A methanol ammoxidation catalyst and its preparation method and application

Abstract

The invention discloses a methanol ammoxidation catalyst and its preparation method and application, wherein the catalyst mass percentage composition includes: carrier 10-90%, molybdenum 2-30%, iron 5-40%, 2,2-bipyridine-5-5-dicarboxylic acid 1-10%. The catalyst has a simple structure, a large pore structure, and high stability and strength. The catalyst is used to prepare hydrocyanic acid, and a higher yield can be obtained. Even under a lower ammonia-oxygen ratio, the generation of by-product hydroxyacetonitrile can be effectively reduced, and the selectivity of hydrocyanic acid is significantly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysis and relates to a methanol ammoxidation catalyst, and specifically relates to an iron-molybdenum catalyst for preparing hydrocyanic acid through methanol ammoxidation, and a preparation method and application thereof. Background Art

[0002] Hydrocyanic acid is a widely used chemical raw material intermediate that can be used to manufacture nylon, pesticides, acrylonitrile, acrylic acid and resins, etc., and has a large market space.

[0003] The methods for producing hydrocyanic acid include Angle method, flame method, Chauvin dry method, acrylonitrile by-product method, light oil cracking method and methanol ammoxidation method. my country mainly uses acrylonitrile by-product method, methanol ammoxidation method and light oil cracking method. The reaction temperature of methane ammoxidation method is relatively high, and the yield of hydrocyanic acid can only reach 60%-70%. The high reaction temperature brings unsafe factors. The acrylonitrile by-product method is to catalyze the synthesis of acrylonitrile with propylene, air and ammonia as raw materials, and at the same time, some hydrocyanic acid is produced as a by-product. Due to the continuous improvement of acrylonitrile catalysts, the by-product HCN is becoming less and less. The light oil cracking method uses light oil and petroleum coke as the main raw materials, and reacts with ammonia at high temperature to synthesize hydrocyanic acid. This production process requires intermittent addition of solid coke, and the synthesis process is unstable, making it difficult to produce on a large scale.

[0004] Therefore, people are actively seeking other process routes. Methanol is cheap, widely available, and the pressure and temperature of the process route are both within a controllable range. The preparation of hydrocyanic acid by methanol ammoxidation has attracted increasing attention. In this process route, the most critical factor is the catalyst.

[0005] Among the reported hydrocyanic acid catalysts, Mo-based catalysts are already a relatively mature catalyst in the preparation of methanol ammoxidation. Whether Mo oxide is used as the main catalyst or the co-catalyst, most catalysts contain the Mo element. By combining with different elements, Mo-based catalysts obtain different properties.

[0006] The catalyst MoaNibFecBidPreCofCegVhCriAjOk is used in CN105905924A, where A is at least one of lithium, sodium, potassium and rubidium. The catalyst is calcined at 600°C for 10 hours, and the obtained catalyst is evaluated in a fluidized bed, with a methanol conversion rate of >100%, HCN selectivity of >70%, and HCN yield of >70%. However, the catalyst components are too complex and difficult to achieve in the scale-up process.

[0007] US3911089 discloses a catalyst with strong catalytic activity, MoaBibFecXdYeZfOg, where X is one of Cr, Mn, Co, Ni, Zn, Cd, Sn, W and Pb, and Y is one or more of transition elements. The catalyst preparation temperature is 850-900°C, the roasting time is about 6 hours, and it is used for the ammoxidation of methanol, formaldehyde or a mixture of the two to prepare hydrocyanic acid. At a space velocity of 510hr-1, the methanol-ammonia-oxygen ratio is 1:1.1:1.4, and the yield of hydrocyanic acid is 86%. The ammonia-oxygen ratio and the final yield of hydrocyanic acid in this method are not ideal.

[0008] JP54126698 discloses a catalyst AaMoBibFefNanPpOq for preparing hydrocyanic acid by ammoxidation of methanol, where A is selected from potassium, rubidium, and cesium. The document mainly studies the wear resistance of the catalyst, and does not explain the reaction conditions such as the ratio of ammonia to oxygen during the reaction. In this method, the catalyst has a best selectivity of 91.3% and a yield of 90.7% at 420°C and sec1.5s.

