An acrylonitrile catalyst prepared by ammoxidation of propylene, its preparation method and application

Abstract

The present invention discloses a catalyst for the ammoxidation of propylene to acrylonitrile, a preparation method thereof, and an application thereof. The active components of the catalyst include molybdenum, bismuth, and rare earth elements, and the carrier includes silica. After heat treatment, the change in the specific surface area of the catalyst conforms to X = (S T1 - S T2 ) / (T2 - T1), where X is less than or equal to 0.18, S T1 is the specific surface area of the catalyst after heat treatment at temperature T1 and in a water-containing atmosphere, S T2 is the specific surface area of the catalyst after heat treatment at temperature T2 and in a water-containing atmosphere, and T2 is greater than T1 and less than or equal to 750 °C. This catalyst exhibits better thermal stability in the application of the ammoxidation of propylene to acrylonitrile.

Description

Technical Field

[0001] The present invention relates to an ammonia oxidation catalyst, and particularly to a catalyst for the ammoxidation of propylene to acrylonitrile, a preparation method thereof, and an application in the reaction of the 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 using propylene as a raw material and by the fluidized bed ammoxidation method.

[0003] The technology for the ammoxidation of propylene to acrylonitrile has been successfully industrialized in acrylonitrile plants worldwide. However, as one of the core technologies of this process, the catalyst for the 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 Mo-Bi 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 ammonia oxidation catalyst prepared by the spray drying method 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 the 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 constantly striving 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 of propylene uses an active component including Mo-Bi and a carrier including silica, when the specific surface area 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, the carrier precursor is first mixed with the rare earth element precursor under specific conditions, and then mixed with other active components, so that the above catalyst can be prepared. The possible reason is that rare earth is more likely to enter the carrier skeleton and form a more stable structure, thereby improving the structural stability of the carrier, and on this basis, the present invention is completed.

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

[0008] In a first aspect of the present invention, there is provided a catalyst for the ammoxidation of propylene to acrylonitrile. The active components of the catalyst include molybdenum, bismuth, and rare earth elements, and the carrier includes silica. The change in specific surface area of the catalyst after heat treatment conforms to formula (I):

[0009] X = (S T1 - S T2 ) / (T2 - T1) (I),

[0010] wherein X is less than or equal to 0.18, S T1 is the specific surface area of the catalyst after heat treatment at temperature T1 and in a water-containing atmosphere, S T2 is the specific surface area of the catalyst after heat treatment at temperature T2 and in a water-containing atmosphere, and T2 is greater than T1 and less than or equal to 750 °C.

[0011] In the catalyst of the present invention, the value of X is less than or equal to 0.18, preferably less than or equal to 0.16. The value of X can be, but is not limited to: 0.18, 0.16, 0.15, 0.12, 0.10, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02, 0.01, etc.

[0012] In the catalyst of the present invention, the temperature T1 is 400 - 600 °C, preferably 450 - 550 °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 further contains at least one of nitrogen or an inert gas.

[0015] In the catalyst of the present invention, the rare earth element is selected from at least one of La, Ce, Pr, Nd, and Sm.

[0016] In the catalyst of the present invention, the active components include molybdenum, bismuth, and rare earth elements. Based on the weight of the catalyst, the molybdenum is in the form of MoO 3The weight content calculated as Bi is 15% - 55%, preferably 20% - 45%. The bismuth is in the form of Bi 2 O 3 The weight content calculated as such is 0.5% - 3.5%, preferably 1.0% - 3.5%. The weight content of the rare earth elements in the form of rare earth element oxides is 1.5% - 8.5%, preferably 2.5% - 5.0%.

[0017] 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.

[0018] In the catalyst of the present invention, the active components may further include Fe, alkali metal elements, alkaline earth metal elements, and metal element A. The said alkali metal elements are selected from at least one of Li, Na, K, Rb, and Cs. The said alkaline earth metal elements are selected from at least one of Be, Mg, Ca, Sr, and Ba. The said 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.

[0019] In the catalyst of the present invention, based on the weight of the catalyst, the weight content of the molybdenum calculated as MoO 3 is 15% - 55%, preferably 20% - 45%. The weight content of the bismuth calculated as Bi 2 O 3 is 0.5% - 3.5%, preferably 1.0% - 3.5%. The weight content of the Fe element calculated as Fe 2 O 3 is 1% - 12%, preferably 1.5% - 11%. The weight content of the alkali metal elements calculated as oxides is 0.01% - 0.60%, preferably 0.05% - 0.55%. The weight content of the alkaline earth metals calculated as oxides is 0.01% - 4.0%, preferably 0.5% - 3.5%. The weight content of the metal element A calculated as oxides is 0.01% - 15%, preferably 0.05% - 14%.

[0020] In the catalyst of the present invention, preferably, 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 11.0. 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., and 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 element + alkali metal element + alkaline earth metal element) / Mo is 0.05 to 0.4, preferably 0.10 to 0.35. Among them, the atomic ratio of (rare earth element + alkali metal element + alkaline earth metal element) / 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 to 1.0, preferably 0.02 to 0.9.

[0021] In the catalyst of the present invention, the carrier may further contain other components, and the other components may be at least one of molecular sieve, zirconia, titanium oxide, magnesium oxide, etc. Based on the weight of the carrier, the content of SiO 2 is 20% to 100%, preferably 30% to 100%, and the content of other components is less than 20%, preferably less than 15%.

