CN111574401A - Method for producing hexamethylene diamine key intermediate 6-aminocapronitrile by continuous gas phase two-step method - Google Patents
Method for producing hexamethylene diamine key intermediate 6-aminocapronitrile by continuous gas phase two-step method Download PDFInfo
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Abstract
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.
Description
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.
Example 1:
heating water to 500 ℃, and mixing caprolactam and water in a ratio of 1: 8, and simultaneously pumping the mixture into a first reactor filled with inert fillers (porcelain balls), and carrying out hydrolysis reaction under the conditions of gauge pressure of 3MPa, reaction temperature of 500 ℃ and residence time of 1s to obtain a hydrolyzed material (aminocaproic acid). Mixing ammonia gas with the weight 0.5 time that of caprolactam and the hydrolysis material at 500 ℃, pumping the mixture into a second reactor filled with a silicon dioxide catalyst, carrying out catalytic ammoniation and dehydration reaction at 300 ℃, the gauge pressure of 0.1MPa, the reaction temperature of 350 ℃ and the retention time of 2s to generate 6-aminocapronitrile, wherein the one-way conversion rate of the caprolactam is 95.6 percent, and the one-way service life of the catalyst is determined to be 1320h when the selectivity of the aminocapronitrile is less than 98 percent.
Example 2:
1% ammonia was heated to 400 ℃, caprolactam was mixed with water at a ratio of 1: 5, and simultaneously pumping the mixture into a first reactor filled with solid acid (ZSM-5), and carrying out hydrolysis reaction under the conditions of gauge pressure of 1MPa, reaction temperature of 430 ℃ and residence time of 0.6s to obtain a hydrolysis material (aminocaproic acid). Mixing ammonia gas with the weight 3 times that of caprolactam and the hydrolysis material at 400 ℃, pumping the mixture into a second reactor filled with an alumina catalyst, carrying out catalytic ammoniation and dehydration reaction at 400 ℃, the gauge pressure of 0.6MPa, the reaction temperature of 450 ℃ and the retention time of 0.5s to generate 6-aminocapronitrile, wherein the one-way conversion rate of the caprolactam is 97.1 percent, and the one-way service life of the catalyst is determined to be 1400h when the selectivity of the aminocapronitrile is less than 98 percent.
Example 3:
heating 10% ammonia to 400 ℃, mixing caprolactam and ammonia in a ratio of 1: 5 weight percent of the mixture is simultaneously pumped into a first reactor filled with solid acid (ZSM-5), and hydrolysis and ammoniation reaction are carried out under the gauge pressure of 1MPa, the reaction temperature of 430 ℃ and the retention time of 0.6s, thus obtaining hydrolysis materials. Mixing ammonia gas with the weight 3 times of that of caprolactam and hydrolysis materials at 400 ℃, feeding the mixture into a second reactor filled with an alumina catalyst, carrying out catalytic ammoniation and dehydration reaction at 400 ℃, the gauge pressure of 0.6MPa, the reaction temperature of 450 ℃ and the retention time of 0.5s to generate 6-aminocapronitrile, judging the one-way service life of the catalyst when the one-way conversion rate of the caprolactam is 98.8 percent and the selectivity of the aminocapronitrile is less than 98 percent for 1500 h.
Example 4:
heating 10% ammonia to 400 ℃, mixing caprolactam and ammonia in a ratio of 1: 5 weight percent of the mixture is simultaneously pumped into a first reactor filled with solid acid (ZSM-5), and hydrolysis and ammoniation reaction are carried out under the gauge pressure of 1MPa, the reaction temperature of 430 ℃ and the retention time of 0.2s, thus obtaining hydrolysis materials. Mixing ammonia gas with the weight 3 times of that of caprolactam and hydrolysis materials at 400 ℃, feeding the mixture into a second reactor filled with an alumina catalyst, performing catalytic ammoniation and dehydration reaction at 400 ℃, the gauge pressure of 0.6MPa, the reaction temperature of 450 ℃ and the retention time of 0.5s to generate 6-aminocapronitrile, and judging the one-way service life of the catalyst when the one-way conversion rate of the caprolactam is 96.6 percent and the selectivity of the aminocapronitrile is less than 98 percent for 1550 h.
