A method for synthesizing high-yield diethyltoluene diamine

Abstract

The application discloses the technical field of organic synthesis and relates to a high-yield synthesis method of diethyltoluene diamine; the method comprises the following steps: firstly, a polyoxometalate-organic framework hybrid material is activated at medium temperature under nitrogen protection, and m-toluene diamine is pretreated by vacuum dehydration; then, the activated catalyst and the dehydrated m-toluene diamine are added into a reaction kettle, ethylene is introduced at high temperature after nitrogen replacement, and reaction is carried out; the reaction mixture is cooled and filtered, the filter cake is washed and dried, and then is activated and regenerated at medium temperature; the filtrate is subjected to rectification to collect main distillates to obtain the product. The catalyst is prepared by the following steps: reaction of phosphotungstic acid and aminopropyltrimethoxysilane, condensation with p-benzene dicarboxaldehyde, solvothermal crystallization with nickel nitrate, supercritical carbon dioxide treatment and calcination. The method has the advantages of high catalyst activity, reusability, mild reaction conditions and high yield of diethyltoluene diamine.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, specifically relating to a method for synthesizing diethyltoluene diamine with high yield. Background Technology

[0002] Diethyltoluenediamine is an important fine chemical intermediate widely used in the polyurethane industry as a high-performance chain extender. It can also be used as a curing agent for epoxy resins and a raw material for the synthesis of dyes, pesticides, and other chemical products. With the rapid development of polyurethane elastomers, composite materials, and other related industries, the market demand for high-quality, high-purity diethyltoluenediamine continues to grow, placing higher demands on the yield, selectivity, and environmental friendliness of its synthesis process.

[0003] Currently, the mainstream industrial method for preparing diethyltoluenediamine is to introduce an ethyl group through alkylation using m-toluenediamine as a raw material. Existing technologies employ a variety of alkylating agents and catalyst systems to achieve this conversion. Earlier processes often used Lewis acids such as aluminum trichloride and boron trifluoride as catalysts. While these methods achieve the reaction, they suffer from problems such as high catalyst consumption, strong corrosiveness, complex post-reaction treatment, and the generation of large amounts of aluminum- or boron-containing waste, which are environmentally unfriendly. To improve this situation, researchers have developed various catalytic systems. For example, using triethylaluminum pre-complexed with m-toluenediamine to generate a catalyst before alkylation can achieve high yields, but still faces challenges such as high catalyst costs and demanding operating conditions. In recent years, there have also been reports of using ionic liquids or specific molecular sieves as catalysts, aiming to simplify separation processes or improve the selectivity of target products. However, ionic liquid synthesis is costly and recovery is complex, while the stability of molecular sieve catalysts during long-term operation and their catalytic efficiency under relatively mild conditions still need improvement. Furthermore, regarding the selection of alkylating agents, although there are reports of using other reagents such as halogenated ethanes, ethylene, as an inexpensive, readily available, and atom-economical olefin feedstock, has always been the ideal choice for industrialization. The key lies in developing a catalytic system that can efficiently activate ethylene and guide its selective alkylation.

[0004] In summary, while existing technologies for synthesizing diethyltoluene diamine have made some progress, most suffer from limitations in catalytic efficiency, product yield, separation and purification difficulty, and environmental compatibility. Therefore, designing a novel catalytic material that can efficiently and selectively catalyze the alkylation reaction of m-toluene diamine with ethylene under relatively mild reaction conditions, while simultaneously enabling easy separation and stable recycling of the catalyst, thereby significantly improving the yield of the target product and reducing production costs and environmental impact, remains a pressing technical challenge for those skilled in the art. Developing a novel catalyst system that combines high activity, high selectivity, good stability, and easy recyclability is of great significance for promoting the green and efficient synthesis of diethyltoluene diamine. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for synthesizing diethyltoluene diamine with a high yield.

[0006] A first aspect of the present invention provides a method for synthesizing high-yield diethyltoluenediamine, comprising the following steps:

[0007] S1. By weight, under nitrogen protection, 2.5-10.0 parts of polyoxometalate cluster-organic framework hybrid material are heated to 120-150℃ and activated at a constant temperature; cooled to room temperature to obtain activated polyoxometalate cluster-organic framework hybrid material; 490-510 parts of m-toluenediamine are vacuum dehydrated at 80-90℃ to obtain pre-dehydrated m-toluenediamine;

[0008] S2. In a nitrogen-filled glove box, the activated polymetallic oxygen cluster-organic framework hybrid material is added to the reactor, followed by the addition of pre-dehydrated m-toluenediamine; the reactor is sealed, nitrogen is introduced into the reactor, and then the pressure is released to atmospheric pressure; the mixture is stirred and heated to 160-180°C; ethylene is introduced to continue the reaction.

[0009] S3. After the reaction is complete, cool to 70-80℃; discharge the reaction mixture through the bottom discharge valve; filter the reaction mixture using a pressure filtration device under nitrogen pressure of 0.2-0.3MPa; obtain filter cake and filtrate; wash the filter cake with isopropanol to obtain washing liquid and washed filter cake; combine the washing liquid and filtrate to obtain a mixture; vacuum dry the washed filter cake and activate it with nitrogen at 120-150℃.

[0010] S4. Transfer the mixture obtained in step S3 to a distillation column and distill it under vacuum conditions; collect the main fraction at the top of the column.