[0022] 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%.

[0023] In the catalyst of the present invention, the molar ratio of the rare earth element in terms of rare earth oxide to the carrier in terms of carrier component oxide is 0.01 to 0.12.

[0024] In the present invention, the catalyst is in granular form, and its average particle size is 30 to 70 μm, preferably 40 to 60 μm.

[0025] The second aspect of the present invention provides a preparation method of the above catalyst, comprising the following steps:

[0026] (1) Mix the carrier precursor and the rare earth element precursor to obtain slurry I;

[0027] (2) Mix the slurry I with the active component precursor including molybdenum and bismuth to obtain slurry II;

[0028] (3) Spray-dry and heat-treat the slurry II to obtain the catalyst.

[0029] In the method of the present invention, the carrier precursor described in step (1) includes silica sol. In the silica sol, the solid content is 20 wt% to 50 wt% in terms of silicon dioxide, and the average particle size is 10 to 35 nm.

[0030] In the method of the present invention, the rare earth element described in step (1) is selected from at least one of La, Ce, Pr, Nd, and Sm. The rare earth element precursor is selected from at least one of nitrates and carbonates.

[0031] In the method of the present invention, in step (1), the preparation of slurry I can be carried out in the presence of a solvent. For example, any solvent convenient for mixing raw materials (such as various precursors) in the field of preparing ammonia oxidation catalysts can be cited. More specifically, for example, alcohols and water can be cited, especially C1-C6 monohydric alcohols (such as ethanol) and water, preferably water. These solvents can be used alone or in combination of multiple solvents in any proportion. Generally, the solid content of the slurry I can be 20 wt% to 50 wt%, but the present invention is not limited thereto.

[0032] In the method of the present invention, in step (1), the molar ratio of the rare earth element precursor in terms of rare earth oxide to the carrier precursor in terms of carrier component oxide is 0.01 to 0.08, preferably 0.01 to 0.06.

[0033] In the method of the present invention, in the mixing process described in step (1), the mixing temperature is not higher than 50 °C, preferably not higher than 45 °C, more preferably 25 to 45 °C, and the mixing time is 10 to 60 min, preferably 10 to 30 min.

[0034] In the method of the present invention, in the active component precursor including molybdenum and bismuth described in step (2), the atomic ratio of Bi / Mo is 0.008 to 0.25, preferably 0.01 to 0.20.

[0035] In the method of the present invention, in the active component precursor including molybdenum and bismuth described in step (2), it further includes Fe, rare earth elements, alkali metal elements, alkaline earth metal elements, and metal element A. The alkali metal element is selected from at least one of Li, Na, K, Rb, and Cs. The alkaline earth metal element is 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, 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 0.4, preferably 0.10 to 0.35; the atomic ratio of metal element A / Mo is 0.01 to 1.0, preferably 0.02 to 0.9.

[0036] In the method of the present invention, in step (2), there is no particular limitation on the Mo element precursor, which may 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 oxoacid salts (including hydrates of these compounds) of Mo can be cited. Among them, water-soluble inorganic acid salts, water-soluble organic acid salts, and ammonium oxoacid salts of Mo are preferred, and ammonium oxoacid salts of Mo are more preferred. For example, (NH 4 ) 6 Mo 7 O 24 or its hydrate. There is no particular limitation on the Bi element precursor, the alkali metal element precursor, the alkaline earth metal element precursor, and the metal A element precursor, which may be oxides of the corresponding elements or any substance that can generate this oxide 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.

[0037] In the method of the present invention, in step (2), the preparation of slurry II can be carried out in the presence of a solvent. For example, any solvent convenient for mixing raw materials (such as various precursors) in the preparation of an ammoxidation catalyst in the art can be cited. More specifically, for example, alcohols and water can be cited, especially C1-C6 monohydric alcohols (such as ethanol) and water, and water is preferred. These solvents can be used alone or in combination of multiple kinds in any proportion. In addition, there is no particular limitation on the amount of the liquid in the present invention, as long as it can dissolve all the element precursors (including the Mo element precursor, the Bi element precursor, etc.) and is easy to stir the slurry. Those skilled in the art can make a conventional selection. Generally, the solid content of the slurry II can be 20wt% - 50wt%, but the present invention is not limited thereto. Preferably, the feeding order of step (2) is as follows: first, the molybdenum-containing precursor is mixed with slurry I, and then mixed with other precursors to obtain slurry II.

[0038] In the method of the present invention, the conditions of spray drying in step (3) 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 material particles is 20 - 200 μm, preferably 40 - 180 μm.

[0039] In the method of the present invention, the heat treatment in step (3) 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 feeding amount of the mixed gas per unit time relative to the mass of the catalyst is 50-500 L / kg·h. The mixed gas containing water and oxygen further contains at least one of nitrogen or inert gas.

[0040] The third aspect of the present invention provides a method for preparing acrylonitrile by ammoxidation of propylene, comprising: a step of subjecting propylene to ammoxidation reaction to produce acrylonitrile in the presence of the catalyst prepared by using the above catalyst or the above preparation method.

