Ammonia oxidation catalyst, preparation method and application thereof, and method for synthesizing acrylonitrile through propylene ammoxidation

Abstract

The invention provides an ammoxidation catalyst, a preparation method and application thereof and a method for synthesizing acrylonitrile through propylene ammoxidation. The general formula of an active component of the catalyst is Mo12BiaBbCcDdOx, wherein B is selected from at least one of VIII group 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; the hollow rate of the catalyst is 0-5%. The catalyst provided by the invention has the advantages of good sphericity, less 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 of two carbons and acrolein, and better long-term operation stability.

Description

Technical Field

[0001] The invention belongs to the field of catalysts, and in particular relates to an ammoxidation catalyst, a preparation method and application thereof, and a method for synthesizing acrylonitrile by ammoxidation of propylene. Background Art

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

[0003] CN101284237 obtains an acrylonitrile catalyst with good activity, selectivity, reduction resistance and wear resistance by modifying a carrier with small molecule template agents such as tetraethylamine and tetrapropylamine and compounding them with active components.

[0004] CN110562990 proposes to use silica sol with a particle size uniformly distributed between 20 and 30 nanometers, a viscosity less than 20 cPs, a mass concentration not less than 40%, and an added stabilizer as a carrier to prepare acrylonitrile. The silica sol has a stability time of more than 20 minutes, has good stability, and is suitable for large-scale industrial production.

[0005] CN106955717A prepares a high-efficiency, wear-resistant acrylonitrile catalyst by adding nano inorganic non-metallic materials such as activated clay or montmorillonite, placing the dried particles in a calcining furnace and calcining and molding them under the condition of maintaining a uniform temperature rise to a certain temperature in stages. However, since the inorganic non-metallic materials used do not have a stable and uniform structure of their own and are difficult to disperse evenly in the slurry, the particle size and structural uniformity of the catalyst finally prepared are poor, which is not conducive to long-term stable operation. Summary of the invention

[0006] The technical problem to be solved by the present 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 a poor fluidization state, reduced reaction performance, and an increase in by-products. An ammoxidation catalyst is provided, which has uniform particle size distribution, high preparation time efficiency, and less wall adhesion loss. The catalyst is used for ammoxidation, such as propylene ammoxidation to acrylonitrile, has a good fluidization state, a high acrylonitrile yield, and a low carbon content of by-products.

[0007] At present, the methods for improving the stability and activity of acrylonitrile catalysts mainly focus on changes in their components, such as increasing the types of metal elements, adjusting the carrier composition, etc.

[0008] In actual applications, it is found that factors such as the particle size distribution and sphericity of acrylonitrile catalysts have an important influence on their long-term operating stability. A fluidized bed reactor is a device that conducts a chemical reaction of gas in a boiling bed composed of solid catalysts. During long-term operation, on the one hand, due to the presence of fine powder in the solid catalyst particles, the fine particles are easily damaged under the impact of high-speed gas, and the catalyst reserves are reduced; on the other hand, larger particles are also easily worn into smaller particles in the reactor and thus damaged. These two factors lead to poor fluidization of the catalyst in the reactor, affecting the catalytic activity and long-term stability, and damaging the company's benefits. Therefore, controlling the particle size distribution of the catalyst, reducing the generation of fine powder, and maintaining the uniformity of the catalyst's spherical morphology are issues that the industry is more concerned about in the current production process of ammonia oxidation catalysts such as acrylonitrile synthesis catalysts.

[0009] After research, the inventors proposed that, without changing the basic element components of the catalyst, by optimizing the slurry concentration, a catalyst precursor slurry with a certain mesh size is preferably screened out. At the same time, during the spray drying process, the angle between the hot air outlet and the atomizer spray outlet is controlled to be within a certain range, so that the hot air and the spray liquid flow in parallel, and the turbulence formed is used to shorten the drying time. At the same time, the catalyst thickness caused by wall adhesion loss on the dryer after spraying can be controlled within a relatively low range. The catalyst prepared in this way has uniform particle size distribution, high preparation time efficiency, and low wall adhesion loss. It has a good fluidized state for ammoxidation, such as propylene ammoxidation to produce acrylonitrile, a high acrylonitrile yield, and a low carbon content of by-products.

