Ammonia oxidation catalysts, methods of making and using the same, and methods of synthesizing acrylonitrile from propylene and ammonia

Abstract

The application provides an ammonia oxidation catalyst, a preparation method and application thereof, and a method for synthesizing acrylonitrile by propylene ammonia oxidation, and the general formula of the active component of the catalyst is Mo 12 Bi a B b C c D d O x ; wherein 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; and the hollow rate of the catalyst is 0-5%. The catalyst has the advantages of good sphericity, few hollow particles, uniform particle size distribution, good fluidization state in a fluidized bed reactor, less catalyst loss after long-term operation, high acrylonitrile yield, low content of by-products two-carbon and propylene aldehyde, and better long-term operation stability.

Description

Technical Field

[0001] This invention belongs to the field of catalysts, and particularly relates to an ammonia oxidation catalyst, its preparation method and application, and a method for synthesizing acrylonitrile by ammonia oxidation of propylene. Background Technology

[0002] Acrylonitrile is a very important organic chemical raw material. At present, the main production process of acrylonitrile at home and abroad is the propylene ammoxidation method, that is, using propylene as raw material, acrylonitrile is synthesized in a fluidized bed reactor through ammoxidation process. The catalyst used in this process uses Mo-Bi system composite oxide as active component and silica as support to prepare catalyst with good reactivity.

[0003] CN101284237 obtained an acrylonitrile catalyst with good activity, selectivity, resistance to reduction and wear resistance by modifying the support with small molecule template agents such as tetraethylamine and tetrapropylamine and combining it with active components.

[0004] CN110562990 proposes using silica sol with a uniform particle size distribution of 20-30 nanometers, a viscosity of less than 20 cPs, a mass concentration of not less than 40%, and the addition of a stabilizer as a carrier to prepare acrylonitrile. The silica sol has a batch stability time of more than 20 minutes, exhibiting good stability and is suitable for large-scale industrial production.

[0005] CN106955717A describes a highly efficient and wear-resistant acrylonitrile catalyst prepared by adding nano-inorganic non-metallic materials such as activated clay or montmorillonite, placing dried particles in a calcination furnace, and calcining them at a constant temperature in stages. However, because the inorganic non-metallic materials used lack a stable and uniform self-structure and are difficult to disperse uniformly in the slurry, the resulting catalyst has poor particle size and structural uniformity, which is not conducive to long-term stable operation. Summary of the Invention

[0006] The technical problem to be solved by this invention is that during the operation of the catalyst, fine particles in the catalyst are lost, the overall particle size is too large, resulting in poor fluidization, reduced reaction performance, and increased by-products. The invention provides an ammonia oxidation catalyst with uniform particle size distribution, high efficiency in preparation time, and low wall adhesion loss. It has good fluidization state when used for ammonia oxidation, such as the ammonia oxidation of propylene to acrylonitrile, with high acrylonitrile yield and low carbon content in by-products.

[0007] Currently, methods to improve the stability and activity of acrylonitrile catalysts mainly focus on changing their composition, such as increasing the types of metal elements and adjusting the composition of the support.

[0008] In practical applications, it has been found that the particle size distribution and sphericity of acrylonitrile catalysts have a significant impact on their long-term operational stability. A fluidized bed reactor is a device that carries out chemical reactions of gases within a boiling bed composed of solid catalysts. During long-term operation, on the one hand, the presence of fine powder in the solid catalyst particles easily leads to particle loss under high-speed gas impact, reducing catalyst reserves; on the other hand, larger particles are also easily worn down into even finer particles within the reactor, resulting in further loss. Both factors lead to poor catalyst fluidization within the reactor, affecting catalytic activity and long-term stability, thus harming enterprise profitability. Therefore, controlling the particle size distribution of the catalyst, reducing the generation of fine powder, and maintaining the uniformity of catalyst spherical morphology are currently issues of great concern in the industry for ammonia oxidation catalysts, such as those used in acrylonitrile synthesis.

[0009] Through research, the inventors proposed that, without changing the basic elemental composition of the catalyst, by optimizing the slurry concentration and selecting a catalyst precursor slurry with a certain mesh size through screening, and by controlling the angle between the hot air outlet and the atomizer spray outlet within a certain range during the spray drying process, the hot air and spray liquid flow in parallel, and the resulting turbulence shortens the drying time. At the same time, the thickness of the catalyst lost due to adhesion to the dryer wall after spraying can also be controlled within a low range. The catalyst prepared in this way has uniform particle size distribution, high efficiency in preparation time, and low wall loss. It exhibits good fluidization state in ammonia oxidation reactions such as the ammonia oxidation of propylene to acrylonitrile, with high acrylonitrile yield and low carbon content in the byproducts.

[0010] According to a first aspect of the present invention, an ammonia oxidation catalyst is provided, wherein the active component of the catalyst has the general formula Mo. 12 Bi a B b C c D d O x Wherein, 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 10.0, the value of b ranges from 0.05 to 12.0, the value of c ranges from 0.02 to 8.0, the value of d ranges from 0.02 to 2.0, 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; the hollowness of the catalyst is 0 to 5%.

[0011] According to a second aspect of the present invention, the present invention provides a method for preparing the ammonia oxidation catalyst of the present invention, the method comprising:

[0012] (1) The active component source and the carrier source are mixed and contacted in solution, and then boiled and hydrolyzed to obtain a slurry;

[0013] (2) The slurry is spray-dried to obtain powder, and then calcined;

[0014] The conditions for spray drying include: the angle between the hot air outlet and the liquid spray outlet of the atomizer is 70° to 110°.

