阅读说明：本技术 一种连续气相两步法生产己二胺关键中间体6-氨基己腈的方法 (Method for producing hexamethylene diamine key intermediate 6-aminocapronitrile by continuous gas phase two-step method ) 是由 王根林 徐林 丁克鸿 梅学赓 王铖 殷恒志 刘鑫 王鑫宇 郭博博 于 2020-06-10 设计创作，主要内容包括：本发明提供了一种连续气相两步法生产己二胺关键中间体6-氨基己腈的方法。该方法包括：步骤S1,将己内酰胺和水在气相状态下混合进行连续化水解或将己内酰胺和氨水在气相状态下混合进行连续化水解氨化反应,得到包含6-氨基己酸、6-氨基己酸铵盐和/或6-氨基己酰胺的第一产物体系；步骤S2,使第一产物体系与氨气进行连续化气相催化氨化和脱水反应,得到包含6-氨基己腈的第二产物体系。本发明专利从源头上减少了一步法工艺中反应产生的水促进原料己内酰胺发生聚合反应的问题,提高了氨基己腈的选择性；有效减少了反应器内己内酰胺的聚合、结焦导致的催化剂失活和压降升高的问题,提高了装置的稳定性,延长了催化剂的使用寿命。(The invention provides a method for producing a key intermediate 6-aminocapronitrile of hexamethylene diamine by a continuous gas-phase two-step method. The method comprises the following steps: step S1, mixing caprolactam and water in a gas phase state for continuous hydrolysis or mixing caprolactam and ammonia water in a gas phase state for continuous hydrolysis ammoniation reaction to obtain a first product system containing 6-aminocaproic acid, 6-aminocaproic acid ammonium salt and/or 6-aminocaproamide; and step S2, carrying out continuous gas-phase catalytic ammoniation and dehydration reaction on the first product system and ammonia gas to obtain a second product system containing 6-aminocapronitrile. The invention fundamentally reduces the problem that water generated by the reaction in the one-step process promotes the polymerization reaction of caprolactam serving as a raw material, and improves the selectivity of aminocapronitrile; effectively reduces the problems of catalyst deactivation and pressure drop increase caused by the polymerization and coking of caprolactam in the reactor, improves the stability of the device and prolongs the service life of the catalyst.)

1. A method for producing a key intermediate 6-aminocapronitrile of hexamethylene diamine by a continuous gas phase two-step method is characterized by comprising the following steps:

step S1, mixing caprolactam and water in a gas phase state for continuous hydrolysis or mixing caprolactam and ammonia water in a gas phase state for continuous hydrolysis ammoniation reaction to obtain a first product system containing 6-aminocaproic acid, 6-aminocaproic acid ammonium salt and/or 6-aminocaproamide;

and step S2, carrying out continuous gas-phase catalytic ammoniation and dehydration reaction on the first product system and ammonia gas to obtain a second product system containing 6-aminocapronitrile.

2. The method according to claim 1, wherein the step S1 comprises atomizing the caprolactam and mixing the atomized caprolactam with preheated water or preheated ammonia water, wherein the preheated temperature of the water or the ammonia water is 300-500 ℃.

3. The method of claim 1, wherein the ammonia water is NH₃The mass content of (A) is 1-50%, and the mass ratio of the caprolactam to the ammonia water is 1: 2-8Preferably, the ratio is 1: 3-8, or the mass ratio of the caprolactam to the water is 1: 2-8.

4. The method according to claim 1, wherein the temperature of the continuous hydrolysis or the continuous hydrolysis/amination reaction in step S1 is 300 to 500 ℃ and the gauge pressure is 0 to 3MPa, and the residence time in step S1 is preferably controlled to 0.1 to 1S, preferably 0.2 to 1S.

5. The method according to any one of claims 1 to 4, wherein in step S1, the continuous hydrolysis or the continuous hydrolysis-amination reaction is performed in the presence of a solid acid catalyst or a solid base catalyst.

6. The method of claim 1, wherein the catalyst used in step S2 comprises a combination of one or more of silica and alumina.

7. The method of claim 1, wherein the mass ratio of the ammonia gas in the step S2 to the starting caprolactam of the step S1 is 0.5-8: 1.

8. The method of claim 1, wherein the reaction temperature of step S2 is 300-500 ℃ and the gauge pressure is 0-2 MPa, and the residence time of step S2 is preferably 0.1-2S, preferably 0.2-2S.

9. The method according to claim 1, wherein the step S1 is performed in a first reactor, and the step S2 is performed in a second reactor, and the first reactor and the second reactor are connected in series.

