A process for the preparation of N-ethyl-1,6-hexanediamine and products made therefrom

Abstract

The application discloses a method for preparing N-ethyl-1,6-hexanediamine. The method comprises the following steps: taking halogen ethane, hexanediamine and a piece of alkali aqueous solution as raw materials, and generating N-ethyl-1,6-hexanediamine synthetic liquid through a substitution reaction under the action of a phase transfer catalyst; layering the synthetic liquid, and obtaining a product solution through solvent extraction of a water layer; and combining an extracted oil layer and a layered oil layer, desolventizing, desolventizing light components and rectifying to obtain N-ethyl-1,6-hexanediamine finished products. The substitution reaction of halogen ethane and hexanediamine can improve the conversion rate of raw materials, and the phase transfer catalyst can effectively shorten the reaction time. The synthesis process has the advantages of mild reaction conditions, high product yield and content, and low raw material consumption.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of fine chemical industry, and relates to a method for preparing N-ethyl-1,6-hexanediamine and a product prepared therefrom. BACKGROUND

[0002] Hexanediamine is an important fine chemical intermediate, which is widely used in the synthesis of hexamethylene diisocyanate, nylon 66 and other products. The production processes of hexanediamine mainly include adiponitrile method, hexanediol method, caprolactam method and butadiene method. At present, most companies adopt the adiponitrile method to produce hexanediamine. A small number of manufacturers also use the caprolactam method, such as Ningxia Ruite Company.

[0003] The preparation of hexanediamine by the adiponitrile method is divided into high-pressure method and low-pressure method. The dominant process route for producing hexanediamine in the world is the low-pressure method, which uses Raney catalyst for catalytic hydrogenation, the reaction temperature is 60-100℃, and the pressure is 1.3-3 MPa. Compared with the high-pressure method, the low-pressure method has mild reaction conditions, high safety and low equipment investment. In the process of synthesizing hexanediamine by the low-pressure method, various by-products are generated, such as azepane, aminomethylcyclopentylamine, 1,2-cyclohexanediamine and dihexene triamine. Under normal circumstances, in order to inhibit the rapid decline of catalyst activity, it is necessary to use ethanol solvent, which will react with hexanediamine to generate the by-product N-ethyl-1,6-hexanediamine.

[0004] When hexanediamine is synthesized by the caprolactam method, ethanol is used as the solvent, and N-ethyl-1,6-hexanediamine impurities are also generated. The boiling point of N-ethyl-1,6-hexanediamine is close to that of hexanediamine, and it is difficult to separate from hexanediamine. Therefore, multiple rectification purifications are required to obtain qualified products, resulting in high energy consumption in the post-processing process. Therefore, accurately determining the content of N-ethyl-1,6-hexanediamine in hexanediamine is very important for selecting appropriate separation methods and means, and then reducing energy consumption.

[0005] In industry, the external standard quantitative method is usually used to determine the content of impurities in hexanediamine. Therefore, it is very important to provide high-content N-ethyl-1,6-hexanediamine standard sample for accurate determination of the content of the impurity in hexanediamine.

[0006] The literature "Process and kinetics of preparing hexanediamine by catalytic hydrogenation of adiponitrile" (Zhang H. Process and kinetics of preparing hexanediamine by catalytic hydrogenation of adiponitrile [D]. Zhengzhou University, 2012.) discloses a method for synthesizing hexanediamine in a batch kettle reactor. The synthesis process uses ethanol as the solvent and Raney nickel catalyst, the catalyst dosage is 5%, the alkali content is 0.5%, the reaction temperature is 75℃, the pressure is 3.3 MPa, the reaction time is 8h, and the yield of hexanediamine is 96%. The content and yield of N-ethyl-1,6-hexanediamine are not further discussed in the literature.

[0007] The document "Synthesis of N-ethylethylenediamine" (Wei Wenlong, Zhang Zhonghua, Chang Honghong. Synthesis of N-ethylethylenediamine [J]. Shanxi Chemical Industry, 2006 (05): 3-4+32.) discloses a synthesis method of N-ethylhexanediamine. The substance is homologous with N-ethyl-1, 6-hexanediamine. The synthesis process uses bromoethane, ethylenediamine and sodium hydroxide as reactants, and uses cyclohexane to extract the aqueous solution to prepare N-ethylethylenediamine. The process has the advantages of simple steps, easy temperature control and high product quality. However, the yield of the process is only 64.56%, which is relatively low.

