Preparation method of high-purity dibenzylamine

Abstract

The invention relates to the technical field of organic synthesis intermediates, and particularly discloses a preparation method of high-purity dibenzylamine, which comprises the following steps: firstly, carrying out Schiff base reaction on benzaldehyde, liquid ammonia and benzyl chloride to generate a Schiff base product N-benzylidene benzylamine, then reacting N-benzylidene benzylamine with hydrogen under the action of a hydrogenation catalyst to generate dibenzylamine, and finally, separating and purifying the dibenzylamine to obtain the high-purity dibenzylamine. Compared with a benzyl chloride method and the like, the preparation method of the high-yield dibenzylamine, provided by the invention, has the advantages of mild reaction conditions, high catalyst activity and stability, high product selectivity, high atom utilization rate, reusability of substances such as the catalyst and the solvent and less generated wastes, and accords with the environment-friendly theme of green and clean production.

Description

Technical Field

[0001] The present invention relates to the technical field of organic synthesis intermediates, and particularly to a method for preparing high-purity dibenzylamine. Background Art

[0002] Dibenzylamine is a secondary amine compound in which two benzyl groups are connected to an amino group. It usually appears as a colorless or light yellow oily liquid with an ammonia odor. It is easily soluble in organic solvents such as ethanol, ether, and chloroform, slightly soluble in water, and can be used as a determinate for cobalt, iron, and cyanate. Dibenzylamine is also an important organic synthesis intermediate, commonly used in the synthesis of penicillin and curing agents for rubber and plastics, or in the production of two highly efficient and non-toxic vulcanization accelerators, diphenyl disulfide tetrakis(benzylthiuram) (TBZTD) and zinc dibenzyldithiocarbamate (ZBEC). In addition, derivatives of dibenzylamine and pharmaceutical compositions containing the derivatives can be used to treat some cardiovascular diseases such as atherosclerosis.

[0003] There are many synthesis methods for dibenzylamine, such as the benzyl chloride method and the benzaldehyde method. Among them, in the benzyl chloride method, under the action of a catalyst, benzyl chloride and aniline undergo a condensation reaction to form dibenzylamine and by-product hydrogen chloride. This method has cheap raw materials and simple synthesis operation, but the yield of the main product is low, the yield of by-product trichlorobenzyl is high, and a large amount of three wastes are generated during the production process, seriously polluting the environment. The benzaldehyde method adopts the reduction hydrogenation theory of preparing a single secondary amine by catalyzing aldehyde or chlorine with a hydrogenation catalyst, and benzaldehyde, ammonia, and hydrogen react to form dibenzylamine and by-product water under the catalytic action of a hydrogenation catalyst. This method has a short reaction time, high product selectivity, and high product recovery rate, but it requires hydrogenation under pressure during the production process, and has relatively strict requirements for the reaction device and the operation level of personnel. Therefore, it is of great significance to develop a production method of dibenzylamine with simple process, high product purity, and high product yield. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing high-purity dibenzylamine, with a simple reaction process, little environmental pollution, high atom utilization rate, and solving the problems of low yield and low purity of dibenzylamine products.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] A method for preparing high-purity dibenzylamine, specifically as follows:

[0007] Step 1: Mix benzaldehyde, liquid ammonia, and benzyl chloride evenly, and react at 60 - 80 °C and 10 - 15 MPa for 4 - 6 h. After the reaction is completed, add deionized water to terminate the reaction, let it stand for stratification, and wash the oil phase with deionized water to obtain N-benzylidene benzylamine;

[0008] Step 2: Mix N-benzylidene benzylamine, ethanol, and Raney nickel catalyst evenly, introduce hydrogen gas, react at 90-120°C for 0.5-2 h. After the reaction is completed, cool, filter, distill the filtered filtrate to remove ethanol, benzylamine, and benzyl alcohol. Finally, raise the temperature to 300-310°C, rectify, and cool to obtain high-purity dibenzylamine.

