Preparation and application of catalyst for hydrogen cyanide production by direct oxidation of methane and ammonia

Abstract

The application provides a preparation and application of a catalyst for hydrogen cyanide prepared by direct oxidation of methane and ammonia. The method comprises the following steps: dissolving a soluble platinum salt, a tungsten salt and a cerium salt in water, adding an organic amine to obtain an alkaline metal salt complex solution, and adding methyl glycine diacetic acid trisodium salt MGDA to obtain a three-component solution of metal-organic amine-MGDA; adding the three-component solution into a hydrothermal kettle, adding a silicon source and a template agent, and performing crystallization, washing, drying and calcination to obtain a catalyst precursor encapsulating metal; mixing the catalyst precursor with a promoter and a process aid, adding a binder, and performing extrusion, pelletizing and calcination to obtain a target catalyst. The method solves the problems of harsh reaction conditions, easy carbon deposition of the catalyst and easy loss of platinum in the prior art. The reaction temperature is lower than 600 DEG C, the yield of hydrogen cyanide is greater than 85%, the platinum loss is lower than 0.2 ‰ after 200 h of operation, and the carbon deposition is lower than 0.05 ‰.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of industrial catalysis, and particularly relates to a preparation method and application of a catalyst for preparing hydrogen cyanide by directly oxidizing methane and ammonia. BACKGROUND

[0002] Hydrogen cyanide (HCN) is a highly toxic chemical that can be miscible with water, has a boiling point of 26 DEG C and a freezing point of -14 DEG C. HCN is a basic raw material for organic synthesis, and has a wide range of uses and a large demand, such as hexanediamine, t-butylamine, triethyl orthoformate, methionine, sodium cyanide, pesticide intermediates and herbicides.

[0003] Main production processes of hydrogen cyanide include a methanol method, a methane method, a direct oxidation method of methanol and ammonia, and a propylene cyanide by-product method. The direct oxidation method of methanol and ammonia is a method for directly producing hydrogen cyanide, and the equation is as follows:

[0004] NH3+CH4→HCN+3H2

[0005] The reaction uses a platinum mesh catalyst, and the reaction temperature is 1000 DEG C. Since the carbon deposition of the catalyst is relatively serious at high temperature, the service life of the catalyst is greatly affected, and platinum is easily lost, which is poor in economy.

[0006] Therefore, there is an urgent need in the art for a new solution to the problems of harsh reaction conditions, easy carbon deposition of the catalyst and easy loss of platinum. SUMMARY

[0007] In view of the above problems, one of the purposes of the present application is to provide a preparation method of a hydrogen cyanide catalyst, which solves the problems of harsh reaction conditions, easy carbon deposition of the catalyst and easy loss of platinum in the prior art. When a fixed bed reactor is used to evaluate the reaction, the reaction temperature is lower than 600 DEG C, the yield of hydrogen cyanide is greater than 85%, the platinum loss is less than 0.2 ‰ after 200 hours of operation, and the carbon deposition is less than 0.05 ‰.

[0008] To achieve the above purposes, the technical scheme of the present application is as follows:

[0009] A preparation method of a hydrogen cyanide catalyst, the method comprising the following steps:

[0010] S1: Dissolve a soluble platinum salt, a tungsten salt and a cerium salt in water, add an organic amine to obtain an alkaline metal salt complex solution, and add methyl glycine diacetic acid trisodium salt (MGDA) to obtain a three-component solution of metal-organic amine-MGDA;

[0011] S2: Add the three-component solution to an autoclave, add a silicon source and a template agent, and perform crystallization, washing, drying and calcination to obtain a catalyst precursor encapsulating metal;

[0012] S3: mixing the catalyst precursor with the cocatalyst, process aid, adding a binder, extruding, cutting, and calcining to obtain the target catalyst.

[0013] In the catalyst component of the present application, the main catalyst is platinum, tungsten and cerium three metals. By in-situ encapsulation, platinum-tungsten-cerium three metals are encapsulated inside the molecular sieve channel to improve its stability and reduce loss. During in-situ synthesis, the addition of organic amine can reduce the agglomeration of metals inside the catalyst, improve its acid distribution, and thus improve its catalytic activity. The cocatalyst is an alkaline earth metal, which is loaded by molding and impregnation to obtain the catalyst. The presence of the cocatalyst can significantly reduce the carbon deposition of the catalyst and improve the service life of the catalyst.