[0015] According to a third aspect of the invention, the application of the catalyst described herein in the ammoxidation reaction of olefins is provided.

[0016] According to a fourth aspect of the present invention, a method for synthesizing acrylonitrile by ammoxidation of propylene is provided, the method comprising contacting propylene with an ammonia source in the presence of the catalyst described in the present invention under an oxygen-containing atmosphere.

[0017] Compared with the prior art, the present invention has at least the following advantages:

[0018] (1) The catalyst of the present invention has good sphericity, few hollow particles, uniform particle size distribution, low fine particle content, less catalyst loss after long-term operation in fluidized bed reactor, good fluidization state, high yield of ammonia oxidation target product such as acrylonitrile, low carbon content of by-products, and better long-term operation stability.

[0019] (2) In the preferred embodiment, the slurry is sieved to remove larger precipitated particles before spray drying. During the spray drying process, the angle between the hot air outlet and the atomizer liquid outlet is controlled to be close to a right angle. The hot air and the spray liquid flow in parallel. The small slurry droplets at the atomizer outlet can be dried quickly and are not easy to agglomerate into large particles or form a hollow structure. The turbulence formed is used to shorten the drying time and improve the catalyst preparation efficiency.

[0020] (3) The thickness of the adhesive residue on the dryer after spraying is controlled to be relatively thin, so as to reduce the loss of catalyst fragments.

[0021] In a preferred embodiment, the catalyst of the present invention is prepared sequentially through three steps: slurry preparation, spray drying, and calcination. Before spray drying, a slurry with a solid content of 35-60% is passed through a 40-120 mesh sieve to remove larger precipitate particles. During spray drying, the angle between the hot air outlet and the atomizer spray outlet is controlled at 70°-110°, with the hot air and spray liquid flowing in parallel. The resulting turbulence shortens the drying time. After spray drying, the wall thickness on the dryer is controlled at 0-3 mm. The resulting catalyst has uniform particle size distribution and good sphericity. The scanning electron microscope (SEM) shows a hollow fraction of 0–5%, and the particle size distribution (laser particle size volume fraction) is as follows: less than 20 μm particle size content 0–1.5 vol%, 20 μm to less than 45 μm particle size content 25–60 vol%, 45 μm to less than 90 μm particle size content 35–60 vol%, and larger than 90 μm particle size content 0–10.0 vol%. The preparation time is efficient with low wall adhesion loss. It exhibits good fluidization in the ammoxidation of propylene to acrylonitrile reaction, resulting in high acrylonitrile yield and low carbon content in the byproducts. Attached Figure Description

[0022] Figure 1 The nitrogen adsorption / desorption curve of the catalyst in Example 1 of the present invention is shown.

[0023] Figure 2 The pore size distribution curve of the catalyst in Example 1 of the present invention is shown.

[0024] Figure 3 This is a scanning electron microscope (SEM) image of the catalyst of Example 1 of the present invention;

[0025] Figure 4 The infrared spectrum of pyridine adsorption of the catalyst in Example 1 of the present invention;

[0026] Figure 5 This is a schematic diagram showing the included angle between the hot air outlet of the spray dryer and the liquid spray outlet of the atomizer according to the present invention. Detailed Implementation

[0027] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0028] This invention provides an ammonia oxidation catalyst, wherein the active component of the catalyst has the general formula Mo. 12 Bi a B b C c D d O x ;in,

[0029] B is selected from at least one of the metal elements in Group VIII;

[0030] C is selected from at least one of the alkaline earth metal elements;

[0031] D is selected from at least one of the alkali metal elements;

[0032] The value of 'a' ranges from 0.05 to 10.0.

[0033] The value of b ranges from 0.05 to 12.0.

[0034] The value of c ranges from 0.02 to 8.0.

[0035] The value of d ranges from 0.02 to 2.0.

[0036] a, b, c, and d represent the molar amounts of Bi, B, C, and D relative to Mo, respectively;

[0037] x is determined by the atomic ratio and valence state of the elements other than oxygen in the general formula of the active component;

[0038] The catalyst has a hollow fraction of 0-5%.

[0039] In this invention, the catalyst has good sphericity. Scanning electron microscopy shows that the hollowness of the catalyst particles is preferably 0 to 1.0%, more preferably 0 to 0.5%.

[0040] According to one embodiment of the present invention, the catalyst includes a support, preferably the catalyst includes 45-60% by weight of the support and 40-55% by weight of the active component.

[0041] In this invention, there are no special requirements for the type of carrier. According to one embodiment of the invention, the carrier includes at least one of silicon oxide and aluminum oxide, preferably silicon dioxide; however, the invention is not limited thereto.

[0042] According to a preferred embodiment of the present invention, the catalyst particle size distribution (laser particle size volume fraction) includes: 0-1.5 vol% of particles smaller than 20 μm, preferably 0.05-1.4 vol%; 25-60 vol% of particles from 20 μm to less than 45 μm, preferably 35-55 vol%; 35-60 vol% of particles from 45 μm to less than 90 μm, preferably 45-50 vol%; and 0-10.0 vol% of particles larger than 90 μm, preferably 0.5-6 vol%.

[0043] According to a preferred embodiment of the present invention, the catalyst has a specific surface area of ​​25–50 m². 2 / g, preferably 35-45m 2 / g.

[0044] According to a preferred embodiment of the present invention, the most probable pore size of the catalyst is 5-20 nm, preferably 8-12 nm.

[0045] In this invention, the catalyst has good wear resistance. After a 20-hour wear test, the wear index of the catalyst is 0.2% to 1.5%, preferably 0.6% to 1.0%.

