A process for the preparation of 4,4'-hmda with low content of trans-trans isomer

Abstract

The application discloses a method for preparing 4,4'-HMDA with low content of trans-trans isomer, which comprises the following steps: continuously carrying out a tank type reaction on a raw material liquid containing 4,4'-diaminodiphenyl methane and hydrogen in the presence of a catalyst, and respectively feeding the raw material liquid and the hydrogen at a feeding speed changing with time. The catalyst can be used for more than 2000 hours without obvious attenuation without other special treatment, and the maximum processing capacity of the catalyst reaches 30 g MDA / g CAT*h. In addition, the detection frequency can be reduced, and cost is further saved. The conversion rate of MDA is greater than 99%, the yield of HMDA reaches more than 90%, and the content of trans-trans isomer is about 17%.

Description

Technical Field

[0001] This invention relates to the field of hydrogenation, specifically to a process for the continuous production of 4,4'-diaminodiphenylmethane (4,4'-HMDA) from 4,4'-diaminodiphenylmethane (4,4'-MDA). Background Technology

[0002] 4,4'-HMDA is mainly produced by high-pressure catalytic hydrogenation of 4,4'-MDA, yielding a mixture of three isomers: cis-cis, cis-trans, and trans-trans isomers. Among the three isomers, the trans-trans isomer is the most thermodynamically stable, and high-temperature reactions favor its formation. Different isomer ratios determine its application value; when the trans-trans isomer content is below 24%, it is classified as PACM20. Because PACM20 does not contain double bonds, the resulting 4,4'-dicyclohexylmethane diisocyanate (4,4'-HMDI) exhibits unique resistance to yellowing and weathering, making it an important intermediate in the polyurethane and polyamide industries. In addition, it is used as an amine epoxy curing agent. With economic development, its demand in domestic and international markets has been increasing year by year.

[0003] CN106631826A discloses a method for preparing diaminodicyclohexylmethane. The method improves the catalyst activity by using the acidity of phenolic compounds, reduces the formation of high-boiling-point tar, thereby extending the catalyst life and improving production efficiency. However, the introduced phenolic compounds have similar boiling points to the product, which increases energy consumption during purification.

[0004] CN110204447A discloses a catalyst regeneration method in the continuous production of 4,4'-diaminodicyclohexylmethane, which involves sequentially switching between liquid ammonia, alkali metal salt solution, and liquid ammonia replacement washing, followed by high-temperature modification. The overall process is complex and cumbersome, and also generates a large amount of wastewater.

[0005] CN103265438A discloses a method for the online activation of a catalyst deactivated during the hydrogenation of 4,4'-MDA to prepare 4,4'-HMDA. The method involves hydrogenating 4,4'-MDA to prepare 4,4'-HMDA. When the catalyst activity decreases, the process switches to a mixture of 2,4'-MDA and 4,4'-MDA. After the activity stabilizes, the process switches back to 4,4'-MDA. Catalyst activity is restored by switching between different feedstocks, and the unit can co-produce different products.

[0006] CN111804324A discloses a method for reducing the proportion of trans-trans isomers in a product and improving product selectivity by adding lithium amino groups. The method involves reacting with water to generate LiOH and NH3, which are then used to perform secondary modification of the catalyst to improve product selectivity. However, it does not address the issue of catalyst activity. The generated LiOH and NH3 are highly basic; while long-term use can improve selectivity, it also causes severe corrosion to the catalyst support, damaging the support structure and negatively impacting catalyst activity and lifespan, which is detrimental to long-term operation of continuous processes.

[0007] EP0231788A discloses an improved intermittent hydrogenation process that uses THF as a solvent and a bimetallic rhodium and ruthenium component as a catalyst. However, this process suffers from a decline in catalyst performance after a long period of use.

[0008] US20020198409A discloses a continuous hydrogenation reduction process for MDA, in which the catalyst activity decreases, requiring cooling and shutdown to wash the catalyst with a solvent.

[0009] US5196594A discloses a continuous hydrogenation reduction MDA process using supported ruthenium as a catalyst. Although the yield of HMDA can reach 93.7%, the efficiency is relatively low, with a feed rate of only 0.04-0.1 kg MDA / kg Cat per hour, which poses a challenge for industrial plants that require high-efficiency production.

