Catalyst, preparation method thereof and application of catalyst in synthesis of 2, 3, 6-triamino-5-nitropyridine

Abstract

The invention discloses a catalyst, a preparation method of the catalyst and application of the catalyst in synthesis of 2, 3, 6-triamino-5-nitropyridine. The catalyst comprises a carrier and an active component Pd loaded on the carrier, the active component Pd comprises an oxidation-state Pd element and a reduction-state Pd element; and the mass content of the Pd element in the oxidation state in the active component Pd is 50-80%. By regulating and controlling the oxidation state of the active component Pd of the catalyst, the electronic structure of the catalyst can be changed, and the catalytic activity of the catalyst is improved. When 2, 3, 6-triamino-5-nitropyridine is synthesized through the catalyst, the hydrogenation conversion rate of 2, 6-diamino-3, 5-dinitro can be 100%, the selectivity of 2, 3, 6-triamino-5-nitropyridine can be 95% or above, and the yield of 2, 3, 6-triamino-5-nitropyridine can be 85% or above. Therefore, the catalyst disclosed by the invention is high in catalytic activity and mild and efficient in reaction condition.

Description

Technical Field

[0001] The invention relates to the technical field of organic synthesis, and more particularly to a catalyst and a preparation method thereof and an application thereof in the synthesis of 2,3,6-triamino-5-nitropyridine. Background Art

[0002] Poly (2,5-dihydroxy-1,4-phenylene pyridinium diimidazole) (PIPD) is a high-performance synthetic fiber obtained by the polymerization of 2,3,5,6-tetraaminopyridine (TAP) and 2,5-dihydroxyterephthalic acid. The tensile and compressive properties of PIPD fibers have unparalleled advantages among all high-performance fibers, and due to the large number of polar functional groups -OH on the molecular chain, PIPD fibers have good surface wettability and composite adhesion, which makes up for the shortcomings of PBO fibers in this regard.

[0003] However, 2,3,5,6-tetraaminopyridine (TAP) has poor stability and needs to be prepared as hydrochloride. In addition, it is still easily oxidized during the polymerization process. 2,3,6-Triamino-5-nitropyridine (TANP) is an intermediate product of 2,6-diamino-3,5-dinitropyridine (DADNP) hydrogenation to synthesize TAP, and can be used as a precursor for reduction to synthesize 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.41No.5Oct.2013), in which sodium polysulfide and hydrazine hydrate are used to reduce 2,6-diamino-3,5-dinitropyridine to obtain 2,3,6-triamino-5-nitropyridine, but the method is relatively complicated and the reaction conditions are severe. In addition, the synthesized substance contains trace amounts of sulfur impurities.

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

[0006] In order to solve the problems in the prior art, the present invention proposes a catalyst and a preparation method thereof and an application in the synthesis of 2,3,6-triamino-5-nitropyridine. The present invention first prepares a new catalyst, and by regulating the oxidation state of the active component Pd of the catalyst, the electronic structure of the catalyst can be changed and the catalytic activity of the catalyst can be improved. The catalyst of the present invention is used to catalyze the synthesis of the polymerization intermediate 2,3,6-triamino-5-nitropyridine, and the 2,6-diamino-3,5-dinitro hydrogenation conversion rate can be 100%, the selectivity of 2,3,6-triamino-5-nitropyridine can be above 95%, and the yield can be above 85%. Therefore, the catalyst of the present invention can make the reaction stay well on the mononitro hydrogenation product, the catalytic activity is high, and the reaction conditions are mild and efficient.

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

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

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

[0010] In the catalyst of the present invention, preferably,

[0011] The content of the active component Pd is 3-5wt% based on the total weight of the active component Pd and the carrier in the catalyst as 100wt%; 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 the present invention, the Pd nanoparticles have a strong interaction with the carbon material and can be well loaded on the carbon material.

[0016] The second object of the present invention is to provide a method for preparing a catalyst, comprising the following steps:

[0017] The precursor solution of the active component Pd and the carrier are mixed and impregnated, aged, dried, reduced, passivated, and oxidized to obtain a catalyst;

[0018] It is preferably used for the preparation of the catalyst described in any one of the purposes of the present invention.

[0019] Compared with the existing common catalyst preparation method, the catalyst preparation step of the present invention further includes a passivation and oxidation step, which increases the proportion of the oxidation state of the catalyst surface and improves the selectivity of the catalyst.

