Catalyst for preparing acrolein and acrylic acid through selective oxidation of propylene and preparation method of catalyst

Abstract

The invention discloses a catalyst for preparing acrolein and acrylic acid through selective oxidation of propylene, a preparation method of the catalyst and a preparation method of acrolein and acrylic acid. The general formula of the catalyst is MoBiaFebXcYdZePfOj, X is selected from at least one of Mg, Co, Ni, Ca, Cu, Zn and Mn, Y is selected from at least one of Nb, Sb and W, and Z is selected from at least one of K, Rb, Na, Li and Cs. The catalyst is used for preparing acrolein and acrylic acid through olefin oxidation, especially propylene oxidation, has the advantage of high total yield of acrolein and acrylic acid, and is good in structural stability.

Description

Technical Field

[0001] The present invention relates to the field of catalysts, in particular to a catalyst for preparing acrolein and acrylic acid through selective oxidation of propylene and a preparation method thereof, and a preparation method of acrolein and acrylic acid. Background Art

[0002] Selective oxidation of olefins to prepare unsaturated acids is an important chemical process. In industry, olefins are usually oxidized to obtain unsaturated aldehydes, and then the unsaturated aldehydes are oxidized to obtain unsaturated acids. This process usually adopts two-stage production, using two reactors and two catalysts under different reaction conditions. One stage of reaction mainly produces acrolein, and about 20% of acrylic acid. The active components of the catalyst are complex Mo and Bi composite oxide systems. The improvement of the catalyst is mainly carried out from the aspects of catalyst activity and stability, such as adding transition metals to the active components to improve activity and increase the single yield of the product; adding rare earth elements to improve redox ability; adding Fe, Co, Ni and other elements to inhibit the sublimation of Mo, stabilize the active components of the catalyst, and increase the service life of the catalyst. In addition, due to the violent exothermic phenomenon in the reaction, it is very important to control the reaction temperature of the catalyst bed. The formation of hot spots not only deteriorates the reaction results, but also shortens the service life of the catalyst and affects the stable operation of the device.

[0003] It is generally believed that in the first step of the reaction of propylene oxidation to produce acrolein, olefins are adsorbed on the catalyst surface, an α-H is removed by the metal oxide, and a free radical intermediate is formed, which is inserted into the product through oxygen or nitrogen. In this process, the catalyst undergoes a redox cycle, in which it loses the oxygen atom involved in the insertion reaction, is reduced, and then is reoxidized by the oxygen in the reaction gas, and the active oxygen atom is supplemented through the migration of oxygen. Therefore, the catalyst is required to have good oxygen migration ability to maintain the catalyst structure and redox balance. Generally, transition metal composite oxides such as Mo, V, Bi, Te, Nb, and Fe are used (Catalysis Today 49 (1999) 141-153). In the selective oxidation reaction, the distance between active sites has an important influence on the selective oxidation reaction. It is generally believed that separated active sites (site isolation) are beneficial to the selective oxidation reaction (AICHE J.9 (1963), 755).

[0004] US4224187 and US4248803 proposed to improve the olefin conversion rate and target product yield by improving the catalyst composition and their usage ratio and catalyst preparation method. For the selective oxidation of isobutylene, there is a problem of low reaction selectivity. The isobutylene conversion rate is as high as 99%, but the total yield of methacrolein and methacrylic acid is only 73.6%.

[0005] US6268529 proposes a propylene oxidation catalyst with a propylene conversion rate of 98.1%, an acrolein yield of 65.3%, an acrylic acid yield of 20.8%, and a total yield of acrolein and acrylic acid of 86.1%.

[0006] CN1564709A improves catalyst performance by adding organic carboxylic acid to overcome the catalyst unevenness caused by the stratification of metal salts during the catalyst preparation coprecipitation process. It is used for the selective oxidation reaction of propylene, wherein the propylene conversion rate is as high as 98.12%, the acrolein selectivity is as high as 82.53%, and the total yield of acrolein and acrylic acid is 91.05%.

[0007] CN1210511A, CN1283604A and CN1314331A achieve the purpose of controlling the reaction hot spots and prolonging the catalyst stability by configuring multiple catalyst layers with gradually increasing reaction activity along the axial direction of the reactor from the reaction gas inlet to the outlet. However, the structural stability of the catalyst needs to be further improved. Summary of the invention

[0008] In view of the problems of low yield and low stability of the target product of the oxidation catalyst in the prior art, the present invention provides a new oxidation catalyst, which is used for olefin oxidation, such as propylene oxidation to prepare acrolein and acrylic acid, and has the advantages of high total yield of acrolein and acrylic acid, and good catalyst stability.

