A method for continuously preparing 4,4'-diaminodicyclohexyl methane based on a loop reactor hydrogenation

Abstract

The application provides a method for preparing 4,4'-diamino dicyclohexyl methane based on a circulation reactor continuous hydrogenation, and belongs to the technical field of chemical reaction engineering. The method is that 4,4'-diamino diphenyl methane is mixed with an organic solvent, heated through a preheater first, fully mixed with hydrogen in a gas-liquid mixer after reaching a certain temperature, forms a gas-liquid mixed fluid, and is subjected to hydrogenation reaction with a supported ruthenium catalyst and a deamination retarder in a circulation reactor to prepare 4,4'-diamino dicyclohexyl methane. The application adds the deamination retarder in the circulation reactor hydrogenation process, reduces the deamination side reaction of the target product, thereby improving the yield of the target product, reducing the production cost of the unit yield of the target product, and the reaction pressure is low, the safety is high, the production efficiency is high, and the method has important application value in the actual mass production in industry.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis, specifically relating to a method for preparing 4,4'-diaminodicyclohexylmethane by continuous hydrogenation in a circulating reactor. Background Technology

[0002] 4,4'-Diaminodicyclohexylmethane is an important alicyclic amine organic intermediate, and its main chemical structure is shown below:

[0003] .

[0004] 4,4'-Diaminodicyclohexylmethane is a highly representative compound among aliphatic amines. Its molecule contains two cyclohexyl groups, exhibiting a typical symmetrical methane-bridged saturated aliphatic ring structure. It is a crucial intermediate in the polyurethane and polyamide industries, used to prepare polyamide resins and aliphatic polyurethanes. Typically, it is produced from 4,4'-diaminodicyclohexylmethane as a raw material. Under the action of a catalyst, the intermediate is first generated, and further hydrogenation yields 4,4'-diaminodicyclohexylmethane. Further reaction of the generated 4,4'-diaminodicyclohexylmethane produces the deamination byproduct dicyclohexylmethane. This deamination byproduct can be detected in the final product. In industrial production, the content of this byproduct in the final product is particularly significant, reducing the yield and quality of 4,4'-diaminodicyclohexylmethane and increasing its production cost.

[0005] Therefore, in the process of reducing aromatic amines to prepare 4,4'-diamino-dicyclohexylmethane, providing a method to avoid the deamination side reaction of the generated 4,4'-diamino-dicyclohexylmethane, thereby improving the yield of the target product and reducing production costs, has important application value. Summary of the Invention

[0006] To address the problems in the prior art, this invention provides a method for the continuous hydrogenation preparation of 4,4'-diaminodicyclohexylmethane using a circulating reactor, comprising the following steps:

[0007] ,

[0008] (1) 4,4'-diaminodiphenylmethane is mixed with an organic solvent to obtain a substrate solution to be hydrogenated. The substrate solution is first preheated by a preheater and then fully mixed with hydrogen in a gas-liquid mixer to form a gas-liquid mixed fluid.

[0009] (2) A gas-liquid mixture flows through a circulating reactor packed with a supported ruthenium catalyst and a deammoniation inhibitor, and undergoes a heterogeneous hydrogenation reduction reaction under certain temperature and pressure conditions and a preset residence time.

[0010] (3) The gas-liquid mixture flowing through the circulating reactor enters the cross-flow filter to obtain a 4,4'-diaminodicyclohexylmethane solution, and then the solvent is removed under reduced pressure to obtain pure 4,4'-diaminodicyclohexylmethane.

[0011] Further, the organic solvent mentioned in step (1) is one or more of cyclohexane, cyclohexylamine, methanol, ethanol, isopropanol, n-butanol, tetrahydrofuran, 2-methylfuran, anisole, methyl tert-butyl ether, diphenyl ether, 1,4-dioxane, ethylene glycol monomethyl ether, and ethylene glycol dimethyl ether; preferably one or more of tetrahydrofuran and cyclohexane.

[0012] Furthermore, the preheating temperature mentioned in step (1) is 45-60℃, preferably 55℃.

[0013] Further, the mass concentration of 4,4'-diaminodiphenylmethane in the mixed solution in step (1) is 5wt%-30wt%, preferably 15wt%.