[0010] According to a first aspect of the present invention, the present invention provides an ammonia oxidation catalyst, 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 the Group VIII metal elements; 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; 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 0.05-10.0, the value range of b is 0.05-12.0, the value range of c is 0.02-8.0, the value range of d is 0.02-2.0, 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 hollow ratio of the catalyst is 0-5%.

[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) mixing an active component source and a carrier source in a solution state, boiling and hydrolyzing the slurry to obtain a slurry;

[0013] (2) spray drying the slurry to obtain a powder, and then calcining;

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

[0015] According to a third aspect of the present invention, there is provided use of the catalyst of the present invention in olefin ammoxidation reaction.

[0016] According to a fourth aspect of the present invention, there is provided a method for synthesizing acrylonitrile by ammoxidation of propylene, the method comprising contacting propylene with an ammonia source in the presence of the catalyst of the present invention in 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 a fluidized bed reactor, good fluidization state, high yield of ammoxidation target products such as acrylonitrile, low carbon content of by-products, and better long-term operation stability.

[0019] (2) In a preferred embodiment, the slurry is sieved before spray drying to remove larger precipitated particles. During the spray drying process, the angle between the hot air outlet and the atomizer spray 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 can be used to shorten the drying time and improve the catalyst preparation efficiency.

[0020] (3) The thickness of the adhesive wall on the spray dryer is controlled to be thinner to reduce the loss of catalyst separation.

[0021] In a preferred embodiment, the catalyst of the present invention is prepared by three steps of slurry preparation, spray drying and calcination. Before spraying, the slurry with a solid content of 35-60% is passed through a 40-120 mesh sieve to remove larger precipitated particles. During the spray drying process, the angle between the hot air outlet and the atomizer spray outlet is controlled to be 70° to 110°, and the hot air and the spray liquid flow in parallel. The turbulence formed is used to shorten the drying time. The thickness of the sticky wall on the dryer after spraying is controlled to be 0-3 mm. The obtained catalyst has uniform particle size distribution and good sphericity. The invention has good quality, a scanning electron microscope shows that the hollow rate is 0-5%, and the particle size distribution range (laser particle size volume fraction) is: the content of particles with a diameter less than 20 μm is 0-1.5% by volume, the content of particles with a diameter from 20 μm to less than 45 μm is 25-60% by volume, the content of particles with a diameter from 45 μm to less than 90 μm is 35-60% by volume, and the content of particles with a diameter greater than 90 μm is 0-10.0% by volume. The preparation time period is efficient and the wall adhesion loss is small. The invention has a good fluidized state for the reaction of propylene ammoxidation to prepare acrylonitrile, a high acrylonitrile yield, and a low carbon content of by-products. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a nitrogen adsorption / desorption curve of the catalyst of Example 1 of the present invention;

[0023] Figure 2 is the pore size distribution curve of the catalyst of Example 1 of the present invention;

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

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

[0026] Figure 5 It is a schematic diagram of the angle between the spray drying hot air outlet and the atomizer spray outlet of the present invention. DETAILED DESCRIPTION

[0027] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

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

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

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

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

[0032] The value range of a is 0.05-10.0,

[0033] The value range of b is 0.05-12.0,

[0034] The value range of c is 0.02-8.0,

[0035] The value range of d is 0.02-2.0,

[0036] a, b, c and d represent the molar contents 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 hollow ratio of the catalyst is 0-5%.

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

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

[0041] In the present invention, there is no special requirement for the type of the carrier. According to one embodiment of the present invention, the carrier includes at least one of silicon oxide and aluminum oxide, preferably silicon dioxide; but the present 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: the content of particle size less than 20μm is 0-1.5% by volume, preferably 0.05-1.4% by volume; the content of particle size from 20μm to less than 45μm is 25-60% by volume, preferably 35-55% by volume; the content of particle size from 45μm to less than 90μm is 35-60% by volume, preferably 45-50% by volume; the content of particle size above 90μm is 0-10.0% by volume, preferably 0.5-6% by volume.