[0041] In the method of the present invention, the reaction conditions for preparing acrylonitrile by ammoxidation of propylene include: the molar ratio of propylene / ammonia / air in terms of O 2 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 terms of gauge pressure, and the weight hourly space velocity is 0.04-0.10 h -1 .

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] 1. The catalyst of the present invention has good stability and can exhibit stable catalytic activity during long-term stable operation.

[0044] 2. When the catalyst of the present invention is used in the reaction for preparing acrylonitrile by ammoxidation of propylene, with the extension of the reaction time, the decrease amplitude of the acrylonitrile yield is significantly reduced, and a high single-pass yield of acrylonitrile can still be maintained after long-term operation. Description of the Drawings

[0045] Figure 1 It is a graph showing the change trend of the specific surface area of the catalysts obtained in Example 1 and Comparative Example 1 with the heat treatment temperature. Detailed Description of the Invention

[0046] The following is a detailed description of the specific embodiments of the present invention. However, 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.

[0047] In the present invention, the average particle size is measured by using a Malvern MS2000 laser particle size analyzer. Before the sample test, the circulating water of the device needs to be turned on. Before the sample determination, the refractive index of the catalyst needs to be selected. Taking SiO 2The refractive index of 1.45 is used as the refractive index of the measured sample. Before measuring the sample, the background needs to be measured. After the measurement, the sample is added until the light shielding degree reaches 10%, and the average value is selected after three measurements.

[0048] 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 Na 2 O, the oxide of Ni refers to NiO, and the oxide of Fe refers to Fe 2 O 3 .

[0049] In the present invention, the specific surface area of the catalyst is measured by the N 2 adsorption and desorption specific surface area of the sample using Tristar2000 of Micromeritics Instrument Corporation, USA. The sample is first degassed under vacuum at 250 °C for 2 h, and then the N 2 adsorption and desorption curve of the sample is measured at the liquid nitrogen temperature (-196 °C). The specific surface area is obtained according to the BET equation.

[0050] 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.

[0051] A fresh catalyst is used in the ammoxidation of propylene to acrylonitrile reaction, and the propylene conversion rate, acrylonitrile selectivity, and acrylonitrile single-pass yield are calculated as the evaluation indexes of the catalyst performance. Among them, the definitions of the propylene conversion rate, acrylonitrile selectivity, and acrylonitrile single-pass yield are as follows:

[0052] Propylene conversion rate (%) = moles of reacted propylene / moles of fed propylene × 100%;

[0053] Acrylonitrile selectivity (%) = moles of formed acrylonitrile / moles of reacted propylene × 100%;

[0054] Acrylonitrile single-pass yield (%) = moles of formed acrylonitrile / moles of fed propylene × 100%.

[0055]

Example 1

[0056] 78.1 g of Pr(NO 3 ) 3 ·6H 2 O is dissolved in water. At 30 °C, 2750 g of silica sol with a weight concentration of 40% (average particle size of 25 nm) is added. After stirring for 30 min, slurry I is formed. The solid content of slurry I is 36 wt%. 3.69 g of KOH and 175.9 g of Bi(NO 3 ) 3 ·5H 2O, 532.7 g of Ni(NO 3 ) 2 ·6H 2 O, 808.2 g of Fe(NO 3 ) 3 ·9H 2 O, 139.5 g of Mg(NO 3 ) 2 ·6H 2 O was added to water and dissolved to obtain Solution I. 836.6 g of (NH 4 ) 6 Mo 7 O 24 ·4H 2 O was dissolved in water, added to Slurry I, stirred for 10 min, and slowly added to Solution I. After stirring, Slurry II was formed. The solid content of Slurry II was 43 wt%. 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 a mixed gas atmosphere of N 2 with a water volume content of 4% and an oxygen volume content of 25%, the gas flow rate per unit time of the mixed gas relative to the catalyst mass was 200 L / kg·h, and heat treatment was carried out at 550 °C (T1) and 700 °C (T2) for 1 h each to obtain the required catalyst sample.

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

[0058] 50% K 0.15 Fe 5.46 Ni 5.0 Mg 1.5 Pr 0.5 Bi 1.0 Mo 13 O x +50% SiO 2 , the specific surface area of the catalyst was measured, where S T1 was 43.5 m 2 / g, S T2 was 26.5 m 2 / g, X = (43.5 - 26.5) / (700 - 550) = 0.11.

[0059] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the catalyst heat-treated at T2 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; Raw material ratio (mol): C 3 ＝ / NH 3 / Air = 1 / 1.25 / 9.6. After running for 500 hours, the reaction results are as follows: the conversion rate of propylene is 99.5%, and the selectivity of acrylonitrile is 85.3%.

