A method for the preparation of a sulfur and phosphorus based catalyst for liquid phase beckmann rearrangement to caprolactam
By preparing sulfur- and phosphorus-based catalysts for caprolactam production, the problems of catalyst corrosivity and by-product ammonium sulfate in existing technologies have been solved, achieving efficient catalyst separation and highly selective caprolactam synthesis.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- PINGDINGSHAN UNIVERSITY
- Filing Date
- 2023-09-06
- Publication Date
- 2026-06-12
Smart Images
Figure SMS_1
Abstract
Description
Technical Field
[0001] This invention relates to a catalyst, and more particularly to a method for preparing a sulfur- and phosphorus-based catalyst for the liquid-phase Beckmann rearrangement to caprolactam. Background Technology
[0002] Caprolactam is an important organic chemical raw material, mainly used in the production of polyamide-6 fibers, polyamide resins, and films. The main caprolactam production processes include the cyclohexanone-hydroxylamine method, the toluene method, the cyclohexane nitrosation method, and the cyclohexanone ammonium oxime method. Due to its advantages such as simple process flow, mild reaction conditions, high reactant conversion rate, and high selectivity, the cyclohexanone oxime liquid-phase Beckmann rearrangement (cyclohexanone ammonium oxime method) has become the mainstream process for caprolactam production. However, the strong corrosiveness of concentrated sulfuric acid catalysts and the large amount of low-value ammonium sulfate byproducts produced during the catalytic reaction are technical challenges that urgently need to be overcome. Therefore, research on green catalysis for caprolactam production without ammonium sulfate rearrangement is of great significance.
[0003] Existing methods for producing caprolactam include: 1. Cyclohexanone-hydroxylamine method: This process involves the reaction of cyclohexanone with hydroxylamine to generate cyclohexanone oxime, which undergoes Beckmann rearrangement in fuming sulfuric acid, followed by neutralization to obtain caprolactam. Disadvantages of this process include: high byproduct ammonium sulfate production (1.8 tons of ammonium sulfate / 1 ton of caprolactam) and complex caprolactam refining. 2. Toluene nitrosation method: This process uses toluene as a raw material, which is oxidized to obtain benzoic acid. Benzoic acid is hydrogenated to generate cyclohexane, which is then reacted with a nitrosylating agent in a sulfuric acid medium to synthesize caprolactam. Disadvantages of this process include: difficult catalyst recovery, high byproduct ammonium sulfate production (4.2 tons of ammonium sulfate / 1 ton of caprolactam), and complex caprolactam refining. 3. Cyclohexane photonitrosation method: This process involves the reaction under mercury lamp irradiation. Cyclohexane reacts with nitrosyl chloride and hydrogen chloride to generate hydrochloride oxime, which then undergoes Beckmann rearrangement in fuming sulfuric acid to obtain caprolactam. This method involves nitrifying cyclohexane to produce nitrocyclohexane, which is then hydrogenated to cyclohexanone oxime. The disadvantages of this process include high energy consumption, severe equipment corrosion, and high initial investment.
[0004] The catalyst provided by this invention has the following advantages in the Beckmann rearrangement catalytic reaction of cyclohexanone oxime: no ammonium sulfate byproduct, easy separation of catalyst and product, maximum cyclohexanone oxime conversion rate of 100%, and maximum caprolactam selectivity of 99.5%. Summary of the Invention
[0005] To address the problems of existing technologies, this invention provides a method for preparing a sulfur- and phosphorus-based catalyst for the liquid-phase Beckmann rearrangement to caprolactam production. The catalyst exhibits a maximum cyclohexanone oxime conversion of 100%, a maximum caprolactam selectivity of 99.5%, and good catalyst stability.
[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:
[0007] A method for preparing a sulfur- and phosphorus-based catalyst for the liquid-phase Beckmann rearrangement to caprolactam includes the following steps:
[0008] (1) Under certain reaction conditions, phosphorus chloride is first weighed and dissolved in a solvent to prepare solution A, and then sulfur-containing organic compounds are dissolved in a solvent to prepare solution B.
