Method for manufacturing dibenzylamine

Abstract

This invention provides a method for manufacturing dibenzylamine. Benzonitrile and a reaction solvent are mixed in a high-pressure reactor, and a hydrogenation reaction is carried out under the action of a ruthenium-iron bimetallic catalyst supported on cerium oxide to obtain a crude product. After cooling and filtering the catalyst, the crude product is purified by distillation to obtain the final dibenzylamine. This method features mild reaction conditions, high atom utilization, and meets the requirements of clean and green production.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and in particular to a method for producing dibenzylamine. Background Technology

[0002] Dibenzylamine is an important intermediate in organic synthesis. It can be used to synthesize penicillin and curing agents for rubber and plastics. It is mainly used to produce highly efficient and non-toxic vulcanization accelerators tetrabenzylthiuram disulfide (TBZTD) and zinc dibenzyl dithiocarbamate (ZBEC). It can also be used to determine cobalt, iron, and cyanates.

[0003] Currently, the main methods for producing dibenzylamine are the benzyl chloride method and the benzaldehyde method. The former is a traditional process that generally uses elemental iodine as a catalyst. Under normal pressure, benzyl chloride reacts with benzylamine to produce dibenzylamine. Although this process is mature, the yield of dibenzylamine is low (producing a large amount of tribenzylamine byproduct) and the quality is poor (containing chlorine), which cannot meet the quality requirements of modern pharmaceuticals and agrochemicals. The latter is a method for preparing high-purity dibenzylamine. This method uses benzaldehyde and ammonia as raw materials, mixes them with a reaction solvent, and carries out a reduction oxidation reaction under high pressure and a catalyst to produce dibenzylamine. This process uses liquid ammonia or ammonia gas as the source of the amino group in the structure of the product dibenzylamine. Both liquid ammonia and ammonia gas are flammable, explosive, and volatile substances. They require special pressure-resistant liquefied gas tank trucks for transportation. In recent years, the rate of industrial accidents caused by the use of liquid ammonia has been very high. At the same time, accurate measurement of liquid ammonia or ammonia gas is very troublesome, and after the reaction is completed, excess liquid ammonia or ammonia gas is difficult to recover and reuse, which increases the difficulty of industrial production operations and wastewater and waste gas treatment.

[0004] In addition, dibenzylamine can also be obtained as a byproduct of the hydrogenation of benzonitrile to produce benzylamine. Usually, the selectivity of benzylamine is very high in this process, while the selectivity of dibenzylamine is very low, so it is not the mainstream method for producing dibenzylamine.

[0005] In view of this, it is necessary to design an improved method for manufacturing dibenzylamine to solve the above problems. Summary of the Invention

[0006] To address the shortcomings of the prior art, the present invention aims to provide a method for manufacturing dibenzylamine, which utilizes the highly selective hydrogenation of benzonitrile to produce dibenzylamine. This method features mild reaction conditions, high atom utilization, and meets the requirements of clean and green production.

[0007] To achieve the above objectives, the present invention provides a method for manufacturing dibenzylamine, comprising the following steps:

[0008] Step 1. In a high-pressure reactor, benzonitrile and reaction solvent are added and mixed. A catalyst is then added to carry out a hydrogenation reaction to obtain the crude reaction product.

[0009] Step 2. After cooling and filtering the catalyst, the crude product obtained in Step 1 is purified by distillation to obtain the dibenzylamine product.

[0010] As a further improvement of the present invention, in step 1, the reaction solvent is a mixture of toluene and benzylamine, and the mass ratio of toluene to benzylamine is 1:(0.1 to 0.5).

[0011] Furthermore, the mass ratio of benzonitrile to the reaction solvent is (0.1–0.5):1.

[0012] Furthermore, the mass ratio of benzonitrile to catalyst is 1:(0.01~0.1).

[0013] Furthermore, the hydrogenation reaction is carried out at a temperature of 50–120°C, a pressure of 0.6–3 MPa, and a time of 0.3–2 h.

[0014] Furthermore, the crude product of the reaction includes benzylamine and dibenzylamine.

[0015] Step 2 also includes collecting the products recovered during the distillation and purification process, wherein the recovered products are toluene and benzylamine.

[0016] As a further improvement of the present invention, the catalyst is a ruthenium-iron bimetallic catalyst supported on cerium oxide.

[0017] Furthermore, the ruthenium loading in the catalyst is 1-10 wt% of the support, and the iron loading is 1-15 wt% of the support.

