Catalysts, their preparation methods, and their application in the synthesis of 2,3,6-triamino-5-nitropyridine

Abstract

This invention discloses a catalyst, its preparation method, and its application in the synthesis of 2,3,6-triamino-5-nitropyridine. The catalyst of this invention comprises a support and an active component Pd supported on the support; the active component Pd includes oxidized Pd and reduced Pd elements; the mass content of oxidized Pd in ​​the active component Pd is 50%-80%. By controlling the oxidation state of the active component Pd, the electronic structure of the catalyst can be altered, thereby improving its catalytic activity. When synthesizing 2,3,6-triamino-5-nitropyridine using the catalyst of this invention, a 100% hydrogenation conversion of 2,6-diamino-3,5-dinitropyridine can be achieved, with a selectivity of over 95% and a yield of over 85%. Therefore, the catalyst of this invention exhibits high catalytic activity and operates under mild and efficient reaction conditions.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis, and more specifically, to catalysts, their preparation methods, and their application in the synthesis of 2,3,6-triamino-5-nitropyridine. Background Technology

[0002] Poly(2,5-dihydroxy-1,4-phenylenepyridinium diimidazole) (PIPD) is a high-performance synthetic fiber obtained by the polymerization reaction of 2,3,5,6-tetraaminopyridine (TAP) and 2,5-dihydroxyterephthalic acid. PIPD fibers possess unparalleled advantages in tensile and compressive strength among all high-performance fibers. Furthermore, the abundance of polar functional groups (-OH) in its molecular chain gives PIPD fibers excellent surface wettability and composite adhesion, compensating for the shortcomings of PBO fibers in these aspects.

[0003] However, 2,3,5,6-tetraaminopyridine (TAP) has poor stability and needs to be prepared as a hydrochloride salt. Furthermore, it is still susceptible to oxidation during polymerization. 2,3,6-Triamino-5-nitropyridine (TANP), an intermediate product in the hydrogenation synthesis of TAP from 2,6-diamino-3,5-dinitropyridine (DADNP), can be used as a precursor for the reductive synthesis of 2,3,5,6-tetraaminopyridine (TAP).

[0004] Existing literature discloses the synthesis and application of 2,3,6-triamino-5-nitropyridine (JOURNAL OF ZHEJIANG UNIVERSITY OF TECHNOLOGY Vol.41 No.5 Oct.2013), which uses sodium polysulfide and hydrazine hydrate to reduce 2,6-diamino-3,5-dinitropyridine to obtain 2,3,6-triamino-5-nitropyridine. However, this method is relatively complex, with harsh reaction conditions, and the synthesized substance contains trace amounts of sulfur impurities.

[0005] Therefore, there is a need to develop a new, mild and efficient method for the synthesis of 2,3,6-triamino-5-nitropyridine. Summary of the Invention

[0006] To address the problems in existing technologies, this invention proposes a catalyst, its preparation method, and its application in the synthesis of 2,3,6-triamino-5-nitropyridine. This invention first prepares a novel catalyst. By controlling the oxidation state of the active component Pd, the electronic structure of the catalyst can be altered, thereby improving its catalytic activity. The catalyst of this invention, used to catalyze the synthesis of the polymerization intermediate 2,3,6-triamino-5-nitropyridine, achieves a 100% hydrogenation conversion of 2,6-diamino-3,5-dinitropyridine, with a selectivity exceeding 95% and a yield exceeding 85%. Therefore, the catalyst of this invention allows the reaction to stop well on the mononitro hydrogenation product, exhibiting high catalytic activity and mild, efficient reaction conditions.

[0007] One object of the present invention is to provide a catalyst comprising a support and an active component Pd supported on the support;

[0008] The active component Pd includes oxidized Pd and reduced Pd elements; the mass content of oxidized Pd in ​​the active component Pd is 50%-80%.

[0009] In this invention, the active component Pd refers to the active component Pd element.