[0046] According to a preferred embodiment of the present invention, the catalyst, as determined by pyridine infrared adsorption, has an L acid site located at 1445 cm⁻¹. -1 ~1455cm -1 The Brønsted acid site is located at 1535 cm⁻¹ -1 ~1545cm -1 between.

[0047] This invention does not impose special requirements on the preparation method of the catalyst; as long as the aforementioned characteristics are met, the purpose of this invention can be achieved. According to a preferred embodiment of this invention, a method for preparing an ammonia oxidation catalyst is provided, the method comprising:

[0048] (1) The active component source and the carrier source are mixed and contacted in solution, and then boiled and hydrolyzed to obtain a slurry;

[0049] (2) The slurry is spray-dried to obtain powder, and then calcined;

[0050] The conditions for spray drying include: the angle between the hot air outlet and the liquid outlet of the atomizer (e.g., Figure 5 The included angle shown is 70° to 110°, preferably 80° to 100°.

[0051] According to a preferred embodiment of the present invention, step (1) preferably includes:

[0052] a) Dissolve the Mo-containing source by heating and mix it thoroughly with the support source;

[0053] b) Dissolve the Bi, B, C, and D sources by heating, and add them to the mixture from step a). Stir until homogeneous to obtain a mixed slurry. The Mo and carrier sources are alkaline, while the Bi and other sources are acidic. Dissolving them separately can prevent precipitation due to acid-base reactions during the raw material dissolution process, which would lead to uneven composition in the slurry.

[0054] In this invention, the active source is a water-soluble salt containing an active metal element, such as a Mo source being a Mo-containing oxyacid ammonium salt, preferably (NH4)6Mo7O. 24 Or its hydrate. The remaining Bi, B, C, and D sources are preferably one or more of halides, alkoxides, nitrates, or acetates, with nitrates being preferred, such as bismuth nitrate, ferric nitrate, nickel nitrate, magnesium nitrate, etc. This is merely illustrative and should not be construed as limiting the invention to this scope.

[0055] According to a preferred embodiment of the present invention, preferably, the thickness of the slurry adhering to the wall of the dryer after spray drying is controlled to be 0-3 mm, preferably 0-2 mm.

[0056] According to a preferred embodiment of the present invention, the conditions for spray drying preferably include: the heat source being air, and / or the drying temperature being 300-420°C, preferably 320-400°C; and / or the drying time being 0.5-3.0h, preferably 0.5-1.0h; and / or the average diameter of the spray droplets being 30-150μm, preferably 30-120μm.

[0057] In this invention, controlling the thickness of the slurry adhering to the wall after spraying can reduce the loss of raw materials and lower production costs. Appropriate drying time and temperature can achieve rapid and efficient drying. Controlling the particle size of the spray droplets can ensure that the particle size of the final product is within the reasonable range required by this invention, making it particularly suitable for fluidized bed reactors.

[0058] In this invention, the carrier source has no special requirements and can be selected according to the carrier. The carrier source is silica sol or a mixture of silica / alumina. According to a preferred embodiment of the present invention, the carrier source is selected from silica sol with a mass concentration of 30% to 40%.

[0059] According to a preferred embodiment of the present invention, the conditions for contact in step (1) in the solution state include: the conditions for mixed contact include: a temperature of 30 to 80°C.

[0060] According to a preferred embodiment of the present invention, the contact in step (1) is carried out in the presence of an additive; the additive is selected from one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, hexadecyltrimethylammonium bromide (CTAB), polyethylene glycol, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123), and polyether F127, preferably selected from one or more of sodium dodecyl sulfate, CTAB, polyethylene glycol, and P123, more preferably a mixture of CTAB and P123, wherein the weight ratio of the two is 5.0-1.0:1.

[0061] According to a preferred embodiment of the present invention, preferably, the mass concentration of the additive in step (1) a) of the solution is 2.0-10.0 g / L.

[0062] According to a preferred embodiment of the present invention, the conditions for hydrolysis and boiling include: time 10 to 30 min; and / or temperature 110 to 160 °C, preferably 125 to 150 °C; and / or stirring speed 150 to 250 rpm.

[0063] According to a preferred embodiment of the present invention, the solid content of the slurry in step (1) is 30-60 wt%, preferably 40-55 wt%.

[0064] According to a preferred embodiment of the present invention, before step (2), the slurry is sieved through a 40-120 mesh, preferably 80-100 mesh, sieve to remove precipitated particles. The solid content after sieving is preferably 42-50 wt%. Sieving the slurry and maintaining a certain solid content avoids large particles generated during the boiling process from affecting the subsequent spray drying and clogging of the atomizing disc. This can effectively improve drying efficiency, reduce the loss of large particles adhering to the wall during spraying, and maintain the uniformity of catalyst particle size.

[0065] In this invention, there are no special requirements for the calcination conditions. According to one embodiment of the invention, the calcination conditions include: being carried out in an oxygen-containing atmosphere, and / or a calcination temperature of 400–700°C, preferably 450–640°C; and / or a calcination time of 3–8 hours, preferably 4–6 hours. However, the invention is not limited to these conditions.

[0066] This invention provides the application of the catalyst described herein in the ammoxidation reaction of olefins, wherein the olefins are selected from one or more of propylene and isobutylene.

[0067] This invention provides a method for synthesizing acrylonitrile by ammoxidation of propylene, the method comprising contacting propylene with an ammonia source in the presence of the catalyst described in this invention under an oxygen-containing atmosphere.

[0068] This invention does not have special requirements for ammonia oxidation conditions; commonly used ammonia oxidation conditions can be used in this invention. In one embodiment of this invention, the ammonia source is selected from ammonia gas.

