Method for preparing 1, 3-cyclohexane dimethylamine through continuous hydrogenation reaction of isophthalonitrile

Abstract

The invention discloses a method for preparing 1, 3-cyclohexane dimethylamine through continuous hydrogenation reaction of isophthalonitrile, and belongs to the technical field of fine chemical engineering. Two-stage hydrogenation is carried out under the same solvent, in the first-stage hydrogenation, Raney nickel is used as a catalyst, isophthalonitrile is dissolved in a solvent containing sodium hydroxide, the solution enters a reaction kettle in a solution form to be in contact with the catalyst for hydrogenation reaction, and an m-xylylenediamine reaction solution is prepared. In the second-stage hydrogenation, ruthenium-supported aluminum oxide is used as a catalyst, the m-xylylenediamine reaction liquid and hydrogen continue to react, 1, 3-cyclohexanedimethanol is prepared, and the total yield can reach 92%. According to the method, the solubility of the solvent to the raw materials is improved by using the sodium hydroxide, and the 1, 3-cyclohexanedimethylamine is prepared through continuous hydrogenation of the isophthalonitrile in the same solvent system, so that compared with the prior art, the refining process of the isophthalonitrile is reduced, continuous feeding can be realized, and the method has a good industrial application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of fine chemicals, and particularly to a method for efficiently and highly selectively preparing 1,3-cyclohexanedimethanamine by continuous hydrogenation reaction of isophthalonitrile. Background Art

[0002] The preparation methods of 1,3-cyclohexanedimethanamine mainly include phthalonitrile hydrogenation method, cyclohexanedimethanol hydroamination method, and phthalylenediamine hydrogenation method. Among them, the process route of directly using isophthalonitrile as the raw material to prepare 1,3-cyclohexanedimethanamine in one pot is to carry out two reactions of hydrogenating isophthalonitrile to prepare isophthalylenediamine and further hydrogenating isophthalylenediamine to prepare 1,3-cyclohexanedimethanamine simultaneously in the same reactor under the same conditions. Patent US5371293 uses 5wt% supported Ru-C or Ru-Al2O3 alumina as the catalyst, and carries out the hydrogenation reaction of isophthalonitrile to prepare 1,3-cyclohexanedimethanamine in a reaction system in the presence of dioxane and liquid ammonia. Patent US4070399 uses 5% supported Ru-Pd / C as the catalyst, uses lower aliphatic alcohols, dioxane, lower aliphatic amines, etc. as solvents, and uses liquid ammonia as an auxiliary agent to carry out the hydrogenation reaction of terephthalonitrile to prepare 1,4-cyclohexanedimethanamine. Patent US3998881 uses 5wt% supported rhodium alumina as the catalyst, and uses dioxane, tetrahydrofuran, chloroform, etc. as solvents to carry out the hydrogenation reaction of isophthalonitrile to prepare 1,3-cyclohexanedimethanamine, and the total yield after rectification is 71%.

[0003] In summary, the main problems of the one-pot method are that the two-step hydrogenation reactions are carried out simultaneously, making the reaction process complex, the catalyst is prone to poisoning, and the selectivity is difficult to improve.

[0004] At present, in order to improve the product selectivity, avoid experiencing the intermediate step of hydrogenating the cyano group to form an imine, and reduce the occurrence of side reactions, the mainstream research chooses the route of hydrogenating isophthalylenediamine as the raw material to prepare 1,3-cyclohexanedimethanamine. Patent CN117534572A uses isophthalylenediamine as the raw material, Pt / Pd-C as the main catalyst, and LrI4 as the co-catalyst. Patent CN113045431A uses Ru / Al-C as the main catalyst and adds lithium basic aluminum carbonate as a modification assistant. Patent CN112169832A discloses a catalyst prepared by the isomorphous substitution method for the hydrogenation of isophthalylenediamine to synthesize 1,3-cyclohexanedimethanamine. The catalyst carrier is SAPO-11 mesoporous molecular sieve, the active component is metal Ru, and the promoter is one or more of Pr, Nd, Mo, Lu, Tm, and uses organic amines such as diethylamine and diisopropylamine as the template agent.

