Method for preparing cyclohexanone oxime by catalyzing cyclohexanone through molecular sieve catalyst TS-1

Abstract

The invention discloses a method for preparing cyclohexanone oxime by catalyzing cyclohexanone through a molecular sieve catalyst TS-1, and belongs to the technical field of organic synthesis. According to the method, cyclohexanone, an ammonia source, hydrogen peroxide, a reaction solvent and a molecular sieve catalyst TS-1 are added into a reactor, the molar ratio of ammonia to cyclohexanone is (1.60-3.10): 1, the molar ratio of hydrogen peroxide to cyclohexanone is controlled to be (1.0-1.8): 1, the mass concentration of the molecular sieve catalyst TS-1 is 0.5-5%, the reaction temperature is controlled to be 35-80 DEG C, stirring reaction is carried out for 0.5-6 h, after the reaction is finished, a reaction product is subjected to post-treatment, and the product is obtained. And filtering, distilling and separating to obtain cyclohexanone-oxime. On the premise of innovative application of a molecular sieve catalyst, optimization of reaction conditions and simple, green and environment-friendly separation method, the invention provides a method for preparing cyclohexanone-oxime under mild and well-controlled reaction conditions, and the conversion rate of raw materials and the selectivity of products are effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and particularly relates to a method for preparing cyclohexanone oxime by catalyzing cyclohexanone with a molecular sieve catalyst TS-1. Background Art

[0002] Cyclohexanone oxime is an extremely critical intermediate in the chemical industry, especially in the production process of caprolactam. Traditional preparation methods have problems such as harsh reaction conditions, low selectivity, and environmental pollution. Although some existing patents relate to the preparation of cyclohexanone oxime, there is still room for improvement in the selection of catalysts and reaction efficiency. Traditional methods for preparing cyclohexanone oxime include hydroxylamine method, nitric oxide reduction method, etc., but these methods have some obvious defects. The traditional hydroxylamine method may require the use of a large amount of strong acid or strong base, which not only leads to serious equipment corrosion problems, but also produces a large amount of salt-containing wastewater, causing great pressure on the environment. The nitric oxide reduction method often requires high temperature and high pressure conditions during the reaction process, which has extremely high requirements for the reaction equipment. At the same time, the selectivity of the reaction is difficult to effectively control, and it is easy to produce a variety of by-products, which reduces the quality and yield of the product.

[0003] In recent years, molecular sieve catalysts have shown great potential in the field of organic synthesis. As a special titanium silicon molecular sieve, TS-1 catalyst has a unique pore structure and catalytic active center, and has shown high selectivity and high activity in many oxidation reactions. However, in the cyclohexanone oximation reaction under the action of TS-1 catalyst, the titanium active center in TS-1 plays a key role. Titanium atoms have suitable Lewis acidity and can activate reactants. The carbonyl oxygen atom in the cyclohexanone molecule coordinates with the titanium active center, so that the carbon atom of the carbonyl group carries a partial positive charge, thereby enhancing its electrophilicity to the nitrogen atom in the hydroxylamine source (such as hydroxylamine hydrochloride or hydroxylamine sulfate). The hydroxylamine source dissociates into hydroxylamine in the reaction system, and the lone pair of electrons on the nitrogen atom of hydroxylamine attacks the carbonyl carbon atom of cyclohexanone coordinated with the titanium active center to form a transition state. Subsequently, after processes such as proton transfer and molecular rearrangement, cyclohexanone oxime is finally generated. During the entire reaction process, the microporous structure of the TS-1 catalyst provides a suitable spatial environment for the adsorption and reaction of the reactants, and can effectively stabilize the transition state and reduce the activation energy of the reaction, thereby improving the reaction rate and selectivity. At present, there is still room for improvement in the method of applying the TS-1 catalyst to the preparation of cyclohexanone oxime, such as further optimization of the reaction conditions, further improvement of the conversion rate of cyclohexanone and the conversion rate of cyclohexanone oxime. Summary of the invention