[0069] According to one embodiment of the present invention, the oxygen-containing atmosphere is one or more of air, oxygen, or a mixture of oxygen and an inert gas.

[0070] According to one embodiment of the present invention, the contact is carried out in a fluidized bed reactor.

[0071] According to one embodiment of the present invention, the contact conditions include a molar ratio of propylene, ammonia source (calculated as ammonia gas), and oxygen-containing atmosphere (calculated as oxygen content) of 1:1.1-1.3:9.5-10.0.

[0072] According to one embodiment of the present invention, the temperature is 420–440°C, the pressure (gauge pressure) is 0.06–0.12 MPa, and the catalyst loading is 0.08–0.12 h⁻¹. -1 The roasting conditions described in this invention are merely illustrative and should not be construed as limiting the invention to that scope.

[0073] According to a preferred embodiment of the present invention, the method for preparing the catalyst further includes the following specific steps:

[0074] a) The precursor containing the active component of Mo is dissolved by heating and thoroughly mixed with the carrier source;

[0075] b) The active component precursor containing metals such as Bi, B, C, and D is heated and dissolved, and then added to the mixture in step a) and stirred evenly to obtain a mixed slurry.

[0076] c) The slurry obtained in step b) is heated and boiled, and then sieved to remove larger sediment particles;

[0077] d) The slurry is spray-dried to obtain powder, which is then calcined in an oxygen-containing atmosphere.

[0078] Further, in steps a) and b), the active source is a water-soluble salt containing an active metal element, for example, the Mo source is a Mo-containing oxyacid ammonium salt, preferably (NH4)6Mo7O. 24 Or its hydrate. The remaining Bi, B, C and D sources are preferably one or more of halides, alkoxides, nitrates or acetates, with nitrates being preferred, such as bismuth nitrate, ferric nitrate, nickel nitrate, magnesium nitrate, etc.

[0079] Furthermore, in steps a) and b), the dissolution temperature is 30–80°C.

[0080] Further, in step a), the precursor of the carrier is a silica sol or a silica / alumina mixed carrier, preferably a silica sol.

[0081] Further, in step c), the heating and boiling conditions are: time 10-30 min, temperature 110-160℃, preferably 125-150℃, and stirring speed 150-250 rpm.

[0082] Further, in step c), the sieving step uses a sieve mesh size of 40 to 120 mesh, preferably 80 to 100 mesh.

[0083] Further, in step d), the angle between the hot air outlet and the liquid spray outlet of the atomizer is controlled to be 70° to 110°, preferably 80° to 100°, during the spray drying process.

[0084] Further, in step d), the heat source for spray drying is air, the drying temperature is 300-420℃, preferably 320-400℃, the drying time is 0.5-3.0h, preferably 0.5-1.0h, and the average diameter of the spray droplets is 30-150μm, preferably 30-120μm.

[0085] Further, in step d), the thickness of the catalyst adhering to the wall of the dryer after spray drying is 0-3 mm, preferably 0-2 mm.

[0086] Further, in step d), the calcination conditions are: calcination in an oxygen-containing atmosphere, such as calcination in an air atmosphere; calcination temperature is 400-700℃, preferably 450-640℃, and calcination time is 3-8h, preferably 4-6h.

[0087] The specific application is as follows: in the presence of the acrylonitrile catalyst, propylene undergoes an ammoxidation reaction to produce acrylonitrile in the presence of ammonia and oxygen.

[0088] Specific reaction conditions include: a molar ratio of propylene / ammonia / air (based on oxygen content) of 1:1.1–1.3:9.5–10.0; a reaction temperature of 420–440℃; a reaction pressure (gauge pressure) of 0.06–0.12 MPa; and a catalyst loading of 0.08–0.12 h⁻¹. -1 .

[0089] The catalyst of the present invention has good sphericity, and scanning electron microscopy shows that the hollowness is 0-0.5%. The particle size distribution range (laser particle size volume fraction) is as follows: less than 20 μm particle size content 0-1.5 vol%, 20 μm to less than 45 μm particle size content 25-60 vol%, 45 μm to less than 90 μm particle size content 35-60 vol%, and larger than 90 μm particle size content 0-10.0 vol%.

[0090] In this invention, the particle size distribution of the catalyst is measured using a Mastersizer2000 particle size analyzer.

[0091] In this invention, the hollowness ratio of the catalyst particles, i.e. the proportion of catalyst particles with central cavities to all particles, is obtained by observation and calculation using a scanning electron microscope (SEM).

[0092] In this invention, the specific surface area and pore size are measured using a Tristar physical adsorption instrument. Before testing, the samples undergo heating and vacuum degassing. Porosity was measured at 77 K, and the specific surface area was calculated using the Brunauer-Emmett-Teller (BET) method. The pore size distribution and pore volume can be calculated from the isothermal adsorption branch using the Barrettner-Joyner-Halenda (BJH) model.

[0093] In this invention, the Fourier transform pyridine adsorption infrared (FT-IR) spectroscopy used is a Nicolet Fourier spectrophotometer manufactured in the United States.

[0094] The catalyst attrition index measuring device used in this invention is an attrition device manufactured by Beijing Huier Sanji Green Chemistry Technology Co., Ltd., and the attrition index determination method is as follows:

[0095] (1) About 10 grams of catalyst with a 200-300 mesh sieve was used to determine the wear index;

[0096] (2) At room temperature and standard atmospheric pressure, purge the reaction tube containing the catalyst by passing air at a flow rate of 10 L / min.

[0097] (3) Weigh the catalyst collection bag when the cumulative purging time is 1h and 20h respectively, and calculate the catalyst wear index.