[0009] As a limitation of the present invention, the mass ratio of benzaldehyde, liquid ammonia, and benzyl chloride is (3-7):(0.5-1.5):(4-8).

[0010] As a limitation of the present invention, the mass ratio of N-benzylidene benzylamine, ethanol, and Raney nickel catalyst is (8-10):(4-8):(0.05-0.2).

[0011] As a limitation of the present invention, in Step 1, the mass ratio of deionized water to terminate the reaction to liquid ammonia is 1:(0.8-1.2). Deionized water can be replaced by an equal volume of ammonia water, which is obtained by distilling the aqueous phase after static stratification and condensing.

[0012] As a limitation of the present invention, in the Raney nickel catalyst, the nickel content is 90%-100%. In Step 2, the Raney nickel catalyst can be filtered out and reused.

[0013] As a limitation of the present invention, in Step 2, the ethanol can be distilled from the filtered filtrate and reused, and the distillation temperature is controlled at 75-90°C.

[0014] As a limitation of the present invention, when removing benzylamine, the distillation temperature is controlled at 185-200°C.

[0015] As a limitation of the present invention, when removing benzyl alcohol, the distillation temperature is controlled at 205-220°C.

[0016] Reaction mechanism of the present invention: Under the condition of excessive ammonia, benzaldehyde first reacts with ammonia to form benzylideneimine (Schiff base intermediate) and water. Then benzylideneimine reacts with benzyl chloride under alkaline conditions to form N-benzylidene benzylamine and hydrogen chloride. N-benzylidene benzylamine reacts with hydrogen under the action of Raney nickel catalyst to hydrogenate to form dibenzylamine.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] The present invention provides a preparation method of high-purity dibenzylamine. This method uses benzaldehyde and benzyl chloride as raw materials, and catalytically hydrogenates to synthesize dibenzylamine under the action of Raney nickel catalyst. The reaction conditions are mild, the product selectivity is high, the atom utilization rate is high, and the generated waste is less, meeting the environmental protection theme of green and clean production.

[0019] The present invention uses a Raney nickel catalyst to catalyze the hydrogenation reaction of the intermediate N-benzylidene benzylamine. The catalyst has high catalytic activity and stable properties. During the reaction process, the by-products (benzylamine and benzyl alcohol) generated are few, and the selectivity for the product dibenzylamine is high, which is beneficial to the formation of dibenzylamine. This catalyst can catalyze the reaction to proceed at a relatively low temperature and pressure, with low reaction energy consumption, which is beneficial to large-scale production.

[0020] In addition to the recycled Raney nickel catalyst, in the preparation method provided by the present invention, the excessive ammonia and the solvent ethanol in the raw materials can also be recovered and reused by distillation and other methods, reducing the waste of resources and the generation of waste, and lowering the production cost. Specific Embodiments

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0022] Raney nickel catalyst (purity: Ni≥90%).

[0023] Example 1: A method for preparing high-purity dibenzylamine, specifically as follows:

[0024] Step 1: Add 500 g of benzaldehyde, 110 g of liquid ammonia, and 650 g of benzyl chloride to a high-pressure reactor. After mixing evenly, react at 70 °C and 12 MPa for 5 h. After the reaction is completed, add 100 g of deionized water to terminate the reaction, let it stand for stratification, wash the oil phase with deionized water to obtain N-benzylidene benzylamine, and distill the aqueous phase at 100 °C, cool it to obtain ammonia water that can be recycled.

[0025] Step 2: Transfer the N-benzylidene benzylamine prepared in Step 1 to another reaction kettle. At the same time, add 500 g of ethanol and 150 g of Raney nickel catalyst to the reaction kettle. After mixing evenly, introduce hydrogen gas and react at 110 °C for 1 h. After the reaction is completed, cool it, filter it to filter out the reusable Raney nickel catalyst. Heat the filtered filtrate to 80 °C, distill it to remove the reusable solvent ethanol, then heat it to 190 °C, distill benzylamine from the filtrate after removing the solvent, and then heat it to 210 °C, distill benzyl alcohol from the filtrate after removing the solvent, and finally heat it to 300 °C for rectification, cool it to obtain high-purity dibenzylamine.