[0004] The present invention aims to provide a method for preparing cyclohexanone oxime from cyclohexanone using a molecular sieve catalyst TS-1. The method has the advantages of mild reaction conditions, easy control, environmental friendliness, and greatly improved cyclohexanone conversion rate and cyclohexanone oxime selectivity.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing cyclohexanone oxime by catalyzing cyclohexanone with a molecular sieve catalyst TS-1, comprising the following steps:

[0007] (1) Cyclohexanone, an ammonia source, hydrogen peroxide, a reaction solvent and a molecular sieve catalyst TS-1 are added to a reactor, wherein the molar ratio of ammonia to cyclohexanone is (1.60-3.10):1, the molar ratio of hydrogen peroxide to cyclohexanone is controlled at (1.0-1.8):1, the mass concentration of the molecular sieve catalyst TS-1 is 0.5-5%, the reaction temperature is controlled at 35-80°C, and the reaction is stirred for 0.5-6h.

[0008] (2) After the reaction is completed, cyclohexanone oxime is obtained by filtration and distillation.

[0009] Based on the above technical solution, further, the reaction temperature in step (1) is 45-55°C, the reaction time is 0.5-3h, and the reaction pressure is 0-0.8Mpa.

[0010] Based on the above technical solution, further, the ammonia source described in step (1) is liquid ammonia, ammonia water, or ammonia gas; the selected pressure atmosphere is one of helium, nitrogen, and argon, or a mixture of two or more.

[0011] Based on the above technical solution, further, in step (1), the mass concentration of the molecular sieve catalyst TS-1 is 2.8-3.3%, the mass concentration of hydrogen peroxide is 40-50%, the mass concentration of ammonia water is 20-30%, the average particle size of the catalyst is 20-100 μm, preferably 65-90 μm, the molar ratio of ammonia to cyclohexanone is (1.80-2.35):1, and the molar ratio of hydrogen peroxide to cyclohexanone is (1.1-1.4):1.

[0012] Based on the above technical solution, further, in step (1), the stirring speed is controlled at 150-600 r / min, preferably 350-500 r / min.

[0013] Based on the above technical solution, further, the reaction solvent described in step (1) is one or a mixed solvent of two or more low-carbon alcohols, and the low-carbon alcohols include isopropanol, tert-butanol, n-butanol, and n-pentanol.

[0014] Based on the above technical scheme, further, the specific process in step (1) is to add the molecular sieve catalyst TS-1 into a reactor (equipped with a condenser and a dropping funnel), the mass concentration of the molecular sieve catalyst TS-1 is 0.5-5%, add cyclohexanone and a reaction solvent, control the temperature at 25-40°C, add an ammonia source through the dropping funnel on the reactor, stir evenly, add hydrogen peroxide, the molar ratio of ammonia to cyclohexanone is (1.60-3.10):1, the molar ratio of hydrogen peroxide to cyclohexanone is controlled at (1.0-1.8):1, control the temperature to 40-80°C, and stir the reaction for 0.5-6h.

[0015] Based on the above technical solution, further, the ammonia source described in step (1) is added dropwise in 2-4 times.

[0016] Compared with the existing method for preparing cyclohexanone oxime, the present invention has the following beneficial effects:

[0017] 1) Innovative application of catalysts: The TS-1 catalyst used in the reaction of the present invention has excellent microporous structure and stability, and is used in the preparation of cyclohexanone oxime, giving full play to its high selectivity and high activity. The catalyst can achieve high-efficiency catalysis under low temperature and normal pressure conditions, reducing the occurrence of side reactions, which is in sharp contrast to the harsh high temperature and high pressure conditions in traditional methods. At the same time, the overall system is a heterogeneous system, which is convenient for catalyst separation.