[0009] In recent years, there are few studies on the Mo-based catalysts in terms of reducing the hydroxyacetonitrile content in the product and obtaining a higher product yield under low ammonia-oxygen ratio conditions. In addition, the above-mentioned composite catalyst patent literature shows that the composite catalyst combination is complex, and while obtaining multiple functions, there are also many problems. The influence and proportion of each single element in the catalyst in the performance are unclear, and it is difficult to control each component during the preparation process, and it cannot be guaranteed that it is dispersed thoroughly.

[0010] Therefore, it is necessary to improve the methanol ammoxidation catalyst and develop a catalyst with a simple structure and good effect, which can have a higher product yield under a lower ammonia-oxygen ratio and also has good catalytic activity and stability. Summary of the invention

[0011] In view of the above problems existing in the prior art, the present invention provides a methanol ammoxidation catalyst and a preparation method thereof. The catalyst has a simple structure, a large pore structure, and high stability and strength.

[0012] The catalyst is used for preparing hydrocyanic acid and can obtain a higher yield. Even under the condition of a lower ammonia-oxygen ratio, the generation of by-product hydroxyacetonitrile can be effectively reduced, thereby significantly improving the selectivity of hydrocyanic acid.

[0013] To achieve the above object, the present invention adopts the following technical solution:

[0014] The present invention provides a methanol ammoxidation catalyst, wherein the catalyst comprises the following components by mass percentage:

[0015] Carrier 10-90%, preferably 40-85%;

[0016] Molybdenum 2-30%, preferably 4-20%;

[0017] Iron 5-40%, preferably 8-30%;

[0018] 2,2-Bipyridine-5-5-dicarboxylic acid 1-10%, preferably 3-8%.

[0019] In the present invention, the molybdenum and iron exist in the form of metal oxides or iron molybdate.

[0020] In the present invention, the carrier is selected from one or more of cerium dioxide, zirconium dioxide, aluminum oxide, silicon dioxide, cobalt oxide, and titanium dioxide, preferably one or more of cerium dioxide, zirconium dioxide, aluminum oxide, and silicon dioxide.

[0021] In the present invention, the methanol ammoxidation catalyst has a particle size of 5-200 μm, preferably 50-150 μm; a specific surface area of ​​20-200 m 2 / g, preferably 20-70m 2 / g.

[0022] In the present invention, the methanol ammoxidation catalyst has a strength of 30-100 N / M 2 , preferably 50-80N / M 2 .

[0023] The present invention studies the role of each component in the methanol ammoxidation catalyst and finds that Fe is a key component of the catalyst activity. The catalyst without Fe has a very low yield of hydrocyanic acid. The content of Fe in the catalyst has a great influence on the performance of the catalyst. By adjusting the mass ratio of Fe in the catalyst, a catalyst with excellent activity under a low ammonia / methanol ratio can be obtained.

[0024] It was also found that in catalysts containing Fe and Mo, Mo and W can coexist and produce a favorable synergistic effect, and the performance of the catalyst can be significantly improved by adding organic metal additives.

[0025] During the research process, the inventors further discovered that adding 2,2-bipyridine-5-5-dicarboxylic acid macromolecular material to a molybdenum-iron mixed oxide catalyst can fully utilize ammonia in the process of methanol ammoxidation, and a high yield of hydrocyanic acid can be obtained under low ammonia / methanol conditions.

[0026] The mechanism of action of the catalyst can be explained from the catalyst structure. In the oxidation reaction of methanol ammoxidation catalyst, Fe and Mo are the main catalysts. The introduced 2,2-bipyridine-5-5-dicarboxylic acid macromolecular material can increase the specific surface area of ​​the catalyst, increase the internal diffusion phenomenon in the reaction, promote deeper reactions, and make the reaction more thorough.

[0027] The present invention also provides a method for preparing the above-mentioned methanol ammoxidation catalyst, the steps of which include:

[0028] Molybdenum salt and iron salt are dissolved in water, and then 2,2-bipyridine-5-5-dicarboxylic acid is added and mixed evenly, and then acid solution is added to adjust the pH of the system, and then a carrier is added, and the temperature is increased and impregnated under stirring, and then washed with water and calcined to obtain a methanol ammoxidation catalyst.

