Mo-Bi-based catalyst as well as preparation method and application thereof

Abstract

The invention discloses a Mo-Bi-based catalyst and a preparation method and application thereof.The catalyst comprises active components, the active components comprise spherical particles and molybdenum oxide nanorods attached to the surfaces of the spherical particles, and the spherical particles contain molybdenum and / or molybdenum oxide and bismuth and / or bismuth oxide. When the catalyst is applied to propylene oxidation synthesis of acrolein, the catalyst has the technical effect of high acrolein selectivity.

Description

Technical Field

[0001] The present invention belongs to the technical field of acrolein synthesis methods, and particularly relates to a Mo-Bi based catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] Acrolein is mainly used for the production of important chemical products such as methionine, methylpyridine, pyridine, glutaraldehyde, and acrylic acid. Industrially, acrolein is prepared by the propylene oxidation method. Under the action of a Mo-Bi composite oxide catalyst, propylene is oxidized to form acrolein, releasing a large amount of heat, along with peroxidation products such as acrylic acid, acetaldehyde, acetic acid, CO, and CO2. Although there are also synthetic routes for preparing acrolein using propane or acetylene as raw materials, they are inferior to the propylene oxidation method in terms of conversion rate, selectivity, etc. The poor technical economy factor has led to no large-scale application.

[0003] Common preparation methods for acrolein catalysts prepared by propylene oxidation mostly involve making metal compounds into solutions, then adding insoluble oxides for evaporation, and then drying, pulverizing, forming, and activating, etc. However, the catalysts obtained by traditional preparation methods have low acrolein selectivity and produce more acrylic acid, resulting in a high unit consumption of acrolein. Moreover, MoO3 in the Mo-Bi catalyst is usually in the core of the catalyst to supplement the Mo lost during long-term use as a Mo source. For example, in patent CN 101690900 A, it mainly focuses on the total yield of acrolein and acrylic acid and does not care about the selectivity of acrolein itself. Summary of the Invention

[0004] One of the technical problems to be solved by the present invention is the problem of low acrolein selectivity in the reaction of propylene oxidation to synthesize acrolein in the prior art. A Mo-Bi catalyst is provided, and when the catalyst is applied to the propylene oxidation to synthesize acrolein, it has the technical effect of high acrolein selectivity.

[0005] One of the objects of the present invention is to provide a Mo-Bi based catalyst, which includes active components. The active components include spherical particles and molybdenum oxide nanorods attached to the surface of the spherical particles. Among them, the spherical particles contain molybdenum and / or its oxides, bismuth and / or its oxides.

[0006] In a preferred embodiment, in the spherical particles, the molar ratio of molybdenum element to bismuth element is 12:(0.05 - 5), for example, 12:0.05, 12:0.08, 12:0.1, 12:0.2, 12:0.5, 12:0.8, 12:1, 12:2, 12:3, 12:4, or 12:5.

[0007] In a preferred embodiment, the molybdenum oxide nanorods are MoO3 nanorods.

[0008] In a preferred embodiment, the general formula of the spherical particles is Mo 12 Bi g Fe f Co m M y O x , where M is at least one of Ni, Mn, Ce, Zr, and Nb, g = 0.05 to 5, f = 0.05 to 5, m = 0.05 to 5, y = 0.05 to 10, and x is a value determined by the total valence of the elements other than oxygen in the general formula.

[0009] For example, g = 0.05, 0.08, 0.1, 0.2, 0.5, 0.8, 1, 2, 3, 4, or 5, f = 0.05, 0.08, 0.1, 0.2, 0.5, 0.8, 1, 2, 3, 4, or 5, m = 0.05, 0.08, 0.1, 0.2, 0.5, 0.8, 1, 2, 3, 4, or 5, and y = 0.05, 0.1, 0.5, 1, 2, 4, 6, 8, or 10

[0010] In a preferred embodiment, the average diameter of the spherical particles is 5 to 100 μm, preferably 20 to 60 μm, such as 5 μm, 10 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 70 μm, 80 μm, 90 μm, or 100 μm.