[0010] In the catalyst described in this invention, preferably,

[0011] Based on a total weight of 100 wt% for the active component Pd and the support in the catalyst, the content of the active component Pd is 3-5 wt%; and / or,

[0012] The average particle size of the active component Pd is 2-3 nm; and / or,

[0013] The carrier is selected from carbon materials;

[0014] Preferably, the carrier is selected from at least one of carbon nanotubes and activated carbon.

[0015] In this invention, the interaction between Pd nanoparticles and carbon materials is strong, and Pd nanoparticles can be well loaded onto carbon materials.

[0016] A second objective of this invention is to provide a method for preparing a catalyst, comprising the following steps:

[0017] The precursor solution of active component Pd was mixed and impregnated with the support, aged, dried, reduced, passivated and oxidized to obtain the catalyst.

[0018] Preferably, the catalyst is prepared for any one of the purposes of this invention.

[0019] Compared with existing conventional catalyst preparation methods, the catalyst preparation steps of this invention also include passivation and oxidation steps, which increase the proportion of oxidized states on the catalyst surface and improve the selectivity of the catalyst.

[0020] In the method for preparing the catalyst described in this invention, preferably,

[0021] Based on a total weight of 100wt% for the Pd element in the precursor solution of the active component Pd and the added support, the amount of Pd element added in the precursor solution of the active component Pd is 3wt%-5wt%; preferably, the content of Pd element in the precursor solution of the active component Pd is 0.5wt%-0.8wt%.

[0022] In the method for preparing the catalyst described in this invention, preferably,

[0023] Under stirring conditions, the precursor solution of the active component Pd is added dropwise to the carrier for mixing and impregnation, preferably for 1-3 hours.

[0024] In this invention, the carrier can be heat-treated with acid before use, preferably with nitric acid at 80-100°C for 8-12 hours.

[0025] In this invention, the preferred impregnation method is equal-volume impregnation, and the impregnation temperature is room temperature.

[0026] In the method for preparing the catalyst described in this invention, preferably,

[0027] The aging time is 12-16 hours; and / or,

[0028] The aging temperature is room temperature; and / or,

[0029] The drying temperature is 100-120℃; and / or,

[0030] The drying time is 8-12 hours.

[0031] In the method for preparing the catalyst described in this invention, preferably,

[0032] The reduction temperature is 160–250°C; and / or,

[0033] The reduction time is 2–4 hours; and / or,

[0034] The reducing atmosphere is hydrogen.

[0035] In the method for preparing the catalyst described in this invention, preferably,

[0036] Passivation is performed using a mixture of oxygen and a protective gas;

[0037] Preferably, the protective gas is selected from at least one of nitrogen and argon;

[0038] More preferably,

[0039] The volume content of oxygen in the gas mixture is 1%-2%; and / or,

[0040] The passivation temperature is room temperature; and / or,

[0041] The passivation time is 1-2 hours.

[0042] In the method for preparing the catalyst described in this invention, preferably,

[0043] Oxidation is achieved by introducing air;

[0044] Preferably,

[0045] The oxidation temperature is 20-50℃; and / or,

[0046] The oxidation time is 8-12 hours.

[0047] In the catalyst preparation method described in this invention, most preferably,

[0048] Dissolve the chloropalladic acid solution in water to prepare a Pd precursor solution of a certain concentration;

[0049] The precursor solution described in step (1) is slowly added to a certain amount of commercial carbon nanotubes while stirring. After the addition is complete, the solution is aged and dried to obtain an unreduced catalyst.

[0050] The catalyst described in step (2) is reduced, passivated by passing through a low concentration of oxygen, and then further oxidized by passing through air to obtain the catalyst.

[0051] A third objective of this invention is to provide the application of a catalyst as described in any one of the objectives of this invention or a catalyst prepared by the method described in any one of the objectives of this invention in the synthesis of 2,3,6-triamino-5-nitropyridine.

