Preparation method of liquid aromatic secondary amine

Abstract

The invention relates to a preparation method of liquid aromatic secondary amine, which comprises the following steps: (1) carrying out dehydration condensation on diethyltoluenediamine and aldehyde under the action of benzenesulfonic acid ion exchange resin to generate a mixture of monoimine and diimine, and layering to remove water; (2) transferring the imine mixture into a high-pressure hydrogenation reaction kettle, carrying out reductive alkylation reaction under the action of hydrogen as a reducing agent, ethanol, benzenesulfonic acid anion resin and a palladium carbon catalyst modified by the functionalized imidazole ionic liquid, and filtering and distilling the mixture after the reaction is ended, thereby obtaining the target product. The yellow target product liquid aromatic secondary amine is obtained, and the separated catalyst can be recycled. According to the preparation method of the liquid aromatic secondary amine, the activity of the catalyst is not easy to reduce, the preparation method is suitable for fluidized bed production and is economical and high in selectivity, and the produced liquid aromatic secondary amine is an excellent chain extender and can be used for preparing a polyurethane elastomer.

Description

Technical Field

[0001] The invention belongs to the field of fine chemicals, relates to a preparation technology of a high-performance polyurethane chain extender-aromatic di-secondary amine, and particularly relates to a preparation method of a liquid aromatic di-secondary amine. Background Art

[0002] Polyurethane elastomer is a new organic polymer chemical material synthesized with isocyanate, polyol and chain extender as main raw materials. It is known as the "fifth plastic" and is widely used in machinery manufacturing, transportation, sports, construction, medicine, electronic devices, military and aerospace, new energy, automobile and other industries. In the preparation of polyurethane elastomer, chain extender is the key to converting liquid polyurethane raw materials into solid finished products. It can effectively adjust the process parameters of polyurethane molding and improve the corrosion resistance, heat resistance, wear resistance, resilience, hardness and other physical and chemical comprehensive properties of the products. Therefore, the innovation of chain extender can often lead to great development of the polyurethane industry.

[0003] Compared with solid chain extenders, liquid chain extenders have the advantages of being easy to use and not requiring heating and melting. Common liquid chain extenders include 3,3'-diethyl-4,4'-diaminodiphenylmethane (MOEA), diethyltoluenediamine (DETDA), dimethylthiotoluenediamine (DMTDA), aliphatic polyetheramines, etc. However, these chain extenders have a common feature, that is, they have a fast reaction speed and high requirements for operating equipment. Therefore, the development of liquid, low-reactivity, high-performance chain extenders, such as liquid disecondary amines, is the research and development focus of the polyurethane industry.

[0004] The most commonly used process for preparing di-secondary amines is the reduction alkylation process. Commonly used catalysts include precious metal catalysts such as palladium, platinum, and rubidium supported on activated carbon and alumina. However, precious metal catalysts are easily poisoned and deactivated under certain conditions, which to a certain extent pushes up the production cost of di-secondary amines. Patent CN101891629A introduces a process for preparing aromatic di-secondary amines in the next step by using 4,4'-methylenebis(2,6-diethylaniline), diethyltoluenediamine, methyl ethyl ketone, acetone, etc. under the action of platinum sulfide / carbon catalyst, wherein the amount of ketone is 12 to 55 times (molar ratio) of diamine, which greatly exceeds the theoretical amount of ketone. In the one-step method, ketone is used as both a raw material and a solvent. After the reaction is completed, the selectivity of di-secondary amine is between 95% and 97%. Ketone is hydrogenated under the action of platinum sulfide catalyst to generate a large amount of alcohol; a two-step method is adopted: first, diprimary amine and ketone are generated into diimines, and then hydrogenated. It takes 28 hours to completely convert diethyltoluenediamine into the corresponding diimine, and the production efficiency needs to be improved. CN101759572B introduces a continuous process for synthesizing disecondary amines using isophorone diamine and acetone as raw materials, wherein isophorone diamine is used at 100 g / h, acetone is used at 135 g / h, and hydrogen is 100% excessive, and a palladium carbon catalyst with a palladium content of 1% is fixed in a pipeline to prepare disecondary amines in one step at 2000 psig (about 14 MPa) and 150° C. The reaction conditions are harsh.