[0060]

Example 2

[0061] Dissolve 133.5 g of Nd(NO 3 ) 3 ·6H 2 O in water. At 30 °C, add 3300 g of silica sol with a weight concentration of 40% (average particle size of 25 nm), and stir for 30 min to form Slurry I. The solid content of Slurry I is 42 wt%. Dissolve 3.12 g of KOH, 74.6 g of Bi(NO 3 ) 3 ·5H 2 O, 447.3 g of Co(NO 3 ) 2 ·6H 2 O, 313.6 g of Fe(NO 3 ) 3 ·9H 2 O, 108.9 g of Mn(NO 3 ) 2 、118.2 g of Mg(NO 3 ) 2 ·6H 2 O, 8.29 g of (NH4) 6 H 5 [H 2 (WO 4 ) 6 into water to dissolve, and obtain Solution I. Dissolve 709 g of (NH 4 ) 6 Mo 7 O 24 ·4H 2 O in water, add it to Slurry I, stir for 10 min, and slowly add Solution I. After stirring, form Slurry II. The solid content of Slurry II is 47 wt%. 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 a mixed gas atmosphere of N 2 gas with a water volume content of 3% and an oxygen volume content of 30%, the unit time gas flow rate of the mixed gas relative to the catalyst mass ratio is 200 L / kg·h, and heat-treat at 550 °C (T1) and 650 °C (T2) for 0.5 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] 40% W 0.1 K 0.15 Fe 2.5 Co 5.0 Mn 1.0 Mg 1.5 Nd 1.0 Bi 0.5 Mo 13 O x +60% SiO 2 , the specific surface area of the catalyst was measured, where S T1 was 42.5 m 2 / g, S T2 was 33.5 m 2 / g, X = (42.5 - 33.5) / (650 - 550) = 0.09.

[0064] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the catalyst heat-treated at temperature T2 were 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 ; the raw material ratio (molar): C 3 ＝ / NH 3 / air = 1 / 1.25 / 9.6. After running for 500 hours, the reaction results were as follows: the propylene conversion was 99.1%, and the acrylonitrile selectivity was 85.8%.

[0065]

Example 3

[0066] Dissolve 140.3 g of La(NO 3 ) 3 ·6H 2 O in water. At 30 °C, add 2750 g of silica sol with a weight concentration of 40% (average particle size of 25 nm). After stirring for 30 min, a slurry I was formed, and the solid content of slurry I was 41 wt%. Dissolve 85.7 g of Bi(NO 3 ) 3 ·5H 2 O, 514.1 g of Co(NO 3 ) 2 ·6H 2 O, 787.3 g of Fe(NO 3 ) 3 ·9H 2 O, 125.1 g of Ca(NO 3 )2 ·4H 2 O, 3.57 g of CrO 3 , 4 g of H 3 PO 4 , 7.82 g of RbNO 3 are added to water and dissolved to obtain Solution I. 814.9 g of (NH 4 ) 6 Mo 7 O 24 ·4H 2 O is dissolved in water, added to Slurry I, stirred for 10 min, and slowly added with Solution I. After stirring, Slurry II is formed. The solid content of Slurry II is 49 wt%. The prepared slurry is 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 are prepared, and then in a mixed gas atmosphere of N 2 with a water volume content of 3% and an oxygen volume content of 20%, the gas flow rate per unit time of the mixed gas relative to the catalyst mass is 200 L / kg·h, and heat treatment is carried out at 550 °C (T1) and 650 °C (T2) for 2 h respectively to obtain the required catalyst sample.

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

[0068] 50% P 0.1 Rb 0.15 Fe 5.46 Co 5.0 Cr 0.1 Ca 1.5 La 1.0 Bi 0.5 Mo 13 O x +50% SiO 2 , the specific surface area of the catalyst is measured, where S T1 is 49.5 m 2 / g, S T2 is 36.5 m 2 / g, X = (49.5 - 36.5) / (650 - 550) = 0.13.

[0069] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the catalyst heat-treated at T2 temperature 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): C 3 ＝ / NH 3 / air = 1 / 1.25 / 9.6. After running for 500 hours, the reaction results are as follows: the conversion rate of propylene is 98.9%, and the selectivity of acrylonitrile is 86.2%.

[0070]

Example 4

[0071] Dissolve 61.5 g of Sm(NO 3 ) 3 ·6H 2 O in water. At 30 °C, add 2750 g of silica sol with a weight concentration of 40% (average particle size of 15 nm), and stir for 30 min to form slurry I. The solid content of slurry I is 43 wt%. Dissolve 85.6 g of Bi(NO 3 ) 3 ·5H 2 O, 518.4 g of Ni(NO 3 ) 2 ·6H 2 O, 786.5 g of Fe(NO 3 ) 3 ·9H 2 O, 3.57 g of CrO 3 , 7.81 g of RbNO 3 , 5.96 g of AgNO 3 into water to dissolve, and obtain solution I. Dissolve 814.1 g of (NH 4 ) 6 Mo 7 O 24 ·4H 2 O in water, add it to slurry I, stir for 10 min, and slowly add solution I. After stirring, form slurry II. The solid content of slurry II is 48 wt%. 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 a mixed gas atmosphere of N 2 with a water volume content of 2% and an oxygen volume content of 25%, the ratio of the gas flow rate per unit time to the catalyst mass is 300 L / kg·h, and heat-treat at 550 °C (T1) and 650 °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% Ag 0.1 Rb 0.15 Fe 5.46 Ni 5.0 Cr 0.1 Sm 1.0 Bi0.5 Mo 13 O x +50% SiO 2 The specific surface area of the catalyst was measured, where S T1 was 51.5 m 2 / g, S T2 was 39.5 m 2 / g, X = (51.5 - 39.5) / (650 - 550) = 0.12.