[0011] In this invention, the high-yield synthesis of diethyltoluenediamine is based on the catalytic alkylation reaction of ethylene with p-m-toluenediamine. The activated polyoxometalate-organic framework hybrid material serves as a heterogeneous catalyst, with its active center comprising acidic sites of the polyoxometalate cluster and coordinated unsaturated sites of the metal ions. At the start of the reaction, m-toluenediamine molecules adsorb onto the catalyst surface. The lone pair electrons on the amino group interact with the acidic sites of the catalyst, reducing the electron cloud density on the nitrogen atom and enhancing nucleophilicity. Simultaneously, ethylene molecules undergo coordination activation at the metal ion sites, polarizing the electron cloud of the carbon-carbon double bond. The activated ethylene molecules undergo a nucleophilic addition reaction with the activated amino group to form an ethylation intermediate. This intermediate undergoes proton transfer and elimination reactions to generate a monoethylated product. The monoethylated product can further undergo a second alkylation reaction with ethylene to generate the target product, diethyltoluenediamine. Controlling the reaction temperature is crucial. Too low a temperature leads to a slow reaction rate and insufficient conversion, while too high a temperature can damage the catalyst structure and increase side reactions, such as excessive alkylation to form triethylated products, amine decomposition products, and polymer byproducts. Maintaining ethylene pressure ensures a sufficient ethylene concentration in the reaction system, shifting the reaction equilibrium towards the product. After the reaction, the catalyst is separated from the reaction liquid by filtration, and can be recycled multiple times after washing and activation. The product mixture is separated by vacuum distillation, and the target fraction is collected based on the boiling point differences of the components. Throughout the synthetic route, the structural integrity of the catalyst, precise control of reaction conditions, and timely separation of products are key factors for achieving high yields. The unique structure of the polyoxometalate-organic framework hybrid material combines the acid catalytic performance of polyoxometalates with the shape-selective catalytic performance of metal-organic frameworks, thus achieving highly selective ethylation of m-toluenediamine.

[0012] According to a preferred embodiment of the present invention, in step S1, the vacuum dehydration treatment time is 2-4 hours.

[0013] According to a preferred embodiment of the present invention, in step S2, the rate of ethylene introduction is 50-100 mL / min; the reaction time is 6-8 h.

[0014] According to a preferred embodiment of the present invention, in step S3, the nitrogen activation time at 120-150°C is 1-2 hours.

[0015] According to a preferred embodiment of the present invention, in step S4, the absolute pressure under vacuum conditions is 1-2 kPa.

[0016] According to a preferred embodiment of the present invention, the preparation steps of the polymetallic oxygen cluster-organic framework hybrid material include:

[0017] A1. Under nitrogen protection, add 150-250 parts by weight of anhydrous acetonitrile and 14.4-18.0 parts by weight of phosphotungstic acid to a three-necked flask and stir. Add 2.0-2.5 parts by weight of 3-aminopropyltrimethoxysilane and 2.0-3.0 parts by weight of deionized water. After the addition is complete, reflux the mixture at 78-82℃ to obtain a reaction solution. Cool the reaction solution to room temperature and rotary evaporate to obtain a crude product. Wash the crude product with 25-35 parts by weight of anhydrous diethyl ether, centrifuge the washing liquid, and collect the solid. Dry the solid under vacuum to obtain an amino-functionalized polyoxometalate precursor.

[0018] A2. Dissolve 4.5-5.5 parts of the amino-functionalized polyoxometalate cluster precursor prepared in step A1 in 140-160 parts of anhydrous N,N-dimethylformamide and cool to 0-5℃. While stirring, add 48-52 parts of an N,N-dimethylformamide solution containing 0.60-0.75 parts of terephthalaldehyde. After the addition is complete, heat to room temperature and continue stirring to obtain a reaction solution. Distill the reaction solution under reduced pressure at 80-90℃, and then add 180-220 parts of anhydrous diethyl ether. Filter to obtain a filter cake. Wash the filter cake alternately with anhydrous ethanol and anhydrous diethyl ether, and dry under vacuum to obtain the polyoxometalate cluster-organic hybrid oligomer.

[0019] A3. Disperse 4.5-5.5 parts of the polyoxometalate cluster-organic hybrid oligomer obtained in step A2 in a mixed solvent of 70-80 parts anhydrous ethanol and 23-27 parts deionized water, and sonicate to obtain a dispersion; transfer the dispersion to a reaction vessel, add 0.65-0.80 parts of nickel nitrate hexahydrate; seal the reaction vessel, and heat to 140-150℃ for solvothermal crystallization reaction; after the reaction is completed, allow it to cool naturally to room temperature; remove the product from the reaction vessel, centrifuge to obtain a solid precipitate; wash the solid precipitate sequentially with N,N-dimethylformamide, deionized water and anhydrous ethanol; vacuum dry to obtain crude polyoxometalate cluster-organic framework hybrid material;

[0020] A4. Place the crude polymetallic oxygen cluster-organic framework hybrid material obtained in step A3 into a supercritical fluid reactor, introduce carbon dioxide, and heat to 38-42℃ for treatment; after treatment, release carbon dioxide to atmospheric pressure and take out the sample; place the sample in a tube furnace and calcine it at 120-150℃ under nitrogen atmosphere protection.

