CN-121990943-A - Method for synthesizing 6-aminocapronitrile from caprolactam

CN121990943ACN 121990943 ACN121990943 ACN 121990943ACN-121990943-A

Abstract

The invention provides a method for synthesizing 6-aminocapronitrile from caprolactam, which comprises the following steps that a gasification device is sequentially provided with a uniform distribution part, a high-efficiency dispersion part, a high-temperature gasification part and an in-situ separation part from top to bottom, liquid-phase caprolactam is injected from the top end of the gasification device, ammonia gas is injected through the high-efficiency dispersion part, in the high-efficiency dispersion part, the liquid-phase caprolactam is broken to form liquid drops under the shearing action of gravity and the ammonia gas in a first circular tube array, after high-temperature gasification, a gas phase is output from the side part of the gasification device, enters from the bottom of a reactor filled with an integral catalyst, and is output from the top after reaction of the integral catalyst. The invention can not only gasify caprolactam with high efficiency and is not easy to produce coking, but also can accurately control the residence time of gas phase reactants in the reactor, greatly improve the reaction efficiency, reduce the discharge amount of waste in the production process of hexamethylenediamine, reduce the cost, improve the economic benefit and provide guarantee for the green safety and safety production.

Inventors

WANG XIAODA
GE XUEHUI
LIU YAN
LIU ZHIYONG
ZHOU CAIJIN
JIANG LILONG
PAN DEBIAO
WANG JIANHUA

Assignees

福建省恒申化工科技有限公司
福州大学

Dates

Publication Date: 20260508
Application Date: 20251215

Claims (10)

1. A method for synthesizing 6-aminocapronitrile from caprolactam is characterized by comprising the following steps: (1) The gasification process comprises the steps of injecting liquid caprolactam from the top end of a gasification device, injecting ammonia through a high-efficiency dispersing component, and dispersing the caprolactam into liquid drops, wherein the gasification device is sequentially provided with a uniform distributing component, a high-efficiency dispersing component, a high-temperature gasification component and an in-situ separation component from top to bottom; the uniform distribution component comprises an elliptical end socket and a bottom plate with round holes, each round hole is connected with a round pipe with the same diameter, and the outlet of the round pipe is contracted and thinned; The high-efficiency dispersing component comprises uniformly distributed first circular tubes, and the positions and the number of the first circular tubes correspond to those of the uniformly distributed component circular tubes; The high-temperature gasification component comprises a tube array dividing wall type heat exchanger, wherein a heated fluid is communicated with a tube side, and a heat carrier is communicated with a shell side; the in-situ separation component is arranged at the bottom of the gasification device and is used for separating unvaporized caprolactam; In the high-efficiency dispersing component, the liquid-phase caprolactam is broken to form liquid drops in the first circular tube array under the shearing action of gravity and ammonia gas, and after high-temperature gasification, a gas phase is output from the side part of the gasification device, and an unvaporized liquid phase is discharged from the bottom; (2) The reaction process is that gas phase materials enter from the bottom of a reactor filled with the integral catalyst and are output from the top after reacting with the integral catalyst.
2. The method for synthesizing 6-aminocapronitrile from caprolactam according to claim 1, wherein the diameter of the contracted outlet of the circular tube is reduced by 20% compared with the diameter of the circular tube; The diameter and length of the circular tubes of the uniform distribution component are respectively 1-3mm and 1-20cm, the length of the shrinkage outlet is 1-2cm, the circular tubes are distributed on the disc in an annular shape, and the distance between the tubes is 3-6mm.
3. The method for synthesizing 6-aminocapronitrile from caprolactam according to claim 1, wherein the diameter of the first circular tube array of the high-efficiency dispersing component is 20% larger than that of the round tube of the uniform distributing component, and the length of the first circular tube array is 1-20cm.
4. A process for the synthesis of 6-aminocapronitrile from caprolactam according to claim 1, wherein the length of the second circular array of tubes in the high temperature gasification unit is in the range of 100-300cm.
5. A process for the synthesis of 6-aminocapronitrile from caprolactam according to claim 1, wherein in step (1) the liquid phase caprolactam and the ammonia gas are fed at a temperature in the range of 50 to 150℃and the molar ratio of the two is ammonia: caprolactam=5 to 50:1.
6. A process for the synthesis of 6-aminocapronitrile from caprolactam according to claim 1, wherein the outlet material temperature of the high temperature gasification unit of step (1) is in the range of 300 to 450 ℃.
7. A process for the synthesis of 6-aminocapronitrile from caprolactam according to claim 1, wherein the gasification device in step (1) is operated at a pressure in the range of from 1 to 200kPa.
8. The method for synthesizing 6-aminocapronitrile from caprolactam according to claim 1, wherein in the step (2), the monolithic catalyst has a honeycomb structure, and the honeycomb channels closer to the center have smaller hydraulic diameters and the channels farther from the center have larger hydraulic diameters.
9. The method for synthesizing 6-aminocapronitrile from caprolactam according to claim 8, wherein the monolithic catalyst in step (2) has a circular cross section and has a hydraulic diameter in the range of 5-30mm, and the surface of the monolithic catalyst in step (2) is coated with an acidic or basic catalyst coating using cordierite honeycomb ceramic as a substrate.
10. The method for synthesizing 6-aminocapronitrile from caprolactam according to claim 1, wherein the reaction device in the step (2) adopts two sets of parallel integrated catalyst devices, one for each.