[0005] In summary, currently, this route avoids the problems in the one-pot method where the two-step hydrogenation reactions occur simultaneously, making the reaction complex with numerous side reactions and affecting the product selectivity. However, the catalysts involved in this route currently have complex preparation processes, and the precious metals and rare earth elements used are expensive. m-Xylylenediamine itself is prepared by hydrogenating m-phthalonitrile, which requires multiple reactors and separation equipment. The separation and purification of intermediate products increase energy consumption and operating costs, and the process flow is long. These factors increase the production cost of this route and limit its application in large-scale production.

[0006] Patent CN107868007A discloses a process for preparing 1,3-cyclohexanedimethanamine by two-stage hydrogenation in the same solvent. In the first stage of hydrogenation, Raney nickel is used as the catalyst, and one or more of methanol, methylamine, 1,4-dioxane are used as the solvent, and organic amine, liquid ammonia, water or sodium hydroxide is used as the auxiliary agent to react to obtain a reaction solution of m-xylylenediamine. In the second stage of hydrogenation, activated carbon loaded with ruthenium is used as the catalyst, and the reaction solution of m-xylylenediamine and hydrogen continue to react to prepare 1,3-cyclohexanedimethanamine.

[0007] Currently, there is little research on the two-step hydrogenation reaction of m-phthalonitrile in the same solvent system. Although the research in patent CN107868007A uses the same solvent for the two-step hydrogenation reaction, it does not mention the solubility of m-phthalonitrile in the solvent. The solubility of m-phthalonitrile in most solvents is low, and current research rarely involves the influence of the solubility of m-phthalonitrile in the solvent on the hydrogenation reaction, while the low-concentration reaction solution or heterogeneous feed imposes certain limitations on the application of this process. Summary of the Invention

[0008] The object of the present invention is to address the above problems, and provides a method for enhancing the solubility of m-phthalonitrile in the solvent, and preparing 1,3-cyclohexanedimethanamine by two-step hydrogenation in this solvent system.

[0009] The present invention is achieved through the following technical solutions: The present invention provides a method for enhancing the solubility of m-phthalonitrile in the solvent. One or more of methanol, ethanol, toluene, xylene, m-xylylenediamine are formulated into a solution in a certain proportion, a certain amount of sodium hydroxide is added, and a certain amount of m-phthalonitrile is added with stirring at 60 - 70 °C. After the solid is completely dissolved, the solution is cooled to room temperature to obtain an m-phthalonitrile solution, wherein the solvent is preferably ethanol, and the mass fraction of sodium hydroxide is 0 - 0.125 wt%, preferably 0.1 wt%.

[0010] The present invention provides a method for preparing 1,3-cyclohexanedimethanamine by two-step hydrogenation reaction using the above m-phthalonitrile solution as the raw material, specifically as follows: The raw material containing isophthalonitrile enters the autoclave reactor in the form of a solution, contacts with Raney nickel for hydrogenation reaction. The reaction temperature is 60 - 80 °C, the reaction pressure is 3 - 5 MPa, and the reaction is carried out for 0.5 - 3 h to obtain m-xylylenediamine. The preferred conditions are: the mass fraction of isophthalonitrile in the solution is 10 wt%, Raney nickel accounts for 20 wt% of the mass of isophthalonitrile, the reaction temperature is 60 °C, the reaction pressure is 3 MPa, and the reaction time is 130 min.

[0011] The m-xylylenediamine solution obtained from the first-step hydrogenation reaction is collected by centrifugal separation and then put into the autoclave reactor again, contacts with the Ru-based supported catalyst for hydrogenation reaction. At a reaction temperature of 90 - 120 °C and a reaction pressure of 4 - 6 MPa, the reaction is carried out for 0.5 - 1.5 h to obtain 1,3-cyclohexanediamine. Among them, for the Ru-based supported catalyst, one or several of alumina, calcium oxide, magnesium oxide, and chromium oxide are used as the carrier, and the loading amount of Ru is 1 - 4 wt%. The preferred conditions are that the Ru loading amount is 4 wt%, the carrier is alumina, the mass of the catalyst accounts for 20 wt% of the mass fraction of m-xylylenediamine, the reaction temperature is 95 °C, the reaction pressure is 5 MPa, and the reaction time is 100 min.