[0029] In the present invention, the molybdenum salt is selected from one or more of ammonium heptamolybdate, molybdenum chloride, molybdic acid, ammonium octamolybdate, and sodium molybdate, preferably one or more of ammonium heptamolybdate, molybdenum chloride, molybdic acid, ammonium octamolybdate, and sodium molybdate;

[0030] The iron salt is selected from one or more of ferric nitrate, ferric chloride, ferric acetate, and ferric sulfate, preferably one or more of ferric nitrate, ferric chloride, ferric acetate, and ferric sulfate;

[0031] Preferably, the mass ratio of the molybdenum salt, the iron salt and water is 0.01-5:0.01-5:1, preferably 0.1-3:0.1-3:1.

[0032] In the present invention, the mass ratio of the added amount of 2,2-bipyridine-5-5-dicarboxylic acid to water is 0.01-1:1, preferably 0.01-0.1:1.

[0033] In the present invention, the acid solution is added to adjust the pH of the system, and the pH value range is 1-5.5, preferably 1-4;

[0034] The acid solution is an acid aqueous solution with a concentration of 0.1-2 mol / L, preferably 1 mol / L; the acid is selected from HCl, nitric acid, sulfuric acid, acetic acid, formic acid, preferably HCl and nitric acid.

[0035] In the present invention, the carrier is selected from one or more of cerium dioxide, zirconium dioxide, aluminum oxide, silicon dioxide, cobalt oxide, and titanium dioxide, preferably one or more of cerium dioxide, zirconium dioxide, aluminum oxide, and silicon dioxide;

[0036] Preferably, the carrier is a powdery particle with a particle size of 5-200 μm, preferably 10-100 μm;

[0037] Preferably, the mass ratio of the added amount of the carrier to water is 0.5-1:1, preferably 0.5-0.9:1.

[0038] In the present invention, the temperature of the heated immersion is 20-70°C, preferably 20-50°C, and the time is 2-8h, preferably 4-6h.

[0039] In the present invention, the calcination temperature is 300-800°C, preferably 400-750°C, and the time is 2-10h, preferably 3-8h.

[0040] The present invention also provides application of the catalyst in preparing hydrocyanic acid.

[0041] In some embodiments, the present invention provides a method for preparing hydrocyanic acid by ammoxidation of methanol, wherein methanol, oxygen and ammonia are contacted in a fluidized bed in a gas phase under the action of the above-mentioned methanol ammoxidation catalyst to undergo an ammoxidation reaction to produce hydrocyanic acid;

[0042] In the method of the present invention, the molar ratio of oxygen to methanol is 1.0-1.5:1, preferably 1.0-1.2:1;

[0043] The molar ratio of ammonia to methanol is 0.9-1.3:1, preferably 0.9-1.2:1; methanol is in gaseous state.

[0044] In the method of the present invention, the ammoxidation reaction is carried out at a temperature of 400-500°C, preferably 420-480°C, for 0.1-5h, preferably 0.2-3h, and at a slightly positive pressure of 0.01-1Mpa, preferably 0.01-0.5Mpa.

[0045] The ammoxidation reaction is carried out in a fluidized bed, and the methanol space velocity is 0.3-50h -1 , preferably 0.5-30h -1 .

[0046] The method for preparing hydrocyanic acid by methanol ammoxidation of the present invention has a methanol conversion rate of more than 99%, a hydrocyanic acid selectivity of more than 96%, and a by-product hydroxyacetonitrile selectivity of less than 0.05%.

[0047] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0048] The catalyst of the invention has a simple composition and good catalytic activity, has a high hydrocyanic acid yield and high strength, can greatly reduce the generation of hydroxyacetonitrile, reduces the separation cost, and realizes the clean production of preparing hydrocyanic acid by methanol ammoxidation. DETAILED DESCRIPTION

[0049] The specific implementation scheme of the method is further described below in conjunction with examples. However, the present invention is not limited to the listed embodiments, and should also include any other known changes within the scope of the rights claimed by the present invention.