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

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

[0045] In the present invention, the catalyst has good attrition performance. After a 20-hour attrition test, the attrition 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 L acid site of the catalyst is located at 1445 cm -1 ~1455cm -1 , the B acid site is located at 1535cm -1 ~1545cm -1 between.

[0047] The present invention has no special requirements for the preparation method of the catalyst. As long as the above characteristics are met, the purpose of the present invention can be achieved. According to a preferred embodiment of the present invention, a preparation method of an ammonia oxidation catalyst is provided, which comprises:

[0048] (1) mixing an active component source and a carrier source in a solution state, boiling and hydrolyzing the slurry to obtain a slurry;

[0049] (2) spray drying the slurry to obtain a powder, and then calcining;

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

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

[0052] a) heating and dissolving the Mo-containing source and fully mixing it with the carrier source;

[0053] b) heating and dissolving the Bi source, B source, C source, and D source, and adding them into the mixed solution of step a), and stirring them evenly to obtain a mixed slurry. The Mo source and the carrier source are alkaline, and the Bi source is acidic. Dissolving them separately can avoid precipitation due to acid-base reaction during the dissolution of the raw materials, resulting in uneven components in the slurry.

[0054] In the present invention, the active source is a water-soluble salt containing an active metal element, for example, the Mo source is an oxygen-containing acid ammonium salt containing Mo, preferably (NH4)6Mo7O 24 Or its hydrate. The remaining Bi source, B source, C source, D source are preferably one or more of halides, alkoxides, nitrates or acetates, preferably nitrates, such as bismuth nitrate, iron nitrate, nickel nitrate, magnesium nitrate, etc. This is only an illustrative description, but the present invention cannot be limited to this scope.

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

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

[0057] In the present invention, controlling the wall thickness of the slurry after spraying can reduce the loss of raw materials and lower production costs. Appropriate drying time and temperature can achieve fast and efficient drying. Controlling the particle size of the spray droplets can make the particle size of the final product within the reasonable range required by the present invention, and can be particularly suitable for fluidized bed reactors.

[0058] In the present invention, there is no special requirement for the carrier source, and it can be selected specifically according to the carrier. The carrier source is silica sol or a mixed carrier 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 contacting conditions in the solution state in step (1) include: the mixed contacting conditions include: the temperature is 30 to 80°C.

[0060] According to a preferred embodiment of the present invention, the contacting in step (1) is carried out in the presence of an additive; the additive is selected from one or more of sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, cetyltrimethylammonium 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, and more preferably a mixture of CTAB and P123, and 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 the solution in step (1) a) is 2.0-10.0 g / L.

[0062] According to a preferred embodiment of the present invention, the conditions for hydrolysis and pulping 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 to 60 wt%, preferably 40 to 55 wt%.

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

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

[0066] The present invention provides application of the catalyst of the present invention in olefin ammoxidation reaction, wherein the olefin is selected from one or more of propylene and isobutylene.

[0067] The present invention provides a method for synthesizing acrylonitrile by ammoxidation of propylene, which comprises contacting propylene with an ammonia source in the presence of the catalyst of the present invention and in an oxygen-containing atmosphere.

[0068] The present invention has no special requirements for ammonia oxidation conditions, and commonly used ammonia oxidation conditions can be used in the present invention. For the present invention, according to one embodiment of the present 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 mixed gas of oxygen and an inert gas.

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

[0071] According to one embodiment of the present invention, the contact conditions include: the molar ratio of propylene, the ammonia source calculated as ammonia gas, and the oxygen-containing atmosphere calculated as oxygen contained is 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 load is 0.08-0.12 h -1 The calcination conditions of the present invention are only for illustrative purposes, but the present invention is not limited to this scope.

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

[0074] a) heating and dissolving the active component precursor containing Mo, and fully mixing with the carrier source;

[0075] b) heating and dissolving an active component precursor containing metals such as Bi, B, C, and D, and adding the precursor to the mixed solution of step a), and stirring the mixture to obtain a mixed slurry;

[0076] c) heating and boiling the slurry obtained in step b), and sieving to remove larger precipitated particles;

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

[0078] Furthermore, in steps a) and b), the active source is a water-soluble salt containing an active metal element, for example, the Mo source is an oxygen-containing acid ammonium salt containing Mo, preferably (NH4)6Mo7O 24 The remaining Bi source, B source, C source, and D source are preferably one or more of halides, alkoxides, nitrates, or acetates, preferably nitrates, such as bismuth nitrate, iron nitrate, nickel nitrate, and magnesium nitrate.