[0008] Patent CN102030656B discloses a synthesis method of N-ethylethylenediamine. The synthesis process is as follows: ethylenediamine and bromoethane are synthesized by halogenated alkyl aminolysis reaction, the generated hydrogen bromide is neutralized with inorganic base, and finally N-ethylethylenediamine is obtained by fractionation. The process uses a water absorbent to remove the water generated by the neutralization of the inorganic base; the water absorbent is selected from polyacrylic acid, cassava starch grafted sodium polyacrylate or carboxymethyl cellulose grafted polyacrylamide. The highest yield given in the process examples is 83.42%, which is relatively low.

[0009] Therefore, there is an urgent need to develop a synthesis method of N-ethyl-1, 6-hexanediamine with fast reaction speed, mild reaction conditions, low raw material consumption, high yield and high content of product. SUMMARY

[0010] In view of the above, the present application provides a method for preparing N-ethyl-1, 6-hexanediamine, and the synthesis chemical equation is shown as formula 1,

[0011]

[0012] Wherein, X is a halogen atom; PTC is a phase transfer catalyst. The reaction is a substitution reaction of 1, 6-hexanediamine and haloethane, and in the case of excess 1, 6-hexanediamine, the reaction tends to generate a mono-substituted product, i.e. the product N-ethyl-1, 6-hexanediamine of the present application.

[0013] The process flow chart of the method is shown as Figure 1 Compared with the prior art, the present application has the advantages of fast reaction speed, mild reaction conditions, high product yield (calculated by haloethane) and content, and low raw material consumption. The present application is realized by the following technical solutions:

[0014] A method for preparing N-ethyl-1, 6-hexanediamine, characterized in that the method comprises:

[0015] (1) Put hexanediamine, aqueous sodium hydroxide solution and phase transfer catalyst into a kettle, then add haloethane dropwise into the kettle, and continue to react after stopping the dropwise addition;

[0016] (2) separating the material in the kettle in step (1) into a layered water layer and a layered oil layer; the layered water layer is subjected to an extraction process at room temperature using a solvent to obtain a raffinate water layer and an extracted oil layer;

[0017] (3) combining the layered oil layer in step (2) and the extracted oil layer, and subjecting the combined oil layer to a desolventizing process, a light-removing process and a rectification process in sequence to obtain N-ethyl-1, 6-hexanediamine product.

[0018] Preferably, in some embodiments, in step (1), the phase transfer catalyst is a quaternary ammonium salt; further preferably, the quaternary ammonium salt is selected from one or more of triethylbenzylammonium chloride, hexadecyltrimethylammonium chloride, hexadecyltriethylammonium chloride.

[0019] Preferably, in some embodiments, in step (2), after the extraction process, the raffinate water layer is subjected to azeotropic distillation, and the obtained aqueous solution of the solvent is reused in the extraction process in step (2). Preferably, in some embodiments, in step (3), in the desolventizing process, the desorbed solvent is reused in the extraction process in step (2).

[0020] Preferably, in some embodiments, in step (3), in the light-removing process, the desorbed hexanediamine is reused in the kettle in step (1).

[0021] In some embodiments, the molar ratio of the hexanediamine, the piece of alkali, the phase transfer catalyst and the haloethane is 1.5-3: 1-1.1: 0.02-0.2: 1.

[0022] In some embodiments, the haloethane refers to one of bromoethane and iodoethane.

[0023] According to the present application, preferably, in some embodiments, in step (1), the concentration of the aqueous piece of alkali is 5-15%; in some embodiments, the reaction temperature is 25-35℃; in some embodiments, the time for dropping the haloethane is 2-4h;

[0024] Preferably, in some embodiments, in step (2), the solvent is one of toluene, chloroform and dichloroethane; in some embodiments, the mass ratio of the solvent to the water layer is 0.5-1: 1; in some embodiments, the extraction is performed 1-4 times; in some embodiments, the azeotropic distillation is controlled so that the solvent content in the kettle residue after the azeotropic distillation is lower than 100ppm.

[0025] Preferably, in some embodiments, in step (3), the desolventizing procedure, the solvent content in the desolventizing tower kettle is controlled to be lower than 50 ppm; in some embodiments, the light-removing procedure, the hexamethylene diamine content in the light-removing tower kettle is controlled to be lower than 500 ppm; in some embodiments, the rectifying procedure, the content of the overhead product is controlled to be higher than 99%.

[0026] and an N-ethyl-1,6-hexanediamine product prepared by any of the above methods. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 A process flow diagram for preparing an N-ethyl-1,6-hexanediamine product. DETAILED DESCRIPTION

[0028] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not critical to the properties. The endpoints of the ranges and the individual points within the ranges can be combined with one another to recite one or more new ranges or points not expressly disclosed. These new ranges are considered disclosed herein.

[0029] The method for preparing N-ethyl-1,6-hexanediamine of the present application is shown in Figure 1 (1) putting hexamethylene diamine, aqueous caustic solution, and phase transfer catalyst into a kettle, and then adding dropwise halogen ethane into the kettle, and continuing the reaction for a period of time after the dropping is stopped.

