A method for preparing low-reaction HMDA in a continuous reactor

Abstract

The present invention provides a method for continuously producing 4,4'-diaminodicyclohexylmethane, comprising the following steps: (1) catalyst activation modification: adding a certain amount of solvent, modifier and catalyst into a reactor, performing activation modification reaction to activate and modify the catalyst; (2) 4,4'-HMDA preparation: continuously injecting a raw material solution into the reactor for reaction. In the method of the present invention, the MDA conversion rate is greater than 99%, the HMDA yield reaches more than 88%, the anti-anti content is 16% to 20%, i.e., the PACM20 product; and the catalyst mass space velocity can reach 12-28gMDA / gCAT*h, and the deactivated catalyst can be restored to activity by special treatment.

Description

Technical Field

[0001] The invention belongs to the field of organic synthesis and relates to a method for continuously producing 4,4'-diaminodicyclohexylmethane (HMDA) in a kettle. Background Art

[0002] 4,4'-HMDA is mainly produced by high-pressure catalytic hydrogenation of 4,4'-MDA. It has three configurational isomers, namely cis-cis, cis-trans and trans-trans isomers. The isomer content distribution of 4,4'-HMDA in equilibrium state is 50% trans-trans, 43% cis-trans and 7% cis-cis. Among the three isomers, the trans-trans isomer is the most thermodynamically stable, and high temperature reaction is conducive to its formation. The mixture of these three isomers is obtained after high-pressure catalytic hydrogenation of 4,4'-MDA.

[0003] According to the different isomer content, the product with the content of trans-trans isomer less than 24%, namely PACM20, is not only used as an amine epoxy curing agent, but also an important intermediate in the polyurethane and polyamide industry. It is the raw material for preparing a new generation of excellent anti-aging polyurethane - 4,4'-dicyclohexylmethane diisocyanate (HMDI). It has unique yellowing resistance and weather resistance. Its application areas include electromechanical, shipbuilding, civil engineering and textiles. In recent years, its demand in the domestic and foreign markets has increased year by year. When the content of trans-trans is about 50%, namely PACM50, it is mainly used to prepare aliphatic polyamide resins, which can be used to react with sebacic acid or adipic acid to produce nylon.

[0004] The raw material of 4,4'-HMDA, 4,4'-MDA, contains two benzene rings. Under the thermodynamic equilibrium theory, HMDA with a trans-trans isomer content of 50% is easiest to prepare, and the three stereoisomers of trans-trans, cis-trans, and cis-cis are difficult to separate. In order to obtain 4,4'-HMDA with a low trans-trans isomer content, special means must be used to break through the limitations of this thermodynamic equilibrium.

[0005] The following is the hydrogenation process of 4,4'-MDA: 4,4'-MDA is hydrogenated in the first step to obtain a partially hydrogenated product 4,4'-H6MDA, which is then further hydrogenated to obtain 4,4'-H 12 MDA, the 4,4'-HMDA mentioned above:

[0006]

[0007] EP0231788 discloses an improved intermittent hydrogenation process, using THF as solvent, bimetallic rhodium and ruthenium components as catalysts, at 170-195°C and 700-1500psig, to prepare HMDA with an anti-antibody content of 17-24%, but does not solve the problem of performance degradation after a long period of use of the catalyst. CN103265438 discloses a method for preparing HMDA by hydrogenating diaminodiphenylmethane, when the catalyst activity decreases, the catalyst activity is regenerated by reducing the catalyst hydrogen consumption rate, and since 2,4'-HMDA is introduced into the product during the catalyst regeneration process, a post-processing process needs to be added to separate the product. Patent CN110204447 discloses a method for regenerating a catalyst in the continuous production process of 4,4'-diaminodicyclohexylmethane. When the conversion rate of the raw material MDA drops to 90-95%, the feed is switched to liquid ammonia-alkali metal salt solution-liquid ammonia replacement washing, followed by high-temperature modification. The technical process is cumbersome, requires frequent switching of feeds, and generates a large amount of wastewater.