[0011] In a preferred embodiment, the average length of the MoO3 nanorods is 50 - 500 nm, and / or the average diameter of the MoO3 nanorods is 5 - 50 nm, and / or the aspect ratio of the MoO3 nanorods is 4 - 20.

[0012] For example, the average length of the MoO3 nanorods is 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, or 500 nm, and / or the average diameter is 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 nm, and / or the aspect ratio is 4, 5, 10, 15, or 20.

[0013] In a preferred embodiment, the MoO3 nanorods are laterally attached (i.e., lying horizontally) to the multi-component matrix.

[0014] In a preferred embodiment, the catalyst further includes a carrier for supporting the active component.

[0015] Wherein, the carrier and the active component are physically mixed to obtain the catalyst.

[0016] In a further preferred embodiment, the carrier is selected from one or more of SiO2, Al2O3, CeO2, and TiO2.

[0017] In a preferred embodiment, based on 100 wt% of the catalyst, it comprises 20 - 90 wt% of the active component and 10 - 80 wt% of the carrier.

[0018] For example, based on 100 wt% of the catalyst, the active component accounts for 20 wt%, 30 wt%, 40 wt%, 50 wt%, 6 wt%, 70 wt%, or 80 wt%, and the carrier accounts for 20 wt%, 30 wt%, 40 wt%, 50 wt%, 6 wt%, 70 wt%, or 80 wt%.

[0019] In a further preferred embodiment, based on 100 wt% of the catalyst, it comprises 20 - 80 wt% of the active component and 20 - 80 wt% of the carrier.

[0020] A second object of the present invention is to provide a method for preparing a Mo - Bi - based catalyst, preferably for preparing the catalyst described in the first object of the present invention. The preparation method includes:

[0021] (1) Spray - drying an aqueous dispersion containing raw material compounds to obtain a powder, and then pre - calcining the powder to obtain the spherical particles; wherein, the raw material compounds include a molybdenum - containing compound, a bismuth - containing compound, an optional iron - containing compound, an optional cobalt - containing compound, and an optional M - element - containing compound;

[0022] (2) Immersing and adsorbing the spherical particles in an aqueous molybdate solution and drying to obtain a precursor of the active component.

[0023] (3) Mixing the precursor of the active component with a carrier raw material, followed by shaping and calcining to obtain the catalyst for acrolein synthesis.

[0024] In a preferred embodiment, in step (1), the molybdenum - containing compound, the bismuth - containing compound, the iron - containing compound, the cobalt - containing compound, and the M - element - containing compound are respectively selected from the corresponding oxygen - containing salts of their metal elements; preferably, the molar ratio of Mo / Bi / Fe / Co / M in the molybdenum - containing compound, the bismuth - containing compound, the iron - containing compound, the cobalt - containing compound, and the M - element - containing compound is 12:(0.5 - 5.0):(0.5 - 5.0):(0.5 - 5.0):(0.05 - 10); and / or,

[0025] In a preferred embodiment, in step (1), the conditions for pre-baking include: the temperature is 260-500 °C, and the time is 0.5-8 h; preferably, the temperature is 320-450 °C, and the time is 1-4 h.

[0026] In a preferred embodiment, in step (1), the total concentration of the raw material compounds in the aqueous dispersion is 5-70 wt%, preferably 20-50 wt%; for example, it is 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt% or 70 wt%.

[0027] In a preferred embodiment, in step (1), the molybdenum-containing compound is selected from at least one of ammonium heptamolybdate and / or its hydrate, ammonium tetramolybdate and / or its basic hydrate, preferably from an aqueous solution of basic ammonium tetramolybdate and / or an aqueous solution of ammonium heptamolybdate;

[0028] In a further preferred embodiment, the bismuth-containing compound, iron-containing compound, cobalt-containing compound, and M-element-containing compound are each selected from at least one of the nitrates corresponding to their metal elements and / or their hydrates.

[0029] In a preferred embodiment, the concentration of the aqueous molybdate solution in step (2) is 1-40 wt%, more preferably 5-35 wt%.

[0030] For example, the concentration of the aqueous molybdate solution in step (2) is 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt% or 50 wt%.