[0021] In this invention, the preparation of polyoxometalate cluster-organic framework hybrid materials involves multiple chemical reactions and self-assembly processes. First, phosphotungstic acid and aminopropyltrimethoxysilane undergo a grafting reaction in anhydrous acetonitrile solvent. The methoxy group in the silane coupling agent hydrolyzes under the influence of water to generate silanol groups. Subsequently, the silanol groups undergo a condensation reaction with oxygen atoms on the surface of phosphotungstic acid, forming stable siloxane-tungsten bonds, thereby introducing amino functional groups onto the surface of the polyoxometalate cluster, yielding an amino-functionalized polyoxometalate cluster precursor. In this process, the amount of water is crucial; sufficient water ensures complete hydrolysis of the silane, but excessive water leads to excessive condensation of the silanol, forming a siloxane polymer. Second, the amino-functionalized polyoxometalate cluster precursor undergoes a Schiff base condensation reaction with terephthalaldehyde in dimethylformamide solvent. The amino and aldehyde groups dehydrate to form imine bonds, linking the polyoxometalate cluster units into an oligomer structure through organic ligands. This reaction is a reversible equilibrium reaction. Removing the water generated during the reaction by vacuum distillation shifts the equilibrium towards the product direction, increasing the degree of condensation. Next, the polyoxometalate-organic hybrid oligomer and nickel nitrate undergo a solvothermal crystallization reaction in an ethanol-water mixed solvent. Nickel ions coordinate with the coordination sites in the oligomer, while the polyoxometalate units are bridged by metal ions to form a three-dimensional framework structure. The solvothermal conditions provide sufficient energy to allow the structural units to arrange themselves in an orderly manner, forming a crystalline material with regular channels. Finally, supercritical carbon dioxide treatment removes solvent molecules from the channels, and mild calcination further activates the material without destroying the organic ligand structure, yielding a catalytically active polyoxometalate-organic framework hybrid material. Throughout the preparation process, the reaction conditions of each step are interrelated; the quality of the product in the previous step directly affects the reaction effect of subsequent steps.

[0022] According to a preferred embodiment of the present invention, in step A1, the reflux reaction time at 78-82°C is 24-30 hours.

[0023] According to a preferred embodiment of the present invention, in step A2, the stirring reaction is continued for 12-18 hours.

[0024] According to a preferred embodiment of the present invention, in step A3, the time for the solvothermal crystallization reaction at 140-150°C is 24-36 hours.

[0025] According to a preferred embodiment of the present invention, in step A4, the calcination time is 2-4 hours after the temperature is raised to 120-150°C.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The high-yield synthesis method of diethyltoluenediamine provided by this invention has the primary technical effect of significantly improving the yield and selectivity of the target product. The core of this method lies in the use of a carefully designed polyoxometalate cluster-organic framework hybrid material as a catalyst. This catalyst is prepared through a multi-step process. First, phosphotungstic acid is reacted with an aminosilane coupling agent to introduce active functional groups. Then, it forms a Schiff base structure with terephthalaldehyde. Subsequently, nickel ions are introduced for coordination-directed solvothermal crystallization. Finally, the mixture is treated with supercritical carbon dioxide and gently calcined to construct a hybrid material with a unique two-dimensional layered structure and a high specific surface area. This structure provides abundant acidic active sites and confined space. In the alkylation reaction of m-toluenediamine with ethylene, it can effectively activate ethylene molecules and guide their selective substitution at the ortho-amino position, thereby significantly reducing the formation of polyalkylation byproducts. Experimental results show that the single-pass conversion rate of m-toluenediamine can reach a high level using this method, the selectivity of the target product diethyltoluenediamine is excellent, and the total yield is significantly higher than that reported using traditional catalysts or processes, which fully meets the market demand for high-quality products.

[0028] (2) The method of this invention exhibits excellent catalyst stability and recyclability, significantly reducing production costs. During catalyst preparation, precise control of each reaction step, particularly setting the final calcination activation temperature within a suitable medium-temperature range, effectively stabilizes the framework structure of the hybrid material while avoiding the destruction of organic ligands and Schiff base bonds by high temperatures, ensuring the firm anchoring of the catalytic active center during the reaction. After the synthesis reaction, efficient separation of the catalyst and reaction mixture can be achieved through simple hot filtration and washing. The recovered catalyst, after vacuum drying and medium-temperature activation under a nitrogen atmosphere, exhibits good recovery of its catalytic activity and selectivity. Experiments confirm that even after repeated use, the yield of the target product remains high, with minimal decrease in activity. This excellent reusability not only significantly reduces the consumption of fresh catalyst but also simplifies the post-processing steps, which is of great significance for reducing raw material costs and waste treatment costs in industrial production.

[0029] (3) The synthesis method of this invention embodies the concepts of green chemistry and sustainable development. Compared with the traditional process using Lewis acids such as aluminum trichloride, this invention avoids the use of a large amount of highly corrosive homogeneous catalysts that produce difficult-to-treat waste residues after processing. The polymetallic oxygen cluster-organic framework hybrid material used is a heterogeneous catalyst, which is easy to separate from the reaction system and can be recycled multiple times, reducing waste generation at the source. Ethylene, the raw material for the reaction, is a cheap, readily available, and atom-economical basic chemical raw material, and its use complies with the principle of atom economy. The entire synthesis process, from catalyst preparation to target product synthesis and product separation and purification, has a compact step design and relatively mild operating conditions. The solvents and reagents used can be recycled and reused through conventional industrial methods. In summary, this invention provides a new technical solution with high efficiency, high selectivity, low cost, and environmental friendliness, and has good prospects for industrial application. It is of positive significance for promoting the upgrading of diethyltoluene diamine production technology. Detailed Implementation

[0030] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0031] Example 1

[0032] This embodiment provides a method for synthesizing high-yield diethyltoluenediamine, comprising the following steps:

[0033] Step S1: Under nitrogen protection, with a nitrogen flow rate of 50 mL / min, weigh 5.0 g of the polymetallic oxygen cluster-organic framework hybrid material and place it in a ceramic boat. Place the ceramic boat in a tube furnace and heat it to 135℃. Activate at this temperature for 2 hours at a heating rate of 5℃ / min. After activation, turn off the heating power and cool it to room temperature under nitrogen protection for 2 hours to obtain the activated polymetallic oxygen cluster-organic framework hybrid material. Weigh 500 g of m-toluenediamine and place it in a 500 mL round-bottom flask. Connect the round-bottom flask to a rotary evaporator and dehydrate it under vacuum at 85℃ and 5 kPa for 3 hours. After dehydration, obtain pre-dehydrated m-toluenediamine with a moisture content of less than 0.01%.

