Synthesis method of 6-aminocapronitrile

Abstract

The present invention provides a method for efficiently synthesizing 6-aminocapronitrile, a key intermediate of hexamethylenediamine, wherein a molten caprolactam feed is reacted with ammonia gas, and an Ag / SiO 2 The catalyst is an amination catalyst. The process is simple and easy to operate, the reaction temperature is low, and the reaction conversion rate and selectivity are high.

Description

Technical Field

[0001] The invention relates to a 6-aminocapronitrile method and belongs to the field of fine chemicals. Background Art

[0002] 6-aminocapronitrile is an important chemical intermediate that can be used to produce 1,6-hexanediamine through hydrogenation reaction. Hexanediamine is an important raw material for the production of polyamide 66 (PA66), PA610, HDI (1,6-hexanediisocyanate) and other products. Internationally, the production of hexanediamine is mainly monopolized by some large multinational companies, and the production is very concentrated. INVISTA, BASF and Ascend together account for 74% of the global production capacity and are in a highly oligopolistic industry. At present, the preparation of 6-aminocapronitrile is mainly obtained by partial hydrogenation of 1,6-adiponitrile. For example, CN105921164B provides a preparation method and application of a nickel-based catalyst modified by alkali metal supported by nitrogen-doped activated carbon, which can have high activity and high total selectivity of 6-aminocapronitrile and hexanediamine under relatively mild reaction conditions when used in the adiponitrile hydrogenation process.

[0003] In 1965, Toray of Japan realized the industrialization of producing hexamethylenediamine from caprolactam, which was mainly used to recycle waste raw materials such as recycled caprolactam or waste nylon. The key to this process is that caprolactam and ammonia generate aminocapronitrile under the action of a catalyst.

[0004] .

[0005] This process has also been studied in China. Patent CN107602416A provides a method for preparing 6-aminocapronitrile by a vapor phase method, wherein caprolactam vapor and hot ammonia are mixed in a certain mass ratio in the presence of a catalyst to carry out an ammonia dehydration reaction, and the product is separated and purified to obtain pure 6-aminocapronitrile. The catalyst is one or more of an alkaline earth metal oxide, a transition metal oxide, silicon dioxide and activated alumina.

[0006] CN107739318A provides a method and device for preparing 6-aminocapronitrile by a caprolactam liquid phase method, wherein caprolactam, an organic solvent and a catalyst are mixed in a certain mass ratio to obtain a mixed solution, the mixed solution is added to a reactor and stirred and heated to a certain temperature, ammonia is introduced into the mixed solution to react, and after the reaction is completed, the reaction product is distilled and purified to obtain pure 6-aminocapronitrile.

[0007] CN110404582A discloses a method for preparing a catalyst for the amination of caprolactam, wherein a phosphorus aluminum molecular sieve is used as a carrier, a certain amount of active components of magnesium nitrate, aluminum nitrate and nickel nitrate are loaded by an impregnation method at a certain temperature, and an amination dehydration catalyst is obtained after drying, molding and roasting. The catalyst is loaded in a fixed bed, and caprolactam and ammonia are reacted under the conditions of 420-500°C and 0-1 MPa. The catalyst obtained by this method is simple to prepare, the conversion rate of caprolactam is greater than 80%, and the selectivity of 6-aminocapronitrile is greater than 99%.

[0008] CN111004148A measures caprolactam and ammonia in a molar ratio of 1:3-1:20, preheats them respectively, mixes them and further heats them to obtain a mixture, puts the mixture into a reactor, and carries out an amination dehydration reaction in the presence of a catalyst to obtain an amination reactant, wherein the catalyst is composed of an alkaline earth metal salt or a transition metal salt as an active component and titanium dioxide or a ZSM-5 molecular sieve as a carrier, and finally separates and purifies to obtain the target product 6-aminocapronitrile.

[0009] There is no industrialized case of related technology in China. Due to the high price of caprolactam, the current process of producing hexamethylenediamine from caprolactam does not have an advantage. With the gradual commissioning of caprolactam plants within Sinopec and the industry, the price of caprolactam is bound to fall in the future. Using Sinopec's own sufficient caprolactam raw materials to produce hexamethylenediamine makes it possible to industrialize the synthesis of hexamethylenediamine from caprolactam on a large scale. Summary of the invention

[0010] The object of the present invention is to provide a method for synthesizing 6-aminocapronitrile.

[0011] A synthesis process of 6-aminocapronitrile, the main process steps comprising: caprolactam and ammonia gas enter a fixed bed reactor in a certain ratio, and under certain reaction conditions and the action of a catalyst, ammonia dehydration reaction is continuously carried out to synthesize 6-aminocapronitrile.

[0012] .

