Core-shell ammoxidation catalysts, methods of making and using same, and methods of synthesizing acrylonitrile

Abstract

The application relates to the preparation field of a catalyst, discloses a core-shell type ammonia oxidation catalyst and a preparation method and application thereof, and a synthesis method of acrylonitrile; the catalyst comprises a carrier and an active component; the active component has a general formula of Mo 10 Bi a B b C c D d O x ; B is selected from at least one of group VIII metal elements; C is selected from at least one of alkaline earth metal elements; D is selected from at least one of alkali metal elements; a, b, c and d respectively represent the molar content of Bi, B, C and D relative to Mo; the value range of a is 0.05-8.0, the value range of b is 0.02-10.0, the value range of c is 0.02-6.0, and the value range of d is 0.05-5.0; Mo exists in the form of bismuth molybdate, molybdenum trioxide and molybdate; the mesostructure of the catalyst comprises an inner core and an outer shell; the main components of the inner core comprise bismuth molybdate, molybdenum trioxide and the carrier; and the main components of the outer shell comprise molybdate and the carrier.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation technology, specifically to a core-shell type ammonia oxidation catalyst, its preparation method and application, and a method for synthesizing acrylonitrile. Background Technology

[0002] Acrylonitrile, as an important organic chemical raw material, has wide applications in synthetic fibers, synthetic resins, and many other fields. Recently, with the rapid development of ABS (acrylonitrile-butadiene-styrene copolymer) resin and acrylonitrile-based carbon fiber, downstream demand for acrylonitrile has been increasing. Currently, the main production process for acrylonitrile is the Sohio process, which uses propylene as raw material and synthesizes acrylonitrile in a fluidized bed reactor through ammonia oxidation. The catalyst used is mainly a Mo-Bi composite oxide system.

[0003] In practical applications, it has been found that after long-term operation in fluidized bed reactors, especially under high-temperature and high-load conditions, the molybdenum component tends to be severely lost due to its high volatility. This results in both catalyst loss and a significant impact on the long-term stability of catalytic activity. Currently, process units often require continuous catalyst replenishment to maintain stable reaction operation. Therefore, a key research direction in this field is to develop novel catalysts for the ammoxidation of propylene to acrylonitrile that exhibit low loss of active molybdenum component under high-temperature and high-load conditions and can operate stably for extended periods.

[0004] To address the long-term operational stability issue of acrylonitrile catalysts, researchers have conducted extensive studies on catalyst support components. CN100566829 uses silica, alumina, or mixtures thereof as supports, enabling the catalyst to operate stably at lower ammonia ratios, air ratios, and temperatures, thus improving the reaction yield and stability of acrylonitrile catalysts and reducing the content of byproducts such as carbon dioxide and hydrogen cyanide. CN101284237 modifies the support with small-molecule template agents such as tetraethylamine and tetrapropylamine, and then combines it with active components to obtain acrylonitrile catalysts with good activity, selectivity, reduction resistance, and wear resistance. CN102892498, by adjusting and controlling the composition of auxiliary agents, yields catalysts with specific X-ray diffraction patterns, which can be widely used in the ammoxidation of olefins to produce acrylonitrile and methacrylonitrile, improving the reaction conversion rate. The yield of acrylonitrile is achieved through various methods. CN110562990 proposes using silica sol with a uniform particle size distribution of 20-30 nm, a viscosity of less than 20 cPs, a mass concentration of not less than 40%, and the addition of a stabilizer as a carrier. The silica sol has a stability time of more than 20 minutes, exhibiting good stability and suitable for large-scale industrial production. CN113828322 focuses on the volatile molybdenum trioxide component in acrylonitrile catalysts, preparing molybdenum trioxide with a specific X-ray spectrum. This molybdenum trioxide forms a supplementary system with the molybdenum-based acrylonitrile catalyst and is used in the continuous supplementary process of propylene ammoxidation reaction. It can achieve a high acrylonitrile yield under high propylene load and maintain long-term stability. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem of poor stability of existing ammonia oxidation catalysts and to provide a new core-shell ammonia oxidation catalyst and its preparation method, especially the application of this catalyst in the synthesis of acrylonitrile.

[0006] As mentioned earlier, current methods for improving the stability and activity of acrylonitrile catalysts mainly focus on altering their composition, such as increasing the types of metal elements and adjusting the support composition. However, research on the control of catalyst particle structure is relatively limited. Based on this, the inventors of this invention propose, without changing the basic elemental composition of the acrylonitrile catalyst, to increase the molybdenum content inside the catalyst particles by controlling the catalyst particle structure. This is achieved by pre-hydrolyzing the molybdenum precursor and additionally introducing molybdenum trioxide, thus preparing a novel acrylonitrile catalyst with a core-shell structure. The main components of the catalyst core include bismuth molybdate, molybdenum trioxide, and a support; the main components of the catalyst shell include molybdate and a support.

[0007] Based on the inventors' research, the first aspect of this invention provides a core-shell type ammonia oxidation catalyst, the catalyst comprising a support and an active component; the active component has the general formula Mo. 10 Bia B b C c D d O x B is selected from at least one of Group VIII metals; C is selected from at least one of alkaline earth metals; D is selected from at least one of alkali metals; a, b, c, and d represent the molar content of Bi, B, C, and D relative to Mo, respectively; the value of a ranges from 0.05 to 8.0, the value of b ranges from 0.02 to 10.0, the value of c ranges from 0.02 to 6.0, the value of d ranges from 0.05 to 5.0, and x is determined by the atomic ratio and valence state of the elements other than oxygen in the general formula of the active component; wherein, Mo exists simultaneously in the form of bismuth molybdate, molybdenum trioxide, and molybdate; the mesoscopic structure of the catalyst includes a core and a shell; the main components of the catalyst core include bismuth molybdate, molybdenum trioxide, and a support; the main components of the catalyst shell include molybdate and a support.

[0008] A second aspect of the present invention provides a method for preparing the above-mentioned catalyst, the method comprising:

[0009] (1) The precursors of molybdenum, bismuth, molybdenum trioxide powder, and the carrier source are mixed and contacted in solution, and then hydrolyzed and combined under acidic conditions to obtain the precursor with the core structure.

[0010] (2) The precursors of the core structure, B, C, and D, and the surfactant are mixed and contacted in solution, and then dried and calcined to obtain the catalyst.

[0011] A third aspect of the present invention provides the application of the catalyst described herein in the preparation of nitrile compounds from C2-C5 hydrocarbons.

[0012] A fourth aspect of the present invention provides a method for synthesizing acrylonitrile, the method comprising carrying out an ammoxidation reaction of propylene under a mixed gas condition containing oxygen and ammonia.

[0013] Compared with the prior art, the present invention has at least the following beneficial effects:

[0014] (1) The catalyst of the present invention has a core-shell structure, with a core of molybdate / molybdenum oxide / support component and a shell of molybdate / support component. This structure helps to reduce the volatilization and loss of molybdenum component during long-term operation, thereby achieving long-term stable operation of the catalyst under high load.

