A method for continuously producing low-anti-HMDA

Abstract

The present invention provides a process method for producing low-trans HMDA by continuous autoclave reaction with simple process operation, low production cost and high efficiency, wherein a raw material liquid containing 4,4'-diaminodiphenylmethane is used as a raw material, an auxiliary agent is added, and low-trans 4,4'-diaminodicyclohexylmethane is produced continuously by double autoclaves in series, wherein the auxiliary agent is selected from at least one of lithium formate, lithium acetate and lithium oxalate. The MDA conversion rate is greater than 99%, the HMDA yield reaches more than 90%, and the content of trans-trans isomers is stabilized at about 17%; the catalyst mass space velocity can reach 8-20gMDA / gCAT*h, and the catalyst performance can exceed 1000h without obvious attenuation without other special treatment.

Description

Technical Field

[0001] The invention relates to a method for continuously producing 4,4'-diaminodicyclohexylmethane (HMDA) by taking 4,4'-diaminodiphenylmethane (MDA) as a raw material. 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] The isomer content determines the application value. When the trans-trans isomer content is less than 24%, it is PACM20. In addition to being used as an amine epoxy curing agent, PACM20 is also an important intermediate in the polyurethane and polyamide industries. It is a raw material for preparing a new generation of high-performance 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.

[0004] The raw material of 4,4'-HMDA, 4,4'-MDA, contains two benzene rings. 4,4'-HMDA is obtained by complete hydrogenation of the 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] EP0231788 discloses an improved intermittent hydrogenation process, using THF as solvent and bimetallic rhodium and ruthenium components as catalysts, at 170-195°C and 700-1500psig, to prepare HMDA with an anti-isomer content of 17-24%, but does not solve the problem of performance degradation of the catalyst after a long period of use. Patent CN110204447 discloses a catalyst regeneration method 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, and the washing is liquid ammonia-alkali metal salt solution-liquid ammonia replacement, followed by high-temperature modification. The process is cumbersome, and the feed needs to be switched frequently, and a large amount of wastewater is generated.

[0006] US20020198409 discloses a continuous hydrogenation reduction process of MDA, which uses alcohols as solvents and supported ruthenium as catalysts 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 on 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 its 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-trans HMDA using Ru / Al2O3 as a catalyst in a fixed bed reactor. The reaction temperature is relatively low at 80°C, and the catalyst processes 0.04kg MDA / kg cat of raw materials per hour, but the conversion rate is less than 70%, and the selectivity is only 60%. When the conversion rate exceeds 80%, the content of its trans-trans structure will increase significantly. Patent CN111804324B discloses a method in which the addition of lithium amide can reduce the proportion of trans-trans isomers in the product and improve the selectivity of the product. Since lithium amide is active in nature and easily reacts with water, the storage conditions are relatively harsh. The patent uses this property to react with water during the reaction process to generate LiOH and NH3, and the catalyst is subjected to secondary modification to reduce the proportion of trans-trans isomers in the product and improve the selectivity of the product, but does not mention the influence of the catalyst reactivity. However, lithium amide and the generated LiOH and NH3 are highly alkaline. Although long-term use can improve product selectivity, it will also cause serious corrosion to the catalyst carrier, destroy the carrier structure, affect the catalyst activity and life, and is not conducive to the implementation of the continuous process.

[0007] In summary, the existing technology has the following defects:

[0008] Most of the MDA hydrogenation continuous processes use fixed-bed reactors. The amount of raw materials processed per unit mass of catalyst per unit time is low. The catalyst processing capacity per hour is usually 0.04-0.1kg MDA / kg cat, and the conversion rate and selectivity are not high. When ensuring a high conversion rate, higher reaction temperatures and pressures are often required, which is not conducive to the formation of low-trans isomers. At the same time, as the catalyst is used for a longer time, the catalyst gradually deactivates, and the regeneration scheme is complicated, requiring additional process flow, increasing the workload, or using liquid ammonia and other forms for high-temperature re-modification, generating a large amount of wastewater. The continuous kettle process generally requires multiple kettles in series to ensure the conversion rate of the raw materials. The large number of reactors in series takes up a large space, and the conversion rate requirements cannot be met when there are few reactors. In addition, since the catalyst form is the same as the intermittent reactor form, which is a powder catalyst, its life is relatively short. Summary of the invention

