An ammonia oxidation catalyst, its preparation method and application

Abstract

The present invention discloses an ammonia oxidation catalyst, a preparation method thereof and an application thereof. The active components of the catalyst include molybdenum and bismuth, and the carrier includes silica. The change in the average pore diameter of the catalyst after heat treatment conforms to Y = (P2 - P1) / P1, where the value of Y is less than or equal to 4.5, and P1 and P2 are the average pore diameters of the catalyst under different heat treatment conditions respectively. This catalyst exhibits better long-term stability in the application of ammoxidation of propylene to acrylonitrile.

Description

Technical Field

[0001] The present invention relates to an ammonia oxidation catalyst, and particularly to a catalyst for ammoxidation of propylene to acrylonitrile, a preparation method thereof, and an application thereof in the reaction of ammoxidation of propylene to acrylonitrile. Background Art

[0002] Acrylonitrile is an important chemical raw material for fibers, rubbers, plastics, etc., and is mainly used to produce acrylic fibers, ABS plastics, styrene plastics, acrylamide, etc. Industrially, acrylonitrile is mainly produced from propylene by using the fluidized bed ammoxidation method.

[0003] The technology of ammoxidation of propylene to acrylonitrile has been successfully industrialized in acrylonitrile plants all over the world. However, as one of the core technologies of this process, the catalyst for ammoxidation of propylene to acrylonitrile has been continuously studied and developed in order to prepare a catalyst with more excellent comprehensive properties such as activity and selectivity.

[0004] At present, as a relatively mature ammonia oxidation catalyst, the molybdenum-bismuth-iron series catalyst has been widely used in industry. The Mo-Bi series catalyst can be prepared by the spray drying method. The process is as follows: a metal precursor and a carrier material are made into a slurry, then spray dried, and then calcined to obtain the catalyst. For example, the spray drying method for preparing an ammonia oxidation catalyst disclosed in CN1600423A.

[0005] However, in the existing production process of acrylonitrile, there is still a problem that it is difficult to balance the activity and / or selectivity of the catalyst for ammoxidation of propylene to acrylonitrile and its long-term use stability. Therefore, developing a Mo-Bi series catalyst with both good activity and / or selectivity and long-term use stability has been the goal that the field has been working hard to study. Summary of the Invention

[0006] The inventors of the present invention have found through a large number of studies that when the ammoxidation catalyst uses an active component including Mo-Bi and a carrier including silica, when the average pore diameter of the catalyst meets specific requirements with the increase of a specific heat treatment temperature, the catalyst can effectively exhibit stable catalytic activity during long-term stable operation, especially a stable single-pass yield of acrylonitrile. The inventors have further found that when preparing the above catalyst, a precursor with alkalinity and a precursor with acidity are co-precipitated in parallel, and in this way, the above catalyst can be prepared. The possible reason is that by controlling the co-precipitation in parallel, grains with uniform size can be obtained, so as to achieve the purpose of controlling the average pore diameter of the catalyst, and the present invention has been completed on this basis.

[0007] The present invention provides an ammonia oxidation catalyst, a preparation method thereof, and an application thereof. The catalyst has the characteristic of good long-term stability when used for ammoxidation of propylene to acrylonitrile.

[0008] In the first aspect of the present invention, an ammonia oxidation catalyst is provided. The active components of the catalyst include molybdenum and bismuth, and the carrier includes silica. The change in the average pore diameter of the catalyst after heat treatment conforms to formula (I):

[0009] Y = (P2 - P1) / P1 (I),

[0010] wherein the value of Y is less than or equal to 4.5, P2 is the average pore diameter of the catalyst after heat treatment at temperature T2 and in a water-containing atmosphere, P1 is the average pore diameter of the catalyst after heat treatment at temperature T1 and in a water-containing atmosphere, and T2 > T1, T2 ≤ 750 °C.

[0011] In the catalyst of the present invention, the value of Y is less than or equal to 4.5, preferably 0.5 - 4.5. Among them, the value of Y can be, but is not limited to: 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, etc., and further preferably 1.5 - 4.0.

[0012] In the catalyst of the present invention, the temperature T1 is 400 - 600 °C, preferably 450 - 600 °C, and the temperature T2 is 500 - 750 °C, preferably 550 - 700 °C. Further, the temperature T2 is at least 50 °C higher than the temperature T1.

[0013] In the catalyst of the present invention, the heat treatment time is 0.5 - 4 h, preferably 0.5 - 2 h.

[0014] In the catalyst of the present invention, the heat treatment is carried out in an atmosphere of a continuously flowing mixed gas containing water and oxygen. In the mixed gas, the volume content of water is 0.01% - 4.5%, the volume content of oxygen is 10% - 30%, and the ratio of the amount of the mixed gas introduced per unit time to the mass of the catalyst is 50 - 500 L / kg·h. The mixed gas containing water and oxygen also contains at least one of nitrogen or an inert gas.

[0015] In the catalyst of the present invention, the active components include molybdenum and bismuth. Based on the weight of the catalyst, the weight content of molybdenum calculated as MoO3 is 15% - 55%, preferably 20% - 45%, and the weight content of bismuth calculated as Bi2O3 is 0.5% - 3.5%, preferably 1.0% - 3.5%.

[0016] In the catalyst of the present invention, preferably, the atomic ratio of Bi / Mo is 0.008 - 0.25, preferably 0.01 - 0.20. Among them, the atomic ratio of Bi / Mo can be exemplified but not limited to: 0.01, 0.05, 0.10, 0.15, 0.20, 0.25, etc.

[0017] In the catalyst of the present invention, the active components may further include Fe, rare earth elements, alkali metal elements, alkaline earth metal elements, and metal element A. The rare earth elements are selected from at least one of La, Ce, Pr, Nd, and Sm. The alkali metal elements are selected from at least one of Li, Na, K, Rb, and Cs. The alkaline earth metal elements are selected from at least one of Be, Mg, Ca, Sr, and Ba. The metal element A is selected from at least one of W, V, Zr, P, Nb, Ni, Co, Cr, Mn, Tl, Au, Ag, Pt, Ru, Rh, Pd, Ti, Sb, In, Sn, and Te. Further preferably, the metal element A is selected from at least one of Co, Mn, P, Pd, and Nb.