[0050] In the various embodiments and comparative examples of the present invention, the sources of the main raw materials are as follows. Unless otherwise specified, other raw materials and reagents are purchased through common commercial channels:

[0051] 2,2-Bipyridine-5-5-dicarboxylic acid: Shanghai Yuanye Biotechnology Co., Ltd., product number S43804-1;

[0052] Molybdenum chloride: Shanghai Bangcheng Chemical Co., Ltd.;

[0053] Ammonium molybdate: West Asia Chemical Technology (Shandong) Co., Ltd.;

[0054] Ammonium heptamolybdate: Hubei Jusheng Technology Co., Ltd.;

[0055] Ammonium octamolybdate: Wuhan Xinweiye Chemical Co., Ltd.;

[0056] Sodium molybdate: Changzhou Jiaye Chemical Co., Ltd.

[0057] Ferric chloride: Hubei Chengfeng Chemical Co., Ltd.;

[0058] Ferric nitrate: Hubei Chengfeng Chemical Co., Ltd.;

[0059] Ferric acetate: Hubei Chengfeng Chemical Co., Ltd.;

[0060] Ferric sulfate: Hubei Hengjingrui Chemical Co., Ltd.;

[0061] Cerium dioxide carrier powder: Hubei Chengfeng Chemical Co., Ltd.;

[0062] Silica: Hunan Jianghai Environmental Protection Industry Co., Ltd.;

[0063] Zirconium dioxide: Shandong Yukang Chemical Co., Ltd.;

[0064] Alumina: Zhejiang Yamei Nano Technology Co., Ltd.

[0065] The main performance of the embodiments of the present invention is tested by the following methods:

[0066] Particle size, specific surface area: BET specific surface area test method;

[0067] Strength: Catalyst strength testing machine;

[0068] Methanol conversion: Agilent gas chromatography;

[0069] HCN conversion: Potentiometric titrator, using silver nitrate as titrant.

[0070] Example 1

[0071] Preparation of methanol ammoxidation catalyst:

[0072] Weigh 464.69g of molybdenum chloride, 290.44g of ferric chloride, and 500g of deionized water respectively, add them to a 1L autoclave, wait for them to dissolve, add 20g of the macromolecular material 2,2-bipyridine-5-5-dicarboxylic acid, stir thoroughly for 4h, adjust the pH value of the stirred mixed solution to about 4 with 1mol / L hydrochloric acid, and add 325g of cerium dioxide carrier powder (diameter 70-100μm). The obtained solution is heated and stirred at 70°C for 4h. Then cool to room temperature, wash the obtained mixture with deionized water, and filter to obtain an orange powder. The powder is calcined at 400°C for 3h to obtain a methanol ammoxidation catalyst.

[0073] The mass percentage composition of the prepared catalyst is: 61.34% of cerium dioxide carrier, 14.03% of molybdenum, 18.91% of iron, and 3.67% of 2,2-bipyridine-5-5-dicarboxylic acid, wherein molybdenum and iron mainly exist in the form of iron molybdate, containing a small amount of molybdenum oxide and iron oxide.

[0074] The catalyst particle size is 104 μm and the specific surface area is 53.65 m 2 / g, strength 58N / M 2 .

[0075] Using the above catalyst, hydrogen cyanide is prepared by ammoxidation of methanol:

[0076] A fluidized bed reactor was used with a reactor diameter of 20 mm, a catalyst loading of 10 g, a reaction pressure of 0.02 MPa, a reaction temperature of 400 °C, and a methanol space velocity of 1 h -1 In the raw gas, the molar ratio of oxygen to methanol is 1.2:1, the molar ratio of ammonia to methanol is 1.1:1, the reaction residence time is 0.4h, and sampling and testing are carried out 3h after the reaction. The results are shown in Table 1.

[0077] After the reaction was run for 1000 h, samples were taken again for testing to compare the stability. The results are shown in Table 1.