[0012] The preparation method of the Ru-based supported catalyst of the present invention is one or a combination of two or more of the excess impregnation method, ultrasonic-assisted equal-volume impregnation method, and ultrasonic-assisted strong electrostatic adsorption method.

[0013] The present invention uses sodium hydroxide to increase the solubility of the solvent in the raw material, and realizes the continuous hydrogenation of isophthalonitrile in the same solvent system to prepare 1,3-cyclohexanediamine. Compared with the existing process, the purification process of isophthalonitrile is reduced, continuous feeding can be realized, and the maximum yield of 1,3-cyclohexanediamine obtained by the reaction in the autoclave reactor is 92%, having good industrial application prospects.

[0014] The beneficial effects of the present invention are as follows: 1. Using sodium hydroxide as an additive to increase the solubility of isophthalonitrile in ethanol to meet the requirements of continuous feeding and discharging in industrial production, and at the same time, it can improve the selectivity of the reaction to the target product and increase the yield of 1,3-cyclohexanediamine. Compared with the liquid ammonia scheme in the traditional process, the reaction system with sodium hydroxide as an additive is more stable, the operation is simple, and the danger is lower; 2. The present invention uses ethanol as a solvent, which has the advantages of low cost, wide source, low toxicity, and moderate volatility compared with solvents such as tetrahydrofuran, dioxane, methanol, and methylamine used in the existing process; 3. Using ethanol as a solvent to realize the efficient continuous two-step hydrogenation of isophthalonitrile to prepare 1,3-cyclohexanediamine, with a yield of 92%, reducing the intermediate distillation steps, simplifying the operation, shortening the production cycle, and reducing the cost. Description of the Drawings

[0015] Figure 1 They are the infrared spectra of the isophthalonitrile-ethanol mixed solution containing 0.1 wt% sodium hydroxide and the saturated ethanol solution of isophthalonitrile without adding sodium hydroxide.

[0016] Figure 2 is in Example 5 of 4Ru / γ -Al2O3-UW and 4Ru / γ -Al2O3-EG X-ray diffraction spectra.

[0017] Figure 3 is in Example 5 of 4Ru / γ -Al2O3-UW and 4Ru / γ -Al2O3-EC X-ray photoelectron spectroscopy. Specific embodiments

[0018] The present invention will be further described below in conjunction with the embodiments. Example 1

[0019] Weigh 20 g of ethanol using a conical flask, dissolve 20 mg of sodium hydroxide, add 1 - 4 g of isophthalonitrile solid, and while heating and stirring with a heating plate under a reflux condenser until the solid is completely dissolved, then stop heating until the solid starts to precipitate, and record the precipitation temperature. The recording results are shown in Table 1.

[0020] Table 1 Solubility test of isophthalonitrile in the sodium hydroxide & ethanol system

[0021] The dissolution ability of isophthalonitrile in the ethanol solution containing 0.1 wt% sodium hydroxide is greatly improved under normal pressure. The maximum solubility increases from 5 wt% to 17 wt%, and the solid precipitation temperature decreases from 70 °C to 45 °C. By adding sodium hydroxide to improve the dissolution ability of ethanol for isophthalonitrile, the problem that alcohol solvents have poor dissolution ability for isophthalonitrile is solved, and the application of alcohol solvents in the hydrogenation reaction of nitrile compounds is broadened.

[0022] Analyze the infrared characterization results ( Figure 1 ), compared with the solution without adding sodium hydroxide, the isophthalonitrile-ethanol mixed solution containing 0.1 wt% sodium hydroxide has a new sharp strong peak at about 1700 cm -1 This peak should be the stretching vibration peak of C=O, proving that sodium hydroxide improves the solubility of IPN in ethanol by promoting the partial alkaline hydrolysis of IPN to form carboxylate ( ). Example 2

[0023] Activation of Raney nickel: Under magnetic stirring, 10 g of nickel-aluminum alloy powder (Raney nickel) was slowly added in portions to 50 mL of 20 wt% sodium hydroxide solution. Subsequently, the temperature was raised to 90 °C with stirring and maintained for 1 h to complete the activation. Then it was washed with deionized water until neutral, and the activated catalyst was stored in water to maintain its activity. Raney cobalt catalyst was activated in the same way.