[0018] In the catalyst of the present invention, based on the weight of the catalyst, the weight content of molybdenum calculated as MoO3 is 15% - 55%, preferably 20% - 45%; the weight content of bismuth calculated as Bi2O3 is 0.5% - 3.5%, preferably 1.0% - 3.5%; the weight content of Fe element calculated as Fe2O3 is 1% - 12%, preferably 1.5% - 11%; the weight content of rare earth elements calculated as the oxides of rare earth elements is 1.5% - 8.5%, preferably 2.5% - 5.0%; the weight content of alkali metal elements calculated as oxides is 0.01% - 0.60%, preferably 0.05% - 0.55%; the weight content of alkaline earth metals calculated as oxides is 0.01% - 4.0%, preferably 0.5% - 3.5%; the weight content of metal element A calculated as oxides is 0.01% - 15%, preferably 0.05% - 14%.

[0019] In the catalyst of the present invention, preferably, in the active components, the atomic ratio of Bi / Mo is 0.008 - 0.25, preferably 0.01 - 0.20. Among them, the atomic ratio of Bi / Mo can be exemplified but not limited to: 0.01, 0.05, 0.10, 0.15, 0.20, 0.25, etc.; the atomic ratio of Fe / Bi is 1.0 - 7.0, preferably 2.0 - 6.0. Among them, the atomic ratio of Fe / Bi can be exemplified but not limited to: 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, etc.; the atomic ratio of (rare earth elements + alkali metal elements + alkaline earth metal elements) / Mo is 0.05 - 0.40, preferably 0.10 - 0.35. Among them, the atomic ratio of (rare earth elements + alkali metal elements + alkaline earth metal elements) / Mo can be exemplified but not limited to: 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, etc.; the atomic ratio of A / Mo is 0.01 - 1.0, preferably 0.02 - 0.9.

[0020] In the catalyst of the present invention, other components may also be contained in the carrier, and the other components may be at least one of zirconia, molecular sieve, cerium oxide, titanium oxide, and calcium oxide. Based on the weight of the carrier, the content of SiO2 is 20% to 100%, preferably 30% to 100%, and the content of other components is less than 20%, preferably 0% to 15%.

[0021] In the catalyst of the present invention, based on the weight of the catalyst, the content of the active component in terms of oxide is 20% to 80%, and the content of the carrier is 20% to 80%.

[0022] In the catalyst of the present invention, the pore size distribution of the catalyst is as follows: the pore volume of pores with a pore size less than 5 nm and greater than 80 nm accounts for 10% or less of the total pore volume, preferably 8% or less, and more preferably 7% or less.

[0023] According to the present invention, the catalyst is in granular form, and its average particle size is 30 to 70 μm, preferably 40 to 60 μm.

[0024] The second aspect of the present invention provides a method for preparing the above catalyst, comprising the following steps:

[0025] (1) A basic material containing molybdenum and a carrier precursor and an acidic material containing a bismuth-containing active component precursor are subjected to a co-current precipitation reaction to obtain slurry I;

[0026] (2) The slurry I is spray-dried and heat-treated to obtain the catalyst.

[0027] In the method of the present invention, the carrier precursor in step (1) includes silica sol. In the silica sol, the solid content in terms of silicon dioxide is 20 wt% to 50 wt%, and the average particle size is 10 to 35 nm.

[0028] In the method of the present invention, in the basic material containing molybdenum and a carrier precursor in step (1), the mass concentration of the material is controlled to be 20% to 55%. Solvents that may be present in the basic material, such as alcohols and water, especially C1-C6 monohydric alcohols (such as ethanol) and water, preferably water. These solvents can be used alone or in combination in any proportion.

[0029] In the method of the present invention, in the acidic material containing a bismuth-containing active component precursor in step (1), the mass concentration of the material is controlled to be 20% to 60%. Solvents that may be present in the acidic material, such as alcohols and water, especially C1-C6 monohydric alcohols (such as ethanol) and water, preferably water. These solvents can be used alone or in combination in any proportion.

[0030] In the method of the present invention, the time of co-current precipitation in step (1) is 10 to 40 minutes, preferably 10 to 25 minutes. Further, after the addition of the materials, further stirring and mixing are carried out, and the mixing time is 10 to 30 minutes, preferably 10 to 25 minutes.

[0031] In the method of the present invention, the temperature of the co-current precipitation in step (1) is controlled at 20 to 60 °C.

[0032] In the acidic material of the active component precursor containing bismuth in step (1) of the method of the present invention, it further includes precursors of Fe, rare earth elements, alkali metal elements, alkaline earth metal elements, and metal element A. The rare earth elements are selected from at least one of La, Ce, Pr, Nd, and Sm. The alkali metal elements are selected from at least one of Li, Na, K, Rb, and Cs. The alkaline earth metal elements are selected from at least one of Be, Mg, Ca, Sr, and Ba. The metal element A is selected from at least one of W, V, Zr, P, Nb, Ni, Co, Cr, Mn, Tl, Au, Ag, Pt, Ru, Rh, Pd, Ti, Sb, In, Sn, and Te. Preferably, the metal element A is selected from at least one of Co, Mn, P, Pd, and Nb. Further, the atomic ratio of Bi / Mo is 0.008 to 0.25, preferably 0.01 to 0.20; the atomic ratio of Fe / Bi is 1.0 to 7.0, preferably 2.0 to 6.0; the atomic ratio of (rare earth element + alkali metal element + alkaline earth metal element) / Mo is 0.05 to 0.40, preferably 0.10 to 0.35; the atomic ratio of A / Mo is 0.01 to 1.0, preferably 0.02 to 0.9.

[0033] In the method of the present invention, in step (1), there is no particular limitation on the Mo element precursor, which can be an oxide of Mo or any substance that can generate this oxide after calcination. Specifically, for example, oxides, hydroxides, inorganic acid salts, organic acid salts, and ammonium oxo salts of Mo (including hydrates of these compounds) can be cited. Among them, water-soluble inorganic acid salts, water-soluble organic acid salts, and ammonium oxo salts of Mo are preferred, and ammonium oxo salts of Mo are more preferred, such as (NH4)6Mo7O 24Or its hydrate. There are no particular limitations on the Bi element precursor, the rare earth element precursor, the alkali metal element precursor, the alkaline earth metal element precursor, and the metal A element precursor, which can be oxides of the corresponding elements or any substances that can generate the oxides after calcination. Specifically, for example, oxides, hydroxides, inorganic acid salts, and organic acid salts (including hydrates of these compounds) of the corresponding elements can be cited. Water-soluble inorganic acid salts and water-soluble organic acid salts are preferred, and halides, alkoxides, nitrates, and acetates are more preferred, especially nitrates. These precursors can be used alone or in combination of multiple kinds in any proportion.