[0014] In an embodiment of the present application, the platinum salt in S1 is one or more of tetraammine platinum nitrate, platinum acetylacetone, platinum nitrate, platinum sulfate, and platinum chloride.

[0015] In an embodiment of the present application, the cerium salt in S1 is cerium nitrate and / or cerium chloride.

[0016] In an embodiment of the present application, the tungsten salt in S1 is one or more of sodium tungstate, potassium tungstate, and ammonium tungstate; preferably, the mass concentration of each component in the three-component solution is 1-10wt%.

[0017] In an embodiment of the present application, the organic amine in S1 is an aromatic organic amine, preferably one or more of p-toluidine, m-phenylenediamine, and o-bromoaniline; preferably, the molar ratio of the organic amine to the metal is 0.8-1.2:1.

[0018] In an embodiment of the present application, the MGDA in S1 is added in equimolar ratio with the organic amine.

[0019] In an embodiment of the present application, the silicon source in S2 is one or more of tetraethyl orthosilicate, tetrabutyl orthosilicate, and water glass, preferably tetraethyl orthosilicate.

[0020] In an embodiment of the present application, the template agent in S2 is tetrapropylammonium hydroxide and / or tetrapropylammonium bromide; preferably, the molar ratio of the silicon source to the template agent is 5-10:1.

[0021] In an embodiment of the present application, the amount of the three-component solution added in S2 is 50-150% of the mass of the silicon source.

[0022] In an embodiment of the present application, the crystallization temperature in S2 is 180℃, and the crystallization time is 48-72h.

[0023] In an embodiment of the present application, in S2, washing is performed until neutral.

[0024] In an embodiment of the present application, the calcination temperature in S2 is 500-550℃, and the calcination time is 4-8h.

[0025] In an embodiment of the present application, the promoter in S3 is one or more of alkaline earth metals. Preferably, the mass ratio of the promoter to the precursor is 0.01-0.05:1 in terms of metal salt.

[0026] In an embodiment of the present application, the process additive in S3 is one or more of Job's tears powder, hydroxymethyl cellulose, graphite, preferably Job's tears powder; preferably, the mass ratio of the process additive to the precursor is 0.05-0.1:1.

[0027] In an embodiment of the present application, the binder in S3 is one or more of nitric acid, sulfuric acid, silica sol; preferably, the mass ratio of the binder to the precursor is 0.1-0.5:1.

[0028] In an embodiment of the present application, S3 is calcined at 480-550℃ for 3-8h.

[0029] Another object of the present application is to provide a catalyst for preparing hydrogen cyanide.

[0030] A catalyst for preparing hydrogen cyanide, which is obtained by the above preparation method, and uses the metal-organic amine-MGDA three-component as the catalyst precursor.

[0031] Still another object of the present application is to provide the use of a catalyst for preparing hydrogen cyanide.

[0032] The use of a catalyst for preparing hydrogen cyanide, which is the catalyst obtained by the above preparation method, or the catalyst described above, and is used for catalyzing the direct reaction of methane and ammonia to prepare hydrogen cyanide.

[0033] Compared with the prior art, the positive effects of the present application are:

[0034] (1) The preparation of the core-shell structure catalyst anchors the main catalyst metal to the inside of the molecular sieve channel, improves its stability through confinement, and avoids metal loss.

[0035] (2) The in-situ formation with alkaline earth metal obtains a multifunctional catalyst, and the alkaline earth metal can reduce the carbon deposition of the catalyst and improve the catalyst life. Specific embodiments

[0036] The following examples are intended to explain the present application, which is not limited to the scope of the examples, and also includes any other changes within the scope of the rights claimed by the present application.

[0037] The experimental raw material information is as follows:

[0038] tetraammineplatinum nitrate analytical pure mcln sodium tungstate analytical pure mayer's reagent m-phenylenediamine analytical pure national pharmaceutical reagent o-bromoaniline analytical pure national pharmaceutical reagent mgda analytical pure aladdin tetraethyl orthosilicate analytical pure aladdin tetrapropylammonium bromide analytical pure mcln tetrapropylammonium hydroxide analytical pure mcln

[0039] The carbon deposition amount of the catalyst was determined by using a Mettler-Toledo thermogravimetric-differential thermal analyzer, the atmosphere was air, and the temperature rising rate was 20℃ / min.