[0014] Further, in step (1), the molar ratio of 4,4'-diaminodiphenylmethane to hydrogen is 1:6.5 to 9, preferably 1:7.

[0015] Further, the support for the supported ruthenium catalyst in step (2) is one or more of activated carbon, aluminum oxide, silicon dioxide, and titanium dioxide, preferably one or more of aluminum oxide and silicon dioxide.

[0016] Further, the deamination inhibitor mentioned in step (2) is one or more of potassium aluminum sulfate, ammonium aluminum sulfate, calcium sulfoaluminate, sodium aluminate, potassium aluminate, and calcium aluminate, preferably one or more of potassium aluminum sulfate and ammonium aluminum sulfate.

[0017] Further, the reaction temperature in step (2) is 90-110℃, preferably 100℃; the reaction pressure is 4.0-6.0 MPa, preferably 5.0 MPa; and the residence time is 3-8 min, preferably 5 min.

[0018] Furthermore, the mass hourly space velocity (MSV) of the mixed solution pumped in step (2) is 0.07~0.3 g / g, preferably 0.12 g / g.

[0019] Furthermore, the method for continuous hydrogenation synthesis of 4,4'-diaminodicyclohexylmethane employs a circulating reactor, which includes an inlet micromixer, a circulating reactor connected to the inlet micromixer, and a reaction circulation pump, a heat exchanger, and a cross-flow filter connected to the circulating reactor.

[0020] The beneficial effects of this invention are:

[0021] 1. This invention, by adding a deamination inhibitor during the hydrogenation reduction process, can significantly reduce or even inhibit the deamination side reaction of the target product, thereby reducing the content of by-products in the final product, increasing the yield and content of the target product, and lowering the production cost per unit output of the target product. It has important application value in actual large-scale industrial production.

[0022] 2. After mixing 4,4'-diaminodiphenylmethane with an organic solvent, the mixture is first heated in a preheater until it reaches a certain temperature. Then, it is fully mixed with hydrogen in a gas-liquid mixer to form a gas-liquid mixture. The gas and liquid phases are evenly distributed in the circulating reactor. The circulating reactor has a strong heat transfer capacity, avoiding local over-hydrogenation. The reaction pressure is low and the reaction temperature is low, which significantly reduces safety hazards, reduces the occurrence of by-products, extends the catalyst life, and reduces reaction costs. The conversion rate of the reaction raw materials is 100%, and the selectivity is greater than 99%. Detailed Implementation

[0023] Example 1:

[0024] A method for preparing 4,4'-diaminodicyclohexylmethane by continuous hydrogenation in a circulating reactor includes the following steps:

[0025] (1) 4,4'-diaminodiphenylmethane (MDA) and tetrahydrofuran are mixed in a preheater to obtain an MDA solution with a concentration of 15 wt% and a preheating temperature of 55 °C. The solution is then mixed with hydrogen in an inlet micro-mixer (MDA to hydrogen molar ratio 1:7) to form a gas-liquid mixture.

[0026] (2) The gas-liquid mixture obtained in step (1) is pumped into a circulating reactor filled with ruthenium / alumina catalyst and potassium aluminum sulfate at a raw material mass hourly space velocity of 0.12 g / g using a metering pump. Nitrogen gas is introduced and the air in the reactor is exhausted. Then, hydrogen gas is introduced. The reaction temperature of the circulating reactor is 100℃, the pressure is 5.0 MPa, and the residence time is 5 min to carry out a heterogeneous hydrogenation reduction reaction.

[0027] (3) The gas-liquid mixture obtained in step (2) was fed into a cross-flow filter, and the separated reaction solution was analyzed by HPLC. The results showed that the MDA conversion rate was 100%, the yield was 99.5%, and no byproduct dicyclohexylmethane was detected.

[0028] Example 2:

[0029] A method for preparing 4,4'-diaminodicyclohexylmethane by continuous hydrogenation in a circulating reactor includes the following steps:

[0030] (1) 4,4'-diaminodiphenylmethane (MDA) and cyclohexane are mixed in a preheater to obtain an MDA solution with a concentration of 15 wt% and a preheating temperature of 55°C. The solution is then mixed with hydrogen in an inlet micro-mixer (MDA to hydrogen molar ratio 1:7) to form a gas-liquid mixture.