[0015] (2) The catalyst of the present invention can maintain a high propylene conversion rate and a high single-pass yield of acrylonitrile even after long-term operation. Attached Figure Description

[0016] Figure 1This is a radial variation diagram of the Mo element intensity in the ammonia oxidation catalyst particles of Example 1 (from the center of the catalyst particle outward to the surface of the catalyst particle). Detailed Implementation

[0017] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0018] A first aspect of this invention provides a core-shell ammonia oxidation catalyst, the catalyst comprising a support and an active component; the active component having the general formula Mo. 10 Bi a B b C c D d O x B is selected from at least one of Group VIII metals; C is selected from at least one of alkaline earth metals; D is selected from at least one of alkali metals; a, b, c, and d represent the molar content of Bi, B, C, and D relative to Mo, respectively; the value of a ranges from 0.05 to 8.0, the value of b ranges from 0.02 to 10.0, the value of c ranges from 0.2 to 6.0, the value of d ranges from 0.05 to 5.0, and x is determined by the atomic ratio and valence state of the elements other than oxygen in the general formula of the active component; among them, Mo exists simultaneously in the form of bismuth molybdate, molybdenum trioxide, and molybdate.

[0019] The mesoscopic structure of the catalyst includes a core and a shell; the main components of the catalyst core include bismuth molybdate, molybdenum trioxide, and a support; the main components of the catalyst shell include molybdate and a support.

[0020] In this invention, the components in the core and shell can be obtained by scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), wherein the core and shell constitute a core-shell structure.

[0021] In this invention, "Mo" 10 Bi a B b C c D d O x The general formula "" only represents the individual elements and their molar content of the active component in the catalyst, and does not represent that the active component of the catalyst in this invention exists as a molecule of this general formula.

[0022] In this invention, the core of the catalyst is in close contact with the outer shell.

[0023] In this invention, the molybdate in the shell component refers to molybdates of elements such as B, C and D, such as magnesium molybdate, iron molybdate, etc.

[0024] In this invention, by studying the particle structure regulation of the catalyst, the catalyst core contains molybdenum trioxide, which includes bismuth molybdate, molybdenum trioxide and a support, and the outer shell contains molybdate and a support. This structure helps to reduce the volatilization and loss of molybdenum components during long-term operation, thereby achieving long-term stable operation of the catalyst under high load.

[0025] According to the present invention, the content of each element in the active component is not particularly limited as long as the purpose of the present invention can be achieved. In some preferred embodiments, the value of a ranges from 0.05 to 4 (e.g., 0.05, 0.1, 0.3, 0.4, 0.5, 1, 2, 3, or 4); in some preferred embodiments, the value of b ranges from 0.1 to 10 (e.g., 0.1, 0.5, 1, 2, 4, 5, 7, 8, 9, or 10); in some preferred embodiments, the value of c ranges from 0.1 to 6 (e.g., 0.1, 0.5, 1, 2, 4, 5, or 6), and the value of d ranges from 0.05 to 2 (e.g., 0.05, 0.06, 0.07, 0.1, 0.2, 0.5, 1, 1.5, or 2). Using the aforementioned embodiments, the catalytic activity of the catalyst in the ammonia oxidation reaction can be better increased.

[0026] According to the present invention, in some embodiments, the molybdenum content in the core and the outer shell differs based on the total weight of molybdenum in the catalyst. By employing the aforementioned embodiments, the catalyst achieves long-term stable operation under high loads.

[0027] According to the present invention, in some embodiments, the molybdenum content in the core is higher than the molybdenum content in the outer shell, based on the total weight of molybdenum in the catalyst. Using the aforementioned embodiments helps to reduce the volatilization and loss of molybdenum components during long-term operation, thereby achieving long-term stable operation of the catalyst under high loads.

[0028] According to some preferred embodiments of the present invention, the molybdenum content in the core is 60-80 wt%, and the molybdenum content in the shell is 20-40 wt%, based on the total amount of molybdenum in the catalyst. Using the aforementioned embodiments can better increase the activity and stability of the catalyst.

[0029] According to the present invention, in some preferred embodiments, the proportion of the support in the core to the total amount of support in the catalyst is 50-65 wt%, and the proportion of the support in the shell to the total amount of support in the catalyst is 35-50 wt%. Using the aforementioned embodiments can better increase the activity and stability of the catalyst.

[0030] According to some preferred embodiments of the present invention, the proportion of bismuth in the core to the total amount of bismuth in the catalyst is 55-65 wt%, and the proportion of bismuth in the shell to the total amount of bismuth in the catalyst is 35-45 wt%. Using the aforementioned embodiments can further increase the catalytic activity and stability of the catalyst in the ammonia oxidation reaction.

[0031] According to some preferred embodiments of the present invention, the proportion of element B in the core to the total amount of element B in the catalyst is 30-45 wt%, and the proportion of element B in the shell to the total amount of element B in the catalyst is 55-70 wt%. Using the aforementioned embodiments can further increase the activity and stability of the catalyst.

[0032] According to some preferred embodiments of the present invention, the proportion of carbon in the core to the total carbon content of the catalyst is 30-45 wt%, and the proportion of carbon in the shell to the total carbon content of the catalyst is 55-70 wt%. Using the aforementioned embodiments can further increase the activity and stability of the catalyst.

[0033] According to the present invention, in some preferred embodiments, the proportion of D element in the core to the total D element in the catalyst is 35-45 wt%, and the proportion of D element in the shell to the total D element in the catalyst is 55-65 wt%. Using the aforementioned embodiments can further increase the activity and stability of the catalyst.

[0034] According to the present invention, in some embodiments, B is selected from at least one of iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, and platinum, preferably at least one of iron, cobalt, and nickel. Using the aforementioned embodiments can increase the activity and stability of the catalyst.

[0035] According to the present invention, in some embodiments, C is selected from at least one of magnesium, calcium, strontium, and barium, preferably magnesium and / or calcium. Using the aforementioned embodiments can increase the activity and stability of the catalyst.

[0036] According to the present invention, in some embodiments, D is selected from at least one of sodium, potassium, rubidium, and cesium, preferably potassium. By employing the aforementioned embodiments, the activity of the catalyst and its long-term stable operation under high loads can be further increased.

[0037] According to some preferred embodiments of the present invention, the catalyst has a specific surface area of ​​35-60 m². 2 / g. The catalysts described in the aforementioned embodiments are more conducive to the contact between the catalyst and the reaction substrate.

[0038] According to some preferred embodiments of the present invention, the pores with a diameter of 20-35 nm on the core account for 40-50% of the total pores in the catalyst. Using the aforementioned embodiments, the catalytic activity of the catalyst and the selectivity of nitrile target products can be better increased.

[0039] According to the present invention, in some preferred embodiments, the pores with a diameter of 6-12 nm on the outer shell account for 50-60% of the total pores in the catalyst. By employing the aforementioned embodiments, the stability of the catalyst can be better increased. The inventors speculate that the outer shell structure provides good protection for the core, limiting the loss of the core active components through the outer shell pores.

[0040] According to some preferred embodiments of the present invention, the radius of the catalyst particle is defined as the distance from the center of the catalyst particle to the particle surface, the radius of the core is 40-60% of the radius of the catalyst particle, and the portion along the surface of the core toward the surface of the catalyst particle is the outer shell.

[0041] According to the present invention, it is understood that the center of the core coincides with the center of the catalyst particle, and the radius of the catalyst particle extends from the center of the catalyst particle outward to the particle surface. The core of the catalyst is located at 40-60% (e.g., 40%, 42%, 45%, 50%, 52%, 55%, 58%, or 60%) of this radius, and the outer shell of the catalyst is located outward.

