A composite catalyst for preparing propenal by catalytic oxidation of propylene and a preparation method thereof

Abstract

The application relates to the technical field of catalysts, and particularly discloses a composite catalyst for preparing propenal through catalytic oxidation of propylene and a preparation method thereof, which comprises active component I and active component II; the use mass ratio of the active component I and the active component II is 1:1-19; the active component I is bismuth tungstate microspheres obtained through a hydrothermal synthesis method, and a general formula is Bi a W1O x ; the active component II is a multimetal oxide obtained through a coprecipitation method, and a general formula is Mo 12 Bi b Co c Ni d Fe e A f B g O y ; the composite catalyst obtained by mixing the bismuth tungstate microspheres obtained through the hydrothermal synthesis method and the multimetal oxide obtained through the coprecipitation method makes the bismuth tungstate microspheres with the microsphere structure serve as the active phase of the reaction and improve the specific surface area and the pore volume of the composite catalyst, and is suitable for the reaction of preparing propenal through catalytic oxidation of propylene under high load.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalysts, and particularly relates to a composite catalyst for preparing propylene aldehyde through propylene catalytic oxidation and a preparation method thereof. BACKGROUND

[0002] The two-step oxidation method of propylene to produce propylene aldehyde to produce acrylic acid is a commonly used method for producing acrylic acid in industry, and acrylic acid can be used to produce high water-absorbing resin, water-based paint, pressure-sensitive adhesive and other products, and has very wide application. Among them, the catalyst used for producing propylene aldehyde through one-step oxidation of propylene is a Mo-Bi metal oxide catalyst, and the Mo=O site is the active center of the reaction, and the addition of Fe, Co, Ni to the catalyst can inhibit the loss of Mo and improve the activity, and the addition of W, Cu, Sb and other elements can further improve the catalytic activity, and the addition of Na, K, Mg, Ca and other alkaline additives can inhibit the non-selective reaction.

[0003] The Mo-Bi catalyst has high activity, high selectivity and good stability, and is therefore commonly used in the industry for preparing propylene aldehyde from propylene oxidation. However, the catalyst obtained by co-precipitation has few pore structures, low specific surface area and low space velocity of propylene, and the utilization rate of metal elements is also low. In the production process of the catalyst, urea, carbonate and other substances are usually added as pore-forming agents, and this pore-forming method is prone to uneven pore distribution, and the residual pore-forming agent can block the pores and even contaminate the catalyst. Therefore, we need to propose a composite catalyst for preparing propylene aldehyde from propylene catalytic oxidation and a preparation method thereof to solve the above problems, so that Bi2WO6 microspheres can be obtained by hydrothermal synthesis, and the composite catalyst can be obtained by mixing the Bi2WO6 microspheres with Mo-Bi metal oxides prepared by co-precipitation. The microspherical structure of Bi2WO6 can not only act as an active phase for the reaction, but also can improve the specific surface area and pore volume of the composite catalyst. SUMMARY

[0004] The application aims to provide a composite catalyst for preparing propylene aldehyde from propylene catalytic oxidation and a preparation method thereof, which can obtain Bi2WO6 microspheres by hydrothermal synthesis, and obtain a composite catalyst by mixing the Bi2WO6 microspheres with Mo-Bi metal oxides prepared by co-precipitation. The microspherical structure of Bi2WO6 can not only act as an active phase for the reaction, but also can improve the specific surface area and pore volume of the composite catalyst, so as to solve the problems proposed in the above background.

[0005] To achieve the above-mentioned purpose, the application adopts the following technical solutions:

[0006] A composite catalyst for preparing propylene aldehyde from propylene catalytic oxidation, comprising active component one and active component two, and the use mass ratio of the active component one and the active component two is 1:1-19.