[0034] In the method of the present invention, the conditions of the spray drying in step (2) include: the drying heat source is air, the drying temperature is 250 - 350 °C, preferably 300 - 350 °C, the drying time is 0.1 - 2.0 h, preferably 0.2 - 1.0 h, and the average diameter of the spray liquid droplets is 20 - 200 μm, preferably 40 - 180 μm.

[0035] In the method of the present invention, the heat treatment in step (2) is a high-temperature calcination treatment in a water-containing atmosphere. Preferably, the conditions of the heat treatment are as follows: the temperature is 500 - 750 °C, and the time is 0.2 - 4 h. The heat treatment is carried out in an atmosphere of a continuously flowing mixed gas containing water and oxygen, wherein in the mixed gas, the volume content of water is 0.01% - 4.5%, the volume content of oxygen is 10% - 30%, and the ratio of the amount of the mixed gas introduced per unit time to the mass of the catalyst is 50 - 500 L / kg·h. The mixed gas containing water and oxygen also contains at least one of nitrogen or inert gas.

[0036] The third aspect of the present invention provides a method for the ammoxidation of propylene to acrylonitrile, including: the step of subjecting propylene to an ammoxidation reaction to produce acrylonitrile in the presence of the above catalyst or the catalyst prepared by the above preparation method.

[0037] In the method of the present invention, the reaction conditions for the ammoxidation of propylene to acrylonitrile include: the molar ratio of propylene / ammonia / air in terms of O2 is 1:1.1 - 1.35:1.8 - 2.5, the reaction temperature is 420 - 440 °C, the reaction pressure is 0.03 - 0.14 MPa in gauge pressure, and the weight hourly space velocity is 0.04 - 0.10 h -1 .

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. The catalyst of the present invention has good stability and can exhibit stable catalytic activity during long-term stable operation.

[0040] 2. When the catalyst of the present invention is used in the ammoxidation of propylene to acrylonitrile, with the extension of the reaction time, the reduction amplitude of the acrylonitrile yield is significantly reduced, and a high single-pass yield of acrylonitrile can still be maintained after long-term operation. Detailed Embodiments

[0041] The following will detail the specific embodiments of the present invention. It should be noted that the protection scope of the present invention is not limited by these specific embodiments, but is determined by the appended claims.

[0042] In the present invention, the average particle size is measured using a Malvern MS2000 laser particle size analyzer. Before sample testing, the circulating water of the device needs to be turned on. Before sample determination, the refractive index of the catalyst needs to be selected, and the refractive index of SiO2, which is 1.45, is used as the refractive index for measuring the sample. Before sample measurement, the background needs to be measured. After measurement, the sample is added to 10% of the light obscuration, and the average value is selected after three measurements.

[0043] In the present invention, the so-called "oxide" refers to the most stable oxide under normal temperature and pressure. For example, the oxide of Na refers to Na2O, the oxide of Ni refers to NiO, and the oxide of Fe refers to Fe2O3.

[0044] In the present invention, the pore size of the catalyst is measured by the N2 adsorption-desorption average pore diameter (diameter) of the sample using a Tristar2000 from Micromeritics Instrument Corporation of the United States. The sample is first degassed under vacuum at 250 °C for 2 h, and then the N2 adsorption-desorption curve of the sample is measured at the liquid nitrogen temperature (-196 °C). The average pore diameter is obtained according to the BJH method.

[0045] Unless otherwise specified, all percentages, parts, ratios, etc. mentioned in this specification are based on weight, unless it does not conform to the common understanding of those skilled in the art when based on weight.

[0046] When using a fresh catalyst for the ammoxidation of propylene to acrylonitrile reaction, the propylene conversion rate, acrylonitrile selectivity, and acrylonitrile single-pass yield are calculated as evaluation indicators of the catalyst performance. Among them, the definitions of the propylene conversion rate, acrylonitrile selectivity, and acrylonitrile single-pass yield are as follows:

[0047] Propylene conversion rate (%) = Moles of reacted propylene / Moles of propylene fed × 100%;

[0048] Acrylonitrile selectivity (%) = Moles of acrylonitrile formed / Moles of reacted propylene × 100%;

[0049] Acrylonitrile single-pass yield (%) = Moles of acrylonitrile formed / Moles of propylene fed × 100%.

[0050]

Example 1

[0051] Dissolve 836.6 g of (NH4)6Mo7O 24 ·4H2O in 684 g of water. At 50 °C, add 2750 g of silica sol with a weight concentration of 40% to form slurry I, and the mass concentration of slurry I is 46.8%. Dissolve 2.46 g of KOH, 175.9 g of Bi(NO3)3·5H2O, 532.7 g of Ni(NO3)2·6H2O, 78.1 g of Pr(NO3)3·6H2O, 808.2 g of Fe(NO3)3·9H2O, and 139.5 g of Mg(NO3)2·6H2O in 195 g of water to obtain solution I. The mass concentration of solution I is 49.5%. Add slurry I and solution I to a separating funnel and carry out concurrent precipitation in a concurrent flow manner. At a temperature of 40 °C, control the time to 20 min. After adding all the materials, stir and mix for 30 min to form slurry II. Form the prepared slurry into microspheres in a spray dryer. The drying temperature is 300 °C, the drying time is 0.5 h, and the average diameter of the spray droplets is 100 μm to obtain particulate matter. Prepare two samples after spraying, and then in an atmosphere of N2 mixed gas with a volume content of water of 0.5% and a volume content of oxygen of 25%, the gas flow rate per unit time of the mixed gas relative to the mass of the catalyst is 200 L / kg·h, and calcine at 550 °C (T1) and 700 °C (T2) for 1 h respectively to obtain the required catalyst samples.

[0052] The composition of the catalyst obtained according to the above steps is represented by the following formula:

[0053] 50% K 0.10 Fe 5.46 Ni 5.0 Mg 1.5 Pr 0.5 Bi 1.0 Mo 13 O x +50% SiO2. The average pore diameter of the catalyst is measured. Among them, P1 is 9.0 nm, P2 is 32.0 nm, Y = (32.0 - 9.0) / 9.0 = 2.6. The pore volume of pores with a pore diameter less than 5 nm and greater than 80 nm accounts for 2.5% of the total pore volume.

