A method for the preparation of a catalyst for the aminolysis of caprolactam

Abstract

The present application relates to a kind of preparation methods for caprolactam ammonolysis catalyst, the present application provides a kind of preparation methods for caprolactam ammonolysis catalyst, the method with carbon molecular sieve as main carrier, by impregnation method, active component is loaded on carrier, then by acid treatment process to obtain target catalyst.The catalyst can make the conversion rate of caprolactam reach more than 80% in the catalytic caprolactam ammonolysis reaction, and the selectivity of product reaches more than 99%.At the same time, carbon molecular sieve is used as carrier, can adsorb part of the recombination component generated in the reaction process, improve the purity of 6-aminocapronitrile in product, reduce separation energy consumption.

Description

Technical Field

[0001] This invention pertains to methods for synthesizing organic compounds, and relates to a method for preparing a catalyst for the ammonolysis of caprolactam. Background Technology

[0002] Hexamethylenediamine (HDMA) is a strongly basic organic diamine. As an important chemical intermediate, it can be used to produce polyhexamethylene adipamide (Nylon 66) and hexamethylene sebacate (Nylon 610), which are then used to manufacture various nylon fibers, nylon resins, and engineering plastics. According to the research report "Global Hexamethylenediamine Industry Overall Scale, Domestic and International Market Share and Ranking of Major Enterprises in 2023," the global market sales of HDMA reached 47.4 billion yuan in 2022 and are projected to reach 68.1 billion yuan in 2029, with a compound annual growth rate (CAGR) of 5.0% (2023-2029). The traditional method for preparing HDMA involves the catalytic hydrogenation of adiponitrile, a method currently used by most large-scale HDMA producers. To avoid using the raw material HDMA, some manufacturers prepare HDMA through the hydrogenation reduction of 6-aminohexanonitrile. The raw material 6-aminohexanonitrile can be obtained through the ammonolysis of caprolactam, which is widely available. Therefore, caprolactam ammonolysis catalysts have become a research hotspot in the field.

[0003] Patent document CN111672526A discloses a method for preparing a catalyst for the synthesis of the hexamethylenediamine intermediate 6-aminohexanonitrile. This catalyst is obtained by mixing a support, binder, water, and a solvent, followed by molding, calcination, modification, and further calcination. Patent document CN114643068A discloses a method for preparing a catalyst for the amination of caprolactam to 6-aminohexanonitrile. This catalyst uses an aluminum compound as a support, mixed with a binder and solvent, then blended with a modifier solution, extruded, and calcined to obtain the catalyst. Patent document CN113402418A discloses a method for preparing 6-aminohexanonitrile. This method uses phosphoric acid or phosphate as a direct catalyst to catalyze the reaction of caprolactam and ammonia to prepare 6-aminohexanonitrile. Patent document CN116265084A discloses a catalyst for the amination of caprolactam to 6-aminohexanonitrile. This catalyst, obtained by adjusting the aluminum source, additive ratio, and crystallization time, yields a porous γ-Al₂O₃ catalyst. The above preparation method focuses on improving the conversion rate of caprolactam, while neglecting the purity of the product 6-aminohexanonitrile. The obtained 6-aminohexanonitrile needs to be further purified before it can be used to prepare hexamethylenediamine. Summary of the Invention

[0004] To address the technical problems existing in the prior art, this invention provides a method for preparing a catalyst for caprolactam ammonolysis. After acid treatment, the molecular sieve has more acidic sites, which increases its activity. The molecular sieve support is a carbon molecular sieve, which can adsorb some of the heavy components generated during the reaction, thereby increasing the purity of 6-aminehexanonitrile in the product and reducing separation energy consumption.