10. The method according to claim 1, wherein the steps S1 and S2 are performed in the same fixed bed reactor, and the step S1 is performed in the first half of the fixed bed reactor, and the step S2 is performed in the second half of the fixed bed reactor.

Technical Field

The invention relates to the technical field of preparation of 6-aminocapronitrile, in particular to a method for producing a key intermediate 6-aminocapronitrile of hexamethylene diamine by a continuous gas-phase two-step method.

Background

1, 6-hexamethylene diamine is an important high-performance material intermediate, is mainly used for producing polyamide, such as nylon 66, nylon 610 and the like, can also be used for producing polyurethane, and can also be used as a curing agent of urea resin and epoxy resin.

The processes for producing hexamethylenediamine are classified into adiponitrile process, which is a major industrial process, and caprolactam process, which is classified into: butadiene process, acrylonitrile process, adipic acid process.

The butadiene method is characterized in that under the existence of transition metals such as nickel and the like and phosphorus ligands, one molecule of butadiene and two molecules of hydrocyanic acid are added to obtain adiponitrile and other by-products (methylglutaronitrile and the like); the advantages are low production cost and good product quality; the disadvantages are that virulent hydrocyanic acid is used, the occupational hazard is large, and the construction investment is high. The acrylonitrile method generally adopts a diaphragm-free electrolysis process, acrylonitrile is quantitatively converted into adiponitrile through a primary polymerization stage and a dimerization stage in electrochemical cathode hydrogenation; has the advantages of short process flow; the defects are that the steps of controlling the electrolysis process and the like are long, technical nodes are more, the safety risk is high, and explosion occurs when the first device (Runxing) in China is tried. The adipic acid method is used for ammoniating and dehydrating adipic acid to generate adiponitrile; the method has the advantages that the technical route is relatively mature, the adipic acid raw material has excessive productivity and reduced price; the disadvantages are high energy consumption, easy coking of the reactor and poor product quality.

In the 60 s of the 20 th century, waste nylon was used as a raw material to produce hexamethylene diamine in Dongli Japan, the pioneer of the technology for preparing hexamethylene diamine by a caprolactam method was started, the caprolactam reacts with ammonia gas under the action of a catalyst to obtain 6-aminocapronitrile, and the 6-aminocapronitrile is further hydrogenated and refined to obtain the hexamethylene diamine. The method is limited by the fact that caprolactam is high in price at that time, cannot be popularized further and has been stopped at present. In recent years, the caprolactam production capacity in China is increasingly surplus, so that the competitiveness of the caprolactam method hexamethylene diamine process is increasingly shown.

The patent application with the application number of 201710943063.4 discloses a method and a device for preparing 6-aminocapronitrile by a one-step liquid phase method and a liquid phase method of caprolactam, wherein caprolactam reacts with ammonia to prepare 6-aminocapronitrile under the catalysis of phosphoric acid or phosphate, the conversion rate of the caprolactam is only 50-60 percent, and the catalyst is not easy to recover. Chinese patent application No. CN201710942344.8 discloses a method for preparing 6-aminocapronitrile by caprolactam gas phase one-step method, mixing caprolactam steam and hot ammonia gas, and contacting and reacting with alkaline earth metal oxide, transition metal oxide, silicon dioxide and active alumina catalyst in a fixed bed reactor to prepare 6-aminocapronitrile, wherein the reaction conversion rate is increased to 96%. The caprolactam is easy to generate polymerization reaction in the gasification and reaction processes in the presence of a trace amount of water, so that the reaction selectivity is reduced, and meanwhile, the generated polymer covers the surface of the catalyst, so that the caprolactam is easy to coke at high temperature, and the stable operation of the device is further influenced.

Disclosure of Invention

The invention mainly aims to provide a method for producing a key intermediate 6-aminocapronitrile of hexamethylene diamine by a continuous gas-phase two-step method, so as to solve the problem that a catalyst is easy to coke when 6-aminocapronitrile is prepared by a caprolactam one-step method in the prior art.

To achieve the above object, according to one aspect of the present invention, there is provided a continuous gas-phase two-step process for producing 6-aminocapronitrile, a key intermediate of hexamethylenediamine, comprising: step S1, mixing caprolactam and water in a gas phase state for continuous hydrolysis or mixing caprolactam and ammonia water in a gas phase state for continuous hydrolysis ammoniation reaction to obtain a first product system containing 6-aminocaproic acid, 6-aminocaproic acid ammonium salt and/or 6-aminocaproamide; and step S2, carrying out continuous gas-phase catalytic ammoniation and dehydration reaction on the first product system and ammonia gas to obtain a second product system containing 6-aminocapronitrile.

