Preparation method of liquid aliphatic secondary amine

Abstract

The invention discloses a preparation method of liquid aliphatic secondary amine, which comprises the following steps: 1, carrying out reductive alkylation reaction on aliphatic secondary amine, 3, 3-dimethyl-2-butanone and hydrogen under the action of a platinum-carbon catalyst and a sulfur-containing organic matter; and 2, filtering the reaction mixture, and carrying out vacuum distillation to obtain the target product. According to the method, hydrogen is used as a reducing agent, the process is green and environment-friendly, side reactions are few, and the purity of the prepared aliphatic secondary amine can reach 98% or above. The preparation method comprises the following steps: dissolving trace dimethyl sulfoxide in an ethanol solution to form a dimethyl sulfoxide-ethanol dispersion mixed solution, adding the dimethyl sulfoxide-ethanol dispersion mixed solution into a high-pressure hydrogenation reaction kettle, fully mixing the dimethyl sulfoxide-ethanol dispersion mixed solution with an obtained imine mixture, and adding a platinum-carbon catalyst. The preparation method of the liquid aliphatic secondary amine, which is disclosed by the invention, has the advantages of high catalyst selectivity and strong activity, and is suitable for producing the liquid aliphatic secondary amine.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of fine chemical industry, and relates to a preparation technology of a chain extender-aliphatic secondary diamine for high-performance polyurethane, in particular to a preparation method of liquid aliphatic secondary diamine. BACKGROUND

[0002] Polyurea is a kind of high-performance polymer material, which has the characteristics of high construction efficiency and excellent physical properties. Commonly used curing agents mainly include diethyl toluene diamine (DETDA), dimethylthio toluene diamine (DMTDA) and aliphatic polyether amine. The active groups of DETDA, DMTDA and polyether amine are primary amines, the reaction speed is fast, the operation time is short when the curing agent is used to prepare polyurea, and the requirement for spraying machinery is high. When the curing agent is a diamine containing a benzene ring structure, the polyurea prepared by using the diamine as a chain extender is easy to discolor under the irradiation of sunlight for a long time. The reaction activity of aliphatic secondary diamine is greatly reduced due to the steric hindrance effect of the amino group in the vicinity, thereby improving the operation performance of polyurea / polyurea. Meanwhile, the aliphatic amine does not contain a benzene ring in the molecular structure, and the polyurea prepared by using the aliphatic amine as a curing agent has good weather resistance. In view of the above advantages, the research and development of aliphatic secondary diamine with good anti-discoloration property and moderate activity is a research hotspot in the industry.

[0003] Regarding the preparation of aliphatic secondary diamine, patent US4126640A (General Mills Chemicals Company) reports a two-step process for preparing aliphatic secondary diamine: an aldehyde or ketone is first reacted with a polyamine (such as diethylene triamine) to form a ketimine or aldimine intermediate, and then the intermediate is reduced by hydrogenation at 145℃ under the action of a Raney nickel catalyst to obtain a polyamine containing a secondary amino group with low viscosity. Patent CN103261145 (SIKA Technology AG, Switzerland) introduces a method for synthesizing aliphatic secondary diamine containing two or more secondary amino groups by reacting a polyamine (polyether amine) with an aldehyde compound (2,2-dimethyl-3-lauryloxypropionaldehyde) to obtain an aldimine, and then performing a hydrogenation reaction. The patent does not mention the catalyst used and the product yield. Patent CN101891629A introduces a one-step process for preparing aliphatic secondary diamine using isophorone diamine, 4-methyl-2-pentanone / 4-heptanone and hydrogen as raw materials, and platinum sulfide as catalyst. The amount of ketone used is 8-15 times (molar ratio) of the primary amine, the hydrogen pressure is less than 1 MPa, the reaction temperature is 110-120℃, and the yield of secondary diamine is 95%-97%.