[0020] In the method for preparing the catalyst of the present invention, preferably,

[0021] Taking the total weight of the Pd element in the precursor solution of the active component Pd and the added carrier as 100wt%, the added amount of the Pd element in the precursor solution of the active component Pd is 3wt%-5wt%; preferably, the content of the Pd element in the precursor solution of the active component Pd is 0.5wt%-0.8wt%.

[0022] In the method for preparing the catalyst of the present invention, preferably,

[0023] Under stirring conditions, the precursor solution of the active component Pd is dripped into the carrier for mixing and impregnation. Preferably, the dripping time is 1 h to 3 h.

[0024] In the present invention, the carrier may be heat-treated with an acid before use, preferably with nitric acid at 80-100° C. for 8-12 h.

[0025] In the present invention, the impregnation method is preferably equal volume impregnation, and the impregnation temperature is room temperature.

[0026] In the method for preparing the catalyst of the present 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°C; and / or,

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

[0031] In the method for preparing the catalyst of the present invention, preferably,

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

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

[0034] The reducing atmosphere is hydrogen.

[0035] In the method for preparing the catalyst of the present invention, preferably,

[0036] Passivation is carried out using a mixture of oxygen and 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 mixed gas is 1%-2%; and / or,

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

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

[0042] In the method for preparing the catalyst of the present invention, preferably,

[0043] Air is introduced for oxidation;

[0044] Preferably,

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

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

[0047] In the method for preparing the catalyst of the present invention, most preferably,

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

[0049] Slowly adding the precursor solution of step (1) into a certain amount of commercial carbon nanotubes while stirring, and aging and drying after the addition is complete to obtain an unreduced catalyst;

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

[0051] The third object of the present invention is to provide a catalyst as described in any one of the objects of the present invention or a catalyst prepared by the method described in any one of the objects of the present invention in the synthesis of 2,3,6-triamino-5-nitropyridine.

[0052] A fourth object of the present 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 are mixed in an organic solvent, hydrogen is introduced to carry out a hydrogenation reaction, and post-processing is performed to obtain 2,3,6-triamino-5-nitropyridine;

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

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

[0056]

[0057] In the method for synthesizing 2,3,6-triamino-5-nitropyridine of 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 the catalyst to 2,6-diamino-3,5-dinitropyridine is ≥ 1:5; preferably 1:5-7; and / or,

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

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

[0063] The temperature of the hydrogenation reaction is 35-55°C; and / or,

[0064] The hydrogenation reaction time is 6-10h.

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

[0066] The solid mixture is obtained by first solid-liquid separation after the hydrogenation reaction, and then a solvent (such as DMSO) is added to dissolve the hydrogenation reaction product in the solid mixture. Secondary solid-liquid separation is performed to obtain a separated liquid, and ice water is added to the separated liquid to crystallize 2,3,6-triamino-5-nitropyridine.

[0067] In the method for synthesizing 2,3,6-triamino-5-nitropyridine of the present invention, most preferably,

[0068] The method comprises the following steps: using methanol as a solvent, placing a raw material 2,6-diamino-3,5-dinitropyridine and a corresponding catalyst into a reaction kettle, introducing hydrogen gas for hydrogenation reaction, wherein the products after the reaction are solid and catalyst powder, placing the solid product and the catalyst powder into a DMSO solution, dissolving the product, and then adding ice water into the DMSO solution to obtain a 2,3,6-triamino-5-nitropyridine product;

[0069] The endpoints and any values ​​of the scope disclosed in the present invention are not limited to the precise scope or value, and these scopes or values ​​should be understood to include values ​​close to these scopes or values. For numerical ranges, the endpoint values ​​of each scope, the endpoint values ​​of each scope and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be regarded as specifically disclosed in this article.

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

[0071] The method for synthesizing 2,3,6-triamino-5-nitropyridine is simple, the yield is high, and the reaction conditions are mild.