[0009] (2) Subsequently, under microwave reaction conditions, A and B were mixed and placed in a reactor for reaction;
[0010] (3) The catalyst precursor obtained in step (2) is washed with solvent and dried under vacuum to obtain the catalyst.
[0011] Further, in step (1), phosphorus chloride is dissolved in a solvent and placed in an open beaker for magnetic stirring to obtain solution A. Then, sulfur-containing organic matter is dissolved in a solvent and placed in an open beaker for magnetic stirring to obtain solution B. The stirring temperature is 20-40℃, the stirring speed is 200-500r / min, and the stirring time is 15min-60min. The mass ratio of phosphorus chloride to solvent is (1-3):7, and the mass ratio of sulfur-containing organic matter to solvent is (1-3):7.
[0012] Furthermore, the phosphorus chloride is one of phosphorus trichloride and phosphorus pentachloride.
[0013] Further, the sulfur-containing organic compound in step (1) is 4,4'-dihydroxydiphenyl sulfide, 3,3'-dihydroxydiphenyl disulfide, thiol-polyethylene glycol-hydroxy, thiol-polyethylene glycol-hydroxy, 4-hydroxybenzenethiophenol, 2-hydroxybenzenethiophenol, 3-hydroxybenzenethiophenol, 2,5-dihydroxybenzenethiophenol, 2-hydroxybenzenesulfonic acid, 2,4-dihydroxybenzenesulfonic acid, or 2,4-dihydroxybenzenesulfonic acid.
[0014] Furthermore, the solvent in step (1) is methanol, benzene, acetonitrile, toluene, acetone, ethanol, diethyl ether, or carbon tetrachloride.
[0015] Furthermore, in step (2), A and B are mixed and placed in a reactor for reaction under microwave reaction conditions. The microwave power is 800-1200W, the reaction temperature is 100-200℃, the reaction time is 0.5-12h, and the reaction atmosphere is nitrogen.
[0016] Further, in step (3), the catalyst precursor obtained in step (2) is washed with a solvent and then transferred to a vacuum drying oven to dry and obtain the catalyst. The drying temperature is 100-200℃ and the drying time is 2-48h. The solvent is methanol, benzene, acetonitrile, toluene, acetone, ethanol, diethyl ether or carbon tetrachloride.
[0017] The present invention also provides the application of the sulfur- and phosphorus-based catalysts in the liquid-phase Beckmann rearrangement to caprolactam reaction, using cyclohexanone oxime as a raw material, to synthesize caprolactam under the catalysis of the sulfur- and phosphorus-based catalysts, with the cyclohexanone oxime conversion reaching 100% and the caprolactam selectivity reaching 99.5%.
[0018] Furthermore, cyclohexanone oxime and catalyst are added to a catalytic reactor, heated to 80-140℃, with a reaction pressure of 0.1KPa-1.0Kpa and a reaction time of 1-60 min; wherein the mass ratio of catalyst to cyclohexanone oxime is (1-50):50.
[0019] The beneficial effects of this invention are as follows: Upon heating in a specific solvent system, the chlorine atoms of phosphorus chloride undergo a condensation reaction with the hydroxyl groups in sulfur-containing organic compounds to generate phosphorus-sulfur compounds. Using cyclohexanone oxime as a raw material, caprolactam is synthesized under the catalysis of sulfur- and phosphorus-based catalysts. The solid catalyst is non-corrosive, produces no ammonium sulfate byproduct, the catalyst and product are easily separated, the maximum conversion rate of cyclohexanone oxime using the catalyst is 100%, and the maximum selectivity for caprolactam is 99.5%. Detailed Implementation
[0020] The present invention will be further described below with reference to specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make some non-essential improvements and adjustments based on the above-described invention.