[0007] The active component one is bismuth tungstate microspheres obtained by hydrothermal synthesis, and the general formula is Bi a W1O x ;

[0008] The active component two is a multi-metal oxide obtained by co-precipitation, and the general formula is Mo 12 Bi b Co c Ni d Fe e A f B g O y ;

[0009] wherein Bi is bismuth, W is tungsten, Mo is molybdenum, Co is cobalt, Ni is nickel, Fe is iron, and O is oxygen; A is at least one selected from lithium, sodium, potassium, rubidium, and cesium; and B is one selected from beryllium, magnesium, calcium, strontium, and barium;

[0010] a, b, c, d, e, f, and g are atomic ratios of respective elements, wherein a = 0.5-2; b = 0.8-1.3; c = 4-6; d = 2-3; e = 0.8-2; and f = 0.05-0.3.

[0011] Preferably, the preparation process of the active component one comprises the following steps:

[0012] A1, dissolving a tungsten source in deionized water to obtain a solution A, and adding a bismuth source to deionized water to obtain a suspension B, and then adding the solution A to the suspension B under heating and constant temperature stirring for 1 h;

[0013] A2, transferring the stirred suspension to a polytetrafluoroethylene-lined stainless steel reaction kettle for hydrothermal synthesis;

[0014] A3, washing, centrifuging, and drying the solid obtained by hydrothermal synthesis, and then heat-treating the solid under a nitrogen atmosphere to obtain the active component one.

[0015] Preferably, in step A1, the tungsten source is sodium tungstate or ammonium tungstate, the bismuth source is bismuth nitrate or bismuth subnitrate, and the heating temperature is 60-98 ℃.

[0016] Preferably, in step A2, the hydrothermal synthesis temperature is 140-200 ℃, and the hydrothermal synthesis time is 20-28 h.

[0017] Preferably, in step A3, the heat-treatment temperature is 600-800 ℃, the heat-treatment time is 1-4 h, the centrifuging condition is centrifuging at a speed of 8000 r / min for 3 min, and the drying condition is drying at 80 ℃ for 12 h.

[0018] Preferably, the preparation process of the active component two is as follows:

[0019] B1, dissolving the Mo source, the A source and the B source in deionized water to obtain a solution C, dissolving the Co source, the Ni source and the Fe source in deionized water to obtain a solution D, dissolving the Bi source in nitric acid to obtain a solution E under heating conditions;

[0020] B2, adding the solution D and the solution E into the solution C in sequence to form a slurry;

[0021] B3, drying the slurry and crushing to obtain the active component two.

[0022] Preferably, in the step B1, the Mo source is ammonium heptamolybdate, the Bi source, the Co source, the Ni source and the Fe source are nitrate, the A source is nitrate or chloride, and the B source is nitrate or hydroxide.

[0023] Preferably, the total mass of the Mo source, the A source, the B source, the Co source, the Ni source, the Fe source and the Bi source is 1:1.5-6 of the total mass of the deionized water.

[0024] Preferably, in the step B3, the drying temperature is 110-180 ℃, and the drying time is 20-30 h.

[0025] Based on the above-described composite catalyst for preparing propylene aldehyde through catalytic oxidation of propylene, the application further provides a preparation method of the composite catalyst for preparing propylene aldehyde through catalytic oxidation of propylene, which comprises the following steps:

[0026] S1, mixing the active component one and the active component two at a mass ratio of 1:1-19 to form a mixture;

[0027] S2, calcining the mixture to obtain a catalyst product, wherein the calcining temperature is 450-600 ℃, and the calcining time is 5-8 h.

[0028] The composite catalyst for preparing propylene aldehyde through catalytic oxidation of propylene and the preparation method thereof have the following advantages compared with the prior art:

[0029] 1. The composite catalyst obtained by mixing the bismuth tungstate microspheres obtained through hydrothermal synthesis and the multi-metal oxides obtained through co-precipitation can make the bismuth tungstate microspheres with microsphere structure serve as the active phase of the reaction and improve the specific surface area and the pore volume of the composite catalyst, and is suitable for the reaction of preparing propylene aldehyde through catalytic oxidation of propylene under high load. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The figure is a flowchart for preparing the composite catalyst of the application;

[0031] Figure 2 The figure is a flowchart for preparing the active component one of the application;

[0032] Figure 3 Preparation flow chart of active component two for the application;

[0033] Figure 4 SEM image of Bi2WO6 microspheres prepared in the comparative example of the application. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. The specific embodiments described here are only used to explain the application, and are not used to limit the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work are within the protection scope of the application.

