CN1305855C - Process for preparing epsilon-hexanolactam by catalyzing cyclohexanone-oxime rearranging - Google Patents

Abstract

The invention relates to a method for preparing ε-caprolactam by catalyzing cyclohexanone oxime by using N-protonated caprolactam as cationic group Brönsted acidic ionic liquid as catalyst and reaction medium through Beckmann rearrangement reaction. The ε-caprolactam can be generated with high conversion rate and high selectivity at mild reaction temperature and short reaction time, and the acidic ionic liquid can be used repeatedly. Because the present invention uses the acidic ionic liquid with the protonated product of the reaction as a cationic group as the catalyst and the reaction medium, the product is no longer combined with the acidic ionic liquid, and there is no need to add alkali for neutralization after the reaction. The reaction system is simple and does not require It will cause environmental pollution, the acidic ionic liquid does not corrode equipment, the preparation cost of the ionic liquid is low, resources are saved, and it has a good industrial application prospect.

Description

Method for preparing ε-caprolactam by catalytic cyclohexanone oxime rearrangement

technical field

The present invention relates to a method for preparing ε-caprolactam by catalytic cyclohexanone oxime rearrangement, specifically, the present invention relates to a Brnsted acidic room temperature ionic liquid with N-protonated caprolactam as cationic group as catalyst and reaction Catalytic method of cyclohexanone oxime via Beckmann rearrangement to prepare ε-caprolactam.

Background technique

ε-caprolactam is an important chemical raw material, mainly used as a polymerized monomer in the production of nylon 6 fiber and resin, and widely used in textile, plastic and artificial leather industries. The traditional production process of ε-caprolactam is to prepare ε-caprolactam through Beckmann rearrangement of cyclohexanone oxime. The rearrangement is carried out with oleum containing 30% SO ₃ at 100-130°C. After the reaction, a large amount of ammonia water is added to free the caprolactam combined with concentrated sulfuric acid. But this process has many disadvantages: (1) by-product a large amount of ammonium sulfate (2-4 tons/ton caprolactam) with low added value; (2) equipment corrosion is serious; (3) complicated follow-up caprolactam purification process; (4) produce A large amount of acid waste water pollutes the environment. Therefore, developing a clean catalytic process that is environmentally friendly, non-polluting, does not produce solid waste, and is easy to separate from the reaction system has become the research and development object of chemical and chemical researchers for a long time. Although the gas-phase Beckmann rearrangement using solid acids such as molecular sieves and metal oxides as catalysts solves the above problems to a certain extent, the harsh reaction conditions (350-500 °C high temperature) and rapid catalyst deactivation make the by-products in the rearrangement products More and the catalyst requires frequent regeneration. It has been reported recently (J.Org.Chem.1998, 63, 9100) that cyclohexanone oxime can be rearranged into caprolactam in supercritical water, but the reaction conversion rate is very low, and supercritical water requires high temperature and pressure, making it difficult for industrial application very big. Therefore, it is still necessary to find a liquid-phase Beckmann rearrangement reaction catalytic system and process with mild reaction conditions and environmental friendliness.

A room temperature ionic liquid is a substance that is liquid at room temperature or near room temperature and is composed entirely of specific cations and anions. Compared with solid substances, it is liquid; compared with traditional liquid substances, it is ionic. Therefore, compared with other solid or liquid materials, ionic liquids often exhibit unique physical and chemical properties and unique functions. Since the early 1980s, countries around the world have carried out research on ionic liquids. Room temperature ionic liquids have excellent physical properties such as wide liquid temperature range, almost no vapor pressure, large heat capacity, high thermal stability, and reusability. The chemical properties have been widely studied in various fields such as organic synthesis, catalytic chemistry, electrochemistry, separation analysis, friction and lubrication. Studies have shown that the first step of the protonic acid-catalyzed Beckmann rearrangement reaction is the partial protonation of the nitrogen-oxygen bond of the oxime, followed by the formation of a cyclic imide positive ion intermediate, and the strong Coulomb attraction inside the ionic liquid can enhance this positive charge The stability of the intermediate, and the weak coordination ability of the ionic liquid may enhance the degree of freedom of the hydrogen ion dissociated from the protonic acid, making it more acidic. Therefore, the Beckmann rearrangement reaction is more suitable in ionic liquids than ordinary solvents. In 2001, Deng Youquan et al. (Tetrahedron Letters, 2001, 42, 403-405) successfully realized the high-conversion and high-selectivity Beckmann rearrangement of cyclohexanone oxime to prepare ε-caprolactam in an imidazole-based room temperature ionic liquid using a phosphorus compound as a catalyst. It cannot be reused, and it is difficult to separate the product from the catalytic system. In recent years, functionalized room temperature ionic liquids have been paid attention to because of their high activity and high selectivity. In 2004, it was reported in the literature (Tetrahedron Letters, 2004, 45, 2681-2683) that using imidazole cation functionalized ionic liquids as reaction media and catalysts can carry out effective Beckmann rearrangement, but weakly basic product caprolactam and acidic ionic liquids are still There is a considerable degree of combination, which makes it difficult to separate the product from the catalyst, thus limiting its industrial application prospects. Therefore, developing a room-temperature ionic liquid catalytic system that is highly efficient, easy to separate from the product caprolactam, and reusable is the key to cleanly catalyzing the Beckmann rearrangement of cyclohexanone oxime to prepare ε-caprolactam in room temperature ionic liquids.