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

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

[0081] Furthermore, in step c), the conditions for heating and boiling the slurry are as follows: time 10 to 30 minutes, temperature 110 to 160° C., preferably 125 to 150° C., and stirring speed 150 to 250 rpm.

[0082] Furthermore, in step c), the mesh number of the sample screening step is 40 to 120 meshes, preferably 80 to 100 meshes.

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

[0084] Furthermore, in step d), the heat source for spray drying is air, the drying temperature is 300-420°C, preferably 320-400°C, 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] Furthermore, in step d), the catalyst has a wall thickness of 0 to 3 mm, preferably 0 to 2 mm, after spray drying on the dryer.

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

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

[0088] The specific reaction conditions include: the molar ratio of propylene / ammonia / air (based on the oxygen contained) is 1:1.1-1.3:9.5-10.0, the reaction temperature is 420-440°C, the reaction pressure (gauge pressure) is 0.06-0.12 MPa, and the reaction catalyst load is 0.08-0.12 h -1 .

[0089] The catalyst of the present invention has good sphericity, and the scanning electron microscope shows that the hollow rate is 0-0.5%, and the particle size distribution range (laser particle size volume fraction) is: the content of particles less than 20μm is 0-1.5% by volume, the content of particles from 20μm to less than 45μm is 25-60% by volume, the content of particles from 45μm to less than 90μm is 35-60% by volume, and the content of particles above 90μm is 0-10.0% by volume.

[0090] The particle size distribution of the catalyst in the present invention is measured by using a Mastersizer 2000 particle size analyzer.

[0091] The hollow ratio of the catalyst particles in the present invention, that is, the ratio of catalyst particles with central hollow cavities to all particles, is obtained by observation and calculation through a scanning electron microscope (SEM).

[0092] The method for measuring the specific surface area and pore size in the present invention adopts a Tristar physical adsorption instrument for measurement. Before the sample is tested, it is necessary to perform a heating vacuum degassing treatment. The porosity of the sample is measured at 77K, and the specific surface area is calculated by the Brunauer-Emmett-Teller (BET) method. The distribution of pore size and pore volume can be calculated from the isothermal adsorption branch using the Barrettner-Joyner-Halenda (BJH) model.

[0093] The Fourier transform pyridine adsorption infrared (FT-IR) spectrum used in the present invention is a Nicolet Fourier spectrophotometer made in the United States.

[0094] The catalyst wear index measuring device of the present invention adopts the wear index measuring device produced by Beijing Huiersanji Green Chemical Technology Co., Ltd., and the wear index measuring method is as follows:

[0095] (1) About 10 grams of catalyst with 200-300 mesh size is screened for determination of attrition index;

[0096] (2) At room temperature and standard atmospheric pressure, the reaction tube containing the catalyst is ventilated and purged at an air flow rate of 10 L / min;

[0097] (3) The catalyst collection bag was weighed when the cumulative purge time was 1 h and 20 h respectively, and the catalyst attrition index was calculated.

[0098] Excluding the fine powder caused by catalyst loss within the first hour, the calculation method of the attrition index is:

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

[0100] In the present invention, gas chromatography is used to perform online analysis on the product gas, and the conversion rate of propylene, the selectivity of acrylonitrile and the single-pass yield are used as indicators for evaluating the performance of the catalyst, and the definitions of the two are as follows:

[0101] Acrylonitrile conversion (%) = (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 (%) = (acrylonitrile produced moles / propylene feed moles) × 100%

[0104] In the present invention, the catalyst composition is calculated based on the raw material input.