[0034] Step S2: In a nitrogen-filled glove box with oxygen and water content below 1 ppm, the activated polymetallic oxygen cluster-organic framework hybrid material is added to a 1 L high-pressure reactor. Then, pre-dehydrated m-toluenediamine is added. The reactor is sealed, and nitrogen is introduced into the reactor at a pressure of 0.5 MPa. The pressure is then released to atmospheric pressure and repeated three times. The reactor is stirred, and a magnetic stirrer is turned on at a speed of 500 r / min. The reactor is removed from the glove box and connected to an ethylene gas source. The electric heating mantle is turned on and the temperature is raised to 170°C. The temperature is maintained for 30 min. Ethylene is introduced, and the ethylene introduction rate is controlled at 75 mL / min. The ethylene pressure is maintained at 1.0 MPa, and the reaction is continued for 7 h. During the reaction, the stirring speed is maintained at 500 r / min.

[0035] Step S3: After the reaction is complete, turn off the heating power and cool down to 75℃ for 1 hour. Discharge the reaction mixture through the bottom discharge valve and transfer it to a pressure filtration device. Filter the reaction mixture under 0.25 MPa nitrogen pressure using a 0.22 μm polytetrafluoroethylene filter membrane to obtain a filter cake and filtrate. Wash the filter cake three times with 100 g of isopropanol to obtain a washing liquid and a washed filter cake. Combine the washing liquid and filtrate to obtain a mixture. Transfer the washed filter cake to a vacuum drying oven and vacuum dry it at 135℃ and 1 kPa for 2 hours. Then, under a nitrogen atmosphere with a nitrogen flow rate of 50 mL / min, activate it at 135℃ for 1.5 hours to obtain a polymetallic oxygen cluster-organic framework hybrid material.

[0036] Step S4: Transfer the mixture to a 2L distillation column with 20 theoretical plates. Distillation is carried out under vacuum conditions with an absolute vacuum pressure of 1.5kPa, a heating power of 2kW, and a reflux ratio of 3:1. The main fraction with a top temperature of 180-185℃ is collected over a period of 4 hours to obtain diethyltoluene diamine.

[0037] Preparation of polyoxometalate cluster-organic framework hybrid materials:

[0038] Step A1: Under nitrogen protection, add 200g of anhydrous acetonitrile and 16.0g of phosphotungstic acid to a 500mL three-necked flask. Turn on the magnetic stirrer and set the stirring speed to 300r / min. Stir and mix thoroughly for 30min. Using a constant pressure dropping funnel, add 2.2g of 3-aminopropyltrimethoxysilane dropwise over 30min. Simultaneously, add 2.5g of deionized water dropwise over 30min. After the addition is complete, remove the nitrogen protection, install the reflux condenser, turn on the oil bath heating, and reflux the reaction at 80℃ for 27h, keeping the mixture stirred during reflux. The reaction mixture was rotated at 300 r / min to obtain a deep yellow reaction solution. The reaction solution was cooled to room temperature for 2 h. The solvent was removed by rotary evaporation at 45 °C and 5 kPa for 3 h to obtain a pale yellow crude product. The crude product was transferred to a centrifuge tube, 30 g of anhydrous diethyl ether was added, and the mixture was ultrasonically dispersed for 10 min. The washing liquid was centrifuged at 8000 r / min for 10 min, the supernatant was discarded, and the solid was collected. The solid was transferred to a vacuum drying oven and vacuum dried at 60 °C and 1 kPa for 12 h to obtain an amino-functionalized polyoxometalate cluster precursor.

[0039] Step A2: Weigh 5.0 g of the amino-functionalized polyoxometalate precursor and place it in a 250 mL three-necked flask. Add 150 g of anhydrous N,N-dimethylformamide and turn on the magnetic stirrer at 300 rpm to completely dissolve the precursor. Transfer the solution to an ice-water bath and cool to 3°C. Keep the solution at this temperature for 30 min. Weigh 0.68 g of terephthalaldehyde and dissolve it in 50 g of anhydrous N,N-dimethylformamide to prepare an N,N-dimethylformamide solution. Using a constant pressure dropping funnel, add 50 g of the N,N-dimethylformamide solution containing 0.68 g of terephthalaldehyde dropwise to the reaction system over a period of 60 min. During the addition process, the temperature was maintained at 3℃. After the addition was completed, the ice-water bath was removed, and the temperature was raised to room temperature (25℃). The reaction was continued with stirring for 15 hours at a stirring speed of 300 r / min to obtain a brown reaction solution. The reaction solution was transferred to a rotary evaporator and the solvent was removed by vacuum distillation at 85℃ and 5 kPa for 4 hours. 200 g of anhydrous diethyl ether was added, and a precipitate appeared. The precipitate was filtered using a Buchner funnel to obtain a filter cake. The filter cake was washed three times with 50 g of anhydrous ethanol and then three times with 50 g of anhydrous diethyl ether. The washed filter cake was transferred to a vacuum drying oven and dried under vacuum at 60℃ and 1 kPa for 12 hours to obtain a polymetallic oxygen cluster-organic hybrid oligomer.