[0018] Furthermore, the catalyst is prepared using a sequential impregnation method, with the specific steps as follows:

[0019] Step 1. Calcine cerium oxide at 500℃ for 1 hour;

[0020] Step 2. Prepare an aqueous solution of ruthenium nitrate and impregnate it with calcined cerium oxide. After impregnation for 12 hours, dehydrate it on a rotary evaporator. Dry the solid obtained under vacuum at 110°C for 12 hours to obtain Ru / CeO2.

[0021] Step 3. Prepare an aqueous solution of ferric nitrate and impregnate Ru / CeO2. After impregnation for 12 hours, dehydrate the solid on a rotary evaporator and dry the solid under vacuum at 110°C for 12 hours to obtain RuFe / CeO2.

[0022] Step 4. Calcine RuFe / CeO2 at 450℃ for 4 hours;

[0023] Step 5. The calcined RuFe / CeO2 was reduced with hydrogen at 200℃ for 4 hours, and then cooled to obtain a cerium oxide-supported ruthenium-iron bimetallic catalyst.

[0024] The beneficial effects of this invention are:

[0025] 1. This invention provides a method for producing dibenzylamine, which utilizes benzonitrile to produce dibenzylamine through highly selective hydrogenation under the action of a ruthenium-iron bimetallic catalyst supported on cerium oxide. This method has mild reaction conditions, high atom utilization, and meets the requirements of clean and green production.

[0026] 2. Compared with alcohol solvents conventionally used in hydrogenation reactions, the reaction solvent used in this invention has a relatively low heat of vaporization and consumes less energy when recovering the solvent, which is beneficial to industrial production.

[0027] 3. The byproduct ammonia of this invention has low solubility in toluene and benzylamine, and the ammonia concentration in the liquid phase system during the reaction is low, which is beneficial to improving the selectivity of dibenzylamine.

[0028] 4. From a reaction mechanism perspective, benzonitrile reacts with hydrogen to first form a benzylimine intermediate, which is then further hydrogenated to form benzylamine. Simultaneously, benzylamine also undergoes a condensation reaction with benzylimine to form N-benzylbenzylimine, which is then hydrogenated to form dibenzylamine. The rate of benzylimine hydrogenation to benzylamine in this process is relatively slow. To address this, benzylamine is added to the reaction solvent in this invention. A portion of the benzylamine reacts rapidly with benzylimine, thus accelerating the rate of dibenzylamine formation and shortening the reaction time. The consumed benzylamine is replenished by the hydrogenation of benzylimine to form benzylamine.

[0029] 5. Compared to using benzylamine as the solvent exclusively, this invention uses a mixture of toluene and benzylamine as the solvent, which reduces the system viscosity and prevents reaction products from adsorbing and accumulating on the catalyst surface, thus avoiding a decrease in catalyst activity. Furthermore, benzylamine itself undergoes a small amount of deamination to generate toluene during the reaction. Using a mixture of toluene and benzylamine as the solvent avoids the introduction of new substances, which is beneficial for the reaction and subsequent distillation.

[0030] 6. By adjusting the ratio of toluene to benzylamine, this invention can obtain crude reaction products with different ratios of benzylamine to dibenzylamine, thus allowing the production ratio of benzylamine and dibenzylamine to be adjusted according to market demand.

[0031] 7. The catalyst used in this invention is a ruthenium-iron bimetallic catalyst supported on cerium oxide, which has high and stable catalytic activity, weak adsorption capacity for ammonia, which is conducive to the formation of dibenzylamine, and has high selectivity for dibenzylamine. This catalyst can carry out the reaction at a lower temperature and pressure, which is in line with the energy saving and consumption reduction effect. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to specific embodiments.

[0033] Additionally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0034] This invention provides a method for manufacturing dibenzylamine, comprising the following steps:

[0035] Step 1. In a high-pressure reactor, benzonitrile and reaction solvent are added and mixed. A catalyst is then added to carry out a hydrogenation reaction to obtain the crude reaction product.

[0036] Specifically, the preferred mass ratio of benzonitrile to the reaction solvent is (0.1–0.5):1.

[0037] More preferably, the mass ratio of benzonitrile to the reaction solvent is (0.2-0.4):1.

[0038] The reaction solvent is a mixture of toluene and benzylamine in a mass ratio of 1:(0.1 to 0.5), and the crude reaction product obtained includes benzylamine and dibenzylamine.

[0039] The preferred mass ratio of benzonitrile to catalyst is 1:(0.01-0.1).

[0040] More preferably, the mass ratio of benzonitrile to catalyst is 1:(0.03 to 0.05).

[0041] The preferred temperature for the hydrogenation reaction is 50–120°C, the preferred pressure is 0.6–3 MPa, and the preferred reaction time is 0.3–2 h.