[0026] Sample the product after the reaction in Step 2 and detect and analyze it by gas chromatography. The conversion rate of benzaldehyde is measured to be 100%, and the selectivity for dibenzylamine is 97.7%.

[0027] Example 2: A method for preparing high-purity dibenzylamine, specifically as follows:

[0028] Step 1: Add 500 g of benzaldehyde, 110 g of liquid ammonia, and 650 g of benzyl chloride into a high-pressure reactor. After mixing evenly, react at 70 °C and 12 MPa for 5 h. After the reaction is completed, add 100 g of deionized water to terminate the reaction. Let it stand for liquid separation. Wash the oil phase with deionized water to obtain N-benzylidene benzylamine. Distill the aqueous phase at 100 °C, cool it, and obtain ammonia water that can be recycled.

[0029] Step 2: Transfer the N-benzylidene benzylamine prepared in Step 1 to another reaction kettle. At the same time, add 500 g of ethanol and 130 g of Raney nickel catalyst into the reaction kettle. After mixing evenly, introduce hydrogen gas and react at 110 °C for 1 h. After the reaction is completed, cool it, filter it, and filter out the reusable Raney nickel catalyst. Heat the filtered filtrate to 80 °C, distill it to remove the reusable solvent ethanol. Then heat it to 190 °C and distill benzylamine from the filtrate after removing the solvent. Then heat it to 210 °C and distill benzyl alcohol from the filtrate after removing the solvent. Finally, heat it to 300 °C, rectify it, cool it, and obtain high-purity dibenzylamine.

[0030] Sample the product after the reaction in Step 2 and detect and analyze it by gas chromatography. The conversion rate of benzaldehyde is determined to be 100%, and the selectivity of dibenzylamine is 97.6%.

[0031] Example 3: A method for preparing high-purity dibenzylamine, specifically as follows:

[0032] Step 1: Add 500 g of benzaldehyde, 110 g of liquid ammonia, and 650 g of benzyl chloride into a high-pressure reactor. After mixing evenly, react at 70 °C and 12 MPa for 5 h. After the reaction is completed, add 100 g of deionized water to terminate the reaction. Let it stand for liquid separation. Wash the oil phase with deionized water to obtain N-benzylidene benzylamine. Distill the aqueous phase at 100 °C, cool it, and obtain ammonia water that can be recycled.

[0033] Step 2: Transfer the N-benzylidene benzylamine prepared in Step 1 to another reaction kettle. At the same time, add 500 g of ethanol and 80 g of Raney nickel catalyst into the reaction kettle. After mixing evenly, introduce hydrogen gas and react at 110 °C for 1 h. After the reaction is completed, cool it, filter it, and filter out the reusable Raney nickel catalyst. Heat the filtered filtrate to 80 °C, distill it to remove the reusable solvent ethanol. Then heat it to 190 °C and distill benzylamine from the filtrate after removing the solvent. Then heat it to 210 °C and distill benzyl alcohol from the filtrate after removing the solvent. Finally, heat it to 300 °C, rectify it, cool it, and obtain high-purity dibenzylamine.

[0034] Sample the product after the reaction in Step 2 and detect and analyze it by gas chromatography. The conversion rate of benzaldehyde is determined to be 100%, and the selectivity of dibenzylamine is 97.3%.

[0035] Example 4: A method for preparing high-purity dibenzylamine, specifically as follows:

[0036] Step 1: Add 500 g of benzaldehyde, 110 g of liquid ammonia, and 650 g of benzyl chloride into a high-pressure reactor. After mixing evenly, react at 70 °C and 12 MPa for 5 h. After the reaction is completed, add 100 g of deionized water to terminate the reaction, let it stand for layering, wash the oil phase with deionized water to obtain N-benzylidene benzylamine, and distill the aqueous phase at 100 °C, cool it to obtain ammonia water that can be recycled.