[0054] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the catalyst heat-treated at temperature T1 are as follows: On a millimeter fluidized bed reactor, the catalyst particle size is 50 μm, the reaction temperature: 430 °C; the reaction pressure: 0.084 MPa; the catalyst loading: 300 g; the catalyst propylene load (WWH): 0.085 h -1 ; The raw material ratio (mole): C3 ＝ / NH3 / Air = 1 / 1.25 / 9.6. After running for 300 hours, the reaction results are as follows: the conversion rate of propylene is 99.2%, and the selectivity of acrylonitrile is 85.1%.

[0055]

Example 2

[0056] Dissolve 704.9 g of (NH4)6Mo7O 24 ·4H2O in 577 g of water. At 50 °C, add 4400 g of silica sol with a weight concentration of 30% to form Slurry I, and the concentration of Slurry I is 35.6%. Dissolve 3.11 g of KOH, 74.1 g of Bi(NO3)3·5H2O, 444.7 g of Co(NO3)2·6H2O, 132.8 g of Nd(NO3)3·6H2O, 374.2 g of Fe(NO3)3·9H2O, 117.5 g of Mg(NO3)2·6H2O, and 101.8 g of Mn(NO3)2 in 94 g of water to obtain Solution I. The concentration of Solution I is 43.6%. Add Slurry I and Solution I to a separating funnel and carry out parallel flow precipitation in a parallel flow manner. At a temperature of 50 °C, control the time to 30 min. After adding all the materials, stir and mix for 30 min to form Slurry II. Form the prepared slurry into microspheres in a spray dryer, with a drying temperature of 300 °C, a drying time of 0.5 h, and an average spray droplet diameter of 100 μm to obtain particulate matter. Prepare two samples after spraying, and then in an atmosphere of a N2 mixture with a volume content of water of 0.5% and a volume content of oxygen of 25%, the gas flow rate per unit time of the mixture relative to the mass of the catalyst is 200 L / kg·h, and calcine at 550 °C (T1) and 700 °C (T2) for 1 h respectively to obtain the required catalyst samples.

[0057] The composition of the catalyst obtained according to the above steps is represented by the following formula:

[0058] 40% K 0.15 Fe 3.0 Co 5.0 Mn 1.0 Mg 1.5 Nd 1.0 Bi 0.5 Mo 13 O x +60% SiO2. The average pore diameter of the catalyst is measured, where P1 is 8.5 nm, P2 is 28.0 nm, Y = (28.0 - 8.5) / 8.5 = 2.3, and the pore volume of pores with a pore diameter less than 5 nm and greater than 80 nm accounts for 2.8% of the total pore volume.

[0059] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the catalyst heat-treated at the T1 temperature are as follows: On a millimeter fluidized bed reactor, the catalyst particle size is 50 microns, the reaction temperature is 430 °C; the reaction pressure is 0.084 MPa; the catalyst loading is 300 grams; the catalyst propylene load (WWH) is 0.085 per hour -1 ; Feed ratio (mole): C3 ＝ / NH3 / air = 1 / 1.25 / 9.6. After running for 300 hours, the reaction results are as follows: the propylene conversion rate is 99.5%, and the acrylonitrile selectivity is 85.1%.

[0060]

Example 3

[0061] Dissolve 1071.4 grams of (NH4)6Mo7O 24 ·4H2O in 877 g of water. At 50 °C, add 4400 grams of silica sol with a weight concentration of 30% to form slurry I, and the concentration of slurry I is 37.7%. Dissolve 10.27 grams of RbNO3, 112.7 grams of Bi(NO3)3·5H2O, 675.9 grams of Co(NO3)2·6H2O, 184.4 grams of La(NO3)3·6H2O, 568.7 grams of Fe(NO3)3·9H2O, 164.5 grams of Ca(NO3)2·6H2O, and 3.98 grams of CrO3 in 226 g of water to obtain solution I. The concentration of solution I is 43%. Add slurry I and solution I to a separating funnel and perform parallel flow precipitation in a parallel flow manner. At a temperature of 60 °C, control the time to 30 min. After adding the materials, stir and mix for 30 min to form slurry II. Form the prepared slurry into microspheres in a spray dryer, with a drying temperature of 300 °C, a drying time of 0.5 h, and an average spray droplet diameter of 100 μm to obtain particulate matter. Prepare two samples after spraying, and then in an atmosphere of N2 mixed gas with a volume content of water of 1.0% and a volume content of oxygen of 25%, the unit time input amount of the mixed gas relative to the catalyst mass ratio is 200 L / kg·h, and calcine at 550 °C (T1) and 700 °C (T2) for 1 h respectively to obtain the required catalyst samples.

[0062] The composition of the catalyst obtained according to the above steps is represented by the following formula:

[0063] 60% Rb 0.15 Fe 3.0 Co 5.0 Cr 0.1 Ca 1.5 La 1.0 Bi 0.5 Mo 13 O x+40% SiO2, the average pore diameter of the catalyst was measured, where P1 was 7.6 nm, P2 was 29.0 nm, Y = (29.0 - 7.6) / 7.6 = 2.8, and the volume of pores with a diameter less than 5 nm and greater than 80 nm accounted for 3.6% of the total pore volume.

[0064] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the catalyst calcined at temperature T1 were as follows: In a millimeter fluidized bed reactor, the catalyst particle size was 50 microns, the reaction temperature was 430 °C, the reaction pressure was 0.084 MPa, the catalyst loading was 300 g, and the catalyst propylene load (WWH) was 0.085 h-1. -1 ; The raw material ratio (molar): C3 ＝ / NH3 / air = 1 / 1.25 / 9.6. After running for 300 hours, the reaction results were as follows: the propylene conversion rate was 98.8%, and the acrylonitrile selectivity was 86.9%.