Example 5:
heating 10% ammonia to 400 ℃, mixing caprolactam and ammonia in a ratio of 1: and simultaneously pumping the mixture into a first reactor filled with solid acid (ZSM-5) in a weight ratio of 5, and performing hydrolysis and ammoniation reaction at a gauge pressure of 1MPa, a reaction temperature of 430 ℃ and a retention time of 1s to obtain a hydrolyzed material. Mixing ammonia gas with the weight 3 times of that of caprolactam and hydrolysis materials at 400 ℃, feeding the mixture into a second reactor filled with an alumina catalyst, carrying out catalytic ammoniation and dehydration reaction at 400 ℃, the gauge pressure of 0.6MPa, the reaction temperature of 450 ℃ and the retention time of 0.5s to generate 6-aminocapronitrile, judging the service life of the catalyst when the conversion per pass of the caprolactam is 99.5 percent and the selectivity of the aminocapronitrile is less than 98 percent for 1400 h.
Example 6:
heating 10% ammonia to 400 ℃, mixing caprolactam and ammonia in a ratio of 1:3 weight ratio and simultaneously pumped into a first reactor filled with solid acid (ZSM-5), and hydrolysis ammoniation reaction is carried out under the gauge pressure of 1MPa, the reaction temperature of 430 ℃ and the retention time of 0.6s to obtain hydrolysis materials. Mixing ammonia gas with the weight 3 times of that of caprolactam and hydrolysis materials at 400 ℃, feeding the mixture into a second reactor filled with an alumina catalyst, carrying out catalytic ammoniation and dehydration reaction at 400 ℃, the gauge pressure of 0.6MPa, the reaction temperature of 450 ℃ and the retention time of 0.5s to generate 6-aminocapronitrile, wherein the conversion per pass of the caprolactam is 97.9 percent, and the service life of the catalyst is determined to be 1400 hours when the selectivity of the aminocapronitrile is less than 98 percent.
Example 7:
heating 10% ammonia to 400 ℃, mixing caprolactam and ammonia in a ratio of 1: and simultaneously pumping the mixture into a first reactor filled with solid acid (ZSM-5) in an 8-weight ratio, and performing hydrolysis and ammoniation reaction at the gauge pressure of 1MPa, the reaction temperature of 430 ℃ and the retention time of 0.6s to obtain a hydrolyzed material. Mixing ammonia gas with the weight 3 times of that of caprolactam and hydrolysis materials at 400 ℃, feeding the mixture into a second reactor filled with an alumina catalyst, carrying out catalytic ammoniation and dehydration reaction at 400 ℃, the gauge pressure of 0.6MPa, the reaction temperature of 450 ℃ and the retention time of 0.5s to generate 6-aminocapronitrile, and judging the service life of the catalyst to be 1300h when the conversion per pass of the caprolactam is 99.3 percent and the selectivity of the aminocapronitrile is less than 98 percent.
Example 8:
heating 10% ammonia to 400 ℃, mixing caprolactam and ammonia in a ratio of 1: and (3) simultaneously pumping the mixture into a first reactor filled with solid acid (ZSM-5) in a weight ratio of 10, and performing hydrolysis and ammoniation reaction under the conditions of gauge pressure of 1MPa, reaction temperature of 430 ℃ and retention time of 0.6s to obtain a hydrolyzed material. Mixing ammonia gas with the weight 3 times of that of caprolactam and hydrolysis materials at 400 ℃, feeding the mixture into a second reactor filled with an alumina catalyst, carrying out catalytic ammoniation and dehydration reaction at 400 ℃, the gauge pressure of 0.6MPa, the reaction temperature of 450 ℃ and the retention time of 0.5s to generate 6-aminocapronitrile, and judging the service life of the catalyst to be 1300h when the conversion per pass of the caprolactam is 98.2 percent and the selectivity of the aminocapronitrile is less than 98 percent.