[0072] The inventors have found that by regulating the oxidation state of the catalyst, the electronic structure of the catalyst can be changed, so that the reaction stays at the mononitro hydrogenation product. Compared with the existing method of reducing with sodium polysulfide and hydrazine hydrate, the catalytic reduction method of the present invention is simpler and has milder reaction conditions. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0075] Figure 3 This is the XPS graph of the catalyst obtained in Example 1. DETAILED DESCRIPTION

[0076] The present invention is described in detail below in conjunction with specific drawings and embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the content of the present invention still fall 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 specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0078] In addition, the various embodiments of the present invention may be arbitrarily combined as long as they do not violate the concept of the present invention. The technical solutions thus formed belong to part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0079] The raw materials used in the examples and comparative examples, unless otherwise specified, are disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0080] Example 1

[0081] Preparation of catalyst:

[0082] 60 g of a chloropalladic acid-water solution having a palladium content of 0.5 wt % was prepared as an impregnation solution;

[0083] Take 10g of commercial carbon nanotube carrier, slowly add the impregnation solution to the carrier and keep stirring. After the addition is completed for 3h, age for 12h, dry at 120 degrees Celsius for 12h, reduce at 200 degrees Celsius for 2h, and then pass 1% O2 / Ar for passivation; pass air at 25°C for deep oxidation for 12h to obtain the catalyst.

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

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

[0086] 5 g of 2,6-diamino-3,5-dinitropyridine (dadnp), 1 g of the above catalyst, and 50 mL of methanol were put into a 100 mL reactor, the hydrogen pressure was 1.0 MPa, the reaction temperature was 40 degrees Celsius, the reaction was carried out for 8 hours, the solid and the reaction liquid were separated, DMSO was added, 2,3,6-triamino-5-nitropyridine (TANP) was dissolved, the catalyst was filtered, the DMSO solution of TANP was added to ice water, TANP crystallized, the yield was 85.0%, there was no impurity peak in the liquid chromatography, the purity was above 99.5%, and the NMR spectrum of the obtained 2,3,6-triamino-5-nitropyridine product was as follows Figure 1 and Figure 2 shown.

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

[0088] Example 2

[0089] Preparation of catalyst:

[0090] 60 g of a chloropalladic acid-water solution having a palladium content of 0.65 wt % was prepared as an impregnation solution;

[0091] Take 10g of commercial carbon nanotube carrier, slowly add the impregnation solution to the carrier, and keep stirring. After the addition is completed for 3h, age for 12h, dry at 120 degrees Celsius for 12h, reduce at 200 degrees Celsius for 2h, and then pass 1% O2 / Ar for passivation; pass air at 25°C for deep oxidation for 12h 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. The same synthesis method and post-treatment method as in Example 1 were used. The yield of the obtained 2,3,6-triamino-5-nitropyridine was 82.5% and the purity was 99.5%. The specific 2,6-diamino-3,5-dinitro hydrogenation conversion rate and 2,3,6-triamino-5-nitropyridine selectivity are shown in the results shown in Table 1.

[0094] Example 3

[0095] Preparation of catalyst:

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

[0097] Take 10g of commercial carbon nanotube carrier, slowly add the impregnation solution to the carrier, and keep stirring. After the addition is completed for 3h, age for 12h, dry at 120 degrees Celsius for 12h, reduce at 200 degrees Celsius for 2h, and then pass 1% O2 / Ar for passivation; pass air at 25°C for deep oxidation for 12h 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. The same synthesis method and post-treatment method as in Example 1 were used. The yield of the obtained 2,3,6-triamino-5-nitropyridine was 78.7% and the purity was 98.0%. The specific 2,6-diamino-3,5-dinitro hydrogenation conversion rate and 2,3,6-triamino-5-nitropyridine selectivity are shown in the results shown in Table 1.

[0100] Example 4

[0101] Preparation of catalyst:

[0102] 60 g of a chloropalladic acid-water solution having a palladium content of 0.5 wt % was prepared as an impregnation solution;

[0103] Take 10g of commercial carbon nanotube carrier, slowly add the impregnation solution to the carrier, and keep stirring. After the addition is completed for 3h, age for 12h, dry at 120 degrees Celsius for 12h, reduce at 200 degrees Celsius for 2h, and then pass 1% O2 / Ar for passivation; pass air at 25°C for deep oxidation for 8h 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. The same synthesis method and post-treatment method as in Example 1 were used. The yield of the obtained 2,3,6-triamino-5-nitropyridine was 84.5% and the purity was 99.5%. The specific 2,6-diamino-3,5-dinitro hydrogenation conversion rate and 2,3,6-triamino-5-nitropyridine selectivity are shown in the results shown in Table 1.