[0024] Catalyst performance test: A autoclave reactor was used, and the catalyst was applied to the hydrogenation of isophthalonitrile. The reaction conditions were: 0.2 g of isophthalonitrile, 0.04 g of catalyst, 0.002 g of sodium hydroxide, and 18 g of ethanol. The reaction results are shown in Table 2.

[0025] Table 2 Performance comparison of Raney nickel / Raney cobalt in the catalytic hydrogenation of isophthalonitrile

[0026] Raney nickel showed higher reactivity in the hydrogenation of nitriles and could complete the hydrogenation reaction more rapidly under milder reaction conditions. In the presence of sodium hydroxide additive, the final yield of m-xylenediamine reached 98.7%. Example 3

[0027] Preparation of Ru-based catalyst: First, the support was pretreated. 10 g of γ γ-Al2O3 support was placed in a muffle furnace and heated to 300 °C at a rate of 10 °C / min in an air atmosphere and maintained for 4 h to remove as many possible impurities as possible. In addition, the theoretical loading of the catalyst active component was 4 wt% (based on the total mass of the catalyst). Catalyst 1

[0028] Ultrasonic-assisted incipient wetness impregnation method: First, 2 g of γ γ-Al2O3 was weighed into a beaker, and 0.16 g of RuCl3·3H2O was dissolved in water to form an aqueous solution (ensuring that the prepared solution just reached the γ γ-Al2O3 saturated water absorption), and it was added dropwise with stirring into γIn -Al2O3, it was ultrasonically treated for 30 min, aged for 12 h under vacuum conditions, then washed successively with deionized water and ethanol, and dried in vacuum at 60 °C for 12 h. After grinding, it was sieved through a 80 - mesh sieve to obtain a precursor sample. The sample was placed in a muffle furnace and heated to 400 °C at a rate of 10 °C / min in an air atmosphere and maintained for 5 h. After cooling to room temperature, it was placed in a tubular reduction furnace for reduction. The conditions were as follows: under a N2 atmosphere with a flow rate of 30 mL / min, heated to 250 °C at a rate of 5 °C / min, and reduced in a H2 atmosphere with a flow rate of 20 mL / min for 6 h, and then cooled to room temperature in a N2 atmosphere and aged for 12 h in a N2 atmosphere. The prepared catalyst was named 4Ru / γ -Al2O3 - UW.

[0029] In the preparation of the precursor sample, after aging for 12 h, it was directly dried in vacuum at 60 °C for 12 h to obtain an unwashed precursor sample. The catalyst prepared from it was named 4Ru - γ -Al2O3 - U, and 4Ru - CaO - U, 4Ru - ZrO2 - U, 4Ru - MgO - U were prepared by the same method. Catalyst Two

[0030] Excessive impregnation method: Weigh 0.16 g of RuCl3·3H2O and dissolve it in 60 mL of deionized water, add 2 g of γ -Al2O3 and stir at 60 °C for 12 h until the liquid is completely volatilized. Then, it was centrifuged by a centrifuge, and then washed successively with deionized water and ethanol, and dried in vacuum at 60 °C for 12 h. After grinding, it was sieved through a 80 - mesh sieve to obtain a precursor sample. The sample was placed in a muffle furnace and heated to 400 °C at a rate of 10 °C / min in an air atmosphere and maintained for 5 h. After cooling to room temperature, it was placed in a tubular reduction furnace for reduction. The conditions were as follows: under a N2 atmosphere with a flow rate of 30 mL / min, heated to 250 °C at a rate of 5 °C / min, and reduced in a H2 atmosphere with a flow rate of 20 mL / min for 6 h, and then cooled to room temperature in a N2 atmosphere and aged for 12 h in a N2 atmosphere. The prepared catalyst was named 4Ru / γ -Al2O3 - SW.