[0031] (2) The gas-liquid mixture obtained in step (1) is pumped into a circulating reactor filled with ruthenium / alumina catalyst and ammonium aluminum sulfate at a raw material mass hourly space velocity of 0.12 g / g using a metering pump. Nitrogen gas is introduced and the air in the reactor is exhausted. Then, hydrogen gas is introduced. The reaction temperature of the circulating reactor is 100℃, the pressure is 5.0 MPa, and the residence time is 5 min to carry out a heterogeneous hydrogenation reduction reaction.

[0032] (3) The gas-liquid mixture obtained in step (2) was fed into a cross-flow filter, and the separated reaction solution was analyzed by HPLC. The results showed that the MDA conversion rate was 100%, the yield was 99.4%, and no byproduct dicyclohexylmethane was detected.

[0033] Example 3:

[0034] A method for preparing 4,4'-diaminodicyclohexylmethane by continuous hydrogenation in a circulating reactor includes the following steps:

[0035] (1) 4,4'-diaminodiphenylmethane (MDA) and tetrahydrofuran are mixed in a preheater to obtain an MDA solution with a concentration of 5 wt% and a preheating temperature of 45 °C. The solution is then mixed with hydrogen in an inlet micro-mixer (MDA to hydrogen molar ratio 1:6.5) to form a gas-liquid mixture.

[0036] (2) The gas-liquid mixture obtained in step (1) is pumped into a circulating reactor filled with ruthenium / alumina catalyst and potassium aluminum sulfate at a raw material mass hourly space velocity of 0.07 g / g using a metering pump. Nitrogen is introduced and the air in the reactor is exhausted. Then, hydrogen is introduced. The reaction temperature of the circulating reactor is 90℃, the pressure is 4.0 MPa, and the residence time is 3 min to carry out the heterogeneous hydrogenation reduction reaction.

[0037] (3) The gas-liquid mixture obtained in step (2) was fed into a cross-flow filter, and the separated reaction liquid was analyzed by HPLC. The results showed that the MDA conversion rate was 100%, the yield was 99.4%, and the content of the byproduct dicyclohexylmethane was 0.18%.

[0038] Example 4:

[0039] A method for preparing 4,4'-diaminodicyclohexylmethane by continuous hydrogenation in a circulating reactor includes the following steps:

[0040] (1) 4,4'-diaminodiphenylmethane (MDA) and tetrahydrofuran are mixed in a preheater to obtain an MDA solution with a concentration of 30 wt% and a preheating temperature of 60 °C. The solution is then mixed with hydrogen in an inlet micro-mixer (MDA to hydrogen molar ratio 1:9) to form a gas-liquid mixture.

[0041] (2) The gas-liquid mixture obtained in step (1) is pumped into a circulating reactor filled with ruthenium / alumina catalyst and potassium aluminum sulfate at a raw material mass hourly space velocity of 0.3 g / g using a metering pump. Nitrogen is introduced and the air in the reactor is exhausted. Then, hydrogen is introduced. The reaction temperature of the circulating reactor is 110℃, the pressure is 6.0 MPa, and the residence time is 8 min to carry out the heterogeneous hydrogenation reduction reaction.

[0042] (3) The gas-liquid mixture obtained in step (2) was fed into a cross-flow filter, and the separated reaction liquid was analyzed by HPLC. The results showed that the MDA conversion rate was 100%, the yield was 99.5%, and the content of the byproduct dicyclohexylmethane was 0.25%.

[0043] Example 5:

[0044] A method for preparing 4,4'-diaminodicyclohexylmethane by continuous hydrogenation in a circulating reactor includes the following steps:

[0045] (1) 4,4'-diaminodiphenylmethane (MDA) and tetrahydrofuran are mixed in a preheater to obtain an MDA solution with a concentration of 3wt% and a preheating temperature of 40°C. The solution is then mixed with hydrogen in an inlet micro-mixer (MDA to hydrogen molar ratio 1:5) to form a gas-liquid mixture.