[0078] Example 2

[0079] Preparation of methanol ammoxidation catalyst:

[0080] Weigh 1685.26g of ammonium molybdate, 868.12g of ferric nitrate, and 600g of deionized water respectively, add them to a 1L high-pressure reactor, wait for them to dissolve, add 30g of the macromolecular material 2,2-bipyridine-5-5-dicarboxylic acid, stir thoroughly for 5h, adjust the pH value of the stirred mixed solution to about 3.5 with 1mol / L hydrochloric acid, and add 420g of zirconium dioxide carrier powder (diameter 50-80μm). The above solution was heated and stirred at 45°C and the immersion time was 5.5h. Then cool to room temperature, wash the resulting mixture with deionized water, and filter to obtain an orange powder. The powder was calcined at 500°C for 4h to obtain a methanol ammoxidation catalyst.

[0081] The mass percentage composition of the prepared catalyst is: 66.21% of cerium dioxide carrier, 9.49% of molybdenum, 18.73% of iron, and 4.25% of 2,2-bipyridine-5-5-dicarboxylic acid, wherein molybdenum and iron mainly exist in the form of iron molybdate, containing a small amount of molybdenum oxide and iron oxide.

[0082] The catalyst particle size is 110 μm and the specific surface area is 32.63 m 2 / g, strength 56N / M 2 .

[0083] Using the above catalyst, hydrogen cyanide is prepared by ammoxidation of methanol:

[0084] A fluidized bed reactor was used with a reactor diameter of 20 mm, a catalyst loading of 10 g, a reaction pressure of 0.03 MPa, a reaction temperature of 420 °C, and a methanol space velocity of 5 h -1 In the raw gas, the molar ratio of oxygen to methanol is 1.2:1, the molar ratio of ammonia to methanol is 1.2:1, the reaction residence time is 0.1h, and sampling and testing are carried out 3h after the reaction. The results are shown in Table 1.

[0085] Example 3

[0086] Preparation of methanol ammoxidation catalyst:

[0087] Weigh 2247.02g of ammonium heptamolybdate, 1736.23g of ferric nitrate, and 800g of deionized water respectively, add them to a 1.5L high-pressure reactor, wait for them to dissolve, add 35g of the macromolecular material 2,2-bipyridine-5-5-dicarboxylic acid, stir thoroughly for 6h, use 1mol / L hydrochloric acid to adjust the pH value of the stirred mixed solution to about 3, and add 480g of zirconium dioxide carrier powder (diameter 50-100μm). The above solution was heated and stirred at 50°C and the immersion time was 6h. Then cool to room temperature, wash the resulting mixture with deionized water, and filter to obtain an orange powder. The powder was calcined at 550°C for 5h to obtain a methanol ammoxidation catalyst.

[0088] The mass percentage composition of the prepared catalyst is: 57.15% of cerium dioxide carrier, 9.06% of molybdenum, 27.39% of iron, and 4.01% of 2,2-bipyridine-5-5-dicarboxylic acid, wherein molybdenum and iron mainly exist in the form of iron molybdate, containing a small amount of molybdenum oxide and iron oxide.

[0089] The catalyst particle size is 120 μm and the specific surface area is 37.63 m 2 / g, strength is 53N / M 2 .

[0090] Using the above catalyst, hydrogen cyanide is prepared by ammoxidation of methanol:

[0091] The fluidized bed reactor was used, with a reactor diameter of 20 mm, a catalyst loading of 10 g, a reaction pressure of 0.03 MPa, a reaction temperature of 450 °C, and a methanol space velocity of 0.7 h -1 In the raw gas, the molar ratio of oxygen to methanol is 1.1:1, the molar ratio of ammonia to methanol is 1.2:1, the reaction residence time is 0.5h, and sampling and testing are carried out 3h after the reaction. The results are shown in Table 1.

[0092] Example 4

[0093] Preparation of methanol ammoxidation catalyst:

[0094] Weigh 856.24g of ammonium octamolybdate, 186.87g of ferric nitrate, and 3100g of deionized water respectively, add them to a 5L enamel reactor, wait for them to dissolve, add 10g of the macromolecular material 2,2-bipyridine-5-5-dicarboxylic acid, stir thoroughly for 7h, use 1mol / L hydrochloric acid to adjust the pH value of the stirred mixed solution to about 3, and add 510g of zirconium dioxide carrier powder (diameter 40-60μm). The above solution was heated and stirred at 45°C and the immersion time was 4h. Then cool to room temperature, wash the resulting mixture with deionized water, and filter to obtain an orange powder. The powder was calcined at 600°C for 6h to obtain a methanol ammoxidation catalyst.