[0009] The first aspect of the present invention provides a catalyst for selective oxidation of propylene to prepare acrolein and acrylic acid, the general formula of the catalyst is: MoBi a Fe b X c Y d Z e P f O j , wherein X is selected from at least one of Mg, Co, Ni, Ca, Cu, Zn, and Mn; Y is selected from at least one of Nb, Sb, and W; Z is selected from at least one of K, Rb, Na, Li, and Cs; a is the molar ratio of Bi to Mo, and the value of a is 0.1 to 0.6; b is the molar ratio of Fe to Mo, and the value of b is 0.1 to 0.5; c is the molar ratio of X to Mo, and the value of c is 0.2 to 1.0; d is the molar ratio of Y to Mo, and the value of d is 0.1 to 0.5; e is the molar ratio of Z to Mo, and the value of e is 0.01 to 0.06; f is the molar ratio of P to Mo, and the value of f is 0.1 to 0.6; j is the total number of oxygen atoms required to satisfy the valence of other elements; f / a is 0.8 to 1.2.

[0010] According to a preferred embodiment of the present invention, the value of a is 0.2-0.4; the value of b is 0.2-0.4; the value of c is 0.3-0.7; the value of d is 0.2-0.4; the value of e is 0.02-0.05; the value of f is 0.2-0.5; and f / a is 0.9-1.1.

[0011] The catalyst of the present invention has high oxidation activity and stable structure. The introduction of a small amount of P can well avoid the problem of reduced structural stability due to charge imbalance, thereby improving the stability of the catalyst.

[0012] The second aspect of the present invention provides a method for preparing a catalyst for preparing acrolein and acrylic acid by selective oxidation of propylene, comprising refluxing a first solution containing a Mo compound, a P compound and a Y compound, and then adjusting the pH value of the first solution to 0-3; adding a second solution containing a Bi compound to form a first slurry, and refluxing; mixing the first slurry with a third solution containing a Fe compound, an X compound and a Z compound to form a second slurry; and drying and calcining.

[0013] According to a preferred embodiment of the present invention, the preparation method comprises refluxing a first solution containing a Mo compound, a P compound and a Y compound at 80-100°C for 2-4 hours, adjusting the pH value of the first solution to 0-3, adding a second solution containing a Bi compound to form a first slurry, and refluxing at 80-100°C for 2-4 hours. The first slurry is mixed with a third solution containing a Fe compound, an X compound and a Z compound to form a second slurry, and then dried and calcined.

[0014] The amount of each substance fed in the preparation method of the present invention satisfies the general formula of the catalyst prepared: MoBi a Fe b X c Y d Z e P f O j , wherein X is at least one selected from Mg, Co, Ni, Ca, Cu, Zn and Mn; Y is at least one selected from Nb, Sb and W; Z is at least one selected from K, Rb, Na, Li and Cs; a is the molar ratio of Bi to Mo, and the value of a is 0.1-0.6; b is the molar ratio of Fe to Mo, and the value of b is 0.1-0.5; c is the molar ratio of X to Mo, and the value of c is 0.2-1.0; d is the molar ratio of Y to Mo, and the value of d is 0.1-0.5; e is the molar ratio of Z to Mo, and the value of e is 0.01-0.06; f is the molar ratio of P to Mo, and the value of f is 0.1-0.6; j is the total number of oxygen atoms required to satisfy the valence of other elements. f / a is 0.8-1.2.

[0015] According to a preferred embodiment of the present invention, the value of a is 0.2-0.4.

[0016] According to a preferred embodiment of the present invention, the value of b is 0.2-0.4.

[0017] According to a preferred embodiment of the present invention, the value of c is 0.3-0.7.

[0018] According to a preferred embodiment of the present invention, the value of d is 0.2-0.4.

[0019] According to a preferred embodiment of the present invention, the value of e is 0.02-0.05.

[0020] According to a preferred embodiment of the present invention, the value of f is 0.2-0.5.

[0021] According to a preferred embodiment of the present invention, f / a is 0.9-1.1.

[0022] The catalyst prepared by the above method of the present invention can further improve the activity and selectivity of the catalyst.

[0023] According to the present invention, there is no special requirement for the drying conditions. For the present invention, the drying conditions preferably include: a temperature of 50 to 80° C., such as 50° C., 60° C., 70° C., 80° C., and any value therebetween.