[0040] Step A3: Weigh 5.0 g of the polymetallic oxy-organic hybrid oligomer and place it in a 100 mL beaker. Add a mixed solvent of 75 g of anhydrous ethanol and 25 g of deionized water. Sonicate the mixture for 30 min using an ultrasonic cell disruptor at a power of 200 W to obtain a uniform dispersion. Transfer the dispersion to a 100 mL stainless steel reactor with a filling density of 70%. Weigh 0.72 g of nickel nitrate hexahydrate and add it to the reactor. Seal the reactor and place it in an oven. Heat the reactor to 145 °C for a solvothermal crystallization reaction for 30 h at a heating rate of 5 °C. After the reaction was completed, the oven power was turned off and the mixture was allowed to cool naturally to room temperature for 12 hours. The product in the reactor was then removed and transferred to a centrifuge tube. The product was centrifuged at 8000 r / min for 10 minutes to obtain a solid precipitate. The solid precipitate was washed three times with 50 g of N,N-dimethylformamide, then three times with 50 g of anhydrous ethanol, and finally three times with 50 g of anhydrous diethyl ether. The washed solid was then transferred to a vacuum drying oven and dried under vacuum at 60 °C and 1 kPa for 12 hours to obtain a crude product of a polymetallic oxygen cluster-organic framework hybrid material.

[0041] Step A4: Weigh the crude polyoxometalate cluster-organic framework hybrid material and place it in a supercritical fluid reactor. Introduce carbon dioxide at a flow rate of 50 mL / min and heat to 40 °C for 2 hours while maintaining the pressure at 10 MPa. After treatment, slowly release the carbon dioxide to atmospheric pressure over a period of 30 minutes. Remove the sample and place it in a tube furnace. Under a nitrogen atmosphere, heat to 135 °C for 3 hours at a flow rate of 100 mL / min. After calcination, allow it to cool naturally to room temperature to obtain the polyoxometalate cluster-organic framework hybrid material.

[0042] Example 2

[0043] The difference between this embodiment and Embodiment 1 lies in the preparation of the polymetallic oxygen cluster-organic framework hybrid material:

[0044] Step A1: Under nitrogen protection, add 150g of anhydrous acetonitrile and 14.4g of phosphotungstic acid to a three-necked flask, stir and mix well, add 2.0g of 3-aminopropyltrimethoxysilane and 2.0g of deionized water dropwise. After the addition is complete, heat to 78℃ and reflux for 24h to obtain a reaction solution. Cool the reaction solution to room temperature and remove the solvent by rotary evaporation to obtain a crude product. Wash the crude product with 25g of anhydrous diethyl ether, centrifuge the washing liquid, collect the solid, and vacuum dry the solid to obtain an amino-functionalized polyoxometalate precursor.

[0045] Step A2: Dissolve 4.5g of amino-functionalized polyoxometalate precursor in 140g of anhydrous N,N-dimethylformamide, cool to 0℃, and add 48g of N,N-dimethylformamide solution containing 0.60g of terephthalaldehyde dropwise while stirring. After the addition is complete, heat to room temperature and continue stirring for 12h to obtain a reaction solution. Distill the reaction solution under reduced pressure at 80℃, then add 180g of anhydrous diethyl ether, filter, and obtain a filter cake. Wash the filter cake alternately with anhydrous ethanol and anhydrous diethyl ether, and dry under vacuum to obtain polyoxometalate-organic hybrid oligomer.

[0046] Step A3: Disperse 4.5g of the polyoxometalate cluster-organic hybrid oligomer in a mixed solvent of 70g anhydrous ethanol and 23g deionized water, and sonicate for 30min to obtain a dispersion. Transfer the dispersion to a reactor, add 0.65g of nickel nitrate hexahydrate, and fill the reactor to 60%. Seal the reactor and heat it to 140℃ for solvothermal crystallization reaction for 24h. After the reaction is completed, allow it to cool naturally to room temperature. Remove the product from the reactor, centrifuge to obtain a solid precipitate, and wash the solid precipitate sequentially with N,N-dimethylformamide, anhydrous ethanol, and anhydrous diethyl ether. Vacuum dry to obtain crude polyoxometalate cluster-organic framework hybrid material.

[0047] Step A4: Place the crude polyoxometalate cluster-organic framework hybrid material in a supercritical fluid reactor, introduce carbon dioxide, heat to 38°C for 2 hours, release carbon dioxide to atmospheric pressure after treatment, remove the sample, place the sample in a tube furnace, and calcine at 120°C for 2 hours under nitrogen atmosphere protection to obtain the polyoxometalate cluster-organic framework hybrid material.

[0048] Synthesis of high-yield diethyltoluenediamine:

[0049] Step S1: Under nitrogen protection, 2.5g of polyoxometalate cluster-organic framework hybrid material was heated to 120℃ and activated at a constant temperature for 1h, then cooled to room temperature to obtain activated polyoxometalate cluster-organic framework hybrid material. 490g of m-toluenediamine was vacuum dehydrated at 80℃ for 2h to obtain pre-dehydrated m-toluenediamine.

[0050] Step S2: In a nitrogen-filled glove box, the activated polymetallic oxygen cluster-organic framework hybrid material was added to the reactor, followed by the addition of pre-dehydrated m-toluenediamine. The reactor was sealed, and nitrogen gas was introduced into the reactor at a pressure of 0.3 MPa. The pressure was then released to atmospheric pressure, and this process was repeated three times. The reactor was stirred, and a magnetic stirrer was turned on at a speed of 400 r / min. The reactor was then removed from the glove box and connected to an ethylene gas source. The electric heating mantle was turned on, and the temperature was raised to 160°C. The temperature was maintained for 30 min, and ethylene was introduced at a rate of 50 mL / min. The ethylene pressure was maintained at 0.8 MPa, and the reaction was continued for 6 h. During the reaction, the stirring speed was kept at 400 r / min.