[0005] The technical solution adopted in this invention is: a method for preparing a catalyst for caprolactam ammonolysis, comprising the following steps: (1) The active component is loaded onto the support by impregnation to obtain catalyst A; (2) In an inert gas atmosphere, catalyst A is heat-treated at 600~800 ℃ for 4~20 h to obtain catalyst B; (3) The catalyst B is acid-treated with hydrochloric acid or nitric acid with a mass concentration of 5-35% at 30-80℃ for 0.5-6 h. The acid treatment step is repeated 1-5 times. After filtration and drying in an inert gas atmosphere, the catalyst C is obtained. (4) In an inert gas atmosphere, catalyst C is heat-treated at 500~600 ℃ for 3~12 h to obtain target catalyst D; The carrier is a carbon molecular sieve or a mixture of a carbon molecular sieve and at least one of pure silicon, pure aluminum, or silicon-aluminum molecular sieves; The active component is one or more of borates, phosphates, and pyrophosphates.

[0006] Some specific methods for preparing caprolactam ammonolysis catalysts, wherein when the support is a mixture, the mass fraction of carbon molecular sieve in the mixture is 60-100%.

[0007] Some specific methods for preparing catalysts for caprolactam ammonolysis are characterized in that the support is a carbon molecular sieve and the active component is a borate.

[0008] Some specific methods for preparing catalysts for caprolactam ammonolysis are characterized by the following: the mass ratio of active component to support is 0.1~0.3:1; the concentration range of hydrochloric acid is 0.1~5.0 mol / L; the concentration range of nitric acid is 1~12 mol / L; the acid treatment time is 1~6 h; and the volume of acid is 20~40 times the volume of catalyst B.

[0009] Some specific methods for preparing catalysts for caprolactam ammonolysis are characterized in that the mass ratio of the active component to the support is 0.15~0.25:1, and the volume of hydrochloric acid or nitric acid is 25~35 times the volume of catalyst B.

[0010] Some specific methods for preparing catalysts for caprolactam ammonolysis are characterized in that the inert gas is one or more of nitrogen, argon, and helium.

[0011] Some specific methods for preparing catalysts for caprolactam ammonolysis are characterized in that the feeding method in the acid treatment process is preferably bottom-in and top-out.

[0012] The catalyst prepared by the method described above for preparing caprolactam ammonolysis catalyst.

[0013] The beneficial effects of this invention are as follows: This invention provides a method for preparing a catalyst for caprolactam ammonolysis. The method uses carbon molecular sieves as the main support, loads the active component onto the support via impregnation, and then obtains the target catalyst through an acid treatment process. In the catalytic ammonolysis reaction of caprolactam, this catalyst can achieve a caprolactam conversion rate of over 80%, a product selectivity of over 90%, and simultaneously improve the purity of the product. Detailed Implementation

[0014] The present invention will be described in detail below with reference to specific embodiments. Unless otherwise specified, all raw materials and reagents used in the embodiments are commercially available chemical raw materials and reagents. The carbon molecular sieve conforms to the HG / T 4364-2020 standard, the pure silicon molecular sieve is synthesized according to Example 4 of Patent 201910340428.3, and the alumina is purchased from Sasol.

[0015] Example 1: 180 g of carbon molecular sieve was added to 400 ml of a 10% sodium borate aqueous solution and impregnated at room temperature for 1.5 h. After filtration, washing with water, and drying at 60 °C, catalyst A1 was obtained. Catalyst A1 was placed in a calcining furnace and heat-treated at 700 °C for 8 h in an argon atmosphere to obtain catalyst B1. Catalyst B1 was then added to 7.5 L of a 3 mol / L hydrochloric acid solution and heated to 50 °C for acid treatment for 3 h. After a total of 3 treatments, the solution was filtered, washed with water, and dried at 60 °C in an argon atmosphere to obtain catalyst C1. Catalyst C1 was heat-treated at 550 °C for 5 h in a calcining furnace to obtain the target catalyst D1.