[0065]

Example 4

[0066] 869.5 g of (NH4)6Mo7O 24 ·4H2O was dissolved in 711 g of water. At 50 °C, 2475 g of a 40% silica sol and 110 g of ZrO2 were added to form Slurry I, and the concentration of Slurry I was 47.3%. 8.34 g of RbNO3, 91.4 g of Bi(NO3)3·5H2O, 553.7 g of Ni(NO3)2·6H2O, 65.7 g of Sm(NO3)3·6H2O, 384.6 g of Fe(NO3)3·9H2O, 119.7 g of Sr(NO3)2·6H2O, 21.5 g of H3PO4, and 3.81 g of CrO3 were dissolved in 129 g of water to obtain Solution I. The concentration of Solution I was 46%. Slurry I and Solution I were respectively added dropwise through a separating funnel in a co-current manner for co-precipitation. At a temperature of 60 °C, the time was controlled for 30 min. After the materials were added, they were stirred and mixed for 30 min to form Slurry II. The prepared slurry was formed into microspheres in a spray dryer. The drying temperature was 300 °C, the drying time was 0.5 h, and the average diameter of the spray droplets was 100 μm to obtain particulate matter. Two samples after spraying were prepared, and then in an atmosphere of a N2 mixture with a volume content of water of 2.0% and a volume content of oxygen of 25%, the gas flow rate per unit time relative to the mass of the catalyst was 200 L / kg·h, and they were calcined at 600 °C (T1) and 700 °C (T2) for 1 h respectively to obtain the required catalyst samples.

[0067] The composition of the catalyst obtained according to the above steps is represented by the following formula:

[0068] 50% Rb 0.15Fe 2.5 Ni 5.0 Cr 0.1 Sr 1.5 Sm 1.0 P 0.5 Bi 0.5 Mo 13 O x +45% SiO2 + 5% ZrO2. The average pore size of the catalyst was measured. Among them, P1 was 6.5 nm, P2 was 27.0 nm, Y = (27.0 - 6.5) / 6.5 = 3.2. The volume of pores with a pore size less than 5 nm and greater than 80 nm accounted for 3.9% of the total pore volume.

[0069] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the catalyst calcined at temperature T1 are as follows: In a millimeter fluidized bed reactor, the catalyst particle size was 50 microns, the reaction temperature was 430 °C, the reaction pressure was 0.084 MPa, the catalyst loading was 300 g, and the catalyst propylene load (WWH) was 0.085 h-1. -1 ; Feed ratio (mole): C3 ＝ / NH3 / air = 1 / 1.25 / 9.6. After running for 300 hours, the reaction results were as follows: The propylene conversion was 99.5%, and the acrylonitrile selectivity was 85.6%.

[0070]

Example 5

[0071] 890.9 g of (NH4)6Mo7O 24·4H2O was dissolved in 729 g of water. At 50 °C, 2750 g of silica sol 2 with a weight concentration of 40% was added to form slurry I, and the concentration of slurry I was 45.6%. 8.54 g of RbNO3, 93.7 g of Bi(NO3)3·5H2O, 567.3 g of Ni(NO3)2·6H2O, 67.3 g of Sm(NO3)3·6H2O, 315.3 g of Fe(NO3)3·9H2O, 122.6 g of Sr(NO3)2·6H2O, and 10.3 g of Pd(NO3)2 were dissolved in 129 g of water to obtain solution I. The concentration of solution I was 47.1%. Slurry I and solution I were subjected to concurrent precipitation through a separating funnel in a concurrent flow manner. At a temperature of 60 °C, the time was controlled for 30 min. After the materials were added, they were stirred and mixed for 30 min to form slurry II. The prepared slurry was subjected to microsphere granulation in a spray dryer. The drying temperature was 300 °C, the drying time was 0.5 h, and the average diameter of the spray droplets was 100 μm to obtain particulate matter. Two samples after spraying were prepared, and then in an atmosphere of a N2 mixture with a volume content of water of 3.0% and a volume content of oxygen of 25%, the gas flow rate per unit time of the mixture relative to the mass of the catalyst was 200 L / kg·h, and they were calcined at 550 °C (T1) and 700 °C (T2) for 1 h respectively to obtain the required catalyst samples.

[0072] The composition of the catalyst obtained according to the above steps is represented by the following formula:

[0073] 50% Pd 0.1 Rb 0.15 Fe 2.0 Ni 5.0 Cr 0.1 Sr 1.5 Sm 1.0 Bi 0.5 Mo 13 O x + 50% SiO2. The average pore diameter of the catalyst was measured, where P1 was 5.8 nm, P2 was 26.50 nm, Y = (26.5 - 5.8) / 5.8 = 3.6, and the pore volume of the pores with a pore diameter less than 5 nm and greater than 80 nm accounted for 1.4% of the total pore volume.

[0074] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the catalyst calcined at the T1 temperature are as follows: On a millimeter fluidized bed reactor, the catalyst particle size was 50 μm, the reaction temperature: 430 °C; the reaction pressure: 0.084 MPa; the catalyst loading: 300 g; the catalyst propylene load (WWH): 0.085 h -1 ; Feed ratio (mol): C3 ＝ / NH3 / Air = 1 / 1.25 / 9.6. After running for 300 hours, the reaction results are as follows: the conversion rate of propylene is 98.3%, and the selectivity of acrylonitrile is 83.8%.

[0075]

Example 6

[0076] Dissolve 984.0 g of (NH4)6Mo7O 24 ·4H2O in 805 g of water. At 50 °C, add 2750 g of silica sol 2 with a weight concentration of 40% to form slurry I, and the concentration of slurry I is 45.6%. Dissolve 8.54 g of RbNO3, 103.5 g of Bi(NO3)3·5H2O, 626.6 g of Ni(NO3)2·6H2O, 36.7 g of Pr(NO3)3·6H2O, 261.2 g of Fe(NO3)3·9H2O, 164.1 g of Mg(NO3)2·6H2O, 4.71 g of CrO3, and 13.22 g of Nb2(C2O4)5 in 144 g of water to obtain solution I. The concentration of solution I is 47.3%. Add slurry I and solution I to a separating funnel and perform co-current precipitation in a co-current manner. At a temperature of 60 °C, control the time to 30 min. After adding all the materials, stir and mix for 30 min to form slurry II. Shape the prepared slurry into microspheres in a spray dryer. The drying temperature is 300 °C, the drying time is 0.5 h, and the average diameter of the spray droplets is 100 μm to obtain particulate matter. Prepare two samples after spraying, and then in an atmosphere of a N2 mixture with a volume content of water of 3.0% and a volume content of oxygen of 25%, the hourly feed rate of the mixture relative to the mass of the catalyst is 200 L / kg·h, and calcine at 550 °C (T1) and 700 °C (T2) for 1 h respectively to obtain the required catalyst samples.

[0077] The composition of the catalyst obtained according to the above steps is represented by the following formula:

[0078] 50% Nb 0.1 Rb 0.10 Fe 1.5 Ni 5.0 Cr 0.1 Mg 1.5 Pr 0.2 Bi 0.5 Mo 13 O x +50% SiO2. The average pore diameter of the catalyst is measured. Among them, P1 is 9.1 nm, P2 is 38.5 nm, Y = (38.5 - 9.1) / 9.1 = 3.2, and the pore volume of pores with a pore diameter less than 5 nm and greater than 80 nm accounts for 1.2% of the total pore volume.