[0010] In summary, the existing technology has the following drawbacks: The production of 4,4'-HMDA, regardless of whether a batch or continuous process is used, suffers from catalyst lifetime issues. As the catalyst's usage time increases, it gradually deactivates, and the regeneration process is complex, requiring additional process steps. The catalyst is not efficient enough, typically processing only 0.04-0.1 kg MDA / kg cat per hour, and the conversion and selectivity are not high. Ensuring high conversion often requires higher reaction temperatures and pressures, which are detrimental to the formation of low-trans-trans isomers. Summary of the Invention

[0011] This invention addresses the shortcomings of existing technologies by providing a method for preparing 4,4'-HMDA with low trans-trans isomer content. The method employs a continuous batch process, resulting in low production costs, high efficiency, and the production of low trans-trans HMDA.

[0012] To achieve the objectives of this invention, the technical solution adopted is as follows:

[0013] A method for preparing 4,4'-HMDA with low trans-trans isomer content includes the following steps: in the presence of a catalyst, a feed liquid containing 4,4'-diaminodiphenylmethane and hydrogen are subjected to a continuous batch reaction at feed rates that vary with time.

[0014] The concentration ω of the feed liquid containing 4,4'-diaminodiphenylmethane described in this invention is 20-60 wt%, based on the mass of solvent and feedstock.

[0015] The purity of the 4,4'-diaminodiphenylmethane described in this invention is ≥99.5%.

[0016] The solvent described in this invention is selected from one or more of methanol, ethanol, isopropanol, n-butanol, 2-butanol, dihydrofuran, tetrahydrofuran, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and dioxane.

[0017] The feed rate of the feed liquid containing 4,4'-diaminodiphenylmethane described in this invention is: Where T is the flow rate control cycle, which is an integer of 8 ≤ T ≤ 24, and the unit is h; t is the running time, which is an integer of 0 ≤ t ≤ 2000, and the unit is h.

[0018] For example, the product is collected and sampled for analysis within each control cycle. If the control cycle is 8 hours, the products within these 8 hours are collected in the same product container, mixed evenly, and then 3-5 drops of the product are taken and dissolved in 1 ml of ethanol. For example, gas chromatography is used for analysis. The analysis method is as follows: the gas chromatograph is an Agilent 7890B DB-5 capillary column, the FID detector temperature is 300℃, the initial column temperature is 50℃, the temperature is increased to 300℃ at 10℃ / min, and the temperature is held for 20 min.

[0019] The hydrogen feed rate described in this invention is V. 气 =6K1V m ωV 料 / M MDA L / h, where 1.1≤K1≤1.5, V m With a standard gas molar volume of 22.4 L / mol, M MDA The molar mass of the MDA raw material is 198 g / mol.

[0020] In the method described in this invention, the maximum mass hourly space velocity of the catalyst does not exceed 30 gMDA / gCAT*h within a control cycle.

[0021] The catalyst described in this invention is a supported catalyst, comprising an active metal and a support.

[0022] The active metals described in this invention include one or more of Pd, Pt, Ir, Co, Ru, and Rh.

[0023] The carrier of the present invention includes one or more of the following: alumina, activated carbon, silicon dioxide, zirconium oxide, diatomaceous earth, barium sulfate, magnesium oxide, titanium dioxide, and calcium carbonate.

[0024] In the catalyst of the present invention, the content of active metal is 0.1-10 wt%, preferably 2-4 wt%.

[0025] The catalyst described in this invention is preferably Ru / SiO2.

[0026] The reaction temperature described in this invention is 100-200℃, and the reaction pressure is 3-12MPa, preferably 140-150℃ and 5-8MPa.

[0027] In this invention, the MDA conversion rate is >99%, the HMDA yield reaches over 90%, the trans-trans isomer content is about 17%, the heavy component content is no more than 5%, the remaining components are light components and some hydrogenation products, and the catalyst performance exceeds 2000h without significant attenuation.