[0095] The mass percentage composition of the prepared catalyst is: 81.73% of cerium dioxide carrier, 4.38% of molybdenum, 9.17% of iron, and 1.28% of 2,2-bipyridine-5-5-dicarboxylic acid, wherein molybdenum and iron mainly exist in the form of iron molybdate, containing a small amount of molybdenum oxide and iron oxide.

[0096] The catalyst particle size is 76 μm and the specific surface area is 53.46 m 2 / g, strength is 87N / M 2 .

[0097] Using the above catalyst, hydrogen cyanide is prepared by ammoxidation of methanol:

[0098] The fluidized bed reactor was used, with a reactor diameter of 20 mm, a catalyst loading of 10 g, a reaction pressure of 0.05 MPa, a reaction temperature of 500 °C, and a methanol space velocity of 0.5 h -1 In the raw gas, the molar ratio of oxygen to methanol is 1.1:1, the molar ratio of ammonia to methanol is 1.2:1, the reaction residence time is 0.6h, and sampling and testing are carried out 3h after the reaction. The results are shown in Table 1.

[0099] Example 5

[0100] Preparation of methanol ammoxidation catalyst:

[0101] Weigh 441.68g of ammonium molybdate, 326.42g of ferric nitrate, and 2500g of deionized water respectively, add them to a 5L enamel reactor, wait for them to dissolve, add 50g of the macromolecular material 2,2-bipyridine-5-5-dicarboxylic acid, stir thoroughly for 8h, use 1mol / L hydrochloric acid to adjust the pH value of the stirred mixed solution to about 3, and add 560g of zirconium dioxide carrier powder (diameter 30-60μm). The above solution was heated and stirred at 30°C and the immersion time was 6h. Then cool to room temperature, wash the resulting mixture with deionized water, and filter to obtain an orange powder. The powder was calcined at 650°C for 7h to obtain a methanol ammoxidation catalyst.

[0102] The mass percentage composition of the prepared catalyst is: 64.13% of cerium dioxide carrier, 13.62% of molybdenum, 13.52% of iron, and 5.24% of 2,2-bipyridine-5-5-dicarboxylic acid, wherein molybdenum and iron mainly exist in the form of iron molybdate, containing a small amount of molybdenum oxide and iron oxide.

[0103] The catalyst particle size is 97 μm and the specific surface area is 94.91 m 2 / g, strength is 69N / M 2 .

[0104] Using the above catalyst, hydrogen cyanide is prepared by ammoxidation of methanol:

[0105] A fluidized bed reactor was used with a reactor diameter of 20 mm, a catalyst loading of 10 g, a reaction pressure of 0.01 MPa, a reaction temperature of 500 °C, and a methanol space velocity of 4 h -1 In the raw gas, the molar ratio of oxygen to methanol is 1.1:1, the molar ratio of ammonia to methanol is 1.2:1, the reaction residence time is 0.05h, and sampling is carried out 3h after the reaction. The results are shown in Table 1.

[0106] Example 6

[0107] Preparation of methanol ammoxidation catalyst:

[0108] Weigh 1099.62g of sodium molybdate, 2170.29g of ferric nitrate, and 2000g of deionized water respectively, add them to a 5L enamel reactor, wait for them to dissolve, add 70g of the macromolecular material 2,2-bipyridine-5-5-dicarboxylic acid, stir thoroughly for 6h, adjust the pH value of the stirred mixed solution to about 3 with 1mol / L hydrochloric acid, and add 500g of zirconium dioxide carrier powder (diameter 60-100μm). The above solution was heated and stirred at 20°C and the immersion time was 6h. Then cool to room temperature, wash the resulting mixture with deionized water, and filter to obtain an orange powder. The powder was calcined at 700°C for 8h to obtain a methanol ammoxidation catalyst.

[0109] The mass percentage composition of the prepared catalyst is: 45.30% of cerium dioxide carrier, 17.41% of molybdenum, 26.91% of iron, and 5.95% of 2,2-bipyridine-5-5-dicarboxylic acid, wherein molybdenum and iron mainly exist in the form of iron molybdate, and contain a small amount of molybdenum oxide and iron oxide.