[0074] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the catalyst heat-treated at temperature T2 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 ; the raw material ratio (molar): C 3 ＝ / NH 3 / air = 1 / 1.25 / 9.6. After running for 500 hours, the reaction results were as follows: the propylene conversion was 99.1%, and the acrylonitrile selectivity was 85.1%.

[0075]

Example 5

[0076] 20.2 g of Sm(NO 3 ) 3 ·6H 2 O was dissolved in water. At 30 °C, 2750 g of silica sol with a weight concentration of 40% (average particle size of 15 nm) was added. After stirring for 30 min, slurry I was formed, and the solid content of slurry I was 45 wt%. 93.5 g of Bi(NO 3 ) 3 ·5H 2 O, 566.2 g of Ni(NO 3 ) 2 ·6H 2 O, 858.9 g of Fe(NO 3 ) 3 ·9H 2 O, 3.89 g of CrO 3 , 8.53 g of RbNO 3 , 3.26 g of AgNO 3 were added to water and dissolved to obtain solution I. 889.1 g of (NH 4 ) 6 Mo 7 O 24 ·4H 2O is dissolved in water, and slurry I is added. After stirring for 10 min, solution I is slowly added. After stirring, slurry II is formed. The solid content of slurry II is 50 wt%. The prepared slurry is 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 are prepared, and then in a mixed gas atmosphere of N 2 with a volume content of water of 1% and a volume content of oxygen of 25%, the ratio of the gas flow rate per unit time to the catalyst mass is 400 L / kg·h, and heat treatment is carried out at 500 °C (T1) and 650 °C (T2) for 1 h each to obtain the required catalyst sample.

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

[0078] 50% Ag 0.05 Rb 0.15 Fe 5.46 Ni 5.0 Cr 0.1 Sm 0.3 Bi 0.5 Mo 13 O x +50% SiO 2 , the specific surface area of the catalyst is measured, where S T1 is 53.5 m 2 / g, S T2 is 37.3 m 2 / g, X = (53.5 - 37.3) / (650 - 500) = 0.11.

[0079] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the catalyst heat-treated at T2 temperature 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 hour -1 ; the raw material ratio (mole): C 3 ＝ / NH 3 / air = 1 / 1.25 / 9.6. After running for 500 hours, the reaction results are as follows: the propylene conversion rate is 98.9%, and the acrylonitrile selectivity is 83.6%.

[0080]

Example 6

[0081] 31.8 g of Pr(NO 3 ) 3 ·6H 2O is dissolved in water. At 30 °C, 2750 g of silica sol with a weight concentration of 40% (average particle size of 11 nm) is added. After stirring for 30 min, slurry I is formed, and the solid content of slurry I is 42 wt%. 89.6 g of Bi(NO 3 ) 3 ·5H 2 O, 542.5 g of Ni(NO 3 ) 2 ·6H 2 O, 823.1 g of Fe(NO 3 ) 3 ·9H 2 O, 3.73 g of CrO 3 , 5.45 g of RbNO 3 , 4.93 g of Pd(NO 3 ) 2 are added to water and dissolved to obtain solution I. 582 g of (NH 4 ) 6 Mo 7 O 24 ·4H 2 O is dissolved in water, added to slurry I, stirred for 10 min, and then solution I is slowly added. After stirring, slurry II is formed. The solid content of slurry II is 48 wt%. The prepared slurry is subjected to microsphere forming 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 are prepared, and then in a mixed gas atmosphere of N 2 with a water volume content of 4% and an oxygen volume content of 25%, the ratio of the gas flow rate per unit time to the catalyst mass is 500 L / kg·h, and heat treatment is carried out at 500 °C (T1) and 650 °C (T2) for 1 h respectively to obtain the required catalyst sample.

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

[0083] 50% Pd 0.05 Rb 0.10 Fe 5.46 Ni 5.0 Cr 0.1 Pr 0.2 Bi 0.5 Mo 13 O x + 50% SiO 2 , the specific surface area of the catalyst is measured, where S T1 is 58.3 m 2 / g, and S T2 is 31.3 m 2 / g, X = (58.3 - 31.3) / (650 - 500) = 0.18.

[0084] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the catalyst heat-treated at temperature T2 are as follows: On a millimeter fluidized bed reactor, the catalyst particle size is 50 μm, 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 ; the raw material ratio (mol): C 3 ＝ / NH 3 / air = 1 / 1.25 / 9.6. After running for 500 hours, the reaction results are as follows: the propylene conversion rate is 99.2%, and the acrylonitrile selectivity is 81.2%.

[0085]

Comparative Example 1

[0086] Dissolve 836.6 g of (NH 4 ) 6 Mo 7 O 24 ·4H 2 O in water. At 30 °C, add 2750 g of silica sol with a weight concentration of 40% (average particle size of 25 nm). After stirring for 30 min, form slurry I, and the solid content of slurry I is 38 wt%. Dissolve 78.1 g of Pr(NO 3 ) 3 ·6H 2 O, 3.69 g of KOH, 175.9 g of Bi(NO 3 ) 3 ·5H 2 O, 532.7 g of Ni(NO 3 ) 2 ·6H 2 O, 808.2 g of Fe(NO 3 ) 3 ·9H 2 O, 139.5 g of Mg(NO 3 ) 2 ·6H 2 O in water to obtain solution I. Slowly add solution I and stir to form slurry II. The solid content of slurry II is 43 wt%. Shape 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 N with a water volume content of 4% and an oxygen volume content of 25% 2In a mixed gas atmosphere of gas, the ratio of the amount of the mixed gas introduced per unit time to the mass of the catalyst is 200 L / kg·h. Heat treatment is carried out at 550 °C (T1) and 700 °C (T2) for 1 h respectively to obtain the required catalyst sample.