[0030] (2) separating the materials in the kettle of step (1) into a layered water layer and a layered oil layer; using a solvent to extract the layered water layer at room temperature to obtain a raffinate water layer and an extracted oil layer; after the extraction procedure, co-boiling distilling the raffinate water layer, controlling the solvent content in the kettle residue after the co-boiling distillation to be lower than 100 ppm, and then reusing the obtained water layer, i.e., the aqueous solution of the solvent, to the extraction procedure of step (2).

[0031] (3) combining the layered oil layer and the extracted oil layer in step (2) and sending them to a desolventizing tower to perform a desolventizing procedure, controlling the solvent content in the desolventizing tower kettle to be lower than 50 ppm, and then reusing the desolventized solvent to the extraction procedure of step (2); sending the kettle residue to a light-removing tower.

[0032] (4) performing a light-removing procedure on the kettle residue of step (3), controlling the hexamethylene diamine content in the light-removing tower kettle to be lower than 500 ppm, and then reusing the desolventized hexamethylene diamine to the kettle of step (1); sending the kettle residue to a rectifying tower.

[0033] (5) The residue of step (5) is subjected to a rectification process, and the content of the N-ethyl-1,6-hexanediamine product at the top of the column is controlled to be higher than 99%, to obtain N-ethyl-1,6-hexanediamine finished product.

[0034] The present application adopts halogen ethane and hexanediamine to undergo substitution reaction, piece alkali aqueous solution as acid binding agent, phase transfer catalyst catalyzes reaction, can effectively improve the conversion rate of raw materials and shorten the reaction time; on the other hand, by virtue of the characteristics of solvent and water azeotrope, distillation recovery solvent in raffinate solution, reuse to the process of extraction can effectively reduce the raw material consumption, reduce the preparation cost. Among them, piece alkali is sodium hydroxide.

[0035] Preferably, in some embodiments, in step (1), the phase transfer catalyst is a quaternary ammonium salt; further preferably, the quaternary ammonium salt is selected from one or more of triethylbenzylammonium chloride, hexadecyltrimethylammonium chloride, hexadecyltriethylammonium chloride.

[0036] According to the present application, the source of the phase transfer catalyst is not limited as long as the purpose of the present application can be achieved, and in some embodiments, the source of the phase transfer catalyst can be commercially available with a purity of 99% or more.

[0037] In the present application, unless otherwise specified, the purity and content refer to mass content.

[0038] Preferably, in some embodiments, in step (2), after the extraction process, the raffinate water layer is subjected to azeotropic distillation, and the obtained aqueous solution of the solvent is reused in the extraction process of step (2).

[0039] Preferably, in some embodiments, in step (3), in the desolventization process, the desorbed solvent is reused in the extraction process of step (2); the mass content percentage of the solvent in the desorbed solvent is 99% or more, and the mass content percentage of water is 1% or less; preferably, the mass content percentage of the solvent in the desorbed solvent is 99.5% or more, and the mass content percentage of water is 0.05% or less.

[0040] Preferably, in some embodiments, in step (3), in the light-removing process, the desorbed hexanediamine is reused in the kettle of step (1); the mass content percentage of hexanediamine in the desorbed hexanediamine is 99% or more, and the mass content percentage of chloroform is 1% or less; preferably, the mass content percentage of hexanediamine in the desorbed hexanediamine is 99.5% or more, and the mass content percentage of chloroform is 0.05% or less.

[0041] The method for detecting the content of the substance is well known to those skilled in the art, and will not be described here. The process of recycling the solvent or hexamethylene diamine is a steady-state process, i.e. the content and weight of each recycling batch are close and do not change greatly with the number of recycling batches. When recycling for the first time, the content of the solvent or hexamethylene diamine needs to be detected first, and the amount of the solvent or hexamethylene diamine that needs to be supplemented is determined according to the content. When recycling for the second time, the corresponding amount of the solvent or hexamethylene diamine that needs to be supplemented can be determined. The use of the foregoing embodiments can effectively reduce the consumption of raw materials and reduce the preparation cost by recycling the corresponding raw materials or solvent.

[0042] In some embodiments, the molar ratio of the hexamethylene diamine, the caustic soda, the phase transfer catalyst and the haloethane is 1.5-3:1-1.1:0.02-0.2:1; preferably, the molar ratio of the hexamethylene diamine, the caustic soda, the phase transfer catalyst and the haloethane is 1.8-2.5:1.05-1.1:0.04-0.1:1.

[0043] In some embodiments, the haloethane refers to one of bromoethane and iodoethane.