[0031] As a control, the sample after centrifugation by the centrifuge was directly dried. The catalyst prepared from the unwashed precursor sample was named 4Ru / γ -Al2O3 - S. Catalyst Three

[0032] Strong electrostatic adsorption - chemical reduction method: Take 1 g of γ-Al2O3 was added to 30 mL of 0.01 M NaOH solution and sonicated for 0.5 h. Subsequently, the pH was adjusted to maintain the pH of the supernatant at around 10. 10 mL of an aqueous solution containing 0.08 g of RuCl3·3H2O was added, and the pH of the solution was maintained at 8 - 9. Sonication was continued for 2 h until the supernatant became clear to obtain the catalyst precursor. Subsequently, 8 mL of 0.1 M NaBH4 solution (n(Ru 3+ ):(NaBH4)=1:10) was added with stirring, and the mixture was stirred for 2 h. Then it was washed successively with deionized water and ethanol and dried in vacuo at 60 °C for 12 h. The prepared catalyst was named 4Ru / γ -Al2O3-EC.

[0033] As a control, the precursor was washed successively with deionized water and ethanol, dried in vacuo at 60 °C for 12 h, ground, passed through an 80-mesh sieve, and placed in a tubular reduction furnace for reduction. The conditions were as follows: under a N2 atmosphere at a flow rate of 30 mL / min, heated to 250 °C at a rate of 5 °C / min, reduced in a H2 atmosphere at a flow rate of 20 mL / min for 6 h, then cooled to room temperature in a N2 atmosphere, and aged in a N2 atmosphere for 12 h. The prepared catalyst was named 4Ru / γ -Al2O3-EG. Example 4

[0034] Performance test of catalysts prepared with different supports: A autoclave reactor was used, and the catalyst was applied to the hydrogenation of m-xylenediamine. The reaction conditions were as follows: 0.25 g of m-xylenediamine, 0.05 g of catalyst, 18 g of ethanol, a pressure of 5 MPa, a temperature of 95 °C, and the reaction time was 70 min. The reaction results are shown in Table 3.

[0035] Table 3 Effects of different supports on the reaction of m-xylenediamine

[0036] The catalyst prepared using alumina as the support showed the best catalytic performance in the reaction of hydrogenating m-xylenediamine to prepare 1,3-cyclohexanediamine. This may be due to the fact that alumina has a large specific surface area and moderate acidic sites, which can make Ru more evenly distributed. Example 5

[0037] Performance test of catalysts prepared with different preparation methods: A autoclave reactor was used, and the catalyst was applied to the hydrogenation of m-xylenediamine. The reaction conditions were as follows: 0.25 g of m-xylenediamine, 0.05 g of catalyst, 18 g of ethanol, a pressure of 5 MPa, a temperature of 95 °C, and the reaction time was 70 min. The reaction results are shown in Table 4.

[0038] Table 4 Effects of different preparation methods on the reaction of m-xylenediamine

[0039] The test results show that the catalyst 4Ru / γ -Al2O3-UW prepared by ultrasonic-assisted equal-volume impregnation method exhibits high reactivity in the reaction of preparing 1,3-cyclohexanediamine from m-xylylenediamine, and at the same time has the highest selectivity for 1,3-cyclohexanediamine. Without using sodium hydroxide as an additive and using pure m-xylylenediamine as the raw material, the selectivity for the target product reaches 89.0%.

[0040] Analyzing the X-ray diffraction characterization results ( Figure 2 ), no obvious characteristic peaks of ruthenium appear in 4Ru / γ -Al2O3-EG, indicating that the ruthenium in the catalyst prepared by the strong electrostatic adsorption method is evenly distributed and has a smaller particle size. This may be the reason for its high activity. However, m-xylylenediamine has multiple hydrogenation sites, and aromatic ring hydrogenation has certain requirements for the particle size of the active component. Too small a particle size may not be conducive to the reaction proceeding in the direction of aromatic ring hydrogenation. Therefore, 4Ru / γ -Al2O3-EG has poor selectivity for 1,3-cyclohexanediamine.