[0021] Example 1
[0022] The preparation method of the sulfur- and phosphorus-based catalysts for the liquid-phase Beckmann rearrangement to caprolactam in this embodiment is as follows:
[0023] (1) First, 30g of phosphorus trichloride was dissolved in 70g of acetonitrile. The solution was prepared by stirring for 15min at a temperature of 30℃ and a stirring speed of 200r / min. Then, 30g of 4,4'-dihydroxydiphenyl sulfide was dissolved in 70g of acetonitrile and stirred for 15min at a temperature of 30℃ and a stirring speed of 200r / min to prepare solution B.
[0024] (2) Subsequently, under microwave reaction conditions of 800W microwave power and 120℃, A and B were mixed and placed in a reactor for microwave reaction for 0.5h to obtain catalyst precursor;
[0025] (3) The catalyst precursor obtained in step (2) was washed with ethanol and vacuum dried for 0.5 h at a vacuum drying temperature of 100 °C to obtain catalyst 1.
[0026] Catalyst evaluation
[0027] Cyclohexanone oxime and catalyst 1 were added to a catalytic reactor, heated to 140℃, and reacted for 30 min; the mass ratio of catalyst to cyclohexanone oxime was 1:1. The conversion rate of cyclohexanone oxime was 100%, and the selectivity of caprolactam was 99.0%.
[0028] Example 2
[0029] The preparation method of the sulfur- and phosphorus-based catalysts for the liquid-phase Beckmann rearrangement to caprolactam in this embodiment is as follows:
[0030] (1) First, 30g of phosphorus pentachloride was dissolved in 70g of acetonitrile. The solution was prepared by stirring for 15min at a temperature of 30℃ and a stirring speed of 200r / min. Then, 30g of 4,4'-dihydroxydiphenyl sulfide was dissolved in 70g of acetonitrile and stirred for 15min at a temperature of 30℃ and a stirring speed of 200r / min to prepare solution B.
[0031] (2) Subsequently, under microwave reaction conditions of 800W microwave power and 120℃, A and B were mixed and placed in a reactor for microwave reaction for 0.5h to obtain catalyst precursor;
[0032] (3) The catalyst precursor obtained in step (2) was washed with ethanol and vacuum dried for 0.5 h at a vacuum drying temperature of 100 °C to obtain catalyst 2.
[0033] Catalyst evaluation
[0034] Cyclohexanone oxime and catalyst 2 were added to a catalytic reactor, heated to 140℃, and reacted for 30 min; the mass ratio of catalyst to cyclohexanone oxime was 1:1. The conversion rate of cyclohexanone oxime was 99.7%, and the selectivity of caprolactam was 99.1%.
[0035] Example 3
[0036] The preparation method of the sulfur- and phosphorus-based catalysts for the liquid-phase Beckmann rearrangement to caprolactam in this embodiment is as follows:
[0037] (1) First, 30g of phosphorus trichloride was dissolved in 70g of acetonitrile. The solution was prepared by stirring for 15min at a temperature of 30℃ and a stirring speed of 200r / min. Then, 30g of thiol-polyethylene glycol-hydroxyl was dissolved in 70g of acetonitrile and stirred for 15min at a temperature of 30℃ and a stirring speed of 200r / min to prepare solution B.
[0038] (2) Subsequently, under microwave reaction conditions of 800W microwave power and 120℃, A and B were mixed and placed in a reactor for microwave reaction for 0.5h to obtain catalyst precursor;
[0039] (3) The catalyst precursor obtained in step (2) was washed with ethanol and vacuum dried for 0.5 h at a vacuum drying temperature of 100 °C to obtain catalyst 3.
[0040] Catalyst evaluation
[0041] Cyclohexanone oxime and catalyst 3 were added to a catalytic reactor, heated to 140℃, and reacted for 30 min; the mass ratio of catalyst to cyclohexanone oxime was 1:1. The conversion rate of cyclohexanone oxime was 99.8%, and the selectivity of caprolactam was 99.3%.