[0098] Excluding the fine powder lost during the first hour of catalyst runoff, the abrasion index is calculated as follows:

[0099] (Weight of the 20h collection bag - weight of the 1h collection bag) / weight of the catalyst packed in the reaction tube * 100%

[0100] In this invention, gas chromatography is used for online analysis of the product gas. The conversion rate of propylene, the selectivity of acrylonitrile, and the single-pass yield are used as indicators to evaluate the catalyst performance. The definitions of these two parameters are as follows:

[0101] Acrylonitrile conversion rate (%) = (moles of propylene reacted / moles of propylene fed) × 100%

[0102] Acrylonitrile selectivity (%) = (moles of acrylonitrile produced / moles of propylene reacted) × 100%

[0103] Acrylonitrile single-pass yield (%) = (moles of acrylonitrile produced / moles of propylene fed) × 100%

[0104] In this invention, the catalyst composition is based on the amount of raw materials fed.

[0105] Example 1

[0106] 84.6 grams of (NH4)6Mo7O 24• 4H₂O was dissolved in hot water, and 250 g of 40% silica sol was added and mixed thoroughly to obtain solution I. 15.5 g of Bi(NO₃)₃·5H₂O, 55.7 g of Ni(NO₃)₂·6H₂O, 32.2 g of Fe(NO₃)₃·9H₂O, 16.4 g of Mg(NO₃)₂·6H₂O, and 0.45 g of KOH were dissolved and thoroughly mixed at 70°C to obtain solution II, which was then added to solution I. The mixture was heated at 135°C for 20 min with a stirring speed of 220 rpm to obtain mixed slurry III (solid content 52 wt%). The slurry was sieved through a 100-mesh sieve to remove large particles; the solid content after sieving was 49 wt%. Spray drying was performed by controlling the angle between the hot air outlet and the atomizer spray outlet to 90° (e.g., ...). Figure 5 As shown), the average diameter of the spray droplets was 50 μm, the heat source was air, the drying temperature was 350℃, and the drying time was 0.5 hours, resulting in powder with a wall adhesion thickness of 0–1.5 mm. The particles were calcined in air at 600℃ for 4 hours to obtain acrylonitrile catalyst A, whose general formula is as follows:

[0107] 50% Mo 12 Bi 0.8 Fe 2.0 Ni 4.8 Mg 1.6 K 0.2 O 46.7 +50% SiO2,

[0108] The catalyst has a particle size distribution of 0.6% (smaller than 20 μm), 47.6% (20 μm–45 μm), 48.7% (45 μm–90 μm), and 3.1% (larger than 90 μm); its specific surface area is 40.2 m². 2 / g, with a most probable pore size of 10.8nm ( Figure 1 , Figure 2 The wear index is 0.82%. Figure 4 The infrared pyridine spectrum of the catalyst shows that the characteristic absorption peaks of pyridine adsorbing infrared L acid and Brønsted acid are located at 1450 cm⁻¹. -1 1539cm -1 Place. Figure 3 The image shows a SEM image of the catalyst of this invention. From the image, it can be observed and calculated that the hollow fraction of the catalyst is 0.35%.

[0109] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the above catalyst are as follows:

[0110] In a millimeter-scale fluidized bed reactor, the reaction conditions were: reaction temperature: 420℃; reaction pressure: 0.085 MPa; catalyst loading: 300 g; catalyst propylene loading (WWH): 0.12 h. -1Raw material ratio (molar): C3 ＝ / NH3 / air = 1 / 1.25 / 9.6. Propylene conversion rate is 99.25%, acrylonitrile selectivity is 83.70%, and acrylonitrile single-pass yield is 83.07%.

[0111] Example 2

[0112] 92.4 grams of (NH4)6Mo7O 24 • 4H₂O was dissolved in hot water, and 230 g of 40% silica sol was added and mixed thoroughly to obtain solution I. 21.2 g of Bi(NO₃)₃·5H₂O, 50.7 g of Ni(NO₃)₂·6H₂O, 35.2 g of Fe(NO₃)₃·9H₂O, 13.4 g of Mg(NO₃)₂·6H₂O, and 0.49 g of KOH were dissolved and thoroughly mixed at 70°C to obtain solution II, which was then added to solution I. The mixture was heated at 140°C with a stirring speed of 220 rpm for 20 min to obtain mixed slurry III (solid content 53 wt%). The slurry was sieved through a 100-mesh sieve to remove large precipitates; the solid content after sieving was 48 wt%. Spray drying was performed with the hot air outlet and the atomizer spray outlet at a 90° angle. The average diameter of the spray droplets was 60 μm. The heat source was air, the drying temperature was 350℃, and the drying time was 0.5 hours, yielding a powder with a wall adhesion thickness of 0–1.8 mm. The particles were calcined in air at 600℃ for 4 hours to obtain acrylonitrile catalyst B, whose general formula is as follows:

[0113] 54% Mo 12 Bi 1.0 Fe 2.0 Ni 4.0 Mg 1.2 K 0.2 O 45.8 +46% SiO2,

[0114] The catalyst has a particle size distribution of 0.5% (smaller than 20 μm), 48.2% (20 μm–45 μm), 47.8% (45 μm–90 μm), and 3.5% (larger than 90 μm); its specific surface area is 38.7 m². 2 / g, most probable pore size is 11nm; abrasion index is 0.85%; the characteristic absorption peaks of pyridine adsorption for L acid and Brønsted acid are located at 1449cm. -1 1540cm -1 At that location, the hollow fraction of the catalyst is 0.45%.