[0042] According to the present invention, the content of the active component and the support is not particularly limited as long as the purpose of the present invention can be achieved. In some embodiments, the mass ratio of the active component to the support is (1.5-0.8):1, preferably (1.2-1.0):1. By adopting the aforementioned embodiments, the activity of the catalyst and its long-term stable operation under high load can be better increased.

[0043] According to the present invention, the type of carrier is not particularly limited as long as the purpose of the present invention can be achieved. In some embodiments, the carrier includes alumina and / or silicon oxide.

[0044] A second aspect of the present invention provides a method for preparing the above-mentioned catalyst, the method comprising:

[0045] (1) The precursors of molybdenum, bismuth, molybdenum trioxide powder, and the carrier source are mixed and contacted in solution, and then hydrolyzed and combined under acidic conditions to obtain the precursor with the core structure.

[0046] (2) The precursors of the core structure, B, C, and D, and the surfactant are mixed and contacted in solution, and then dried and calcined to obtain the catalyst.

[0047] According to the present invention, the specific types of precursors for molybdenum and bismuth are not limited, as long as they provide the corresponding molybdenum and bismuth elements and can be dissolved in a solvent to form a homogeneous solvent, such as the corresponding inorganic salts, nitrates, chlorides, etc.

[0048] According to the present invention, the mixing and contact of molybdenum precursor, bismuth precursor, molybdenum trioxide powder, and carrier source in solution refers to the contact of molybdenum precursor, bismuth precursor, and molybdenum trioxide powder in the presence of a solvent. During the mixing and contact, the molybdenum precursor, bismuth precursor, molybdenum trioxide powder, and carrier source can be added to the solvent sequentially or simultaneously for mixing; alternatively, the molybdenum precursor, molybdenum trioxide powder, and carrier source can be mixed with a solvent to obtain a mixture containing molybdenum precursor, molybdenum trioxide powder, and carrier source; the bismuth precursor can be mixed with a solvent to obtain a mixture containing bismuth precursor; then, the mixture containing molybdenum precursor, molybdenum trioxide powder, and carrier source is mixed and contacted with the mixture containing bismuth precursor; other mixing and contact methods can also be selected. Furthermore, the carrier source can be dispersed in a solvent as needed before mixing and contacting with other components. The present invention is not limited to the mixing and contact methods listed above. In order to achieve more uniform mixing during mixing and contact or the preparation of the corresponding mixture, mixing can be carried out under heating and / or stirring conditions. For example, mix for 5-30 minutes at a temperature of 30-100℃ and a stirring speed of 200-450 rpm.

[0049] According to the present invention, the solvent used in step (1) is not particularly limited, and any solvent that can dissolve the precursor of molybdenum and the precursor of bismuth is acceptable, including but not limited to water. The amount of solvent is not particularly limited, as long as the precursor of molybdenum and the precursor of bismuth can be completely dissolved.

[0050] According to the present invention, the amounts of molybdenum trioxide powder and molybdenum precursor are not particularly limited as long as the objectives of the present invention can be achieved. In some embodiments, the mass ratio of molybdenum trioxide powder to molybdenum precursor is 1:(1-30), for example 1:1, 1:2, 1:5, 1:7, 1:10, 1:12, 1:15, 1:18, 1:22, 1:25 or 1:30, preferably 1:(3-15). Using the aforementioned embodiments helps to reduce the volatilization and loss of molybdenum components during long-term operation, thereby achieving long-term stable operation of the catalyst under high loads.

[0051] According to the present invention, the specific type of molybdenum trioxide powder is not particularly limited as long as the purpose of the present invention can be achieved. In some embodiments, the molybdenum trioxide powder is in the α-MoO3 crystal form, with a particle size of 300-600 mesh. By adopting the aforementioned embodiments, the molybdenum content and stability of the molybdenum component in the catalyst can be improved, which helps to reduce the volatilization and loss of the molybdenum component during long-term operation, thereby achieving long-term stable operation of the catalyst under high load.

[0052] According to the present invention, the specific type of the carrier source is not particularly limited as long as the purpose of the present invention can be achieved. In some embodiments, the carrier source is selected from at least one of silica sol, alumina sol, aluminosilicate molecular sieve (e.g., ZSM-5 aluminosilicate molecular sieve) and silica powder.

[0053] In this invention, the advantages of the invention are illustrated by using silica sol with a particle size of 10-25 nanometers (mass concentration of 30%) and ZSM-5 silica-alumina molecular sieve with a silica-to-alumina ratio of 150-200 and a mesh size of 800-1000 as examples, but the invention is not limited thereto.

[0054] According to the present invention, the acidic conditions in step (1) are not particularly limited as long as the purpose of the present invention can be achieved. In some embodiments, the acidic conditions in step (1) are pH = 2-3. The catalyst prepared by the above embodiments has good activity and stability.

[0055] According to the present invention, in order to make the acidic conditions pH = 2-3, a pH adjuster can be used for adjustment, wherein the pH adjuster includes, but is not limited to, nitric acid.

[0056] According to the present invention, the amount of surfactant used is not particularly limited as long as the purpose of the present invention can be achieved. In some embodiments, the mass ratio of the surfactant to the support is (0.005-0.05):1. Using the aforementioned embodiments helps the catalyst form a smaller mesoporous structure, which can reduce the volatilization and loss of molybdenum components during long-term operation, thereby achieving long-term stable operation of the catalyst under high loads.

[0057] According to the present invention, the specific type of surfactant is not particularly limited as long as the purpose of the present invention can be achieved. In some embodiments, the surfactant is selected from at least one of water-soluble urea compounds, polyols, and quaternary ammonium salt surfactants, preferably including at least one of urea, ethylene glycol, hexadecyltrimethylammonium bromide (CTAB), and hexadecyltrimethylammonium chloride (CTAC). The aforementioned embodiments better increase the activity and stability of the catalyst.

[0058] According to the present invention, in step (2), the mixing and contact of the precursor of the core structure, the precursor of B, the precursor of C, the precursor of D and the surfactant in solution refers to the mixing and contact of the precursor of the core structure, the precursor of B, the precursor of C, the precursor of D and the surfactant in the presence of a solvent, either sequentially or simultaneously. Alternatively, the precursors of B, C and D can be dissolved in a solvent to obtain a solution containing the precursors of B, C and D, and the surfactant can be dispersed in a solvent to obtain a surfactant solution of a certain concentration. Then, the solution containing the precursors of B, C and D and the surfactant solution of a certain concentration can be added sequentially or simultaneously to the precursor of the core structure for mixing. In order to make the mixing more uniform, the mixing can be carried out under heating and / or stirring conditions, for example, heating and stirring for 10-30 minutes at a temperature of 90-120°C and a stirring speed of 150-250 rpm. In addition, in order to improve the drying efficiency, the mixing can be carried out at a temperature greater than 100°C to form a slurry.

[0059] According to the present invention, the solvent used in step (2) is not particularly limited, and any solvent that can dissolve the precursors of B, C and D is acceptable, including but not limited to water. The amount of solvent used is not particularly limited, as long as the precursors of B, C and D can be completely dissolved.

[0060] According to the present invention, as long as the purpose of the present invention can be achieved, the drying and calcination conditions in step (2) are not particularly limited. In some embodiments, the drying method is spray drying, the heat source is air, the drying temperature is 280-400℃, the drying time is 0.5-1.0h, and the average diameter of the spray droplets is 30-120μm. In some embodiments, the calcination method is carried out in an oxygen-containing atmosphere (e.g., air), the calcination temperature is 400-650℃, and the calcination time is 4-6h.

