Method for inhibiting deamination side reaction in hydrogenation process of 2, 4-diaminotoluene
By using a supported monometal ruthenium-based heterophasic catalyst and ammonia water in the 2,4-diaminotoluene hydrogenation reaction, the side reaction of deaminoglycrystallization was successfully inhibited, and the selectivity of 1-methyl-2,4-cyclohexanediamine was improved, and an efficient and green preparation process was achieved.
Patent Information
- Application Number
- CN202411757320.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-03
- Publication Date
- 2025-03-07
AI Technical Summary
During the preparation of 1-methyl-2,4-cyclohexanediamine by hydrogenation of 2,4-diaminotoluene, side reactions of deamination are prone to occur, resulting in a decrease in product selectivity.
A supported single-metal ruthenium-based heterophasic catalyst is used, and water ammonia is added to the reaction as a deamination inhibitor, and the reaction conditions such as temperature and pressure are controlled to inhibit the occurrence of deamination side reactions.
The selectivity of 1-methyl-2,4-cyclohexanediamine is significantly improved to more than 90%, reducing the incidence of side reactions, improving the atomic utilization rate of the reaction, and meeting the requirements of "green chemistry".
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Figure CN119569579A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of chemical production, in particular to a method for inhibiting a deamination side reaction in the process of preparing 1-methyl-2,4-cyclohexanediamine by hydrogenating 2,4-diaminotoluene. Background Art
[0002] 1-Methyl-2,4-cyclohexanediamine (HTDA) is an important organic chemical and fine chemical intermediate. It can be used as an epoxy resin curing agent. The product has low viscosity, long operating time, good temperature resistance and high shear strength. It can also be used in composite materials, coatings and high-grade epoxy adhesives. It can also be used in the organic synthesis of polyamides, polyimides, etc., and as an amine chain extender for polyurethane synthesis, it forms urea bonds with isocyanate groups to improve the comprehensive performance of the product. It can also be used in the organic synthesis of medicines, high-grade dyes, etc.
[0003] In industry, diaminotoluene (TDA) is commonly used to hydrogenate HTDA. Due to the high activation energy barrier of the benzene ring, high temperature and high pressure reaction conditions are usually required. As a result, the side reaction of the para-amino group removal is very likely to occur during the hydrogenation of the benzene ring, which leads to the occurrence of a deamination side reaction, and ultimately reduces the selectivity of the product.
[0004] In the prior art, regarding the method of inhibiting the TDA hydrodeamination side reaction, sodium nitrite (NaNO2) is generally used as a deamination inhibitor in China. Although sodium nitrite has certain application value as a deamination inhibitor, its toxicity and potential harm to human health cannot be ignored.
[0005] Therefore, according to the development concept of green chemistry, in order to improve the utilization rate of reactants, inhibiting the occurrence of deamination side reactions has become an important research direction for the hydrogenation of TDA to HTDA. Summary of the invention
[0006] The object of the present invention is to provide a method for inhibiting the deamination side reaction in the hydrogenation process of 2,4-diaminotoluene, so as to solve the technical problem that the deamination side reaction is easy to occur in the hydrogenation reaction of 2,4-diaminotoluene, thereby resulting in the inability to achieve high selectivity of HTDA.
[0007] In order to achieve the above object, the present invention adopts the following technical solution:
[0008] The present invention provides a method for inhibiting the deamination side reaction in the hydrogenation process of 2,4-diaminotoluene, comprising:
[0009] A supported single metal ruthenium-based heterogeneous catalyst, 2,4-diaminotoluene, a deamination inhibitor, and a reaction solvent are added to a reactor and the reactor is sealed. The air in the reactor is replaced with N2 three times at room temperature, and then low-speed stirring is started at 10-100 rpm. At the same time, H2 is introduced to replace the atmosphere in the reactor and part of the hydrogen is dissolved. Finally, H2 is introduced to a pressure of 2-5 MPa, the temperature is controlled at 150-200°C, and the stirring speed is increased to 700-1000 rpm for hydrogenation reaction for 8-15 hours to obtain the corresponding product.
[0010] Furthermore, the supported single metal ruthenium-based heterogeneous catalyst consists of a carrier and an active component, the active component is metal ruthenium, and the carrier is at least one of γ-Al2O3, activated carbon, Y-type molecular sieve, TiO2, and ZSM-5 molecular sieve.