[0079] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the catalyst calcined at temperature T1 are as follows: In a millimeter fluidized bed reactor, the catalyst particle size is 50 microns, the reaction temperature is 430 °C; the reaction pressure is 0.084 MPa; the catalyst loading is 300 g; the catalyst propylene load (WWH) is 0.085 h-1. -1 ; The raw material ratio (molar): C3 ＝ / NH3 / air = 1 / 1.25 / 9.6. After running for 300 hours, the reaction results are as follows: the propylene conversion rate is 99.1%, and the acrylonitrile selectivity is 86.1%.

[0080]

Comparative Example 1

[0081] Dissolve 836.6 g of (NH4)6Mo7O 24 ·4H2O in 684 g of water. At 50 °C, add 2750 g of silica sol with a weight concentration of 40% to form Slurry I, and the concentration of Slurry I is 46.8%. Dissolve 2.46 g of KOH, 175.9 g of Bi(NO3)3·5H2O, 532.7 g of Ni(NO3)2·6H2O, 78.1 g of Pr(NO3)3·6H2O, 808.2 g of Fe(NO3)3·9H2O, and 139.5 g of Mg(NO3)2·6H2O in 195 g of water to obtain Solution I. The concentration of Solution I is 49.5%. Add Slurry I to Solution I and stir and mix for 30 min to form Slurry II. The prepared slurry is subjected to microsphere granulation in a spray dryer, the drying temperature is 300 °C, the drying time is 0.5 h, and the average diameter of the spray droplets is 100 μm to obtain particulate matter. Prepare two samples after spraying, and then in an atmosphere of a N2 mixture with a volume content of water of 0.5% and a volume content of oxygen of 25%, the hourly feed rate of the mixture relative to the catalyst mass ratio is 200 L / kg·h, and calcine at 550 °C (T1) and 700 °C (T2) for 1 h respectively to obtain the required catalyst samples.

[0082] The composition of the catalyst obtained according to the above steps is represented by the following formula:

[0083] 50% K 0.10 Fe 5.46 Ni 5.0 Mg 1.5 Pr 0.5 Bi 1.0 Mo 13 O x+50% SiO2, the average pore diameter of the catalyst was measured, where P1 was 5.2 nm, P2 was 39.0 nm, Y = (39.0 - 5.2) / 5.2 = 6.5, and the pore volume of pores with a pore diameter less than 5 nm and greater than 80 nm accounted for 7.2% of the total pore volume.

[0084] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the catalyst calcined at temperature T1 were as follows: In a millimeter fluidized bed reactor, the catalyst particle size was 50 microns, the reaction temperature was 430 °C; the reaction pressure was 0.084 MPa; the catalyst loading was 300 g; the catalyst propylene load (WWH) was 0.085 h-1 -1 ; The raw material ratio (molar): C3 ＝ / NH3 / air = 1 / 1.25 / 9.6. After running for 300 hours, the reaction results were as follows: the propylene conversion was 99.2%, and the acrylonitrile selectivity was 79.6%.

[0085]

Comparative Example 2

[0086] 704.9 g of (NH4)6Mo7O 24 ·4H2O was dissolved in 577 g of water. At 50 °C, 4400 g of a 30% silica sol by weight was added to form Slurry I, and the concentration of Slurry I was 35.6%. 3.11 g of KOH, 74.1 g of Bi(NO3)3·5H2O, 444.7 g of Co(NO3)2·6H2O, 132.8 g of Nd(NO3)3·6H2O, 374.2 g of Fe(NO3)3·9H2O, 117.5 g of Mg(NO3)2·6H2O, and 101.8 g of Mn(NO3)2 were dissolved in 94 g of water to obtain Solution I. The concentration of Solution I was 43.6%. Solution I was added to Slurry I and stirred and mixed for 30 min to form Slurry II. The prepared slurry was subjected to microsphere granulation in a spray dryer at a drying temperature of 300 °C, a drying time of 0.5 h, and an average spray droplet diameter of 100 μm to obtain particulate matter. Two samples after spraying were prepared, and then in an atmosphere of a N2 mixture with a water volume content of 0.5% and an oxygen volume content of 25%, the gas flow rate per unit time of the mixture relative to the mass of the catalyst was 200 L / kg·h, and they were calcined at 550 °C (T1) and 700 °C (T2) for 1 h respectively to obtain the required catalyst samples.

[0087] The composition of the catalyst obtained according to the above steps is represented by the following formula:

[0088] 40% K 0.15 Fe 3.0 Co 5.0 Mn 1.0 Mg 1.5 Nd1.0 Bi 0.5 Mo 13 O x +60% SiO2. The average pore diameter of the catalyst was measured. Among them, P1 was 7.1 nm, P2 was 38.0 nm, Y = (38.0 - 7.1) / 7.1 = 6.4. The volume of pores with a pore diameter less than 5 nm and greater than 80 nm accounted for 7.5% of the total pore volume.

[0089] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the catalyst calcined at temperature T1 are as follows: In a millimeter fluidized bed reactor, the catalyst particle size was 50 microns, the reaction temperature was 430 °C, the reaction pressure was 0.084 MPa, the catalyst loading was 300 g, and the catalyst propylene load (WWH) was 0.085 h-1. -1 ; Feed ratio (molar): C3 ＝ / NH3 / air = 1 / 1.25 / 9.6. After running for 300 hours, the reaction results were as follows: the propylene conversion rate was 99.7%, and the acrylonitrile selectivity was 80.9%.