Example 9:
heating 10% ammonia to 400 ℃, mixing caprolactam and ammonia in a ratio of 1: 5 weight percent of solid acid (SO) is pumped into the pump at the same time4 2-/ZrO2) The first reactor is subjected to hydrolysis and ammoniation reaction under the conditions of gauge pressure of 1MPa, reaction temperature of 430 ℃ and residence time of 0.6s to obtain a hydrolysis material. Mixing ammonia gas with the weight 0.5 time that of caprolactam and the hydrolysis material at 400 ℃, feeding the mixture into a second reactor filled with an alumina catalyst, carrying out catalytic ammoniation and dehydration reaction at 400 ℃, the gauge pressure of 0.6MPa, the reaction temperature of 450 ℃ and the retention time of 0.5s to generate 6-aminocapronitrile, wherein the conversion per pass of the caprolactam is 98.7%, and the service life of the catalyst is determined to be 1400h when the selectivity of the aminocapronitrile is less than 98%.
Example 10:
heating 10% ammonia to 400 ℃, mixing caprolactam and ammonia in a ratio of 1: 5 weight percent of solid acid (SO) is pumped into the pump at the same time4 2-/ZrO2) The first reactor is subjected to hydrolysis and ammoniation reaction under the conditions of gauge pressure of 1MPa, reaction temperature of 430 ℃ and residence time of 0.6s to obtain a hydrolysis material. Will be 8 timesAmmonia gas with the weight of 400 ℃ of caprolactam is mixed with hydrolysis materials and is sent into a second reactor filled with an alumina catalyst, the mixture is subjected to catalytic ammoniation and dehydration reaction at the temperature of 400 ℃, the gauge pressure of 0.6MPa, the reaction temperature of 450 ℃ and the retention time of 0.5s to generate 6-aminocapronitrile, the conversion per pass of the caprolactam is 98.8 percent, and the service life of the catalyst is judged to be 1350h when the selectivity of the aminocapronitrile is less than 98 percent.
Example 11:
heating 10% ammonia to 400 ℃, mixing caprolactam and ammonia in a ratio of 1: 5 weight percent of solid acid (SO) is pumped into the pump at the same time4 2-/ZrO2) The first reactor is subjected to hydrolysis and ammoniation reaction under the conditions of gauge pressure of 1MPa, reaction temperature of 430 ℃ and residence time of 0.6s to obtain a hydrolysis material. Mixing ammonia gas with the weight 9 times that of caprolactam and the hydrolysis material at 400 ℃, feeding the mixture into a second reactor filled with an alumina catalyst, carrying out catalytic ammoniation and dehydration reaction at 400 ℃, the gauge pressure of 0.6MPa, the reaction temperature of 450 ℃ and the retention time of 0.5s to generate 6-aminocapronitrile, judging the service life of the catalyst to be 1350h when the conversion per pass of the caprolactam is 98.9 percent and the selectivity of the aminocapronitrile is less than 98 percent.
Example 12:
heating 10% ammonia to 400 ℃, mixing caprolactam and ammonia in a ratio of 1: 5 weight percent of the mixture is simultaneously pumped into a first reactor filled with solid acid (ZSM-5), and hydrolysis and ammoniation reaction are carried out under the gauge pressure of 1MPa, the reaction temperature of 430 ℃ and the retention time of 0.6s, thus obtaining hydrolysis materials. Mixing ammonia gas with the weight 3 times of that of caprolactam and hydrolysis materials at 400 ℃, feeding the mixture into a second reactor filled with an alumina catalyst, carrying out catalytic ammoniation and dehydration reaction at 400 ℃, the gauge pressure of 0.6MPa, the reaction temperature of 450 ℃ and the retention time of 0.2s to generate 6-aminocapronitrile, and judging the service life of the catalyst by judging that the conversion per pass of the caprolactam is 98.6 percent and the selectivity of the aminocapronitrile is less than 98 percent when the catalyst is used for 1450 h.