[0042] Example 4
[0043] The preparation method of the sulfur- and phosphorus-based catalysts for the liquid-phase Beckmann rearrangement to caprolactam in this embodiment is as follows:
[0044] (1) First, 30g of phosphorus pentachloride was dissolved in 70g of acetonitrile. The solution was prepared by stirring for 15min at a temperature of 30℃ and a stirring speed of 500r / min. Then, 30g of 2,4-dihydroxybenzenesulfonic acid was dissolved in 70g of acetonitrile and stirred for 15min at a temperature of 30℃ and a stirring speed of 500r / min to prepare solution B.
[0045] (2) Subsequently, under microwave reaction conditions of 800W microwave power and 120℃, A and B were mixed and placed in a reactor for microwave reaction for 0.5h to obtain catalyst precursor;
[0046] (3) The catalyst precursor obtained in step (2) was washed with ethanol and vacuum dried for 0.5 h at a vacuum drying temperature of 100 °C to obtain catalyst 4.
[0047] Catalyst evaluation
[0048] Cyclohexanone oxime and catalyst 4 were added to a catalytic reactor, heated to 140℃, and reacted for 30 min; the mass ratio of catalyst to cyclohexanone oxime was 1:1. The conversion rate of cyclohexanone oxime was 99.7%, and the selectivity of caprolactam was 99.5%.
[0049] Example 5
[0050] The preparation method of the sulfur- and phosphorus-based catalysts for the liquid-phase Beckmann rearrangement to caprolactam in this embodiment is as follows:
[0051] (1) First, 25g of phosphorus trichloride was dissolved in 70g of acetonitrile. The solution was stirred for 15min at 30℃ and 500r / min to obtain solution A. Then, 25g of 3,3'-dihydroxydiphenyl disulfide was dissolved in 70g of acetonitrile and stirred for 15min at 30℃ and 500r / min to obtain solution B.
[0052] (2) Subsequently, under microwave reaction conditions of 1200W microwave power and 200℃ reaction temperature, A and B were mixed and placed in a reactor for microwave reaction for 0.5h to obtain catalyst precursor;
[0053] (3) The catalyst precursor obtained in step (2) was washed with ethanol and vacuum dried for 0.5 h at a vacuum drying temperature of 100 °C to obtain catalyst 5.
[0054] Catalyst evaluation
[0055] Cyclohexanone oxime and catalyst 5 were added to a catalytic reactor, heated to 140℃, and reacted for 30 min; the mass ratio of catalyst 5 to cyclohexanone oxime was 1:1. The conversion rate of cyclohexanone oxime was 99.3%, and the selectivity of caprolactam was 99.0%.
[0056] Example 6
[0057] The preparation method of the sulfur- and phosphorus-based catalysts for the liquid-phase Beckmann rearrangement to caprolactam in this embodiment is as follows:
[0058] (1) First, 15g of phosphorus pentachloride was dissolved in 70g of acetonitrile. The solution was prepared by stirring for 15min at a temperature of 30℃ and a stirring speed of 500r / min. Then, 15g of 2,4-dihydroxybenzenesulfonic acid was dissolved in 70g of acetonitrile and stirred for 15min at a temperature of 30℃ and a stirring speed of 500r / min to prepare solution B.
[0059] (2) Subsequently, under microwave reaction conditions of 800W microwave power and 120℃, A and B were mixed and placed in a reactor for microwave reaction for 0.5h to obtain catalyst precursor;
[0060] (3) The catalyst precursor obtained in step (2) was washed with ethanol and vacuum dried for 0.5 h at a vacuum drying temperature of 100 °C to obtain catalyst 6.
[0061] Catalyst evaluation
[0062] Cyclohexanone oxime and catalyst 6 were added to a catalytic reactor, heated to 140℃, and reacted for 30 min; the mass ratio of catalyst to cyclohexanone oxime was 1:1. The conversion rate of cyclohexanone oxime was 99.6%, and the selectivity of caprolactam was 99.4%.
[0063] Example 7
[0064] The preparation method of the sulfur- and phosphorus-based catalysts for the liquid-phase Beckmann rearrangement to caprolactam in this embodiment is as follows:
[0065] (1) First, 10g of phosphorus pentachloride was dissolved in 70g of acetonitrile. The solution was prepared by stirring for 60min at a temperature of 30℃ and a stirring speed of 500r / min. Then, 30g of 2,4-dihydroxybenzenesulfonic acid was dissolved in 70g of acetonitrile and stirred for 15min at a temperature of 30℃ and a stirring speed of 500r / min to prepare solution B.