[0004] It can be known from the currently disclosed documents that the steric hindrance of raw materials has a great influence on the reduction alkylation reaction. When the steric hindance is large, the generation of diimine and the hydrogenation of diimine are difficult to proceed. For example, the reaction activity of ketone is lower than that of aldehyde due to the existence of steric hindance near the carbonyl group. The larger the steric hindance, the lower the activity. The reduction alkylation reaction can be carried out by one-step method or two-step method. Which method to be used needs to be determined by experiment according to the used raw materials, the difficulty of process, and the service life of catalyst. When the two-step method is used to prepare di-secondary amine, in order to make the reaction of amine and aldehyde / ketone to generate imine proceed fully, the aldehyde / ketone is generally excessive, and it is difficult to separate diimine from the product after the reaction is completed and then hydrogenation is carried out. Therefore, whether one-step method or two-step method is used, the problem of selectivity of catalyst to imine (carbon-nitrogen double bond) hydrogenation and aldehyde / ketone (carbon-oxygen double bond) hydrogenation is faced. When the activity of catalyst is high, the selectivity of hydrogenation is poor. Reducing the activity of catalyst can improve the reaction selectivity.

[0005] Platinum-carbon is a high-activity hydrogenation catalyst, which has a good catalytic effect on the hydrogenation of carbon-nitrogen double bond and carbon-oxygen double bond. However, due to the high activity of platinum-carbon, there is also a hydrogenolysis reaction in the process of catalyzing the reaction of amine and aldehyde / ketone to prepare di-secondary amine, which increases the content of by-products / impurities. In this case, in order to improve the selectivity of platinum-carbon catalyst for the preparation of di-secondary amine with high steric hindance, patent CN101891629A uses platinum sulfide catalyst for the synthesis of aliphatic di-secondary amine. However, for the preparation of di-secondary amine with high steric hindance, such as using 3,3-dimethyl-2-butanone as raw material, the catalytic effect of platinum sulfide is not ideal. How to catalyze the hydrogenation of carbon-nitrogen double bond to synthesize di-secondary amine with high steric hindance with high efficiency and high selectivity is a problem to be solved at present. SUMMARY

[0006] The technical problem to be solved by the present application is how to solve the problem that the selectivity and activity of catalyst are difficult to be considered in the production process of existing liquid aliphatic di-secondary amine, and a preparation method of liquid aliphatic di-secondary amine with high selectivity and high activity of catalyst is provided.

[0007] In order to solve the above technical problem, the preparation method of liquid aliphatic di-secondary amine comprises the following steps: (1) dehydrating and condensing aliphatic di-primary amine and 3,3-dimethyl-2-butanone under the action of benzene sulfonic acid anion exchange resin to generate a mixture of single-side imine and diimine, and obtaining the mixture of imine after water removal; (2) transferring the imine mixture to a high-pressure hydrogenation reactor, and carrying out reduction alkylation reaction under the condition that hydrogen is used as reducing agent and platinum-carbon is used as catalyst; (3) obtaining colorless to slightly yellow transparent aliphatic di-secondary amine with purity of more than 98% after cooling, filtering and distilling the mixture after hydrogenation is completed, and the feature is that the step (2) comprises the following sub-steps:

[0008] ①. The mixture of the imine obtained in (1) is cooled to 60-65℃ and transferred to the high-pressure hydrogenation reactor,

[0009] ②. 0.2%-1% of dimethyl sulfoxide by mass of the platinum-carbon catalyst is taken, and then the dimethyl sulfoxide is dissolved in 0.3-0.7 times the mass of ethanol of the raw material 3,3-dimethyl-2-butanone in step (1) to form a dimethyl sulfoxide-ethanol dispersion mixture,

[0010] ③. The dimethyl sulfoxide-ethanol dispersion mixture obtained in step (2) is first added to the high-pressure hydrogenation reactor, and then the platinum-carbon catalyst is added to the high-pressure hydrogenation reactor,

[0011] ④. The high-pressure hydrogenation reactor is then purged with nitrogen for 3 times, and then the internal gas of the high-pressure hydrogenation reactor is replaced with hydrogen for 3 times,

[0012] ⑤. The high-pressure hydrogenation reactor is then heated and kept at a temperature of 70-110℃, the pressure of the high-pressure hydrogenation reactor is set and kept in the range of 3.5-10 MPa, hydrogen is introduced, and the reduction alkylation reaction is carried out for 15-40 h.

[0013] In the present application, a small amount of dimethyl sulfoxide is first dissolved in an ethanol solution to form a dimethyl sulfoxide-ethanol dispersion mixture, which is then added to the high-pressure hydrogenation reactor, mixed with the mixture of the imine obtained in (1), and then the platinum-carbon catalyst is added. In this way, the dimethyl sulfoxide is fully dispersed before it meets the platinum-carbon catalyst, so that the local excess of dimethyl sulfoxide is avoided, the selectivity of the platinum-carbon catalyst is greatly improved, the generation of alcohol and hydrogenolysis by-products is reduced, and the activity of the platinum-carbon catalyst is not significantly reduced.