[0052] A fourth objective of this invention is to provide a method for synthesizing 2,3,6-triamino-5-nitropyridine, comprising the following steps:

[0053] 2,6-Diamino-3,5-dinitropyridine and a catalyst were mixed in an organic solvent, and hydrogen was introduced to carry out a hydrogenation reaction. After post-treatment, 2,3,6-triamino-5-nitropyridine was obtained.

[0054] The catalyst is selected from the catalyst described in any one of the objectives of this invention or the catalyst prepared by the method described in any one of the objectives of this invention.

[0055] The structural formula of 2,3,6-triamino-5-nitropyridine in this invention is shown in (Ⅰ):

[0056]

[0057] In the method for synthesizing 2,3,6-triamino-5-nitropyridine according to the present invention, preferably,

[0058] The organic solvent is selected from alcohol solvents, preferably at least one of methanol and ethanol; and / or,

[0059] The mass ratio of the organic solvent to 2,6-diamino-3,5-dinitropyridine is 1:8-15; and / or,

[0060] The mass ratio of catalyst to 2,6-diamino-3,5-dinitropyridine is ≥1:5; preferably 1:5-7; and / or,

[0061] The hydrogen pressure is maintained at 0.5-1.5 MPa.

[0062] In the method for synthesizing 2,3,6-triamino-5-nitropyridine according to the present invention, preferably,

[0063] The temperature for hydrogenation reactions is 35-55℃; and / or,

[0064] The hydrogenation reaction takes 6-10 hours.

[0065] In the method for synthesizing 2,3,6-triamino-5-nitropyridine according to the present invention, preferably,

[0066] After the hydrogenation reaction, a solid-liquid separation is performed to obtain a solid mixture. Then, a solvent (such as DMSO) is added to dissolve the hydrogenation reaction product in the solid mixture. A second solid-liquid separation is performed to obtain a separated liquid. Ice water is added to the separated liquid to cause 2,3,6-triamino-5-nitropyridine to crystallize out.

[0067] In the method for synthesizing 2,3,6-triamino-5-nitropyridine described in this invention, most preferably,

[0068] The process includes the following steps: using methanol as a solvent, the raw material 2,6-diamino-3,5-dinitropyridine and the corresponding catalyst are placed in a reaction vessel, and hydrogen gas is introduced to carry out a hydrogenation reaction. The products after the reaction are a solid and a catalyst powder. The solid product and the catalyst powder are placed in a DMSO solution, the product dissolves, and then ice water is added to the DMSO solution to obtain the 2,3,6-triamino-5-nitropyridine product.

[0069] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In the following, various technical solutions can, in principle, be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0070] Compared with the prior art, the present invention has at least the following advantages:

[0071] The present invention provides a simple, high-yield, and mild reaction method for synthesizing 2,3,6-triamino-5-nitropyridine.

[0072] The inventors discovered that by controlling the oxidation state of the catalyst, its electronic structure can be altered, thereby halting the reaction at the mononitro hydrogenation product stage. Compared to existing reduction methods using sodium polysulfide and hydrazine hydrate, the catalytic reduction method of this invention is simpler and operates under milder reaction conditions. Attached Figure Description

[0073] Figure 1 The 1H NMR spectrum of the product obtained in Example 1;

[0074] Figure 2 The carbon NMR spectrum of the product obtained in Example 1;

[0075] Figure 3 The image shows the XPS plot of the catalyst obtained in Example 1. Detailed Implementation

[0076] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0077] It should also be noted that the various specific technical features described in the following embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the various possible combinations will not be described separately in this invention.

[0078] Furthermore, various embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention. The resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0079] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0080] Example 1

[0081] Catalyst preparation:

[0082] Prepare 60g of a chloropalladic acid-water solution with a palladium content of 0.5wt% as the impregnation solution;

[0083] Take 10g of commercial carbon nanotube support, slowly add the impregnation solution to the support while stirring, and after 3 hours of dropwise addition, age for 12 hours, dry at 120 degrees Celsius for 12 hours, reduce at 200 degrees Celsius for 2 hours, then passivate by passing through 1% O2 / Ar; and then deeply oxidize by passing through air at 25 degrees Celsius for 12 hours to obtain the catalyst.

