Hydrocyanic acid catalyst for fluidized-bed synthesis, its preparation and use

Abstract

The application provides a fluidized bed synthesis hydrocyanic acid catalyst and a preparation method and application thereof, and comprises the following steps: mixing silica sol, polyacrylamide and ammonia water to obtain a carrier solution; dissolving molybdenum salt into water, adding acid to adjust pH, and heating to obtain an A solution; then dissolving bismuth salt, iron salt, nickel salt, manganese salt, magnesium salt, praseodymium salt and zirconium salt into water, heating to obtain a B solution, adding the B solution into the A solution to mix and age, and obtaining an active solution; mixing the carrier solution and the active solution, beating, crystallizing, aging, drying and calcining to obtain the hydrocyanic acid catalyst. The application adjusts the pH of the carrier solution by using ammonia water, so that the carrier particle distribution of the carrier solution is more uniform, the catalyst stability is improved, the abrasion resistance of the catalyst is increased by using the agglomeration performance of the polyacrylamide, the catalyst pore diameter can be enlarged, and the catalytic reaction efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of hydrogen cyanide catalyst technology, specifically to a catalyst for fluidized bed synthesis of hydrogen cyanide, its preparation method, and its application. Background Technology

[0002] Hydrogen cyanide is an important chemical, widely used in the synthesis of fine chemical intermediates due to its reactive properties, and has important applications in pharmaceuticals, metallurgy, electroplating, pesticides, and dyes. The production methods of hydrogen cyanide are mainly divided into two categories: direct synthesis and acrylonitrile by-product methods. Direct synthesis methods are further divided into four types: the Angle process, the BMA process, the light oil cracking process, and the methanol ammoxidation process. Among these, the Angle process, the BMA process, and the light oil cracking process use natural gas or light oil as raw materials and require high temperatures. The acrylonitrile by-product method involves the ammoxidation of propylene with propylene to produce acrylonitrile, yielding HCN as a by-product. With continuous advancements in propylene ammoxidation technology, the amount of hydrogen cyanide as a by-product has gradually decreased. The methanol ammoxidation process, originating from coal chemical processes, is more in line with China's energy structure, offering advantages such as inexpensive and readily available raw materials, low reaction temperatures, and high yields, thus possessing broad development prospects.

[0003] Currently, foreign patent reports on methanol ammoxidation catalysts for hydrogen cyanide production mainly fall into four categories: Mo-based, Sb-based, Mn-based, and BP oxide. In the late 1980s, the Changchun Institute of Applied Chemistry in my country also conducted research on Mo-Fe metal oxide catalysts for methanol ammoxidation to hydrogen cyanide. Current catalyst development mainly focuses on Fe-Mo oxide catalysts, Mn-P oxide catalysts, PV oxide catalysts, and Pt-Rh alloy catalysts. Chinese patents CN 101715369A and CN105905924A summarize in detail the characteristics of methanol ammoxidation reaction on composite oxide catalysts, with most catalysts showing high hydrogen cyanide yields. Furthermore, CN105905924A provides a comparison of application effects in fixed-bed and fluidized-bed reactors, but does not provide the catalyst preparation method.

[0004] Currently, some regions in China have methanol-to-hydrogen cyanide (Hcyanate) plants with capacities of tens of thousands of tons, but these all use tubular reactors. During actual use, the catalyst exhibits significant hot spots and a wide temperature range, making the active component Mo prone to sublimation and loss, leading to catalyst lifespan degradation. The Hcyanate yield drops significantly in the initial and final stages of plant operation, necessitating periodic shutdowns for catalyst replacement. Furthermore, the temperature distribution makes operation and control difficult, resulting in large fluctuations in Hcyanate yield and high levels of byproduct carbon dioxide. Adopting a fluidized bed reaction process with the catalyst in a fluidized state could completely solve the hot spot problem, resulting in more uniform reaction temperature, reduced Mo sublimation and loss, increased catalyst lifespan, reduced yield fluctuations, and lower byproduct carbon dioxide content. Simultaneously, the catalyst can be replenished online, extending the plant's operating cycle. However, existing catalysts have low mechanical strength, and their wear resistance index does not meet the requirements of fluidized bed reaction processes. Therefore, developing catalysts with excellent wear resistance and high yield is crucial.