[0005] As for the currently known commercially available di-secondary amine chain extenders, there is only one in China, 4,4'-di(N-isobutylamino)diphenylmethane, and the production is small and the price is high. The reason is that the precious metal catalyst is easily poisoned and deactivated, and the service life is short. In this case, how to extend the service life of the catalyst, improve production efficiency, and reduce the production cost of di-secondary amines is an urgent problem to be solved in the production field of chain extender di-secondary amines. Summary of the invention

[0006] The technical problem to be solved by the present invention is how to solve the problem that the noble metal catalyst is easily poisoned and deactivated and has a short service life in the production process of the existing liquid aromatic di-secondary amine, and to provide a preparation method of liquid aromatic di-secondary amine which is economical, highly selective, suitable for a fluidized bed and is not easy to reduce the activity of the catalyst.

[0007] In order to solve the above technical problems, the present invention provides a method for preparing a liquid aromatic disecondary amine which is not easy to reduce the activity of the catalyst, comprising the following steps:

[0008] ①. Diethyltoluenediamine and aldehyde are dehydrated and condensed under the action of benzenesulfonic acid ion exchange resin to form a mixture of monoimine and diimine, and water is removed by layering to obtain an imine mixture;

[0009] During the reaction, the steam formed by aldehyde and water is condensed and separated, and the organic phase is returned to the kettle. After 6 to 10 hours of reaction, the conversion rate of diethyltoluenediamine is greater than 99%, the selectivity of monoimine in the imine mixture is 20% to 40%, and the selectivity of diimine is 60% to 80%. Stirring is stopped, and the mixture is allowed to stand and separate to remove the water generated during the reaction. Benzenesulfonic acid anion resin can promote the reaction of amine and carbonyl groups to generate imines, and its dosage is 8% to 15% of the mass of diethyltoluenediamine.

[0010] ②. The imine mixture is then transferred to a high-pressure hydrogenation reactor, and the imine mixture is subjected to a reduction alkylation reaction under the action of a reducing agent, hydrogen, ethanol, benzenesulfonic acid anion resin, and a palladium-carbon catalyst modified with a functionalized imidazolium ion liquid. After the reaction, the mixture is filtered and distilled to obtain a yellow target product, a liquid aromatic disecondary amine, and the separated catalyst is recovered for reuse.

[0011] When noble metal catalysts are used for reduction alkylation to prepare di-secondary amines, palladium has the advantages of lower price, no hydrogenolysis, and less by-products compared to highly active platinum. Therefore, the present invention uses palladium-carbon catalysts as the first choice when preparing highly sterically hindered di-secondary amines using diethyltoluenediamine and aliphatic aldehydes as raw materials. A small amount of ethanol is added during hydrogenation in this patent, and the mass of the ethanol used is 0.3 to 1 times the mass of the aldehyde.

[0012] The reducing agent used in the preparation of di-secondary amines in this patent is hydrogen, and the hydrogenation catalyst is palladium supported on activated carbon. The palladium content can be 3%, 5% or 10%, and 5% is preferred in this patent; the carrier used for the catalyst is activated carbon doped with nitrogen and modified with functionalized 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid. The preparation of the palladium / carbon catalyst can refer to the relevant content in "Textbook of practical organic chemistry", and the amount of palladium-carbon catalyst used is 3% to 5% of diethyltoluenediamine.

[0013] The hydrogenation reaction occurs at the contact surface between the catalyst and the liquid, and the hydrogenation reaction is an exothermic reaction. The ethanol added in the present invention works synergistically with the palladium carbon catalyst modified with the functionalized imidazolium ionic liquid to dilute and slow down the heat released by the hydrogenation reaction, effectively preventing the catalyst surface temperature from overheating, reducing the agglomeration of the catalyst, and greatly extending the catalyst activity and life.

[0014] The present invention adds benzenesulfonic acid anion resin when preparing diimine, and the acidic resin can promote the reaction of amine and carbonyl to generate imine. The present invention adopts a two-step method to first prepare the imine mixture, and then hydrogenates to greatly reduce the generation of by-product alcohol.

[0015] The preferred technical solution is: the raw material aldehyde is a straight-chain aliphatic aldehyde or a branched aliphatic aldehyde with 3 to 10 carbon atoms.

[0016] The preferred technical solution is: the raw material aldehyde is propionaldehyde or butyraldehyde or 2-methylpropionaldehyde or valeraldehyde or 2-methylbutyraldehyde or 3-methylbutyraldehyde or heptanal.

