Hydrogenation catalyst and method for preparing 1, 4-cyclohexanediamine with high trans-cis ratio

Abstract

The invention relates to a hydrogenation catalyst and a method for preparing 1, 4-cyclohexanediamine with a high trans-cis ratio, the hydrogenation catalyst comprises an active metal and a modified carrier, and the active metal is selected from one or more of Ru, Rh, Ni, Pt and Pd; the modified carrier is a composite alumina carrier with a microporous structure. According to the preparation method, the yield of 1, 4-cyclohexanediamine trans-form in the product can be effectively improved, and the performance of polyurethane is improved.

Description

Technical Field

[0001] The present invention relates to a hydrogenation catalyst and a preparation method of cyclohexanediamine, and particularly relates to a method for preparing 1,4-cyclohexanediamine with a high trans-cis ratio, belonging to the field of synthesis of amine compounds. Background Art

[0002] Currently, aromatic diamines and their hydrogenated products are traditional chemical intermediates and can be widely used in the pharmaceutical, rubber, and polyurethane industries. Among them, p-phenylenediamine (hereinafter referred to as PPDA) is a derivative organic compound of aniline, and it can be hydrogenated to prepare an important polyurethane raw material 1,4-cyclohexanediamine (hereinafter referred to as CHDA). In the polyurethane industry, the polyurethane polymer prepared from PPDA will slowly change color due to the molecular structure, thus limiting its application. However, compared with the aromatic diamine of PPDA, the polyurethane prepared from CHDA is more stable to light and air, and has better performance.

[0003] For the catalytic hydrogenation of PPDA to synthesize CHDA, from the existing literature and patent reports, the main achievements are to use specific noble metal catalysts such as rhodium Rh and ruthenium Ru for the reaction. US Patents US2606924 and US3697449 reported the effect of supported Ru catalysts in the hydrogenation of the benzene ring of aromatic amine compounds. The reaction is mainly carried out under the conditions of P = 10 - 35 MPa, T = 80 - 230 °C, using an inert solvent, and the catalyst is alkali-modified. Research shows that high pressure and alkali modification of the catalyst can both improve the catalytic activity and the reaction yield. US Patent US3586862 reported that the Rh catalyst also showed high activity in the hydrogenation of PPDA, but due to its high price, the further use of the Rh catalyst is limited.

[0004] For this saturated cyclic compound of CHDA, it mainly includes two conformations, the boat form and the chair form, in which the six carbon atoms exist in a non-planar structure and basically exist in the chair configuration. However, the chemical bonds do not break during the mutual conversion between the conformations, so the conformational conversion will not affect the molecular configuration. Therefore, when paying attention to the stereoisomerism of CHDA, conformational isomerism can be ignored, and only cis-trans isomerism needs to be concerned. In addition, due to the different spatial structures of the cis-trans isomers, their physical and chemical properties are also different. Among them, the structural symmetry of the trans form is better than that of the cis form, so the boiling point and melting point are also higher than those of the cis form.

[0005] The two amino groups of CHDA are respectively located on the 1,4 carbon atoms of cyclohexane. Without considering stereoisomerism, CHDA has two isomers, trans-1,4-cyclohexanediamine (hereinafter referred to as trans-CHDA) and cis-1,4-cyclohexanediamine (hereinafter referred to as cis-CHDA), and their structures are as follows:

[0006]

[0007] Generally, the larger the proportion of trans-CHDA, the better the properties of the prepared polyurethane. Therefore, to improve the properties of polyurethane, the proportion of trans-CHDA should be increased as much as possible.