[0013] To achieve the above purpose, the technical solution generally adopted by the present invention is as follows:

[0014] 1. The catalyst prepared by the impregnation method is Ag / SiO2 catalyst, the weight of Ag accounts for 1%~6% of the weight of the carrier SiO2, and the carrier SiO2 is a small ball with a particle size of 0.5mm-2mm. The catalyst preparation method is: the carrier SiO2 is hydrothermally treated at 160℃-200℃, and after drying, the AgNO3 calculated in proportion is loaded by the impregnation method, and after drying and calcination, the Ag2O / SiO2 catalyst is obtained, and its specific surface area is 40m 2 / g-60 m2 / g. The catalyst is filled into a fixed bed, and before the amination reaction, hydrogen or ammonia is used to reduce the Ag2O / SiO2 catalyst to convert it into an Ag / SiO2 catalyst.

[0015] 2. Caprolactam enters the preheater in a molten state and is vaporized. Ammonia and caprolactam are preheated and mixed in the preheater before entering the catalyst bed. The molar ratio of ammonia to caprolactam is 5-25, and the hourly space velocity of the reaction liquid (molten caprolactam feed rate / catalyst filling volume) is 0.1 h -1 -0.5h -1 The reaction temperature is controlled at 280°C-320°C, the reactor outlet is in a vented state, and the reaction pressure is normal pressure or slightly positive pressure.

[0016] 3. The receiving tank of the reaction product is fully cooled with 10℃-30℃ circulating water to fully liquefy the organic materials in the product and discharge the unreacted ammonia for treatment.

[0017] Beneficial effects of the present invention:

[0018] A 6-aminocapronitrile method is provided, wherein a caprolactam molten feed reacts with ammonia, and an Ag / SiO2 catalyst is used as an amination catalyst. The process is simple and easy to operate, the reaction temperature is low, and the reaction conversion rate and selectivity are both high. DETAILED DESCRIPTION

[0019] The present invention will be further described below in conjunction with specific embodiments.

[0020] Example 1

[0021] Catalyst preparation: 0.5 mm silicon pellets were hydrothermally treated at 160 °C and the Ag2O / SiO2 catalyst was prepared by impregnation. The weight of Ag accounts for 1% of the weight of the carrier SiO2. The specific surface area of ​​the catalyst is 60 m 2 After being loaded into a fixed bed reactor, the Ag2O / SiO2 catalyst is reduced with ammonia gas to convert it into an Ag / SiO2 catalyst suitable for amination reaction.

[0022] Amination reaction: the molar ratio of ammonia to caprolactam is 5, the reaction temperature is controlled at 280°C, and the hourly space velocity of the caprolactam feed liquid is 0.1h -1 , the cooling water of the receiving tank was 10°C. After 4 hours of reaction, the organic phase in the receiving tank was dissolved with acetonitrile, and the composition was analyzed by gas chromatography. The results showed that the material composition of the reaction product was: caprolactam 17.27%, 6-aminocapronitrile 76.89%, the conversion rate of amination reaction was 82.73%, and the selectivity of 6-aminocapronitrile reaction was 92.94%.

[0023] Example 2

[0024] Catalyst preparation: 1 mm silicon pellets, 180 ° C hydrothermal treatment, and impregnation method to prepare Ag2O / SiO2 catalyst, the weight of Ag accounts for 3% of the weight of the carrier SiO2. The specific surface area of ​​the catalyst is 54 m 2 After being loaded into a fixed bed reactor, the Ag2O / SiO2 catalyst is reduced with ammonia gas to convert it into an Ag / SiO2 catalyst suitable for amination reaction.

[0025] Amination reaction: the molar ratio of ammonia to caprolactam is 10, the reaction temperature is controlled at 300°C, and the hourly space velocity of the caprolactam feed liquid is 0.2h -1 , the cooling water of the receiving tank was 20°C. After 4 hours of reaction, the organic phase in the receiving tank was dissolved with acetonitrile, and the composition was analyzed by gas chromatography. The results showed that the material composition of the reaction product was: caprolactam 11.04%, 6-aminocapronitrile 87.50%, the conversion rate of amination reaction was 88.96%, and the selectivity of 6-aminocapronitrile reaction was 98.36%.

[0026] Example 3

[0027] Catalyst preparation: 2 mm silicon pellets, 180 ° C hydrothermal treatment, and impregnation method to prepare Ag2O / SiO2 catalyst, the weight of Ag accounts for 6% of the weight of the carrier SiO2. The specific surface area of ​​the catalyst is 57 m 2 After being loaded into a fixed bed reactor, the Ag2O / SiO2 catalyst is reduced with ammonia gas to convert it into an Ag / SiO2 catalyst suitable for amination reaction.