[0044] According to the present application, preferably, in some embodiments, in step (1), the concentration of the aqueous caustic soda solution is 5-15%; preferably, the concentration of the aqueous caustic soda solution is 7.5-12.5%; in some embodiments, the reaction temperature is 25-35°C; preferably, the reaction temperature is 28-32°C; in some embodiments, the time for dropping the haloethane is 2-4h; in some embodiments, the time for continuing the reaction is 0.5-2h. The use of the foregoing embodiments can effectively improve the conversion rate of the raw materials and shorten the reaction time.

[0045] According to the present application, as long as the purpose of the present application can be achieved, the source of the hexamethylene diamine, the caustic soda and the haloethane is not limited, and in some embodiments, the source of the hexamethylene diamine, the caustic soda and the haloethane can be commercially available and the purity is more than 99%; wherein the caustic soda is subsequently configured into an aqueous solution with the concentration.

[0046] Preferably, in some embodiments, in step (2), the solvent is one of toluene, chloroform and dichloroethane; in some embodiments, the mass ratio of the solvent to the water layer is 0.5-1:1; preferably, the mass ratio of the solvent to the water layer is 0.5-0.75:1; in some embodiments, the extraction is performed for 1-4 times; preferably, the extraction is performed for 2-4 times; in some embodiments, the azeotropic distillation is controlled such that the content of the solvent in the residue after the azeotropic distillation is lower than 100ppm. The use of the foregoing embodiments can effectively reduce the consumption of raw materials and reduce the preparation cost by distilling the solvent in the raffinate solution and recycling it to the extraction process by taking advantage of the azeotropic characteristics of the solvent and water.

[0047] Preferably, in some embodiments, in step (3), the desolventizing process, the solvent content in the desolventizing tower kettle is controlled to be less than 50 ppm; in some embodiments, the light removal process, the hexamethylene diamine content in the light removal tower kettle is controlled to be less than 500 ppm; in some embodiments, the rectification process, the content of the overhead product is controlled to be higher than 99%. By using the foregoing embodiments, the purity of the product can be effectively improved.

[0048] According to the present application, as long as the purpose of the present application can be achieved, the conditions of the desolventizing process are not limited, and in some embodiments, the conditions include: the desolventizing tower kettle temperature is 60-110°C, and the absolute pressure is 150-760 mmHg.

[0049] According to the present application, as long as the purpose of the present application can be achieved, the conditions of the light removal process are not limited, and in some embodiments, the conditions include: the light removal tower kettle temperature is 80-105°C, and the absolute pressure is 5-15 mmHg.

[0050] According to the present application, as long as the purpose of the present application can be achieved, the conditions of the rectification process are not limited, and in some embodiments, the conditions include: the rectification tower kettle temperature is 80-120°C, and the absolute pressure is 5-15 mmHg.

[0051] According to the present application, as long as the purpose of the present application can be achieved, the source of the equipment used in the present application is not limited, and in some embodiments, the source of the equipment is commercially available.

[0052] In order for those skilled in the art to better understand the present application, the present application will be described in detail below with specific examples, and the protection scope of the present application is not limited to the following examples, and these examples are listed only for exemplary purposes and do not limit the present application in any way.

[0053] Example

[0054] Example 1

[0055] (1) 292.9 g of hexamethylene diamine (purity: 99%, industrial grade, Swifty Company, same below), 440 g of aqueous caustic soda (wt: 10%, purity: 99%, industrial grade, Swifty Company, same below), and 9.2 g of triethylbenzylammonium chloride (purity: 99%, industrial grade, Macklin Reagent Company, same below) were put into a kettle, and the temperature was raised to 30°C. After 110 g of bromoethane (purity: 99%, industrial grade, Macklin Reagent Company, same below) was added dropwise into the kettle, the dropwise addition was completed in 3 h, and the reaction was continued for another 1 h, then the reaction was completed, and the weight of the synthesis liquid was 852.1 g. The molar ratio of the reactants, hexamethylene diamine, caustic soda, triethylbenzylammonium chloride, and bromoethane, was 2.5:1.1:0.04:1.

[0056] (2) The synthetic solution in step (1) was separated into two layers, 660.1 g of water layer and 190.9 g of oil layer. The water layer was extracted with 396.6 g of chloroform (purity: 99%, industrial grade, supplied by Macklin Reagent Co., Ltd.) three times at room temperature, and 447.6 g of oil layer was obtained. The water layer was then azeotropically distilled to obtain the chloroform and water azeotrope, which was reused in the extraction process. The mass of the azeotrope was 9.8 g, and the composition was 80.2% chloroform and 19.8% water. The chloroform content in the residue after azeotropic distillation was 56 ppm.