Example 13:
heating 10% ammonia to 400 ℃, mixing caprolactam and ammonia in a ratio of 1: 5 weight percent of the mixture is simultaneously pumped into a first reactor filled with solid acid (ZSM-5), and hydrolysis and ammoniation reaction are carried out under the gauge pressure of 1MPa, the reaction temperature of 430 ℃ and the retention time of 0.6s, thus obtaining hydrolysis materials. Mixing ammonia gas with the weight 3 times that of caprolactam and the hydrolysis material at 400 ℃, feeding the mixture into a second reactor filled with an alumina catalyst, carrying out catalytic ammoniation and dehydration reaction at 400 ℃, the gauge pressure of 0.6MPa, the reaction temperature of 450 ℃ and the retention time of 2s to generate 6-aminocapronitrile, judging the service life of the catalyst to be 1250h when the conversion per pass of the caprolactam is 99.5 percent and the selectivity of the aminocapronitrile is less than 98 percent.
Example 14:
heating 10% ammonia to 400 ℃, mixing caprolactam and ammonia in a ratio of 1: 5 weight percent of the mixture is simultaneously pumped into a first reactor filled with solid acid (ZSM-5), and hydrolysis and ammoniation reaction are carried out under the gauge pressure of 1MPa, the reaction temperature of 430 ℃ and the retention time of 0.6s, thus obtaining hydrolysis materials. Mixing ammonia gas with the weight 3 times that of caprolactam and the hydrolysis material at 400 ℃, feeding the mixture into a second reactor filled with an alumina catalyst, carrying out catalytic ammoniation and dehydration reaction at 400 ℃, the gauge pressure of 0.6MPa, the reaction temperature of 450 ℃ and the retention time of 3s to generate 6-aminocapronitrile, wherein the one-way conversion rate of caprolactam is 99.7 percent, and the service life of the catalyst is determined when the selectivity of aminocapronitrile is less than 98 percent for 1200 h.
Example 15:
50% ammonia was heated to 320 ℃ and caprolactam was mixed with ammonia in a ratio of 1:2, pumping the mixture into the top of a reactor filled with solid alkali (MgO) at the same time, and carrying out hydrolysis reaction at the gauge pressure of 0.1MPa, the reaction temperature of 320 ℃ and the retention time of 0.2s to obtain a hydrolyzed material. Pumping ammonia gas with the weight 7 times that of caprolactam and at the temperature of 330 ℃ into the lower section of a reactor filled with a silicon dioxide and aluminum oxide composite catalyst from the middle part of the reactor, carrying out catalytic ammoniation and dehydration reaction at the temperature of 320 ℃, the gauge pressure of 0.1MPa, the reaction temperature of 330 ℃ and the retention time of 0.2s to generate 6-aminocapronitrile, judging the service life of the catalyst for 1600h when the conversion per pass of the caprolactam is 99.6 percent and the selectivity of the aminocapronitrile is less than 98 percent.
From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects:
the method can be realized in a single tubular reactor, ammonia water solution and ammonia are pumped in sections, the aim of synthesizing aminocapronitrile by caprolactam through a continuous two-step method is realized, the process route is simple, the operation is easy, and the method is suitable for large-scale application;
the problem that water generated in the one-step process promotes the polymerization reaction of caprolactam serving as a raw material is solved from the source, and the high conversion rate and the high selectivity of the aminocapronitrile are ensured;
the process effectively reduces the problems of catalyst deactivation and pressure drop increase caused by polymerization and coking of caprolactam in the reactor, improves the stability of the device, and prolongs the service life of the catalyst.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
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.
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| CN111978207A (en) * | 2020-09-22 | 2020-11-24 | 江苏扬农化工集团有限公司 | Method for synthesizing hexamethylene diamine key intermediate |
| CN111978206A (en) * | 2020-09-22 | 2020-11-24 | 江苏扬农化工集团有限公司 | Process system for synthesizing hexamethylene diamine key intermediate |
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| CN107602416A (en) * | 2017-10-11 | 2018-01-19 | 中国天辰工程有限公司 | A kind of method that vapor phase method prepares 6 amino-capronitriles |
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