[0037] Step 2: Transfer the N-benzylidene benzylamine prepared in Step 1 to another reaction kettle. At the same time, add 500 g of ethanol and 50 g of Raney nickel catalyst into the reaction kettle. After mixing evenly, introduce hydrogen gas and react at 110 °C for 1 h. After the reaction is completed, cool it, filter it to filter out the reusable Raney nickel catalyst. Heat the filtered filtrate to 80 °C, distill it to remove the reusable solvent ethanol, then heat it to 190 °C to distill benzylamine from the filtrate after removing the solvent, then heat it to 210 °C to distill benzyl alcohol from the filtrate after removing the solvent, and finally heat it to 300 °C for rectification, cool it to obtain high-purity dibenzylamine.

[0038] Sample the product after the reaction in Step 2 and analyze it by gas chromatography. The conversion rate of benzaldehyde is measured to be 100%, and the selectivity of dibenzylamine is 96.8%.

[0039] Example 5: A method for preparing high-purity dibenzylamine, specifically as follows:

[0040] Step 1: Add 500 g of benzaldehyde, 110 g of liquid ammonia, and 650 g of benzyl chloride into a high-pressure reactor. After mixing evenly, react at 70 °C and 12 MPa for 5 h. After the reaction is completed, add 100 g of deionized water to terminate the reaction, let it stand for layering, wash the oil phase with deionized water to obtain N-benzylidene benzylamine, and distill the aqueous phase at 100 °C, cool it to obtain ammonia water that can be recycled.

[0041] Step 2: Transfer the N-benzylidene benzylamine prepared in Step 1 to another reaction kettle. At the same time, add 500 g of ethanol and 100 g of Raney nickel catalyst into the reaction kettle. After mixing evenly, introduce hydrogen gas and react at 95 °C for 1.5 h. After the reaction is completed, cool it, filter it to filter out the reusable Raney nickel catalyst. Heat the filtered filtrate to 80 °C, distill it to remove the reusable solvent ethanol, then heat it to 190 °C to distill benzylamine from the filtrate after removing the solvent, then heat it to 210 °C to distill benzyl alcohol from the filtrate after removing the solvent, and finally heat it to 300 °C for rectification, cool it to obtain high-purity dibenzylamine.

[0042] Samples of the product after the reaction in Step 2 were taken and analyzed by gas chromatography. The conversion rate of benzaldehyde was determined to be 100%, and the selectivity of dibenzylamine was 96.5%.

[0043] Example 6: A method for preparing high-purity dibenzylamine, specifically:

[0044] Step 1: Add 500 g of benzaldehyde, 110 g of liquid ammonia, and 650 g of benzyl chloride to a high-pressure reactor. After mixing evenly, react at 70 °C and 12 MPa for 5 h. After the reaction is completed, add 100 g of deionized water to terminate the reaction, let it stand for layering, wash the oil phase with deionized water to obtain N-benzylidene benzylamine, and distill the aqueous phase at 100 °C, cool it to obtain ammonia water that can be recycled.

[0045] Step 2: Transfer the N-benzylidene benzylamine prepared in Step 1 to another reaction kettle. At the same time, add 500 g of ethanol and 100 g of Raney nickel catalyst to the reaction kettle. After mixing evenly, introduce hydrogen gas and react at 95 °C for 1 h. After the reaction is completed, cool it, filter it, and filter out the reusable Raney nickel catalyst. Heat the filtered filtrate to 80 °C, distill it to remove the reusable solvent ethanol, then heat it to 190 °C, distill benzylamine from the filtrate after removing the solvent, and then heat it to 210 °C, distill benzyl alcohol from the filtrate after removing the solvent. Finally, heat it to 300 °C, rectify it, cool it to obtain high-purity dibenzylamine.

[0046] Samples of the product after the reaction in Step 2 were taken and analyzed by gas chromatography. The conversion rate of benzaldehyde was determined to be 100%, and the selectivity of dibenzylamine was 95.2%.