[0057] (3) The oil layer in step (2) was combined with the extracted oil layer, and the combined solution was desolventized. The temperature in the desolventizing column was controlled to be less than 100°C, and the absolute pressure was 760 mmHg. After desolventization, the chloroform content in the desolventizing column was 45 ppm. The desorbed chloroform was reused in the extraction process in step (2), and the mass of the recovered chloroform in the overhead was 386.8 g, with a composition of 99.74% chloroform and 0.2% water. The desolventizing column residue was then stripped. The temperature in the stripping column was controlled to be less than 99°C, and the absolute pressure was 12 mmHg. After stripping, the hexanediamine content in the stripping column was 267 ppm. The desorbed hexanediamine was reused in the column in step (1), and the mass of the recovered hexanediamine in the overhead was 171.7 g, with a composition of 99.8% hexanediamine and 0.1% chloroform. The stripping column residue was then rectified. The temperature in the rectifying column was controlled to be less than 120°C, and the absolute pressure was 12 mmHg. After rectification, the N-ethyl-1,6-hexanediamine content in the overhead was 99.3%, and the mass of the product was 133.8 g, with a yield of 92.3%.

[0058] Example 2

[0059] (1) 234.3 g of hexanediamine (purity: 99%), 366.7 g of aqueous sodium hydroxide solution (wt: 12%), and 19.4 g of cetyltrimethylammonium chloride (purity: 99%, industrial grade, supplied by Macklin Reagent Co., Ltd.) were added to a column, and the temperature was raised to 25°C. Then, 157.6 g of iodoethane (purity: 99%, industrial grade, supplied by Macklin Reagent Co., Ltd.) was added dropwise to the column, and the addition was completed in 2.5 h. The reaction was continued for another 1.5 h, and then the reaction was completed. The mass of the synthetic solution was 778 g. The molar ratio of the reaction materials, hexanediamine, sodium hydroxide, cetyltrimethylammonium chloride, and iodoethane, was 2:1.1:0.06:1.

[0060] (2) The synthetic liquid material in step (1) was separated into layers, and 613 g of a separated water layer and 164 g of a separated oil layer were obtained. The separated water layer was extracted four times with 333.6 g of dichloroethane at room temperature, and 385.7 g of an extracted oil layer was obtained. The remaining water layer was subjected to azeotropic distillation, and the dichloroethane and water azeotrope was reused in the extraction process. The azeotrope had a mass of 10.1 g and a composition of chloroform: 75.4%, water: 24.6%. The dichloroethane content of the remaining material after azeotropic distillation was 75 ppm.

[0061] (3) The separated oil layer 164 g and the extracted oil layer 385.7 g in step (2) were combined, and the combined solution was subjected to desolventization. The desolventization column temperature was controlled to be <100°C, and the absolute pressure was 760 mmHg. After the desolventization was completed, the dichloroethane content in the desolventization column was 40 ppm. The removed dichloroethane was reused in the extraction process in step (2), and the recovered dichloroethane at the top of the column had a mass of 320.2 g and a composition of dichloroethane: 99.69%, water: 0.3%. The desolventization column material was subjected to light desorption. The light desorption column temperature was controlled to be <99°C, and the absolute pressure was 12 mmHg. After the light desorption was completed, the hexanediamine content in the light desorption column was 320 ppm. The removed hexanediamine was reused in the column in step (1), and the recovered hexanediamine at the top of the column had a mass of 136.5 g and a composition of hexanediamine: 99.7%, dichloroethane: 0.2%. The light desorption column material was subjected to rectification. The rectification column temperature was controlled to be <120°C, and the absolute pressure was 12 mmHg. After the rectification was completed, the N-ethyl-1,6-hexanediamine content in the rectification column top was 99.1%, and the mass was 135.1 g. The product yield was 93%.

[0062] Example 3

[0063] (1) 210.9 g of hexanediamine (purity: 99%), 293.3 g of aqueous sodium hydroxide (wt: 15%), and 13.8 g of triethylbenzylammonium chloride (purity: 99%, industrial grade, same as the following) were put into a column, and the temperature was raised to 25°C. 110 g of bromoethane (purity: 99%) was added dropwise into the column, and the addition was completed in 4 h. Then, the reaction was continued for 0.5 h, and the reaction was completed. The synthetic liquid material weighed 628 g. The molar ratio of the reaction materials, hexanediamine, sodium hydroxide, triethylbenzylammonium chloride, and bromoethane, was 1.8:1.1:0.06:1.

[0064] (2) The synthetic liquid material in step (1) was separated into layers, and 468.3 g of a separated water layer and 158.7 g of a separated oil layer were obtained. The separated water layer was extracted three times with 370 g of toluene at room temperature, and 415.6 g of an extracted oil layer was obtained. The remaining water layer was subjected to azeotropic distillation, and the toluene and water azeotrope was reused in the extraction process. The azeotrope had a mass of 8.9 g and a composition of toluene: 78.05%, water: 21.95%. The toluene content of the remaining material after azeotropic distillation was 65 ppm.

