile.

[0014] The design principle of this invention is as follows: The process for improving the stability of cyclohexanone oxime gas-phase Beckmann rearrangement catalyst provided by this invention mainly involves using a mixed solvent composed of a specific ratio of ethanol-water or acetonitrile-water (water content 5-30 wt%) to carry out the cyclohexanone oxime gas-phase Beckmann rearrangement reaction. Specifically, the nitriles and alcohols in the mixed solvent are beneficial for dissolving the carbonized organic matter on the catalyst surface, and water vapor can restore the acidity of the catalyst surface at high temperatures. Using two parallel feed tanks allows for in-situ regeneration of the carbonized and deactivated catalyst without changing the reaction system temperature, reducing operational difficulty and improving production efficiency.

[0015] The beneficial effects of this invention are as follows: (1) The present invention provides a method to improve the stability of the gas-phase Beckmann rearrangement catalyst of cyclohexanone oxime by using a mixed solvent to react, which can effectively achieve a significant improvement in the stability of the catalyst.

[0016] (2) The process for improving the stability of cyclohexanone oxime gas-phase Beckmann rearrangement catalyst provided by the present invention has the advantages of simple operation, low cost, and suitability for industrial production.

[0017] (3) The process for improving the stability of the cyclohexanone oxime gas-phase Beckmann rearrangement catalyst provided by the present invention was applied to the reaction of cyclohexanone oxime gas-phase Beckmann rearrangement to caprolactam. The results showed that the single-pass conversion rate of cyclohexanone oxime could reach up to 100%, and the selectivity of caprolactam was greater than 99.0%.

[0018] (4) The regeneration process of the carbon-deactivated catalyst provided by the present invention is applicable to the regeneration process of carbon-deactivated catalyst in the reaction of cyclohexanone oxime gas phase Beckmann rearrangement to caprolactam or the reaction of caprolactam amination to 6-aminohexanonitrile. The regeneration operation is simple and can realize continuous production. Attached Figure Description

[0019] Figure 1 This is a thermogravimetric analysis (TGA) diagram of the catalyst.

[0020] Figure 2 This is a process flow diagram of a fixed-bed reactor that enables in-situ regeneration.

[0021] Explanation of reference numerals in the attached diagram: 1. Raw material feed heating vessel; 2. Raw material feed pump; 3. Raw material heat exchanger; 4. Raw material vaporizer. 5A / B, Parallel reactors 6, Regeneration solvent circulation pump 7, Solvent heater 8, Regeneration solvent tank. Detailed Implementation

[0022] The advantages of the present invention will be further described in detail below with reference to embodiments and comparative examples. It should also be understood that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. The specific mass, reaction time, temperature, process parameters, etc., in the examples are merely examples within a suitable range. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention.

[0023] Example 1 The steps to improve the stability of the cyclohexanone oxime gas-phase Beckmann reaction catalyst are as follows: Five g of commercially available H-Beta silica-alumina molecular sieve catalyst was placed in a fixed-bed reactor, and then a feed solution with a mass concentration of 25 wt% cyclohexanone oxime (the solvent of the feed solution was a 15% water content acetonitrile-water mixture) was introduced. The reaction was carried out at a temperature of 320 °C, a pressure of 0.1 MPa, and a mass hourly space velocity of 2.0 h⁻¹. -1 Cyclohexanone oxime gas-phase Beckmann reaction was carried out under the condition of nitrogen flow rate of 40 mL / min to obtain caprolactam. The catalyst was continuously evaluated for 100 h, and the catalyst performance results at 8 h and 100 h were used for comparison. The specific catalytic results are shown in Table 1.

[0024] Example 2 The treatment steps to improve the stability of the cyclohexanone oxime gas-phase Beckmann reaction catalyst are the same as in Example 1, except that the commercially available aluminosilicate molecular sieve H-Beta is replaced with the commercially available aluminosilicate molecular sieve ZSM-5, and the water content in the mixed solvent is adjusted to 10%; the remaining steps are the same as in Example 1, and the catalytic results are shown in Table 1.

[0025] Example 3 The treatment steps to improve the stability of the cyclohexanone oxime gas-phase Beckmann reaction catalyst are the same as in Example 1, except that the commercially available silica-alumina molecular sieve H-Beta is replaced with the commercially available all-silica molecular sieve S-1, and the mixed solvent is replaced with a methanol-water mixed solvent with a water content of 5%; the remaining steps are the same as in Example 1, and the catalytic results are shown in Table 1.