[0047] Example 7: A method for preparing high-purity dibenzylamine, specifically:

[0048] Step 1: Add 500 g of benzaldehyde, 110 g of liquid ammonia, and 650 g of benzyl chloride to a high-pressure reactor. After mixing evenly, react at 70 °C and 12 MPa for 5 h. After the reaction is completed, add 100 g of deionized water to terminate the reaction, let it stand for layering, wash the oil phase with deionized water to obtain N-benzylidene benzylamine, and distill the aqueous phase at 100 °C, cool it to obtain ammonia water that can be recycled.

[0049] Step 2: Transfer the N-benzylidene benzylamine prepared in Step 1 to another reactor. Meanwhile, add 500 g of ethanol and 100 g of Raney nickel catalyst into the reactor. After mixing evenly, introduce hydrogen gas and react at 110 °C for 0.5 h. After the reaction is completed, cool and filter to remove the reusable Raney nickel catalyst. Heat the filtered filtrate to 80 °C, distill to remove the reusable solvent ethanol, then heat to 190 °C to distill benzylamine from the filtrate after solvent removal, then heat to 210 °C to distill benzyl alcohol from the filtrate after solvent removal, and finally heat to 300 °C for rectification and cooling to obtain high-purity dibenzylamine.

[0050] Take a sample of the product after the reaction in Step 2 and detect and analyze it by gas chromatography. The conversion rate of benzaldehyde is determined to be 100%, and the selectivity of dibenzylamine is 95.6%.

[0051] Example 8: A method for preparing high-purity dibenzylamine, specifically as follows:

[0052] Step 1: Add 500 g of benzaldehyde, 110 g of liquid ammonia, and 650 g of benzyl chloride to a high-pressure reactor. After mixing evenly, react at 70 °C and 12 MPa for 5 h. After the reaction is completed, add 100 g of deionized water to terminate the reaction, let it stand for liquid separation, wash the oil phase with deionized water to obtain N-benzylidene benzylamine, and distill the aqueous phase at 100 °C, cool to obtain ammonia water that can be recycled.

[0053] Step 2: Transfer the N-benzylidene benzylamine prepared in Step 1 to another reactor. Meanwhile, add 500 g of ethanol and 100 g of Raney nickel catalyst into the reactor. After mixing evenly, introduce hydrogen gas and react at 95 °C for 0.5 h. After the reaction is completed, cool and filter to remove the reusable Raney nickel catalyst. Heat the filtered filtrate to 75 °C, distill to remove the reusable solvent ethanol, then heat to 185 °C to distill benzylamine from the filtrate after solvent removal, then heat to 205 °C to distill benzyl alcohol from the filtrate after solvent removal, and finally heat to 300 °C for rectification and cooling to obtain high-purity dibenzylamine.

[0054] Take a sample of the product after the reaction in Step 2 and detect and analyze it by gas chromatography. The conversion rate of benzaldehyde is determined to be 100%, and the selectivity of dibenzylamine is 92.2%.

[0055] Example 9: A method for preparing high-purity dibenzylamine, specifically as follows:

[0056] Step 1: Add 500 g of benzaldehyde, 100 g of liquid ammonia, and 650 g of benzyl chloride into a high-pressure reactor. After mixing evenly, react at 70 °C and 12 MPa for 5 h. After the reaction is completed, add 100 g of deionized water to terminate the reaction. Let it stand for layering. Wash the oil phase with deionized water to obtain N-benzylidene benzylamine. Distill the aqueous phase at 100 °C, cool it to obtain ammonia water that can be recycled.

[0057] Step 2: Transfer the N-benzylidene benzylamine prepared in Step 1 to another reaction kettle. At the same time, add 500 g of ethanol and 100 g of Raney nickel catalyst to the reaction kettle. After mixing evenly, introduce hydrogen gas and react at 110 °C for 1 h. After the reaction is completed, cool it and filter to filter out the reusable Raney nickel catalyst. Heat the filtered filtrate to 80 °C, distill it to remove the reusable solvent ethanol. Then heat it to 190 °C to distill benzylamine from the filtrate after removing the solvent. Then heat it to 210 °C to distill benzyl alcohol from the filtrate after removing the solvent. Finally, heat it to 300 °C for rectification, cool it to obtain high-purity dibenzylamine.