It is worth mentioning that the ε-caprolactam molecule has a tertiary amine structure similar to imidazole and pyridine. If it is combined with a strong Brnsted acid, it can form an ionic liquid with Brnsted acidity with caprolactam as the cation. If such an ionic liquid is used as a catalyst and a reaction medium to catalyze cyclohexanone oxime to prepare ε-caprolactam through Beckmann rearrangement, it is conceivable to combine the product ε-caprolactam with the Brönsted acidic ionic liquid catalyst and medium using ε-caprolactam as a cation The problem is solved due to the existence of the following dynamic equilibrium reaction:

Where X ⁻ =BF ₄ ⁻ , CF ₃ COO ⁻ , ClCH ₂ COO ⁻ , C ₆ H ₄ COO ⁻ , C ₆ H ₄ CH ₂ COO ⁻ , NO ₃ ⁻ . The product ε-caprolactam and the ionic liquid catalyst and reaction medium with caprolactam as cations can be separated by appropriate separation and extraction methods, so that a large amount of solid by-products are no longer produced, and the ionic liquid catalyst and reaction medium can be used again.

Contents of the invention

The object of the present invention is to provide a method for preparing ε-caprolactam by catalyzing cyclohexanone oxime through Beckmann rearrangement reaction using N-protonated caprolactam as cationic Brönsted acidic ionic liquid as catalyst and reaction medium.

A kind of method that catalysis cyclohexanone oxime rearrangement prepares epsilon-caprolactam is characterized in that taking N-protonated caprolactam as the Brnsted acidic ionic liquid of cationic group as catalyst and reaction medium, its chemical structural formula uses formula (I )express:

Where X ^- is the anion group of Brnsted acid HX, X ^- is selected from BF ₄ ^- , CF ₃ COO ^- , ClCH ₂ COO ^- , C ₆ H ₄ COO ^- , C ₆ H ₄ CH ₂ COO ^- , NO ₃ One of ^- ; controlling the reaction temperature to 50-120° C., and the reaction time to 1-6 hours, to catalyze the rearrangement of cyclohexanone oxime to prepare ε-caprolactam.

The molar ratio of cyclohexanone oxime to ionic liquid in the present invention is 1:1-1:4.

The preferred reaction temperature of the present invention is 70-100 DEG C, the preferred reaction time is 3-5 hours, and the by-product of the reaction is only cyclohexanone.

When the molar ratio of N-protonated caprolactam Brnsted acidic ionic liquid and cyclohexanone oxime is 3:1, react at 90-100 ℃ for 4 hours, the conversion rate of cyclohexanone oxime is 93.0%-97.3%, caprolactam The selectivity of the cyclohexanone is 87.0%-95.0%, and the selectivity of the corresponding by-product cyclohexanone is 13.0%-5.0%.

Compared with the Beckmann rearrangement reaction process widely used in the existing industry and the catalytic process of phosphorus-containing compounds in room temperature ionic liquids, the present invention is characterized in that:

(1) The acidic ionic liquid is not only a catalyst but also a reaction medium, which simplifies the reaction system;

(2) clever use of the product ε-caprolactam of this reaction and inorganic or organic acid to synthesize an acidic room temperature ionic liquid, so that the product generated by the reaction is no longer combined with the acidic ionic liquid, so there is no need to add alkali for neutralization, and no solid waste is generated, which is beneficial Product separation and purification;

(3) The room temperature ionic liquid has almost no vapor pressure, which avoids the environmental pollution caused by the volatilization of traditional organic solvents;

(4) by-product is single, is only cyclohexanone, can be recycled industrially and prepares cyclohexanone oxime;

(5) The preparation of N-protonated caprolactam Brnsted acidic ionic liquid is simple, and the raw material caprolactam used is cheaper than the methylimidazole used in the general synthesis of ionic liquids, which greatly reduces the production cost;

(6) No harmful gas is produced during the reaction process, which is more environmentally friendly;

(7) The method has strong industrial operability and is suitable for large-scale preparation of ε-caprolactam.

Detailed ways

In order to further illustrate the details of the present invention, several embodiments are listed below, but should not be limited thereto.

Example 1

Take 15mmol of caprolactam fluoroboric acid ionic liquid, put it in a 100ml round bottom flask, add 5mmol of cyclohexanone oxime, gradually raise the temperature to 50°C for 3 hours under stirring, and cool the reactant to room temperature to obtain a homogeneous liquid mixture, take 1ml of it and add 6ml Acetone, fully mixed, chromatographic analysis, the conversion rate is 13%, the selectivity of the product ε-caprolactam is 65%, and the by-product is cyclohexanone.