[0016] Example 2: 180 g of carbon molecular sieve was added to 400 ml of a 10% sodium borate aqueous solution and impregnated at room temperature for 2.0 h. After filtration, washing with water, and drying at 60 °C, catalyst A2 was obtained. Catalyst A2 was placed in a calcining furnace and heat-treated at 600 °C for 18 h in an argon atmosphere to obtain catalyst B2. Catalyst B2 was then added to 9 L of a 3 mol / L hydrochloric acid solution and heated to 35 °C for acid treatment for 5 h. After a total of 3 treatments, the solution was filtered, washed with water, and dried at 65 °C in an argon atmosphere to obtain catalyst C2. Catalyst C2 was heat-treated at 600 °C for 3 h in a calcining furnace to obtain the target catalyst D2.

[0017] Example 3: 180 g of carbon molecular sieve was added to 400 ml of a 5% sodium borate aqueous solution and impregnated at room temperature for 3 h. After filtration, washing with water, and drying at 60 °C, catalyst A3 was obtained. Catalyst A3 was placed in a calcining furnace and heat-treated at 800 °C for 5 h in an argon atmosphere to obtain catalyst B3. Catalyst B3 was then added to 9 L of a 3 mol / L hydrochloric acid solution and heated to 65 °C for acid treatment for 1 h. After a total of 3 treatments, the solution was filtered, washed with water, and dried at 60 °C in an argon atmosphere to obtain catalyst C3. Catalyst C3 was heat-treated at 500 °C for 11 h in a calcining furnace to obtain the target catalyst D3.

[0018] Example 4: 180 g of carbon molecular sieve was added to 400 ml of a 20% sodium borate aqueous solution and impregnated at room temperature for 2 h. After filtration, washing with water, and drying at 60 °C, catalyst A4 was obtained. Catalyst A4 was placed in a calcining furnace and heat-treated at 670 °C for 10 h in an argon atmosphere to obtain catalyst B4. Catalyst B4 was then added to 10.8 L of a 3 mol / L hydrochloric acid solution and heated to 80 °C for acid treatment for 4 h. After a total of 3 treatments, the solution was filtered, washed with water, and dried at 60 °C in an argon atmosphere to obtain catalyst C4. Catalyst C4 was heat-treated at 550 °C for 5 h in a calcining furnace to obtain the target catalyst D4.

[0019] Example 5: 180 g of carbon molecular sieve was added to 400 ml of a 15% sodium borate aqueous solution and impregnated at room temperature for 10 h. After filtration, washing with water, and drying at 60 °C, catalyst A5 was obtained. Catalyst A5 was placed in a calcining furnace and heat-treated at 700 °C for 4 h in an argon atmosphere to obtain catalyst B5. Catalyst B5 was then added to 9 L of a 3 mol / L hydrochloric acid solution and heated to 30 °C for acid treatment for 1 h. After a total of 3 treatments, the solution was filtered, washed with water, and dried at 60 °C in an argon atmosphere to obtain catalyst C5. Catalyst C5 was heat-treated at 600 °C for 7 h in a calcining furnace to obtain the target catalyst D5.

[0020] Example 6: 180 g of carbon molecular sieve was added to 400 ml of a 10% sodium pyrophosphate aqueous solution and impregnated at room temperature for 1.5 h. After filtration, washing with water, and drying at 60 °C, catalyst A6 was obtained. Catalyst A6 was placed in a calcining furnace and heat-treated at 700 °C for 8 h in an argon atmosphere to obtain catalyst B6. Catalyst B6 was then added to 9 L of a 3 mol / L hydrochloric acid solution and heated to 50 °C for acid treatment for 3 h. After filtration, washing with water, and drying at 60 °C in an argon atmosphere, catalyst C6 was obtained. Catalyst C6 was heat-treated at 550 °C for 5 h in a calcining furnace to obtain the target catalyst D6.