[0042] More preferably, the hydrogenation reaction temperature is 70–90°C, the reaction pressure is 1–2 MPa, and the reaction time is 0.5–1.5 h.

[0043] The catalyst is a ruthenium-iron bimetallic catalyst supported on cerium oxide.

[0044] The ruthenium loading in the catalyst is preferably 1-10 wt% of the support, and the iron loading is preferably 1-15 wt% of the support.

[0045] More preferably, the ruthenium loading in the catalyst is 1-5 wt% of the support, and the iron loading is 2.5-10 wt% of the support.

[0046] Step 2. After cooling and filtering the catalyst, the crude product obtained in Step 1 is purified by distillation to obtain the dibenzylamine product.

[0047] Specifically, step 2 also includes collecting the products recovered during the distillation and purification process, wherein the recovered products are toluene and benzylamine.

[0048] In the above steps, the catalyst is prepared using a sequential impregnation method, and the specific steps are as follows:

[0049] Step 1. Calcine cerium oxide at 500℃ for 1 hour;

[0050] Step 2. Prepare an aqueous solution of ruthenium nitrate and impregnate it with calcined cerium oxide. After impregnation for 12 hours, dehydrate it on a rotary evaporator. Dry the solid obtained under vacuum at 110°C for 12 hours to obtain Ru / CeO2.

[0051] Step 3. Prepare an aqueous solution of ferric nitrate and impregnate Ru / CeO2. After impregnation for 12 hours, dehydrate the solid on a rotary evaporator and dry the solid under vacuum at 110°C for 12 hours to obtain RuFe / CeO2.

[0052] Step 4. Calcine RuFe / CeO2 at 450℃ for 4 hours;

[0053] Step 5. The calcined RuFe / CeO2 was reduced with hydrogen at 200℃ for 4 hours, and then cooled to obtain a cerium oxide-supported ruthenium-iron bimetallic catalyst.

[0054] The method for manufacturing dibenzylamine provided by the present invention will be described below with reference to specific embodiments.

[0055] Example 1

[0056] Example 1 provides a method for manufacturing dibenzylamine, comprising the following steps:

[0057] Step 1. In a 1000 mL high-pressure reactor, add 150 g of benzonitrile, 375 g of reaction solvent (80 wt% toluene and 20 wt% benzylamine), and 7.5 g of cerium oxide-supported ruthenium-iron bimetallic catalyst (5 wt% ruthenium and 5 wt% iron) to carry out a hydrogenation reaction. The reaction temperature is 70 °C, the reaction pressure is 2.0 MPa, and the reaction time is 1 h to obtain a crude reaction product containing benzylamine and dibenzylamine.

[0058] Step 2. After cooling and filtering the catalyst, the crude product obtained in Step 1 is purified by distillation to obtain dibenzylamine. The toluene and benzylamine recovered during the distillation process can be recycled.

[0059] The reaction products were detected by gas chromatography. The conversion rate of benzonitrile was 100%, and the selectivity of dibenzylamine was 97.3%.

[0060] Example 2

[0061] Example 2 provides a method for producing dibenzylamine. The only difference from Example 1 is that the hydrogenation reaction temperature is 90°C. Other experimental parameters and conditions are the same as in Example 1 and will not be repeated here.

[0062] The reaction products were detected by gas chromatography. The conversion rate of benzonitrile was 100%, and the selectivity of dibenzylamine was 97.6%.

[0063] Example 3

[0064] Example 3 provides a method for manufacturing dibenzylamine. Compared with Example 1, the only difference is that the reaction pressure is 3.0 MPa. Other experimental parameters and conditions are the same as in Example 1, and will not be repeated here.

[0065] The reaction products were detected by gas chromatography. The conversion rate of benzonitrile was 100%, and the selectivity of dibenzylamine was 97.7%.

[0066] Example 4

[0067] Example 3 provides a method for manufacturing dibenzylamine. Compared with Example 1, the only difference is that the amount of catalyst used is 5g. Other experimental parameters and conditions are the same as in Example 1, and will not be repeated here.

[0068] The reaction products were detected by gas chromatography. The conversion rate of benzonitrile was 99.3%, and the selectivity of dibenzylamine was 96.9%.

[0069] Comparative Examples 1-2

[0070] Comparative Examples 1 and 2 each provide a method for manufacturing dibenzylamine. The only difference from Example 1 is that the reaction solvent in Comparative Example 1 is toluene, and the reaction solvent in Comparative Example 2 is benzylamine. Other experimental parameters and conditions are the same as in Example 1, and will not be repeated here.