[0061] A third aspect of the present invention provides the application of the catalyst described herein in the preparation of nitrile compounds from C2-C5 hydrocarbons.

[0062] The catalyst of this invention not only exhibits excellent catalytic activity in the preparation of nitrile compounds, but also maintains high conversion rates of C2-C5 hydrocarbons and single-pass yields of nitrile compounds even after long-term operation.

[0063] In this invention, C2-C5 hydrocarbon compounds include C2-C5 alkanes and C2-C5 alkenes.

[0064] A fourth aspect of the present invention provides a method for synthesizing acrylonitrile, the method comprising carrying out an ammoxidation reaction of propylene under a mixed gas condition containing oxygen and ammonia.

[0065] The catalyst of this invention can maintain a high propylene conversion rate and acrylonitrile single-pass yield even after long-term operation.

[0066] According to some embodiments of the present invention, the conditions for the ammonia oxidation reaction include: an oxygen-containing atmosphere (based on oxygen), a molar ratio of propylene, an oxygen-containing atmosphere (e.g., air), and ammonia of 1:(1.2-1.3):(9.6-10.0); and / or a reaction temperature of 420-435°C; and / or a reaction pressure (gauge pressure) of 0.06-0.14 MPa; and / or a catalyst loading of 0.08-0.12 h. -1 .

[0067] The present invention will be described in detail below through embodiments. The following embodiments and comparisons are as follows:

[0068] Specific surface area and pore size were measured using a Tristar physical adsorption instrument. Before testing, the samples underwent heating and vacuum degassing. Porosity was determined at 77 K, and specific surface area was calculated using the Brunauer-Emmett-Teller (BET) method. The pore size distribution and pore volume were calculated from the isothermal adsorption branch using the Barrettner-Joyner-Halenda (BJH) model.

[0069] In this invention, the quantitative analysis of elements is performed by scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) to obtain the element intensity distribution, and the relative content of elements is calculated.

[0070] Online analysis of the product gases was performed using gas chromatography. Propylene conversion, acrylonitrile selectivity, and single-pass yield were used as performance indicators for the catalyst, and their definitions are as follows:

[0071] Acrylonitrile conversion rate (%) = (moles of propylene reacted / moles of propylene fed) × 100%;

[0072] Acrylonitrile selectivity (%) = (moles of acrylonitrile produced / moles of propylene reacted) × 100%;

[0073] Acrylonitrile single-pass yield (%) = (moles of acrylonitrile produced / moles of propylene fed) × 100%.

[0074] Example 1

[0075] Preparation of ammonia oxidation catalyst:

[0076] (1) 211.9 grams of (NH4)6Mo7O 24 • 4H2O was dissolved in 200g of water at 100℃, and 23g of 600-mesh molybdenum trioxide powder and 900g of 30% silica sol were added and mixed thoroughly to obtain mixture I; 29.1g of Bi(NO3)3·5H2O was dissolved in 15g of water at 100℃ and added to mixture I. The mixture was stirred at 200 rpm for 20 min, and then nitric acid solution was added to adjust the pH to 2-3. The mixture was stirred and hydrolyzed to obtain mixture II.

[0077] (2) After heating and stirring the mixture II at 60°C for 15 min, dissolve 145.4 g of Ni(NO3)2·6H2O, 80.8 g of Fe(NO3)3·9H2O, 38.5 g of Mg(NO3)2·6H2O and 0.84 g of KNO3 in 120 g of water and add them to the mixture II. Add 50 mL of 10% hexadecyltrimethylammonium bromide aqueous solution while heating and stirring at 60°C. Heat and stir at 100°C for 20 min to obtain the mixed slurry III. The stirring speed during the stirring in step (2) is 250 rpm.

[0078] (3) Slurry III was spray-dried at 350°C for 0.5 hours to obtain particulate matter. The particulate matter was then calcined in air at 600°C for 3 hours to obtain an ammonia oxidation catalyst with the following general formula: 50wt% Mo 10 Bi 0.4 4Fe 1.5 Ni 3.7 Mg 1.1 K 0.11 O 37.6 +50wt% SiO2;

[0079] Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analysis revealed that the ammonia oxidation catalyst consists of a core and a shell. The radius of the catalyst particle is defined as the distance from the center of the particle outwards to the particle surface. The radius of the core is 49% of the radius of the catalyst particle (where the core radius is 13.4 μm and the catalyst particle radius is 27.3 μm). The portion extending from the surface of the core to the surface of the catalyst particle constitutes the shell. The radial variation of Mo content in the ammonia oxidation catalyst (from the center of the catalyst particle outwards to the surface of the catalyst particle) in this embodiment is shown in the figure below. Figure 1 As shown; elemental composition content and Figure 1 The vertical axis is proportional to the intensity, and the Mo content is based on... Figure 1 The results were obtained through analysis and calculation.

[0080] The elemental contents of the catalyst were determined by scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) as follows:

[0081] In the core and shell, Mo accounts for 68 wt% and 32 wt% of the total Mo in the catalyst, respectively.

[0082] In the core and shell, Bi accounts for 57 wt% and 43 wt% of the total Bi in the catalyst, respectively.

[0083] In the core and shell, Fe accounts for 35 wt% and 65 wt% of the total Fe in the catalyst, respectively.

[0084] In the core and shell, Ni accounts for 36 wt% and 64 wt% of the total Ni in the catalyst, respectively.

[0085] In the core and shell, Mg accounts for 33 wt% and 67 wt% of the total Mg in the catalyst, respectively.

[0086] In the core and shell, K accounts for 42 wt% and 58 wt% of the total K in the catalyst, respectively.

[0087] In the core and shell, the support accounts for 61 wt% and 39 wt% of the total amount of support in the catalyst, respectively.

[0088] The catalyst has a specific surface area of ​​47.3 m². 2 / g, the pore size includes two different sizes: 8nm (present in the outer shell) and 22nm (present in the core). The proportions of the two pore sizes in the total pores of the catalyst are 56% and 44% respectively, calculated by integrating the pore size distribution area.

[0089] Catalyst evaluation:

[0090] In the presence of the ammonia oxidation catalyst prepared above, propylene ammonia oxidation to acrylonitrile was carried out under the following conditions: reaction temperature: 420℃; reaction pressure: 0.085 MPa; catalyst loading: 300 g; catalyst propylene loading (WWH): 0.12 h. -1 Raw material ratio (moles): Propylene: NH3: Air (as oxygen) = 1:1.25:9.7.

[0091] Catalyst evaluation results:

[0092] After 3 hours of operation, the propylene conversion rate was 98.87%, the acrylonitrile selectivity was 83.79%, and the acrylonitrile single-pass yield was 82.84%; after 500 hours of operation, the propylene conversion rate was 98.65%, the acrylonitrile selectivity was 83.43%, and the acrylonitrile single-pass yield was 82.30%.