[0035] The application provides a composite catalyst for preparing propylene aldehyde through catalytic oxidation of propylene, as shown in formula (I). Figures 1-3 The composite catalyst comprises active component one and active component two, and the use mass ratio of the active component one and the active component two is 1:1-19; the active component one is bismuth tungstate microspheres obtained through a hydrothermal synthesis method, and has a general formula of Bi a W1O x The active component two is a multimetal oxide obtained through a coprecipitation method, and has a general formula of Mo 12 Bi b Co c Ni d Fe e A f B g O y ; wherein Bi is bismuth, W is tungsten, Mo is molybdenum, Co is cobalt, Ni is nickel, Fe is iron, and O is oxygen; A is at least one selected from lithium, sodium, potassium, rubidium and cesium elements; B is one selected from beryllium, magnesium, calcium, strontium and barium elements; a, b, c, d, e, f and g are atomic ratios of the elements, wherein a=0.5-2; b=0.8-1.3; c=4-6; d=2-3; e=0.8-2; f=0.05-0.3; by adjusting the ratios, the activity, selectivity and stability of the catalyst can be optimized.

[0036] The preparation flow of the active component one comprises the following steps:

[0037] A1, dissolving a tungsten source in deionized water to obtain a solution A, adding a bismuth source into deionized water to obtain a suspension B, and adding the solution A into the suspension B under heating conditions and constant-temperature stirring for 1 h;

[0038] The tungsten source is sodium tungstate or ammonium tungstate, the bismuth source is bismuth nitrate or bismuth subnitrate, and the heating temperature is 60-98 ℃; the molar ratio of the bismuth source to the tungsten source is 0.5-2:1, such as using 9.46 g of sodium tungstate dihydrate and 24.25 g of bismuth nitrate pentahydrate; the heating temperature is preferably 90 ℃, which ensures uniform mixing of the solution and promotes the reaction of the tungsten source and the bismuth source;

[0039] A2, the stirred suspension is transferred to a polytetrafluoroethylene-lined stainless steel reaction kettle for hydrothermal synthesis; the hydrothermal synthesis temperature is 140-200 ℃, and the hydrothermal synthesis time is 20-28 h, preferably 180 ℃ for 24 h, to form bismuth tungstate microspheres with good crystallinity;

[0040] A3, the solid obtained by hydrothermal synthesis is washed with deionized water, centrifuged, dried, and then heat treated in a nitrogen atmosphere to obtain active component one. Wash with deionized water until neutral, centrifuge (8000 r / min, 3 min) to remove impurities, then dry at 80 ℃ for 12 h, and then heat treat at a temperature of 600-800 ℃ in a nitrogen atmosphere for 1-4 h, preferably at 650 ℃ for 2 h;

[0041] The flowchart for preparing active component two is as follows:

[0042] B1, dissolve the Mo source, A source, and B source in deionized water under heating conditions to obtain solution C, dissolve the Co source, Ni source, and Fe source in deionized water to obtain solution D, and dissolve the Bi source in nitric acid to obtain solution E;

[0043] The Mo source is ammonium heptamolybdate, the Bi source, Co source, Ni source, and Fe source are nitrate salts, the A source is a nitrate salt or a chloride salt, and the B source is a nitrate salt or a hydroxide; the total mass of the Mo source, A source, B source, Co source, Ni source, Fe source, and Bi source to the total mass of deionized water is 1:1.5-6; for example, using 30 g of ammonium heptamolybdate as the Mo source, and other components are: potassium nitrate (KNO3) 0.14 g, magnesium nitrate (Mg(NO3)2·6H2O) 0.36 g, cobalt nitrate (Co(NO3)2·6H2O) 20.61 g, nickel nitrate (Ni(NO3)2·6H2O) 9.06 g, iron nitrate (Fe(NO3)3·9H2O) 7.44 g, and bismuth nitrate (Bi(NO3)3·5H2O) 7.56 g (dissolved in 5 mL of deionized water and 1 mL of nitric acid); the heating temperature is preferably 70 ℃, which ensures that each component is fully dissolved and uniformly mixed;

[0044] B2, add solution D and solution E to solution C in sequence to form a slurry;

[0045] B3, after drying the slurry, crushing to obtain active component two, the drying temperature is 110-180 ℃, the drying time is 20-30 h, preferably 140 ℃, maintaining 24 h, to remove moisture and form a dry precursor, crushing to an appropriate particle size for mixing.