[0046] (2) The gas-liquid mixture obtained in step (1) is pumped into a circulating reactor filled with ruthenium / alumina catalyst and potassium aluminum sulfate at a raw material mass hourly space velocity of 0.05 g / g using a metering pump. Nitrogen is introduced and the air in the reactor is exhausted. Then, hydrogen is introduced. The reaction temperature of the circulating reactor is 80℃, the pressure is 3.0 MPa, and the residence time is 2 min to carry out the heterogeneous hydrogenation reduction reaction.

[0047] (3) The gas-liquid mixture obtained in step (2) was fed into a cross-flow filter, and the separated reaction liquid was analyzed by HPLC. The results showed that the MDA conversion rate was 99%, the yield was 97.3%, and the dicyclohexylmethane content was 1.85%.

[0048] Example 6:

[0049] A method for preparing 4,4'-diaminodicyclohexylmethane by continuous hydrogenation in a circulating reactor includes the following steps:

[0050] (1) 4,4'-diaminodiphenylmethane (MDA) and tetrahydrofuran are mixed in a preheater to obtain an MDA solution with a concentration of 35 wt% and a preheating temperature of 65 °C. The solution is then mixed with hydrogen in an inlet micro-mixer (MDA to hydrogen molar ratio 1:10) to form a gas-liquid mixture.

[0051] (2) The gas-liquid mixture obtained in step (1) is pumped into a circulating reactor filled with ruthenium / alumina catalyst and potassium aluminum sulfate at a raw material mass hourly space velocity of 0.40 g / g using a metering pump. Nitrogen is introduced and the air in the reactor is exhausted. Then, hydrogen is introduced. The reaction temperature of the circulating reactor is 120℃, the pressure is 7.0 MPa, and the residence time is 10 min to carry out a heterogeneous hydrogenation reduction reaction.

[0052] (3) The gas-liquid mixture obtained in step (2) was fed into a cross-flow filter, and the separated reaction liquid was analyzed by HPLC. The results showed that the MDA conversion rate was 98%, the yield was 96.8%, and the content of the by-product dicyclohexylmethane was 2.87%.

[0053] Comparative Example 1: Batch Reaction Hydrogenation Experiment

[0054] 1) Feeding: Add 50g of 4,4'-diaminodiphenylmethane (MDA), 100.0g of methanol, 1.51g of 5wt%Ru / C catalyst, and 0.30g of lithium hydroxide monohydrate sequentially to the intermittent high-pressure reactor;

[0055] 2) Gas replacement: In a sealed reactor, the air inside the reactor is first replaced three times with high-purity nitrogen. Each time, the pressure is increased to 1.0 MPa and then slowly released to remove the air from the reactor. Then, the reactor is replaced three times with high-purity hydrogen.

[0056] 3) Heating and pressurizing: Charge hydrogen into the reactor to an initial pressure of 3.0 MPa, turn on the mechanical stirrer, control the stirring speed at 700 r / min, and raise the temperature to the reaction temperature of 140℃ through a program at a rate of 4℃ / min;

[0057] 4) Intermittent hydrogenation reaction: Under constant temperature of 140℃, high-purity hydrogen is continuously added to maintain a constant reaction pressure of 6.0MPa in the reactor and an intermittent constant temperature hydrogenation reaction is carried out for 8 hours; during this period, the hydrogen absorption rate is monitored in real time. When the hydrogen absorption rate drops below 0.008L / h, the reaction is determined to have reached the endpoint and heating is stopped.

[0058] 5) Post-processing: Keep stirring and allow to cool naturally to room temperature (25±2℃). Slowly depressurize to atmospheric pressure and replace the residual hydrogen in the reactor twice with high-purity nitrogen. Open the reactor and separate and recover the solid catalyst by passing the reaction liquid through a precision filter (0.22μm filter membrane pore size). Distill the filtrate at atmospheric pressure to recover the tetrahydrofuran solvent (recovery rate ≥95.5%). The remaining crude product is subjected to vacuum distillation, controlling the top temperature of the column at 165℃ and the vacuum degree at 1.5kPa. Collect the target fraction to obtain the product. The test results show that the MDA conversion rate is 99%, the yield is 97.3%, and the content of the by-product dicyclohexylmethane is 1.85%.