[0005] Existing catalyst preparation methods mostly employ co-precipitation, where a salt solution is directly added dropwise to a molybdenum salt solution and dried to obtain the catalyst. As a result, the existing catalysts lack sufficient mechanical strength and wear resistance, failing to meet the specific requirements of fluidized bed processes. Summary of the Invention

[0006] The technical problem to be solved by this invention is how to improve the mechanical strength of hydrogen cyanide catalysts.

[0007] The present invention solves the above-mentioned technical problems through the following technical means:

[0008] The first aspect of this invention provides a method for preparing a catalyst for the fluidized bed synthesis of hydrogen cyanide, comprising the following steps: S1 mixes silica sol, polyacrylamide, and ammonia to obtain a carrier solution; S2 dissolves molybdenum salt in water and adds acid to adjust the pH to obtain solution A; then dissolves bismuth salt, iron salt, nickel salt, manganese salt, magnesium salt, praseodymium salt and zirconium salt in water and mixes them to obtain solution B. Solution B is added to solution A for mixing and aging to obtain an active solution. S3 involves mixing the support solution and the active solution, crystallizing and aging them, drying them, and calcining them to obtain a hydrogen cyanide catalyst.

[0009] The active component of the hydrogen cyanide catalyst has the structural formula Mo6Bi. a Fe b Ni c Mn d Mg e Pr f Zr h O n, a, b, c, d, e, f and g represent atomic ratios relative to Mo, wherein the value of a ranges from 0.8 < a < 1.5; the value of b ranges from 1.5 < b < 3.0; the value of c ranges from 1.2 < c < 4.5; the value of d ranges from 1.5 < d < 2.5; the value of e ranges from 0.8 < e < 1.2; the value of f ranges from 1.2 < f < 2.5; the value of g ranges from 0.8 < g < 1.3; and n is the total number of oxygen atoms required to satisfy the valence of other elements.

[0010] Advantageous effects: In the present invention, silica sol is mixed with polyacrylamide and ammonia water, and ammonia water is used to adjust the pH of the carrier solution, so that silica particles in the carrier solution are more uniformly distributed, which improves the stability of the catalyst. The agglomeration property of polyacrylamide is utilized, which can increase the wear resistance of the catalyst, also expand the pore size of the catalyst and improve the catalytic reaction efficiency. After calcination, the catalyst prepared by the present invention has a carrier of silica. The silica is uniformly distributed, and its framework structure can improve the wear resistance of the catalyst. In addition, silica can form a synergistic effect with active components to improve the catalytic performance of the catalyst. The preparation method of the present invention is simple in operation and easy for production.

[0011] Preferably, the mass concentration of the ammonia water is 10-20%, and the weight ratio of the silica sol: polyacrylamide: ammonia water is 1:0.01 0.9:0.01-0.2.

[0012] Preferably, step S1 is carried out at a temperature of 25-90°C.

[0013] Preferably, the acid in step S2 is nitric acid, having a mass concentration of 65-69%, and the pH is adjusted to 2.0-4.0.

[0014] Preferably, in step S2, aging is carried out at a temperature of 50-80°C, and the aging time is 10-14h.

[0015] Preferably, the temperature for mixing and beating in step S3 is 25-90°C, and crystallization and aging are performed at a temperature of 50-100°C for 10-14h.

[0016] Preferably, the calcination temperature in step S3 is 350-700°C.

[0017] Preferably, the carrier accounts for 30-60% of the total weight of the catalyst.

[0018] In a second aspect of the present invention, a hydrocyanic acid catalyst is prepared by the preparation method of the above catalyst for fluidized bed synthesis of hydrocyanic acid.

[0019] The third aspect of this invention provides the application of the above-mentioned method for preparing a catalyst for the synthesis of hydrogen cyanide in a fluidized bed, wherein the hydrogen cyanide catalyst is reacted in a fluidized bed to generate hydrogen cyanide, and the reaction temperature is 350-400℃.

[0020] Beneficial effects: This invention introduces multiple auxiliary metals into the MoBiFeNi-based catalyst. Through different metal interactions, it is suitable for fluidized bed reactors, reduces reaction temperature, reduces the loss of molybdenum in the catalyst, and produces fewer byproducts such as carbon dioxide. While improving the yield of hydrogen cyanide, it also improves the shortcomings of fixed-bed reaction processes. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0023] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0024] Example 1 This embodiment provides a catalyst for fluidized bed synthesis of hydrogen cyanide and its preparation method, the specific steps of which are as follows: S1. Add 200g of silica sol and 20g of polyacrylamide to a 1000mL round-bottom flask, add 400g of deionized water, stir at 25℃ for 2h, then add 12g of 20% ammonia water, gradually raise the temperature to 50℃, stir at this temperature for 1h to obtain the carrier solution.