[0058] Sample the product after the reaction in Step 2 and detect and analyze it by gas chromatography. The conversion rate of benzaldehyde is determined to be 98.8%, and the selectivity of dibenzylamine is 96.9%.

[0059] Example 10: A preparation method of high-purity dibenzylamine, specifically as follows:

[0060] Step 1: Add 500 g of benzaldehyde, 90 g of liquid ammonia, and 650 g of benzyl chloride into a high-pressure reactor. After mixing evenly, react at 70 °C and 12 MPa for 5 h. After the reaction is completed, add 100 g of deionized water to terminate the reaction. Let it stand for layering. Wash the oil phase with deionized water to obtain N-benzylidene benzylamine. Distill the aqueous phase at 100 °C, cool it to obtain ammonia water that can be recycled.

[0061] Step 2: Transfer the N-benzylidene benzylamine prepared in Step 1 to another reaction kettle. At the same time, add 500 g of ethanol and 100 g of Raney nickel catalyst to the reaction kettle. After mixing evenly, introduce hydrogen gas and react at 110 °C for 1 h. After the reaction is completed, cool it and filter to filter out the reusable Raney nickel catalyst. Heat the filtered filtrate to 80 °C, distill it to remove the reusable solvent ethanol. Then heat it to 190 °C to distill benzylamine from the filtrate after removing the solvent. Then heat it to 210 °C to distill benzyl alcohol from the filtrate after removing the solvent. Finally, heat it to 300 °C for rectification, cool it to obtain high-purity dibenzylamine.

[0062] Sample the product after the reaction in Step 2 and detect and analyze it by gas chromatography. The conversion rate of benzaldehyde is determined to be 96.4%, and the selectivity of dibenzylamine is 93.7%.

[0063] Example 11: A preparation method of high-purity dibenzylamine, specifically as follows:

[0064] Step 1: Add 550 g of benzaldehyde, 110 g of liquid ammonia, and 650 g of benzyl chloride to a high-pressure reactor. After mixing evenly, react at 70 °C and 12 MPa for 5 h. After the reaction is completed, add 100 g of deionized water to terminate the reaction. Let it stand for layering, wash the oil phase with deionized water to obtain N-benzylidene benzylamine, and distill the aqueous phase at 100 °C, cool it to obtain ammonia water that can be recycled.

[0065] Step 2: Transfer the N-benzylidene benzylamine prepared in Step 1 to another reaction kettle. At the same time, add 500 g of ethanol and 100 g of Raney nickel catalyst to the reaction kettle. After mixing evenly, introduce hydrogen gas and react at 110 °C for 1 h. After the reaction is completed, cool it, filter it, and filter out the reusable Raney nickel catalyst. Heat the filtered filtrate to 80 °C, distill it to remove the reusable solvent ethanol, then heat it to 190 °C, distill benzylamine from the filtrate after removing the solvent, then heat it to 210 °C, distill benzyl alcohol from the filtrate after removing the solvent, and finally heat it to 300 °C, rectify it, cool it to obtain high-purity dibenzylamine.

[0066] Sample the product after the reaction in Step 2 and detect and analyze it by gas chromatography. The conversion rate of benzaldehyde is measured to be 99.2%, and the selectivity of dibenzylamine is 97.2%.

[0067] Example 12: A preparation method of high-purity dibenzylamine, specifically as follows:

[0068] Step 1: Add 600 g of benzaldehyde, 110 g of liquid ammonia, and 650 g of benzyl chloride to a high-pressure reactor. After mixing evenly, react at 70 °C and 12 MPa for 5 h, react for 4 - 6 h. After the reaction is completed, add 100 g of deionized water to terminate the reaction. Let it stand for layering, wash the oil phase with deionized water to obtain N-benzylidene benzylamine, and distill the aqueous phase at 100 °C, cool it to obtain ammonia water that can be recycled.