[0090] [Comparative Example 3]

[0091] 1071.4 g of (NH4)6Mo7O 24 ·4H2O and 184.4 g of La(NO3)3·6H2O were dissolved in 907 g of water. At 50 °C, 4400 g of a 30% silica sol by weight was added to form Slurry I, and the concentration of Slurry I was 37.7%. 10.27 g of RbNO3, 112.7 g of Bi(NO3)3·5H2O, 675.9 g of Co(NO3)2·6H2O, 568.7 g of Fe(NO3)3·9H2O, 164.5 g of Ca(NO3)2·6H2O, and 3.98 g of CrO3 were dissolved in 196 g of water to obtain Solution I. The concentration of Solution I was 43%. Slurry I and Solution I were separately added through a separating funnel in a co-current manner for co-current precipitation. At a temperature of 90 °C, the time was controlled for 30 min. After the materials were added, they were stirred and mixed for 30 min to form Slurry II. The prepared slurry was formed into microspheres in a spray dryer. The drying temperature was 300 °C, the drying time was 0.5 h, and the average diameter of the spray droplets was 100 μm to obtain particulate matter. Two samples after spraying were prepared, and then in an atmosphere of a N2 mixture with a volume content of water of 1.0% and a volume content of oxygen of 25%, the gas flow rate per unit time of the mixture relative to the mass of the catalyst was 200 L / kg·h, and they were calcined at 550 °C (T1) and 700 °C (T2) for 1 h respectively to obtain the required catalyst samples.

[0092] The composition of the catalyst obtained according to the above steps is represented by the following formula:

[0093] 60% Rb 0.15 Fe 3.0 Co 5.0 Cr 0.1 Ca 1.5 La 1.0 Bi 0.5 Mo 13 O x + 40% SiO2. The average pore diameter of the catalyst was measured. Among them, P1 was 6.7 nm, P2 was 39.0 nm, Y = (39.0 - 6.7) / 6.7 = 4.8. The pore volume of the pores with a pore diameter less than 5 nm and greater than 80 nm accounted for 7.6% of the total pore volume.

[0094] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the catalyst calcined at temperature T1 are as follows: On a millimeter fluidized bed reactor, the catalyst particle size was 50 microns, the reaction temperature: 430 °C; the reaction pressure: 0.084 MPa; the catalyst loading: 300 g; the catalyst propylene load (WWH): 0.085 h -1 ; Feed ratio (molar): C3 ＝ / NH3 / air = 1 / 1.25 / 9.6. After running for 300 hours, the reaction results were as follows: The propylene conversion rate was 98.5%, and the acrylonitrile selectivity was 77.1%.

[0095]

Comparative Example 4

[0096] 836.6 g of (NH4)6Mo7O 24 ·4H2O was dissolved in 684 g of water. At 50 °C, 2750 g of silica sol with a weight concentration of 40% was added to form Slurry I, and the mass concentration of Slurry I was 46.8%. 2.46 g of KOH, 175.9 g of Bi(NO3)3·5H2O, 532.7 g of Ni(NO3)2·6H2O, 78.1 g of Pr(NO3)3·6H2O, 808.2 g of Fe(NO3)3·9H2O, and 139.5 g of Mg(NO3)2·6H2O were dissolved in 195 g of water to obtain Solution I. The mass concentration of Solution I was 49.5%. Slurry I and Solution I were separately precipitated in parallel through a separating funnel. At a temperature of 40 °C, the time was controlled for 20 min. After the materials were added, they were stirred and mixed for 30 min to form Slurry II. The prepared slurry was formed into microspheres in a spray dryer. The drying temperature was 300 °C, the drying time was 0.5 h, and the average diameter of the spray droplets was 100 μm to obtain particulate matter. Then it was calcined in an air atmosphere at 700 °C for 1 h to obtain the required catalyst sample.

[0097] The composition of the catalyst obtained according to the above steps is represented by the following formula:

[0098] 50% K 0.10 Fe 5.46 Ni 5.0 Mg 1.5 Pr 0.5 Bi 1.0 Mo 13 O x + 50% SiO2,

[0099] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the above catalyst are as follows: In a millimeter fluidized bed reactor, the catalyst particle size is 50 microns, the reaction temperature is 430 °C; the reaction pressure is 0.084 MPa; the catalyst loading is 300 g; the catalyst propylene load (WWH) is 0.085 h -1 ; Feed ratio (mole): C3 ＝ / NH3 / air = 1 / 1.25 / 9.6. After running for 300 hours, the reaction results are as follows: the propylene conversion rate is 96.1%, and the acrylonitrile selectivity is 78.3%.

[0100] Table 1 Composition and evaluation results of the catalyst particles obtained in each example and comparative example

[0101]

[0102] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. An ammonia oxidation catalyst, wherein the active components of the catalyst include molybdenum and bismuth, and the carrier includes silica. The change in the average pore diameter of the catalyst after heat treatment conforms to formula (I): Y = (P2 - P1) / P1 (I), Among them, The value of Y is less than or equal to 4.

5. P2 is the average pore diameter of the catalyst after heat treatment at temperature T2 and in a water-containing atmosphere, and P1 is the average pore diameter of the catalyst after heat treatment at temperature T1 and in a water-containing atmosphere. And T2 > T1, T2 ≤ 750 °C; temperature T1 is 400 - 600 °C; temperature T2 is 500 - 750 °C; the heat treatment time is 0.5 - 4 h; temperature T2 is at least 50 °C higher than temperature T1; The active components include molybdenum and bismuth. Based on the weight of the catalyst, the weight content of molybdenum calculated as MoO3 is 15% - 55%, and the weight content of bismuth calculated as Bi2O3 is 0.5% - 3.5%; the atomic ratio of Bi / Mo is 0.008 - 0.25; The preparation method of the catalyst includes the following steps: (1) A basic material containing molybdenum and a carrier precursor and an acidic material containing a bismuth-containing active component precursor are subjected to co-current precipitation reaction to obtain slurry I; (2) The slurry I is spray-dried and heat-treated to obtain the catalyst.

2. The catalyst according to claim 1, characterized in that, The value of Y is 0.5 - 4.

5.

3. The catalyst according to claim 2, characterized in that, The value of Y is 1.5 - 4.

0.

4. The catalyst according to claim 1, characterized in that, Temperature T1 is 450 - 600 °C; temperature T2 is 550 - 700 °C; And / or, the heat treatment time is 0.5 - 2 h.

5. The catalyst according to claim 1, characterized in that, The heat treatment is carried out in an atmosphere of a continuously flowing mixed gas of water and oxygen, wherein in the mixed gas, the volume content of water is 0.01% - 4.5%, the volume content of oxygen is 10% - 30%, and the ratio of the unit time throughput of the mixed gas to the mass of the catalyst is 50 - 500 L / kg·h.

6. The catalyst according to claim 1, characterized in that, The active components include molybdenum and bismuth. Based on the weight of the catalyst, the weight content of molybdenum calculated as MoO3 is 20% - 45%, and the weight content of bismuth calculated as Bi2O3 is 1.0% - 3.5%.