[0009] The present invention aims at the deficiencies of the prior art and provides a process for producing low-trans HMDA by continuous autoclave reaction with simple process operation, low production cost and high efficiency, wherein the MDA conversion rate is greater than 99%, the HMDA yield reaches more than 90%, and the content of trans-trans isomers is stabilized at about 17%; the catalyst mass space velocity can reach 8-20gMDA / gCAT*h, and the catalyst performance can exceed 1000h without obvious attenuation without other special treatment.

[0010] In order to achieve the purpose of the present invention, the technical solution adopted is:

[0011] A scheme for producing low-reverse 4,4'-HMDA by continuous batch reaction using 4,4'-MDA as raw material, comprising:

[0012] Using a raw material liquid containing 4,4'-diaminodiphenylmethane as a raw material, adding an auxiliary agent, and using a double-reactor series to continuously produce 4,4'-diaminodicyclohexylmethane to obtain low-reverse 4,4'-HMDA;

[0013] The reaction kettle consists of two kettles connected in series, each containing an equal amount of catalyst;

[0014] The reaction volume of the first reactor (the first reactor to be fed, reactor a) is 1.2 to 1.8 times the reaction volume of the second reactor (reactor b), that is, the liquid holding capacity of the two reactors is different;

[0015] The reaction temperature of the reactor a is 120-140°C, and the reaction pressure is 3-5MPa, preferably 135°C, 4MPa;

[0016] The reaction temperature of the reactor b is 140-170°C, and the reaction pressure is 4-8MPa, preferably 160°C, 6MPa;

[0017] The catalyst is a supported catalyst, which is a combination of an active metal and a carrier; the active metal includes any one of Pt, Rh, and Ru or a combination of at least two of them, preferably Rh; the carrier includes any one of alumina, activated carbon, lithium aluminate, silicon oxide, and diatomaceous earth or a combination of at least two of them, preferably alumina; based on the weight of the supported catalyst, the content of the active metal is 2-6wt%, preferably 3-4wt%; preferably, the supported catalyst is Rh / Al2O3.

[0018] The solvent is selected from any one or a combination of at least two of methanol, ethanol, isopropanol, n-butanol, and 2-butanol;

[0019] The concentration of 4,4'-MDA in the raw material solution is 30wt%-60wt% (based on the mass of the solvent and the raw material).

[0020] The auxiliary agent is selected from one or a combination of at least two of lithium formate, lithium acetate and lithium oxalate;

[0021] The dosage of the auxiliary agent is 0.01-0.12 wt % (based on the mass of the raw material 4,4'-MDA), preferably 0.08 wt %.

[0022] The feed rate of the raw material solution is calculated based on the mass of the solution put into the reactor, and the feed rate maintains the catalyst mass space velocity of each reactor at 8-20 gMDA / gCAT*h.

[0023] The beneficial technical effects achieved by the present invention are:

[0024] (1) The present invention provides a process scheme for continuously producing low-reverse HMDA by connecting two kettles in series. The two kettles in series not only improve the raw material conversion rate, but also maintain the mass space velocity of the catalyst at 8-20gMDA / gCAT*h. Without other special treatment, the catalyst performance can exceed 1000h without obvious attenuation.

[0025] (2) Through the combined effect of modified catalyst and continuous double-kettle series process, the use time of the catalyst in the low temperature section is extended, so that the entire reaction process is at a lower reaction temperature, thereby maintaining the trans-trans isomer content of the product at about 17%.

[0026] (3) The alkalinity of the modifier is weaker than that of the currently disclosed patent data, and the problem of corrosion of the catalyst carrier by the currently disclosed modification aid, thereby reducing the life of the catalyst, can be effectively improved without the need for a secondary reaction. DETAILED DESCRIPTION

[0027] In order to further illustrate the invention, the following experiment is carried out according to the above method, but the listed process and data do not mean to limit the scope of the invention. The experimental results are analyzed by gas chromatography.