[0031] In a further preferred embodiment, the aqueous molybdate solution in step (2) is selected from at least one of ammonium tetramolybdate and / or its basic hydrate, ammonium heptamolybdate and / or its aqueous solution, preferably from ammonium tetramolybdate and / or its basic hydrate.

[0032] Among them, the inventors found through experiments that using ammonium tetramolybdate and / or its basic hydrate in step (2) can promote the formation of MoO3 nanorods.

[0033] In a preferred embodiment, the molar ratio of Mo in the dispersion for preparing the raw material compounds to Mo in the aqueous molybdate solution is 5-50, for example, it is 5, 10, 15, 20, 25, 30, 35, 40, 45 or 50.

[0034] That is, the molar ratio of molybdenum in the molybdenum-containing compound in step (1) to molybdenum in the aqueous molybdate solution in step (2).

[0035] In a preferred embodiment, in step (3), the calcination temperature is 200 - 1000 °C, preferably 300 - 650 °C; and / or, the calcination time is 0.5 - 100 hours, preferably 24 - 72 h.

[0036] For example, in step (3), the calcination temperature is 200 °C, 300 °C, 400 °C, 500 °C, 600 °C, 700 °C, 800 °C, 900 °C or 1000 °C; and / or, the calcination time is 0.5, 1, 10, 20, 30, 40, 50, 60, 70, 80, 90 or 100 hours.

[0037] In a preferred embodiment, in step (3), the carrier raw material is selected from one or more of SiO2, Al2O3, CeO2, TiO2 and their precursors.

[0038] In a further preferred embodiment, based on 100 parts by total weight of the active component and the carrier raw material, the dosage of the active component is 20 - 90 parts, and the dosage of the carrier is 10 - 80 parts.

[0039] For example, based on 100 parts by total weight of the active component and the carrier raw material, the dosage of the active component is 20 parts, 30 parts, 40 parts, 50 parts, 60 parts, 70 parts, 80 parts or 90 parts, and the dosage of the carrier is 10 parts, 20 parts, 30 parts, 40 parts, 50 parts, 60 parts, 70 parts or 80 parts.

[0040] In a still further preferred embodiment, based on 100 parts by total weight of the active component and the carrier raw material, the dosage of the active component is 50 - 90 parts, and the dosage of the carrier is 10 - 50 parts.

[0041] The third object of the present invention is to provide the application of the Mo - Bi - based catalyst described in the first object of the present invention or the Mo - Bi - based catalyst prepared by the preparation method described in the second object of the present invention in the synthesis of acrolein.

[0042] In a preferred embodiment, the application includes contacting the catalyst with propylene at a reaction temperature of 330 - 380 °C and a space velocity of 80 - 130 h -1 -1.

[0043] For example, the reaction temperature is 330 °C, 340 °C, 350 °C, 360 °C, 370 °C or 380 °C, and the space velocity is 80 h -1 -1, 90 h -1 -1, 100 h -1 -1, 110 h -1 -1, 120 h -1 -1 or 130 h-1 。

[0044] In a preferred embodiment, the temperature of the reaction is 300 - 400 °C, preferably 330 - 380 °C.

[0045] In a further preferred embodiment, the reaction is carried out in the presence of water vapor and air.

[0046] Compared with the prior art, the present invention has the following beneficial effects: when the catalyst is used for synthesizing acrolein, it has the advantages of high propylene conversion rate and high acrolein selectivity. Description of the Drawings

[0047] Figure 1 The SEM diagram of the active component in the catalyst obtained in Example 1 of the present invention is shown.

[0048] In Figure 1 , the microsphere is the multi-component microsphere, the rod lying horizontally on the surface of the microsphere is the MoO3 nanorod, and the MoO3 nanorod lies horizontally or is attached horizontally to the multi-component microsphere.

[0049] Figure 2 For Figure 1 is a partial enlarged view. Detailed Embodiments

[0050] The present invention will be specifically described below in conjunction with specific embodiments. It is necessary to point out here that the following embodiments are only for further illustration of the present invention and cannot be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art according to the content of the present invention still fall within the protection scope of the present invention.