[0105] Example 1

[0106] 84.6 g (NH4)6Mo7O 24·4H2O is dissolved in hot water, 250 grams of silica sol with a mass fraction of 40% is added, and the solution I is obtained by mixing thoroughly; 15.5 grams of Bi(NO3)3·5H2O, 55.7 grams of Ni(NO3)2·6H2O, 32.2 grams of Fe(NO3)3·9H2O, 16.4 grams of Mg(NO3)2·6H2O and 0.45 grams of KOH are dissolved and mixed thoroughly at 70°C to obtain solution II, which is added to solution I, heated at 135°C for 20 minutes, and stirred at a speed of 220 rpm to obtain a mixed slurry III (solid content is 52wt% by weight). The slurry is sieved through 100 mesh to remove large particles of precipitate. The solid content after sieving is 49wt%. The angle between the hot air outlet and the atomizer spray outlet is controlled to be 90° for spray drying (such as Figure 5 As shown), the average diameter of the spray droplets is 50μm, the heat source is air, the drying temperature is 350℃, the drying time is 0.5 hours, and the powder is obtained. The thickness of the powder wall is 0-1.5mm. The particles are calcined at 600℃ in air atmosphere 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 of less than 20 μm, a content of 0.6%, a content of 20 μm to 45 μm, a content of 47.6%, a content of 45 μm to 90 μm, and a content of 3.1% of particles larger than 90 μm. The specific surface area is 40.2 m 2 / g, the most probable pore size is 10.8nm ( Figure 1 , Figure 2 ); the wear index is 0.82%; Figure 4 The infrared spectrum of pyridine is the catalyst. The characteristic absorption peaks of pyridine adsorbing infrared L acid and B acid are located at 1450 cm -1 1539cm -1 Place. Figure 3 This is a SEM picture of the catalyst of the present invention. From the picture, it can be observed and calculated that the hollow ratio of the catalyst is 0.35%.

[0109] The reaction conditions for producing acrylonitrile by propylene ammoxidation of the above catalyst are:

[0110] On a millimeter fluidized bed reactor, reaction temperature: 420°C; reaction pressure: 0.085Mpa; catalyst loading: 300g; catalyst propylene load (WWH): 0.12h -1; Raw material ratio (molar): C3 ＝ / NH3 / air=1 / 1.25 / 9.6. Propylene conversion was 99.25%, acrylonitrile selectivity was 83.70%, and acrylonitrile single-pass yield was 83.07%.

[0111] Example 2

[0112] 92.4 g (NH4)6Mo7O 24 ·4H2O was dissolved in hot water, 230 g of silica sol with a mass fraction of 40% was added, and the mixture was 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 mixed thoroughly at 70°C to obtain solution II, which was added to solution I, stirred at 220 rpm at 140°C, and heated for 20 min to obtain mixed slurry III (solid content of 53 wt%). The slurry was sieved through 100 mesh to remove large particle precipitates, and the solid content after sieving was 48 wt%. The angle between the hot air outlet and the atomizer spray outlet was controlled to be 90° for spray drying, the average diameter of the spray droplets was 60 μm, the heat source was air, the drying temperature was 350°C, the drying time was 0.5 hours, and a powder was obtained, and the thickness of the powder wall was 0 to 1.8 mm. The particles were calcined at 600°C in an air atmosphere for 4 hours to obtain acrylonitrile catalyst B, whose general composition 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 of less than 20 μm, a content of 0.5%, a content of 20 μm to 45 μm, a content of 48.2%, a content of 45 μm to 90 μm, and a content of 3.5% of particles larger than 90 μm. The specific surface area is 38.7 m 2 / g, the most probable pore size is 11nm; the abrasion index is 0.85%; the characteristic absorption peaks of pyridine adsorption infrared L acid and B acid are located at 1449cm -1 1540cm -1 At , the hollow ratio of the catalyst is 0.45%.