[0028] Unless otherwise specified, the raw materials used in the following examples or comparative examples are all commercially available industrial-grade conventional raw materials. The main raw materials and testing instrument information are as follows:

[0029] The raw material of 4,4'-diaminodiphenylmethane (4,4'-MDA) comes from Wanhua Chemical with a purity greater than 99%.

[0030] n-Butanol was purchased from Beijing Inokai Technology Co., Ltd. of analytical grade.

[0031] The catalyst was purchased from Johnson Matthey.

[0032] 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 the others are mainly light components and some incomplete hydrogenation products.

[0033] Example 1

[0034] The reactor is composed of two reactors a and b connected in series. 480g of solvent n-butanol (the volume of the reactor is 1L, the liquid level is 480g) and 2.5g of 4wt% Rh / Al2O3 catalyst are added to reactor a, and 400g of solvent n-butanol (the volume of the reactor is 1L, the liquid level is 400g, that is, the reaction volume of reactor a is 1.2 times that of reactor b) and 2.5g of 4wt% Rh / Al2O3 catalyst are added to reactor b. After replacing with 1MPa of N2 three times, it is replaced with 1MPa of H2 three times. Then H2 is added to 1MPa. Reactor a is heated to a reaction temperature of 135°C and the pressure is maintained at 4MPa. Reactor b is heated to a reaction temperature of 160°C and the pressure is maintained at 6MPa.

[0035] 4,4'-MDA was prepared into a 40 wt% n-butanol solution (based on the total weight of the raw material and n-butanol), and 0.08 wt% lithium acetate (based on the raw material 4,4'-MDA) was added as an auxiliary agent. The mass space velocity of the catalyst in each kettle was 13 gMDA / gCAT*h.

[0036] The results are as follows:

[0037]

[0038] Example 2

[0039] The raw material liquid was changed to: 4,4'-MDA concentration of 40wt%, 0.04wt% lithium acetate was added as an auxiliary agent (based on the raw material 4,4'-MDA), the catalyst mass space velocity was 13gMDA / gCAT*h, the reaction conditions of kettle a and kettle b were the same as in Example 1, and the reaction was continued.

[0040] The results are as follows:

[0041]

[0042] Example 3

[0043] The reactor consists of two reactors a and b connected in series. 560g of solvent n-butanol (volume of the reactor is 1L, liquid level is 560g) and 3.2g of 4wt% Rh / Al2O3 catalyst are added to reactor a, and 350g of solvent n-butanol (volume of the reactor is 1L, liquid level is 350g, i.e. reaction volume of reactor a is 1.6 times of reactor b) and 3.2g of 4wt% Rh / Al2O3 catalyst are added to reactor b. After displacement with 1MPa N2 three times, it is then replaced with 1MPa H2 three times. Then H2 is added to 1MPa. Reactor a is heated to a reaction temperature of 130°C and maintained at a pressure of 5MPa, and reactor b is heated to a reaction temperature of 170°C and maintained at a pressure of 7MPa.

[0044] 4,4'-MDA was prepared into a 40 wt% n-butanol solution (based on the total weight of the raw material and n-butanol), and 0.06 wt% of lithium acetate (based on the raw material 4,4'-MDA) was added as an auxiliary agent. The mass space velocity of the catalyst in each kettle was 15 gMDA / gCAT*h.

[0045] The results are as follows:

[0046]

[0047] Example 4

[0048] The difference compared with Example 3 is that the amount of the auxiliary agent in the raw material solution is changed to 0.1wt%, and the reaction is continued.

[0049] The results are as follows:

[0050]

[0051] Comparative Example 1

[0052] The difference compared with Example 1 is that the raw material does not contain the auxiliary agent lithium acetate.