[0046] Based on the above-described composite catalyst for catalytic oxidation of propylene to prepare propylene aldehyde, the application further provides a preparation method of the composite catalyst for catalytic oxidation of propylene to prepare propylene aldehyde, comprising the following steps:

[0047] S1, mixing active component one and active component two in a mass ratio of 1:1-19 to form a mixture, preferably in a range of 1:3-9; grinding or stirring can be used to ensure uniform distribution, and the active component two is mixed with the active component one after drying, and the mixture does not need to be additionally dried before calcination;

[0048] S2, calcining the mixture to obtain a catalyst product, the calcination temperature is 450-600 ℃, and the calcination time is 5 h-8 h. For example, calcining at 500 ℃ for 6 h can form a stable catalyst structure and promote the interaction between the active components, and the process can be carried out in an atmosphere with different oxygen concentrations, which can be selected according to the performance requirements of the catalyst.

[0049] It should be noted that the required equipment is as follows:

[0050] A stainless steel reaction kettle with a polytetrafluoroethylene lining has the characteristics of corrosion resistance, high temperature resistance and high pressure resistance, and is suitable for hydrothermal synthesis reaction; during the hydrothermal synthesis process, it should be ensured that the reaction kettle is well sealed to avoid danger under high temperature and high pressure. After the reaction is completed, the reaction kettle should be naturally cooled to room temperature before opening.

[0051] A high-speed centrifuge with a speed of more than 8000 r / min is used for solid-liquid separation;

[0052] A forced air drying oven or a vacuum drying oven has precise temperature control function and is suitable for drying solid products; during heat treatment and calcination, the temperature should be strictly controlled to avoid overheating and cause fire or explosion. During operation, it should be kept away from flammable materials and good ventilation conditions should be ensured;

[0053] A high-temperature muffle furnace has precise temperature control and good heat preservation performance, and is suitable for heat treatment and calcination of catalysts;

[0054] For example, according to the method provided above, a specific example is verified, and the verification process is as follows:

[0055] Example 1

[0056] (1) Preparation of active component one

[0057] A solution A was prepared by dissolving 9.46 g of ammonium molybdate in 300 mL of deionized water, and a suspension B was prepared by adding 24.25 g of bismuth nitrate into 300 mL of deionized water. The solution A was added into the suspension B at 90 °C and stirred for 1 h, and then the suspension was transferred into a 1 L polytetrafluoroethylene-lined stainless steel autoclave, and hydrothermally synthesized at 180 °C for 24 h. The solid obtained by the hydrothermal synthesis was washed, centrifuged, dried, and then heat-treated at 650 °C for 2 h in a nitrogen atmosphere to obtain an active component one.

[0058] (2) Preparation of an active component two

[0059] A solution C was prepared by dissolving 30.00 g of ammonium heptamolybdate, 0.14 g of potassium nitrate, and 0.36 g of magnesium nitrate in 200 mL of deionized water at 70 °C, a solution D was prepared by dissolving 20.61 g of cobalt nitrate, 9.06 g of nickel nitrate, and 7.44 g of iron nitrate in 30 mL of deionized water, and a solution E was prepared by dissolving 7.56 g of bismuth nitrate in 5 mL of deionized water and 1 mL of nitric acid (65 wt%). The solution D and the solution E were added into the solution C at 70 °C to form a slurry, which was stirred for 1 h, and then dried at 140 °C for 24 h to obtain a block solid. The block solid was crushed to obtain an active component two.

[0060] (3) Preparation of a composite catalyst

[0061] The active component one and the active component two having a total weight of 40 g were mixed and then calcined at 500 °C for 6 h. The mass ratio of the active component one to the active component two was 1:11.5.