[0014] In a preferred technical solution, the aliphatic diprimary amine is a linear, branched or cyclic diamine with a carbon atom number of 6-10.

[0015] In a preferred technical solution, the aliphatic diprimary amine is isophorone diamine or decane diamine or nonane diamine or octane diamine or heptane diamine or cyclohexane diamine or hexane diamine.

[0016] In a preferred technical solution, the aliphatic diprimary amine is preferably isophorone diamine or 1,6-hexane diamine or 1,4-cyclohexane diamine.

[0017] In a preferred technical solution, the molar ratio of the diprimary amine to 3,3-dimethyl-2-butanone is 1:3-1:6, and the temperature is 80-120℃.

[0018] In a preferred technical solution, the addition amount of the platinum-carbon catalyst for imine hydrogenation is 2%-8% of the mass of the raw material diprimary amine.

[0019] The preferred technical solution is that the amount of platinum-carbon catalyst added for the hydrogenation of imine is 3% to 5% of the mass of the primary diamine.

[0020] The present invention provides a method for preparing liquid aliphatic di-secondary amines with high catalyst selectivity and strong activity, which is suitable for the production of liquid aliphatic di-secondary amines. Detailed Implementation

[0021] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0022] Example 1

[0023] The reactor was purged with nitrogen three times. Then, 300g of 3,3-dimethyl-2-butanone, 20g of acidic ion exchange resin (Amberlyst 15), and 170g of isophorone diamine were added to a 1L reactor. After purging with nitrogen twice, stirring was started and the temperature was set to 110℃. As the reaction temperature increased, the ketone and the generated water evaporated and separated into layers after condensation. The upper organic phase ketone was returned to the reactor to continue the reaction. After 5 hours, gas chromatography analysis showed that the selectivity of unilateral imine in the reaction solution was 38%, and the selectivity of diimine was 62%. The reaction solution also contained excess ketone. The reaction solution was cooled to 60–65 °C and transferred to a high-pressure reactor (which was purged with nitrogen beforehand). 120 g of ethanol, 0.031 g of dimethyl sulfoxide (DMSO, dissolved in ethanol beforehand), and 5.1 g of platinum-carbon catalyst were added. The reactor was purged with nitrogen three times, then purged with hydrogen three times, and then heated to 85 °C. The pressure was set at 5.5 MPa. Intermittent samples were taken for analysis during the reaction. After 27 hours, the conversion rate of isophorone diamine was 100%, the selectivity of the target product N,N'-di-(3,3-dimethyl-2-butyl)-isophorone diamine was 99.1%, and the amount of 3,3-dimethyl-2-butanone converted to 3,3-dimethyl-2-butanol was 1.8% of the ketone.

[0024] The reaction mixture was cooled, filtered, and the solvent and excess ketone / alcohol were removed to give 322.3 g of product.

[0025] Examples 2-6

[0026] The experimental procedure was the same as in Example 1, but the amount of raw materials and the reaction temperature and pressure were changed. The experimental results are as follows:

[0027] Table 1. Preparation of N,N'-bis-(3,3-dimethyl-2-butyl)-isophorone diamine

[0028]

[0029]

[0030] Note: (1) Ketone refers to 3,3-dimethyl-2-butanone;

[0031] (2) Catalyst mass refers to the mass percentage of catalyst Pt / C to raw material di-primary amine;

[0032] (3) Dimethyl sulfoxide mass refers to the mass percentage of dimethyl sulfoxide to catalyst;

[0033] From the experimental results, it can be seen that adding dimethyl sulfoxide in a specified range to the reaction liquid during hydrogenation is helpful to increase the selectivity of the target product di- secondary amine and reduce the content of by-products.