[0084] from Figure 3 As can be seen from the above, the oxidation state of the catalyst prepared in Example 1 of the present invention is different from that of ordinary Pd catalyst. The proportion of oxidized Pd element in the catalyst of the present invention is greater than that of reduced Pd element.

[0085] Synthesis of 2,3,6-triamino-5-nitropyridine:

[0086] 5g of 2,6-diamino-3,5-dinitropyridine (dadnp), 1g of the above catalyst, and 50mL of methanol were added to a 100mL reactor. The hydrogen pressure was 1.0MPa, the reaction temperature was 40°C, and the reaction was carried out for 8 hours. The solid and reaction liquid were separated, and 2,3,6-triamino-5-nitropyridine (TANP) was dissolved by adding DMSO. The catalyst was obtained by filtration. The DMSO solution of TANP was added to ice water, and TANP crystallized out with a yield of 85.0%. Liquid chromatography showed no impurity peaks, and the purity was above 99.5%. The NMR spectrum of the obtained 2,3,6-triamino-5-nitropyridine product is shown below. Figure 1 and Figure 2 As shown.

[0087] The catalyst prepared by the above method was used to catalyze the synthesis of the polymerization intermediate 2,3,6-triamino-5-nitropyridine. The specific hydrogenation conversion of 2,6-diamino-3,5-dinitro and the selectivity of 2,3,6-triamino-5-nitropyridine are shown in Table 1.

[0088] Example 2

[0089] Catalyst preparation:

[0090] Prepare 60g of a chloropalladic acid-water solution with a palladium content of 0.65wt% as the impregnation solution;

[0091] Take 10g of commercial carbon nanotube support, slowly add the impregnation solution to the support while stirring, and after 3 hours of dropwise addition, age for 12 hours, dry at 120 degrees Celsius for 12 hours, reduce at 200 degrees Celsius for 2 hours, then passivate by passing through 1% O2 / Ar; and then deeply oxidize by passing through air at 25 degrees Celsius for 12 hours to obtain the catalyst.

[0092] Synthesis of 2,3,6-triamino-5-nitropyridine:

[0093] The catalyst obtained by the above method was used to synthesize 2,3,6-triamino-5-nitropyridine, using the same synthesis and post-treatment methods as in Example 1. The yield of 2,3,6-triamino-5-nitropyridine was 82.5%, and the purity was 99.5%. The specific hydrogenation conversion of 2,6-diamino-3,5-dinitropyridine and the selectivity of 2,3,6-triamino-5-nitropyridine are shown in Table 1.

[0094] Example 3

[0095] Catalyst preparation:

[0096] Prepare 60g of a chloropalladic acid-water solution with a palladium content of 0.8wt% as the impregnation solution;

[0097] Take 10g of commercial carbon nanotube support, slowly add the impregnation solution to the support while stirring, and after 3 hours of dropwise addition, age for 12 hours, dry at 120 degrees Celsius for 12 hours, reduce at 200 degrees Celsius for 2 hours, then passivate by passing through 1% O2 / Ar; and then deeply oxidize by passing through air at 25 degrees Celsius for 12 hours to obtain the catalyst.

[0098] Synthesis of 2,3,6-triamino-5-nitropyridine:

[0099] The catalyst obtained by the above method was used to synthesize 2,3,6-triamino-5-nitropyridine using the same synthesis and post-treatment methods as in Example 1. The yield of 2,3,6-triamino-5-nitropyridine was 78.7%, and the purity was 98.0%. The specific hydrogenation conversion of 2,6-diamino-3,5-dinitropyridine and the selectivity of 2,3,6-triamino-5-nitropyridine are shown in Table 1.