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

[0116] Example 3

[0117] 84.6 g (NH4)6Mo7O 24 ·4H2O was dissolved in hot water, 250 g of silica sol with a mass fraction of 40% was added, and the mixture was 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 heated at 70°C to dissolve and mix thoroughly to obtain solution II, which was added to solution I, heated at 150°C for 20 min, and stirred at a speed of 180 rpm to obtain mixed slurry III (solid content of 50 wt% by weight). The slurry was sieved through 80 mesh to remove large particle precipitates, and the solid content after sieving was 47 wt%. The angle between the hot air outlet and the atomizer spray outlet was controlled to be 85° for spray drying, the average diameter of the spray droplets was 80 μm, the heat source was air, the drying temperature was 350°C, the drying time was 0.5 hours, and a powder was obtained, and the thickness of the powder wall was 0 to 1.6 mm. The particles were calcined at 580°C in an air atmosphere for 4 hours to obtain acrylonitrile catalyst C, whose general composition 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 of less than 20 μm, a content of 0.8%, a content of 20 μm to 45 μm, a content of 49.0%, a content of 45 μm to 90 μm, and a content of 2.0% of particles larger than 90 μm. The specific surface area is 38.5 m 2 / g, the most probable pore size is 11.2nm; the abrasion index is 0.78%; the characteristic absorption peaks of pyridine adsorption infrared L acid and B acid are located at 1447cm -1 1543cm -1 At , the hollow ratio of the catalyst is 0.42%.

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

[0121] Example 4

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

[0123] The catalyst has a particle size of less than 20 μm, a content of 0.1%, a content of 20 μm to 45 μm, a content of 38.7%, a content of 45 μm to 90 μm, and a content of 11.0% of particles larger than 90 μm. The specific surface area is 27.5 m 2 / g, the most probable pore size is 18.0nm; the abrasion index is 2.45%; the characteristic absorption peaks of pyridine adsorption infrared L acid and B acid are located at 1448cm -1 1542cm -1 At , the hollow ratio of the catalyst is 2.53%.

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

[0125] Example 5

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

[0127] The catalyst has a particle size of less than 20 μm, a content of 0.2%, a content of 20 μm to 45 μm, a content of 49.5% of 45 μm to 90 μm, and a content of 7.5% of particles larger than 90 μm. The specific surface area is 30.2 m 2 / g, the most probable pore size is 16.3nm; the abrasion index is 1.85%; the characteristic absorption peaks of pyridine adsorption infrared L acid and B acid are located at 1450cm -1 1542cm -1 At , the hollow ratio of the catalyst is 3.20%.

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

[0129] Example 6

[0130] The method of Example 1 is followed, except that after adding the carrier to obtain solution I, a surfactant cetyltrimethylammonium bromide (CTAB, the mass concentration of the surfactant in solution I is 3.6 g / L) is added for stirring and mixing, and the other conditions remain unchanged. The powder wall adhesion thickness after spray drying is 0 to 1.2 mm.

[0131] The catalyst has a particle size of less than 20 μm, a content of 1.1%, a content of 20 μm to 45 μm, a content of 50.6%, a content of 45 μm to 90 μm, and a content of 0.9% of particles larger than 90 μm. The specific surface area is 42.5 m 2 / g, the most probable pore size is 9.3nm; the abrasion index is 0.62%; the characteristic absorption peaks of pyridine adsorption infrared L acid and B acid are located at 1448cm -1 1541cm -1 At , the hollow ratio of the catalyst is 0.20%.

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

[0133] Example 7

[0134] The method of Example 1 is followed, except that after adding the carrier to obtain solution I, surfactants CTAB and P123 (the mass ratio of CTAB to P123 is 2:1, and the mass concentration of the surfactant in solution I is 3.6 g / L) are added for stirring and mixing, and the other conditions remain unchanged. The powder wall adhesion thickness after spray drying is 0 to 1.0 mm.

[0135] The catalyst has a particle size of less than 20 μm, a content of 1.4%, a content of 20 μm to 45 μm, a content of 47.0% of 45 μm to 90 μm, and a content of 0.4% of particles larger than 90 μm. The specific surface area is 44.2 m 2 / g, the most probable pore size is 8.5nm; the abrasion index is 0.40%; the characteristic absorption peaks of pyridine adsorption infrared L acid and B acid are located at 1447cm -1 1540cm -1 At , the hollow ratio of the catalyst is 0.15%.

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

[0137] Example 8

[0138] The method of Example 1 is followed, except that the slurry cooking condition is heating at 120° C. for 30 min to obtain mixed slurry III, wherein the powder wall adhesion thickness after spray drying is 0 to 1.6 mm.