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

[0088] 50% K 0.15 Fe 5.46 Ni 5.0 Mg 1.5 Pr 0.5 Bi 1.0 Mo 13 O x +50% SiO 2 , the specific surface area of the catalyst is measured, where S T1 is 45.8 m 2 / g, S T2 is 16.5 m 2 / g, X = (45.8 - 16.5) / (700 - 550) = 0.20.

[0089] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the catalyst heat-treated at the T2 temperature are as follows: On a millimeter fluidized bed reactor, the catalyst particle size is 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 ; the raw material ratio (molar): C 3 ＝ / NH 3 / air = 1 / 1.25 / 9.6. After running for 500 h, the reaction results are as follows: the propylene conversion rate is 99.9%, and the acrylonitrile selectivity is 79.3%.

[0090]

Comparative Example 2

[0091] Dissolve 709 g of (NH 4 ) 6 Mo 7 O 24 ·4H 2 O in water. At 30 °C, add 3300 g of silica sol with a weight concentration of 40% (average particle size of 25 nm). After stirring for 30 min, form slurry I, and the solid content of slurry I is 44%. Add 133.5 g of Nd(NO 3 ) 3 ·6H 2 O, 3.12 g of KOH, 74.6 g of Bi(NO 3 ) 3 ·5H2 O, 447.3 g of Co(NO 3 ) 2 ·6H 2 O, 313.6 g of Fe(NO 3 ) 3 ·9H 2 O, 108.9 g of Mn(NO 3 ) 2 , 118.2 g of Mg(NO 3 ) 2 ·6H 2 O, 8.29 g of (NH4) 6 H 5 [H 2 (WO 4 ) 6 were added to water and dissolved to obtain Solution I. Solution I was slowly added and stirred to form Slurry II. The solid content of Slurry II was 47 wt%. The prepared slurry was subjected to microsphere forming 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 a mixed gas atmosphere of N 2 with a volume content of water of 3% and a volume content of oxygen of 30%, the gas flow rate per unit time of the mixed gas relative to the catalyst mass was 200 L / kg·h, and heat treatments were carried out at 550 °C (T1) and 650 °C (T2) for 1 h each 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] 40% K 0.15 Fe 5.46 Co 5.0 Mn 1.0 Mg 1.5 Nd 1.0 Bi 0.5 Mo 13 O x +60% SiO 2 , the specific surface area of the catalyst was measured, where S T1 was 43.5 m 2 / g, S T2 was 21.3 m 2 / g, and X = (43.5 - 21.3) / (650 - 550) = 0.22.

[0094] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the catalyst heat-treated at T2 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 (molar): C 3 ＝ / NH 3 / Air = 1 / 1.25 / 9.6. After running for 500 hours, the reaction results are as follows: The propylene conversion rate is 99.1%, and the acrylonitrile selectivity is 80.1%.

[0095]

Comparative Example 3

[0096] Dissolve 1.7 grams of Sm(NO 3 ) 3 ·6H 2 O in water. At 30 °C, add 2750 grams of silica sol with a weight concentration of 40% (average particle size of 15 nm), stir for 30 min to form slurry I, and the solid content of slurry I is 36 wt%. Dissolve 3.95 grams of CrO 3 , 94.8 grams of Bi(NO 3 ) 3 ·5H 2 O, 574 grams of Ni(NO 3 ) 2 ·6H 2 O, 870.7 grams of Fe(NO 3 ) 3 ·9H 2 O, 8.64 grams of RbNO 3 , 6.6 grams of AgNO 3 into water to obtain solution I. Dissolve 901.3 grams of (NH 4 ) 6 Mo 7 O 24 ·4H 2 O in water, add it to slurry I, stir for 10 min, slowly add solution I, and stir to form slurry II. The solid content of slurry II is 43 wt%. 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 a mixed gas atmosphere of N 2 with a water volume content of 2% and an oxygen volume content of 25%, the gas flow rate per unit time of the mixed gas relative to the catalyst mass ratio is 300 L / kg·h, and heat treatment is carried out at 550 °C (T1) and 650 °C (T2) for 1 h respectively to obtain the required catalyst samples.

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

[0098] 50% Ag 0.1 Rb 0.15 Fe 5.46 Ni 5.0 Cr 0.1 Sm 0.01 Bi 0.5 Mo 13 O x + 50% SiO 2 , the specific surface area of the catalyst was measured, where S T1 was 56.5 m 2 / g, S T2 was 26.5 m 2 / g, X = (56.5 - 26.5) / (650 - 550) = 0.30.

[0099] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the catalyst heat-treated at temperature T2 were 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 ; the feed ratio (molar): C 3 ＝ / NH 3 / air = 1 / 1.25 / 9.6. After running for 500 hours, the reaction results were as follows: the propylene conversion was 98.7%, and the acrylonitrile selectivity was 77.3%.