[0024] According to the present invention, the drying time can be determined according to the drying temperature, and preferably the drying time is 1 to 16 hours, such as 1 hour, 2 hours, 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, and any value therebetween.

[0025] According to the present invention, there is no special requirement for the calcination conditions. For the present invention, the calcination conditions preferably include: a temperature of 400-650° C. For example, 400° C., 450° C., 500° C., 550° C., 600° C., 650° C., and any value therebetween.

[0026] According to the present invention, the calcination time can be determined according to the calcination temperature, and preferably the calcination time is 1 to 12 hours, such as 1 hour, 2 hours, 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, and any value therebetween.

[0027] According to a preferred embodiment of the present invention, the calcination atmosphere is an inert atmosphere and / or an atmosphere containing O2. However, from an economic point of view, the calcination atmosphere is preferably air. Unless otherwise specified, the calcination atmosphere in the present invention is air.

[0028] According to a preferred embodiment of the present invention, the solution after mixing in each process is a homogeneous solution, a suspension or a mixture of a solution and a suspension.

[0029] According to the present invention, a solid can be obtained by steps such as concentration. For the present invention, the solid is preferably obtained by evaporation concentration at 60 to 80°C.

[0030] According to a preferred embodiment of the present invention, the amount of water used in the first solution and the second solution has a wide selection range, with the purpose of being able to fully dissolve the compound.

[0031] According to a preferred embodiment of the present invention, the Mo compound, the Y compound, the Bi compound, the Fe compound, the X compound, the Z compound and the P compound may be selected from nitrates, ammonium salts, sulfates, oxides, hydroxides, chlorides, acetates and the like.

[0032] According to a preferred embodiment of the present invention, the Mo compound may be selected from, but not limited to, one or more of ammonium molybdate, molybdenum trioxide, molybdenum nitrate, molybdic acid and sodium molybdate.

[0033] According to a preferred embodiment of the present invention, the Bi compound may be selected from, but not limited to, one or more of: bismuth nitrate, bismuth trioxide, bismuth sulfate, bismuth chloride and bismuth acetate.

[0034] According to a preferred embodiment of the present invention, the Fe compound may be selected from but not limited to: one or more of ferric nitrate, ferric sulfate, ferric chloride, ferric oxide and ferrous sulfate.

[0035] According to a preferred embodiment of the present invention, the X compound can be selected from but not limited to: one or more of cobalt nitrate, cobalt sulfate, cobalt chloride, magnesium nitrate, magnesium sulfate, magnesium chloride, magnesium oxide, magnesium acetate, nickel nitrate, nickel sulfate, nickel chloride, calcium nitrate, calcium acetate, calcium chloride, copper nitrate, zinc nitrate and manganese nitrate.

[0036] According to a preferred embodiment of the present invention, the Y compound can be selected from but not limited to: one or more of niobium oxalate, niobium pentoxide, niobium pentachloride, niobic acid, niobyl nitrate, ammonium niobium oxalate, antimony nitrate, antimony tartrate, ammonium tungstate, tungsten trioxide, tungstic acid, sodium tungstate and ammonium metatungstate.

[0037] According to a preferred embodiment of the present invention, the Z compound may be selected from but not limited to: one or more of potassium nitrate, rubidium nitrate, sodium nitrate, sodium sulfate, sodium chloride, sodium acetate, sodium hydroxide, lithium nitrate and cesium nitrate.

[0038] According to a preferred embodiment of the present invention, the P compound may be selected from but not limited to: one or more of phosphoric acid, ammonium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, phosphorus pentoxide and phosphorus chloride.

[0039] Mo-Bi system composite oxides are important catalytic systems for selective oxidation or ammoxidation of olefins, and Bi is considered to be the active site for the first step of dehydrogenation. Bi salts are easily precipitated in neutral or alkaline environments, which will affect the dispersion of Bi in Mo-based composite oxides. The solubility product of BiPO4 is very small, and it does not dissolve under acidic conditions, so it can fix Bi very well. P is easily dispersed in Mo oxides. Therefore, P is first dispersed in Mo, and then under acidic conditions, the dispersed P is used to anchor Bi, so that Bi is better dispersed in the composite oxide to form independent active sites (isolated sites), which can greatly improve the performance of the catalyst.

[0040] The method of the invention is used for the reaction of preparing acrolein by oxidizing propylene, has the advantages of high total yield of acrolein and acrylic acid, and good catalyst structure stability.