[0066] (2) Subsequently, under microwave reaction conditions of 800W microwave power and 140℃, A and B were mixed and placed in a reactor for microwave reaction for 0.5h to obtain catalyst precursor;
[0067] (3) The catalyst precursor obtained in step (2) was washed with ethanol and then vacuum dried for 120 h at a vacuum drying temperature of 120 °C to obtain catalyst 7.
[0068] Catalyst evaluation
[0069] Cyclohexanone oxime and catalyst 7 were added to a catalytic reactor, heated to 140℃, and reacted for 60 min; the mass ratio of catalyst to cyclohexanone oxime was 1:1. The conversion rate of cyclohexanone oxime was 98.9%, and the selectivity of caprolactam was 98.8%.
[0070] Example 8
[0071] The preparation method of the sulfur- and phosphorus-based catalysts for the liquid-phase Beckmann rearrangement to caprolactam in this embodiment is as follows:
[0072] (1) First, 20g of phosphorus pentachloride was dissolved in 70g of acetonitrile. The solution was prepared by stirring for 60min at a temperature of 30℃ and a stirring speed of 500r / min. Then, 30g of 2,5-dihydroxythiophenol was dissolved in 70g of acetonitrile and stirred for 15min at a temperature of 30℃ and a stirring speed of 500r / min to prepare solution B.
[0073] (2) Subsequently, under microwave reaction conditions of 800W microwave power and 120℃, A and B were mixed and placed in a reactor for microwave reaction for 0.5h to obtain catalyst precursor;
[0074] (3) The catalyst precursor obtained in step (2) was washed with ethanol and vacuum dried for 0.5 h at a vacuum drying temperature of 120 °C to obtain catalyst 8.
[0075] Catalyst evaluation
[0076] Cyclohexanone oxime and catalyst 8 were added to a catalytic reactor, heated to 130℃, and reacted for 60 min; the mass ratio of catalyst to cyclohexanone oxime was 1:1. The conversion rate of cyclohexanone oxime was 99.4%, and the selectivity of caprolactam was 99.1%.
[0077] Example 9
[0078] The preparation method of the sulfur- and phosphorus-based catalysts for the liquid-phase Beckmann rearrangement to caprolactam in this embodiment is as follows:
[0079] (1) First, 30g of phosphorus pentachloride was dissolved in 70g of acetonitrile. The solution was prepared by stirring for 60min at a temperature of 30℃ and a stirring speed of 500r / min. Then, 30g of dihydroxydiphenyl sulfide was dissolved in 70g of acetonitrile and stirred for 15min at a temperature of 30℃ and a stirring speed of 500r / min to prepare solution B.
[0080] (2) Subsequently, under microwave reaction conditions of 800W microwave power and 120℃, A and B were mixed and placed in a reactor for microwave reaction for 0.5h to obtain catalyst precursor;
[0081] (3) The catalyst precursor obtained in step (2) was washed with ethanol and vacuum dried for 0.5 h at a vacuum drying temperature of 100 °C to obtain 9.
[0082] Catalyst evaluation
[0083] Cyclohexanone oxime and catalyst 9 were added to a catalytic reactor, heated to 120°C, and reacted for 30 min; the mass ratio of catalyst to cyclohexanone oxime was 1:1. The conversion rate of cyclohexanone oxime was 99.1%, and the selectivity of caprolactam was 99.1%.
[0084] Example 10
[0085] The preparation method of the sulfur- and phosphorus-based catalysts for the liquid-phase Beckmann rearrangement to caprolactam in this embodiment is as follows:
[0086] (1) First, 30g of phosphorus pentachloride was dissolved in 70g of carbon tetrachloride and stirred for 15min at 30℃ and 500r / min to obtain solution A. Then, 30g of 2,4-dihydroxybenzenesulfonic acid was dissolved in 70g of carbon tetrachloride and stirred for 15min at 30℃ and 500r / min to obtain solution B.