[0025] S2 dissolves 100g of ammonium heptamolybdate in 500ml of deionized water at 50℃, then adds 68% concentrated nitric acid to adjust the pH of the solution to 2.5, thus obtaining solution A.

[0026] 22g bismuth nitrate, 40g ferric nitrate, 56g nickel nitrate, 11g manganese nitrate, 7.9g magnesium nitrate, 8.8g praseodymium nitrate, and 9.2g zirconium nitrate were dissolved in 500ml of deionized water at 50℃ to obtain solution B. Solution B was then added dropwise to solution A under vigorous stirring to mix the solutions. The mixture was then aged at 65℃ for 12 hours to obtain the active solution.

[0027] S3 mixed the support solution and active solution at 70℃ and then transferred them to an enamel crystallization kettle for crystallization and aging at 90℃ for 12 hours. After crystallization and aging, the mixture was spray-dried at 350℃ and then calcined at 400℃ for 4 hours to obtain a hydrogen cyanide catalyst with a support weight accounting for 40% of the total catalyst weight. Based on the molar ratio of the metal salt cations, the structural formula of the active component of the hydrogen cyanide catalyst was derived as: Mo6Bi 0.94 Fe 1.98 Ni 2.47 Mn 2.43 Mg 0.95 Pr 1.24 Zr 1.05 On.

[0028] Example 2 This embodiment provides a catalyst for the fluidized bed synthesis of hydrogen cyanide and its preparation method. The difference between this embodiment and Embodiment 1 is that the support solution is as follows: 200g of silica sol and 10g of polyacrylamide are added to a 1000mL round-bottom flask, 400g of deionized water is added, and the mixture is stirred at 25°C for 2 hours. Then, 12g of 20% ammonia solution is added, and the temperature is gradually increased to 50°C. The mixture is stirred at this temperature for 1 hour to obtain the support solution.

[0029] Example 3 This embodiment provides a catalyst for the fluidized bed synthesis of hydrogen cyanide and its preparation method. The difference between this embodiment and Embodiment 1 is that the support solution is as follows: 200g of silica sol and 40g of polyacrylamide are added to a 1000mL round-bottom flask, 400g of deionized water is added, and the mixture is stirred at 25°C for 2 hours. Then, 12g of 20% ammonia solution is added, and the temperature is gradually increased to 50°C. The mixture is stirred at this temperature for 1 hour to obtain the support solution.

[0030] Example 4 This embodiment provides a catalyst for the fluidized bed synthesis of hydrogen cyanide and its preparation method. The difference between this embodiment and Embodiment 1 is that the support solution is as follows: 200g of silica sol and 40g of polyacrylamide are added to a 1000mL round-bottom flask, 400g of deionized water is added, and the mixture is stirred at 25°C for 2 hours. Then, 30g of 20% ammonia solution is added, and the temperature is gradually raised to 50°C. The mixture is stirred at this temperature for 1 hour to obtain the support solution.

[0031] Example 5 This embodiment provides a catalyst for the fluidized bed synthesis of hydrogen cyanide and its preparation method. The difference between this embodiment and Embodiment 1 is that the support solution is as follows: 200g of silica sol and 40g of polyacrylamide are added to a 1000mL round-bottom flask, 400g of deionized water is added, and the mixture is stirred at 25°C for 2 hours. Then, 20g of 20% ammonia solution is added, and the temperature is gradually increased to 50°C. The mixture is stirred at this temperature for 1 hour to obtain the support solution.

[0032] Example 6 This embodiment provides a catalyst for the fluidized bed synthesis of hydrogen cyanide and its preparation method. The difference between this embodiment and Embodiment 1 is that the support solution is as follows: 200g of silica sol and 40g of polyacrylamide are added to a 1000mL round-bottom flask, 400g of deionized water is added, and the mixture is stirred at 25°C for 2 hours. Then, 8g of 20% ammonia solution is added, and the temperature is gradually increased to 50°C. The mixture is stirred at this temperature for 1 hour to obtain the support solution.

[0033] Example 7 This embodiment provides a catalyst for fluidized bed synthesis of hydrogen cyanide and its preparation method, specifically including the following steps: S1. Add 200g of silica sol and 20g of polyacrylamide to a 1000mL round-bottom flask, add 400g of deionized water, stir at 25℃ for 2h, then add 12g of 20% ammonia water, gradually raise the temperature to 50℃, stir at this temperature for 1h to obtain the carrier solution.