[0059] While the specific embodiments of the present invention have been described above, they are not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for preparing 4,4'-diaminodicyclohexylmethane by continuous hydrogenation in a circulating reactor, characterized in that, The reaction formula is shown below: , Includes the following steps: (1) 4,4'-diaminodiphenylmethane is mixed with an organic solvent to obtain a substrate solution to be hydrogenated. The substrate solution is first preheated by a preheater and then fully mixed with hydrogen in a gas-liquid mixer to form a gas-liquid mixed fluid. (2) A gas-liquid mixture flows through a circulating reactor packed with a supported ruthenium catalyst and a deammoniation inhibitor, and undergoes a heterogeneous hydrogenation reduction reaction under certain temperature and pressure conditions and a preset residence time. (3) The gas-liquid mixture flowing through the circulating reactor enters the cross-flow filter to obtain a 4,4'-diaminodicyclohexylmethane solution, and then the solvent is removed under reduced pressure to obtain pure 4,4'-diaminodicyclohexylmethane.

2. The method for preparing 4,4'-diaminodicyclohexylmethane by continuous hydrogenation in a circulating reactor according to claim 1, characterized in that, The organic solvent mentioned in step (1) is one or more of cyclohexane, cyclohexylamine, methanol, ethanol, isopropanol, n-butanol, tetrahydrofuran, 2-methylfuran, anisole, methyl tert-butyl ether, diphenyl ether, 1,4-dioxane, ethylene glycol monomethyl ether, and ethylene glycol dimethyl ether; preferably one or more of tetrahydrofuran and cyclohexane.

3. The method for preparing 4,4'-diaminodicyclohexylmethane by continuous hydrogenation in a circulating reactor according to claim 1, characterized in that, The preheating temperature mentioned in step (1) is 45-60℃, preferably 55℃.

4. The method for preparing 4,4'-diaminodicyclohexylmethane by continuous hydrogenation in a circulating reactor according to claim 1, characterized in that, The mass concentration of 4,4'-diaminodiphenylmethane in the mixed solution in step (1) is 5 wt%-30 wt%, preferably 15 wt%.

5. The method for preparing 4,4'-diaminodicyclohexylmethane by continuous hydrogenation in a circulating reactor according to claim 1, characterized in that, In step (1), the molar ratio of 4,4'-diaminodiphenylmethane to hydrogen is 1:6.5 to 9, preferably 1:

7.

6. The method for preparing 4,4'-diaminodicyclohexylmethane by continuous hydrogenation in a circulating reactor according to claim 1, characterized in that, The support for the supported ruthenium catalyst in step (2) is one or more of activated carbon, aluminum oxide, silicon dioxide, and titanium dioxide. Preferably, the support for the supported ruthenium catalyst in step (2) is one or more of aluminum oxide and silicon dioxide.

7. The method for preparing 4,4'-diaminodicyclohexylmethane by continuous hydrogenation in a circulating reactor according to claim 1, characterized in that, The deammoniation inhibitor mentioned in step (2) is one or more of potassium aluminum sulfate, ammonium aluminum sulfate, calcium sulfoaluminate, sodium aluminate, potassium aluminate, and calcium aluminate, preferably one or more of potassium aluminum sulfate and ammonium aluminum sulfate.

8. The method for preparing 4,4'-diaminodicyclohexylmethane by continuous hydrogenation in a circulating reactor according to claim 1, characterized in that, The reaction temperature in step (2) is 90-110℃, preferably 100℃; the reaction pressure is 4.0-6.0 MPa, preferably 5.0 MPa; and the residence time is 3-8 min, preferably 5 min.

9. The method for preparing 4,4'-diaminodicyclohexylmethane by continuous hydrogenation in a circulating reactor according to claim 1, characterized in that, The mass hourly space velocity (MSV) of the mixed solution pumped in step (2) is 0.07~0.3 g / g, preferably 0.12 g / g.

10. The method for preparing 4,4'-diaminodicyclohexylmethane by continuous hydrogenation in a circulating reactor according to claim 1, characterized in that, The method for continuous hydrogenation synthesis of 4,4'-diaminodicyclohexylmethane employs a circulating reactor, which includes an inlet micromixer, a circulating reactor connected to the inlet micromixer, and a reaction circulation pump, a heat exchanger, and a cross-flow filter connected to the circulating reactor.

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