[0028] Amination reaction: the molar ratio of ammonia to caprolactam is 15, the reaction temperature is controlled at 320°C, and the hourly space velocity of the caprolactam feed liquid is 0.2h -1 , the cooling water of the receiving tank was 20°C. After 4 hours of reaction, the organic phase in the receiving tank was dissolved with acetonitrile, and the composition was analyzed by gas chromatography. The results showed that the material composition of the reaction product was: caprolactam 0.81%, 6-aminocapronitrile 98.47%, the conversion rate of amination reaction was 99.19%, and the selectivity of 6-aminocapronitrile reaction was 99.27%.

[0029] Example 4

[0030] Preparation of catalyst: The difference from Example 3 is that the hydrothermal treatment temperature is changed to 200°C and the specific surface area of ​​the catalyst is 42 m 2 / g.

[0031] Amination reaction: The reaction and analysis methods were the same as those in Example 3. The results showed that the material composition of the reaction product was: 0.93% caprolactam, 96.48% 6-aminocapronitrile, the amination reaction conversion rate was 99.07%, and the 6-aminocapronitrile reaction selectivity was 97.39%.

[0032] Example 4

[0033] Preparation of catalyst: The difference from Example 3 is that the Ag loading is adjusted to 1% and the specific surface area of ​​the catalyst is 55 m 2 / g.

[0034] Amination reaction: The reaction and analysis methods were the same as those in Example 3. The results showed that the material composition of the reaction product was: caprolactam 7.18%, 6-aminocapronitrile 92.02%, the amination reaction conversion rate was 92.82%, and the 6-aminocapronitrile reaction selectivity was 99.14%.

[0035] Example 5

[0036] Preparation of catalyst: Same as Example 3.

[0037] Amination reaction: The reaction conditions differ from those in Example 3 in that the hourly space velocity of the caprolactam feed liquid is 0.5 h -1 The remaining reaction and sampling analysis conditions were the same. The results showed that the material composition of the reaction product was: caprolactam 13.79%, 6-aminocapronitrile 86.15%, the amination reaction conversion rate was 86.21%, and the 6-aminocapronitrile reaction selectivity was 99.93%.

[0038] Example 6

[0039] Preparation of catalyst: Same as Example 3.

[0040] Amination reaction: The reaction conditions differ from those of Example 3 in that the amination reaction temperature was adjusted to 300° C., and the other reaction and sampling analysis conditions were the same. The results showed that the material composition of the reaction product was: 2.35% caprolactam, 97.15% 6-aminocapronitrile, the amination reaction conversion rate was 97.65%, and the 6-aminocapronitrile reaction selectivity was 99.49%.

[0041] Example 7

[0042] Preparation of catalyst: The difference from Example 2 is that the Ag loading is adjusted to 6% and the specific surface area of ​​the catalyst is 51m 2 / g.

[0043] Amination reaction: The reaction and analysis methods were the same as those in Example 3. The results showed that the material composition of the reaction product was: 5.33% caprolactam, 92.97% 6-aminocapronitrile, the amination reaction conversion rate was 94.67%, and the 6-aminocapronitrile reaction selectivity was 98.20%.

Claims

1. A method for synthesizing 6-aminocapronitrile, characterized in that: Caprolactam and ammonia enter a fixed bed reactor in proportion, and under the action of an Ag / SiO2 catalyst, an amination-dehydration reaction continuously occurs to synthesize 6-aminocapronitrile, specifically comprising the following steps: caprolactam enters a preheater in a molten state and is gasified, ammonia and caprolactam are preheated and mixed in the preheater, and then enter a catalyst bed; the catalyst is filled into a fixed bed, and before the amination reaction, the Ag2O / SiO2 catalyst is reduced by hydrogen or ammonia to convert it into an Ag / SiO2 catalyst; the catalyst preparation method comprises the following steps: the carrier SiO2 is subjected to a hydrothermal treatment at 160°C-200°C, and after drying, a proportionate amount of AgNO3 is loaded by an impregnation method, and the Ag2O / SiO2 catalyst is obtained after drying and calcination.

2. The method according to claim 1, characterized in that In the catalyst, the weight ratio of Ag to the weight ratio of the carrier SiO2 is 1% to 6%.

3. The method according to claim 1, characterized in that In the catalyst, the carrier SiO2 is a small ball with a particle size of 0.5mm-2mm.

4. The method according to claim 1, characterized in that The specific surface area of ​​the catalyst is 40 m 2 / g-60 m 2 / g.

5. The method according to claim 1, characterized in that The molar ratio of ammonia to caprolactam is 5-25, and the hourly space velocity of the reaction liquid, i.e., the molten caprolactam feed rate / catalyst filling volume, is 0.1 h -1 -0.5h -1 The reaction temperature is controlled at 280°C-320°C, the reactor outlet is in a vented state, and the reaction pressure is normal pressure or slightly positive pressure.

6. The method according to claim 1, characterized in that The receiving tank of the reaction product is fully cooled with 10℃-30℃ circulating water to fully liquefy the organic materials in the product and discharge the unreacted ammonia for treatment.