[0071] The reaction products were detected by gas chromatography. In Comparative Example 1, the conversion rate of benzonitrile was 99.2% and the selectivity of dibenzylamine was 89.4%; in Comparative Example 2, the conversion rate of benzonitrile was 98.5% and the selectivity of dibenzylamine was 80.3%.

[0072] Comparative Example 3

[0073] Comparative Example 3 provides a method for manufacturing dibenzylamine. Compared with Example 1, the only difference is that the ruthenium loading in the catalyst is 15 wt% of the support, and the iron loading is 5 wt% of the support. Other experimental parameters and conditions are the same as in Example 1, and will not be repeated here.

[0074] The reaction products were detected by gas chromatography. The conversion rate of benzonitrile was 98.0%, and the selectivity of dibenzylamine was 87.7%.

[0075] Comparative Example 4

[0076] Comparative Example 4 provides a method for producing dibenzylamine. The only difference from Example 1 is that the catalyst used is a platinum catalyst supported on carbon. Other experimental parameters and conditions are the same as in Example 1 and will not be repeated here.

[0077] The reaction products were detected by gas chromatography. The conversion rate of benzonitrile was 97.8%, and the selectivity of dibenzylamine was 5%.

[0078] The above examples and comparative examples demonstrate that the cerium oxide-supported ruthenium-iron bimetallic catalyst provided by this invention exhibits high and stable catalytic activity, weak ammonia adsorption capacity, and is conducive to the formation of dibenzylamine. At a benzonitrile conversion rate of 100%, the selectivity for dibenzylamine is >96%. The catalyst can react at relatively low temperatures and pressures, achieving energy-saving and consumption-reducing effects. Furthermore, the use of a mixture of toluene and benzylamine as a solvent reduces system viscosity and prevents the adsorption and accumulation of reaction products on the catalyst surface, thus avoiding a decrease in catalyst activity. Therefore, this invention achieves superior technical results.

[0079] In summary, the method for producing dibenzylamine provided by this invention utilizes benzonitrile for selective hydrogenation under the action of a ruthenium-iron bimetallic catalyst supported on cerium oxide to produce dibenzylamine. This method has mild reaction conditions, high atom utilization, and meets the requirements of clean and green production.

[0080] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for manufacturing dibenzylamine, characterized in that, Includes the following steps: Step 1. In a high-pressure reactor, benzonitrile and reaction solvent are added and mixed. A catalyst is then added to carry out a hydrogenation reaction to obtain the crude reaction product. The reaction solvent is a mixture of toluene and benzylamine, wherein toluene is 80 wt% and benzylamine is 20 wt%. The catalyst is a ruthenium-iron bimetallic catalyst supported on cerium oxide, wherein the loading of ruthenium in the catalyst is 5 wt% of the support, and the loading of iron is 5 wt% of the support. The catalyst was prepared using a sequential impregnation method, and the specific steps are as follows: Step 11. Calcine cerium oxide at 500℃ for 1 hour; Step 12. Prepare an aqueous solution of ruthenium nitrate and impregnate it with calcined cerium oxide. After impregnation for 12 hours, dehydrate it on a rotary evaporator. Dry the solid obtained under vacuum at 110°C for 12 hours to obtain Ru / CeO2. Step 13. Prepare an aqueous solution of ferric nitrate and impregnate Ru / CeO2. After impregnation for 12 hours, dehydrate the solid on a rotary evaporator and dry it under vacuum at 110°C for 12 hours to obtain RuFe / CeO2. Step 14. Calcine RuFe / CeO2 at 450℃ for 4 hours; Step 15. The calcined RuFe / CeO2 was reduced with hydrogen at 200℃ for 4h, and then cooled to obtain a cerium oxide-supported ruthenium-iron bimetallic catalyst. Step 2. After cooling and filtering the catalyst, the crude product obtained in Step 1 is purified by distillation to obtain the dibenzylamine product.

2. The method for producing dibenzylamine according to claim 1, characterized in that, In step 1, the mass ratio of benzonitrile to the reaction solvent is (0.1~0.5):

1.

3. The method for producing dibenzylamine according to claim 1, characterized in that, In step 1, the mass ratio of benzonitrile to catalyst is 1:(0.01~0.1).

4. The method for producing dibenzylamine according to claim 1, characterized in that, In step 1, the temperature of the hydrogenation reaction is 50~120℃, the pressure of the reaction is 0.6~3 MPa, and the reaction time is 0.3~2 h.

5. The method for producing dibenzylamine according to claim 1, characterized in that, In step 1, the crude reaction product includes benzylamine and dibenzylamine.

6. The method for producing dibenzylamine according to claim 1, characterized in that, Step 2 also includes collecting the products recovered during the distillation and purification process; the recovered products are toluene and benzylamine.