[0026] Example 4 The treatment steps to improve the stability of the cyclohexanone oxime gas-phase Beckmann reaction catalyst are the same as in Example 1, except that the commercially available silica-alumina molecular sieve H-Beta is replaced with the commercially available titanium-silicon molecular sieve TS-1, and the mixed solvent is replaced with a cyclohexanol-water mixed solvent with a water content of 8%; the remaining steps are the same as in Example 1, and the catalytic results are shown in Table 1.

[0027] Example 5 The steps for improving the stability of the cyclohexanone oxime gas-phase Beckmann reaction catalyst are the same as in Example 1, except that the commercially available silica-alumina molecular sieve H-Beta is replaced with the commercially available silica-phosphorus-alumina molecular sieve SAPO-11, and the mixed solvent is replaced with an ethanol-hexanonitrile mixed solvent with an ethanol content of 10%; the remaining steps are the same as in Example 1, and the catalytic results are shown in Table 1.

[0028] Example 6 The steps for improving the stability of the cyclohexanone oxime gas-phase Beckmann reaction catalyst are the same as in Example 1, except that the commercially available aluminosilicate molecular sieve H-Beta is replaced with the commercially available aluminosilicate molecular sieve Na-Beta, and the mixed solvent is replaced with a mixed solvent composed of acetonitrile-ethanol-water (5% ethanol and 5% water). The remaining steps are the same as in Example 1, and the catalytic results are shown in Table 1.

[0029] Comparative Example 1 The steps for improving the stability of the cyclohexanone oxime gas-phase Beckmann reaction catalyst are the same as in Example 1, except that the mixed solvent is replaced with pure acetonitrile solvent; the remaining steps are the same as in Example 1, and the catalytic results are shown in Table 1.

[0030] Comparative Example 2 The steps for improving the stability of the cyclohexanone oxime gas-phase Beckmann reaction catalyst are the same as in Example 1, except that the commercially available aluminosilicate molecular sieve H-Beta is replaced with the commercially available aluminosilicate molecular sieve ZSM-5, and the mixed solvent is replaced with pure ethanol solvent; the remaining steps are the same as in Example 1, and the catalytic results are shown in Table 1.

[0031] Comparative Example 3 The steps for improving the stability of the cyclohexanone oxime gas-phase Beckmann reaction catalyst are the same as in Example 1, except that the commercially available silica-alumina molecular sieve H-Beta is replaced with the commercially available all-silica molecular sieve S-1, and the mixed solvent is replaced with pure water. All other steps are the same as in Example 1. The catalytic results are shown in Table 1.

[0032] Table 1: Results of the gas-phase Beckmann rearrangement of cyclohexanone oxime

[0033] Example 7 The steps for testing the acid content on the catalyst surface are as follows: The surface acidity of the catalyst was determined by NH3-TPD characterization: First, 0.10 g of catalyst was weighed into a U-tube, and then... -1 He purging was performed, and the temperature was raised to 300 °C and held for 2 h to remove adsorbed water and impurities from the sample surface. The temperature was then lowered to 40 °C, and the solution was changed to 50 mL / min. -1 The catalyst was purged with 10% NH3 / He for 1.5 h to saturate the NH3 adsorption on the catalyst surface, and then the gas was changed to 50 mL / min. -1 He purging was performed to remove physically adsorbed NH3 from the sample surface. Once the baseline stabilized, data acquisition began. The temperature was set at 10 °C for [min]. -1 The temperature was raised to 800 °C and held for 10 min. Signals were acquired using a TCD and an external mass spectrometer detector. The peak areas of the TCD and mass spectrometer were calibrated by pure NH3 pulse injection, and the acid content on the catalyst surface was calculated.

[0034] The specific acid content values ​​of the catalyst used in Example 1 and the catalyst of Comparative Example 1 were tested according to the above steps and are shown in Table 2.

[0035] As can be seen from the results in Table 2, when the H-Beta silica-alumina molecular sieve catalyst undergoes a gas-phase Beckmann reaction of cyclohexanone oxime in a specific ratio of nitrile-water, alcohol-water, or nitrile-alcohol mixtures as solvents, the total acid content on the catalyst surface does not change significantly before and after the catalytic reaction. However, when a single pure solvent is used for the reaction, the total acid content on the catalyst surface decreases significantly. This further demonstrates the advantages of the treatment method provided by this invention.