Further, the step S1 includes atomizing caprolactam and mixing the atomized caprolactam with preheated water or preheated ammonia water, wherein the preheating temperature of the water or ammonia water is 300-500 ℃.

Further, NH in the ammonia water₃The mass content of the caprolactam is 1-50%, the mass ratio of the caprolactam to the ammonia water is 1: 2-8, preferably 1: 3-8, or the mass ratio of the caprolactam to the water is 1: 2-8.

Further, in the step S1, the temperature of the continuous hydrolysis or continuous hydrolysis/amination reaction is 300 to 500 ℃, the gauge pressure is 0 to 3MPa, and the residence time is preferably controlled to 0.1 to 1S, more preferably 0.2 to 1S in the step S1.

Further, in the step S1, the continuous hydrolysis or continuous hydrolysis/amination reaction is performed in the presence of a solid acid catalyst or a solid base catalyst.

Further, the catalyst used in the above step S2 includes one or a combination of silica and alumina.

Further, the mass ratio of the ammonia gas in the step S2 to the initial caprolactam in the step S1 is 0.5-8: 1.

Further, the reaction temperature in the step S2 is 300 to 500 ℃, the gauge pressure is 0 to 2MPa, and the residence time in the step S2 is preferably controlled to be 0.1 to 2S, preferably 0.2 to 2S.

Further, the above step S1 is performed in a first reactor, and the step S2 is performed in a second reactor, the first reactor and the second reactor being connected in series.

Further, the above step S1 and step S2 are performed in the same fixed bed reactor, and step S1 is performed in the first half of the fixed bed reactor, and step S2 is performed in the second half of the fixed bed reactor.

By applying the technical scheme of the invention, the method for continuously preparing 6-aminocapronitrile by using caprolactam is carried out by two steps, the caprolactam is subjected to ring-opening hydrolysis reaction in step S1 to obtain aminocaproic acid, neutralization reaction is carried out in the presence of ammonia to obtain aminocaproic acid ammonium salt, and further dehydration is carried out to obtain aminocaproamide; the alkaline reaction system in the presence of ammonia effectively reduces aminocaproic acid, thereby reducing catalytic polymerization on caprolactam; the excessive water has good depolymerization effect on the low polymer formed by caprolactam, and both the water and the low polymer greatly reduce the polymerization reaction of the caprolactam; the aminocaproic acid, the aminocaproic acid ammonium salt and/or the aminocaproamide in the first product system further perform gas phase catalytic ammoniation and dehydration reaction with ammonia gas to form 6-aminocapronitrile, and the polymerization reaction in S2 is effectively avoided because the caprolactam conversion rate in the first product system is extremely high. Therefore, the invention fundamentally reduces the problem that water generated by the reaction in the one-step process promotes the polymerization reaction of caprolactam serving as a raw material, and improves the selectivity of aminocapronitrile; effectively reduces the problems of catalyst deactivation and pressure drop increase caused by the polymerization and coking of caprolactam in the reactor, improves the stability of the device and prolongs the service life of the catalyst.

Detailed Description

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail with reference to examples.

As analyzed by the application, in the prior art, because caprolactam is easy to generate polymerization reaction in the gasification and reaction processes in the presence of a trace amount of water, the reaction selectivity is reduced, and simultaneously, the generated polymer covers the surface of the catalyst, so that the polymer is easy to coke at high temperature, and the stable operation of the device is further influenced. In order to solve the problem, in an exemplary embodiment of the present application, there is provided a method for continuously preparing 6-aminocapronitrile using caprolactam, the method comprising: step S1, mixing caprolactam and water in a gas phase state for continuous hydrolysis or mixing caprolactam and ammonia water in a gas phase state for continuous hydrolysis ammoniation reaction to obtain a first product system containing 6-aminocaproic acid, 6-aminocaproic acid ammonium salt and/or 6-aminocaproamide; and step S2, carrying out continuous gas-phase catalytic ammoniation and dehydration reaction on the first product system and ammonia gas to obtain a second product system containing 6-aminocapronitrile.