[0008] US20020198409 discloses a continuous reduction process of MDA, in which alcohols are used as solvents and supported ruthenium is used as catalyst in a series of suspension reactors formed by continuous bubbling towers, wherein the ruthenium metal content is 1-10%, and the catalytic reaction is carried out at 130-200°C and 50-400bar. When the catalyst reaction activity decreases, it is necessary to stop the process and use a solvent to wash the catalyst. US5196594 discloses a continuous hydrogenation reduction process of MDA, which uses supported ruthenium as a catalyst in at least one fixed bed reactor at 100-190°C and 50-350bar to prepare HMDA with an anti-antibody content of 18.5-23.5%. Although the yield of HMDA is relatively high, reaching 93.7%, the amount of raw materials processed by the catalyst per hour is only 0.04-0.1Kg MDA / Kg Cat, which restricts the efficiency of industrial production. Patent US9873658 discloses a method for preparing low-reverse HMDA using Ru / Al2O3 as a catalyst in a fixed bed reactor. The reaction temperature is as low as 80°C, and the catalyst can process 0.04kg MDA / kg cat per hour. However, the conversion rate is less than 70%, and the selectivity is only 60%.

[0009] In summary, the existing technology has the following defects:

[0010] Most MDA continuous hydrogenation processes use fixed-bed reactors. The amount of raw materials processed per unit mass of catalyst per unit time is low, and the catalyst processing capacity per hour is usually 0.04-0.1kg MDA / kg cat, and the conversion rate and selectivity are not high. At the same time, as the use time increases, the catalyst gradually deactivates, and the regeneration scheme is complicated, requiring additional process flow, which increases the workload, or high-temperature re-modification using liquid ammonia and other forms, which produces a large amount of wastewater. The continuous kettle process generally requires multiple kettles in series to ensure the conversion rate of the raw materials, and because the catalyst is in the same powder catalyst as the intermittent reactor, its life is relatively short. Summary of the invention

[0011] The purpose of the present invention is to provide a method for producing low-reverse HMDA by continuous autoclave reaction with simple process operation, low production cost and high efficiency, in view of the deficiencies in the prior art, wherein the MDA conversion rate is greater than 99%, the HMDA yield reaches more than 88%, the reverse content is 16% to 20%, i.e., the PACM20 product; and the catalyst mass space velocity can reach 12-28gMDA / gCAT*h, and the deactivated catalyst can be restored to activity by special treatment.

[0012] In order to achieve the purpose of the present invention, the technical solution adopted is:

[0013] A scheme for producing low-reverse 4,4'-HMDA by continuous batch reaction using 4,4'-MDA as raw material, comprising:

[0014] During the entire catalyst life cycle, the reaction is divided into three stages:

[0015] (1) The first stage: The first stage is the catalyst activation modification reaction, in which a certain amount of solvent, modifier and catalyst are added to the continuous stirring reactor;

[0016] Wherein, the solvent is selected from any one or a combination of at least two of tetrahydrofuran, cyclohexane, methanol, ethanol, isopropanol, 2-butanol or methylcyclohexane;

[0017] The amount of solvent added is 50-80 times the mass of the catalyst;

[0018] The modifier is divided into two components, a and b;

[0019] The a component is 4,4'-MDA and water, wherein the mass ratio of 4,4'-MDA to water is 0.1-2.5, and the addition amount of the a component is 10-50 times the mass of the catalyst, preferably 30 times;

[0020] The b component is tetrahydrofurfurylamine, and the addition amount of the b component is 1% to 10% of the catalyst mass, preferably 5%;

[0021] The catalyst is a supported catalyst, comprising a combination of an active metal and a carrier;

[0022] The active metal includes any one or a combination of at least two of Pt, Rh, and Ru, preferably Rh;

[0023] The carrier comprises any one of alumina, activated carbon, lithium aluminate, and silicon oxide, or a combination of at least two of them, preferably alumina;

[0024] The active metal content is 2-6 wt%, preferably 4-5 wt%, based on the weight of the supported catalyst;

[0025] Preferably, the supported catalyst is Rh / Al2O3;

[0026] The modification reaction temperature is 120-200°C, the pressure is 3-8MPa, and the time is 2-12h, preferably 170°C, 6MPa, 6h;

[0027] This step forms a water-in-oil or oil-in-water structure on the catalyst surface, which accelerates the desorption of the product, reduces the generation of heavy components, and prolongs the life of the catalyst.