[0041] Analyzing the X-ray photoelectron spectroscopy characterization results ( Figure 3 ), compared with 4Ru / γ -Al2O3-EC, after 4Ru / γ -Al2O3-UW is reduced by H2 gas phase, Ru can be more fully reduced to Ru 0 , which can explain the reason for the poor activity of 4Ru / γ -Al2O3-EC prepared by the chemical reduction method. Example 6

[0042] Add 10 g of ethanol solution containing 10 wt% m-xylylene dinitrile and 0.1 wt% sodium hydroxide to a batch reactor, contact with 0.2 g of Raney nickel for hydrogenation reaction. The reaction temperature is 60 °C, the reaction pressure is 3 MPa, and react for 130 min to obtain m-xylylenediamine. The m-xylylenediamine solution obtained from the first-step hydrogenation reaction is collected by centrifugal separation and then put into the batch reactor again, contact with 0.2 g of 4Ru / γ -Al2O3-UW for hydrogenation reaction. At a reaction temperature of 95 °C and a reaction pressure of 5 MPa, react for 100 min to obtain 1,3-cyclohexanediamine. The final yield of 1,3-cyclohexanediamine reaches 92%.

[0043] The above examples are only used to illustrate the present invention. Any equivalent transformation and improvement based on the technical solution of the present invention should not be excluded from the protection scope of the present invention.

Claims

1. A method for continuously hydrogenating isophthalonitrile to prepare 1,3 - cyclohexanedimethanamine, characterized in that: 1) Dissolve isophthalonitrile in a solvent containing sodium hydroxide at 60 - 70 °C to obtain a mixed solution; 2) Add the mixed solution to a batch reactor and contact with catalyst a for hydrogenation reaction. The reaction temperature is 60 - 80 °C, the reaction pressure is 3 - 5 MPa, and the reaction is carried out for 0.5 - 3 h to obtain m - xylylenediamine; 3) Collect the m - xylylenediamine solution by centrifugal separation, put it into a batch reactor, contact with catalyst b for hydrogenation reaction. At a reaction temperature of 90 - 140 °C and a reaction pressure of 4 - 6 MPa, the reaction is carried out for 0.5 - 2 h to obtain 1,3 - cyclohexanedimethanamine.

2. The method according to claim 1, wherein In the step 1), the solvent is one or several of methanol, ethanol, toluene, xylene, m - xylylenediamine.

3. The method according to claim 1, characterized in that In the step 1), the mass fraction of sodium hydroxide in the mixed solution is 0.01 - 0.125 wt%; the mass fraction of isophthalonitrile is 5 - 15 wt%.

4. The method according to claim 1, wherein In the step 2), the reaction temperature is 60 °C; the reaction pressure is 3 MPa; the reaction time is 130 min.

5. The method according to claim 1, wherein In the step 2), catalyst a is Raney nickel or Raney cobalt, and the mass fraction of the catalyst accounts for 15 - 25 wt% of the mass of isophthalonitrile.

6. The method according to claim 1, wherein In step 3), the reaction temperature is 90 - 140 °C, preferably 95 °C; the reaction pressure is 4 - 6 MPa, preferably 5 MPa; the reaction time is 0.5 - 1.5 h, preferably 1.3 h.

7. The method according to claim 1, characterized in that, In the step 3), the active component of catalyst b is Ru, the carrier is one or several of alumina, calcium oxide, magnesium oxide, zirconium oxide, and the mass fraction of the active component is 1 - 4 wt% of the catalyst. The mass fraction of the catalyst accounts for 20 wt% of the mass of m - xylylenediamine.

8. The method according to claim 7, characterized in that, In the step 3), the preparation method of catalyst b is excessive impregnation, ultrasonic - assisted equal - volume impregnation, strong electrostatic adsorption impregnation.

9. The method according to claim 8, wherein In the step 3), the preparation method of catalyst b adopts ultrasonic - assisted equal - volume impregnation, specifically: γ - The aqueous solution of Al2O3 and RuCl3 was subjected to equal-volume impregnation, ultrasonicated for 20 - 40 min, aged under vacuum conditions for 12 h, then washed, vacuum dried, ground and sieved to obtain a precursor sample; The precursor sample is placed in a muffle furnace and heated from room temperature to 350 - 450 °C at a rate of 5 - 10 °C / min in an air atmosphere and maintained for 4 - 6 h. After cooling to room temperature, it is put into a tubular reduction furnace for reduction. The conditions are as follows: in an N2 atmosphere, it is heated to 200 - 300 °C at a rate of 3 - 5 °C / min, and reduced in an H2 atmosphere with a flow rate of 10 - 30 mL / min for 4 - 8 h, and then cooled to room temperature in an N2 atmosphere and aged in an N2 atmosphere for 12 h to obtain the catalyst.

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