[0100] Example 4

[0101] Catalyst preparation:

[0102] Prepare 60g of a chloropalladic acid-water solution with a palladium content of 0.5wt% as the impregnation solution;

[0103] Take 10g of commercial carbon nanotube support, slowly add the impregnation solution to the support while stirring, and after 3 hours of dropwise addition, age for 12 hours, dry at 120 degrees Celsius for 12 hours, reduce at 200 degrees Celsius for 2 hours, then passivate by passing through 1% O2 / Ar; and then deeply oxidize by passing through air at 25 degrees Celsius for 8 hours to obtain the catalyst.

[0104] Synthesis of 2,3,6-triamino-5-nitropyridine:

[0105] The catalyst obtained by the above method was used to synthesize 2,3,6-triamino-5-nitropyridine, using the same synthesis and post-treatment methods as in Example 1. The yield of 2,3,6-triamino-5-nitropyridine was 84.5%, and the purity was 99.5%. The specific hydrogenation conversion of 2,6-diamino-3,5-dinitropyridine and the selectivity of 2,3,6-triamino-5-nitropyridine are shown in Table 1.

[0106] Example 5

[0107] Catalyst preparation:

[0108] Prepare 60g of a chloropalladic acid-water solution with a palladium content of 0.5wt% as the impregnation solution;

[0109] Take 10g of commercial carbon nanotube support, slowly add the impregnation solution to the support while stirring, and after 3 hours of dropwise addition, age for 12 hours, dry at 120 degrees Celsius for 12 hours, reduce at 160 degrees Celsius for 2 hours, then passivate by passing through 1% O2 / Ar; and then deeply oxidize by passing through air at 25 degrees Celsius for 12 hours to obtain the catalyst.

[0110] Synthesis of 2,3,6-triamino-5-nitropyridine:

[0111] The catalyst obtained by the above method was used to synthesize 2,3,6-triamino-5-nitropyridine using the same synthesis and post-treatment methods as in Example 1. The yield of 2,3,6-triamino-5-nitropyridine was 84.8%, and the purity was 99.5%. The specific hydrogenation conversion of 2,6-diamino-3,5-dinitropyridine and the selectivity of 2,3,6-triamino-5-nitropyridine are shown in Table 1.

[0112] Example 6

[0113] Catalyst preparation:

[0114] Prepare 60g of a chloropalladic acid-water solution with a palladium content of 0.5wt% as the impregnation solution;

[0115] Take 10g of commercial carbon nanotube support, slowly add the impregnation solution to the support while stirring, and after 3 hours of dropwise addition, age for 12 hours, dry at 120 degrees Celsius for 12 hours, reduce at 250 degrees Celsius for 2 hours, then passivate by passing through 1% O2 / Ar; and then deeply oxidize by passing through air at 25 degrees Celsius for 12 hours to obtain the catalyst.

[0116] Synthesis of 2,3,6-triamino-5-nitropyridine:

[0117] The catalyst obtained by the above method was used to synthesize 2,3,6-triamino-5-nitropyridine using the same synthesis and post-treatment methods as in Example 1. The yield of 2,3,6-triamino-5-nitropyridine was 83.5%, and the purity was 99.5%. The specific hydrogenation conversion of 2,6-diamino-3,5-dinitropyridine and the selectivity of 2,3,6-triamino-5-nitropyridine are shown in Table 1.

[0118] Example 7

[0119] Catalyst preparation:

[0120] Prepare 60g of a chloropalladic acid-water solution with a palladium content of 0.5wt% as the impregnation solution;

[0121] Take 10g of commercial carbon nanotube support, slowly add the impregnation solution to the support while stirring, and after 3 hours of dropwise addition, age for 12 hours, dry at 120 degrees Celsius for 12 hours, reduce at 200 degrees Celsius for 2 hours, then passivate by passing through 1% O2 / Ar; and then deeply oxidize by passing through air at 45 degrees Celsius for 12 hours to obtain the catalyst.