[0008] Currently, the active metals used in the CHDA preparation process are basically noble metal Ru. Therefore, the dispersion of noble metals in the support is very important. Currently, the activity mainly affects the conversion rate of raw material PPDA and does not affect the selectivity of trans-CHDA. Since CHDA has two configurations, cis and trans, and the molecular sizes of the two configurations are also different, and the molecular structure of trans-CHDA is relatively more symmetrical than that of cis-CHDA and is easier to pass through the catalyst pores. Therefore, designing a catalyst with a suitable pore structure can improve the selectivity of trans-CHDA. Currently, supports with small pore structures such as activated carbon have characteristics such as being not wear-resistant and difficult to settle, while most of the pore channels of the commonly used support alumina are mesopores, which cannot disperse the active metal well and are difficult to stably adjust the pore channels. This patent uses an organic substance combined with alumina to form a microporous polymer in the mesopores of alumina, so that the catalyst has both wear resistance and a suitable pore structure. Summary of the Invention

[0009] In order to increase the content of trans in current CHDA and thus improve the properties of polyurethane, the present invention provides a hydrogenation catalyst with high trans-CHDA selectivity and a process for liquid-phase catalytic hydrogenation of PPDA. The catalyst prepared by the present invention can be continuously reused for more than 20 batches when using a batch reactor for the hydrogenation reaction. While ensuring a high conversion rate of PPDA, the yield of trans-CHDA can reach more than 95%.

[0010] On the one hand, the present invention provides a hydrogenation catalyst, which comprises an active metal and a modified support. The active metal is selected from one or more of Ru, Rh, Ni, Pt, and Pd; the modified support is a composite alumina support with a microporous structure.

[0011] In the present invention, the mass ratio of the active metal to the modified support is 0.5%-3%.

[0012] In the present invention, the modified support is alumina modified by metal-organic framework (MOF) or covalent organic framework (COF).

[0013] The preparation method is as follows: Weigh mesoporous γ-Al2O3 powder and metal-organic framework (MOF) or covalent organic framework (COF) into a container, add deionized water and stir for modification; after the modification is completed, filter and dry; calcine the dried mixture to obtain the modified support.

[0014] In the present invention, the average pore diameter of the modified support is 1.5 - 3 nm, and the specific surface area is 600 - 1800 m 2 / g.

[0015] In the present invention, the γ-Al2O3 in the modified support adopts ultrafine mesoporous alumina, and its BET is 100 - 240 m 2 / g, and the pore diameter is 15 - 60 nm.

[0016] In the present invention, the metal-organic framework (MOF) or covalent organic framework (COF) in the modified support is one or more of COF-1, COF-102, and MIL-53; among them, the BET of the COF-102 material is 3000 - 3472 m 2 / g, and the average pore diameter is 0.9 - 1.1 nm; the BET of the COF-1 material is 711 - 820 m 2 / g, and the average pore diameter is 1.7 - 2.2 nm; the BET of the MIL-53 material is 870 - 1000 m 2 / g, and the average pore diameter is 1.4 - 1.6 nm.

[0017] The mass ratio of the metal-organic framework (MOF) or covalent organic framework (COF) to alumina is 0.5 - 1.5, and the modification time is 8 - 48 h.

[0018] The drying is vacuum drying, the temperature is 60 - 80 °C, and the drying time is 6 - 12 h.

[0019] The calcination uses a muffle furnace for calcination, the temperature is 200 - 500 °C, the atmosphere is nitrogen, and the calcination time is 1 - 4 h.

[0020] In the second aspect, the present invention provides a method for preparing the catalyst, and the method includes the following steps: adding the modified support into deionized water and continuously stirring to obtain a suspension, weighing RuCl3 powder and Ni(acac)2 powder and adding them into a solvent to mix evenly to obtain an impregnation solution, dropping the impregnation solution into the support suspension and continuously stirring, drying all THF and water to obtain a uniform catalyst precursor; reducing the catalyst precursor with hydrogen in a tube furnace to obtain the catalyst.

[0021] The solvent is selected from one or more of THF, methanol, and dioxane;

[0022] The temperature of the hydrogen reduction is 200 - 400 °C, the time is 4 - 8 h, and the hydrogen flow rate is 50 - 200 mL / min.

[0023] Thirdly, the present invention provides a method for liquid-phase catalytic hydrogenation of PPDA, and the method comprises the following steps: using PPDA as a raw material, in a solution of a solvent and an auxiliary agent, PPDA reacts with hydrogen under the action of a hydrogenation catalyst to generate CHDA.