[0065] (2) Combine the separated water layer 791 g and the extracted oil layer 420 g from step (1) and remove the solvent from the combined solution. The temperature of the column bottom is controlled at <100°C and the absolute pressure is 760 mmHg. After the removal of the solvent, the toluene content in the column bottom is measured to be 36 ppm. The removed toluene is recycled to the extraction process of step (2). The mass of the recovered toluene at the column top is 360.4 g, and the composition is toluene: 99.77%, water: 0.2%. The column bottom material is subjected to light removal. The temperature of the column bottom is controlled at <99°C and the absolute pressure is 12 mmHg. After the light removal, the hexanediamine content in the column bottom is measured to be 305 ppm. The removed hexanediamine is recycled to the column of step (1). The mass of the recovered hexanediamine at the column top is 122.1 g, and the composition is hexanediamine: 99.8%, toluene: 0.1%. The column bottom material is subjected to rectification. The temperature of the column bottom is controlled at <120°C and the absolute pressure is 12 mmHg. After the rectification, the N-ethyl-1,6-hexanediamine content in the column top is measured to be 99.1%, and the mass is 132.3 g. The product yield is 91%.

[0066] Example 4

[0067] Compared with Examples 1-3, the present example does not recycle the corresponding raw materials and solvents:

[0068] (1) Put 193.35 g of hexanediamine (purity: 99%), 586.7 g of aqueous caustic soda solution (wt: 7.5%), and 60.380 g of cetyltrimethylammonium chloride (purity: 99%) into a column. After the temperature is raised to 25°C, 173.3 g of iodoethane (purity: 99%) is added dropwise into the column. The dropwise addition is completed in 2.5 h, and the reaction is continued for another 1.5 h. Then the reaction is completed, and the mass of the synthesis liquid is 971 g. The molar ratio of the reaction materials, hexanediamine, caustic soda, cetyltrimethylammonium chloride, and iodoethane, is 1.5:1:0.15:1.

[0069] (2) Separate the synthesis liquid material in step (1) into layers, and obtain 791 g of a water layer and 178 g of an oil layer. At room temperature, 367.3 g of dichloroethane is used to extract the water layer in four times, and an extracted oil layer of 420 g is obtained.

[0070] (3) Combine the separated water layer 667.1 g and the separated oil layer 175.8 g from step (2), and then desolventize the combined solution, with the desolventizing column kettle temperature controlled at <100°C and the absolute pressure at 760 mmHg. After the desolventizing is completed, the dichloroethane content in the desolventizing column kettle is measured to be 42 ppm. The material in the desolventizing column kettle is then subjected to light desolventizing, with the light desolventizing column kettle temperature controlled at <99°C and the absolute pressure at 12 mmHg. After the light desolventizing is completed, the hexanediamine content in the light desolventizing column kettle is measured to be 299 ppm. The material in the light desolventizing column kettle is then subjected to rectification, with the rectification column kettle temperature controlled at <120°C and the absolute pressure at 12 mmHg. After the rectification is completed, the N-ethyl-1,6-hexanediamine content in the rectification column top is measured to be 99.2%, with the mass being 145.0 g and the product yield being 90.8%.

[0071] Comparative Example 1

[0072] In comparison with Example 1, no phase transfer catalyst is added in this comparative example:

[0073] (1) 292.9 g of hexanediamine (purity: 99%) and 440 g of aqueous caustic soda solution (wt: 10%) are warmed to 30°C, and then 110 g of bromoethane (purity: 99%) is added dropwise into the kettle, with the molar ratio of the reaction materials hexanediamine, caustic soda, and bromoethane controlled at 2.5:1.1:1. After 3 h of dropwise addition, the reaction is continued for another 1 h, and then the oil layer sample is taken for analysis. At this time, 35.2% of the bromoethane is still not completely reacted, and the reaction rate is relatively slow.

[0074] (2) The material in step (1) is separated into layers, and a total of 667.1 g of separated water layer and 175.8 g of separated oil layer are obtained. After the oil layer is left to stand overnight, white slurry is continuously generated at room temperature, and the next step cannot be performed.