[0093] Example 2

[0094] Preparation of ammonia oxidation catalyst:

[0095] (1) 211.9 grams of (NH4)6Mo7O 24 ·4H2O was dissolved in 200g of water at 100℃, and 23g of 600-mesh molybdenum trioxide powder and a carrier source dispersion containing 270g of ZSM-5 silica-alumina molecular sieve (obtained by mixing 270g of ZSM-5 silica-alumina molecular sieve with a molar silica-alumina ratio of 150 and a mesh size of 800-1000 mesh with 630g of water) were added. The mixture was thoroughly mixed to obtain mixture I. 29.1g of Bi(NO3)3·5H2O was dissolved in 15g of water at 100℃ and added to mixture I. The mixture was stirred at a stirring speed of 200 rpm for 20min. Then, nitric acid solution was added to adjust the pH to 2-3, and stirring was continued to ensure thorough mixing and hydrolysis to obtain mixture II.

[0096] (2) After heating and stirring the mixture II at 60°C for 15 min, dissolve 145.4 g of Ni(NO3)2·6H2O, 80.8 g of Fe(NO3)3·9H2O, 38.5 g of Mg(NO3)2·6H2O and 0.84 g of KNO3 in 120 g of water and add them to the mixture II. Add 50 mL of 10% hexadecyltrimethylammonium bromide aqueous solution while heating and stirring at 60°C. Heat and stir at 100°C for 20 min to obtain the mixed slurry III. The stirring speed during the stirring in step (2) is 250 rpm.

[0097] (3) Slurry III was spray-dried at 350°C for 0.5 hours to obtain particulate matter. The particulate matter was then calcined in air at 550°C for 3 hours to obtain an ammonia oxidation catalyst with the following general formula: 50wt% Mo10 Bi 0.4 4Fe 1.5 Ni 3.7 Mg 1.1 K 0.11 O 37.6 +50wt% ZSM-5 silica-alumina molecular sieve;

[0098] Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analysis revealed that the ammonia oxidation catalyst consists of a core and a shell. The radius of the catalyst particle is defined as the distance from the center of the particle outwards to the particle surface. The radius of the core is 52% of the radius of the catalyst particle (where the core radius is 14.6 μm and the catalyst particle radius is 28.1 μm). The portion extending from the surface of the core to the surface of the catalyst particle constitutes the shell. The elemental contents of the catalyst are as follows:

[0099] In the core and shell, Mo accounts for 66 wt% and 34 wt% of the total Mo in the catalyst, respectively.

[0100] In the core and shell, Bi accounts for 56 wt% and 44 wt% of the total Bi in the catalyst, respectively.

[0101] In the core and shell, Fe accounts for 36 wt% and 64 wt% of the total Fe in the catalyst, respectively.

[0102] In the core and shell, Ni accounts for 37 wt% and 63 wt% of the total Ni in the catalyst, respectively.

[0103] In the core and shell, Mg accounts for 33 wt% and 67 wt% of the total Mg in the catalyst, respectively.

[0104] In the core and shell, K accounts for 43 wt% and 57 wt% of the total K in the catalyst, respectively.

[0105] In the core and shell, the support accounts for 60 wt% and 40 wt% of the total amount of support in the catalyst, respectively.

[0106] The catalyst has a specific surface area of ​​51.0 m². 2 / g, the pore size includes two different sizes: 7nm (present in the outer shell) and 23nm (present in the core). The proportion of the two pore sizes in the total pores of the catalyst is calculated by integrating the area of ​​the pore size distribution, which is 55% and 45%, respectively.

[0107] The catalyst evaluation method is the same as in Example 1.

[0108] Catalyst evaluation results:

[0109] After 3 hours of operation, the propylene conversion rate was 98.78%, the acrylonitrile selectivity was 83.80%, and the acrylonitrile single-pass yield was 82.78%; after 500 hours of operation, the propylene conversion rate was 98.55%, the acrylonitrile selectivity was 83.32%, and the acrylonitrile single-pass yield was 82.11%.

[0110] Example 3

[0111] Preparation of ammonia oxidation catalyst:

[0112] (1) 211.9 grams of (NH4)6Mo7O 24 • 4H2O was dissolved in 200g of water at 100℃, and 23g of 600-mesh molybdenum trioxide powder and 900g of 30% silica sol were added and mixed thoroughly to obtain mixture I; 29.1g of Bi(NO3)3·5H2O was dissolved in 15g of water at 100℃ and added to mixture I. The mixture was stirred at 200 rpm for 20 min, and then nitric acid solution was added to adjust the pH to 2-3. The mixture was stirred and hydrolyzed to obtain mixture II.

[0113] (2) After heating and stirring the mixture II at 60°C for 15 min, dissolve 96.9 g Ni(NO3)2·6H2O, 80.8 g Fe(NO3)3·9H2O, 38.5 g Mg(NO3)2·6H2O and 0.84 g KNO3 in 120 g water and add them to the mixture II. Add 50 mL of 10% urea aqueous solution while heating and stirring at 60°C. Heat and stir at 110°C for 20 min to obtain the mixed slurry III. The stirring speed during the stirring in step (2) is 250 rpm.

[0114] (3) Slurry III was spray-dried at 380°C for 0.5 hours to obtain particulate matter. The particulate matter was then calcined in air at 600°C for 3 hours to obtain an ammonia oxidation catalyst with the following general formula: 50wt% Mo 10 Bi 0.4 4Fe 1.5 Ni 2.5 Mg 1.1 K 0.11 O 36.3 +50wt% SiO2;

[0115] Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analysis revealed that the ammonia oxidation catalyst consists of a core and a shell. The radius of the catalyst particle is defined as the distance from the center of the particle outward to the particle surface. The radius of the core is 50% of the radius of the catalyst particle (where the core radius is 14.2 μm and the catalyst particle radius is 28.4 μm). The portion extending from the surface of the core to the surface of the catalyst particle constitutes the shell. The elemental contents of the catalyst are as follows:

[0116] In the core and shell, Mo accounts for 67 wt% and 33 wt% of the total Mo in the catalyst, respectively.

[0117] In the core and shell, Bi accounts for 56 wt% and 44 wt% of the total Bi in the catalyst, respectively.

[0118] In the core and shell, Fe accounts for 37 wt% and 63 wt% of the total Fe in the catalyst, respectively.

[0119] In the core and shell, Ni accounts for 36 wt% and 64 wt% of the total Ni in the catalyst, respectively.

[0120] In the core and shell, Mg accounts for 32 wt% and 68 wt% of the total Mg in the catalyst, respectively.

[0121] In the core and shell, K accounts for 45 wt% and 55 wt% of the total K in the catalyst, respectively.

[0122] In the core and shell, the support accounts for 58 wt% and 42 wt% of the total amount of support in the catalyst, respectively.

[0123] The catalyst has a specific surface area of ​​48.5 m². 2 / g, the pore size includes two different sizes: 8nm (present in the outer shell) and 23nm (present in the core). The proportion of the two pore sizes in the total pores of the catalyst is calculated by integrating the area of ​​the pore size distribution, which are 57% and 43%, respectively.

[0124] The catalyst evaluation method is the same as in Example 1.

[0125] Catalyst evaluation results:

[0126] After 3 hours of operation, the propylene conversion rate was 98.80%, the acrylonitrile selectivity was 83.72%, and the acrylonitrile single-pass yield was 82.71%; after 500 hours of operation, the propylene conversion rate was 98.53%, the acrylonitrile selectivity was 83.40%, and the acrylonitrile single-pass yield was 82.17%.

