CN-121972239-A - Method for improving stability of cyclohexanone oxime gas-phase Beckmann rearrangement catalyst and application

CN121972239ACN 121972239 ACN121972239 ACN 121972239ACN-121972239-A

Abstract

The invention provides a process for improving stability of a cyclohexanone oxime gas-phase Beckmann rearrangement catalyst, which comprises the following steps of placing the catalyst in a fixed bed reactor, and introducing a solution consisting of cyclohexanone oxime-mixed solvent to perform a cyclohexanone oxime gas-phase Beckmann rearrangement reaction, wherein the mixed solvent is formed by mixing at least two of nitrile solvents, C1-C6 alcohols and water, and the catalyst is used for the cyclohexanone oxime gas-phase Beckmann rearrangement reaction. Compared with a single solvent system, the method provided by the invention can obviously improve the stability of the cyclohexanone oxime gas-phase Beckmann rearrangement catalyst by adopting the mixed solvent. The raw materials and the mixed solvent of the fixed bed reaction device can be fed separately or mixed, two parallel reactors are adopted, when the carbon deposition of the catalyst of one reactor is deactivated, the reactor is switched to the other reactor to continue the reaction, and the deactivated catalyst is switched to the mixed solvent for feeding and in-situ treatment is carried out, so that the catalyst performance regeneration can be realized.

Inventors

YE LINMIN
YUAN YOUZHU
FU QI

Assignees

厦门大学

Dates

Publication Date: 20260505
Application Date: 20260114

Claims (9)

1. A process for improving the stability of a cyclohexanone oxime vapor-phase beckmann rearrangement catalyst, comprising the steps of: The method comprises the steps of placing a catalyst in a fixed bed reactor, and then introducing a solution consisting of cyclohexanone oxime and a mixed solvent to perform a vapor phase Beckmann rearrangement reaction of the cyclohexanone oxime, wherein the mixed solvent is formed by mixing at least two of a nitrile solvent, C1-C6 alcohol and water, and the catalyst is used for the vapor phase Beckmann rearrangement reaction of the cyclohexanone oxime.
2. Process for improving the stability of a cyclohexanone oxime gas phase beckmann rearrangement catalyst according to claim 1, characterized in that the C1-C6 alcohol solvent comprises one of methanol, ethanol, propanol, isopropanol, butanol or cyclohexanol.
3. The process for improving the stability of a cyclohexanone oxime vapor phase beckmann rearrangement catalyst according to claim 1, wherein the nitrile solvent is formed by mixing one or two of acetonitrile and capronitrile.
4. Process for improving the stability of a cyclohexanone oxime vapor phase beckmann rearrangement catalyst according to claim 1, characterized in that the catalyst is selected from one of aluminium-silicon molecular sieves, pure silicon molecular sieves, silicon-phosphorus-aluminium 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, wherein the reaction device is a fixed bed reactor, the condition of the cyclohexanone oxime gas-phase Beckmann rearrangement reaction is that 5-25wt% of cyclohexanone oxime-mixed solution is taken as a raw material, and the reaction is carried out under the conditions that the reaction temperature is 320-400 ℃, the reaction pressure is 0.1-2.0 MPa, the mass airspeed is set to 0.5-3.0 h -1 , and the carrier gas nitrogen flow is 10-100 mL/min.
6. The process for improving the stability of a cyclohexanone oxime vapor phase beckmann rearrangement catalyst according to claim 1, wherein when the mixed solvent is composed of 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%, and when the mixed solvent is composed of nitrile solvent and C1-C6 alcohol solvent, the alcohol content in the mixed solvent is 1-10 wt%.
7. The in-situ regeneration process of the carbon deposition deactivated catalyst is characterized by comprising the steps of placing the carbon deposition deactivated catalyst in a fixed bed reactor, and then introducing a mixed solvent for treatment at a reaction temperature, wherein the mixed solvent is formed by mixing at least two of a nitrile solvent, C1-C6 alcohol and water.
8. The in-situ regeneration process of the catalyst according to claim 7, wherein the raw materials and the mixed solvent of the fixed bed reactor can be fed independently or mixed, and are provided with two reactors connected in parallel, when the carbon deposition of the catalyst of one reactor is deactivated, the reactor is switched to the other reactor to continue the reaction, the deactivated carbon deposition catalyst is switched to the mixed solvent for feeding, and the deactivated catalyst is regenerated in situ at the reaction temperature for 1-48 h.
9. The in-situ catalyst regeneration process according to claim 7, wherein the method is applicable to the regeneration process of carbon deposition deactivated catalyst in the reaction of preparing caprolactam by cyclohexanone oxime gas phase Beckmann rearrangement or the reaction of preparing 6-aminocapronitrile by caprolactam ammonification.