[0011] Preferably, the content of active component Ru in the supported single metal ruthenium-based heterogeneous catalyst is 2-5 wt%.
[0012] Furthermore, the deamination inhibitor added to the reaction system is at least one of aqueous ammonia, ammonium carbonate and ammonium hydroxide.
[0013] Preferably, the deamination inhibitor added to the reaction system is aqueous ammonia with a mass concentration of 25%.
[0014] Furthermore, the reaction solvent is isopropanol.
[0015] Furthermore, the usage ratio of the supported single metal ruthenium-based heterogeneous catalyst, 2,4-diaminotoluene, deamination inhibitor, and reaction solvent is 1 g: 5 g: 5 mL: 250 mL.
[0016] Furthermore, the preparation steps of the supported metal ruthenium-based heterogeneous catalyst are:
[0017] (1) Loading metal: weigh a certain amount of carrier into a three-necked flask, add a certain proportion of distilled water and dispersant PEG-400, heat to 70-100°C in an oil bath and stir continuously, then slowly drop the metal precursor solution prepared with distilled water into the three-necked flask, and continue to stir to make it better dispersed; after the solution is added, continue to stir for a certain period of time to allow the metal cations to adsorb onto the carrier; after a period of time, add alkaline solution drop by drop, adjust the pH to 10-12, and stir for 1-2 hours; then stop heating and stirring, and centrifuge and wash the impregnated metal precursor to neutrality to obtain a metal precursor;
[0018] (2) Pretreatment of metal precursor: calcining the metal precursor in a muffle furnace under air atmosphere for 4 h;
[0019] (3) Catalyst reduction: using a fixed bed to reduce the metal precursor treated in step (2) in a hydrogen atmosphere at 250° C. to obtain the corresponding catalyst;
[0020] (4) Catalyst pretreatment: The catalyst treated in step (3) is placed in a 5 wt % LiOH solution for 12 h, washed to neutrality, and dried to obtain a supported single metal ruthenium-based heterogeneous catalyst.
[0021] Preferably, the metal precursor solution in step (1) is a RuCl3 solution.
[0022] Preferably, the alkaline solution in step (1) is a NaCO3 or (NH4)2CO3 solution with a molar concentration of 0.01-1 mol / L.
[0023] Compared with the prior art, the beneficial technical effects of the present invention are:
[0024] 1. In the process of preparing HTDA by hydrogenation of TDA catalyzed by a supported single metal ruthenium-based heterogeneous catalyst, the present invention uses a deamination inhibitor to inhibit the occurrence of a deamination side reaction, thereby achieving a 20%-30% increase in the selectivity of the target product, and a HTDA selectivity of more than 90%, with substantially no deamination side reaction occurring. This not only significantly reduces the incidence of side reactions and improves the atomic utilization of the reaction, but also has lower requirements on equipment, meeting the requirements of "green chemistry".
[0025] 2. The present invention uses ammonia water as a deamination inhibitor, which not only inhibits the occurrence of deamination side reactions, but also acts as a solvent for dispersing the catalyst. Moreover, as a deamination inhibitor, it is easy to remove, which greatly reduces the separation and purification problems in industrial production.