[0127] Example 4

[0128] Preparation of ammonia oxidation catalyst:

[0129] (1) 155.5 grams of (NH4)6Mo7O 24 • 4H2O was dissolved in 200g of water at 100℃, and 69g of 600-mesh molybdenum trioxide powder and 900g of 30% silica sol were added and mixed thoroughly to obtain mixture I; 29.1g of Bi(NO3)3·5H2O was dissolved in 15g of water at 100℃ and added to mixture I. The mixture was stirred at 200 rpm for 20 min, and then nitric acid solution was added to adjust the pH to 2-3. The mixture was stirred and hydrolyzed to obtain mixture II.

[0130] (2) After heating and stirring the mixture II at 60°C for 15 min, dissolve 145.4 g of Ni(NO3)2·6H2O, 80.8 g of Fe(NO3)3·9H2O, 38.5 g of Mg(NO3)2·6H2O and 0.84 g of KNO3 in 120 g of water and add them to the mixture II. Add 50 mL of 10% hexadecyltrimethylammonium bromide aqueous solution while heating and stirring at 60°C. Heat and stir at 100°C for 20 min to obtain the mixed slurry III. The stirring speed during the stirring in step (2) is 250 rpm.

[0131] (3) Slurry III was spray-dried at 350°C for 0.5 hours to obtain particulate matter. The particulate matter was then calcined at 600°C in air for 3 hours to obtain the ammonia oxidation catalyst.

[0132] Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analysis revealed that the ammonia oxidation catalyst consists of a core and a shell. The radius of the catalyst particle is defined as the distance from the center of the particle to the particle surface. The radius of the core is 56% of the radius of the catalyst particle (where the core radius is 16.0 μm and the catalyst particle radius is 28.6 μm). The portion extending from the surface of the core to the surface of the catalyst particle constitutes the shell. The elemental contents of the catalyst are as follows:

[0133] In the core and shell, Mo accounts for 82 wt% and 18 wt% of the total Mo in the catalyst, respectively.

[0134] In the core and shell, Bi accounts for 60 wt% and 40 wt% of the total Bi in the catalyst, respectively.

[0135] In the core and shell, Fe accounts for 35 wt% and 65 wt% of the total Fe in the catalyst, respectively.

[0136] In the core and shell, Ni accounts for 37 wt% and 63 wt% of the total Ni in the catalyst, respectively.

[0137] In the core and shell, Mg accounts for 33 wt% and 67 wt% of the total Mg in the catalyst, respectively.

[0138] In the core and shell, K accounts for 41 wt% and 59 wt% of the total K in the catalyst, respectively.

[0139] In the core and shell, the support accounts for 62 wt% and 38 wt% of the total amount of support in the catalyst, respectively.

[0140] The catalyst has a specific surface area of ​​43.1 m². 2 / g, the pore size includes two different sizes: 9nm (present in the outer shell) and 24nm (present in the core). The proportions of the two pore sizes in the total pores of the catalyst are 53% and 47% respectively, calculated by integrating the pore size distribution area.

[0141] The catalyst evaluation method is the same as in Example 1.

[0142] Catalyst evaluation results:

[0143] After 3 hours of operation, the propylene conversion rate was 97.56%, the acrylonitrile selectivity was 82.20%, and the acrylonitrile single-pass yield was 80.19%. After 500 hours of operation, the propylene conversion rate was 96.82%, the acrylonitrile selectivity was 81.61%, and the acrylonitrile single-pass yield was 79.01%.

[0144] Example 5

[0145] Preparation of ammonia oxidation catalyst:

[0146] (1) 230.8 grams of (NH4)6Mo7O 24 • 4H2O was dissolved in 200g of water at 100℃, and 7.7g of 600-mesh molybdenum trioxide powder and 900g of 30% silica sol were added and mixed thoroughly to obtain mixture I; 29.1g of Bi(NO3)3·5H2O was dissolved in 15g of water at 100℃ and added to mixture I. The mixture was stirred at 200 rpm for 20 min, and then nitric acid solution was added to adjust the pH to 2-3. The mixture was stirred and hydrolyzed to obtain mixture II.

[0147] (2) After heating and stirring the mixture II at 60°C for 15 min, dissolve 145.4 g of Ni(NO3)2·6H2O, 80.8 g of Fe(NO3)3·9H2O, 38.5 g of Mg(NO3)2·6H2O and 0.84 g of KNO3 in 120 g of water and add them to the mixture II. Add 50 mL of 10% hexadecyltrimethylammonium bromide aqueous solution while heating and stirring at 60°C. Heat and stir at 100°C for 20 min to obtain the mixed slurry III. The stirring speed during the stirring in step (2) is 250 rpm.

[0148] (3) Spray dry slurry III at 350°C for 0.5 hours to obtain particulate matter. Then calcine the particulate matter in air at 600°C for 3 hours to obtain ammonia oxidation catalyst.

[0149] Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analysis revealed that the ammonia oxidation catalyst consists of a core and a shell. The radius of the catalyst particle is defined as the distance from the center of the particle outward to the particle surface. The radius of the core is 45% of the radius of the catalyst particle (where the core radius is 13.1 μm and the catalyst particle radius is 29.1 μm). The portion extending from the surface of the core to the surface of the catalyst particle constitutes the shell. The elemental contents of the catalyst are as follows:

[0150] In the core and shell, Mo accounts for 56 wt% and 44 wt% of the total Mo in the catalyst, respectively.

[0151] In the core and shell, Bi accounts for 58 wt% and 42 wt% of the total Bi in the catalyst, respectively.

[0152] In the core and shell, Fe accounts for 35 wt% and 65 wt% of the total Fe in the catalyst, respectively.

[0153] In the core and shell, Ni accounts for 37 wt% and 63 wt% of the total Ni in the catalyst, respectively.

[0154] In the core and shell, Mg accounts for 33 wt% and 67 wt% of the total Mg in the catalyst, respectively.

[0155] In the core and shell, K accounts for 42 wt% and 58 wt% of the total K in the catalyst, respectively.

[0156] In the core and shell, the support accounts for 61 wt% and 39 wt% of the total amount of support in the catalyst, respectively.

[0157] The catalyst has a specific surface area of ​​50.9 m². 2 / g, the pore size includes two different sizes: 7nm (present in the outer shell) and 23nm (present in the core). The proportions of the two pore sizes are calculated by integrating the area of ​​the pore size distribution, which are 52% and 48%, respectively.

[0158] The catalyst evaluation method is the same as in Example 1;

[0159] Catalyst evaluation results:

[0160] After 3 hours of operation, the propylene conversion rate was 97.72%, the acrylonitrile selectivity was 82.05%, and the acrylonitrile single-pass yield was 80.18%; after 500 hours of operation, the propylene conversion rate was 96.85%, the acrylonitrile selectivity was 81.36%, and the acrylonitrile single-pass yield was 78.79%.

[0161] Example 6

[0162] Preparation of ammonia oxidation catalyst:

[0163] (1) 211.9 grams of (NH4)6Mo7O 24 • 4H2O was dissolved in 200g of water at 100℃, and 23g of 600-mesh molybdenum trioxide powder and 900g of 30% silica sol were added and mixed thoroughly to obtain mixture I; 29.1g of Bi(NO3)3·5H2O was dissolved in 15g of water at 100℃ and added to mixture I. The mixture was stirred at 200 rpm for 20 min, and then nitric acid solution was added to adjust the pH to 2-3. The mixture was stirred and then stirred to ensure thorough mixing and hydrolysis to obtain solution II.