[0017] The preferred technical solution is: the molar ratio of the diethyltoluenediamine to the aldehyde is 1:2.5 to 1:5.

[0018] The preferred technical solution is: the reaction temperature of diethyltoluenediamine and aldehyde is 60-120°C, the mixed vapor of aldehyde and water is condensed and layered in a water separator during the reaction, and the organic phase is returned to the container to participate in the reaction.

[0019] The preferred technical solution is that the selectivity of the monoimine in the imine mixture is 20% to 40%, and the selectivity of the diimine is 60% to 80%.

[0020] The preferred technical solution is: the content of palladium in the palladium-carbon catalyst is 3% or 5% or 10%.

[0021] The preferred technical solution is: the palladium content in the palladium-carbon catalyst is 5%.

[0022] The preferred technical solution is: the carbon carrier used for the palladium-carbon catalyst is obtained by doping with nitrogen elements and modifying with a functionalized imidazolium ionic liquid, and the functionalized imidazolium ionic liquid is 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid or 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid or 1-propyl-3-methylimidazolium chloride ionic liquid or 1-propyl-3-methylimidazolium bromide ionic liquid.

[0023] The preferred technical scheme is: the amount of the palladium carbon catalyst is 3% to 5% of diethyltoluenediamine, the hydrogenation temperature is 80 to 110° C., the pressure is 3.5 to 7 MPa, and the reaction time is 5 to 10 hours; the imidazolium ionic liquid is 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid.

[0024] The preparation method of the liquid aromatic di-secondary amine of the present invention is not easy to reduce the activity of the catalyst, is suitable for fluidized bed production, is economical and has high selectivity. The produced liquid aromatic di-secondary amine is an excellent chain extender, can be used to prepare polyurethane elastomers, can effectively adjust the process parameters of polyurethane molding, and improve the corrosion resistance, heat resistance, wear resistance, resilience, hardness and other physical and chemical comprehensive properties of the products. DETAILED DESCRIPTION

[0025] Example 1: The following is a specific example of the reaction of diethyltoluenediamine and 2-methylbutyraldehyde to illustrate the implementation of the present invention. People familiar with this technology can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0026] Example 1

[0027] 1783 g of diethyltoluenediamine and 300 g of benzenesulfonic acid exchange resin were added to a 10 L reactor. After nitrogen purging, stirring was started and the temperature was raised. 3445 g of 2-methylbutyraldehyde was added dropwise. The reaction temperature was set to 110° C. As the temperature increased, steam was observed to evaporate and enter the condenser. The condensed steam was separated into layers in the water separator, and the upper organic phase was returned to the reactor. Samples were taken at intervals during the reaction and the yield of diimine was analyzed. After 6 hours, the growth rate of diimine slowed down. At this time, the conversion rate of diethyltoluenediamine was 99.5%, the selectivity of unilateral imine was 21%, and the selectivity of diimine was 78%. Stirring was stopped and the layers were allowed to stand to separate. A total of 4768 g of organic phase was obtained. The acidic resin obtained after filtering the lower aqueous phase was put into the hydrogenation reactor.

[0028] Example 2

[0029] The high-pressure hydrogenation reactor was purged with nitrogen three times, 100 g of imine organic phase, 15 g of ethanol, 1.5 g of palladium carbon catalyst, and 6 g of benzenesulfonic acid exchange resin were added, the reactor was closed and purged with nitrogen three times, and then the nitrogen was replaced with hydrogen three times, the hydrogen pressure was set to 4 MPa, the temperature was 93°C and stirring was turned on, sampling was taken at intervals during the reaction, and after 8 hours, the selectivity of N, N'-di(2-methyl-butyl)-diethyltoluene disecondary amine was detected to be 99.4%, and the amount of 2-methylbutanal converted to 2-methylbutanol was 3.6% of the aldehyde. The hydrogenation and stirring were stopped and the pressure was released, the hydrogen was replaced with nitrogen three times, and the reaction liquid was pressed into a closed filter under a slightly positive pressure condition for filtration, and the filtrate was distilled to remove ethanol, water, 2-methylbutanal and 2-methylbutanol, respectively, to finally obtain 60.2 g of the target product disecondary amine with a yellow color, and the catalyst was collected and reused.