[0024] The solvent is selected from one or more of tetrahydrofuran, methanol, ethanol, propanol, isopropanol, n-butanol, ethyl acetate, and butyl acetate.

[0025] The auxiliary agent is selected from one or more of metal oxides or hydroxides such as Li, K, Ca, etc.

[0026] The mass fraction of PPDA in the solvent is 5-20%, the addition amount of the auxiliary agent relative to the mass fraction of the catalyst is 1%-5%, and hydrogen is fed continuously.

[0027] The reaction temperature is 100-180°C, the reaction time is 30-300 min, and the hydrogen pressure is 3-8 MPa.

[0028] The present invention has the following advantages compared with the prior art:

[0029] 1. The catalyst carrier of the present invention is a composite carrier. Compared with activated carbon, its mechanical strength is significantly improved, and the rate of catalyst pulverization is reduced; compared with the alumina carrier, the catalyst has richer pores and a moderate pore size, which is beneficial to improving the selectivity of the product.

[0030] 2. The active components of the catalyst of the present invention use Ru and Ni as active components, and the characteristic is that a large amount of alloy is not formed, so that the dispersion of the active metal is better, the adsorption capacity of hydrogen is increased, and thus the catalyst activity is increased.

[0031] 3. Compared with the catalyst for modifying pores in a solution, the microporous compound of the present invention is directly immobilized on the inner surface of the catalyst, so the stability is greatly increased, and it can be continuously used for more than 10 batches. Specific Embodiments

[0032] Raw materials and sources: The main raw materials used in the following examples or comparative examples are sourced as follows. Unless otherwise specified, others are all ordinary commercially available raw materials. COF-1, COF-102, and MIL-53 were purchased from Xi'an Ruixi Biotechnology Co., Ltd. The BET of the COF-102 material is 3472 m 2 / g, and the average pore diameter is 1.1 nm; the BET of the COF-1 material is 711 m 2 / g, and the average pore diameter is 1.7 nm; the BET of the MIL-53 material is 1000 m 2 / g, with an average pore size of 1.4 nm. The mesoporous γ-Al2O3 powder was purchased from Yangzhou Zhongtianli New Materials Co., Ltd., and its BET was 100 m 2 / g, with a pore size of 15 nm. The main equipment information is as follows:

[0033] Test method: The conditions for gas chromatography analysis in the following examples were as follows: Agilent 7890 and DB-5 were used The injector temperature was 280 °C, and the detector temperature was 300 °C. The temperature programming was as follows: The initial column temperature was 50 °C and held for 2 min; it was heated to 80 °C at a rate of 5 °C / min and held for 0 min; it was heated to 300 °C at a rate of 15 °C / min and held for 15 min. The content of each component was determined by the normalization method.

[0034] The specific surface area and pore size distribution of the sample were measured on a physical adsorption instrument (Quantachrome Autosorb-1 instrument). Before analysis, about 50 mg of the sample was degassed at 300 °C under vacuum for 3 h. The specific surface area was obtained by the Brunauer-Emmett (BET) method from the data in the range of the adsorption isotherm P / P0 = 0.05 - 0.30; the pore size distribution was obtained from the desorption isotherm.

[0035] Example 1

[0036] First, 3 g of mesoporous γ-Al2O3 powder and 5 g of COF-102 powder were weighed into a three-necked flask, and 200 mL of water was added and stirred at 40 °C for 12 h. Then, filtration was carried out, and vacuum drying was carried out at 80 °C for 8 h to remove the moisture on the surface of the mixture. The dried mixture was calcined under the condition of calcining in a nitrogen atmosphere at 300 °C for 2 h to obtain a catalyst support.