[0034] S2 dissolves 84g of ammonium heptamolybdate in 500ml of deionized water at 50℃, then adds 68% concentrated nitric acid to adjust the pH of the solution to 2.5, thus obtaining solution A.

[0035] 18.3g bismuth nitrate, 33.3g ferric nitrate, 46.7g nickel nitrate, 9.2g manganese nitrate, 6.6g magnesium nitrate, 7.3g praseodymium nitrate, and 7.7g zirconium nitrate were dissolved in 500ml of deionized water at 50℃ to obtain solution B. Solution B was added dropwise to solution A under vigorous stirring and then aged at 70℃ for 12 hours to obtain the active solution.

[0036] S3 mixed the support solution and active component solution at 70℃ and then transferred them to an enamel crystallization kettle for crystallization and aging at 90℃ for 12 hours. After crystallization and aging, the mixture was spray-dried at 350℃ and then calcined at 400℃ for 4 hours to obtain a catalyst in which the support weight accounted for 50% of the total catalyst weight. Based on the molar ratio of the metal salt cations, the structural formula of the active component of the catalyst was derived: Mo6Bi 0.94 Fe 1.98 Ni 2.47 Mn 2.43 Mg0.95 Pr 1.24 Zr 1.05 On.

[0037] Comparative Example 1 This comparative example provides a hydrogen cyanide catalyst and its preparation method. The difference between this comparative example and Example 1 is that no support solution was prepared.

[0038] Comparative Example 2 This comparative example provides a hydrogen cyanide catalyst and its preparation method. The difference between this comparative example and Example 1 is that the support solution is only silica sol.

[0039] Comparative Example 3 This comparative example provides a hydrogen cyanide catalyst and its preparation method. The difference between this comparative example and Example 1 is that no ammonia was added to the support solution.

[0040] Comparative Example 4 This comparative example provides a hydrogen cyanide catalyst and its preparation method. The difference between this comparative example and Example 1 is that no polyacrylamide was added to the support solution.

[0041] Comparative Example 5 This comparative example provides a hydrogen cyanide catalyst and its preparation method. The difference between this comparative example and Example 1 is that the support is only alumina.

[0042] Comparative Example 6 This comparative example provides a hydrogen cyanide catalyst and its preparation method. The difference between this comparative example and Example 1 is that the silica sol in Example 1 is replaced with alumina.

[0043] Comparative Example 7 This comparative example provides a hydrogen cyanide catalyst and its preparation method. The difference between this comparative example and Example 1 is that the weight of the support accounts for 80% of the total weight of the catalyst.

[0044] Comparative Example 8 This comparative example provides a hydrogen cyanide catalyst and its preparation method. The difference between this comparative example and Example 1 is that the weight of the support accounts for 20% of the total weight of the catalyst.

[0045] Experimental Example The hydrogen cyanide catalysts prepared in Examples 1-12 and Comparative Examples 1-6 were evaluated in a fluidized bed reactor for the synthesis of hydrogen cyanide from methanol via ammonia oxidation. The catalyst performance evaluation is shown in Table 1. The evaluation conditions for catalyst conversion, selectivity, etc., were as follows: fluidized bed reactor, inner diameter 150 mm; catalyst loading: 500 g; reaction pressure: 55 kPa; reaction temperature: 390 °C; contact time: 8 s; feed gas composition (volume ratio): methanol:ammonia:air = 1:1.03:11.5; space velocity: 2500 h⁻¹ -1 The gaseous products of the reaction were absorbed by sodium hydroxide solution and then titrated with silver nitrate.

[0046] The definitions of methanol conversion, hydrogen cyanide yield, selectivity, and carbon dioxide yield are as follows: Methanol conversion rate (%) = (moles of hydrogen cyanide produced in the reaction + moles of carbon dioxide produced in the reaction / moles of methanol entering the reactor) × 100%.

[0047] Hydrogen cyanide yield (%) = (moles of hydrogen cyanide produced / moles of methanol entering the reactor) × 100%.

[0048] Hydrogen cyanide selectivity (%) = (number of carbon moles of hydrogen cyanide produced / total number of carbon moles of all products) × 100%.

[0049] Carbon dioxide yield (%) = (moles of carbon dioxide produced / moles of methanol entering the reactor) × 100%.