[0069] Step 2: Transfer the N-benzylidene benzylamine prepared in Step 1 to another reaction kettle. At the same time, add 500 g of ethanol and 100 g of Raney nickel catalyst to the reaction kettle. After mixing evenly, introduce hydrogen gas and react at 110 °C for 1 h. After the reaction is completed, cool it, filter it, and filter out the reusable Raney nickel catalyst. Heat the filtered filtrate to 80 °C, distill it to remove the reusable solvent ethanol, then heat it to 190 °C, distill benzylamine from the filtrate after removing the solvent, then heat it to 210 °C, distill benzyl alcohol from the filtrate after removing the solvent, and finally heat it to 300 °C, rectify it, cool it to obtain high-purity dibenzylamine.

[0070] Samples were taken from the product after the reaction in Step 2 and analyzed by gas chromatography. The conversion rate of benzaldehyde was determined to be 97.8%, and the selectivity of dibenzylamine was 94.9%.

[0071] Example 13: A method for preparing high-purity dibenzylamine, specifically as follows:

[0072] Step 1: Add 500 g of benzaldehyde, 110 g of liquid ammonia, and 650 g of benzyl chloride to a high-pressure reactor. After mixing evenly, react at 60 °C and 10 MPa for 6 h. After the reaction is completed, add 100 g of deionized water to terminate the reaction. Let it stand for layering. The oil phase is washed with deionized water to obtain N-benzylidene benzylamine. The aqueous phase is distilled at 100 °C, cooled, and ammonia water that can be recycled is obtained.

[0073] Step 2: Transfer the N-benzylidene benzylamine prepared in Step 1 to another reaction kettle. At the same time, add 500 g of ethanol and 100 g of Raney nickel catalyst to the reaction kettle. After mixing evenly, introduce hydrogen gas and react at 110 °C for 1 h. After the reaction is completed, cool and filter to filter out the reusable Raney nickel catalyst. Heat the filtered filtrate to 80 °C and distill to remove the reusable solvent ethanol. Then heat it to 190 °C and distill benzylamine from the filtrate after removing the solvent. Then heat it to 210 °C and distill benzyl alcohol from the filtrate after removing the solvent. Finally, heat it to 300 °C for rectification, cool, and obtain high-purity dibenzylamine.

[0074] Samples were taken from the product after the reaction in Step 2 and analyzed by gas chromatography. The conversion rate of benzaldehyde was determined to be 94.6%, and the selectivity of dibenzylamine was 91.4%.

[0075] Example 14: A method for preparing high-purity dibenzylamine, specifically as follows:

[0076] Step 1: Add 500 g of benzaldehyde, 110 g of liquid ammonia, and 650 g of benzyl chloride to a high-pressure reactor. After mixing evenly, react at 80 °C and 12 MPa for 4 h. After the reaction is completed, add 100 g of deionized water to terminate the reaction. Let it stand for layering. The oil phase is washed with deionized water to obtain N-benzylidene benzylamine. The aqueous phase is distilled at 100 °C, cooled, and ammonia water that can be recycled is obtained.

[0077] Step 2: Transfer the N-benzylidene benzylamine prepared in Step 1 to another reaction kettle. Meanwhile, add 500 g of ethanol and 100 g of Raney nickel catalyst into the reaction kettle. After mixing evenly, introduce hydrogen gas and react at 110 °C for 1 h. After the reaction is completed, cool and filter to remove the reusable Raney nickel catalyst. Heat the filtered filtrate to 80 °C and distill to remove the reusable solvent ethanol. Then heat to 190 °C and distill benzylamine from the filtrate after removing the solvent. Further heat to 210 °C and distill benzyl alcohol from the filtrate after removing the solvent. Finally, heat to 300 °C, rectify, and cool to obtain high-purity dibenzylamine.