[0100]

Comparative Example 4

[0101] Dissolve 280.3 g of Sm(NO 3 ) 3 ·6H 2 O in water. At 30 °C, add 2750 g of silica sol with a weight concentration of 40% (average particle size of 15 nm), stir for 30 min, and form slurry I. The solid content of slurry I was 45 wt%. Add 2.95 g of CrO 3 , 70.9 g of Bi(NO 3 ) 3 ·5H 2 O, 429.4 g of Ni(NO 3 ) 2 ·6H 2 O, 651.4 g of Fe(NO 3 ) 3 ·9H 2 O, 6.47 g of RbNO 3 , 4.94 g of AgNO 3Dissolve it in water to obtain Solution I. Dissolve 674.3 g of (NH 4 ) 6 Mo 7 O 24 ·4H 2 O in water, add Slurry I, stir for 10 min, slowly add Solution I, and after stirring, form Slurry II. The solid content of Slurry II is 48 wt%. Shape 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 a mixed gas atmosphere of N 2 with a volume content of water of 2% 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 300 L / kg·h, and heat-treat at 550 °C (T1) and 650 °C (T2) for 1 h respectively to obtain the required catalyst samples.

[0102] The composition of the catalyst obtained according to the above steps is represented by the following formula:

[0103] 50% Ag 0.1 Rb 0.15 Fe 5.46 Ni 5.0 Cr 0.1 Sm 5.5 Bi 0.5 Mo 13 O x +50% SiO 2 , the specific surface area of the catalyst is measured, where S T1 is 51.3 m 2 / g, S T2 is 31.5 m 2 / g, X = (51.3 - 31.5) / (650 - 550) = 0.20.

[0104] The reaction conditions for the ammoxidation of propylene to acrylonitrile using the catalyst heat-treated at temperature T2 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): C 3 ＝ / NH 3 / air = 1 / 1.25 / 9.6. After running for 500 h, the reaction results are as follows: the propylene conversion rate is 98.8%, and the acrylonitrile selectivity is 77.8%.

[0105]

Comparative Example 5

[0106] Dissolve 78.1 g of Pr(NO 3 ) 3 ·6H 2 O in water. At 30 °C, add 2,750 g of silica sol with a weight concentration of 40% (average particle size of 25 nm). After stirring for 30 min, form slurry I. The solid content of slurry I is 36 wt%. Dissolve 3.69 g of KOH, 175.9 g of Bi(NO 3 ) 3 ·5H 2 O, 532.7 g of Ni(NO 3 ) 2 ·6H 2 O, 808.2 g of Fe(NO 3 ) 3 ·9H 2 O, 139.5 g of Mg(NO 3 ) 2 ·6H 2 O in water to obtain solution I. Dissolve 836.6 g of (NH 4 ) 6 Mo 7 O 24 ·4H 2 O in water, add it to slurry I, stir for 10 min, and slowly add solution I. After stirring, form slurry II. The solid content of slurry II is 43 wt%. 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. Then, calcine it in an air atmosphere at 700 °C for 1 h to obtain the required catalyst sample.

[0107] The composition of the catalyst obtained according to the above steps is represented by the following formula:

[0108] 50% K 0.15 Fe 5.46 Ni 5.0 Mg 1.5 Pr 0.5 Bi 1.0 Mo 13 O x +50% SiO 2 。

[0109] 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 μm, the reaction temperature is 430 °C; the reaction pressure is 0.084 MPa; the catalyst propylene load (WWH) is 0.085 h -1 ; the raw material ratio (mole): C3 ＝ / NH 3 / air = 1 / 1.25 / 9.6. After running for 500 hours, the reaction results were as follows: the conversion rate of propylene was 97.5%, and the selectivity of acrylonitrile was 79.8%.

[0110] Table 1 Composition and evaluation results of the catalysts obtained in each example and comparative example

[0111]

[0112] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions 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. A catalyst for the ammoxidation of propylene to acrylonitrile, wherein the active components of the catalyst include molybdenum, bismuth and rare earth elements, the carrier includes silica, and the change in specific surface area of the catalyst after heat treatment conforms to formula (I): X = (S T1 - S T2 ) / (T2 - T1) (I), Wherein, The value of X is less than or equal to 0.18, S T1 is the specific surface area of the catalyst after heat treatment at temperature T1 and in a water-containing atmosphere, S T2 is the specific surface area of the catalyst after heat treatment at temperature T2 and in a water-containing atmosphere, and T2 is greater than T1, T2 is less than or equal to 750 °C; the temperature T1 is 400 - 600 °C; the temperature T2 is 500 - 750 °C; the heat treatment time is 0.5 - 4 h; the temperature T2 is at least 50 °C higher than the temperature T1; The rare earth element is selected from at least one of La, Ce, Pr, Nd, and Sm; Based on the weight of the catalyst, the weight content of molybdenum calculated as MoO 3 is 15% - 55%, the weight content of bismuth calculated as Bi 2 O 3 is 0.5% - 3.5%, and the weight content of rare earth elements calculated as oxides of rare earth elements is 1.5% - 8.5%; the atomic ratio of Bi / Mo is 0.008 - 0.25; The preparation method of the catalyst includes the following steps: (1) Mix the carrier precursor and the rare earth element precursor to obtain slurry I; (2) Mix the slurry I with the active component precursor including molybdenum and bismuth to obtain slurry II; (3) Spray-dry and heat-treat the slurry II to obtain the catalyst.