[0051] In addition, it should be noted that the various specific technical features described in the following detailed embodiments can be combined in any appropriate manner without conflict. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0052] In addition, any combination can be made between various different embodiments of the present invention as long as it does not violate the idea of the present invention. The technical solutions thus formed belong to a part of the original disclosure content of this specification and also fall within the protection scope of the present invention.

[0053] If there is no special limitation on the raw materials used in the examples and comparative examples, they are all disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0054] Propylene conversion rate = (moles of propylene consumed in the reaction / total moles of propylene input into the reaction) * 100%;

[0055] Selectivity of acrolein = number of moles of acrolein produced / number of moles of acrolein theoretically produced * 100%;

[0056] Single-pass yield of acrolein = conversion rate of propylene * selectivity of acrolein.

[0057]

Example 1

[0058] Dissolve 55.0 g of bismuth nitrate pentahydrate, 49.5 g of cobalt nitrate hexahydrate, 57.8 g of iron nitrate nonahydrate, and 64.8 g of zirconium nitrate pentahydrate in 100 g of water. Then add 1000 g of an aqueous solution of 20 wt% ammonium heptamolybdate ((NH4)6Mo7O 24 ·4H2O). After stirring for 10 min, spray dry. The obtained powder is calcined in a muffle furnace at 400 °C for 4 h to obtain 232 g of precursor (I).

[0059] Then add 232 g of precursor (I) to 54 g of an ammonia solution of 25 wt% ammonium dimolybdate tetrahydrate ((NH4)2Mo4O 13 ·2H2O). After stirring evenly, dry at 80 °C for 24 h to obtain precursor (II).

[0060] Take 400 g of the obtained precursor (II), 100 g of Al2O3, 5 g of graphite, and 10 g of deionized water, mix them evenly, set the tableting pressure at 3 kN through a tableting machine, and tablet them into a circular tablet-shaped catalyst with a diameter of 5 mm and a thickness of 4 mm. Finally, calcine at 505 °C for 24 h to obtain the catalyst for acrolein synthesis.

[0061] Observe the microstructure of the obtained catalyst by scanning electron microscopy (SEM), as shown in the appendix Figure 1 and 2 shown. It can be seen that the active components in the catalyst include spherical particles and nanorods attached to the surface of the spherical particles. Among them, the average diameter of the spherical particles is about 40 μm, the average length of the MoO3 nanorods is about 260 nm, the average diameter of the MoO3 nanorods is about 65 nm, and the average aspect ratio of the MoO3 nanorods is 4.

[0062]

Example 2

[0063] Dissolve 55.0 g of bismuth nitrate pentahydrate, 49.5 g of cobalt nitrate hexahydrate, 57.8 g of iron nitrate nonahydrate, and 44.4 g of nickel nitrate hexahydrate in 100 g of water. Then add 1000 g of an aqueous solution of 20 wt% ammonium heptamolybdate ((NH4)6Mo7O 24 ·4H2O). After stirring for 10 min, spray dry. The obtained powder is calcined in a muffle furnace at 400 °C for 4 h to obtain 225 g of precursor (I).

[0064] Then, 225 g of the obtained precursor (I) was added to 90 g of an aqueous ammonia solution of ammonium tetramolybdate ((NH4)2Mo4O 13 ) with a concentration of 15 wt%. After stirring evenly, it was dried at 80 °C for 24 hours to obtain precursor (II).

[0065] 400 g of the obtained precursor (II), 100 g of Al2O3, 5 g of graphite, and 10 g of deionized water were mixed evenly. Through a tablet press, the tablet pressure was set to 3 kN, and a circular tablet-shaped catalyst with a diameter of 5 mm and a tablet thickness of 4 mm was formed by pressing. Finally, it was calcined at 525 °C for 36 hours to obtain the catalyst for acrolein synthesis.

[0066]

Example 3

[0067] 55.0 g of bismuth nitrate pentahydrate, 49.5 g of cobalt nitrate hexahydrate, 57.8 g of iron nitrate nonahydrate, and 44.4 g of nickel nitrate hexahydrate were dissolved in 100 g of water. Then, 1000 g of an aqueous solution of ammonium heptamolybdate ((NH4)6Mo7O 24 ·4H2O) with a concentration of 20 wt% was added. After stirring for 10 min, it was spray-dried. The obtained powder was calcined in a muffle furnace at 400 °C for 4 hours to obtain 225 g of precursor (I).