[0164] (2) After heating and stirring the mixture II at 60°C for 15 min, dissolve 145.4 g of Ni(NO3)2·6H2O, 80.8 g of Fe(NO3)3·9H2O, 38.5 g of Mg(NO3)2·6H2O and 0.84 g of KNO3 in 120 g of water and add them to the mixture II. Add 50 mL of 10% hexadecyltrimethylammonium bromide aqueous solution while heating and stirring at 60°C. Heat and stir at 100°C for 20 min to obtain the mixed slurry III. The stirring speed during the stirring in step (2) is 250 rpm.

[0165] (3) Spray dry slurry III at 350°C for 0.5 hours to obtain particulate matter. Then calcine the particulate matter in air at 650°C for 3 hours to obtain ammonia oxidation catalyst.

[0166] Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analysis revealed that the ammonia oxidation catalyst consists of a core and a shell. The radius of the catalyst particle is defined as the distance from the center of the particle outward to the particle surface. The radius of the core is 52% of the radius of the catalyst particle (where the core radius is 12.8 μm and the catalyst particle radius is 24.6 μm). The portion extending from the surface of the core to the surface of the catalyst particle constitutes the shell. The elemental contents of the catalyst are as follows:

[0167] In the core and shell, Mo accounts for 67 wt% and 33 wt% of the total Mo in the catalyst, respectively.

[0168] In the core and shell, Bi accounts for 57 wt% and 43 wt% of the total Bi in the catalyst, respectively.

[0169] In the core and shell, Fe accounts for 35 wt% and 65 wt% of the total Fe in the catalyst, respectively.

[0170] In the core and shell, Ni accounts for 36 wt% and 64 wt% of the total Ni in the catalyst, respectively.

[0171] In the core and shell, Mg accounts for 35 wt% and 65 wt% of the total Mg in the catalyst, respectively.

[0172] In the core and shell, K accounts for 43 wt% and 57 wt% of the total K in the catalyst, respectively.

[0173] In the core and shell, the support accounts for 61 wt% and 39 wt% of the total amount of support in the catalyst, respectively.

[0174] The catalyst has a specific surface area of ​​32.0 m². 2 / g, the pore size includes two different sizes: 15nm (present in the outer shell) and 32nm (present in the core). The proportions of the two pore sizes in the total pores of the catalyst are 67% and 33% respectively, calculated by integrating the pore size distribution area.

[0175] The catalyst evaluation method is the same as in Example 1.

[0176] Catalyst evaluation results:

[0177] After 3 hours of operation, the propylene conversion rate was 97.48%, the acrylonitrile selectivity was 82.32%, and the acrylonitrile single-pass yield was 80.24%; after 500 hours of operation, the propylene conversion rate was 96.75%, the acrylonitrile selectivity was 81.74%, and the acrylonitrile single-pass yield was 79.08%.

[0178] Example 7

[0179] Preparation of ammonia oxidation catalyst:

[0180] (1) 211.9 grams of (NH4)6Mo7O 24 • 4H2O was dissolved in 200g of water at 100℃, and 23g of 600-mesh molybdenum trioxide powder and 900g of 30% silica sol were added and mixed thoroughly to obtain mixture I; 29.1g of Bi(NO3)3·5H2O was dissolved in 15g of water at 100℃ and added to mixture I. The mixture was stirred at 200 rpm for 20 min, and then nitric acid solution was added to adjust the pH to 2-3. The mixture was stirred and hydrolyzed to obtain mixture II.

[0181] (2) After heating and stirring the mixture II at 60°C for 15 min, dissolve 145.4 g Ni(NO3)2·6H2O, 80.8 g Fe(NO3)3·9H2O, 38.5 g Mg(NO3)2·6H2O and 0.84 g KNO3 in 120 g water and add them to the mixture II. Add 5 mL of 10% hexadecyltrimethylammonium bromide aqueous solution while heating and stirring. Heat and stir at 100°C for 20 min to obtain the mixed slurry III. The stirring speed in step (2) is 250 rpm.

[0182] (3) Spray dry slurry III at 350°C for 0.5 hours to obtain particulate matter. Then calcine the particulate matter in air at 600°C for 3 hours to obtain ammonia oxidation catalyst.

[0183] Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analysis revealed that the ammonia oxidation catalyst consists of a core and a shell. The radius of the catalyst particle is defined as the distance from the center of the particle outward to the particle surface. The radius of the core is 50% of the radius of the catalyst particle (where the core radius is 13.7 μm and the catalyst particle radius is 27.4 μm). The portion extending from the surface of the core to the surface of the catalyst particle constitutes the shell. The elemental contents of the catalyst are as follows:

[0184] In the core and shell, Mo accounts for 64 wt% and 36 wt% of the total Mo in the catalyst, respectively.

[0185] In the core and shell, Bi accounts for 56 wt% and 44 wt% of the total Bi in the catalyst, respectively.

[0186] In the core and shell, Fe accounts for 37 wt% and 63 wt% of the total Fe in the catalyst, respectively.

[0187] In the core and shell, Ni accounts for 36 wt% and 64 wt% of the total Ni in the catalyst, respectively.

[0188] In the core and shell, Mg accounts for 33 wt% and 67 wt% of the total Mg in the catalyst, respectively.

[0189] In the core and shell, K accounts for 42 wt% and 58 wt% of the total K in the catalyst, respectively.

[0190] In the core and shell, the support accounts for 60 wt% and 40 wt% of the total amount of support in the catalyst, respectively.

[0191] The catalyst has a specific surface area of ​​32.7 m². 2 / g, the pore size includes two different sizes: 10nm (present in the outer shell) and 31nm (present in the core). The proportions of the two pore sizes in the total pores of the catalyst are 26% and 74% respectively, calculated by integrating the pore size distribution area.

[0192] The catalyst evaluation method is the same as in Example 1.

[0193] Catalyst evaluation results:

[0194] After 3 hours of operation, the propylene conversion rate was 97.52%, the acrylonitrile selectivity was 82.20%, and the acrylonitrile single-pass yield was 80.16%; after 500 hours of operation, the propylene conversion rate was 96.73%, the acrylonitrile selectivity was 81.54%, and the acrylonitrile single-pass yield was 78.87%.

[0195] Comparative Example 1

[0196] Preparation of ammonia oxidation catalyst:

[0197] (1) 240.1 g of (NH4)6Mo7O 24 • 4H2O was dissolved in 200g of water by heating at 100℃, and 900g of silica sol with a mass fraction of 30% was added. The mixture was thoroughly mixed to obtain mixture I. 29.1g of Bi(NO3)3·5H2O was dissolved in 15g of water by heating at 100℃ and added to mixture I. The mixture was stirred at a stirring speed of 200 rpm for 20min to ensure thorough mixing and obtain mixture II.

[0198] (2) Dissolve 145.4 g Ni(NO3)2·6H2O, 80.8 g Fe(NO3)3·9H2O, 38.5 g Mg(NO3)2·6H2O and 0.84 g KNO3 in 120 g water and add them to mixture II. Add 50 mL of 10% hexadecyltrimethylammonium bromide aqueous solution while heating and stirring. Heat and stir at 100 °C for 20 min to obtain mixed slurry III. The stirring speed in step (2) is 250 rpm.