[0115] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the above catalyst were the same as in Example 1, with a propylene conversion rate of 99.18%, an acrylonitrile selectivity of 83.72%, and an acrylonitrile single-pass yield of 83.03%.

[0116] Example 3

[0117] 84.6 grams of (NH4)6Mo7O 24 • 4H₂O was dissolved in hot water, and 250 g of 40% silica sol was added and mixed thoroughly to obtain solution I. 15.5 g of Bi(NO₃)₃·5H₂O, 55.7 g of Ni(NO₃)₂·6H₂O, 32.2 g of Fe(NO₃)₃·9H₂O, 16.4 g of Mg(NO₃)₂·6H₂O, and 0.45 g of KOH were dissolved and thoroughly mixed at 70°C to obtain solution II, which was then added to solution I. The mixture was heated at 150°C for 20 min with a stirring speed of 180 rpm to obtain mixed slurry III (solid content 50 wt%). The slurry was sieved through an 80-mesh sieve to remove large precipitates; the solid content after sieving was 47 wt%. Spray drying was performed with the angle between the hot air outlet and the atomizer spray outlet controlled at 85°. The average diameter of the spray droplets was 80 μm. The heat source was air, the drying temperature was 350℃, and the drying time was 0.5 hours, resulting in powder with a wall adhesion thickness of 0–1.6 mm. The particles were calcined in air at 580℃ for 4 hours to obtain acrylonitrile catalyst C, whose general formula is as follows:

[0118] 50% Mo 12 Bi 0.8 Fe 2.0 Ni 4.8 Mg 1.6 K 0.2 O 46.7 +50% SiO2,

[0119] The catalyst has a particle size distribution of 0.8% (smaller than 20 μm), 49.0% (20 μm–45 μm), 48.2% (45 μm–90 μm), and 2.0% (larger than 90 μm); its specific surface area is 38.5 m². 2 / g, with a most probable pore size of 11.2nm; an abrasion index of 0.78%; and characteristic absorption peaks of pyridine adsorbed on L and Brønsted acids at 1447cm⁻¹. -1 1543cm -1 At that location, the hollow fraction of the catalyst is 0.42%.

[0120] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the above catalyst were the same as in Example 1, with a propylene conversion rate of 99.1%, an acrylonitrile selectivity of 83.59%, and an acrylonitrile single-pass yield of 82.84%.

[0121] Example 4

[0122] The catalyst was prepared according to the method of Example 1, except that it was spray-dried directly without sieving, while the other conditions remained the same. The thickness of the powder adhering to the wall after spray drying reached more than 3.0 mm.

[0123] The catalyst contains 0.1% particles smaller than 20 μm, 38.7% particles between 20 μm and 45 μm, 50.2% particles between 45 μm and 90 μm, and 11.0% particles larger than 90 μm; its specific surface area is 27.5 m². 2 / g, most probable pore size is 18.0nm; abrasion index is 2.45%; the characteristic absorption peaks of pyridine adsorption for L acid and Brønsted acid are located at 1448cm⁻¹. -1 1542cm -1 At that location, the hollowness of the catalyst is 2.53%.

[0124] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the above catalyst were the same as in Example 1, with a propylene conversion rate of 98.23%, an acrylonitrile selectivity of 82.56%, and an acrylonitrile single-pass yield of 81.10%.

[0125] Example 5

[0126] The catalyst was prepared according to the method in Example 1, except that the angle between the hot air outlet and the liquid spray outlet of the atomizer was controlled at 75° during spray drying, while other conditions remained unchanged. The powder adhered to the wall thickness after spray drying reached more than 3.5 mm.

[0127] The catalyst has a particle size distribution of 0.2% (smaller than 20 μm), 42.8% (20 μm–45 μm), 49.5% (45 μm–90 μm), and 7.5% (larger than 90 μm); its specific surface area is 30.2 m². 2 / g, with a most probable pore size of 16.3nm; an abrasion index of 1.85%; and characteristic absorption peaks of pyridine adsorbed on L and Brønsted acids at 1450cm⁻¹. -1 1542cm -1 At that location, the hollowness of the catalyst was 3.20%.

[0128] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the above catalyst were the same as in Example 1, with a propylene conversion rate of 99.02%, an acrylonitrile selectivity of 83.36%, and a single-pass yield of 82.54%.

[0129] Example 6

[0130] The method was followed as in Example 1, except that after adding the carrier to obtain solution I, the surfactant hexadecyltrimethylammonium bromide (CTAB, with a surfactant concentration of 3.6 g / L in solution I) was added and stirred for mixing, while the other conditions remained unchanged. The powder wall thickness after spray drying was 0–1.2 mm.

[0131] The catalyst contains 1.1% particles smaller than 20 μm, 50.6% particles between 20 μm and 45 μm, 47.4% particles between 45 μm and 90 μm, and 0.9% particles larger than 90 μm; its specific surface area is 42.5 m². 2 / g, most probable pore size is 9.3nm; abrasion index is 0.62%; the characteristic absorption peaks of pyridine adsorption for L acid and Brønsted acid are located at 1448cm⁻¹. -1 1541cm -1 At that location, the hollow fraction of the catalyst is 0.20%.

[0132] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the above catalyst were the same as in Example 1, with a propylene conversion rate of 99.43%, an acrylonitrile selectivity of 84.15%, and an acrylonitrile single-pass yield of 83.67%.

[0133] Example 7

[0134] The method was followed as in Example 1, except that after adding the carrier to obtain solution I, surfactants CTAB and P123 (the mass ratio of CTAB to P123 was 2:1, and the mass concentration of the surfactant in solution I was 3.6 g / L) were added and stirred. All other conditions remained unchanged. The powder adherence thickness to the wall after spray drying was 0–1.0 mm.