[0062] Example 2

[0063] The preparation conditions of the active component one and the active component two were the same as in Example 1, and the preparation conditions of the composite catalyst in the third step were changed as follows: the active component one and the active component two having a total weight of 40 g were mixed and then calcined at 500 °C for 6 h. The mass ratio of the active component one to the active component two was 1:5.67.

[0064] Example 3

[0065] The preparation conditions of the active component one and the active component two were the same as in Example 1, and the preparation conditions of the composite catalyst in the third step were changed as follows: the active component one and the active component two having a total weight of 40 g were mixed and then calcined at 500 °C for 6 h. The mass ratio of the active component one to the active component two was 1:1.5.

[0066] Example 4

[0067] Replace "0.14 g potassium nitrate" in the preparation method of active component two of Example 1 with "0.21 g potassium nitrate", and the remaining steps are the same as Example 1.

[0068] Example 5

[0069] Replace "0.36 g magnesium nitrate" in the preparation method of active component two of Example 1 with "0.19 g calcium nitrite", and the remaining steps are the same as Example 1.

[0070] Example 6

[0071] (1) Preparation of active component one

[0072] Dissolve 7.10 g of ammonium molybdate in 300 mL of deionized water to obtain solution A, add 24.25 g of bismuth nitrate to 300 mL of deionized water to obtain suspension B, add solution A to suspension B at 80°C and constant temperature stirring for 1 h, then transfer the suspension to a 1 L polytetrafluoroethylene lined stainless steel reaction kettle, hydrothermal synthesis at 160°C for 20 h, wash, centrifuge and dry the solid obtained by hydrothermal synthesis, and then heat treat at 700°C for 1 h in a nitrogen atmosphere to obtain active component one.

[0073] (2) Preparation of active component two

[0074] Dissolve 30.00 g of ammonium heptamolybdate, 0.14 g of potassium nitrate, and 0.36 g of magnesium nitrate in 200 mL of deionized water at 70°C to obtain solution C, dissolve 20.61 g of cobalt nitrate, 9.06 g of nickel nitrate, and 7.44 g of iron nitrate in 30 mL of deionized water to obtain solution D, dissolve 7.56 g of bismuth nitrate in 5 mL of deionized water and 1 mL of nitric acid (65 wt%) to obtain solution E, add solution D and solution E to solution C in sequence at 70°C to form a slurry, stir the slurry for 1 h, and then dry at 140°C for 24 h to obtain a blocky solid. After crushing the blocky solid, active component two is obtained.

[0075] (3) Preparation of composite catalyst

[0076] Mix the active component one and the active component two with a total weight of 40 g thoroughly, and then calcine at 470°C for 7 h. The mass ratio of active component one to active component two is 1:4.

[0077] Example 7:

[0078] (1) Preparation of active component one

[0079] A solution A was prepared by dissolving 9.46 g of ammonium molybdate in 300 mL of deionized water, and a suspension B was prepared by adding 24.25 g of bismuth nitrate into 300 mL of deionized water. The solution A was added into the suspension B at 90 °C and stirred for 1 h, and then the suspension was transferred into a 1 L polytetrafluoroethylene-lined stainless steel autoclave, which was hydrothermally synthesized at 180 °C for 24 h. After washing, centrifuging and drying, the hydrothermally synthesized solid was heat-treated at 650 °C for 2 h in a nitrogen atmosphere to obtain an active component one.

[0080] (2) Preparation of an active component two

[0081] A solution C was prepared by dissolving 30.00 g of ammonium heptamolybdate, 0.14 g of potassium nitrate and 0.36 g of magnesium nitrate in 300 mL of deionized water at 70 °C, a solution D was prepared by dissolving 20.61 g of cobalt nitrate, 9.06 g of nickel nitrate and 7.44 g of iron nitrate in 60 mL of deionized water, and a solution E was prepared by dissolving 7.56 g of bismuth nitrate in 5 mL of deionized water and 1 mL of nitric acid (65 wt%). The solution D and the solution E were added into the solution C in sequence to form a slurry at 70 °C, and the slurry was stirred for 1 h and then dried at 110 °C for 28 h to obtain a block solid, which was crushed to obtain the active component two.