[0037] This 3 g of support was added to 200 g of deionized water and continuously stirred. RuCl3 powder and Ni(acac)2 powder (the mass fractions of Ru and Ni relative to the support were 0.5% and 1%) were weighed and added to 20 g of THF solution and mixed evenly to obtain an impregnation solution. The impregnation solution was dropped into the ultrasonic and stirred support suspension at a rate of 1 drop / second, and continuous stirring was carried out for 12 h after dropping. THF and water were all dried using rotary evaporation at 80 °C to obtain a uniform catalyst precursor. The precursor was reduced with hydrogen in a tubular furnace to obtain a catalyst, with a reduction temperature of 300 °C, a reduction time of 5 h, and a hydrogen flow rate of 100 mL / min. The pore size of the prepared catalyst was 2.5 nm.

[0038] Reaction process: Add 2 g of catalyst, 25 g of 1,4-phenylenediamine, 278 g of tetrahydrofuran, and 0.05 g of auxiliary LiOH into the reaction kettle. Close the reaction kettle, replace the air in the kettle with 0.6 MPa of nitrogen three times, and then replace the nitrogen in the kettle with 1 MPa of hydrogen three times. Pressurize the hydrogen to 8 MPa, turn on the reaction kettle and heat it to a reaction temperature of 140 °C, and carry out the constant-temperature reaction for 2 h. Wait until the temperature in the kettle drops to room temperature, filter out the reaction solution for gas chromatography analysis. Filter the catalyst and reuse it for 10 batches to investigate its stability.

[0039] Example 2

[0040] Replace 5 g of COF-102 with COF-1, and keep other conditions the same as in Example 1. The average pore diameter of the prepared catalyst is 3.8 nm.

[0041] Example 3

[0042] Replace 5 g of COF-102 with MIL-53(Al), and keep other conditions the same as in Example 1. The average pore diameter of the prepared catalyst is 3 nm.

[0043] Example 4

[0044] Replace 5 g of COF-102 powder with 3 g, and keep other conditions the same as in Example 1. The average pore diameter of the prepared catalyst is 5 nm.

[0045] Example 5

[0046] Replace 5 g of COF-102 powder with 7 g, and keep other conditions the same as in Example 1. The average pore diameter of the prepared catalyst is 1.9 nm.

[0047] Example 6

[0048] Replace the calcination temperature with 200 °C and the calcination time with 2 h, and keep other conditions the same as in Example 1. The average pore diameter of the prepared catalyst is 1.7 nm.

[0049] Example 7

[0050] Replace the calcination temperature with 500 °C and the calcination time with 2 h, and keep other conditions the same as in Example 1. The average pore diameter of the prepared catalyst is 7 nm.

[0051] Example 8

[0052] Replace the calcination time with 1 h, and keep other conditions the same as in Example 1. The average pore diameter of the prepared catalyst is 2.1 nm.

[0053] Example 9

[0054] Change the calcination time to 4 h, and keep other conditions the same as in Example 1. The average pore diameter of the prepared catalyst is 4.5 nm.

[0055] Example 10

[0056] Change the mass fractions of Ru and Ni relative to the support to 0.5% and 2%, respectively, and keep other conditions the same as in Example 1. The average pore diameter of the prepared catalyst is 3.2 nm.

[0057] Example 11

[0058] Change the mass fractions of Ru and Ni relative to the support to 0.5% and 0.5%, respectively, and keep other conditions the same as in Example 1. The average pore diameter of the prepared catalyst is 2.4 nm.

[0059] Example 12

[0060] Change the reaction temperature from 140 °C to 130 °C, and keep other conditions the same as in Example 1.

[0061] Example 13

[0062] Change the reaction temperature from 140 °C to 150 °C, and keep other conditions the same as in Example 1.

[0063] Comparative Example 1

[0064] Omit the COF-102 powder, and keep other conditions the same as in Example 1. The pore diameter of the prepared catalyst is 14.2 nm.

[0065] Comparative Example 2

[0066] Change 5 g of the COF-102 powder to 9 g, and keep other conditions the same as in Example 1. The average pore diameter of the prepared catalyst is 1.9 nm. The pore diameter of the prepared catalyst is 1.5 nm.

[0067] Comparative Example 3

[0068] Omit the mesoporous γ-Al2O3, and keep other conditions the same as in Example 1. The pore diameter of the prepared catalyst is 1.0 nm.