[0034] Example 7

[0035] The reaction kettle was purged with nitrogen for 3 times, then 3,3-dimethyl-2-butanone 601 g, acidic ion resin 20 g (Amberlyst 15), and liquid hexanediamine 116 g were added into a 1 L reaction kettle, which was purged with nitrogen for 2 times, then stirring was started and the temperature was set to 110°C. As the reaction temperature rose, the ketone and generated water vapor were evaporated and separated into two layers after condensation, the upper organic phase ketone was returned to the reaction kettle for continuous reaction. After 5 h, gas chromatography detection showed that the selectivity of the monoimine in the reaction liquid was 25%, the diimine content was 75%, and the reaction liquid also contained excess ketone. The reaction liquid was cooled to 60-65°C and transferred to a high-pressure reaction kettle (the reaction kettle was purged with nitrogen in advance), then ethanol 400 g, dimethyl sulfoxide 0.046 g (dimethyl sulfoxide was dissolved in ethanol in advance), platinum-carbon catalyst 4.64 g were added, the reaction kettle was purged with nitrogen for 3 times, then replaced with hydrogen for 3 times, heated to 100°C, and the pressure was set to 10 MPa. During the reaction, intermittent sampling analysis was performed. After 15 h, analysis and detection showed that the conversion rate of hexanediamine was 100%, the selectivity of N,N'-di-(3,3-dimethyl-2-butyl)-1,6-hexanediamine was 98.9%, and the amount of 3,3-dimethyl-2-butanone converted from the ketone was 2.4% of the ketone.

[0036] After the reaction mixture was cooled, filtered, and the solvent and excess ketone were removed, the product 266.5 g was obtained.

[0037] Examples 8-9

[0038] The experimental operation was the same as that in Example 1, except that the amount of raw material, reaction temperature, and pressure were changed, and the experimental results are as follows:

[0039] Table 2 Preparation of N,N'-di-(3,3-dimethyl-2-butyl)-1,6-hexanediamine

[0040]

[0041] Note: (1) The ketone in the table refers to 3,3-dimethyl-2-butanone;

[0042] (2) The catalyst mass refers to the mass percentage of the catalyst Pt / C to the raw material di-primary amine. The catalyst used in Example 8 is Pt(S) / C pretreated with H2S, and the catalyst used in Example 9 is Pd / C;

[0043] (3) The dimethyl sulfoxide mass refers to the mass percentage of dimethyl sulfoxide relative to the catalyst;

[0044] It can be seen from the experimental results that the platinum sulfide and palladium catalysts supported on activated carbon are not suitable for the preparation of di- secondary amine in the present patent.

[0045] Example 10

[0046] The reaction kettle was purged with nitrogen for 3 times, then 3,3-dimethyl-2-butanone 600 g, acidic ion resin 20 g (Amberlyst 15), liquid 1,4-cyclohexanediamine 114 g were added into a 1 L reaction kettle, which was purged with nitrogen for 2 times, then the stirring was started and the temperature was set to 110°C. As the reaction temperature rose, the ketone and the generated water vapor were evaporated and separated into two layers after condensation, the upper organic phase ketone was returned to the reaction kettle for continuous reaction. After 4 h, the selectivity of the monoimine in the reaction liquid was 27% and the selectivity of the diimine was 73% detected by gas chromatography, and the reaction liquid also contained excess ketone. The reaction liquid was cooled to 60-65°C and transferred to a high-pressure reaction kettle (the reaction kettle was purged with nitrogen in advance), then ethanol 200 g, dimethyl sulfoxide 0.023 g (the dimethyl sulfoxide was dissolved in ethanol in advance), platinum-carbon catalyst 5.7 g were added, which was purged with nitrogen for 3 times, then replaced with hydrogen for 3 times, heated to 85°C, and the pressure was set to 6.5 MPa. During the reaction, the samples were analyzed intermittently. After 28 h, the conversion rate of cyclohexanediamine was 100%, the selectivity of N,N'-di-(3,3-dimethyl-2-butyl)-1,4-cyclohexanediamine was 99.6%, and the amount of 3,3-dimethyl-2-butanone converted from the ketone to 3,3-dimethyl-2-butanol was 1.6% of the ketone.

[0047] After the reaction mixture was cooled, filtered, and the solvent and excess ketone were removed, the product 259.5 g was obtained.

[0048] Example 11

[0049] The operation of Example 10 was repeated to investigate the reuse of platinum-carbon catalyst, and the experimental results were as follows:

[0050] Table 3 Reusable times of catalyst

[0051]

[0052]

[0053] With the increase of the number of times of reuse of the catalyst, the time required for hydrogenation is prolonged.