[0078] Sample the product after the reaction in Step 2 and analyze it by gas chromatography. The conversion rate of benzaldehyde is determined to be 95.6%, and the selectivity of dibenzylamine is 93.4%.

[0079] Conversion rate of benzaldehyde (%) Selectivity of diphenylamine (%) Example 1 100％ 97.7％ Example 2 100％ 97.6％ Example 3 100％ 97.3％ Example 4 100％ 96.8％ Example 5 100％ 96.5％ Example 6 100％ 95.2％ Example 7 100％ 95.6％ Example 8 100％ 92.2％ Example 9 98.8％ 96.9％ Example 10 96.4％ 93.7％ Example 11 99.2％ 97.2％ Example 12 97.8％ 94.9％ Example 13 94.6％ 91.4％ Example 14 95.6％ 93.4％

[0080] Conclusion: After gas chromatography detection and analysis of the mixed liquid obtained after the reaction in each example, it can be seen that the preparation method of high-purity dibenzylamine proposed by the present invention can efficiently synthesize dibenzylamine by using raw materials such as benzaldehyde, liquid ammonia, and benzyl chloride. Moreover, due to the selective catalysis of the catalyst, the selectivity of the main product is strong, and almost no by-products such as benzylamine and benzyl alcohol are generated. In addition, the catalyst, solvent, etc. used in the production process of the present invention can be separated from the mixture by filtration and distillation and reused, with high atom utilization rate, meeting the theme of green and environmental protection production.

[0081] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended to include all changes falling within the meaning and scope of the equivalent elements of the claims in the present invention.

Claims

1. A method for preparing high-purity dibenzylamine, characterized in that: Specifically: Step 1: Benzaldehyde, liquid ammonia and benzyl chloride are mixed evenly, and then reacted at 60 - 80°C and 10 - 15 MPa for 4 - 6 h. After the reaction is completed, deionized water is added to terminate the reaction, and the mixture is allowed to stand for layering. The oil phase is washed with deionized water to obtain N-benzylidene benzylamine; Step 2: N-benzylidene benzylamine, ethanol and Raney nickel catalyst are mixed evenly, hydrogen is introduced, and the reaction is carried out at 90 - 120°C for 0.5 - 2 h. After the reaction is completed, it is cooled, filtered, and the filtered filtrate is distilled to remove ethanol, benzylamine and benzyl alcohol. Finally, the temperature is raised to 300 - 310°C for rectification, and then cooled to obtain high-purity dibenzylamine.

2. The preparation method of a high-purity dibenzylamine according to claim 1, characterized in that: The mass ratio of benzaldehyde, liquid ammonia and benzyl chloride is (3 - 7):(0.5 - 1.5):(4 - 8).

3. The preparation method of a high-purity dibenzylamine according to claim 1, characterized in that: The mass ratio of N-benzylidene benzylamine, ethanol and Raney nickel catalyst is (8 - 10):(4 - 8):(0.05 - 0.2).

4. A method for preparing high-purity dibenzylamine according to claim 1, characterized in that: In Step 1, the mass ratio of the deionized water used to terminate the reaction to liquid ammonia is 1:(0.8 - 1.2). The deionized water can be replaced by an equal volume of ammonia water, which is obtained by distilling the aqueous phase after standing for layering and then condensing it.

5. The preparation method of a high-purity dibenzylamine according to claim 1, characterized in that: In the Raney nickel catalyst, the nickel content is 90% - 100%. In Step 2, the Raney nickel catalyst can be filtered out and reused.

6. The preparation method of a high-purity dibenzylamine according to claim 1, characterized in that: In Step 2, the ethanol can be distilled out from the filtered filtrate and reused, and the distillation temperature is controlled at 75 - 90°C.

7. A method for preparing high-purity dibenzylamine according to claim 1, characterized in that: When removing benzylamine, the distillation temperature is controlled at 185 - 200°C.

8. The preparation method of a high-purity dibenzylamine according to claim 1, characterized in that: When removing benzyl alcohol, the distillation temperature is controlled at 205 - 220°C.