[0069]

Claims

1. A hydrogenation catalyst, which comprises an active metal and a modified support. The active metal is selected from one or more of Ru, Rh, Ni, Pt, and Pd; the modified support is a composite alumina support with a microporous structure.

2. The hydrogenation catalyst according to claim 1, wherein The mass ratio of the active metal to the modified support is 0.5%-3%.

3. The hydrogenation catalyst according to claim 1, characterized in that, The modified support is alumina modified by metal-organic framework (MOF) or covalent organic framework (COF), and its preparation method is as follows: Weigh mesoporous γ-Al2O3 powder and metal-organic framework (MOF) or covalent organic framework (COF) into a container, add deionized water and stir for modification; after the modification is completed, filter and dry; calcine the dried mixture to obtain the modified support.

4. The hydrogenation catalyst according to claim 3, wherein The average pore diameter of the modified support is 1.5 - 3 nm, and the specific surface area is 600 - 1800 m 2 / g; and / or, the γ-Al2O3 in the modified support is ultrafine mesoporous alumina with a BET of 100 - 240 m 2 / g and a pore diameter of 15 - 60 nm.

5. The hydrogenation catalyst according to claim 3 or 4, characterized in that, The metal-organic framework (MOF) or covalent organic framework (COF) in the modified support is one or more of COF-1, COF-102, and MIL-53; preferably, the BET of the COF-102 material is 3000-3472 m 2 / g, and the average pore diameter is 0.9-1.1 nm; the BET of the COF-1 material is 711-820 m 2 / g, and the average pore diameter is 1.7-2.2 nm; the BET of the MIL-53 material is 870-1000 m 2 / g, and the average pore diameter is 1.4-1.6 nm.

6. The hydrogenation catalyst according to any one of claims 3 to 5, characterized in that The mass ratio of the metal-organic framework (MOF) or covalent organic framework (COF) to alumina is 0.5-1.5; and / or, the modification time is 8-48 h; and / or, the drying is vacuum drying, the temperature is 60-80 °C, and the drying time is 6-12 h; and / or, the calcination is carried out in a muffle furnace, the temperature is 200-500 °C, the atmosphere is nitrogen, and the calcination time is 1-4 h.

7. The preparation method of the hydrogenation catalyst according to any one of claims 1-6, characterized in that, The method comprises the following steps: Add the modified support to deionized water and continuously stir to obtain a suspension. Weigh RuCl3 powder and Ni(acac)2 powder, add them to a solvent and mix evenly to obtain an impregnation solution. Drop the impregnation solution into the carrier suspension and continuously stir. Dry all THF and water to obtain a uniform catalyst precursor; reduce the catalyst precursor with hydrogen in a tube furnace to obtain the catalyst. Preferably, the solvent is selected from one or more of THF, methanol, and dioxane; the temperature of the hydrogen reduction is 200-400 °C, the time is 4-8 h, and the hydrogen flow rate is 50-200 mL / min.

8. A method for the liquid-phase catalytic hydrogenation of PPDA, which comprises the following steps: Using PPDA as a raw material, in a solution of a solvent and an auxiliary agent, PPDA reacts with hydrogen under the action of a hydrogenation catalyst to generate CHDA, and the hydrogenation catalyst is selected from the hydrogenation catalyst according to any one of claims 1-6.

9. The method according to claim 8, characterized in that, The solvent is selected from one or more of tetrahydrofuran, methanol, ethanol, propanol, isopropanol, n-butanol, ethyl acetate, and butyl acetate; and / or, the auxiliary agent is selected from one or more of metal oxides or hydroxides such as Li, K, and Ca.

10. The method according to claim 8 or 9, characterized in that The mass fraction of PPDA in the solvent is 5-20%, the addition amount of the auxiliary agent relative to the mass fraction of the catalyst is 1%-5%, and hydrogen is fed continuously; and / or, the reaction temperature is 100-180 °C, the reaction time is 30-300 min, and the hydrogen pressure is 3-8 MPa.

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