[0018] 2) Optimized reaction conditions: In addition to the investigation of reaction temperature, pressure, time and solvent screening conditions, the present invention further investigated the order of adding materials to the reaction from a mechanism perspective for the first time. Under the determined reaction conditions, both the conversion rate of cyclohexanone and the selectivity of cyclohexanone oxime reached a high level. This condition optimization based on the reaction mechanism is one of the core innovations of the present invention.

[0019] 3) Green and environmentally friendly process: The reaction system and post-treatment method adopted in the present invention are relatively simple, avoiding the use of a large amount of toxic and harmful chemical reagents, reducing pollution to the environment, and meeting the development requirements of green chemistry. DETAILED DESCRIPTION

[0020] The present invention is specifically described below with reference to examples.

[0021] Embodiment 1:

[0022] The reaction temperature selected in this embodiment is 80°C: first, 3g of TS-1 catalyst is weighed into a three-necked flask, and 4.735g of cyclohexanone, 13.528g of 25% ammonia water, 3.939g of 50% hydrogen peroxide and 66.29g of tert-butyl alcohol are added in sequence, at normal pressure, the reaction temperature is 80°C, the rotation speed is 400r / min, and the reaction is stirred and contacted for 1h. The conversion rate of cyclohexanone is 70% and the selectivity of cyclohexanone oxime is 85% as calculated by gas chromatography analysis.

[0023] Embodiment 2:

[0024] The reaction temperature used in this embodiment is 70°C: first, 3g of TS-1 catalyst is weighed into a three-necked flask, and 4.735g of cyclohexanone, 13.528g of 25% ammonia water, 3.939g of 50% hydrogen peroxide and 66.29g of tert-butyl alcohol are added in sequence, at normal pressure, the reaction temperature is 70°C, the rotation speed is 400r / min, and the reaction is stirred and contacted for 1h. After analysis and calculation, the conversion rate of cyclohexanone is 85%, and the selectivity of cyclohexanone oxime is 88%.

[0025] Embodiment 3:

[0026] The reaction temperature used in this example is 50°C: first, 3g of TS-1 catalyst is weighed into a three-necked flask, and 4.735g of cyclohexanone, 13.528g of 25% ammonia water, 3.939g of 50% hydrogen peroxide and 66.29g of tert-butyl alcohol are added in sequence, at normal pressure, the reaction temperature is 50°C, the rotation speed is 400r / min, and the reaction is stirred and contacted for 1h. After analysis and calculation, the conversion rate of cyclohexanone is 99%, and the selectivity of cyclohexanone oxime is 90%.

[0027] Embodiment 4:

[0028] The order of adding materials selected in this embodiment is hydrogen peroxide first and then ammonia water: first weigh 1.456g of TS-1 catalyst into a three-necked flask, add 4.735g of cyclohexanone and 14.205g of tert-butyl alcohol in sequence, control the temperature at 35°C, add 3.939g of 50% hydrogen peroxide with a dropping funnel, stir well for 30min, then add 13.528g of 25% ammonia water three times (about 4.5g of ammonia water each time), raise the temperature to 50°C at normal pressure, rotate at 200r / min, and stir well for 1h. After analysis and calculation, the conversion rate of cyclohexanone is 75%, and the selectivity of cyclohexanone oxime is 80%.

[0029] Embodiment 5:

[0030] The order of adding materials selected in this embodiment is ammonia water first and then hydrogen peroxide: first weigh 1.456g of TS-1 catalyst into a three-necked flask, add 4.735g of cyclohexanone and 14.205g of tert-butyl alcohol in sequence, and when the temperature is controlled at 35°C, use a dropping funnel to drop 13.528g of 25% ammonia water three times (about 4.5g of ammonia water is dropped each time), and after fully stirring for 30min, continue to drop 3.939g of 50% hydrogen peroxide, normal pressure, temperature rise to 50°C, speed 200r / min, fully stir and contact for 1h. After analysis and calculation, it is found that the conversion rate of cyclohexanone is 93%, and the selectivity of cyclohexanone oxime is 99%.