[0051] Step S3: After the reaction is completed, the temperature is lowered to 70°C, and the reaction mixture is discharged through the bottom discharge valve. The reaction mixture is filtered using a pressure filtration device under a nitrogen pressure of 0.2 MPa to obtain a filter cake and a filtrate. The filter cake is washed with isopropanol to obtain a washing liquid and a washed filter cake. The washing liquid and the filtrate are combined to obtain a mixture. The washed filter cake is vacuum dried and activated with nitrogen at 120°C for 1 hour.

[0052] Step S4: Transfer the mixture to a distillation column and distill it under vacuum conditions. The absolute vacuum pressure is 1 kPa. Collect the main fraction with a top temperature of 175-180℃ to obtain diethyltoluene diamine product.

[0053] Example 3

[0054] The difference between this embodiment and Embodiment 1 lies in the preparation of the polymetallic oxygen cluster-organic framework hybrid material:

[0055] Step A1: Under nitrogen protection, add 250g of anhydrous acetonitrile and 18.0g of phosphotungstic acid to a three-necked flask, stir and mix well, add 2.5g of 3-aminopropyltrimethoxysilane and 3.0g of deionized water dropwise. After the addition is complete, heat to 82℃ and reflux for 30h to obtain a reaction solution. Cool the reaction solution to room temperature and remove the solvent by rotary evaporation to obtain a crude product. Wash the crude product with 35g of anhydrous diethyl ether, centrifuge the washing liquid, collect the solid, and vacuum dry the solid to obtain an amino-functionalized polyoxometalate precursor.

[0056] Step A2: Dissolve 5.5g of amino-functionalized polyoxometalate precursor in 160g of anhydrous N,N-dimethylformamide, cool to 5°C, and add 52g of N,N-dimethylformamide solution containing 0.75g of terephthalaldehyde dropwise while stirring. After the addition is complete, heat to room temperature and continue stirring for 18h to obtain a reaction solution. Distill the reaction solution under reduced pressure at 90°C, then add 220g of anhydrous diethyl ether, filter, and obtain a filter cake. Wash the filter cake alternately with anhydrous ethanol and anhydrous diethyl ether, and dry under vacuum to obtain polyoxometalate-organic hybrid oligomer.

[0057] Step A3: Disperse 5.5g of the polyoxometalate cluster-organic hybrid oligomer in a mixed solvent of 80g anhydrous ethanol and 27g deionized water, and sonicate for 30min to obtain a dispersion. Transfer the dispersion to a reaction vessel, add 0.80g of nickel nitrate hexahydrate, and fill the reaction vessel to 80%. Seal the reaction vessel and heat it to 150℃ for solvothermal crystallization reaction for 36h. After the reaction is completed, allow it to cool naturally to room temperature. Remove the product from the reaction vessel, centrifuge to obtain a solid precipitate, and wash the solid precipitate sequentially with N,N-dimethylformamide, anhydrous ethanol, and anhydrous diethyl ether. Vacuum dry to obtain crude polyoxometalate cluster-organic framework hybrid material.

[0058] Step A4: Place the crude polyoxometalate cluster-organic framework hybrid material in a supercritical fluid reactor, introduce carbon dioxide, heat to 42°C and treat for 2 hours. After treatment, release carbon dioxide to atmospheric pressure, take out the sample, place the sample in a tube furnace, and calcine at 150°C for 4 hours under nitrogen atmosphere protection to obtain the polyoxometalate cluster-organic framework hybrid material.

[0059] Synthesis of high-yield diethyltoluenediamine:

[0060] Step S1: Under nitrogen protection, 10.0 g of polyoxometalate cluster-organic framework hybrid material was heated to 150℃ and activated at a constant temperature for 2 h, then cooled to room temperature to obtain activated polyoxometalate cluster-organic framework hybrid material. 510 g of m-toluenediamine was vacuum dehydrated at 90℃ for 4 h to obtain pre-dehydrated m-toluenediamine.

[0061] Step S2: In a nitrogen-filled glove box, the activated polymetallic oxygen cluster-organic framework hybrid material was added to the reactor, followed by the addition of pre-dehydrated m-toluenediamine. The reactor was sealed, and nitrogen gas was introduced into the reactor at a pressure of 0.6 MPa. The pressure was then released to atmospheric pressure, and this process was repeated three times. The reactor was stirred, and a magnetic stirrer was turned on at a speed of 600 r / min. The reactor was then removed from the glove box and connected to an ethylene gas source. The electric heating mantle was turned on, and the temperature was raised to 180°C and maintained for 30 min. Ethylene was introduced, and the ethylene introduction rate was controlled at 100 mL / min. The ethylene pressure was maintained at 1.2 MPa, and the reaction was continued for 8 h. During the reaction, the stirring speed was maintained at 600 r / min.

[0062] Step S3: After the reaction is completed, the temperature is lowered to 80°C, and the reaction mixture is discharged through the bottom discharge valve. The reaction mixture is filtered using a pressure filtration device under a nitrogen pressure of 0.3 MPa to obtain a filter cake and a filtrate. The filter cake is washed with isopropanol to obtain a washing liquid and a washed filter cake. The washing liquid and the filtrate are combined to obtain a mixture. The washed filter cake is vacuum dried and activated with nitrogen at 150°C for 2 hours.

[0063] Step S4: Transfer the mixture to a distillation column and distill it under vacuum conditions. The absolute vacuum pressure is 2 kPa. Collect the main fraction with a top temperature of 185-190℃ to obtain diethyltoluene diamine product.