[0139] The catalyst has a particle size of less than 20 μm, a content of 0.5%, a content of 20 μm to 45 μm, a content of 43.2%, a content of 45 μm to 90 μm, and a content of 7.3% of particles larger than 90 μm. The specific surface area is 35.4 m 2 / g, the most probable pore size is 12.2nm; the abrasion index is 0.94%; the characteristic absorption peaks of pyridine adsorption infrared L acid and B acid are located at 1449cm -1 1539cm -1 At , the hollow ratio of the catalyst is 0.59%.

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

[0141] Comparative Example 1

[0142] The catalyst was prepared according to the method of Example 1, except that the angle between the hot air outlet and the atomizer spray outlet was controlled to be 60° during spray drying, and the other conditions remained unchanged. The powder wall adhesion thickness after spray drying was more than 5.5 mm. The catalyst had a particle size content of less than 20 μm, a particle size content of 20 μm to 45 μm, a particle size content of 45 μm to 90 μm, a particle size content of 52.1%, and a particle size content of greater than 90 μm, and a specific surface area of ​​25.2 m 2 / g, the most probable pore size is 19.1nm; the abrasion index is 5.60%; the characteristic absorption peaks of pyridine adsorption infrared L acid and B acid are located at 1448cm -1 1541cm -1 At , the hollow ratio of the catalyst is 6.5%.

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

[0144] Comparative Example 2

[0145] 97.3 g (NH4)6Mo7O 24·4H2O was heated and dissolved in water, and 350 grams of silica sol with a mass fraction of 30% was added to obtain material I; 9.6 grams of Bi(NO3)3·5H2O, 49.7 grams of Ni(NO3)2·6H2O, 30.2 grams of Fe(NO3)3·9H2O, and 16.2 grams of Mg(NO3)2·6H2O were dissolved in water and incorporated into material I to obtain mixed slurry II; 14.0 grams of urea was weighed, dissolved in water, and added to mixed slurry II, and stirred at 300 rpm for 0.5 hours at 100°C to obtain slurry. The angle between the hot air outlet and the atomizer spray outlet was controlled to be 50° to spray dry the slurry, the drying temperature was 350°C, and the drying time was 0.5 hours to obtain particles, which were calcined at 600°C in air atmosphere for 3 hours to obtain acrylonitrile catalyst, whose general component formula is:

[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 has a particle size of less than 20 μm, a content of 0.1%, a content of 20 μm to 45 μm, a content of 36.2%, a content of 45 μm to 90 μm, and a content of 8.4% of particles larger than 90 μm. The specific surface area is 22.0 m 2 / g, the most probable pore size is 20.7nm; the abrasion index is 6.2%; the characteristic absorption peaks of pyridine adsorption infrared L acid and B acid are located at 1450cm -1 1542cm -1 The hollow ratio of the catalyst is 5.57%. The thickness of the powder sticking to the wall after spray drying is more than 6.2 mm.

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

[0149] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various specific technical features in any suitable manner. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations. However, these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. An ammonia oxidation catalyst, characterized in that The general formula of the active component of the catalyst is Mo 12 Bi a B b C c D d O x ;in, B is selected from at least one of the 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; The value range of a is 0.05-10.0, The value range of b is 0.05-12.0, The value range of c is 0.02-8.0, The value range of d is 0.02-2.0, a, b, c and d represent the molar contents 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 ratio of the catalyst is 0-5%.

2. The catalyst according to claim 1, wherein The hollow ratio of the catalyst is 0 to 1.0%, preferably 0 to 0.5%; The catalyst comprises a carrier, preferably the catalyst comprises 45 to 60% by weight of the carrier and 40 to 55% by weight of the active component; More preferably, the support comprises at least one of silicon oxide and aluminum oxide, preferably silicon dioxide; and / or The catalyst particle size distribution includes: The content of particles smaller than 20 μm is 0 to 1.5% by volume, preferably 0.05 to 1.4% by volume; The content of particles with a diameter of 20 μm to less than 45 μm is 25 to 60% by volume, preferably 35 to 55% by volume; The content of particles with a diameter of 45 μm to less than 90 μm is 35 to 60% by volume, preferably 45 to 50% by volume; The content of particles with a diameter of 90 μm or more is 0 to 10.0% by volume, preferably 0.5 to 6% by volume; and / or The specific surface area of ​​the catalyst is 25 to 50 m 2 / g, preferably 35-45m 2 / g, the most probable pore size is 5 to 20 nm, preferably 8 to 12 nm; The catalytic attrition index is 0.2% to 1.5%, preferably 0.6% to 1.0%; The L acid site of the catalyst is located at 1445 cm -1 ~1455cm -1 The B acid site is located at 1535 cm -1 ~1545cm -1 between.