[0106] Example 5

[0107] Preparation of catalyst:

[0108] 60 g of a chloropalladic acid-water solution having a palladium content of 0.5 wt % was prepared as an impregnation solution;

[0109] Take 10g of commercial carbon nanotube carrier, slowly add the impregnation solution to the carrier, and keep stirring. After the addition is completed for 3h, age for 12h, dry at 120 degrees Celsius for 12h, reduce at 160 degrees Celsius for 2h, and then pass 1% O2 / Ar for passivation; pass air at 25°C for deep oxidation for 12h 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. The same synthesis method and post-treatment method as in Example 1 were used. The yield of the obtained 2,3,6-triamino-5-nitropyridine was 84.8% and the purity was 99.5%. The specific 2,6-diamino-3,5-dinitro hydrogenation conversion rate and 2,3,6-triamino-5-nitropyridine selectivity are shown in the results shown in Table 1.

[0112] Example 6

[0113] Preparation of catalyst:

[0114] 60 g of a chloropalladic acid-water solution having a palladium content of 0.5 wt % was prepared as an impregnation solution;

[0115] Take 10g of commercial carbon nanotube carrier, slowly add the impregnation solution to the carrier, and keep stirring. After the addition is completed for 3h, age for 12h, dry at 120 degrees Celsius for 12h, reduce at 250 degrees Celsius for 2h, and then pass 1% O2 / Ar for passivation; pass air at 25°C for deep oxidation for 12h 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. The same synthesis method and post-treatment method as in Example 1 were used. The yield of the obtained 2,3,6-triamino-5-nitropyridine was 83.5% and the purity was 99.5%. The specific 2,6-diamino-3,5-dinitro hydrogenation conversion rate and 2,3,6-triamino-5-nitropyridine selectivity are shown in the results shown in Table 1.

[0118] Example 7

[0119] Preparation of catalyst:

[0120] 60 g of a chloropalladic acid-water solution having a palladium content of 0.5 wt % was prepared as an impregnation solution;

[0121] Take 10g of commercial carbon nanotube carrier, slowly add the impregnation solution to the carrier, and keep stirring. After the addition is completed for 3h, age for 12h, dry at 120 degrees Celsius for 12h, reduce at 200 degrees Celsius for 2h, and then pass 1% O2 / Ar for passivation; pass air at 45°C for deep oxidation for 12h 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. The rest of the synthesis method and post-treatment method were the same as in Example 1. The yield of the obtained 2,3,6-triamino-5-nitropyridine was 75.0% and the purity was 83%. The specific 2,6-diamino-3,5-dinitro hydrogenation conversion rate and 2,3,6-triamino-5-nitropyridine selectivity are shown in the results shown in Table 1.

[0124] Example 8

[0125] Preparation of catalyst:

[0126] 60 g of a chloropalladic acid-water solution having a palladium content of 0.5 wt % was prepared as an impregnation solution;

[0127] Take 10g of commercial carbon nanotube carrier, slowly add the impregnation solution to the carrier, and keep stirring. After the addition is completed for 3h, age for 12h, dry at 120 degrees Celsius for 12h, reduce at 200 degrees Celsius for 2h, and then pass 1% O2 / Ar for passivation; pass air at 45°C for deep oxidation for 12h 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. The rest of the synthesis method and post-treatment method were the same as in Example 1. The yield of the obtained 2,3,6-triamino-5-nitropyridine was 84.0% and the purity was 99.0%. The specific 2,6-diamino-3,5-dinitro hydrogenation conversion rate and 2,3,6-triamino-5-nitropyridine selectivity are shown in the results shown in Table 1.

[0130] The average particle size of the active component Pd in ​​the catalyst prepared by the 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 the active component Pd in ​​the prepared catalyst is calculated based on the total weight of the Pd element in the precursor solution of the active component Pd and the added carrier as 100wt%.

[0132] Comparative Example 1

[0133] The catalyst is prepared by a method substantially the same as that in Example 1, except that the passivation treatment step is not performed in Example 1. If the reduced catalyst is not passivated and encounters air, it will directly burn and cannot be used.

[0134] Comparative Example 2

[0135] The catalyst is prepared by a method substantially the same as that of Example 1, except that the catalyst in Comparative Example 2 is 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 the obtained 2,3,6-triamino-5-nitropyridine was 15% and the purity was 95%.

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

[0138] Comparative Example 3

[0139] The catalyst is prepared by a method substantially the same as that of Example 1, except that the catalyst in Comparative Example 3 uses alumina as a carrier.

[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 the obtained 2,3,6-triamino-5-nitropyridine was 10% and the purity was 92%.