[0087] (2) Subsequently, under microwave reaction conditions of 1200W microwave power and 120℃ reaction temperature, A and B were mixed and placed in a reactor for microwave reaction for 0.5h to obtain catalyst precursor;
[0088] (3) The catalyst precursor obtained in step (2) was washed with ethanol and vacuum dried for 0.5 h at a vacuum drying temperature of 100 °C to obtain catalyst 10.
[0089] Catalyst evaluation
[0090] Cyclohexanone oxime and catalyst 10 were added to a catalytic reactor, heated to 140℃, and reacted for 60 min; the mass ratio of catalyst to cyclohexanone oxime was 1:1. The conversion rate of cyclohexanone oxime was 98.8%, and the selectivity of caprolactam was 99.4%.
[0091]
[0092] The foregoing has shown and described the basic principles and main features of the present invention, as well as its advantages. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.
Claims
1. A method for preparing a sulfur- and phosphorus-based catalyst for the liquid-phase Beckmann rearrangement to caprolactam, characterized in that, Includes the following steps: (1) Under certain reaction conditions, phosphorus chloride is first weighed and dissolved in a solvent to prepare solution A, and then sulfur-containing organic compounds are dissolved in a solvent to prepare solution B; (2) Under microwave reaction conditions, solution A and solution B are mixed and placed in a reactor to react and obtain a catalyst precursor; (3) The catalyst precursor obtained in step (2) is washed with solvent and dried under vacuum to obtain a sulfur- and phosphorus-based catalyst for the preparation of caprolactam by the liquid phase Beckmann rearrangement. The solvent in step (1) is carbon tetrachloride; In step (2), the microwave power is 800-1200W, the reaction temperature is 120-140℃, the reaction time is 0.5h, and the reaction atmosphere is nitrogen. The phosphorus chloride in step (1) is phosphorus trichloride or phosphorus pentachloride. The sulfur-containing organic compound in step (1) is 4,4'-dihydroxydiphenyl sulfide, 3,3'-dihydroxydiphenyl disulfide, thiol-polyethylene glycol-hydroxy, 4-hydroxybenzylthiophenol, 2-hydroxybenzylthiophenol, 3-hydroxybenzylthiophenol, 2,5-dihydroxybenzylthiophenol, 2-hydroxybenzylsulfonic acid, or 2,4-dihydroxybenzylsulfonic acid.
2. The method for preparing a sulfur- and phosphorus-based catalyst for the liquid-phase Beckmann rearrangement to caprolactam according to claim 1, characterized in that: In step (1), phosphorus chloride is dissolved in a solvent and placed in an open beaker for magnetic stirring to obtain solution A. Then, sulfur-containing organic matter is dissolved in a solvent and placed in an open beaker for magnetic stirring to obtain solution B. The stirring temperature is 20-40℃, the stirring speed is 200-500r / min, and the stirring time is 15min-60min. The mass ratio of phosphorus chloride to solvent is (1-3):7, and the mass ratio of sulfur-containing organic matter to solvent is (1-3):
7.
3. The method for preparing a sulfur- and phosphorus-based catalyst for the liquid-phase Beckmann rearrangement to caprolactam according to claim 1, characterized in that: In step (3), the catalyst precursor obtained in step (2) is washed with a solvent and then transferred to a vacuum drying oven to dry and obtain the catalyst. The drying temperature is 100-200℃ and the drying time is 2-48h. The solvent is methanol, benzene, acetonitrile, toluene, acetone, ethanol, diethyl ether or carbon tetrachloride.
4. The application of the sulfur- and phosphorus-based catalyst prepared by any one of claims 1-3 in the liquid-phase Beckmann rearrangement to caprolactam reaction, characterized in that, Caprolactam was synthesized from cyclohexanone oxime under the catalysis of sulfur- and phosphorus-based catalysts.