[0028] (2) The second stage: The second stage is the reaction stage. After the activation and modification reaction is completed, the reaction is carried out by continuously pumping the raw material solution into the reaction chamber through the feed pump.

[0029] The concentration of 4,4'-MDA in the raw material solution is 30wt%-60wt%, and the solvent is the same as the first stage;

[0030] The reaction temperature is 120-200°C, and the pressure is 3-8MPa, preferably 170°C and 6MPa;

[0031] The feed rate of the raw material solution is calculated based on the mass of the catalyst in the reactor, and the feed rate maintains the catalyst mass space velocity of 12-28 gMDA / gCAT*h.

[0032] (3) The third stage: The third stage is the stage of recovering the activity of the deactivated catalyst. When the conversion rate of the raw material 4,4'-MDA drops to 90-95%, the operation of the first stage is repeated to recover the activity of the catalyst and continue the reaction.

[0033] The beneficial technical effects achieved by the present invention are:

[0034] (1) The present invention provides a process scheme for the continuous production of HMDA in a kettle, which maintains a high raw material conversion rate and a high product yield (MDA conversion rate>99%, HMDA yield of more than 88%), while the mass space velocity of the catalyst can reach 12-28gMDA / gCAT*h, greatly improving the production efficiency.

[0035] (2) After the catalyst is deactivated, it can be restored to its initial activity by regeneration. The regeneration scheme is simple and easy to operate without introducing any extra impurities. DETAILED DESCRIPTION

[0036] In order to further illustrate the present invention, experiments are carried out as follows according to the above method, but the listed processes and data are not meant to limit the scope of the present invention.

[0037] The experimental results were analyzed by gas chromatography.

[0038] Unless otherwise specified, the raw materials used in the following examples or comparative examples are all commercially available industrial grade conventional raw materials.

[0039] The main raw materials and testing equipment information are as follows:

[0040] The raw material of 4,4'-diaminodiphenylmethane (4,4'-MDA) comes from Wanhua Chemical with a purity greater than 99%.

[0041] Tetrahydrofurfurylamine and tetrahydrofuran were purchased from Beijing Inokai Technology Co., Ltd. with analytical grade.

[0042] The catalyst was purchased from Johnson Matthey.

[0043] The gas chromatograph was Agilent 7890B, DB-5 capillary column, FID detector temperature was 300℃, the initial column temperature was 50℃, increased to 300℃ at 10℃ / min, and stayed for 20min. 12 MDA is the trans-isomer content, and “others” are mainly light components and some incomplete hydrogenation products.

[0044] Example 1

[0045] Add 300g of tetrahydrofuran solvent, 4.5g of 4wt% Rh / Al2O3 catalyst, 135g of modifier component a (67.5g of MDA and 67.5g of H2O), and 0.225g of component b tetrahydrofurfurylamine into a continuous stirring reactor. Replace with 1MPa of N2 three times, then replace with 1MPa of H2 three times, and then add H2 to 1MPa. When the modification activation temperature reaches 170℃, maintain the pressure at 6MPa and perform modification activation for 6h.

[0046] Preparation of HMDA: 4,4'-MDA was prepared into a tetrahydrofuran solution with a concentration of 45 wt%, the reaction temperature was 170°C, the reaction pressure was 6 MPa, and the catalyst mass space velocity was 12 gMDA / gCAT*h.

[0047] When the conversion rate dropped to about 95%, the modification and activation operation was repeated and then the reaction was continued.

[0048] The results are as follows:

[0049]

[0050] Example 2

[0051] When the conversion rate of Example 1 dropped to about 95%, the catalyst was activated and modified. The modification reaction conditions were different from those of Example 1 as follows: 45 g of modifier component a (including 4.5 g of MDA and 40.5 g of H2O), 0.135 g of component b, and the modification temperature was 160°C, 5 MPa, and 8 h.

[0052] Then, the preparation of HMDA was continued according to the conditions of Example 1.

[0053] The results are as follows:

[0054]

[0055] Example 3

[0056] When the conversion rate of Example 2 dropped to about 95%, the catalyst was activated and modified. The modification reaction conditions were different from those of Example 1 as follows: 225 g of modifier component a, of which MDA was 157.5 g, H2O was 67.5 g, component b was 0.36 g, and the modification temperature was 190°C, 7 MPa, and 5 h.