[0075] Comparative Example 2

[0076] In comparison with Example 1, a small amount of catalyst is added in this comparative example:

[0077] (1) 292.9 g of hexanediamine (purity: 99%), 440 g of aqueous caustic soda solution (wt: 10%), and 1.2 g of triethylbenzylammonium chloride (purity: 99%) are put into a kettle, and then warmed to 30°C. After 110 g of bromoethane (purity: 99%) is added dropwise into the kettle, the molar ratio of the reaction materials hexanediamine, caustic soda, triethylbenzylammonium chloride, and bromoethane is controlled at 2.5:1.1:0.005:1. After 3 h of dropwise addition, the reaction is continued for another 1 h, and then the oil layer sample is taken for analysis. At this time, 10.5% of the bromoethane is still not completely reacted, and the reaction rate is relatively slow. The weight of the synthesis solution is 844.1 g.

[0078] (2) The synthetic liquid material in step (1) was separated into layers, and a total of 660.1 g of a separated water layer and 184.6 g of a separated oil layer were obtained. After the oil layer was left overnight, a small amount of white slurry was generated at room temperature, and the next step could not be performed.

[0079] Comparative Example 3

[0080] Compared with Example 1, the molar ratio of hexanediamine to bromoethane in this comparative example was 1.1:1:

[0081] (1) 128.9 g of hexanediamine (purity: 99%), 440 g of a tablet alkali aqueous solution (wt: 10%), and 9.2 g of triethylbenzylammonium chloride (purity: 99%) were put into a kettle, and the temperature was raised to 30°C. After 110 g of bromoethane (purity: 99%) was added dropwise into the kettle, the dropwise addition was completed in 3 h, and the reaction was continued for 1 h, and then the reaction was completed. The weight of the synthetic liquid was 688.1 g. The molar ratio of the reaction materials, hexanediamine, tablet alkali, triethylbenzylammonium chloride, and bromoethane, was 1.1:1.1:0.04:1.

[0082] (2) The synthetic liquid material in step (1) was separated into layers, and a total of 660.1 g of a separated water layer and 184.6 g of a separated oil layer were obtained. After the oil layer was left overnight, a small amount of white slurry was generated at room temperature, and the next step could not be performed.

[0083] (3) The separated oil layer 172.3 g in step (2) and the extracted oil layer 452.6 g were combined, and the combined solution was desolventized. The desolventization kettle temperature was controlled to be <100°C, and the absolute pressure was 760 mmHg. After the desolventization was completed, the chloroform content in the desolventization kettle was measured to be 24 ppm. The desolventization kettle material was subjected to a light removal, and the light removal kettle temperature was controlled to be <99°C, and the absolute pressure was 12 mmHg. After the light removal was completed, the hexanediamine content in the light removal kettle was measured to be 312 ppm. The light removal kettle material was subjected to rectification, and the rectification kettle temperature was controlled to be <120°C, and the absolute pressure was 12 mmHg. After the rectification was completed, the N-ethyl-1,6-hexanediamine content in the rectification kettle top was measured to be 99.2%, the mass was 104.1 g, and the product yield was 71.6%. The yield of this comparative example was lower than that of Example 1, and the rectification kettle had more impurities.

[0084] Comparative Example 4

[0085] Compared with Example 1, no tablet alkali aqueous solution was added during the synthesis of this comparative example, and the tablet alkali aqueous solution was added after the reaction:

[0086] (1) Put 292.9 g of hexamethylenediamine (purity: 99%), 9.2 g of triethylbenzylammonium chloride (purity: 99%) into a kettle, and warm up to 30°C. Then, add 110 g of bromoethane (purity: 99%) dropwise into the kettle, and control the molar ratio of hexamethylenediamine, triethylbenzylammonium chloride and bromoethane to be 2.5:0.04:1. After 3 h of dropwise addition, continue to react for 1 h. At this time, the material is turbid, and the sample analysis shows that 22.4% of bromoethane is not completely reacted, and the reaction rate is slow. The weight of the synthesis liquid is 412.1 g. After 3.5 h of continuous reaction, the reaction is completed.

[0087] (2) Add 440 g of aqueous sodium bicarbonate solution (wt: 10%) to the material in step (1), stir for 1 h, and then separate the layers. A total of 661.1 g of separated water layer and 189.9 g of separated oil layer are obtained. At room temperature, the separated water layer is extracted with 396.6 g of chloroform for three times, and a total of 448.5 g of extracted oil layer is obtained.

[0088] (3) Combine the separated oil layer 189.9 g in step (2) and the extracted oil layer 448.5 g, and then desolventize the combined solution. The desolventizing kettle temperature is controlled to be <100°C, and the absolute pressure is 760 mmHg. After desolventizing, the chloroform content in the desolventizing kettle is measured to be 26 ppm. Then, the desolventizing kettle material is subjected to light removal, and the light removal kettle temperature is controlled to be <99°C, and the absolute pressure is 12 mmHg. After light removal, the hexamethylenediamine content in the light removal kettle is measured to be 310 ppm. Then, the light removal kettle material is subjected to rectification, and the rectification kettle temperature is controlled to be <120°C, and the absolute pressure is 12 mmHg. After rectification, the N-ethyl-1,6-hexanediamine content in the rectification kettle top is measured to be 99.4%, the mass is 124.8 g, and the product yield is 86%. The yield of the comparative example is lower than that of example 1, and the reaction time is longer. The catalyst in the synthesis liquid is not dissolved, and does not play a phase transfer catalysis role.