Example 2

Take 20mmol of caprolactam fluoroboric acid ionic liquid, put it in a 100ml round bottom flask, add 5mmol of cyclohexanone oxime, gradually raise the temperature to 60°C for 3 hours under stirring, cool the reactant to room temperature to obtain a homogeneous liquid mixture, take 1ml of it and add 6ml Acetone, mixed well, analyzed by gas chromatography, the conversion rate was 61%, and the selectivity of the product ε-caprolactam was 81%.

Example 3

Take 10mmol of caprolactam fluoroboric acid ionic liquid, put it in a 100ml round bottom flask, add 5mmol of cyclohexanone oxime, gradually raise the temperature to 90°C under stirring and keep it for 6 hours, cool the reactant to room temperature to obtain a homogeneous liquid mixture, take 1ml of it and add 6ml Acetone, mixed well, analyzed by gas chromatography, the conversion rate was 90%, and the selectivity was 84%.

Example 4

Take 15mmol of caprolactam fluoroboric acid ionic liquid, put it in a 100ml round bottom flask, add 5mmol of cyclohexanone oxime, gradually raise the temperature to 90°C for 4 hours under stirring, cool the reactant to room temperature to obtain a homogeneous liquid mixture, take 1ml of it and add 6ml Acetone, mixed well, analyzed by gas chromatography, the conversion rate was 95.8%, and the selectivity was 89.4%.

Example 5

Same as Example 4, but the amount of caprolactam fluoboric acid ionic liquid was enlarged to 1.0 mol, and the amount of cyclohexanone oxime was enlarged to 0.33 mol, reacted in a 500ml round-bottomed flask, and gradually heated to 90°C under stirring for 4 hours. The reactant was cooled to room temperature to obtain a homogeneous liquid mixture, 1 ml of which was added to 6 ml of acetone, mixed thoroughly, and analyzed by gas chromatography, the conversion rate was 95.0%, and the selectivity was 87.0%.

Example 6

Take 15mmol of caprolactam trifluoroacetic acid ionic liquid, put it in a 100ml round bottom flask, add 5mmol of cyclohexanone oxime, gradually raise the temperature to 100°C for 4 hours under stirring, cool the reactant to room temperature to obtain a homogeneous liquid mixture, take 1ml of it and add 6ml of acetone, fully mixed, analyzed by gas chromatography, the conversion rate was 97.3%, and the selectivity was 93.5%.

Example 7

Take 15mmol of caprolactam benzoic acid ionic liquid, put it in a 100ml round bottom flask, add 5mmol of cyclohexanone oxime, gradually raise the temperature to 100°C for 4 hours under stirring, cool the reactant to room temperature to obtain a homogeneous liquid mixture, take 1ml of it and add 6ml Acetone, mixed well, analyzed by gas chromatography, the conversion rate was 94.6%, and the selectivity was 92.7%.

Example 8

Take 15mmol of caprolactam chloroacetic acid ionic liquid, put it in a 100ml round bottom flask, add 5mmol of cyclohexanone oxime, gradually raise the temperature to 100°C for 4 hours under stirring, and cool the reactant to room temperature to obtain a homogeneous liquid mixture, take 1ml of it and add 6ml Acetone, mixed well, analyzed by gas chromatography, the conversion rate was 93.7%, and the selectivity was 94.6%.

Example 9

Take 15mmol of caprolactam phenylacetic acid ionic liquid, put it in a 100ml round bottom flask, add 5mmol of cyclohexanone oxime, gradually raise the temperature to 100°C for 4 hours under stirring, cool the reactant to room temperature to obtain a homogeneous liquid mixture, take 1ml of it and add 6ml Acetone, mixed well, analyzed by gas chromatography, the conversion rate was 93.0%, and the selectivity was 95.0%.

Claims (3)

1. A method for preparing ε-caprolactam by catalyzing the rearrangement of cyclohexanone oxime is characterized in that the Brnsted acidic ionic liquid with N-protonated caprolactam as cationic group is used as catalyst and reaction medium, and its chemical structural formula is as follows: (I) means: Where X ^- is the anion group of Brnsted acid HX, X ^- is selected from BF ₄ ^- , CF ₃ COO ^- , ClCH ₂ COO ^- , C ₆ H ₄ COO ^- , C ₆ H ₄ CH ₂ COO ^- , NO ₃ One of ^- ; controlling the reaction temperature to 50-120° C., and the reaction time to 1-6 hours, to catalyze the rearrangement of cyclohexanone oxime to prepare ε-caprolactam. 2. The method according to claim 1, characterized in that the molar ratio of cyclohexanone oxime to ionic liquid is 1:1-1:4. 3. The method according to claim 1, characterized in that the reaction temperature is 70-100°C and the reaction time is 3-5 hours.