[0122] Synthesis of 2,3,6-triamino-5-nitropyridine:

[0123] The catalyst obtained by the above method was used to synthesize 2,3,6-triamino-5-nitropyridine. The reaction time was 8 h, and the rest of the synthesis and post-treatment methods were the same as in Example 1. The yield of 2,3,6-triamino-5-nitropyridine was 75.0%, and the purity was 83%. The specific hydrogenation conversion of 2,6-diamino-3,5-dinitropyridine and the selectivity of 2,3,6-triamino-5-nitropyridine are shown in Table 1.

[0124] Example 8

[0125] Catalyst preparation:

[0126] Prepare 60g of a chloropalladic acid-water solution with a palladium content of 0.5wt% as the impregnation solution;

[0127] Take 10g of commercial carbon nanotube support, slowly add the impregnation solution to the support while stirring, and after 3 hours of dropwise addition, age for 12 hours, dry at 120 degrees Celsius for 12 hours, reduce at 200 degrees Celsius for 2 hours, then passivate by passing through 1% O2 / Ar; and then deeply oxidize by passing through air at 45 degrees Celsius for 12 hours to obtain the catalyst.

[0128] Synthesis of 2,3,6-triamino-5-nitropyridine:

[0129] The catalyst obtained by the above method was used to synthesize 2,3,6-triamino-5-nitropyridine. The reaction time was 12 h, and the rest of the synthesis and post-treatment methods were the same as in Example 1. The yield of 2,3,6-triamino-5-nitropyridine was 84.0%, and the purity was 99.0%. The specific hydrogenation conversion of 2,6-diamino-3,5-dinitropyridine and the selectivity of 2,3,6-triamino-5-nitropyridine are shown in Table 1.

[0130] The average particle size of the active component Pd in ​​the catalyst prepared by the above method of the present invention is 2-3 nm.

[0131] In the catalyst prepared by the above method of the present invention, the content of active component Pd in ​​the catalyst is estimated based on the total weight of Pd element in the precursor solution of active component Pd and the added support being 100wt%.

[0132] Comparative Example 1

[0133] The catalyst was prepared using a method that was basically the same as that in Example 1. The only difference was that the passivation step was not performed in Comparative Example 1. If the reduced catalyst was not passivated, it would burn directly when it came into contact with air and would be unusable.

[0134] Comparative Example 2

[0135] The catalyst was prepared using essentially the same method as in Example 1, except that the catalyst in Comparative Example 2 was not subjected to an oxidation treatment step.

[0136] The catalyst obtained by the above method was used to synthesize 2,3,6-triamino-5-nitropyridine using the same preparation method as in Example 1. The yield of 2,3,6-triamino-5-nitropyridine was 15%, and the purity was 95%.

[0137] The catalyst prepared by the above method was used to catalyze the synthesis of the polymerization intermediate 2,3,6-triamino-5-nitropyridine. The specific hydrogenation conversion of 2,6-diamino-3,5-dinitro and the selectivity of 2,3,6-triamino-5-nitropyridine are shown in Table 1.

[0138] Comparative Example 3

[0139] The catalyst was prepared using a method that was basically the same as that in Example 1, except that the catalyst in Comparative Example 3 used alumina as a support.

[0140] The catalyst obtained by the above method was used to synthesize 2,3,6-triamino-5-nitropyridine using the same preparation method as in Example 1. The yield of 2,3,6-triamino-5-nitropyridine was 10%, and the purity was 92%.

[0141] The catalyst prepared by the above method was used to catalyze the synthesis of the polymerization intermediate 2,3,6-triamino-5-nitropyridine. The specific hydrogenation conversion of 2,6-diamino-3,5-dinitro and the selectivity of 2,3,6-triamino-5-nitropyridine are shown in Table 1.

[0142] The specific hydrogenation conversion rates of 2,6-diamino-3,5-dinitro and the selectivity of 2,3,6-triamino-5-nitropyridine prepared by the catalysts in the above embodiments and comparative examples of the present invention during the synthesis of 2,3,6-triamino-5-nitropyridine are shown in Table 1.