[0050] The hydrogen cyanide catalysts prepared in Examples 1-12 and Comparative Examples 1-6 were placed in an apparatus for measuring the wear index and purged with a gas flow of 15 L / min for 5 hours. Samples smaller than 20 micrometers purged in the first hour were discarded. Samples purged in the following 4 hours were collected, and the average wear percentage per hour was calculated, which is called the catalyst wear index: f = m / 50 g / 4 h, where m is the mass of the sample purged in the following 4 hours. Specific data are shown in Table 1.

[0051] Table 1 Catalyst Performance Evaluation

[0052] As shown in Table 1, the hydrogen cyanide catalysts prepared in Examples 1-7, compared with those prepared in Comparative Example 1, not only showed a significant improvement in the attrition index, but also exhibited correspondingly improved catalytic performance.

[0053] As shown in Comparative Examples 1-4, if any one of the three components of the carrier solution—silica sol, polyacrylamide, and ammonia—is missing, the wear index of the hydrogen cyanide catalyst will decrease significantly, and the catalytic performance of the catalyst will also decrease accordingly.

[0054] As can be seen from Comparative Examples 5-6, when silica sol is replaced with a similar support, alumina, the wear index of the hydrogen cyanide catalyst will decrease accordingly, and it will not be able to reach the wear index of the examples.

[0055] As can be seen from Examples 7-8, the wear index cannot reach the wear index of the Examples when the carrier weight accounts for 30-60% of the total catalyst weight.

[0056] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a catalyst for the fluidized bed synthesis of hydrogen cyanide, characterized in that, Includes the following steps: S1 mixes silica sol, polyacrylamide, and ammonia to obtain a carrier solution; S2 dissolves molybdenum salt in water and adds acid to adjust the pH to obtain solution A; then dissolves bismuth salt, iron salt, nickel salt, manganese salt, magnesium salt, praseodymium salt and zirconium salt in water and mixes them to obtain solution B. Solution B is added to solution A for mixing and aging to obtain an active solution. S3 involves mixing and pulping the support solution and the active solution, crystallizing and aging, drying and calcining to obtain a hydrogen cyanide catalyst. The structural formula of the active component of the hydrocyanic acid catalyst is Mo₆Bi a Fe b Ni c Mn d Mg e Pr f Zr h O n , wherein a, b, c, d, e, f and g represent atomic ratios relative to Mo, the value range of a is 0.8 < a < 1.5; the value range of b is 1.5 < b < 3.0; the value range of c is 1.2 < c < 4.5; the value range of d is 1.5 < d < 2.5; the value range of e is 0.8 < e < 1.2; the value range of f is 1.2 < f < 2.5; the value range of g is 0.8 < g < 1.3; and n is the total number of oxygen atoms required to satisfy the valence of other elements.

2. The method for preparing the catalyst for fluidized bed synthesis of hydrogen cyanide according to claim 1, characterized in that, The ammonia concentration is 10-20%, and the weight ratio of silica sol, polyacrylamide, and ammonia is 1:0.

01. 0.9: 0.01-0.

2.

3. The method for preparing the catalyst for fluidized bed synthesis of hydrogen cyanide according to claim 1, characterized in that, Step S1 is performed at a temperature of 25-90℃.

4. The method for preparing the catalyst for fluidized bed synthesis of hydrogen cyanide according to claim 1, characterized in that, The acid in step S2 is nitric acid with a mass concentration of 65-69%, and the pH is adjusted to 2.0-4.

0.

5. The method for preparing the catalyst for fluidized bed synthesis of hydrogen cyanide according to claim 1, characterized in that, Step S2 involves aging at 50-80℃ for 10-14 hours.

6. The method for preparing the catalyst for fluidized bed synthesis of hydrogen cyanide according to claim 1, characterized in that, The mixing and pulping temperature in step S3 is 25-90℃, and the crystallization and aging are carried out at 50-100℃ for 10-14 hours.

7. The method for preparing the catalyst for fluidized bed synthesis of hydrogen cyanide according to claim 1, characterized in that, The roasting temperature in step S3 is 350-700℃.

8. The method for preparing the catalyst for fluidized bed synthesis of hydrogen cyanide according to claim 1, characterized in that, The support accounts for 30-60% of the total weight of the catalyst.

9. A method for preparing a hydrogen cyanide catalyst according to any one of claims 1-8.

10. The application of the hydrogen cyanide catalyst prepared by the method for preparing a fluidized bed synthesis catalyst as described in any one of claims 1-8, wherein the catalyst reacts in a fluidized bed to generate hydrogen cyanide, characterized in that, The reaction temperature is 350-400℃.

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