[0082] (3) Preparation of a composite catalyst

[0083] The active component one and the active component two with a total weight of 40 g were mixed and then calcined at 600 °C for 5 h, wherein the mass ratio of the active component one to the active component two was 1:6.69.

[0084] Comparative Example 1

[0085] 40 g of the active component one in Example 1 was calcined at 500 °C for 6 h as a final product catalyst. Figure 4 Figure 1 shows a SEM image of the Bi2WO6 microspheres prepared.

[0086] Comparative Example 2

[0087] 40 g of the active component one in Example 1 without heat treatment was calcined at 500 °C for 6 h as a final product catalyst.

[0088] Comparative Example 3

[0089] 40 g of the active component two in Example 1 was calcined at 500 °C for 6 h as a final product catalyst.

[0090] Comparative Example 4

[0091] Take 3.2 g of Comparative Example 1 and 36.8 g of Comparative Example 3 after mixing as the final product catalyst.

[0092] The catalysts prepared in Examples 1 to 7 and Comparative Examples 1 to 4 were characterized by nitrogen physical adsorption-desorption, and the specific surface area (S BET ) obtained based on the Brunauer-Emmett-Teller (BET) method, the total pore volume (V total ) obtained by the nitrogen adsorption amount when 0=0.99, and the pore size distribution (PSD) data are shown in Table 1 below: S BET ) and the pore size distribution (PSD) data are shown in Table 1 below: P / P V pore ) and the pore size distribution (PSD) data are shown in Table 1 below:

[0093] Table 1

[0094]

[0095] From the above table data, the specific surface area and the pore volume of the active component one (Comparative Example 1) are large, and after mixing with the active component two, the specific surface area and the pore volume of the composite catalyst can be improved.

[0096] In summary, the Bi2WO6 microspheres obtained by hydrothermal synthesis are mixed with the Mo-Bi metal oxide prepared by coprecipitation to obtain a composite catalyst. The Bi2WO6 microspheres can not only act as an active phase for the reaction, but also improve the specific surface area and the pore volume of the composite catalyst.

[0097] The catalysts prepared in Examples 1 to 7 and Comparative Examples 1 to 4 were evaluated, and the evaluation data are shown in Table 2 below:

[0098] Table 2

[0099]

[0100] From the evaluation data of Examples 1, 2, Comparative Examples 1 and 3, it can be seen that after mixing the active component one and the active component two in a proper ratio, the performance of the composite catalyst is obviously improved compared with the single active component. Among them, Example 2 can achieve a propylene conversion of 99.4%, a propylene aldehyde yield of 85.3%, and a propylene acid yield of 9.3% under the space velocity condition of 900 h -1 , and still achieve a propylene conversion of 98.3%, a propylene aldehyde yield of 85.1%, and a propylene acid yield of 8.7% under the space velocity condition of 1200 h -1 ; from the evaluation data of Comparative Examples 1 and 2, it can be seen that heat treatment of the active component one can obviously improve its catalytic activity; from the evaluation data of Example 1 and Comparative Example 4, it can be seen that the catalytic effect of mixing the active component one and the active component two and then calcining is better than that of calcining the two and then mixing. ​

[0101] In summary, the composite catalyst of the present application can achieve 99.4% propylene conversion, 85.3% propylene aldehyde yield and 9.3% propylene acid yield under 900 h -1 of space velocity conditions, and still achieve 98.3% propylene conversion, 85.1% propylene aldehyde yield and 8.7% propylene acid yield under 1200 h -1 of space velocity conditions.

[0102] Finally, it should be noted that the above only describes the preferred embodiments of the present application, and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or equivalently replace some of the technical features, as long as they are within the spirit and principles of the present application. Any modification, equivalent replacement, improvement, etc. made within the scope of the present application shall be included in the protection scope of the present application.