[0110] The catalyst particle size is 121 μm and the specific surface area is 91.47 m 2 / g, strength is 69N / M 2 .

[0111] Using the above catalyst, hydrogen cyanide is prepared by ammoxidation of methanol:

[0112] A fluidized bed reactor was used with a reactor diameter of 20 mm, a catalyst loading of 10 g, a reaction pressure of 0.15 MPa, a reaction temperature of 450 °C, and a methanol space velocity of 1 h -1 In the raw gas, the molar ratio of oxygen to methanol is 1.1:1, the molar ratio of ammonia to methanol is 1.2:1, the reaction residence time is 0.2h, and sampling and testing are carried out 3h after the reaction. The results are shown in Table 1.

[0113] Comparative Example 1

[0114] The method of Example 1 was used with the exception that 2,2-bipyridine-5-5-dicarboxylic acid was not added during the preparation of the catalyst, and other operations and conditions remained unchanged. The results are shown in Table 1.

[0115] Comparative Example 2

[0116] The method of Example 1 was used with the exception that no molybdenum salt was added during the preparation of the catalyst, and other operations and conditions remained unchanged. The results are shown in Table 1.

[0117] Comparative Example 3

[0118] The method of Example 1 is referred to, except that the molybdenum salt is replaced by tungstate when preparing the catalyst, and other operations and conditions remain unchanged. The results are shown in Table 1.

[0119] Comparative Example 4

[0120] The method of Example 1 was used with the exception that no iron salt was added during the preparation of the catalyst, and other operations and conditions remained unchanged. The results are shown in Table 1.

[0121] Comparative Example 5

[0122] The method of Example 1 was used with the exception that bismuth chloride was used to replace ferric chloride when preparing the catalyst, and other operations and conditions remained unchanged. The results are shown in Table 1.

[0123] Comparative Example 6

[0124] The method of Example 1 was used with the exception that acid was not used to adjust the pH value of the system during the preparation of the catalyst, and other operations and conditions remained unchanged. The results are shown in Table 1.

[0125] Table 1 Table 2 Catalyst evaluation results

[0126] Methanol conversion rate Hydroxyacetonitrile selectivity HCN selectivity Example 1 99.81％ 0.01％ 96.17％ Example 1 (1000h) 99.76％ 0.01％ 96.03％ Example 2 99.63％ 0.01％ 97.32％ Example 3 99.64％ 0.02％ 96.85％ Example 4 99.55％ 0.01％ 96.57％ Example 5 99.77％ 0.01％ 97.13％ Example 6 99.52％ 0.02％ 97.62％ Comparative Example 1 90.59％ 0.34％ 86.54％ Comparative Example 2 80.35％ 0.13％ 1.32％ Comparative Example 3 81.65％ 0.15％ 0.03％ Comparative Example 4 80.94％ 0.24％ 1.29％ Comparative Example 5 83.76％ 0.37％ 7.75％ Comparative Example 6 81.56％ 0.03％ 84.94％

[0127] It can be seen from Table 1 and Table 2 that Examples 1 to 6 all have good activity and selectivity, while the catalysts described in Comparative Examples 1 to 3 have low activity or poor selectivity or poor strength.

[0128] By comparing Example 1 with Comparative Example 1, it can be seen that adding macromolecular materials to the catalyst can significantly improve the activity of the catalyst. This is because the macromolecular materials can form a larger pore structure in the catalyst, and the porous structure can promote the internal diffusion of the reaction, and the active sites can be better exposed to the reactants, thereby promoting the reaction.

[0129] By comparing Example 3 with Comparative Example 6, adjusting the pH value can effectively promote the formation of active sites, which is helpful to improve the performance of the catalyst.

[0130] The above results show that the catalyst prepared by the method of the present invention has more active components, better mass transfer performance, more thorough reaction, and can effectively promote the formation of HCN and reduce the content of by-product hydroxyacetonitrile.