[0040] The content of hydrogen cyanide in sodium hydroxide was analyzed by using the method described in GB 7486-87.

[0041] The platinum content of the catalyst before and after the reaction was analyzed by using an inductively coupled plasma emission spectrometer (ICP-OES) of Agilent Technologies Company, and the model number thereof was 720 ICP-OES.

[0042] Example 1

[0043] In a beaker, 20 g of water was taken, 1.00 g of tetraammine platinum nitrate, 1.40 g of sodium tungstate, 1.10 g of cerium nitrate, 0.9261 g of m-phenylenediamine, and 2.3238 g of MGDA were added, and stirring was performed to obtain a three-component solution.

[0044] 11.5 g of the three-component solution, 7.8 g of TEOS (tetraethyl orthosilicate), and 1 g of TPABr (tetrapropylammonium bromide) were taken, stirring was performed to obtain a uniform mixture, and the mixture was placed in an oven for crystallization at 180℃ for 72 h. After the crystallization was completed, the sample was calcined at 500℃ for 4 h to obtain a catalyst precursor sample.

[0045] 10 g of the precursor sample was taken, 0.1 g of magnesium carbonate and 0.5 g of zirconium powder were added, 2 g of silica sol was added, and stirring was performed to obtain a uniform mixture. The mixture was extruded into a strip, and the strip was cut into particles. The particles were calcined at 500℃ for 4 h to obtain catalyst A.

[0046] The catalyst was evaluated by using a molten salt fixed bed reactor. The molar ratio of the methane and ammonia feed was 1:1.1. The space velocity was 120 h-1. The evaluation temperature was 580℃. After the tail gas was absorbed by 20 wt% sodium hydroxide for 60 min, the content of hydrogen cyanide was analyzed by using a silver nitrate titration method. The carbon deposition amount of the catalyst was analyzed by using thermogravimetry after the catalyst was evaluated for 200 h. -1

[0047] Example 2

[0048] In a beaker, 20 g of water was taken, 2.00 g of tetraammine platinum nitrate, 1.80 g of sodium tungstate, 1.90 g of cerium nitrate, 3.5327 g of o-bromoaniline, and 5.5661 g of MGDA were added, and stirring was performed to obtain a three-component solution. 12 g of the three-component solution, 8 g of TEOS (tetraethyl orthosilicate), and 1.5 g of TPAOH (tetrapropylammonium hydroxide) were taken, stirring was performed to obtain a uniform mixture, and the mixture was placed in an oven for crystallization at 180℃ for 72 h. After the crystallization was completed, the sample was calcined at 550℃ for 8 h to obtain a precursor.

[0049] ​Take 10 g of precursor, 0.5 g of calcium carbonate, 1 g of rice husk powder, 5 g of silica sol, mix uniformly, extrude into strips, cut into particles, and then calcine at 540°C for 6h to obtain catalyst B.

[0050] Evaluation was carried out in the manner of Example 1.

[0051] Example 3

[0052] In a beaker, take 20 g of water, add 0.2 g of platinum acetylacetone, 0.6 g of potassium tungstate, 0.4 g of cerium chloride, 1.0535 g of o-bromoaniline, and 1.6599 g of MGDA, stir uniformly to obtain a three-component solution. Take 10 g of the three-component solution, 9.4 g of tetramethyl silicate, and 2 g of TPABr (tetrapropylammonium bromide), stir uniformly, and place in an oven for crystallization at 180°C for 48h. After crystallization, calcine at 530°C for 6h to obtain catalyst precursor sample.

[0053] Take 10 g of precursor, 0.5 g of calcium carbonate, 1 g of rice husk powder, 5 g of silica sol, mix uniformly, extrude into strips, cut into particles, and then calcine at 540°C for 6h to obtain catalyst C.

[0054] Evaluation was carried out in the manner of Example 1.

[0055] Comparative Example 1

[0056] Compared with Example 1, the only difference is that no MGDA is added, and catalyst D is obtained after calcination.

[0057] Evaluation was carried out in the manner of Example 1.