Claims

1. A composite catalyst for the catalytic oxidation of propene to acrolein, characterized in that: The active component one and the active component two, the use mass ratio of the active component one and the active component two is 1:1-19; The active component one is bismuth tungstate microspheres obtained by hydrothermal synthesis, general formula is Bi a W1O x ; The active component two is a polyoxometalate obtained by coprecipitation, general formula: Mo 12 Bi b Co c Ni d Fe e A f B g O y ; Wherein, Bi is bismuth, W is tungsten, Mo is molybdenum, Co is cobalt, Ni is nickel, Fe is iron, O is oxygen; A is at least one selected from lithium, sodium, potassium, rubidium, cesium elements; B is one selected from beryllium, magnesium, calcium, strontium, barium elements; a, b, c, d, e, f, g are atomic ratios of each element, wherein a=0.5-2; b=0.8-1.3; c=4-6; d=2-3; e=0.8-2; f=0.05-0.

3.

2. The composite catalyst for the catalytic oxidation of propylene to acrolein according to claim 1, characterized in that: The preparation process of the active component one comprises the following steps: A1, dissolve the tungsten source in deionized water to obtain solution A, add the bismuth source to deionized water to obtain suspension B, drop solution A into suspension B under heating condition and constant temperature stirring for 1h; A2, transfer the stirred suspension into a stainless steel reaction kettle with a polytetrafluoroethylene liner for hydrothermal synthesis; A3, wash, centrifuge and dry the solid obtained by hydrothermal synthesis, and then heat treat under nitrogen atmosphere to obtain the active component one.

3. The composite catalyst for the catalytic oxidation of propylene to acrolein according to claim 2, characterized in that: In step A1, the tungsten source is sodium tungstate or ammonium tungstate, the bismuth source is bismuth nitrate or bismuth subnitrate, and the heating temperature is 60-98 ℃.

4. The composite catalyst for the catalytic oxidation of propylene to acrolein according to claim 3, characterized in that: In step A2, the hydrothermal synthesis temperature is 140-200 ℃, and the hydrothermal synthesis time is 20-28 h.

5. The composite catalyst for the catalytic oxidation of propylene to acrolein according to claim 1, characterized in that: In step A3, the heat treatment temperature is 600-800 ℃, the heat treatment time is 1-4 h, the centrifugal separation condition is centrifugation at a speed of 8000 r / min for 3 min, and the drying condition is drying at 80 ℃ for 12 h.

6. The composite catalyst for the catalytic oxidation of propylene to acrolein according to claim 5, characterized in that: The preparation process of the active component two is as follows: B1, dissolve the Mo source, the A source and the B source in deionized water to obtain solution C under heating condition, dissolve the Co source, the Ni source and the Fe source in deionized water to obtain solution D, and dissolve the Bi source in nitric acid to obtain solution E; B2, add solution D and solution E to solution C in sequence to form a slurry; B3, dry the slurry and crush to obtain the active component two.

7. The composite catalyst for the catalytic oxidation of propylene to acrolein according to claim 6, characterized in that: In step B1, the Mo source is ammonium heptamolybdate, the Bi source, the Co source, the Ni source and the Fe source are nitrate, the A source is nitrate or chloride, and the B source is nitrate or hydroxide.

8. The composite catalyst for the catalytic oxidation of propylene to acrolein according to claim 7, characterized in that: The total mass of the Mo source, the A source, the B source, the Co source, the Ni source, the Fe source and the Bi source and the total mass of deionized water are in a ratio of 1:1.5-6.

9. The composite catalyst for the catalytic oxidation of propylene to acrolein according to claim 8, characterized in that: In step B3, the drying temperature is 110-180 ℃, and the drying time is 20-30 h.

10. A process for the preparation of a composite catalyst for the catalytic oxidation of propene to acrolein, based on a composite catalyst for the catalytic oxidation of propene to acrolein according to any one of claims 1 to 9, characterized in that: The preparation process comprises the following steps: S1, mix the active component one and the active component two in a mass ratio of 1:1-19 to form a mixture; S2, calcine the mixture to obtain a finished catalyst, and the calcination temperature is 450-600 ℃, and the calcination time is 5 h-8 h.

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