3. A method for preparing the ammonia oxidation catalyst according to claim 1 or 2, characterized in that: The method includes: (1) mixing an active component source and a carrier source in a solution state, boiling and hydrolyzing the slurry to obtain a slurry; (2) spray drying the slurry to obtain a powder, and then calcining; The conditions for spray drying include: the angle between the hot air outlet and the atomizer spray outlet is 70° to 110°, preferably 80° to 100°; Preferably, step (1) comprises: a) heating and dissolving the Mo-containing source and fully mixing it with the carrier; b) heating and dissolving the Bi source, B source, C source and D source, adding the mixture into the mixed solution of step a), and stirring evenly to obtain a mixed slurry.

4. The preparation method according to claim 3, wherein The thickness of the slurry on the dryer after spray drying is controlled to be 0 to 3 mm, preferably 0 to 2 mm; Preferably, the spray drying conditions include: The heat source is air, and / or The drying temperature is 300-420°C, preferably 320-400°C; and / or Drying time 0.5-3.0h, preferably 0.5-1.0h; and / or The average diameter of the spray droplets is 30-150 μm, preferably 30-120 μm.

5. The preparation method according to claim 3 or 4, wherein The conditions for contacting in the solution state in step (1) include: The carrier source is selected from silica sol with a mass concentration of 30% to 40%; and / or The mixed contact conditions include: temperature 30 to 80°C; and / or The contacting in step (1) is carried out in the presence of an additive; the additive is selected from one or more of sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, hexadecyltrimethylammonium bromide, polyethylene glycol, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, and polyether F127; Preferably selected from one or more of sodium lauryl sulfate, CTAB, polyethylene glycol, and P123; More preferably, it is a mixture of CTAB and P123, the weight ratio of the two is 5.0-1.0:1; Preferably, the mass concentration of the additive in step a) is 2.0-10.0 g / L solution; The conditions for hydrolysis and pulping include: time of 10 to 30 minutes; and / or temperature of 110 to 160° C., preferably 125 to 150° C.; and / or stirring speed of 150 to 250 rpm.

6. The preparation method according to any one of claims 3 to 5, wherein: The solid content of the slurry in step (1) is 30-60wt%, preferably 40-55wt%; Before step (2), the slurry is sieved with a 40-120 mesh, preferably 80-100 mesh, sieve to remove precipitated particles, and the solid content after sieving is preferably 42-50 wt%.

7. The preparation method according to any one of claims 3 to 6, wherein: The calcination conditions include: being carried out in an oxygen-containing atmosphere, and / or a calcination temperature of 400 to 700° C., preferably 450 to 640° C.; and / or a calcination time of 3 to 8 hours, preferably 4 to 6 hours.

8. Use of the catalyst according to claim 1 or 2 in olefin ammoxidation reaction, wherein the olefin is selected from one or more of propylene and isobutylene.

9. A method for synthesizing acrylonitrile by ammoxidation of propylene, characterized in that: The method comprises contacting propylene with an ammonia source in the presence of the catalyst according to claim 1 or 2 in an oxygen-containing atmosphere.

10. The method according to claim 9, wherein: The contact conditions 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 contacting is carried out in a fluidized bed reactor; and / or The contact conditions include: the molar ratio of propylene, ammonia source (calculated as ammonia gas), and oxygen-containing atmosphere (calculated as contained oxygen) is 1: 1.1～1.3：9.5～10.0； The temperature is 420-440°C, the pressure (gauge pressure) is 0.06-0.12 MPa, and the catalyst load is 0.08-0.12 h -1 .

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