[0058] Comparative Example 2

[0059] Compared with Example 2, the only difference is that no calcium carbonate modification is added, and catalyst E is obtained.

[0060] Evaluation was carried out in the manner of Example 1.

[0061] Comparative Example 3

[0062] A traditional platinum mesh catalyst was selected, purchased from Grace Company, and labeled as catalyst F.

[0063] Evaluation was carried out in the manner of Example 1.

[0064] The following are the evaluation results of the catalysts:

[0065]

[0066]

[0067] Catalyst D shows that the presence of MGDA is beneficial to increase the dispersion of the metal, thus increasing the catalytic activity and reducing the carbon deposition. Catalyst C shows that the alkaline earth metal is a key factor to maintain the hydrogen cyanide yield. Catalyst F shows that the traditional platinum mesh catalyst has a lower yield and a more serious platinum loss when the reaction temperature is lower than 600°C.

Claims

1. A process for the preparation of a catalyst for the production of hydrogen cyanide, characterized in that The method comprises the following steps: S1: dissolving a soluble platinum salt, tungsten salt, and cerium salt in water, adding an organic amine to obtain an alkaline metal salt complex solution, and adding methyl glycine diacetic acid trisodium salt (MGDA) to obtain a three-component solution of metal-organic amine-MGDA; S2: adding the three-component solution to a hydrothermal kettle, adding a silicon source and a template agent, and performing crystallization, washing, drying, and calcination to obtain a catalyst precursor encapsulating metal; S3: mixing the catalyst precursor with a promoter and a process additive, adding a binder, and performing extrusion, granulation, and calcination to obtain a target catalyst; In S3, the promoter is one or more of alkaline earth metals.

2. The production method according to claim 1, characterized by, In S1, the platinum salt is one or more of tetraammine platinum nitrate, platinum acetylacetone, platinum nitrate, platinum sulfate, and platinum chloride; In S1, the cerium salt is cerium nitrate and / or cerium chloride; In S1, the tungsten salt is one or more of sodium tungstate, potassium tungstate, and ammonium tungstate; In S1, the organic amine is an aromatic organic amine; In S1, the molar ratio of MGDA to the organic amine is equimolar.

3. The method of claim 2, wherein, In S1, the mass concentration of each component in the three-component solution is 1-10 wt%; In S1, the organic amine is one or more of p-toluidine, m-phenylenediamine, and o-bromoaniline; In S1, the molar ratio of the organic amine to the metal is 0.8-1.2:

1.

4. The method of claim 1, wherein, In S2, the silicon source is one or more of tetraethyl orthosilicate, tetrabutyl orthosilicate, and water glass; In S2, the template agent is tetrapropylammonium hydroxide and / or tetrapropylammonium bromide; In S2, the amount of the three-component solution added is 50-150% of the mass of the silicon source; In S2, the crystallization temperature is 180°C, and the crystallization time is 48-72 h; In S2, the washing is performed to neutral; In S2, the calcination temperature is 500-550°C, and the calcination time is 4-8 h.

5. The method of claim 4, wherein, In S2, the silicon source is tetraethyl orthosilicate; In S2, the molar ratio of the silicon source to the template agent is 5-10:

1.

6. The method of claim 1, wherein, In S3, the mass ratio of the promoter to the precursor is 0.01-0.05:1, calculated based on the metal salt; In S3, the process additive is one or more of bamboo powder, hydroxymethyl cellulose, and graphite; In S3, the binder is one or more of nitric acid, sulfuric acid, and silica sol; In S3, the calcination is performed at 480-550°C for 3-8 h.

7. The method of claim 6, wherein, In S3, the process additive is bamboo powder; In S3, the mass ratio of the process additive to the precursor is 0.05-0.1:1; In S3, the mass ratio of the binder to the precursor is 0.1-0.5:

1.

8. A catalyst for the production of hydrogen cyanide, which is obtained by the production method according to any one of claims 1 to 7, characterized in that, The catalyst uses a three-component of metal-organic amine-MGDA as a catalyst precursor.

9. Use of a catalyst for preparing hydrogen cyanide, wherein the catalyst is obtained by the preparation method according to any one of claims 1-7 or is the catalyst according to claim 8, and the catalyst is used for catalyzing the direct reaction of methane and ammonia to prepare hydrogen cyanide.

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