[0026] 3. The present invention uses the reaction of preparing HTDA by hydrogenation of TDA catalyzed by a loaded single metal ruthenium-based heterogeneous catalyst as a probe reaction, and the method designed to inhibit the deamination side reaction in the hydrogenation process of 2,4-diaminotoluene reveals the reaction mechanism of the hydrogenation side reaction, thereby achieving efficient and green preparation of the product HTDA. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figure 1 This is a transmission electron microscope (TEM) image of the 5%Ru / γ-Al2O3 catalyst used in Example 1 of the present invention;
[0028] Figure 2 X-ray diffraction XRD pattern of the 5%Ru / γ-Al2O3 catalyst used in Example 1 of the present invention;
[0029] Figure 3 This is the X-ray photoelectron XPS spectrum of the 5%Ru / γ-Al2O3 catalyst used in Example 1 of the present invention. DETAILED DESCRIPTION
[0030] The technical solution of the present invention will be described clearly and completely in conjunction with the embodiments below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0031] Example 1
[0032] Preparation of 1.5%Ru / Al2O3 Catalyst
[0033] (1) Metal loading: 3.8 g of carrier (γ-Al2O3) was weighed into a three-necked flask, 20 mL of distilled water and 7.5 mL of dispersant PEG-400 were added, and the mixture was heated at 80°C in an oil bath and stirred continuously; then 132 mL of 1.515 mg / mL RuCl3 solution was slowly added dropwise into the three-necked flask, and stirred continuously to disperse the solution better; after the addition of the solution was completed, stirring was continued for 4 h to allow the metal cations to be adsorbed onto the carrier; after a period of time, 1 mol / L Na2CO3 solution was added dropwise, the pH was adjusted to 10-12, and stirring was continued for 1 h; heating and stirring were stopped, and the impregnated metal precursor was centrifuged and washed until neutral to obtain a metal precursor;
[0034] (2) Pretreatment of metal precursor: calcining the metal precursor in a muffle furnace under air atmosphere for 4 h;
[0035] (3) Catalyst reduction: using a fixed bed, the metal precursor treated in step (1) is placed in a hydrogen atmosphere at 250° C. for 4 h to obtain the corresponding catalyst;
[0036] (4) Catalyst pretreatment: The catalyst treated in step (3) is immersed in a 5 wt% LiOH solution for 12 hours, then centrifuged and washed until neutral, and dried to obtain the corresponding single metal ruthenium-based heterogeneous catalyst of this embodiment, i.e., 1.5% Ru / Al2O3 catalyst.
[0037] Hydrogenation of TDA to HTDA over supported single-metal ruthenium-based heterogeneous catalysts
[0038] In a 450mL mechanically stirred reactor, 1g of a supported single metal ruthenium-based heterogeneous catalyst, 5g of TDA, 5mL of ammonia water, and 250mL of isopropanol were added to the reactor and the reactor was sealed. Then, the air in the reactor was replaced with N2 three times at room temperature, and low-speed stirring was started at 50rpm. At the same time, H2 was introduced to replace the atmosphere in the reactor and some hydrogen was dissolved. Finally, H2 was introduced to 3.5MPa, the temperature was set to 180°C, and the stirring speed was increased to 700rpm. Then the reaction time was set to 15h, an intermediate sampling was performed when the reaction was carried out for 8h, and a final sampling was performed again at 15h. After the reaction was completed, it was cooled to room temperature and the pressure in the reactor was released.
[0039] Example 2
[0040] The catalyst preparation steps of this embodiment are the same as those of Example 1, except that the catalyst carrier is changed to use activated carbon as the carrier, and the remaining steps are the same as those of Example 1.
[0041] In a 450mL mechanically stirred reactor, 1g of a supported single metal ruthenium-based heterogeneous catalyst, 5g of TDA, 5mL of ammonia water, and 250mL of isopropanol were added to the reactor and the reactor was sealed. Then, the air in the reactor was replaced with N2 three times at room temperature, and low-speed stirring was started at 50rpm. At the same time, H2 was introduced to replace the atmosphere in the reactor and some hydrogen was dissolved. Finally, H2 was introduced to 3.5MPa, the temperature was set to 180°C, and the stirring speed was increased to 700rpm. Then the reaction time was set to 15h, an intermediate sampling was performed when the reaction was carried out for 8h, and a final sampling was performed again at 15h. After the reaction was completed, it was cooled to room temperature and the pressure in the reactor was released.
[0042] Example 3
[0043] The catalyst preparation steps of this embodiment are the same as those of embodiment 1, except that the catalyst carrier is changed to use ZSM-5 as the carrier, and the remaining steps are the same as those of embodiment 1.
[0044] In a 450mL mechanically stirred reactor, 1g of a supported single metal ruthenium-based heterogeneous catalyst, 5g of TDA, 5mL of ammonia water, and 250mL of isopropanol were added to the reactor and the reactor was sealed. Then, the air in the reactor was replaced with N2 three times at room temperature, and low-speed stirring was started at 50rpm. At the same time, H2 was introduced to replace the atmosphere in the reactor and some hydrogen was dissolved. Finally, H2 was introduced to 3.5MPa, the temperature was set to 180°C, and the stirring speed was increased to 700rpm. Then the reaction time was set to 15h, an intermediate sampling was performed when the reaction was carried out for 8h, and a final sampling was performed again at 15h. After the reaction was completed, it was cooled to room temperature and the pressure in the reactor was released.