[0068] Then, 225 g of precursor (I) was added to 96 g of an aqueous ammonia solution of ammonium tetramolybdate ((NH4)2Mo4O 13 ) with a concentration of 15 wt%. After stirring evenly, it was dried at 80 °C for 24 hours to obtain precursor (II).

[0069] 400 g of the obtained precursor (II), 100 g of Al2O3, 5 g of graphite, and 10 g of deionized water were mixed evenly. Through a tablet press, the tablet pressure was set to 3 kN, and a circular tablet-shaped catalyst with a diameter of 5 mm and a tablet thickness of 4 mm was formed by pressing. Finally, it was calcined at 525 °C for 36 hours to obtain the catalyst for acrolein synthesis.

[0070]

Example 4

[0071] 72.3 g of bismuth nitrate pentahydrate, 49.5 g of cobalt nitrate hexahydrate, 57.8 g of iron nitrate nonahydrate, and 44.4 g of nickel nitrate hexahydrate were dissolved in 100 g of water. Then, 1000 g of an aqueous solution of ammonium heptamolybdate tetrahydrate ((NH4)6Mo7O 24 ·4H2O) with a concentration of 20 wt% was added. After stirring for 10 min, it was spray-dried. The obtained powder was calcined in a muffle furnace at 320 °C for 4 hours to obtain 225 g of precursor (I).

[0072] Then, 225 g of precursor (I) was added to 96 g of an aqueous ammonia solution of ammonium tetramolybdate dihydrate ((NH4)2Mo4O 13An aqueous ammonia solution of (NH4)2Mo4O·2H2O was added, and after stirring evenly, it was dried at 80 °C for 24 hours to obtain the precursor (II).

[0073] 400 g of the obtained precursor (II), 100 g of Al2O3, 5 g of graphite, and 10 g of deionized water were mixed evenly. The tableting pressure was set at 3 kN by a tableting machine, and a circular tablet-shaped catalyst with a diameter of 5 mm and a thickness of 4 mm was formed by tableting. Finally, it was calcined at 480 °C for 36 hours to obtain the catalyst for acrolein synthesis.

[0074]

Example 5

[0075] 55.0 g of bismuth nitrate pentahydrate, 65.9 g of cobalt nitrate hexahydrate, 57.8 g of iron nitrate nonahydrate, and 44.4 g of nickel nitrate hexahydrate were dissolved in 100 g of water. Then, 1000 g of an aqueous solution of 20 wt% ammonium heptamolybdate tetrahydrate ((NH4)6Mo7O·4H2O) was added. After stirring for 10 min, it was spray-dried. The obtained powder was calcined in a muffle furnace at 450 °C for 4 hours to obtain 225 g of the precursor (I). 24 ·4H2O) aqueous solution 1000g, stir for 10min, then spray dry, and the obtained powder was calcined in a muffle furnace at 450 °C for 4 hours to obtain 225g of precursor (I).

[0076] Then, 225 g of the precursor (I) was added to 96 g of an aqueous ammonia solution of 15 wt% ammonium dimolybdate tetrahydrate ((NH4)2Mo4O·2H2O). After stirring evenly, it was dried at 80 °C for 24 hours to obtain the precursor (II). 13 ·2H2O) aqueous ammonia solution, stir evenly and dry at 80 °C for 24 hours to obtain precursor (II).

[0077] 400 g of the obtained precursor (II), 100 g of Al2O3, 5 g of graphite, and 10 g of deionized water were mixed evenly. The tableting pressure was set at 3 kN by a tableting machine, and a circular tablet-shaped catalyst with a diameter of 5 mm and a thickness of 4 mm was formed by tableting. Finally, it was calcined at 580 °C for 72 hours to obtain the catalyst for acrolein synthesis.