[0028] This invention provides a method for preparing 4,4'-HMDA with low trans-trans isomer content. Since the product obtained after hydrogenation has three different isomers, the trans-trans isomer content is limited not only by the catalyst but also by the degree of reaction. When the reaction is excessive, the low trans-trans product undergoes isomerization, gradually converting into the more thermodynamically stable high trans-trans product. That is, the cis-cis and cis-trans isomers in the low trans-trans product gradually convert into trans-trans isomers. By periodically controlling the feed liquid flow rate and a specific hydrogen flow rate using this function, the feed conversion rate is increased at low flow rates, and the trans-trans isomer content is further reduced at high flow rates, thus minimizing isomer conversion. Within one feed rate cycle, a mixture of products with different degrees of reaction is obtained, reducing the interconversion between isomers. Therefore, the feed conversion rate can be increased and the trans-trans isomer content of the product can be reduced within the feed cycle. If fed directly at a high flow rate, a large amount of partial hydrogenation products, namely monobenzene ring hydrogenation products (H6MDA), will be generated, leading to the accumulation of H6MDA. Further switching from high to low flow rate feed will increase the replacement time of these products in the continuous reactor, also resulting in H6MDA accumulation. Extending the low-flow-rate feed time will increase isomer conversion, leading to an increase in the content of the trans-transomer. The periodic function controls the feed flow rate trend from low to high and then gradually decreases. Furthermore, a feed pause control is added after switching from high to low flow rate and stopping the feed, allowing for deeper hydrogenation of some products, avoiding excessive accumulation, and increasing product yield. No other special treatment is required, allowing the catalyst performance to exceed 2000 hours without significant degradation, while the maximum catalyst throughput reaches 30 g MDA / gCAT*h. Simultaneously, the frequency of detection can be reduced, further saving costs. Detailed Implementation

[0029] To further illustrate the invention, experiments were conducted according to the methods described above; however, the listed procedures and data do not imply limitation on the scope of the invention. Experimental results were analyzed using gas chromatography.

[0030] 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:

[0031] The 4,4'-diaminodiphenylmethane (4,4'-MDA) raw material is from Wanhua Chemical and has a purity greater than 99%.

[0032] 2-Methyltetrahydrofuran was purchased from Beijing Innocare Technology Co., Ltd., and was of analytical grade.

[0033] The catalyst was purchased from Johnson Matthey.

[0034] Gas chromatography was performed using an Agilent 7890B DB-5 capillary column with an FID detector at 300°C. The initial column temperature was 50°C, increased to 300°C at a rate of 10°C / min, and held for 20 min. Where t, tH 12 MDA is the content of trans-trans isomers, and the rest are mainly light components and hydrogenation products of monobenzene rings.

[0035] Example 1

[0036] 800g of 2-methyltetrahydrofuran solvent and 7.5g of 4wt% Ru / SiO2 catalyst were added to a 2L reactor. The reactor was purged three times with 1MPa N2, followed by three purgings with 1MPa H2. The pressure was then increased to 1MPa with H2. The reaction temperature was raised to 145℃, and the pressure was maintained at 5MPa.

[0037] 4,4'-MDA was prepared into a 35 wt% 2-methyltetrahydrofuran solution (based on the total weight of the raw material and 2-methyltetrahydrofuran). The flow rate was controlled over a period of T = 8 h, and the flow rate V was controlled within this period. 气 Within the range of 0–78 L / h (K1 = 1.1), the maximum mass space velocity of the catalyst during the control period is 14.0 h⁻¹. -1 .

[0038] The results are as follows:

[0039]

[0040] Example 2

[0041] The concentration of 4,4'-MDA in Example 1 was changed to a 40 wt% 2-methyltetrahydrofuran solution (based on the total weight of the raw material and 2-methyltetrahydrofuran), and the flow rate control period was T = 12 h. 气 Within the range of 0–98 L / h (K1 = 1.2), the maximum mass space velocity of the catalyst during the control period was 16.0 h⁻¹. -1 The reaction temperature is 140℃ and the reaction pressure is 5MPa.

[0042] The results are as follows:

[0043]

[0044] Example 3

[0045] The concentration of 4,4'-MDA in Example 1 was changed to a 45 wt% 2-methyltetrahydrofuran solution (based on the total weight of the raw material and 2-methyltetrahydrofuran), and the flow rate control period was T = 16 h. 气 Within the range of 0–110 L / h (K1 = 1.2), the maximum mass space velocity of the catalyst during the control period is 18.0 h⁻¹. -1 The reaction temperature is 150℃ and the reaction pressure is 7MPa.

[0046] The results are as follows:

[0047]

[0048] Example 4

[0049] 800 g of 2-methyltetrahydrofuran solvent and 6.0 g of 4 wt% Rh / C catalyst were added to a 2 L reactor. The reactor was purged three times with 1 MPa N₂, followed by three purgings with 1 MPa H₂. The pressure was then increased to 1 MPa with H₂. The reaction temperature was raised to 145 °C, and the pressure was maintained at 5 MPa.