[0041] The third aspect of the present invention provides a catalyst obtained by the preparation method.

[0042] The general formula of the catalyst components is: MoBi a Fe b X c Y d Z e P f O j , wherein X is at least one selected from Mg, Co, Ni, Ca, Cu, Zn and Mn; Y is at least one selected from Nb, Sb and W; Z is at least one selected from K, Rb, Na, Li and Cs; a is the molar ratio of Bi to Mo, and the value of a is 0.1-0.6; b is the molar ratio of Fe to Mo, and the value of b is 0.1-0.5; c is the molar ratio of X to Mo, and the value of c is 0.2-1.0; d is the molar ratio of Y to Mo, and the value of d is 0.1-0.5; e is the molar ratio of Z to Mo, and the value of e is 0.01-0.06; f is the molar ratio of P to Mo, and the value of f is 0.1-0.6; j is the total number of oxygen atoms required to satisfy the valence of other elements. f / a is 0.8-1.2.

[0043] According to a preferred embodiment of the present invention, the value of a is 0.2-0.4; the value of b is 0.2-0.4; the value of c is 0.3-0.7; the value of d is 0.2-0.4; the value of e is 0.02-0.05; the value of f is 0.2-0.5. f / a is 0.9-1.1.

[0044] The catalyst of the present invention has high oxidation activity and stable structure. Dispersed P is used to anchor Bi, so that Bi has good dispersion and can form independent active sites. The catalyst has good activity and selectivity.

[0045] The fourth aspect of the present invention provides a method for preparing acrolein and acrylic acid, comprising reacting propylene with an oxidizing gas containing oxygen in the presence of a catalyst, wherein the catalyst is the catalyst described above or a catalyst obtained by the preparation method described above.

[0046] According to a preferred embodiment of the present invention, the oxygen-containing oxidizing gas may be pure oxygen or oxygen-enriched gas, but air is preferred from an economical point of view.

[0047] According to a preferred embodiment of the present invention, the reaction conditions include: a temperature of 300 to 550°C, preferably 330 to 380°C.

[0048] According to a preferred embodiment of the present invention, the reaction conditions include: the pressure is 0.01 to 0.08 MPa (gauge pressure).

[0049] According to a preferred embodiment of the present invention, in terms of volume ratio, propylene:air=1:(6-8).

[0050] According to a preferred embodiment of the present invention, in order to make the reaction more stable and controllable, it is preferably carried out in the presence of a diluent gaseous material, preferably water vapor.

[0051] According to a preferred embodiment of the present invention, the reaction conditions include: propylene: air: optional water vapor = 1: (6-8): (0.5-5).

[0052] According to a preferred embodiment of the present invention, the reaction conditions include: raw gas volume mass space velocity: 600-1200 mL / g·h.

[0053] The present invention adopts the method of pre-dispersing the P component in Mo and then utilizing the combination of Bi and P to make the active component Bi dispersed well, thereby improving the performance of the catalyst. The catalyst of the present invention is used for olefin oxidation, especially propylene oxidation to prepare acrolein and acrylic acid, and has the advantages of high total yield of acrolein and acrylic acid, and good catalyst structural stability. DETAILED DESCRIPTION

[0054] In order to make the present invention more easily understood, the present invention will be described in detail below in conjunction with embodiments. These embodiments are only for illustration and are not intended to limit the application scope of the present invention.

[0055] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0056] The raw materials used in the examples and comparative examples, unless otherwise specified, are disclosed in the prior art, for example, they can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0057] In the embodiments and comparative examples of the present invention, the catalyst evaluation conditions are as follows:

[0058] Reactor: Fixed bed single tube reactor, inner diameter 26.0 mm, reactor length 800 mm

[0059] Catalyst: 200 g

[0060] Reaction temperature: 360℃

[0061] Reaction pressure: 0.03MPa (gauge pressure)

[0062] Propylene: air (raw material molar ratio) = 1: 7.2

[0063] Propylene: water vapor = 1: 1.8

[0064] Raw gas volume mass space velocity: 1000mL / g·h

[0065] The reaction product was absorbed by 0°C dilute acid and analyzed by gas chromatography (Agilent 7890A). The carbon balance was calculated and the data were valid when the carbon balance was (95-105)%.