[0064] Comparative Example 1

[0065] The difference between this comparative example and Example 1 is that in step A1, 3-aminopropyltrimethoxysilane and deionized water are not added for amino functionalization, and the phosphotungstic acid precursor is obtained directly. In step A2, 5.0 g of the phosphotungstic acid precursor is dissolved in 150 g of anhydrous N,N-dimethylformamide for subsequent reaction. The other steps are the same as in Example 1, and the diethyltoluenediamine product is finally obtained.

[0066] Comparative Example 2

[0067] The difference between this comparative example and Example 1 is that in step A2, an N,N-dimethylformamide solution containing terephthalaldehyde is not added for Schiff base linkage. The other steps are the same as in Example 1, and the diethyltoluene diamine product is finally obtained.

[0068] Comparative Example 3

[0069] The difference between this comparative example and Example 1 is that nickel nitrate hexahydrate is not added in step A3 for metal node coordination. The other steps are the same as in Example 1, and the diethyltoluene diamine product is finally obtained.

[0070] In accordance with national and industry standard testing specifications, a series of standardized tests were conducted on the synthesis methods of high-yield diethyltoluene diamine described in Examples 1-3 and Comparative Examples 1-3.

[0071] Catalyst specific surface area test: The specific surface area of ​​the polymetallic oxygen cluster-organic framework hybrid material was determined by nitrogen adsorption-desorption instrument. Before the test, the sample was degassed in vacuum at 120℃ for 12h with a degassing pressure of less than 1Pa and a test temperature of 77K. The specific surface area was calculated using the BET method, with the unit being m² / g. The test was repeated 3 times and the average value was taken.

[0072] Product yield test: The catalytic reaction was carried out in a fixed-bed reactor at a reaction temperature of 170℃, an ethylene pressure of 1.0MPa, an ethylene flow rate of 75mL / min, a mass of 500g of m-toluenediamine, a mass of 5.0g of catalyst, and a reaction time of 7h. After the reaction was completed, the product was collected and the actual product mass was weighed. The yield was calculated using the formula (actual product mass / theoretical product mass) × 100%, in units of 100%.

[0073] Product purity testing: Product purity was analyzed using gas chromatography. The chromatographic column was a DB-5 capillary column, 30 m long, 0.25 mm inner diameter, and 0.25 μm film thickness. The injection port temperature was 280 °C, and the detector temperature was 300 °C. The column temperature program was as follows: initial temperature 80 °C, hold for 2 min, increase to 280 °C at 10 °C / min, hold for 10 min. Nitrogen was used as the carrier gas at a flow rate of 1.0 mL / min and a split ratio of 50:1. Purity was calculated using the peak area normalization method.

[0074] Catalyst cycle stability test: The catalyst after reaction was washed three times with 100g of isopropanol, dried under vacuum for 12h, activated with nitrogen at 135℃ for 1.5h and reused. The product yield of the 10th cycle was tested. The test conditions were the same as those for the product yield test.

[0075] Catalyst selectivity test: The ratio of target product to byproduct is analyzed by gas chromatography. The selectivity calculation formula is (moles of target product / moles of reactant converted) × 100%, unit.

[0076] Triethylation byproduct testing: The content of triethylation byproducts in the reaction solution was detected by gas chromatography-mass spectrometry. The ionization method was electron impact ionization with an electron energy of 70 eV, an ion source temperature of 230℃, a quadrupole temperature of 150℃, and a scan range of 30 amu to 500 amu. Quantification was performed using the external standard method.

[0077] The performance test data above are shown in Table 1.

[0078] Table 1 Performance Test Results

[0079]

[0080] As can be seen from the above, Examples 1-3 effectively solve the key technical problems in the existing diethyltoluene diamine synthesis technology compared with Comparative Examples 1-3. The specific surface area of ​​Examples 1-3 is 820-880 m² / g, which is 2.1-2.5 times that of Comparative Examples 1-3 (350-420 m² / g). This indicates that the present invention significantly increases the number of active sites of the catalyst through the synergistic effect of amino functionalization, Schiff base linkage and metal node coordination, and solves the technical problem of insufficient activity caused by low specific surface area of ​​existing catalysts.

[0081] The product yields of Examples 1-3 were 89.3-92.5%, which is more than 20% higher than the 65.8-71.5% of Comparative Examples 1-3. This indicates that the catalyst of the present invention has higher activity and solves the technical problem of low yield and high production cost caused by existing synthesis methods.

[0082] The purity of the products in Examples 1-3 was 97.5-98.2%, which was higher than that of Comparative Examples 1-3 (91.2-93.4%). This indicates that the catalyst of the present invention has fewer side reactions and solves the technical problem of low product purity leading to high subsequent purification costs in existing methods.

[0083] The catalysts in Examples 1-3 maintained a yield of 87.2-90.5% after 10 cycles, while the yields in Comparative Examples 1-3 decreased to 50.5-58.6% after 10 cycles. This indicates that the catalyst of the present invention has excellent cycle stability and solves the technical problem of short service life caused by easy deactivation of existing catalysts.

[0084] The catalyst selectivity of Examples 1-3 was 94.2-95.5%, which was much higher than that of Comparative Examples 1-3 (68.8-73.5%), indicating that the present invention achieved precise control of the reaction pathway and solved the technical problem of poor selectivity in existing methods.

[0085] The triethylation byproduct content in Examples 1-3 was only 1.1-1.5%, far lower than the 5.2-6.5% in Comparative Examples 1-3, indicating that the present invention effectively suppressed the excessive ethylation side reaction and solved the technical problem of difficult separation caused by excessive byproducts in existing methods.

[0086] In summary, this invention, through the special structural design of polyoxometalate cluster-organic framework hybrid materials, comprehensively solves many technical problems in the existing diethyltoluene diamine synthesis technology, such as low yield, poor purity, poor selectivity, poor catalyst stability, and numerous by-products, demonstrating significant progress.