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

3. The catalyst according to claim 1 or 2, characterized in that, 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.

4. The catalyst according to claim 1, characterized in that, Based on the weight of the catalyst, the weight content of molybdenum calculated as MoO 3 is 20% - 45%, the weight content of bismuth calculated as Bi 2 O 3 is 1.0% - 3.5%, and the weight content of the rare earth element calculated as the oxide of the rare earth element is 2.5% - 5.0%.

5. The catalyst according to claim 1, characterized in that, The atomic ratio of Bi / Mo is 0.01-0.

20.

6. The catalyst according to claim 1, characterized in that, The active components further include Fe, 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, and Te.

7. The catalyst according to claim 6, characterized in that, The atomic ratio of Fe / Bi is 1.0-11.

0.

8. The catalyst according to claim 6, characterized in that, Based on the weight of the catalyst, the weight content of the molybdenum calculated as MoO 3 is 15% to 55%, the weight content of the bismuth calculated as Bi 2 O 3 is 0.5% to 3.5%, the weight content of the Fe element calculated as Fe 2 O 3 is 1% to 12%, the weight content of the alkali metal element calculated as the oxide is 0.01% to 0.60%, the weight content of the alkaline earth metal calculated as the oxide is 0.01% to 4.0%, and the weight content of the metal element A calculated as the oxide is 0.01% to 15%.

9. The catalyst according to claim 8, characterized in that, Based on the weight of the catalyst, the weight content of the molybdenum calculated as MoO 3 is 20% - 45%, the weight content of the bismuth calculated as Bi 2 O 3 is 1.0% - 3.5%, the weight content of the Fe element calculated as Fe 2 O 3 is 1.5% - 11%, the weight content of the alkali metal element calculated as the oxide is 0.05% - 0.55%, the weight content of the alkaline earth metal calculated as the oxide is 0.5% - 3.5%, and the weight content of the metal element A calculated as the oxide is 0.05% - 14%.

10. The catalyst according to claim 8, characterized in that, In the catalyst, the atomic ratio of (rare earth element + alkali metal element + alkaline earth metal element) / Mo is 0.05-0.

4.

11. The catalyst according to claim 10, characterized in that, In the catalyst, the atomic ratio of (rare earth element + alkali metal element + alkaline earth metal element) / Mo is 0.10-0.

35.

12. The catalyst according to claim 1, 6 or 8, characterized in that, Based on the weight of the catalyst, the content of the active components in terms of oxides is 20%-80%, and the content of the carrier is 20%-80%.

13. The catalyst according to claim 1, characterized in that, The molar ratio of the rare earth element in terms of rare earth oxide to the carrier in terms of carrier component oxide is 0.01-0.

12.

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

15. The catalyst according to claim 14, characterized in that the catalyst is in granular form, and its average particle size is 40 - 60 μm.

16. A method for preparing the catalyst according to any one of claims 1 - 15, comprising the following steps: (1) Mixing a carrier precursor and a rare earth element precursor to obtain slurry I; (2) Mixing the slurry I with an active component precursor comprising molybdenum and bismuth to obtain slurry II; (3) Spray - drying and heat - treating the slurry II to obtain the catalyst.

17. The preparation method according to claim 16, characterized in that the carrier precursor in step (1) comprises silica sol; in the silica sol, the solid content is 20 wt% - 50 wt% calculated as silicon dioxide, and the average particle size is 10 - 35 nm; and / or, the solid content of the slurry I is 20 wt% - 50 wt%; and / or, the solid content of the slurry II is 20 wt% - 50 wt%.

18. The preparation method according to claim 16, characterized in that during the mixing process in step (1), the mixing temperature is not higher than 50 °C, and the mixing time is 10 - 60 min; and / or, the conditions for spray - drying in step (3) 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 - dried particles is 20 - 200 μm; and / or, the heat - treatment in step (3) is a high - temperature calcination treatment in a water - containing atmosphere.

19. The preparation method according to claim 18, characterized in that during the mixing process in step (1), the mixing temperature is not higher than 45 °C, and the mixing time is 10 - 30 min.

20. The preparation method according to claim 18, characterized in that during the mixing process in step (1), the mixing temperature is 25 - 45 °C.

21. The preparation method according to claim 18, characterized in that the conditions for spray - drying in step (3) include: the drying temperature is 300 - 350 °C, the drying time is 0.2 - 1.0 h, and the average diameter of the spray - dried particles is 40 - 180 μm.

22. The preparation method according to claim 18, characterized in that the conditions for the heat - treatment in step (3) are as follows: the temperature is 500 - 750 °C, the time is 0.2 - 4 h, 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 introduction amount of the mixed gas to the mass of the catalyst is 50 - 500 L / kg·h.

23. A method for the ammoxidation of propylene to acrylonitrile, comprising: the step of subjecting propylene to an ammoxidation reaction to produce acrylonitrile in the presence of the catalyst prepared by using the catalyst according to any one of claims 1 - 15 or the preparation method according to any one of claims 16 - 22.

24. The method according to claim 23, characterized in that The reaction conditions for the ammoxidation of propylene to acrylonitrile include: the molar ratio of propylene / ammonia / air calculated as O 2 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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