[0135] The catalyst contains 1.4% particles smaller than 20 μm, 51.2% particles between 20 μm and 45 μm, 47.0% particles between 45 μm and 90 μm, and 0.4% particles larger than 90 μm; its specific surface area is 44.2 m². 2 / g, most probable pore size is 8.5nm; abrasion index is 0.40%; the characteristic absorption peaks of pyridine adsorption for L acid and Brønsted acid are located at 1447cm. -1 1540cm -1 At that location, the hollowness of the catalyst is 0.15%.

[0136] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the above catalyst were the same as in Example 1, with a propylene conversion rate of 99.56%, an acrylonitrile selectivity of 84.49%, and a single-pass yield of 84.11%.

[0137] Example 8

[0138] The method was followed in Example 1, except that the slurry was heated at 120°C for 30 minutes to obtain mixed slurry III. The thickness of the powder adhering to the wall after spray drying was 0–1.6 mm.

[0139] The catalyst contains 0.5% particles smaller than 20 μm, 43.2% particles between 20 μm and 45 μm, 49% particles between 45 μm and 90 μm, and 7.3% particles larger than 90 μm; its specific surface area is 35.4 m². 2 / g, with a most probable pore size of 12.2nm; an abrasion index of 0.94%; and characteristic absorption peaks of pyridine adsorbed on L and Brønsted acids at 1449cm⁻¹. -1 1539cm -1 At that location, the hollow fraction of the catalyst is 0.59%.

[0140] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the above catalyst were the same as in Example 1, with a propylene conversion rate of 98.85%, an acrylonitrile selectivity of 83.02%, and an acrylonitrile single-pass yield of 82.07%.

[0141] Comparative Example 1

[0142] The catalyst was prepared according to the method of Example 1, except that the spray drying process was carried out at a 60° angle between the hot air outlet and the atomizer spray outlet, while all other conditions remained unchanged. After spray drying, the powder adhered to the wall thickness of more than 5.5 mm. The catalyst had a particle size distribution of 0% (smaller than 20 μm), 32.6% (20 μm–45 μm), 52.1% (45 μm–90 μm), and 15.3% (larger than 90 μm); the specific surface area was 25.2 m². 2 / g, with a most probable pore size of 19.1nm; an abrasion index of 5.60%; and characteristic absorption peaks of pyridine adsorption for L and Brønsted acids located at 1448cm⁻¹. -1 1541cm -1 At that location, the hollowness of the catalyst is 6.5%.

[0143] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the above catalyst were the same as in Example 1, with a propylene conversion rate of 97.33%, an acrylonitrile selectivity of 81.58%, and a single-pass yield of 79.40%.

[0144] Comparative Example 2

[0145] 97.3 grams of (NH4)6Mo7O 24• 4H2O was dissolved in water upon heating, and 350 g of silica sol with a mass fraction of 30% was added to obtain material I. 9.6 g of Bi(NO3)3·5H2O, 49.7 g of Ni(NO3)2·6H2O, 30.2 g of Fe(NO3)3·9H2O, and 16.2 g of Mg(NO3)2·6H2O were dissolved in water and added to material I to obtain mixed slurry II. 14.0 g of urea was weighed, dissolved in water, and added to mixed slurry II. The mixture was stirred at 300 rpm for 0.5 hours at 100°C to obtain a slurry. The slurry was spray-dried at 350°C for 0.5 hours, with the angle between the hot air outlet and the atomizer spray outlet controlled at 50°, to obtain particulate matter. The particulate matter was calcined at 600°C in air for 3 hours to obtain an acrylonitrile catalyst with the following general formula:

[0146] 50% Mo 12.00 Bi 0.43 Fe 1.63 Ni 3.72 Mg 1.38 O 44.18 +50% SiO2

[0147] The catalyst contains 0.1% particles smaller than 20 μm, 36.2% particles between 20 μm and 45 μm, 55.3% particles between 45 μm and 90 μm, and 8.4% particles larger than 90 μm; its specific surface area is 22.0 m². 2 / g, most probable pore size is 20.7nm; abrasion index is 6.2%; characteristic absorption peaks of pyridine adsorption for L and Brønsted acids are located at 1450cm⁻¹. -1 1542cm -1 At this location, the hollowness of the catalyst is 5.57%. After spray drying, the thickness of the powder adhering to the wall is over 6.2 mm.

[0148] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the above catalyst were the same as in Example 1, with a propylene conversion rate of 97.06%, an acrylonitrile selectivity of 81.31%, and a single-pass yield of 78.92%.

[0149] 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 specific technical features in any suitable manner. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. However, 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. An ammonia oxidation catalyst, characterized in that, The general formula of the active component of this catalyst is Mo. 12 Bi a B b C c D d O x ;in, B is selected from at least one of the metal elements in Group VIII; C is selected from at least one of the alkaline earth metal elements; D is selected from at least one of the alkali metal elements; The value of 'a' ranges from 0.05 to 10.

0. The value of b ranges from 0.05 to 12.

0. The value of c ranges from 0.02 to 8.

0. The value of d ranges from 0.02 to 2.

0. a, b, c, and d represent the molar amounts of Bi, B, C, and D relative to Mo, respectively; x is determined by the atomic ratio and valence state of the elements other than oxygen in the general formula of the active component; The hollow fraction of the catalyst is 0-5%; The catalyst particle size distribution includes: Particle size less than 20μm content: 0~1.5% by volume; Particle size content of 20μm to less than 45μm: 25-60% by volume; 35-60% by volume of particles with a diameter of 45 μm to less than 90 μm. Particle size greater than 90μm content: 0~10.0% by volume; The catalyst has a specific surface area of ​​25-50 m². 2 / g.