[0143] Table 1

[0144]

[0145] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0146] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0147] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0148] In the context of this specification, except where expressly stated otherwise, any matters or issues not mentioned shall apply directly to those known in the art without any modification.

Claims

1. The application of a catalyst in the synthesis of 2,3,6-triamino-5-nitropyridine, characterized in that: The catalyst includes a support and an active component Pd supported on the support; The active component Pd includes oxidized Pd and reduced Pd elements; the mass content of oxidized Pd in ​​the active component Pd is 50%-80%. Based on a total weight of 100wt% for the active component Pd and the support in the catalyst, the content of the active component Pd is 3-5wt%; the support is selected from carbon materials. The precursor solution of the active component Pd was mixed and impregnated with the support, aged, dried, reduced, passivated, and oxidized to obtain the catalyst.

2. The application according to claim 1, characterized in that: The average particle size of the active component Pd is 2-3 nm.

3. The application according to claim 1, characterized in that: The carrier is selected from at least one of carbon nanotubes and activated carbon.

4. The application according to claim 1, characterized in that: In the catalyst preparation method, based on the total weight of Pd element in the precursor solution of active component Pd and the added support being 100wt%, the amount of Pd element added in the precursor solution of active component Pd is 3wt%-5wt%.

5. The application according to claim 4, characterized in that: The precursor solution of the active component Pd contains 0.5wt%-0.8wt% of Pd.

6. The application according to claim 1, characterized in that: In the catalyst preparation method, under stirring conditions, the precursor solution of the active component Pd is dropwise added to the support for mixing and impregnation.

7. The application according to claim 6, characterized in that: The precursor solution of the active component Pd is added dropwise to the carrier for mixing and impregnation, and the dropwise addition time is 1h-3h.

8. The application according to claim 1, characterized in that: The aging time is 12-16 hours; and / or, The aging temperature is room temperature; and / or, The drying temperature is 100-120℃; and / or, The drying time is 8-12 hours.

9. The application according to claim 1, characterized in that: The reduction temperature is 160~250℃; and / or, The reduction time is 2-4 hours; and / or, The reducing atmosphere is hydrogen.

10. The application according to claim 1, characterized in that: Passivation is performed using a mixture of oxygen and a protective gas.

11. The application according to claim 10, characterized in that: The protective gas is selected from at least one of nitrogen and argon.

12. The application according to claim 11, characterized in that: The volume content of oxygen in the gas mixture is 1%-2%; and / or, The passivation temperature is room temperature; and / or, The passivation time is 1-2 hours.

13. The application according to claim 1, characterized in that: Air is introduced to induce oxidation.

14. The application according to claim 13, characterized in that: The oxidation temperature is 20-50℃; and / or, The oxidation time is 8-12 hours.

15. The application according to claim 1, characterized in that: A method for synthesizing 2,3,6-triamino-5-nitropyridine includes the following steps: 2,6-Diamino-3,5-dinitropyridine and a catalyst were mixed in an organic solvent, and hydrogen was introduced to carry out a hydrogenation reaction. After post-treatment, 2,3,6-triamino-5-nitropyridine was obtained.

16. The application according to claim 15, characterized in that: The organic solvent is selected from alcohol solvents; and / or, The mass ratio of the organic solvent to 2,6-diamino-3,5-dinitropyridine is 1:8-15; and / or, The mass ratio of catalyst to 2,6-diamino-3,5-dinitropyridine is ≥1:5; and / or, The hydrogen pressure is maintained at 0.5-1.5 MPa.

17. The application according to claim 16, characterized in that: The organic solvent is selected from at least one of methanol and ethanol; and / or, The mass ratio of the catalyst to 2,6-diamino-3,5-dinitropyridine is 1:5-7.

18. The application according to claim 15, characterized in that: The temperature for hydrogenation reactions is 35-55℃; and / or, The hydrogenation reaction takes 6-12 hours.

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