[0045] Example 4
[0046] The catalyst preparation steps of this embodiment are the same as those of Example 1, except that TiO2 is used as the catalyst carrier. The remaining steps are the same as those of Example 1.
[0047] In a 450mL mechanically stirred reactor, 1g of a supported single metal ruthenium-based heterogeneous catalyst, 5g of TDA, 5mL of ammonia water, and 250mL of isopropanol were added to the reactor and the reactor was sealed. Then, the air in the reactor was replaced with N2 three times at room temperature, and low-speed stirring was started at 50rpm. At the same time, H2 was introduced to replace the atmosphere in the reactor and some hydrogen was dissolved. Finally, H2 was introduced to 3.5MPa, the temperature was set to 180°C, and the stirring speed was increased to 700rpm. Then the reaction time was set to 15h, an intermediate sampling was performed when the reaction was carried out for 8h, and a final sampling was performed again at 15h. After the reaction was completed, it was cooled to room temperature and the pressure in the reactor was released.
[0048] Example 5
[0049] The catalyst preparation steps of this embodiment are the same as those of embodiment 4, except that the catalyst carrier is changed and Y-type molecular sieve is used as the carrier. The remaining steps are the same as those of embodiment 1.
[0050] In a 450mL mechanically stirred reactor, 1g of a supported single metal ruthenium-based heterogeneous catalyst, 5g of TDA, 5mL of ammonia water, and 250mL of isopropanol were added to the reactor and the reactor was sealed. Then, the air in the reactor was replaced with N2 three times at room temperature, and low-speed stirring was started at 50rpm. At the same time, H2 was introduced to replace the atmosphere in the reactor and some hydrogen was dissolved. Finally, H2 was introduced to 3.5MPa, the temperature was set to 180°C, and the stirring speed was increased to 700rpm. Then the reaction time was set to 15h, an intermediate sampling was performed when the reaction was carried out for 8h, and a final sampling was performed again at 15h. After the reaction was completed, it was cooled to room temperature and the pressure in the reactor was released.
[0051] Example 6
[0052] The catalyst of this embodiment adopts the catalyst of embodiment 1.
[0053] In a 450mL mechanically stirred reactor, 1g of a supported single metal ruthenium-based heterogeneous catalyst, 5g of TDA, 2.5mL of ammonia water, and 250mL of isopropanol were added to the reactor and the reactor was sealed. Then, the air in the reactor was replaced with N2 three times at room temperature, and low-speed stirring was started at 50rpm. At the same time, H2 was introduced to replace the atmosphere in the reactor and part of the hydrogen was dissolved. Finally, H2 was introduced to 3.5MPa, the temperature was set to 180°C, and the stirring speed was increased to 700rpm; then the reaction time was set to 15h, an intermediate sampling was performed when the reaction was carried out to 8h, and a final sampling was performed again at 15h. After the reaction was completed, it was cooled to room temperature and the pressure in the reactor was released.
[0054] Example 7
[0055] The catalyst of this embodiment adopts the catalyst of embodiment 1.
[0056] In a 450mL mechanically stirred reactor, 1g of a supported single metal ruthenium-based heterogeneous catalyst, 5g of TDA, 7.5mL of ammonia water, and 250mL of isopropanol were added to the reactor and the reactor was sealed. Then, the air in the reactor was replaced with N2 three times at room temperature, and low-speed stirring was started at 50rpm. At the same time, H2 was introduced to replace the atmosphere in the reactor and part of the hydrogen was dissolved. Finally, H2 was introduced to 3.5MPa, the temperature was set to 180°C, and the stirring speed was increased to 700rpm; then the reaction time was set to 15h, an intermediate sampling was performed when the reaction was carried out to 8h, and a final sampling was performed again at 15h. After the reaction was completed, it was cooled to room temperature and the pressure in the reactor was released.
[0057] Example 8
[0058] The catalyst of this embodiment adopts the catalyst of embodiment 1.