[0021] Example 7: 130 g of carbon molecular sieve and 50 g of pure silicon molecular sieve were mechanically extruded into cylinders with a diameter of 3 mm and a length of 15-20 mm. These cylinders were added to 400 ml of a 10% (w / w) sodium borate aqueous solution and impregnated at room temperature for 1.5 h. After filtration, washing with water, and drying at 60 °C, catalyst A7 was obtained. Catalyst A7 was placed in a calcining furnace and heat-treated at 700 °C for 8 h in an argon atmosphere to obtain catalyst B7. Catalyst B7 was then added to 9 L of a 3 mol / L hydrochloric acid solution and heated to 50 °C for acid treatment for 3 h. This treatment was repeated three times. After filtration, washing with water, and drying at 60 °C in an argon atmosphere, catalyst C7 was obtained. Catalyst C7 was heat-treated at 550 °C for 5 h in a calcining furnace to obtain the target catalyst D7.

[0022] Example 8: 150 g of carbon molecular sieve and 30 g of pure silicon molecular sieve were mechanically extruded into cylinders with a diameter of 3 mm and a length of 15-20 mm. These cylinders were added to 400 ml of a 10% (w / w) sodium borate aqueous solution and impregnated at room temperature for 1.5 h. After filtration, washing with water, and drying at 60 °C, catalyst A8 was obtained. Catalyst A8 was placed in a calcining furnace and heat-treated at 700 °C for 8 h in an argon atmosphere to obtain catalyst B8. Catalyst B8 was then added to 9 L of a 3 mol / L hydrochloric acid solution and heated to 50 °C for acid treatment for 3 h. After filtration, washing with water, and drying at 60 °C in an argon atmosphere, catalyst C8 was obtained. Catalyst C8 was heat-treated at 550 °C for 5 h in a calcining furnace to obtain the target catalyst D8.

[0023] Example 9: 150 g of carbon molecular sieve and 30 g of alumina were mechanically extruded into cylinders with a diameter of 3 mm and a length of 15-20 mm. These cylinders were then added to 400 ml of a 10% (w / w) sodium borate aqueous solution and impregnated at room temperature for 1.5 h. After filtration, washing with water, and drying at 60 °C, catalyst A9 was obtained. Catalyst A9 was placed in a calcining furnace and heat-treated at 600 °C for 8 h in an argon atmosphere to obtain catalyst B9. Catalyst B9 was then added to 9 L of a 3 mol / L hydrochloric acid solution and heated to 50 °C for acid treatment for 3 h. After filtration, washing with water, and drying at 60 °C in an argon atmosphere, catalyst C9 was obtained. Catalyst C9 was heat-treated at 550 °C for 5 h in a calcining furnace to obtain the target catalyst D9.

[0024] Comparative Example 1: 180g of alumina was mechanically extruded into cylinders with a diameter of 3mm and a length of 15-20mm. These cylinders were added to 400ml of a 10% sodium borate aqueous solution and impregnated at room temperature for 1.5h. After filtration, washing with water, and drying at 60℃, catalyst A'1 was obtained. Catalyst A'1 was placed in a calcining furnace and heat-treated at 700℃ for 8h under an argon atmosphere to obtain catalyst B'1. Catalyst B'1 was then added to 9L of a 3mol / L hydrochloric acid solution and heated to 50℃ for acid treatment for 3h. This treatment was repeated three times. After filtration, washing with water, and drying at 60℃ under an argon atmosphere, catalyst C'1 was obtained. Catalyst C'1 was then heat-treated at 550℃ for 5h in a calcining furnace to obtain the target catalyst D'1.

[0025] Comparative Example 2: 180g of silica was mechanically extruded into cylinders with a diameter of 3mm and a length of 15-20mm. These cylinders were added to 400ml of a 10% sodium borate aqueous solution and impregnated at room temperature for 1.5h. After filtration, washing with water, and drying at 60℃, catalyst A'2 was obtained. Catalyst A'2 was placed in a calcining furnace and heat-treated at 700℃ for 8h under an argon atmosphere to obtain catalyst B'2. Catalyst B'2 was then added to 9L of a 3mol / L hydrochloric acid solution and heated to 50℃ for acid treatment for 3h. This treatment was repeated three times. After filtration, washing with water, and drying at 60℃ under an argon atmosphere, catalyst C'2 was obtained. Catalyst C'2 was then heat-treated at 550℃ for 5h in a calcining furnace to obtain the target catalyst D'2.