7. The catalyst according to claim 1, characterized in that, In the active components, the atomic ratio of Bi / Mo is 0.01 - 0.

20.

8. The catalyst according to claim 1, characterized in that, The active components further include Fe, rare earth elements, alkali metal elements, alkaline earth metal elements, and metal element A; the metal element A is selected from at least one of W, V, Zr, P, Nb, Ni, Co, Cr, Mn, Tl, Au, Ag, Pt, Ru, Rh, Pd, Ti, Sb, In, Sn, Te.

9. The catalyst according to claim 8, characterized in that, The metal element A is selected from at least one of Co, Mn, P, Pd, Nb.

10. The catalyst according to claim 8, characterized in that, Based on the weight of the catalyst, the weight content of molybdenum calculated as MoO3 is 15% - 55%, the weight content of bismuth calculated as Bi2O3 is 0.5% - 3.5%, the weight content of the Fe element calculated as Fe2O3 is 1% - 12%, the weight content of the alkali metal element calculated as an oxide is 0.01% - 0.60%, the weight content of the alkaline earth metal calculated as an oxide is 0.01% - 4.0%, and the weight content of the metal element A calculated as an oxide is 0.01% - 15%.

11. The catalyst according to claim 10, characterized in that, Based on the weight of the catalyst, the weight content of molybdenum calculated as MoO3 is 20% - 45%, the weight content of bismuth calculated as Bi2O3 is 1.0% - 3.5%, the weight content of Fe element calculated as Fe2O3 is 1.5% - 11%, the weight content of alkali metal element calculated as oxide is 0.05% - 0.55%, the weight content of alkaline earth metal calculated as oxide is 0.5% - 3.5%, and the weight content of metal element A calculated as oxide is 0.05% - 14%.

12. The catalyst according to claim 10, characterized in that, In the catalyst, the atomic ratio of Bi / Mo is 0.008 - 0.25; and / or, the atomic ratio of Fe / Bi is 1.0 - 7.0; and / or, the atomic ratio of (rare earth element + alkali metal element + alkaline earth metal element) / Mo is 0.05 - 0.40; and / or, the atomic ratio of A / Mo is 0.01 - 1.

0.

13. The catalyst according to claim 12, characterized in that, In the catalyst, the atomic ratio of Bi / Mo is 0.01 - 0.20; and / or, the atomic ratio of Fe / Bi is 2.0 - 6.0; and / or, the atomic ratio of (rare earth element + alkali metal element + alkaline earth metal element) / Mo is 0.10 - 0.35; and / or, the atomic ratio of A / Mo is 0.02 - 0.

9.

14. The catalyst according to claim 1, 8 or 10, characterized in that, Based on the weight of the catalyst, the content of the active component calculated as oxide is 20% - 80%, and the content of the carrier is 20% - 80%.

15. The catalyst according to claim 1, characterized in that, The catalyst is in granular form, and its average particle size is 30 - 70 μm.

16. The catalyst according to claim 15, characterized in that, The catalyst is in granular form, and its average particle size is 40 - 60 μm.

17. A preparation method of the catalyst according to any one of claims 1 - 16, comprising the following steps: (1) A basic material containing molybdenum and a carrier precursor and an acidic material containing a bismuth-containing active component precursor are subjected to co-current precipitation reaction to obtain slurry I; (2) The slurry I is spray-dried and heat-treated to obtain the catalyst.

18. The preparation method according to claim 17, wherein, The carrier precursor in step (1) includes silica sol; in the silica sol, the solid content calculated as silicon dioxide is 20wt% - 50wt%, and the average particle size is 10 - 35 nm; and / or, in the basic material containing molybdenum and the carrier precursor in step (1), the mass concentration of the material is controlled at 20% - 55%; and / or, in the acidic material containing the bismuth-containing active component precursor in step (1), the mass concentration of the material is controlled at 20% - 60%.

19. The preparation method according to claim 17, characterized in that, The time of co-current precipitation in step (1) is 10 - 40 min, and the temperature is controlled at 20 - 60 °C.

20. The preparation method according to claim 19, wherein The time of co-current precipitation in step (1) is 10 - 25 min.

21. The preparation method according to claim 19, characterized in that, In step (1), after the materials are added, further stirring and mixing are carried out, and the mixing time is 10 - 30 min.

22. The preparation method according to claim 19, wherein, In step (1), after the materials are added, further stirring and mixing are carried out, and the mixing time is 10 - 25 min.

23. The preparation method according to any one of claims 17-22, characterized in that, In the acidic material containing the bismuth-containing active component precursor in step (1), precursors of Fe, rare earth element, alkali metal element, alkaline earth metal element, and metal element A are also included.

24. The preparation method according to claim 17, characterized in that, The conditions of the spray drying described in step (2) include: the drying heat source is air, the drying temperature is 250 - 350 °C, the drying time is 0.1 - 2.0 h, and the average diameter of the spray droplets is 20 - 200 μm; and / or, the heat treatment described in step (2) is a high-temperature roasting treatment in a water-containing atmosphere.

25. The preparation method according to claim 24, characterized in that, The conditions of the spray drying described in step (2) include: the drying temperature is 300 - 350 °C, the drying time is 0.2 - 1.0 h, and the average diameter of the spray droplets is 40 - 180 μm.

26. The preparation method according to claim 24, characterized in that, The conditions of the heat treatment described in step (2) are as follows: the temperature is 500 - 750 °C, the time is 0.2 - 4 h, and the heat treatment is carried out in an atmosphere of a continuously flowing mixed gas containing water and oxygen, wherein in the mixed gas, the volume content of water is 0.01% - 4.5%, the volume content of oxygen is 10% - 30%, and the ratio of the amount of the mixed gas introduced per unit time to the mass of the catalyst is 50 - 500 L / kg·h.

27. A method for preparing acrylonitrile by ammoxidation of propylene, comprising: The step of subjecting propylene to ammoxidation to produce acrylonitrile in the presence of the catalyst according to any one of claims 1 - 16 or the catalyst prepared by the preparation method according to any one of claims 17 - 26.

28. The method according to claim 27, wherein The reaction conditions for the ammoxidation of propylene to acrylonitrile include: the molar ratio of propylene / ammonia / air in terms of O2 is 1:1.1 - 1.35:1.8 - 2.5, the reaction temperature is 420 - 440 °C, the reaction pressure is 0.03 - 0.14 MPa in gauge pressure, and the weight hourly space velocity is 0.04 - 0.10 h -1 .

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