[0089] The molar ratio of raw materials (hexamethylenediamine: sodium bicarbonate: phase transfer catalyst: haloethane), product content and product yield (calculated based on haloethane) of the above examples and comparative examples are shown in Table 1. As can be seen from example 1 and comparative examples 1 and 2, the addition of the phase transfer catalyst in the present application enables the synthesis reaction of N-ethyl-1,6-hexanediamine to be fast and complete. As can be seen from examples 1-4 and comparative example 3, the selection of each raw material and the molar ratio in the present application can ensure the yield of the product and reduce the generation of impurities. As can be seen from example 1 and comparative example 4, the addition of sodium bicarbonate during the reaction in the synthesis process of the present application can dissolve the phase transfer catalyst, and has the beneficial effect of making the reaction complete.

[0090] Table 1

[0091]

[0092] The above examples are set forth to illustrate the application and are not intended to limit the scope of the application. The application is described with reference to the typical embodiments, but it is understood that the language used is to convey what is believed to be the most practical and preferred aspects of the application, and the intent is not to limit the scope of the application to the details given. Modifications and variations are possible in the detail of the application as described, and other such modifications and variations are intended to fall within the scope of the application. While the application has been described in connection with specific methods, materials and embodiments, the application is not to be construed as limited to the particular examples disclosed. On the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the application.

Claims

1. A method for preparing N-ethyl-1,6-hexanediamine, comprising: (1) putting hexanediamine, aqueous caustic soda solution and phase transfer catalyst into a kettle, then adding halogenethane dropwise into the kettle, and continuing to react after stopping the dropwise addition; (2) separating the materials in the kettle of step (1) into a separated water layer and a separated oil layer; the separated water layer is subjected to an extraction process using a solvent at room temperature, and an extracted water layer and an extracted oil layer are obtained; (3) combining the separated oil layer and the extracted oil layer in step (2), and sequentially subjecting the combined oil layer to a desolventization process, a light component removal process and a rectification process to obtain N-ethyl-1,6-hexanediamine product; wherein the phase transfer catalyst is a quaternary ammonium salt.

2. The process for the production of N-ethyl-1,6-hexanediamine according to claim 1, characterized in that, The quaternary ammonium salt is selected from one or more of triethylbenzylammonium chloride, hexadecyltrimethylammonium chloride and hexadecyltriethylammonium chloride.

3. The process for the production of N-ethyl-1,6-hexanediamine according to claim 1, characterized in that, In the desolventization process in step (3), the desorbed solvent is reused in the extraction process in step (2).

4. The process for the production of N-ethyl-1,6-hexanediamine as claimed in claim 1, characterized in that, In the light component removal process in step (3), the desorbed hexanediamine is reused in the kettle in step (1).

5. The process for the production of N-ethyl-1,6-hexanediamine as claimed in claim 1, characterized in that, In step (1), the molar ratio of hexanediamine, caustic soda, phase transfer catalyst and halogenethane is 1.5-3:1-1.1:0.02-0.2:1; and the halogenethane is selected from one of bromoethane and iodoethane.

6. The process for the production of N-ethyl-1,6-hexanediamine according to claim 5, characterized in that, In step (1), the concentration of the aqueous caustic soda solution is 5-15 wt.%, the reaction temperature is 25-35℃, the time for dropwise addition of halogenethane is 2-4 h, and the time for continued reaction is 0.5-2 h.

7. The process for the production of N-ethyl-1,6-hexanediamine according to any one of claims 1 to 6, characterized in that, In step (2), the solvent is one of toluene, chloroform and dichloroethane; the mass ratio of the solvent to the separated water layer is 0.5-1:1; the extraction is performed 1-4 times; and in the azeotropic distillation process, the content of the solvent in the kettle residue after azeotropic distillation is controlled to be lower than 100 ppm.

8. The process for the production of N-ethyl-1,6-hexanediamine according to any one of claims 1 to 6, characterized in that, In the desolventization process in step (3), the content of the solvent in the kettle of the desolventization tower is controlled to be lower than 50 ppm; in the light component removal process, the content of hexanediamine in the kettle of the light component removal tower is controlled to be lower than 500 ppm; and in the rectification process, the content of the N-ethyl-1,6-hexanediamine product at the top of the tower is controlled to be higher than 99%.

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