[0031] Comparative Example 1:

[0032] This comparative example is compared with Example 5, and the reaction is evaluated by pressurizing an intermittent reactor: first, 1.456g of TS-1 catalyst is weighed into the reactor, and 4.735g of cyclohexanone, 13.528g of 25% ammonia water, 3.939g of 50% hydrogen peroxide and 14.205g of tert-butyl alcohol are added in sequence. After nitrogen replacement of the atmosphere three times, the pressure is maintained at 0.5Mpa, the reaction temperature is 50°C, the speed is 200r / min, and the contact is fully stirred for 1h. After analysis and calculation, the conversion rate of cyclohexanone is 77%, and the selectivity of cyclohexanone oxime is 95%.

[0033] It can be seen from the results of the above embodiments that the optimized method of the present invention is used to prepare cyclohexanone oxime, not only the reaction conditions are mild and precisely controllable, but also a higher conversion rate of cyclohexanone and selectivity of cyclohexanone oxime can be obtained.

[0034] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited to the specific details of the above embodiments. Within the technical concept of the present invention, the technical scheme of the present invention can be subjected to a variety of simple variations and combinations, all of which fall within the protection scope of the present invention.

Claims

1. A method for preparing cyclohexanone oxime by catalyzing cyclohexanone with molecular sieve catalyst TS-1, characterized in that: The following steps are involved: (1) Cyclohexanone, an ammonia source, hydrogen peroxide, a reaction solvent and a molecular sieve catalyst TS-1 are added to a reactor, wherein the molar ratio of ammonia to cyclohexanone is (1.60-3.10):1, the molar ratio of hydrogen peroxide to cyclohexanone is controlled at (1.0-1.8):1, the mass concentration of the molecular sieve catalyst TS-1 is 0.5-5%, the reaction temperature is controlled at 35-80°C, and the reaction is stirred for 0.5-6h. (2) After the reaction is completed, cyclohexanone oxime is obtained by filtration and distillation.

2. The method according to claim 1, characterized in that The reaction temperature in step (1) is 45-55° C., the reaction time is 0.5-3 h, and the reaction pressure is 0-0.8 MPa.

3. The method according to claim 1, characterized in that The ammonia source described in step (1) is liquid ammonia, ammonia water, or ammonia gas; the pressure atmosphere selected is one of helium, nitrogen, and argon, or a mixture of two or more.

4. The method according to claim 1, characterized in that: In step (1), the mass concentration of the molecular sieve catalyst TS-1 is 2.8-3.3%, the mass concentration of the hydrogen peroxide is 40-50%, the mass concentration of the ammonia water is 20-30%, the average particle size of the catalyst is 20-100 μm, preferably 65-90 μm, the molar ratio of ammonia to cyclohexanone is (1.80-2.35):1, and the molar ratio of the hydrogen peroxide to cyclohexanone is (1.1-1.4):

1.

5. The method according to claim 1, characterized in that In step (1), the stirring speed is controlled at 150-600 r / min, preferably 350-500 r / min.

6. The method according to claim 1, characterized in that The reaction solvent described in step (1) is one or a mixed solvent of two or more low-carbon alcohols, and the low-carbon alcohols include isopropanol, tert-butanol, n-butanol, and n-pentanol.

7. The method according to any one of claims 1 to 6, characterized in that: The specific process in step (1) is to add the molecular sieve catalyst TS-1 into a reactor (equipped with a condenser and a dropping funnel), the mass concentration of the molecular sieve catalyst TS-1 is 0.5-5%, add cyclohexanone and a reaction solvent, control the temperature at 25-40° C., add an ammonia source through the dropping funnel on the reactor, stir evenly, add hydrogen peroxide, the molar ratio of ammonia to cyclohexanone is (1.60-3.10):1, the molar ratio of hydrogen peroxide to cyclohexanone is controlled at (1.0-1.8):1, control the temperature to 40-80° C., and stir the reaction for 0.5-6 hours.

8. The method according to claim 7, characterized in that The ammonia source described in step (1) is added dropwise in 2-4 portions.