Claims

1. A method for synthesizing diethyltoluenediamine in high yield, characterized in that, Includes the following steps: S1. By weight, under nitrogen protection, 2.5-10.0 parts of polyoxometalate cluster-organic framework hybrid material are heated to 120-150℃ and activated at a constant temperature; cooled to room temperature to obtain activated polyoxometalate cluster-organic framework hybrid material; 490-510 parts of m-toluenediamine are vacuum dehydrated at 80-90℃ to obtain pre-dehydrated m-toluenediamine; S2. In a nitrogen-filled glove box, the activated polymetallic oxygen cluster-organic framework hybrid material is added to the reactor, followed by the addition of pre-dehydrated m-toluenediamine; the reactor is sealed, nitrogen is introduced into the reactor, and then the pressure is released to atmospheric pressure; the mixture is stirred and heated to 160-180°C; ethylene is introduced to continue the reaction. S3. After the reaction is complete, cool down to 70-80℃; release the reaction mixture through the bottom discharge valve; use a pressure filtration device to filter the reaction mixture under nitrogen pressure of 0.2-0.3MPa; obtain filter cake and filtrate; wash the filter cake with isopropanol to obtain washing liquid and washed filter cake. The washing liquid and filtrate were combined to obtain a mixture; the washed filter cake was vacuum dried and activated with nitrogen at 120-150℃. S4. Transfer the mixture obtained in step S3 to a distillation column and perform distillation under vacuum conditions; Collect the main distillate from the top of the column.

2. The method for synthesizing high-yield diethyltoluenediamine according to claim 1, characterized in that, In step S1, the vacuum dehydration process takes 2-4 hours.

3. The method for synthesizing high-yield diethyltoluenediamine according to claim 1, characterized in that, In step S2, the rate of ethylene introduction is 50-100 mL / min; the reaction time is 6-8 h.

4. The method for synthesizing high-yield diethyltoluenediamine according to claim 1, characterized in that, In step S3, the nitrogen activation time at 120-150℃ is 1-2 hours.

5. The method for synthesizing high-yield diethyltoluenediamine according to claim 1, characterized in that, In step S4, the absolute pressure under vacuum conditions is 1-2 kPa.

6. The method for synthesizing high-yield diethyltoluenediamine according to any one of claims 1-5, characterized in that, The preparation steps of the polymetallic oxygen cluster-organic framework hybrid material include: A1. Under nitrogen protection, add 150-250 parts by weight of anhydrous acetonitrile and 14.4-18.0 parts by weight of phosphotungstic acid to a three-necked flask and stir. Add 2.0-2.5 parts by weight of 3-aminopropyltrimethoxysilane and 2.0-3.0 parts by weight of deionized water. After the addition is complete, reflux the mixture at 78-82℃ to obtain a reaction solution. Cool the reaction solution to room temperature and rotary evaporate to obtain a crude product. Wash the crude product with 25-35 parts by weight of anhydrous diethyl ether, centrifuge the washing liquid, and collect the solid. Dry the solid under vacuum to obtain an amino-functionalized polyoxometalate precursor. A2. Dissolve 4.5-5.5 parts of the amino-functionalized polyoxometalate cluster precursor prepared in step A1 in 140-160 parts of anhydrous N,N-dimethylformamide and cool to 0-5℃. While stirring, add 48-52 parts of an N,N-dimethylformamide solution containing 0.60-0.75 parts of terephthalaldehyde. After the addition is complete, heat to room temperature and continue stirring to obtain a reaction solution. Distill the reaction solution under reduced pressure at 80-90℃, and then add 180-220 parts of anhydrous diethyl ether. Filter to obtain a filter cake. Wash the filter cake alternately with anhydrous ethanol and anhydrous diethyl ether, and dry under vacuum to obtain the polyoxometalate cluster-organic hybrid oligomer. A3. Disperse 4.5-5.5 parts of the polyoxometalate cluster-organic hybrid oligomer obtained in step A2 in a mixed solvent of 70-80 parts anhydrous ethanol and 23-27 parts deionized water, and sonicate to obtain a dispersion; transfer the dispersion to a reaction vessel, add 0.65-0.80 parts of nickel nitrate hexahydrate; seal the reaction vessel, and heat to 140-150℃ for solvothermal crystallization reaction; after the reaction is completed, allow it to cool naturally to room temperature; remove the product from the reaction vessel, centrifuge to obtain a solid precipitate; wash the solid precipitate sequentially with N,N-dimethylformamide, deionized water and anhydrous ethanol; vacuum dry to obtain crude polyoxometalate cluster-organic framework hybrid material; A4. Place the crude polymetallic oxygen cluster-organic framework hybrid material obtained in step A3 into a supercritical fluid reactor, introduce carbon dioxide, and heat to 38-42℃ for treatment; after treatment, release carbon dioxide to atmospheric pressure and take out the sample; place the sample in a tube furnace and calcine it at 120-150℃ under nitrogen atmosphere protection.

7. The method for synthesizing high-yield diethyltoluenediamine according to claim 6, characterized in that, In step A1, the reflux reaction time at 78-82℃ is 24-30 hours.

8. The method for synthesizing high-yield diethyltoluenediamine according to claim 6, characterized in that, In step A2, the stirring reaction continues for 12-18 hours.

9. The method for synthesizing high-yield diethyltoluenediamine according to claim 6, characterized in that, In step A3, the time for the solvothermal crystallization reaction at 140-150℃ is 24-36 hours.

10. The method for synthesizing high-yield diethyltoluenediamine according to claim 6, characterized in that, In step A4, the temperature is raised to 120-150℃ and the calcination time is 2-4 hours.

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