[0199] (3) Slurry III was spray-dried at 350°C for 0.5 hours to obtain particulate matter. The particulate matter was then calcined in air at 600°C for 3 hours to obtain an ammonia oxidation catalyst with the following general formula: 50wt% Mo 10 Bi 0.4 4Fe 1.5 Ni 3.7 Mg 1.1 K 0.11 O 37.6 +50wt% SiO2;

[0200] Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analysis revealed that the elemental composition of the catalyst was uniformly distributed and there was no obvious core-shell structure.

[0201] The catalyst has a specific surface area of ​​46.8 m². 2 / g, the pore size includes two different sizes, 9nm and 26nm. The proportions of the two pore sizes in the total pores of the catalyst are 59% and 41%, respectively, calculated by integrating the pore size distribution area.

[0202] The catalyst evaluation method is the same as in Example 1.

[0203] Catalyst evaluation results:

[0204] After 3 hours of operation, the propylene conversion rate was 95.67%, the acrylonitrile selectivity was 79.61%, and the acrylonitrile single-pass yield was 76.16%; after 500 hours of operation, the propylene conversion rate was 93.58%, the acrylonitrile selectivity was 78.55%, and the acrylonitrile single-pass yield was 73.51%.

[0205] The results from the above examples show that the methods for synthesizing acrylonitrile using the catalyst of the present invention in Examples 1-7 can maintain a high propylene conversion rate and acrylonitrile single-pass yield even after long-term operation.

[0206] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A core-shell type ammonia oxidation catalyst, characterized in that, The catalyst includes a support and an active component; The general formula of the active component is Mo. 10 Bi a B b C c D d O x ; B is selected from at least one of Group VIII metal elements; C is selected from at least one of alkaline earth metal elements; D is selected from at least one of alkali metal elements; a, b, c, and d represent the molar content of Bi, B, C, and D relative to Mo, respectively; the value of a ranges from 0.05 to 8.0, the value of b ranges from 0.02 to 10.0, the value of c ranges from 0.02 to 6.0, the value of d ranges from 0.05 to 5.0, and x is determined by the atomic ratio and valence state of the elements other than oxygen in the general formula of the active component; Mo exists simultaneously in the form of molybdenum trioxide and molybdate. The mesoscopic structure of the catalyst includes a core and a shell; the main components of the catalyst core include bismuth molybdate, molybdenum trioxide, and a support; the main components of the catalyst shell include molybdate and a support. Based on the total amount of molybdenum in the catalyst, the molybdenum content in the core is 60-80 wt%, and the molybdenum content in the outer shell is 20-40 wt%. Based on the total amount of support in the catalyst, the support in the core accounts for 50-65 wt% of the total amount of support in the catalyst, and the support in the outer shell accounts for 35-50 wt% of the total amount of support in the catalyst. Based on the total amount of bismuth in the catalyst, the proportion of bismuth in the core to the total amount of bismuth in the catalyst is 55-65 wt%, and the proportion of bismuth in the shell to the total amount of bismuth in the catalyst is 35-45 wt%. Based on the total amount of element B in the catalyst, the proportion of element B in the core to the total amount of element B in the catalyst is 30-45 wt%, and the proportion of element B in the shell to the total amount of element B in the catalyst is 55-70 wt%. Based on the total amount of carbon in the catalyst, the proportion of carbon in the core to the total amount of carbon in the catalyst is 30-45 wt%, and the proportion of carbon in the shell to the total amount of carbon in the catalyst is 55-70 wt%. Based on the total amount of D element in the catalyst, the proportion of D element in the core to the total amount of D element in the catalyst is 35-45 wt%, and the proportion of D element in the shell to the total amount of D element in the catalyst is 55-65 wt%. The catalyst has a specific surface area of ​​35-60 m². 2 / g; The pores with a diameter of 20-35 nm on the core account for 40-50% of the total pores in the catalyst; The pores with a diameter of 6-12 nm on the outer shell account for 50-60% of the total pores in the catalyst.

2. The catalyst according to claim 1, wherein, The value of a ranges from 0.05 to 4; and / or the value of b ranges from 0.1 to 10; and / or the value of c ranges from 0.1 to 6; and / or the value of d ranges from 0.05 to 2.

3. The catalyst according to claim 1, wherein, B is selected from at least one of iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, and platinum; and / or C is selected from at least one of magnesium, calcium, strontium, and barium; and / or D is selected from at least one of sodium, potassium, rubidium, and cesium.

4. The catalyst according to claim 3, wherein, B is at least one of iron, cobalt, and nickel; and / or C is magnesium and / or calcium; and / or D stands for potassium.

5. The catalyst according to claim 1, wherein, The radius of the catalyst particle is defined as the distance from the center of the particle outward to the particle surface. The radius of the core is 40-60% of the radius of the catalyst particle, and the portion of the core surface extending towards the particle surface is the outer shell.

6. The catalyst according to claim 1, wherein, The mass ratio of the active component to the carrier is (1.5-0.8):1; and / or The carrier includes alumina and / or silicon oxide.

7. The catalyst according to claim 6, wherein, The mass ratio of the active component to the carrier is (1.2-1.0):

1.

8. A method for preparing the catalyst according to any one of claims 1-7, characterized in that, The method includes: (1) The precursors of molybdenum, bismuth, molybdenum trioxide powder and the carrier source are mixed and contacted in solution, and then hydrolyzed and combined under acidic conditions to obtain the precursor with the core structure. (2) The precursors of the core structure, B, C, and D and the surfactant are mixed and contacted in solution, and then dried and calcined to obtain the catalyst.

9. The preparation method according to claim 8, wherein, The mass ratio of molybdenum trioxide powder to molybdenum precursor is 1:(1-30) based on the molar amount of molybdenum provided; and / or The molybdenum trioxide powder is in the α-MoO3 crystal form, with a particle size of 300-600 mesh; and / or The carrier source is selected from at least one of silica sol, alumina sol, silica-alumina molecular sieve, and silica powder; and / or The acidic conditions in step (1) are pH = 2-3; and / or The mass ratio of the surfactant to the carrier source is (0.005-0.05):1; and / or The surfactant is selected from at least one of water-soluble urea compounds, polyols, and quaternary ammonium salt surfactants.

10. The preparation method according to claim 9, wherein, The mass ratio of molybdenum trioxide powder to molybdenum precursor is 1:(3-15) based on the molar amount of molybdenum provided; and / or The surfactant includes at least one of urea, ethylene glycol, hexadecyltrimethylammonium bromide, and hexadecyltrimethylammonium chloride.

11. The use of the catalyst according to any one of claims 1-7 in the preparation of nitrile compounds from C2-C5 hydrocarbons.

12. A method for synthesizing acrylonitrile, characterized in that, The method includes, in the presence of the catalyst described in any one of claims 1-7, carrying out an ammonia oxidation reaction of propylene under a mixed gas condition containing oxygen and ammonia.

13. The synthesis method according to claim 12, wherein, The conditions for the ammonia oxidation reaction include: The oxygen-containing atmosphere is expressed as oxygen gas, and the molar ratio of propylene, oxygen-containing atmosphere, and ammonia is 1:(1.2-1.3):(9.6-10.0); and / or The reaction temperature is 420-435℃, and / or The reaction pressure is 0.06-0.14 MPa, and / or The catalyst loading for the reaction was 0.08-0.12 h⁻¹. -1 .

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