Claims

1. A method for preparing a methanol ammoxidation catalyst, It is characterized in that the steps include: The molybdenum salt and the iron salt are dissolved in water, and then 2,2-bipyridine-5,5-dicarboxylic acid is added and mixed evenly, and then an acid solution is added to adjust the pH of the system, and then a carrier is added, and the mixture is heated and impregnated under stirring, and then washed with water and calcined to obtain a methanol ammoxidation catalyst; The carrier is selected from one or more of cerium dioxide, zirconium dioxide, aluminum oxide, silicon dioxide, cobalt oxide, and titanium dioxide; The molybdenum salt is selected from one or more of ammonium heptamolybdate, molybdenum chloride, molybdic acid, ammonium octamolybdate, and sodium molybdate; The iron salt is selected from one or more of ferric nitrate, ferric chloride, ferric acetate and ferric sulfate; The mass ratio of the molybdenum salt, the iron salt and water is 0.01-5:0.01-5:1; The mass ratio of the added amount of 2,2-bipyridine-5,5-dicarboxylic acid to water is 0.01-1:

1.

2. The preparation method according to claim 1, It is characterized in that The mass ratio of the molybdenum salt, the iron salt and water is 0.1-3:0.1-3:1; The mass ratio of the added amount of 2,2-bipyridine-5,5-dicarboxylic acid to water is 0.01-0.1:

1.

3. The preparation method according to claim 1, It is characterized in that The acid solution is added to adjust the pH of the system, and the pH value range is 1-5.5; The acid solution is an acid aqueous solution with a concentration of 0.1-2 mol / L; the acid is selected from HCl, nitric acid, sulfuric acid, acetic acid, and formic acid; The carrier is selected from one or more of cerium dioxide, zirconium dioxide, aluminum oxide, silicon dioxide, cobalt oxide, and titanium dioxide.

4. The preparation method according to claim 3, It is characterized in that The acid solution is added to adjust the pH of the system, and the pH value range is 1-4; The acid solution is an acid aqueous solution with a concentration of 0.1-2 mol / L.

5. The preparation method according to claim 1, It is characterized in that The carrier is powdery particles with a particle size of 5-200 μm.

6. The preparation method according to claim 5, It is characterized in that The carrier is powdery particles with a particle size of 10-100 μm.

7. The preparation method according to claim 1, It is characterized in that The mass ratio of the added amount of the carrier to water is 0.5-1:

1.

8. The preparation method according to claim 7, It is characterized in that The mass ratio of the added amount of the carrier to water is 0.5-0.9:

1.

9. The preparation method according to claim 1, It is characterized in that The temperature of the soaking is 20-70°C and the time is 2-8h; The calcination temperature is 300-800° C. and the time is 2-10 hours.

10. The preparation method according to claim 9, It is characterized in that The temperature of the heated immersion is 20-50° C. and the time is 4-6 hours.

11. The preparation method according to claim 9, It is characterized in that The calcination temperature is 400-750° C. and the time is 3-8 hours.

12. A method for preparing hydrocyanic acid by ammoxidation of methanol, It is characterized in that The method comprises the following steps: methanol, oxygen and ammonia are contacted in a fluidized bed in a gas phase under the action of a methanol ammoxidation catalyst prepared by the method according to any one of claims 1 to 11 to produce hydrogen cyanide by ammoxidation reaction.

13. The method according to claim 12, It is characterized in that The molar ratio of oxygen to methanol is 1.0-1.5:1; The molar ratio of ammonia to methanol is 0.9-1.3:1; methanol is in gaseous state; The ammoxidation reaction is carried out at a temperature of 400-500°C, a time of 0.1-5h, and a reaction pressure of 0.01-1Mpa; The ammoxidation reaction is carried out in a fluidized bed, and the methanol space velocity is 0.3-50h -1 .

14. The method according to claim 13, It is characterized in that The molar ratio of oxygen to methanol is 1.0-1.2:1; The molar ratio of ammonia to methanol is 0.9-1.2:

1.

15. The method according to claim 13, It is characterized in that The ammoxidation reaction has a temperature of 420-480°C, a time of 0.2-3h, and a reaction pressure of 0.01-0.5Mpa.

16. The method according to claim 13, It is characterized in that The methanol space velocity is 0.5-30h -1 .