[0053] The results are as follows:

[0054] Running time / h <![CDATA[H 12 MDA / %]]> <![CDATA[t,t-H 12 MDA / %]]> Recombinant content / % other / % Conversion rate / % 100 88.9 19.1 6.2 4.9 98.5 300 87.7 18.5 6.9 5.4 96.2 500 86.5 17.8 7.4 6.1 94.1

[0055] Comparative Example 2

[0056] The reactor consists of two reactors a and b connected in series. 400g of solvent n-butanol (the volume of the reactor is 1L, the liquid level is 400g) and 2.5g of 4wt% Rh / Al2O3 catalyst are added to reactor a, and 400g of solvent n-butanol (the volume of the reactor is 1L, the liquid level is 400g, that is, the reaction volumes of the two reactors are the same) and 2.5g of 4wt% Rh / Al2O3 catalyst are added to reactor b. After replacing with 1MPa of N2 three times, it is replaced with 1MPa of H2 three times. Then H2 is added to 1MPa. Reactor a is heated to a reaction temperature of 135°C and the pressure is maintained at 4MPa. Reactor b is heated to a reaction temperature of 160°C and the pressure is maintained at 6MPa.

[0057] 4,4'-MDA was prepared into a 40 wt% n-butanol solution, and 0.08 wt% of lithium acetate (based on the raw material 4,4'-MDA) as an auxiliary agent was added. The catalyst mass space velocity of each kettle was 13 gMDA / gCAT*h.

[0058] The results are as follows:

[0059]

[0060]

[0061] Comparative Example 3

[0062] Only the reaction kettle b was used, i.e., a single-kettle reaction. 400 g of n-butanol solvent (liquid level was 400 g) and 2.5 g of 4 wt% Rh / Al2O3 catalyst were added. After displacement with 1 MPa of N2 three times, it was then replaced with 1 MPa of H2 three times. Then, the pressure was supplemented with H2 to 1 MPa. The temperature was raised to a reaction temperature of 160°C and the pressure was maintained at 6 MPa.

[0063] 4,4'-MDA was prepared into a 40 wt% n-butanol solution, 0.08 wt% of lithium acetate as an auxiliary agent (based on the raw material 4,4'-MDA) was added, and the catalyst mass space velocity was 13 gMDA / gCAT*h.

[0064] The results are as follows:

[0065]

[0066] Comparative Example 4

[0067] The difference compared with Example 1 is that the auxiliary agent in the raw material is replaced by lithium hydroxide.

[0068] The results are as follows:

[0069] Running time / h <![CDATA[H 12 MDA / %]]> <![CDATA[t,t-H 12 MDA / %]]> Recombinant content / % other / % Conversion rate / % 100 88.9 17.5 3.7 7.4 98.1 200 86.8 17.2 4.4 8.8 96.4 300 85.4 17.1 5.3 9.3 95.6

Claims

1. A method for continuously producing 4,4'-diaminodicyclohexylmethane, comprising the following steps: A raw material liquid containing 4,4'-diaminodiphenylmethane is used as a raw material, an auxiliary agent is added, and 4,4'-diaminodicyclohexylmethane is continuously produced by using two kettles in series, wherein the auxiliary agent is selected from at least one of lithium formate, lithium acetate, and lithium oxalate; the two kettles contain an equal amount of catalyst, and the catalyst is a supported catalyst composed of an active metal and a carrier; the active metal is selected from any one of Pt, Rh, and Ru or a combination of at least two; the carrier is selected from any one of alumina, activated carbon, lithium aluminate, silicon oxide, and diatomaceous earth or a combination of at least two.

2. The method according to claim 1, wherein the reaction volume of the first reactor is 1.2 to 1.8 times the reaction volume of the second reactor.

3. The method according to claim 1 or 2, wherein the reaction temperature of the first reactor is 120-140°C and the reaction pressure is 3-5MPa.

4. The method according to claim 1 or 2, wherein the reaction temperature of the second reactor is 140-170°C and the reaction pressure is 4-8MPa.

5. The method according to claim 1, wherein: The dosage of the auxiliary agent is 0.01-0.12wt%, based on the mass of the raw material 4,4'-diaminodiphenylmethane.

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

7. The method according to claim 1, wherein: The solvent of the raw material liquid is selected from any one of methanol, ethanol, isopropanol, n-butanol, and 2-butanol, or a combination of at least two thereof.

8. The method according to claim 1 or 7, wherein: The concentration of 4,4'-diaminodiphenylmethane in the raw material solution is 30wt%-60wt%.

9. The method according to claim 1 or 2, wherein: The catalyst mass space velocity of each kettle is 8-20 g 4,4'-diaminodiphenylmethane / g catalyst*h.

Images