[0030] Example 3

[0031] The diimine prepared in Example 1 was used, and the imine hydrogenation operation was the same as in Example 2, the only difference being that the catalyst used for hydrogenation was an unmodified palladium / carbon catalyst. The catalyst recycling results are shown in the following table.

[0032] Example 4

[0033] The experimental operation is the same as Example 2, except that the catalyst used for hydrogenation is an unmodified palladium-carbon catalyst, and no ethanol is added during the hydrogenation process. The catalyst recycling results are shown in the following table.

[0034]

[0035]

[0036] The experimental results show that the activity of the palladium / carbon catalyst modified with nitrogen-doped carrier carbon and functionalized pyridinium ionic liquid has not decreased significantly after 30 uses. Compared with the unmodified palladium-carbon catalyst, the service life of the modified palladium-carbon catalyst is greatly extended; the addition of ethanol can extend the life of the catalyst during use; the two-step method of first preparing the imine mixture and then hydrogenating it can greatly reduce the production of by-product alcohols.

[0037] The above description is only used to explain the preferred embodiments of the present invention, and is not intended to limit the present invention in any form. Therefore, any modifications or changes made to the present invention under the same inventive spirit should still be included in the scope of protection intended by the present invention.

Claims

1. A method for preparing a liquid aromatic di-secondary amine, characterized in that: The steps include: ①. Diethyltoluenediamine and aldehyde are dehydrated and condensed under the action of benzenesulfonic acid ion exchange resin to form a mixture of monoimine and diimine, and water is removed by layering to obtain an imine mixture; ②. The imine mixture is then transferred to a high-pressure hydrogenation reactor, and a reduction alkylation reaction is carried out under the action of hydrogen as a reducing agent, ethanol, benzenesulfonic acid anion resin and a palladium carbon catalyst modified with a functionalized imidazolium ion liquid. After the reaction, the mixture is filtered and distilled to obtain a yellow target product, a liquid aromatic disecondary amine, and the separated catalyst is recovered for reuse.

2. The method for preparing a liquid aromatic disecondary amine according to claim 1, characterized in that: The raw material aldehyde is a straight-chain aliphatic aldehyde or a branched aliphatic aldehyde having 3 to 10 carbon atoms.

3. The method for preparing a liquid aromatic di-secondary amine according to claim 2, characterized in that: The raw material aldehyde is propionaldehyde or butyraldehyde or 2-methylpropionaldehyde or valeraldehyde or 2-methylbutyraldehyde or 3-methylbutyraldehyde or heptaldehyde.

4. The method for preparing a liquid aromatic di-secondary amine according to claim 1, characterized in that: The molar ratio of the diethyltoluenediamine to the aldehyde is 1:2.5 to 1:

5.

5. The method for preparing a liquid aromatic di-secondary amine according to claim 1, characterized in that: The reaction temperature of diethyltoluenediamine and aldehyde is 60-120° C. During the reaction, the mixed vapor of aldehyde and water is condensed and separated into layers in a water separator, and the organic phase is returned to the container to participate in the reaction.

6. The method for preparing a liquid aromatic di-secondary amine according to claim 1, characterized in that: The selectivity of the monoimine in the imine mixture is 20% to 40%, and the selectivity of the diimine is 60% to 80%.

7. The method for preparing a liquid aromatic di-secondary amine according to any one of claims 1 to 6, characterized in that: The palladium content in the palladium-carbon catalyst for imine hydrogenation is 3%, 5% or 10%.

8. The method for preparing a liquid aromatic di-secondary amine according to claim 7, characterized in that: The content of palladium in the palladium-carbon catalyst is 5%.

9. The method for preparing a liquid aromatic disecondary amine according to claim 8, characterized in that: The carbon carrier used for the palladium-carbon catalyst is obtained by doping with nitrogen elements and modifying with a functionalized imidazolium ionic liquid, wherein the functionalized imidazolium ionic liquid is 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid or 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid or 1-propyl-3-methylimidazolium chloride ionic liquid or 1-propyl-3-methylimidazolium bromide ionic liquid.

10. The method for preparing a liquid aromatic di-secondary amine according to claim 9, characterized in that: The dosage of palladium carbon catalyst for imine hydrogenation is 3% to 5% of diethyltoluenediamine, the hydrogenation temperature is 80 to 110° C., and the pressure is 3.5 to 7 MPa; the imidazolium ionic liquid is 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid.

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