[0059] In a 450mL mechanically stirred reactor, 1g of a supported single metal ruthenium-based heterogeneous catalyst, 5g of TDA, 10mL of ammonia water, and 250mL of isopropanol were added to the reactor and the reactor was sealed. Then, the air in the reactor was replaced with N2 three times at room temperature, and low-speed stirring was started at 50rpm. At the same time, H2 was introduced to replace the atmosphere in the reactor and some hydrogen was dissolved. Finally, H2 was introduced to 3.5MPa, the temperature was set to 180°C, and the stirring speed was increased to 700rpm. Then the reaction time was set to 15h, an intermediate sampling was performed when the reaction was carried out for 8h, and a final sampling was performed again at 15h. After the reaction was completed, it was cooled to room temperature and the pressure in the reactor was released.
[0060] Example 9
[0061] The catalyst of this embodiment adopts the catalyst of embodiment 1.
[0062] In a 450mL mechanically stirred reactor, 1g of a supported single metal ruthenium-based heterogeneous catalyst, 5g of TDA, 12.5mL of ammonia water, and 250mL of isopropanol were added to the reactor and the reactor was sealed. Then, the air in the reactor was replaced with N2 three times at room temperature, and low-speed stirring was started at 50rpm. At the same time, H2 was introduced to replace the atmosphere in the reactor and part of the hydrogen was dissolved. Finally, H2 was introduced to 3.5MPa, the temperature was set to 180°C, and the stirring speed was increased to 700rpm; then the reaction time was set to 15h, an intermediate sampling was performed when the reaction was carried out to 8h, and a final sampling was performed again at 15h. After the reaction was completed, it was cooled to room temperature and the pressure in the reactor was released.
[0063] Example 10
[0064] The catalyst of this embodiment adopts the catalyst of embodiment 1.
[0065] In a 450mL mechanically stirred reactor, 1g of a supported single metal ruthenium-based heterogeneous catalyst, 5g of TDA, 3.2g of ammonium carbonate (the ammonia content is the same as that of 5ml of ammonia water), and 250mL of isopropanol were added to the reactor and the reactor was sealed. The air in the reactor was then replaced with N2 three times at room temperature, and low-speed stirring was started at 50rpm. At the same time, H2 was introduced to replace the atmosphere in the reactor and part of the hydrogen was dissolved. Finally, H2 was introduced to 3.5MPa, the temperature was set to 180°C, and the stirring speed was increased to 700rpm; the reaction time was then set to 15h, an intermediate sampling was performed when the reaction was carried out to 8h, and a final sampling was performed again at 15h. After the reaction was completed, it was cooled to room temperature and the pressure in the reactor was released.
[0066] Comparative Example 1
[0067] The catalyst used in this comparative example is the catalyst of Example 1.
[0068] In a 450mL mechanically stirred reactor, 1g of a supported single metal ruthenium-based heterogeneous catalyst, 5g of TDA, and 250mL of isopropanol were added to the reactor and the reactor was sealed. The air in the reactor was then replaced with N2 three times at room temperature. Low-speed stirring was then started at 50rpm, and H2 was introduced to replace the atmosphere in the reactor, and part of the hydrogen was dissolved. Finally, H2 was introduced to 3.5MPa, the temperature was set to 180°C, and the stirring speed was increased to 700rpm. The reaction time was then set to 15h, an intermediate sample was taken when the reaction was carried out for 8h, and a final sample was taken again at 15h. After the reaction was completed, the reactor was cooled to room temperature and the pressure in the reactor was released.
[0069] Comparative Example 2
[0070] The catalyst used in this comparative example is the catalyst of Example 2.
[0071] In a 450mL mechanically stirred reactor, 1g of a supported single metal ruthenium-based heterogeneous catalyst, 5g of TDA, and 250mL of isopropanol were added to the reactor and the reactor was sealed. The air in the reactor was then replaced with N2 three times at room temperature. Low-speed stirring was then started at 50rpm, and H2 was introduced to replace the atmosphere in the reactor, and part of the hydrogen was dissolved. Finally, H2 was introduced to 3.5MPa, the temperature was set to 180°C, and the stirring speed was increased to 700rpm. The reaction time was then set to 15h, an intermediate sample was taken when the reaction was carried out for 8h, and a final sample was taken again at 15h. After the reaction was completed, the reactor was cooled to room temperature and the pressure in the reactor was released.
[0072] Comparative Example 3
[0073] The catalyst used in this comparative example is the catalyst of Example 3.