[0050] 4,4'-MDA was prepared into a 35 wt% 2-methyltetrahydrofuran solution (based on the total weight of the raw material and 2-methyltetrahydrofuran). The flow rate control period was T = 12 h. 气 The maximum mass space velocity of the catalyst was 17.5 h⁻¹ within the control period between 0 and 78 L / h (K1 = 1.1). -1 .

[0051] The results are as follows:

[0052]

[0053] Example 5

[0054] The concentration of 4,4'-MDA in Example 4 was changed to a 40 wt% 2-methyltetrahydrofuran solution (based on the total weight of the raw material and 2-methyltetrahydrofuran), and the flow rate control period was T = 16 h. 气 Within the range of 0–98 L / h (K1 = 1.2), the maximum mass space velocity of the catalyst during the control period is 20.0 h⁻¹. -1 The reaction temperature is 140℃ and the reaction pressure is 5MPa.

[0055] The results are as follows:

[0056]

[0057] Example 6

[0058] The 4,4'-MDA from Example 4 was prepared as a 55 wt% 2-methyltetrahydrofuran solution (based on the total weight of the raw material and 2-methyltetrahydrofuran), with a flow rate control period of T = 24 h, V 气 Within the range of 0–157 L / h (K1 = 1.4), the maximum mass space velocity of the catalyst during the control period was 27.5 h⁻¹. -1 The reaction temperature is 150℃ and the reaction pressure is 7MPa.

[0059] The results are as follows:

[0060]

[0061] Comparative Example 1

[0062] 800g of 2-methyltetrahydrofuran solvent and 7.5g of Ru / SiO2 catalyst were added to a 2L reactor. The reactor was purged three times with 1MPa N2, followed by three purgings with 1MPa H2. The pressure was then increased to 1MPa with H2. The reaction temperature was raised to 145℃, and the pressure was maintained at 5MPa.

[0063] 4,4'-MDA was prepared into a 35 wt% 2-methyltetrahydrofuran solution (based on the total weight of the raw material and 2-methyltetrahydrofuran), and a high-speed constant feed rate of 300 g / h was maintained. 气 =78L / h

[0064] The results are as follows:

[0065]

[0066] Comparative Example 2

[0067] The feed rate in Comparative Example 1 was changed to a low flow rate feed of 75 g / h.

[0068] The results are as follows:

[0069]

Claims

1. A method for preparing 4,4'-HMDA with low trans-trans isomer content, comprising the following steps: In the presence of a catalyst, a feed liquid containing 4,4'-diaminodiphenylmethane and hydrogen gas are subjected to a continuous batch reaction at a feed rate that varies with time. The feed rate of the feed liquid containing 4,4'-diaminodiphenylmethane is: Where T is the flow rate control period and is an integer of 8 ≤ T ≤ 24, in hours (h); t is the running time and is an integer of 0 ≤ t ≤ 2000, in hours (h). The hydrogen feed rate is V. 气 =6K1V m ωV 料 / M MDA L / h, where 1.1≤K1≤1.5, V m With a standard gas molar volume of 22.4 L / mol, M MDA It is 198 g / mol; The concentration ω of the feed liquid containing 4,4'-diaminodiphenylmethane is 20-60 wt%, based on the mass of solvent and feed.

2. The method according to claim 1, characterized in that, The maximum mass hourly space velocity (MSV) of the catalyst does not exceed 30 gMDA / gCAT*h within a control cycle.

3. The method according to claim 1, characterized in that, The catalyst is a supported catalyst, comprising an active metal and a support; the active metal is selected from one or more of Pd, Pt, Ir, Co, Ru, and Rh; the support is selected from one or more of alumina, activated carbon, silicon dioxide, zirconium oxide, diatomaceous earth, barium sulfate, magnesium oxide, titanium dioxide, and calcium carbonate.

4. The method according to claim 3, characterized in that, The catalyst contains 0.1-10 wt% active metal.

5. The method according to claim 3, characterized in that, The catalyst contains 2-4 wt% active metal.

6. The method according to claim 3, characterized in that, The catalyst is Ru / SiO2.

7. The method according to claim 1, characterized in that, The reaction temperature is 100–200℃, and the reaction pressure is 3–12 MPa.

8. The method according to claim 1, characterized in that, The reaction temperature is 140–150℃, and the reaction pressure is 5–8 MPa.

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