[0026] Test Example: Evaluation of the Catalytic Performance of the Catalyst for Caprolactam Ammonolysis The catalysts prepared in the examples and comparative examples were used to evaluate the fixed-bed caprolactam ammonolysis reaction. 50 g of catalyst was packed into a fixed bed, the temperature was raised to 400 °C, and caprolactam was released at a mass hourly space velocity (WHSV) of 0.5 h⁻¹. -1 The feed consisted of ammonia / caprolactam at a molar ratio of 30. Liquid 6-aminohexanonitrile was collected and sampled for control. Mass balance calculations were performed to obtain the conversion rate of caprolactam and the selectivity of the product 6-aminohexanonitrile. Simultaneously, liquid chromatography was used to determine the purity of the product 6-aminohexanonitrile. Specific data are shown in Table 1.

[0027] Table 1 Evaluation data of caprolactam ammonolysis catalyzed by catalysts in the examples and comparative examples. D1 82.70% 99.60% 99.80% D2 82.40% 99.50% 99.70% D3 82.20% 99.45% 99.50% D4 84.30% 99.40% 99.60% D5 83.10% 99.50% 99.55% D6 81.2% 99.05% 99.20% D7 81.30% 99.30% 99.25% D8 81.80% 99.40% 99.40% D9 81.50% 99.30% 99.30% D’1 80.80% 99.00% 99.00% D’2 80.90% 99.05% 99.05% The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a catalyst for caprolactam ammonolysis, characterized in that, The method includes the following steps: (1) The active component is loaded onto the support by impregnation to obtain catalyst A; (2) In an inert gas atmosphere, catalyst A is heat-treated at 600~800 ℃ for 4~20 h to obtain catalyst B; (3) The catalyst B is acid-treated with hydrochloric acid or nitric acid with a mass concentration of 5-35% at 30-80℃ for 0.5-6 h. The acid treatment step is repeated 1-5 times. After filtration and drying in an inert gas atmosphere, the catalyst C is obtained. (4) In an inert gas atmosphere, catalyst C is heat-treated at 500~600 ℃ for 3~12 h to obtain target catalyst D; The carrier is a carbon molecular sieve or a mixture of a carbon molecular sieve and at least one of pure silicon, pure aluminum, or silicon-aluminum molecular sieves; The active component is one or more of borates, phosphates, and pyrophosphates; The mass ratio of the active component to the support is 0.1~0.3:1, and the volume of hydrochloric acid or nitric acid is 20~40 times the volume of catalyst B.

2. The method for preparing the caprolactam ammonolysis catalyst according to claim 1, characterized in that, When the carrier is a mixture, the mass fraction of carbon molecular sieve in the mixture is 60~100%.

3. The method for preparing the caprolactam ammonolysis catalyst according to claim 1, characterized in that, The carrier is a carbon molecular sieve, and the active component is a borate.

4. The method for preparing the caprolactam ammonolysis catalyst according to claim 1, characterized in that, The mass ratio of the active component to the support is 0.15~0.25:1, and the volume of hydrochloric acid or nitric acid is 25~35 times the volume of catalyst B.

5. The method for preparing the caprolactam ammonolysis catalyst according to claim 4, characterized in that, The concentration of hydrochloric acid is 0.1~5.0 mol / L, the concentration of nitric acid is 1~12 mol / L, and the duration of each acid treatment is 1~6 h.

6. The method for preparing a caprolactam ammonolysis catalyst according to any one of claims 1-3, characterized in that: The inert gas is one or more of argon and helium.

7. The method for preparing a caprolactam ammonolysis catalyst according to any one of claims 1-3, characterized in that: The acid treatment process uses a bottom-in, top-out feeding method.

8. The catalyst prepared by the method for preparing caprolactam ammonolysis catalyst according to any one of claims 1-3.