2. The catalyst according to claim 1, wherein, The catalyst has a hollow fraction of 0~1.0%; The catalyst includes a support, and the catalyst comprises 45-60% by weight of the support and 40-55% by weight of the active component; and / or The catalyst particle size distribution includes: The content of particles smaller than 20 μm is 0.05~1.4% by volume; Particle size content of 20μm to less than 45μm: 35-55% by volume; 45-50% by volume of particles with a diameter of 45 μm to less than 90 μm. Particle size greater than 90μm: 0.5~6% by volume; and / or The catalyst has a specific surface area of ​​35~45m². 2 / g, with most probable pore sizes of 5~20nm; The wear index of the catalyst is 0.2%~1.5%; The L acid site of the catalyst is located at 1445 cm⁻¹. -1 ~1455cm -1 Between, the Brønsted acid site is located at 1535 cm. -1 ~1545cm -1 between.

3. The catalyst according to claim 1, wherein, The catalyst has a hollow fraction of 0~0.5%; The carrier includes at least one of silicon oxide and aluminum oxide; and / or The catalyst has a most probable pore size of 8~12 nm; The wear index of the catalyst is 0.6%~1.0%.

4. The catalyst according to claim 3, wherein, The carrier includes silicon dioxide.

5. A method for preparing the ammonia oxidation catalyst according to any one of claims 1-4, characterized in that, The method includes: (1) The active component source and the carrier source are mixed and contacted in solution, and then boiled and hydrolyzed to obtain a slurry; (2) The slurry is spray-dried to obtain powder, and then calcined; The conditions for spray drying include: the angle between the hot air outlet and the liquid spray outlet of the atomizer is 70°~110°.

6. The preparation method according to claim 5, wherein, The angle between the hot air outlet and the liquid spray outlet of the atomizer is 80°~100°.

7. The preparation method according to claim 5, wherein, The thickness of the slurry adhering to the wall of the dryer after spray drying is controlled to be 0~3mm.

8. The preparation method according to claim 7, wherein, The thickness of the slurry adhering to the wall of the dryer after spray drying is controlled to be 0~2mm.

9. The preparation method according to claim 5, wherein, The conditions for spray drying include: The heat source is air, and / or The drying temperature is 300-420℃; and / or Drying time: 0.5-3.0 h; and / or The average diameter of the spray droplets is 30-150 μm.

10. The preparation method according to claim 9, wherein, The conditions for spray drying include: The drying temperature is 320~400℃; and / or Drying time: 0.5~1.0 h; and / or The average diameter of the spray droplets is 30~120μm.

11. The preparation method according to claim 5, wherein, The conditions for contact in the solution state in step (1) include: The carrier source is selected from silica sol with a mass concentration of 30%~40%; and / or Conditions for mixed contact include: temperature 30~80℃; and / or The contact in step (1) is carried out in the presence of an additive; the additive is selected from one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, hexadecyltrimethylammonium bromide, polyethylene glycol, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, and polyether F127; The conditions for hydrolysis and boiling include: time 10~30 min; and / or temperature 110~160℃; and / or stirring speed 150~250 rpm.

12. The preparation method according to claim 11, wherein, The additive is selected from one or more of sodium dodecyl sulfate, CTAB, polyethylene glycol, and P123.

13. The preparation method according to claim 12, wherein, The additive is a mixture of CTAB and P123 in a weight ratio of 5.0-1.0:

1.

14. The preparation method according to claim 11, wherein, The mass concentration of the additive in step a) is 2.0-10.0 g / L solution.

15. The preparation method according to claim 11, wherein, The conditions for hydrolysis and boiling include a temperature of 125~150℃.

16. The preparation method according to claim 5, wherein, The solid content of the slurry in step (1) is 30~60 wt%; Before step (2), the slurry is sieved through a 40-120 mesh screen to remove precipitated particles, and the solid content after sieving is 42-50 wt%.

17. The preparation method according to claim 16, wherein, The solid content of the slurry in step (1) is 40~55wt%; Before step (2), the slurry is sieved with an 80-100 mesh screen to remove precipitated particles.

18. The preparation method according to claim 5, wherein, The calcination conditions include: being carried out in an oxygen-containing atmosphere, and / or a calcination temperature of 400~700℃; and / or a calcination time of 3~8h.

19. The preparation method according to claim 18, wherein, The calcination conditions include: a calcination temperature of 450~640℃; and / or a calcination time of 4~6h.

20. The use of the catalyst according to any one of claims 1-4 in the ammoxidation reaction of olefins, wherein the olefin is selected from one or more of propylene and isobutylene.

21. A method for synthesizing acrylonitrile by ammoxidation of propylene, characterized in that, The method includes contacting propylene with an ammonia source in an oxygen-containing atmosphere in the presence of the catalyst described in any one of claims 1-4.

22. The method according to claim 21, wherein, The conditions for contact include: The ammonia source is selected from ammonia gas; The oxygen-containing atmosphere is one or more of air, oxygen, or a mixture of oxygen and an inert gas; and / or The contact takes place in a fluidized bed reactor; and / or The contact conditions include a molar ratio of propylene, ammonia source (based on ammonia gas), and oxygen-containing atmosphere (based on the oxygen content) of 1:1.1~1.3:9.5~10.

0. The temperature was 420~440℃, the gauge pressure was 0.06~0.12MPa, and the catalyst loading was 0.08~0.12 h⁻¹. -1 .

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