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

[0142] When the catalysts prepared in the above embodiments and comparative examples of the present invention are used to synthesize 2,3,6-triamino-5-nitropyridine, the specific 2,6-diamino-3,5-dinitro hydrogenation conversion rate and 2,3,6-triamino-5-nitropyridine selectivity are shown in Table 1.

[0143] Table 1

[0144]

[0145] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached 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 conventionally understood by those skilled in the art. In the event of a conflict, the definition in this specification shall prevail.

[0147] When this specification uses the prefix "well-known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, etc., the objects introduced by the prefix cover those commonly used in the art when this application is filed, but also include those that are not commonly used at present but will become recognized in the art as being suitable for similar purposes.

[0148] In the context of the present specification, any matters or items not mentioned are directly applicable to those known in the art without any changes except those explicitly stated.

Claims

1. A catalyst comprising a carrier and an active component Pd supported on the carrier; The active component Pd includes an oxidized Pd element and a reduced Pd element; the mass content of the oxidized Pd element in the active component Pd is 50%-80%.

2. The catalyst according to claim 1, characterized in that: The content of the active component Pd is 3-5wt% based on the total weight of the active component Pd and the carrier in the catalyst as 100wt%; and / or, The average particle size of the active component Pd is 2-3 nm; and / or, The carrier is selected from carbon materials; Preferably, the carrier is selected from at least one of carbon nanotubes and activated carbon.

3. A method for preparing a catalyst, characterized in that: The following steps are involved: The precursor solution of the active component Pd and the carrier are mixed and impregnated, aged, dried, reduced, passivated, and oxidized to obtain a catalyst; It is preferably used for the preparation of the catalyst according to any one of claims 1 to 2.

4. The method for preparing the catalyst according to claim 3, characterized in that: Taking the total weight of the Pd element in the precursor solution of the active component Pd and the added carrier as 100wt%, the added amount of the Pd element in the precursor solution of the active component Pd is 3wt%-5wt%; preferably, the content of the Pd element in the precursor solution of the active component Pd is 0.5wt%-0.8wt%.

5. The method for preparing the catalyst according to claim 3, characterized in that: Under stirring conditions, the precursor solution of the active component Pd is dripped into the carrier for mixing and impregnation. Preferably, the dripping time is 1 h to 3 h.

6. The method for preparing the catalyst according to claim 3, 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°C; and / or, The drying time is 8-12 hours.

7. The method for preparing the catalyst according to claim 3, characterized in that: The reduction temperature is 160-250° C.; and / or, The reduction time is 2 to 4 hours; and / or, The reducing atmosphere is hydrogen.

8. The method for preparing the catalyst according to claim 3, characterized in that: Passivation is carried out using a mixture of oxygen and protective gas; Preferably, the protective gas is selected from at least one of nitrogen and argon; More preferably, The volume content of oxygen in the mixed gas is 1%-2%; and / or, The passivation temperature is room temperature; and / or, The passivation time is 1-2h.

9. The method for preparing the catalyst according to claim 3, characterized in that: Air is introduced for oxidation; Preferably, The oxidation temperature is 20-50°C; and / or, The oxidation time is 8-12h.

10. Use of the catalyst according to any one of claims 1 to 2 or the catalyst prepared by the method according to any one of claims 3 to 9 in the synthesis of 2,3,6-triamino-5-nitropyridine.

11. A method for synthesizing 2,3,6-triamino-5-nitropyridine, comprising the following steps: 2,6-diamino-3,5-dinitropyridine and a catalyst are mixed in an organic solvent, hydrogen is introduced to carry out a hydrogenation reaction, and post-processing is performed to obtain 2,3,6-triamino-5-nitropyridine; The catalyst is selected from the catalyst described in any one of claims 1 to 2 or the catalyst prepared by the method described in any one of claims 3 to 9.

12. The method for synthesizing 2,3,6-triamino-5-nitropyridine according to claim 11, characterized in that: The organic solvent is selected from alcohol solvents, preferably at least one of methanol and ethanol; 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 the catalyst to 2,6-diamino-3,5-dinitropyridine is ≥ 1:5; preferably 1:5-7; and / or, The hydrogen pressure is maintained at 0.5-1.5Mpa.

13. The method for synthesizing 2,3,6-triamino-5-nitropyridine according to claim 11, characterized in that: The temperature of the hydrogenation reaction is 35-55°C; and / or, The hydrogenation reaction time is 6-12h.

Images