[0078]

Comparative Example 1

[0079] 55.0 g of bismuth nitrate, 49.5 g of cobalt nitrate, 57.8 g of iron nitrate, and 64.8 g of zirconium nitrate were dissolved in 100 g of water. Then, 1000 g of an aqueous solution of 20 wt% ammonium heptamolybdate ((NH4)6Mo7O·4H2O) and 54 g of an aqueous ammonia solution of 25 wt% ammonium dimolybdate tetrahydrate ((NH4)2Mo4O·2H2O) were added. After stirring for 10 min, it was spray-dried. The obtained powder was calcined in a muffle furnace at 400 °C for 8 hours to obtain the active component precursor. 24 ·4H2O) aqueous solution 1000g, 54g of 25wt% aqueous ammonia solution of ammonium dimolybdate ((NH4)2Mo4O·2H2O), stir for 10min, then spray dry, and the obtained powder was calcined in a muffle furnace at 400 °C for 8 hours to obtain the active component precursor. 13 ·2H2O) aqueous ammonia solution, stir for 10 min, then spray dry, and the obtained powder was calcined in a muffle furnace at 400 °C for 8 hours to obtain the active component precursor.

[0080] 400 g of the active component precursor, 100 g of Al2O3, 5 g of graphite, and 10 g of deionized water were mixed evenly. Through a tablet press, the tableting pressure was set at 3 kN, and a circular tablet-shaped catalyst with a diameter of 5 mm and a tablet thickness of 4 mm was obtained by tableting. Finally, it was calcined at 505 °C for 24 hours to obtain the catalyst for acrolein synthesis.

[0081]

Comparative Example 2

[0082] The process of Example 1 was repeated, with the difference that: the calcination conditions of the formed catalyst were different: it was calcined at 505 °C for 2 hours, and the obtained MoO3 was not rod-shaped but was loaded on the microspheres in a lamellar shape.

[0083]

Catalyst Evaluation

[0084] The reactant propylene was introduced into a fixed-bed reactor filled with the catalyst to be tested. The reaction product was absorbed with dilute acid at 0 °C and then analyzed by gas chromatography. The carbon balance was calculated during the analysis process, and the data when the carbon balance was between 95% and 105% were selected as valid data. Among them, the reaction conditions were:

[0085] Reactor: Fixed-bed reactor, inner diameter 25.4 mm, length 750 mm;

[0086] Catalyst filling amount: 150 g;

[0087] Reaction temperature: 350 °C;

[0088] Reaction time: 100 hours;

[0089] Volume ratio of raw materials: propylene: air: steam = 1: 1.6: 3.2;

[0090] Propylene volume space velocity: 100 h -1 .

[0091] The evaluation results are shown in Table 1.

[0092] Table 1: Catalyst evaluation results

[0093]

[0094] Among them, the single-pass yield of acrolein refers to the single-pass yield of acrolein.

[0095] The present invention has been described in detail above in combination with specific embodiments and exemplary examples, but these descriptions should not be construed as limiting the present invention. Those skilled in the art understand that without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications, or improvements can be made to the technical solutions of the present invention and their implementation manners, and these all fall within the scope of the present invention. The protection scope of the present invention is subject to the appended claims.

Claims

1. A Mo-Bi-based catalyst, which comprises an active component, and the active component comprises spherical particles and molybdenum oxide nanorods attached to the surface of the spherical particles, wherein, The spherical particles contain molybdenum and / or its oxides, bismuth and / or its oxides.

2. The Mo-Bi-based catalyst according to claim 1, wherein in the spherical particles, the molar ratio of molybdenum element to bismuth element is 12:(0.05 - 5); and / or, the molybdenum oxide nanorods are MoO3 nanorods.

3. The Mo-Bi based catalyst according to claim 1, characterized in that, The general formula of the spherical particles is Mo 12 Bi g Fe f Co m M y O x , where M is at least one of Ni, Mn, Ce, Zr, and Nb, g = 0.05 - 5, f = 0.05 - 5, m = 0.05 - 5, y = 0.05 - 10, and x is a value determined by the total valence of the elements other than oxygen in the general formula; Preferably, the average diameter of the spherical particles is 5 - 100 μm, preferably 20 - 60 μm.

4. The Mo-Bi based catalyst according to claim 1, characterized in that: The average length of the MoO3 nanorods is 50 - 500 nm, and / or, the average diameter of the MoO3 nanorods is 5 - 50 nm, and / or, the aspect ratio of the MoO3 nanorods is 4 - 20.