Description

Method for improving stability of cyclohexanone oxime gas-phase Beckmann rearrangement catalyst and application Technical Field The invention relates to the technical field of catalysts, in particular to a treatment method for improving the stability of a cyclohexanone oxime gas-phase Beckmann rearrangement catalyst, an in-situ regeneration process of the catalyst and a continuous production process flow, which are suitable for industrial production scenes of preparing caprolactam by the cyclohexanone oxime gas-phase Beckmann rearrangement and preparing 6-aminocapronitrile by ammonification of caprolactam. Background The Beckmann rearrangement of cyclohexanone oxime is a typical acid catalytic process, and the traditional liquid phase rearrangement usually adopts concentrated sulfuric acid or fuming sulfuric acid as a catalyst, so that the method not only causes serious corrosion to reaction equipment, but also forms serious threat to the environment. In contrast, the solid acid catalyst is used for gas phase rearrangement, so that the method has higher atom utilization rate, reduces resource waste, and can also avoid pollution caused by the liquid catalyst. The product and the catalyst are easier to separate under the gas phase reaction condition, the subsequent treatment cost is obviously reduced, and the method is a new process route conforming to the green development concept. The solid acid catalysts commonly used for the vapor phase beckmann rearrangement of cyclohexanone oxime can be divided into two main types, namely oxides and molecular sieves, and the stability of the catalyst is directly related to the efficiency of the reaction, the selectivity of the product, the production cost and the sustainability of the process. In particular, the stability of the catalyst has a major impact on the reaction efficiency in that, firstly, the stable catalyst (e.g., modified ZSM-5 molecular sieve) maintains the number and strength of active sites (e.g., acid sites) for a long period of time, ensuring a continuous and efficient conversion of cyclohexanone oxime to caprolactam. The stable catalyst can maintain high conversion rate (usually more than 95 percent), reduce the downtime of frequent replacement of the catalyst, and if the catalyst stability is reduced, the catalyst is deactivated due to carbon deposition, framework dealumination or acid position loss, the reaction conversion rate is reduced, so that the cyclohexanone oxime is not completely converted, and the raw material waste and the subsequent separation cost are increased. secondly, the influence on the selectivity of the product is that the stable catalyst can keep proper acid site distribution and pore channel structure, the Beckmann rearrangement main reaction is promoted to the greatest extent, side reactions (such as cyclohexanone oxime is decomposed into cyclohexanone, nitriles or tar) are reduced, the selectivity of caprolactam can be kept above 90%, and the stability of the catalyst is reduced or the catalyst is inactivated, so that the acid site strength or pore channel structure is changed, and the side reactions are promoted to be increased. For example, clogging of the channels with carbon deposition may cause cyclohexanone oxime to decompose at non-selective sites, selectivity to decrease, and by-products to increase, decreasing product quality. Thirdly, the catalyst with high stability has long service life, reduces the replacement frequency and lowers the production cost. Stable catalysts can also operate under wider reaction conditions (e.g., high temperature or aqueous atmosphere), simplifying process control, while low stability catalysts can increase operating costs and downtime losses due to frequent deactivation requiring periodic regeneration or replacement of the catalyst. Fourth, the process sustainability is affected by the fact that the stable catalyst reduces the generation of waste catalyst, meets the requirements of green chemical industry, the gas-phase Beckmann rearrangement is environment-friendly than the traditional liquid-phase process (concentrated sulfuric acid method), and the catalyst stability further reduces the requirements of byproduct and waste treatment. However, the low stability or deactivated catalyst may require frequent treatment due to carbon deposition or structural damage, increasing waste treatment burden, and if byproducts are increased, additional separation and waste treatment processes are required, increasing environmental load. Fifth, the impact on reaction conditions and operational flexibility is that stable catalysts (e.g., high Si/Al ratios or phosphorus modified ZSM-5) can run for long periods of time at high temperatures (250-400 ℃) allowing for more flexible reaction condition optimization (e.g., increasing temperature to increase reaction rate), while low stability catalysts are sensitive to high temperatures or moisture (e.g., framework dealumination), limiting the range o