[0074] In a 450mL mechanically stirred reactor, 1g of a supported single metal ruthenium-based heterogeneous catalyst, 5g of TDA, and 250mL of isopropanol were added to the reactor and the reactor was sealed. The air in the reactor was then replaced with N2 three times at room temperature. Low-speed stirring was then started at 50rpm, and H2 was introduced to replace the atmosphere in the reactor, and part of the hydrogen was dissolved. Finally, H2 was introduced to 3.5MPa, the temperature was set to 180°C, and the stirring speed was increased to 700rpm. The reaction time was then set to 15h, an intermediate sample was taken when the reaction was carried out for 8h, and a final sample was taken again at 15h. After the reaction was completed, the reactor was cooled to room temperature and the pressure in the reactor was released.
[0075] Comparative Example 4
[0076] The catalyst used in this comparative example is the catalyst of Example 4.
[0077] In a 450mL mechanically stirred reactor, 1g of a supported single metal ruthenium-based heterogeneous catalyst, 5g of TDA, and 250mL of isopropanol were added to the reactor and the reactor was sealed. The air in the reactor was then replaced with N2 three times at room temperature. Low-speed stirring was then started at 50rpm, and H2 was introduced to replace the atmosphere in the reactor, and part of the hydrogen was dissolved. Finally, H2 was introduced to 3.5MPa, the temperature was set to 180°C, and the stirring speed was increased to 700rpm. The reaction time was then set to 15h, an intermediate sample was taken when the reaction was carried out for 8h, and a final sample was taken again at 15h. After the reaction was completed, the reactor was cooled to room temperature and the pressure in the reactor was released.
[0078] Comparative Example 5
[0079] The catalyst used in this comparative example is the catalyst of Example 5.
[0080] In a 450mL mechanically stirred reactor, 1g of a supported single metal ruthenium-based heterogeneous catalyst, 5g of TDA, and 250mL of isopropanol were added to the reactor and the reactor was sealed. The air in the reactor was then replaced with N2 three times at room temperature. Low-speed stirring was then started at 50rpm, and H2 was introduced to replace the atmosphere in the reactor, and part of the hydrogen was dissolved. Finally, H2 was introduced to 3.5MPa, the temperature was set to 180°C, and the stirring speed was increased to 700rpm. The reaction time was then set to 15h, an intermediate sample was taken when the reaction was carried out for 8h, and a final sample was taken again at 15h. After the reaction was completed, the reactor was cooled to room temperature and the pressure in the reactor was released.
[0081] Test Case
[0082] The intermediate samples and final products obtained by the methods of Examples 1-6 and Comparative Examples 1-5 were analyzed and tested in a gas chromatography-mass spectrometry instrument. The evaluation results of the methods of Examples 1-6 and Comparative Examples 1-5 are shown in Table 1.
[0083] Table 1 Method evaluation results of Examples 1-6 and Comparative Examples 1-5
[0084]
[0085]
[0086] The results show that: compared with Example 1 and Comparative Example 1, when the same catalyst is used and other conditions are exactly the same, the addition of 5mL of ammonia water can increase the selectivity of the final sampled product HTDA by 16%; compared with Example 2 and Comparative Example 2, when the same catalyst is used and other conditions are exactly the same, the addition of 5mL of ammonia water can increase the selectivity of the final sampled product HTDA by 35%; compared with Example 3 and Comparative Example 3, when the same catalyst is used and other conditions are exactly the same, the addition of 5mL of ammonia water can increase the selectivity of the final sampled product HTDA by 41%; compared with Example 4 and Comparative Example 4, when the same catalyst is used and other conditions are exactly the same, the addition of 5mL of ammonia water can increase the selectivity of the final sampled product HTDA by 23%; compared with Example 5 and Comparative Example 5, when the same catalyst, i.e., 5% Ru / γ-Al2O3 catalyst, and other conditions are exactly the same, the addition of 5mL of ammonia water can increase the selectivity of the final sampled product HTDA by 23%. Compared with Examples 1, 6, 7, 8 and 9, the same catalyst was used, only the amount of ammonia water added was different, and under the condition that other conditions were exactly the same, the highest selectivity was obtained by adding 5 ml of ammonia water, and adding more ammonia water did not have a better effect. Compared with Comparative Example 1, Example 10, under the condition that the same catalyst was used and other conditions were exactly the same, the addition of 3.2 g of ammonium carbonate (the amount of ammonia was equivalent to 5 ml of ammonia water) could increase the selectivity of the final sampled product HTDA by 24%; it can be seen that in the process of preparing HTDA by hydrogenation of TDA catalyzed by a supported single metal ruthenium-based heterogeneous catalyst, the addition of ammonia water can indeed effectively reduce the occurrence of deamination side reactions and improve the selectivity of the product. Under the conditions that the supported single metal ruthenium-based heterogeneous catalyst uses different carriers (activated carbon, ZSM-5, TiO2, Y-type molecular sieve, γ-Al2O3, etc.), the addition of ammonia water can play a role in reducing the occurrence of deamination side reactions.