5. The Mo-Bi based catalyst according to any one of claims 1 to 4, characterized in that: The catalyst further includes a carrier for loading the active components; preferably, the carrier is selected from one or more of SiO2, Al2O3, CeO2, and TiO2.

6. The Mo-Bi-based catalyst according to claim 5, wherein: Based on 100 wt% of the catalyst, it includes 20 - 90 wt% of the active components and 10 - 80 wt% of the carrier; preferably, it includes 20 - 80 wt% of the active components and 20 - 80 wt% of the carrier.

7. A method for preparing a Mo-Bi-based catalyst, preferably for preparing the catalyst according to any one of claims 1 - 6, the preparation method comprising: (1) Spray-drying an aqueous dispersion containing raw material compounds to obtain a powder, and then pre-calcining the powder to obtain the spherical particles; wherein, the raw material compounds include a molybdenum-containing compound, a bismuth-containing compound, an optional iron-containing compound, an optional cobalt-containing compound, and an optional M-element-containing compound; (2) Immersing the spherical particles in an aqueous molybdate solution and drying to obtain an active component precursor; (3) Mixing the active component precursor with a carrier raw material, shaping, and calcining to obtain the catalyst for acrolein synthesis.

8. The preparation method according to claim 7, wherein: in step (1), the molybdenum-containing compound, bismuth-containing compound, iron-containing compound, cobalt-containing compound, and M-element-containing compound are respectively selected from the corresponding oxygen-containing salts of their metal elements; preferably, the molar ratio of Mo / Bi / Fe / Co / M in the molybdenum-containing compound, bismuth-containing compound, iron-containing compound, cobalt-containing compound, and M-element-containing compound is 12:(0.5 - 5.0):(0.5 - 5.0):(0.5 - 5.0):(0.05 - 10); and / or, in step (1), the conditions for the pre-calcining include: the temperature is 260 - 500 °C, and the time is 0.5 - 8 h; preferably, the temperature is 320 - 450 °C, and the time is 1 - 4 h.

9. The preparation method according to claim 7, characterized in that: The total concentration of the raw material compounds in the aqueous dispersion in step (1) is 5 - 70 wt%, preferably 20 - 50 wt%; Preferably, the molybdenum-containing compound is selected from at least one of ammonium heptamolybdate and / or its hydrate, ammonium tetramolybdate and / or its basic hydrate, preferably from an aqueous solution of basic ammonium tetramolybdate and / or an aqueous solution of ammonium heptamolybdate; Preferably, the bismuth-containing compound, iron-containing compound, cobalt-containing compound, and M-element-containing compound are each selected from at least one of the nitrates corresponding to their metal elements and / or their hydrates.

10. The preparation method according to claim 7, wherein: The concentration of the molybdate aqueous solution in step (2) is 1-40 wt%, more preferably 5-35 wt%; and / or, The molybdate aqueous solution in step (2) is selected from at least one of ammonium tetramolybdate and / or its basic hydrate, ammonium heptamolybdate and / or its aqueous solution; and / or, The molar ratio of Mo in the dispersion for preparing the raw material compound to Mo in the molybdate aqueous solution is 5-50.

11. The preparation method according to any one of claims 7 to 10, wherein: In step (3), the calcination temperature is 200-1000 °C, preferably 300-650 °C; and / or, the calcination time is 0.5-100 hours, preferably 24-72 h; and / or, In step (3), the carrier raw material is selected from one or more of SiO2, Al2O3, CeO2, TiO2 and their precursors; preferably, based on 100 parts by total weight of the active component and the carrier raw material, the amount of the active component is 20-90 parts, and the amount of the carrier raw material is 10-80 parts.

12. Use of the Mo-Bi based catalyst according to any one of claims 1 to 6 or the Mo-Bi based catalyst prepared by the preparation method according to any one of claims 7 to 11 in the synthesis of acrolein; preferably, the use includes contacting the catalyst with propylene at a reaction temperature of 330 to 380 °C and a space velocity of 80 to 130 h -1 -1.

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