[0036] Table 2: Catalyst Surface Acidity Data

[0037] Example 8 The test procedure for the degree of carbon deposition on the catalyst is as follows: The catalysts used before the reaction in Example 1 and Comparative Example 1 were selected and their stability was tested by thermogravimetric analysis (TGA). TGA is an analytical technique that studies the thermal stability, composition, and phase transition of a substance by measuring the change in sample mass with temperature. The degree of carbon deposition on the catalyst after the reaction was studied using a STA 449 F5 Jupiter simultaneous thermal analyzer: approximately 15 mg of catalyst sample was placed in a crucible and incubated at 5 °C for [time missing] min in air. -1 The temperature was raised to 900 °C, and mass change data were collected within the range of 30–900 °C. The results are as follows: Figure 1 As shown.

[0038] from Figure 1 As can be seen, the degree of carbon deposition of the molecular sieve catalyst after reaction using a mixed solvent (Example 1) is significantly lower than that of the catalyst reacting using a single pure solvent (Comparative Example 1), indicating that the stability of the catalyst is greatly improved in the mixed solvent, which is consistent with the data results in Table 1.

[0039] Example 9 The in-situ regeneration method for deactivated catalysts in the gas-phase Beckmann rearrangement of cyclohexanone oxime is as follows: Taking the catalyst in Comparative Example 1 as an example, when the catalyst activity decreases by 20%, it is regenerated online. The regeneration process includes: passing a mixed solvent composed of acetonitrile-ethanol-water (5% ethanol and 5% water) through the catalyst and treating it at the reaction temperature for 24 hours to regenerate the deactivated catalyst in situ.

[0040] The performance evaluation steps for the regenerated catalyst are as described in Example 1, and the catalytic results are shown in Table 1.

[0041] Example 10 The in-situ regeneration method for the deactivated catalyst in the caprolactam amination reaction is as follows: 5.0 g of commercially available Al2O3 catalyst was placed in a fixed-bed reactor capable of in-situ regeneration; such as Figure 2 The diagram shows the process flow of the fixed-bed reactor. The raw material (caprolactam) and mixed solvent are added to the raw material feed heating vessel, and then sequentially pass through the raw material feed pump, raw material heat exchanger, and raw material vaporizer before entering the parallel reactor 5A. Ammonia gas is introduced, and the reaction temperature is 350 °C, the reaction pressure is 0.1 MPa, and the mass hourly space velocity is set to 1.0 h⁻¹. -1 The caprolactam amination reaction was carried out under an amino-acyl ratio of 20, yielding 6-aminohexanonitrile as the main product. The initial activity of the catalyst after 8 h showed a caprolactam conversion of 85.4% and a 6-aminohexanonitrile selectivity of 98.6%. The reaction products and solvent were separated under reduced pressure. The reaction solvent entered a regeneration solvent tank and then was pumped into a solvent heater for regeneration and recycling. When the catalyst conversion rate dropped below 80%, the reaction was switched to parallel reactor 5B. Parallel reactor 5A was switched to a mixed solvent of acetonitrile-water with an 8% water content (mixed solvent) for in-situ regeneration of the deactivated catalyst at 350 °C for 12 h. When the catalyst conversion rate in parallel reactor 5B dropped below 80%, the reaction was switched back to parallel reactor 5A. After system stabilization, the caprolactam conversion rate was measured at 86.3%, and the 6-aminohexanonitrile selectivity was 98.5%. The deactivated catalyst in parallel reactor 5B was regenerated using the same method. This regeneration operation could be repeated more than 20 times, and the performance of the regenerated catalyst was comparable to its initial activity.

[0042] The results of Example 10 demonstrate that the catalyst regeneration process provided by this invention has a certain degree of universality for catalysts that have become deactivated due to carbon deposition.

[0043] Example 11 Preparation of caprolactam amination catalyst: Weigh 16.8 g of titanium sulfate and add it to 200 mL of 0.1 mol / L dilute sulfuric acid solution. Heat at 40°C. 0 After dissolving under stirring at temperature C, 18.0 g of Beta molecular sieve was added in three portions. The resulting mixture was then heated to 60°C. 0 After stirring at C for 24 hours, the mixture was heated to dryness. The resulting solid was then heated to 100°C. 0 Dry at C for 12 h. Then dry at 1 0 Heating rate increased to 700 °C / min 0 Calcination at C for 12 h. The prepared catalyst is granulated into tablets to 10-20 mesh. 10.0 g of catalyst is weighed and loaded into a fixed-bed reactor, and then heated in an ammonia atmosphere at 20 mL / min at a flow rate of 1...0 Heating rate increased to 350 °C / min 0 The activated catalyst was obtained by activation at C for 4 h.