Description

Method for synthesizing 6-aminocapronitrile from caprolactam Technical Field The invention relates to the technical field of organic chemical industry, in particular to a method for synthesizing 6-aminocapronitrile by gasifying and ammonolysis of caprolactam, which is suitable for efficient preparation of hexamethylenediamine intermediates. Background 1, 6-Hexamethylenediamine, also known as 1, 6-diaminohexane, hexamethylenediamine, is an organic compound of the formula C6H16N2. Hexamethylenediamine is used for the synthesis of nylon 66 and 610 resins, polyurethane resins, ion exchange resins and hexamethylene diisocyanate, as curing agents for urea-formaldehyde resins, epoxy resins and the like, as organic crosslinking agents and the like, as stabilizers, bleaching agents for the textile and paper industry, corrosion inhibitors for aluminum alloys, neoprene emulsifiers and the like. The hexamethylenediamine and hydrochloric acid form salt below 28 ℃ to obtain 1, 6-hexamethylenediamine hydrochloride (6055-52-3), which can be used for producing the bactericide chlorhexidine acetate. Hexamethylenediamine is also used in the production of adhesives, aircraft coatings, and rubber vulcanization accelerators. There are many industrial processes for producing hexamethylenediamine at present, including adipic acid process, butadiene process, acrylonitrile process, hexanediol process and caprolactam process, depending on the raw materials used. Among them, the adipic acid process, the butadiene process and the acrylonitrile dimerization process are processes for producing hexamethylenediamine by hydrogenation of adiponitrile as an intermediate, and at present, almost all processes for mass production of hexamethylenediamine are adiponitrile catalytic hydrogenation processes. In recent years, with the rapid increase of caprolactam productivity, a method for synthesizing hexamethylenediamine from caprolactam has been attracting more and more attention. The method generally obtains hexamethylenediamine through two reaction steps, wherein the first reaction is that caprolactam and ammonia are subjected to ammonolysis reaction to obtain water and 6-aminocapronitrile, and the second reaction is that 6-aminocapronitrile and hydrogen are subjected to reaction to obtain hexamethylenediamine. The bottleneck step in synthesizing hexamethylenediamine by a caprolactam method is an ammonolysis reaction of caprolactam, and the reaction can be realized by a liquid phase method and a gas phase method. For example, patent CN107739318a discloses a liquid phase process for the preparation of 6-aminocapronitrile, in which liquid phase caprolactam and excess hot ammonia gas are subjected to a gas-liquid two-phase reaction at 260-280 ℃ for a period of time of about 0.5-2 hours, with a caprolactam conversion of about 65%. The liquid phase process suffers from the problem that the conversion is not high and the catalyst is difficult to recycle. For another example, patent CN107602416a discloses a gas phase process for preparing 6-aminocapronitrile from caprolactam, which comprises gasifying caprolactam at high temperature and then reacting with an excess of hot ammonia gas at 300-400 ℃ for a very short time (about 1 s) with a conversion of more than 98% under strict control of the reaction time. One of the key operations of the gas phase process is the gasification of caprolactam. The difficulty of this step is that caprolactam is susceptible to polymerization reaction during high temperature gasification, resulting in problems of low gasification efficiency, low selectivity of subsequent reaction, etc. To enhance the caprolactam gasification process, caprolactam is usually gasified with another raw material, hot ammonia gas, in the reaction process as a heat source. The liquid caprolactam is dispersed by the annular liquid phase distribution device in the patents CN 112321456B, CN 115260058B, CN 116603460A and CN 118987637A, and then heated and gasified by adopting a high Wen Anqi. In this process, the caprolactam distribution unit is usually directly exposed to high temperature ammonia gas. After long-time use, the outlet of the distribution device is always blocked due to polymerization of caprolactam, so that liquid caprolactam cannot be uniformly distributed, and further bad phenomena such as poor gasification effect, serious polymerization and the like are caused. The patents CN 113426377A and CN 116617690A introduce ammonia into the venturi, creating a negative pressure at the throat of the tube, by means of which caprolactam is gasified and enters the venturi from the side tube of the throat, merging with the ammonia cross-flow. In the method, the pipe throat is thin, the blockage is easy to cause, and the long-term stable operation is difficult. Another key operation of the gas phase process is the accurate control of the residence time of the gas phase in the reactor. The reaction is a very rapid chemical reaction, requiring only