[0087] The study found that when the same catalyst and other conditions were the same, as the amount of ammonia water added gradually increased, the selectivity of the product gradually increased, but when the amount of ammonia water reached 5 mL, that is, reached 2% of the total mass of the system, the selectivity of the product no longer increased significantly, as shown in the test results of Examples 1 and 6, 7, 8, and 9.
[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the technical solution and conceptual invention of the present invention should be included in the protection scope of the present invention.
Claims
1. A method for inhibiting the deamination side reaction in the hydrogenation process of 2,4-diaminotoluene, characterized in that: Here are the steps: A supported single metal ruthenium-based heterogeneous catalyst, 2,4-diaminotoluene, a deamination inhibitor, and a reaction solvent are added to a reactor and the reactor is sealed. The air in the reactor is replaced with N2 three times at room temperature, and then low-speed stirring is started at 10-100 rpm. At the same time, H2 is introduced to replace the atmosphere in the reactor and partially hydrogen is dissolved. Finally, H2 is introduced to a pressure of 2-5 MPa, the temperature is controlled at 150-200°C, and the stirring speed is increased to 700-1000 rpm for hydrogenation reaction for 8-15 hours to obtain the corresponding product; The supported single metal ruthenium-based heterogeneous catalyst is composed of a carrier and an active component, the active component is metal ruthenium, and the carrier is at least one of γ-Al2O3, activated carbon, Y-type molecular sieve, TiO2, and ZSM-5 molecular sieve; The deamination inhibitor is at least one of aqueous ammonia, ammonium carbonate and ammonium hydroxide.
2. The method according to claim 1, characterized in that: The content of the active component Ru in the supported single metal ruthenium-based heterogeneous catalyst is 2-5wt%.
3. The method according to claim 1, characterized in that: The reaction solvent is isopropanol.
4. The method according to claim 1, characterized in that: The deamination inhibitor is ammonia water with a mass concentration of 25%.
5. The method according to claim 1, wherein: The amount ratio of the supported single metal ruthenium-based heterogeneous catalyst, 2,4-diaminotoluene, deamination inhibitor and reaction solvent is 1 g: 5 g: 5 mL: 250 mL.
6. The method according to claim 1, characterized in that The preparation steps of the supported metal ruthenium-based heterogeneous catalyst are: Weigh 3.8g of the carrier into a three-necked flask, add 20mL of distilled water and 7.5mL of dispersant PEG-400, heat at 80°C in an oil bath and stir continuously; then slowly drop 132mL of 1.515mg / mL RuCl3 solution into the three-necked flask, and continue stirring to disperse it better; after the solution is added, continue stirring for 4h to allow the metal cations to adsorb onto the carrier; after a period of time, drop 1mol / L Na2CO3 solution, adjust the pH to 10-12, and stir for 1h; stop heating and stirring, and centrifuge and wash the impregnated metal precursor to neutrality to obtain a metal precursor; (2) Pretreatment of metal precursor: calcining the metal precursor in a muffle furnace under air atmosphere for 4 h; (3) Catalyst reduction: using a fixed bed, the metal precursor treated in step (1) is placed in a hydrogen atmosphere at 250° C. for 4 h to obtain the corresponding catalyst; (4) Catalyst pretreatment: The catalyst treated in step (3) was immersed in a 5 wt % LiOH solution for 12 hours, then centrifuged and washed until neutral, and dried to obtain the corresponding supported single metal ruthenium-based heterogeneous catalyst.