[0054] From the experimental results, it can be seen that when the aliphatic diamine is isophorone diamine, hexanediamine or cyclohexanediamine, the ketone is 3,3-dimethyl-2-butanone, the imine is first generated from the diamine and the ketone, and then the imine is hydrogenated by using part of the poisoned platinum carbon as a catalyst, ethanol as a solvent and hydrogen as a reducing agent to prepare aliphatic disec-ondary amine, the selectivity of the disec-ondary amine is high, the side reaction of hydrogenation of the raw material ketone to alcohol is greatly reduced, and when the disec-ondary amine is prepared by using this method, the catalyst can be reused, thereby reducing the preparation cost of the disec-ondary amine.

[0055] In the synthesis process, dimethyl sulfoxide is added, dimethyl sulfoxide contains sulfur, which can cause the catalyst to be just right and suitable for the poisoning of the synthesis of the compound of the patent, and the balance of activity and selectivity is achieved.

[0056] The two-step method for preparing the disec-ondary amine can reduce the amount of ketone used as a solvent and the amount of alcohol generated by hydrogenation of the ketone.

[0057] The above description is only used to explain the preferred embodiments of the present application, and is not intended to limit the present application in any form, so any modification or change related to the present application made under the same inventive spirit should still be included in the scope intended to be protected by the present application.

Claims

1. A method for preparing a liquid aliphatic diamine, comprising the following steps: (1) An aliphatic diamine and 3,3-dimethyl-2-butanone are dehydrated and condensed under the action of benzenesulfonic acid anion exchange resin to generate a mixture of unilateral imine and diimine. After dehydration, a mixture of imines is obtained; (2) The imine mixture is transferred to a high-pressure hydrogenation reactor and a reduction alkylation reaction is carried out under the conditions of hydrogen as a reducing agent and platinum carbon as a catalyst; (3) After hydrogenation, the mixture is cooled, filtered, and distilled to obtain a colorless to slightly yellow transparent aliphatic diamine with a purity of more than 98%. The characteristic of step (2) is that it includes the following sub-steps: ①. Cool the mixture of imines obtained in step (1) to 60–65°C and transfer it to the high-pressure hydrogenation reactor. ②. Take 0.2% to 1% of the mass of the platinum-carbon catalyst in dimethyl sulfoxide, and then dissolve the dimethyl sulfoxide in 0.3 to 0.7 times the mass of the raw material 3,3-dimethyl-2-butanone in step (1) in ethanol to form a dimethyl sulfoxide-ethanol dispersion mixture. ③. First, add the dimethyl sulfoxide-ethanol dispersion mixture obtained in step ② into the high-pressure hydrogenation reactor, and then add the platinum-carbon catalyst into the high-pressure hydrogenation reactor. ④ Then purge the high-pressure hydrogenation reactor with nitrogen three times, and then replace the gas inside the high-pressure hydrogenation reactor with hydrogen three times. ⑤. Then, heat the high-pressure hydrogenation reactor and maintain the temperature range of 70 to 110°C. Keep the pressure of the high-pressure hydrogenation reactor in the range of 3.5 to 10 MPa. Introduce hydrogen gas and carry out the reduction alkylation reaction for 15 to 40 hours.

2. The method for preparing liquid aliphatic diamine according to claim 1, characterized in that: The aliphatic diamine is a straight-chain, branched, or cyclic diamine with 6 to 10 carbon atoms.

3. The method for preparing liquid aliphatic diamine according to claim 1, characterized in that: The aliphatic primary amine is isophorone diamine, decanediamine, nonanediamine, octanediamine, heptandiamine, cyclohexanediamine, or hexanediamine.

4. The method for preparing liquid aliphatic diamine according to claim 1, characterized in that: The aliphatic primary amine is preferably isophorone diamine, 1,6-hexanediamine, or 1,4-cyclohexanediamine.

5. The method for preparing liquid aliphatic diamine according to claim 1, characterized in that: The molar ratio of the primary amine to 3,3-dimethyl-2-butanone is 1:3 to 1:6, and the reaction temperature is 80 to 120°C.

6. The method for preparing liquid aliphatic diamine according to claim 1, characterized in that: The amount of platinum-carbon catalyst added for the hydrogenation of imine is 2% to 8% of the mass of the primary diamine.

7. The method for preparing liquid aliphatic diamine according to claim 1, characterized in that: The amount of platinum-carbon catalyst added for the hydrogenation of imine is 3% to 5% of the mass of the primary diamine.

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