[0044] Performance evaluation of caprolactam amination catalyst: The performance evaluation of the activated catalyst in the caprolactam gas-phase amination reaction in a fixed-bed reactor is shown in Example 10, with the following specific conditions: the feed liquid was heated to 100°C. 0 C is a liquid caprolactam, the reaction gas is pure ammonia, and the reaction temperature is 350°C. 0 C, the reaction pressure is 0.1 MPa, and the mass hourly space velocity is set to 3.0 h⁻¹. -1 The molar ratio of ammonia to caprolactam was set at 10. After 1000 h of catalytic reaction in reactor 5A, the reaction was switched to reactor 5B to continue; reactor 5A was then switched to a 5% water-95% acetonitrile mixed solvent at 350 °C. 0 After treatment at temperature C for 24 hours, the reactor is ready for use; after 1000 hours of reaction in reactor 5B, it is switched back to reactor 5A, and so on. Test results show that the caprolactam conversion rate can be maintained at greater than 95% and the 6-aminohexanonitrile selectivity at greater than 98% within 12000 hours.

[0045] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A process for improving the stability of a cyclohexanone oxime gas-phase Beckmann rearrangement catalyst, characterized in that, Includes the following steps: The cyclohexanone oxime gas-phase Beckmann rearrangement reaction can be carried out by placing the catalyst in a fixed-bed reactor and then passing it through a solution composed of cyclohexanone oxime and a mixed solvent; wherein the mixed solvent is composed of at least two of a nitrile solvent, a C1-C6 alcohol and water; and the catalyst is a catalyst for the cyclohexanone oxime gas-phase Beckmann rearrangement reaction.

2. The process for improving the stability of the cyclohexanone oxime gas-phase Beckmann rearrangement catalyst according to claim 1, characterized in that, The C1-C6 alcohol solvent includes one of methanol, ethanol, propanol, isopropanol, butanol, or cyclohexanol.

3. The process for improving the stability of the cyclohexanone oxime gas-phase Beckmann rearrangement catalyst according to claim 1, characterized in that, The nitrile solvent is composed of one or a mixture of acetonitrile or hexanonitrile.

4. The process for improving the stability of the cyclohexanone oxime gas-phase Beckmann rearrangement catalyst according to claim 1, characterized in that, The catalyst is selected from one of aluminosilicate molecular sieves, pure silicon molecular sieves, silicon-phosphorus-aluminum molecular sieves, or titanium-silicon molecular sieves, or molecular sieves derived from these molecular sieves after acid-base modification.

5. The process for improving the stability of the cyclohexanone oxime gas-phase Beckmann rearrangement catalyst according to claim 1, characterized in that, The reaction apparatus is a fixed-bed reactor. The conditions for the gas-phase Beckmann rearrangement reaction of cyclohexanone oxime are as follows: using a 5-25 wt% cyclohexanone oxime-mixed solution as raw material, the reaction temperature is 320-400 °C, the reaction pressure is 0.1-2.0 MPa, and the mass hourly space velocity is set to 0.5-3.0 h⁻¹. -1 The process was carried out under the condition that the carrier nitrogen flow rate was 10~100 mL / min.

6. The process for improving the stability of the cyclohexanone oxime gas-phase Beckmann rearrangement catalyst according to claim 1, characterized in that, When the mixed solvent consists of nitrile solvents and water, the water content in the mixed solvent is 5-20 wt%; when the mixed solvent consists of C1-C6 alcohols and water, the water content in the mixed solvent is 1-30 wt%; when the mixed solvent consists of nitrile solvents and C1-C6 alcohol solvents, the alcohol content in the mixed solvent is 1-10 wt%.

7. An in-situ regeneration process for a carbon-deactivated catalyst, characterized in that, include: The deactivated catalyst with carbon deposits is placed in a fixed-bed reactor, and then a mixed solvent is introduced to treat it at the reaction temperature; wherein the mixed solvent is composed of at least two of a nitrile solvent, C1-C6 alcohol and water.

8. The in-situ catalyst regeneration process according to claim 7, characterized in that, The feedstock and mixed solvent of the fixed-bed reactor can be fed separately or in combination, and it is equipped with two reactors connected in parallel. When the catalyst in one reactor becomes carbonized and deactivated, the reactor is switched to the other reactor to continue the reaction. The deactivated catalyst is switched to the mixed solvent feed and regenerated in situ at the reaction temperature for 1 to 48 hours.

9. The in-situ catalyst regeneration process according to claim 7, characterized in that, The method can be applied to the regeneration process of deactivated catalysts in the gas-phase Beckmann rearrangement of cyclohexanone oxime to caprolactam or the amination of caprolactam to 6-aminohexanonitrile.

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