[0057] Then, the preparation of HMDA was continued according to the conditions of Example 1.

[0058] The results are as follows:

[0059]

[0060] Comparative Example 1

[0061] When the conversion rate of Example 3 dropped to about 95%, the catalyst was activated and modified. The modification reaction conditions were different from those of Example 1 as follows: 225 g of modifier component a, of which MDA was 157.5 g, and H2O was 67.5 g. Component b was not added. The modification temperature was 190°C, 7 MPa, and 5 h.

[0062] Then, the preparation of HMDA was continued according to the conditions of Example 1.

[0063] The results are as follows:

[0064]

[0065] Comparative Example 2

[0066] When the conversion rate of comparative example 1 drops to about 95%, the catalyst is subjected to activation modification reaction. The modification reaction conditions are different from those of example 1 in that no modifier a and b components are added, and the modification temperature is 190° C., 7 MPa, and 5 h.

[0067] Then, the preparation of HMDA was continued according to the conditions of Example 1.

[0068] The results are as follows:

[0069]

[0070] Comparative Example 3

[0071] The catalyst of comparative example 2 which was operated for 1900 h was subjected to a modification reaction. The modification reaction conditions were different from those of example 1 as follows: the modifier component a was 225 g of MDA, no H2O was added, component b was 0.36 g, and the modification temperature was 190°C, 7 MPa, and 5 h.

[0072] Then, the preparation of HMDA was continued according to the conditions of Example 1.

[0073] The results are as follows:

[0074]

[0075] Example 4

[0076] The catalyst of comparative example 3 which was operated for 2000 h was subjected to a modification reaction. The modification reaction conditions were different from those of example 1 as follows: 45 g of modifier component a (including 4.5 g of MDA and 40.5 g of H2O), 0.135 g of component b, and the modification temperature was 160°C, 5 MPa, and 8 h.

[0077] Then, the preparation of HMDA was continued according to the conditions of Example 1.

[0078] The results are as follows:

[0079]

Claims

1. A method for activating and modifying a catalyst for preparing 4,4'-HMDA, comprising: A certain amount of solvent tetrahydrofuran, a modifier and a catalyst are added into the reaction kettle to carry out activation and modification reaction; Wherein, the modifier is divided into two components, a and b; The a component is 4,4'-MDA and water, wherein the mass ratio of 4,4'-MDA to water is 0.1-2.5, and the addition amount of the a component is 10-50 times the mass of the catalyst; The component b is tetrahydrofurfurylamine, and its addition amount is 1% to 10% of the catalyst mass; The catalyst is a supported catalyst Rh / alumina.

2. The method according to claim 1, wherein: The amount of solvent added is 50-80 times the mass of the catalyst.

3. The method according to claim 1, wherein: The content of Rh is 2-6 wt % based on the weight of the supported catalyst.

4. The method according to any one of claims 1 to 3, wherein: The modification reaction temperature is 120-200°C, the pressure is 3-8MPa, and the time is 2-12h.

5. A method for continuously producing 4,4'-diaminodicyclohexylmethane, comprising the following steps: (1) Catalyst activation and modification: Activating and modifying the catalyst by the method according to any one of claims 1 to 4; (2) Preparation of 4,4'-HMDA: The raw material solution was continuously injected into a continuously stirred reactor for reaction.

6. The method according to claim 5, wherein: The catalyst is a supported catalyst Rh / alumina.

7. The method according to claim 6, wherein: The content of Rh is 2-6 wt % based on the weight of the supported catalyst.

8. The method according to claim 5, wherein: The concentration of 4,4'-MDA in the raw material solution is 30wt%-60wt%.

9. The method according to claim 5, wherein: The reaction temperature of step (2) is 120-200° C. and the pressure is 3-8 MPa.

10. The method according to claim 5, wherein: Step (2) catalyst mass space velocity is 12-28h -1 .

11. The method according to any one of claims 5 to 10, wherein: When the conversion rate of the raw material 4,4'-MDA drops to 90-95%, the catalyst activity is restored by the method according to any one of claims 1-4 and the reaction is continued.

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