The hydrolysis and amination reaction process of the step S1 is as follows:

the reaction process involved in step S2 is as follows:

the method for continuously preparing 6-aminocapronitrile by using caprolactam comprises the following two steps of carrying out ring opening hydrolysis reaction on caprolactam in step S1 to obtain aminocaproic acid, carrying out neutralization reaction in the presence of ammonia to obtain aminocaproic acid ammonium salt, and further dehydrating to obtain aminocaproamide; the alkaline reaction system in the presence of ammonia effectively reduces aminocaproic acid, thereby reducing catalytic polymerization on caprolactam; the excessive water has good depolymerization effect on the low polymer formed by caprolactam, and both the water and the low polymer greatly reduce the polymerization reaction of the caprolactam; the aminocaproic acid, the aminocaproic acid ammonium salt and/or the aminocaproamide in the first product system further perform gas phase catalytic ammoniation and dehydration reaction with ammonia gas to form 6-aminocapronitrile, and the polymerization reaction in S2 is effectively avoided because the caprolactam conversion rate in the first product system is extremely high. Therefore, the invention fundamentally reduces the problem that water generated by the reaction in the one-step process promotes the polymerization reaction of caprolactam serving as a raw material, and improves the selectivity of aminocapronitrile; effectively reduces the problems of catalyst deactivation and pressure drop increase caused by the polymerization and coking of caprolactam in the reactor, improves the stability of the device and prolongs the service life of the catalyst.

In order to improve the reaction efficiency of step S1, it is preferable that in step S1, the atomized caprolactam is mixed with preheated water or preheated ammonia water, wherein the preheated temperature of the water or ammonia water is 300-500 ℃. The caprolactam is atomized and mixed with preheated water or preheated ammonia water, so that the contact area of the caprolactam and the preheated water is increased, the hydrolytic ammoniation reaction time is shortened, and the self-polymerization of the 6-aminocaproic acid and the catalytic polymerization reaction of the caprolactam can be more effectively reduced.

In order to further increase the reaction conversion rate, NH is preferably added to the ammonia water₃The mass content of the caprolactam is 0-50%, the mass ratio of the caprolactam to the ammonia water is 1: 2-8, or the mass ratio of the caprolactam to the water is 1: 2-8.

In a preferred embodiment of the present invention, in the step S1, the temperature of the continuous hydrolysis or continuous hydrolysis/amination reaction is 300 to 500 ℃, and the gauge pressure is 0 to 3MPa, and in the embodiment, the temperature and pressure are controlled to improve the efficiency of the hydrolysis/amination reaction. Preferably, the residence time in step S1 is controlled to be 0.1-1S to further reduce polymerization and avoid coking.

In order to accelerate the hydrolysis/amination reaction, it is preferable that the continuous hydrolysis or continuous hydrolysis/amination reaction is carried out in the presence of a solid acid catalyst or a solid base catalyst in step S1. The solid acid catalyst used in the present application may be ZSM-5, SO₄ ^2-/ZrO₂Etc., the solid base catalyst may be MgO, Mg/MCM-41, etc. Of course, the above solid acid catalyst and solid base catalystIs not essential to the hydrolytic amination reaction of step S1, and inert fillers may be used to fill the reactor in the actual reaction.

The catalyst used in the above step S2 may be a catalyst commonly used in one-step method in the prior art, and it is preferable that the catalyst used in the above step S2 include one or a combination of silica and alumina because the dehydration reaction mainly occurs in the step S2.

Since caprolactam is partially consumed in step S1 and converted to aminocaproic acid, an ammonium aminocaproate salt and/or aminocaproamide in the present application, it is preferable that the mass ratio of ammonia gas to starting caprolactam in the above step S2 is 0.5 to 7: 1.

As the conditions of the step S2 in the present application can refer to the conditions of the existing one-step method, the reaction temperature of the step S2 is preferably 300-500 ℃, and the gauge pressure is preferably 0-2 MPa. The use amount/circulation amount of the ammonia gas is reduced, so that the industrial implementation is facilitated. Preferably, in the step S2, the residence time is controlled to be 0.1-2S, so that the occurrence of polymerization reaction is further reduced.

The two-step continuous process of the present application can be carried out in two separate apparatuses, i.e., in one embodiment, the above step S1 is carried out in a first reactor, and the step S2 is carried out in a second reactor, the first reactor and the second reactor being connected in series. It is also possible to concentrate the steps S1 and S2 in one reactor, that is, step S1 is performed in the first half of the fixed bed reactor and step S2 is performed in the second half of the fixed bed reactor.

The advantageous effects of the present application will be further described below with reference to examples and comparative examples.

In the following examples, "%" is "mass%" unless otherwise specified.