[0066] Propylene conversion, product yield and selectivity are defined as:

[0067]

[0068]

[0069]

[0070] [Example 1]

[0071] Weigh ammonium molybdate equivalent to 1 mol of Mo, diammonium hydrogen phosphate of 0.3 mol of P and ammonium niobium oxalate of 0.2 mol of Nb and dissolve them in 3000 g of water to obtain solution 1. After reflux at 90°C for 3 hours, adjust the pH value to 2 with nitric acid. Weigh bismuth nitrate equivalent to 0.3 mol of Bi and dissolve it in 150 ml of 10% nitric acid to obtain solution 2, and add solution 1, reflux at 80°C for 3 hours to obtain slurry 1. Iron nitrate containing 0.3 mol of Fe, cobalt nitrate containing 0.5 mol of Co, and rubidium nitrate containing 0.04 mol of Rb are dissolved in 200 g of water to obtain solution 3. Slurry 1 and solution 3 are mixed to obtain slurry 2. Concentrate at 65°C to a viscous paste, dry at 80°C for 6 hours, and then calcine in an air atmosphere at 550°C for 2 hours to obtain the catalyst MoBi. 0.3 Fe 0.3 Co 0.5 Nb 0.2 R 0.04 P 0.3 O j .

[0072] [Example 2]

[0073] Weigh ammonium molybdate equivalent to 1 mol of Mo, diammonium hydrogen phosphate 0.1 mol of P and ammonium niobium oxalate 0.2 mol of Nb and dissolve them in 3000 g of water to obtain solution 1. After reflux at 90°C for 3 hours, adjust the pH value to 2 with nitric acid. Weigh bismuth nitrate equivalent to 0.12 mol of Bi and dissolve it in 150 ml of 10% nitric acid to obtain solution 2, and add solution 1, reflux at 80°C for 3 hours to obtain slurry 1. Iron nitrate containing 0.3 mol of Fe, cobalt nitrate containing 0.5 mol of Co, and rubidium nitrate containing 0.04 mol of Rb are dissolved in 200 g of water to obtain solution 3. Slurry 1 and solution 3 are mixed to obtain slurry 2. Concentrate at 65°C to a viscous paste, dry at 80°C for 6 hours, and then calcine at 550°C in an air atmosphere for 2 hours to obtain the catalyst MoBi. 0.12 Fe 0.3 Co 0.5 Nb 0.2 R 0.04 P 0.1 O j .

[0074] [Example 3]

[0075] Weigh ammonium molybdate equivalent to 1 mol of Mo, diammonium hydrogen phosphate 0.6 mol of P and ammonium niobium oxalate 0.2 mol of Nb and dissolve them in 3000 g of water to obtain solution 1. After reflux at 90°C for 3 hours, adjust the pH value to 2 with nitric acid. Weigh bismuth nitrate equivalent to 0.5 mol of Bi and dissolve it in 150 ml of 10% nitric acid to obtain solution 2, and add solution 1, reflux at 80°C for 3 hours to obtain slurry 1. Iron nitrate containing 0.3 mol of Fe, cobalt nitrate containing 0.5 mol of Co, and rubidium nitrate containing 0.04 mol of Rb are dissolved in 200 g of water to obtain solution 3. Slurry 1 and solution 3 are mixed to obtain slurry 2. Concentrate at 65°C to a viscous paste, dry at 80°C for 6 hours, and then calcine in an air atmosphere at 550°C for 2 hours to obtain the catalyst MoBi. 0.5 Fe 0.3 Co 0.5 Nb 0.2 R 0.04 P 0.6 O j .

[0076] [Example 4]

[0077] Weigh ammonium molybdate equivalent to 1 mol of Mo, diammonium hydrogen phosphate 0.3 mol of P, 0.1 mol of antimony tartrate and 0.4 mol of ammonium metatungstate W and dissolve them in 3000 g of water to obtain solution 1. After reflux at 90°C for 3 hours, adjust the pH value to 2 with nitric acid. Weigh bismuth nitrate equivalent to 0.3 mol of Bi and dissolve it in 150 ml of 10% nitric acid to obtain solution 2, and add solution 1, reflux at 80°C for 3 hours to obtain slurry 1. Iron nitrate containing 0.1 mol of Fe, cobalt nitrate containing 0.5 mol of Co, nickel nitrate containing 0.5 mol of Ni, and potassium nitrate containing 0.01 mol of K are dissolved in 200 g of water to obtain solution 3. Slurry 1 and solution 3 are mixed to obtain slurry 2. Concentrate at 65°C to a viscous paste, dry at 80°C for 6 hours, and then calcine in an air atmosphere at 550°C for 2 hours to obtain the catalyst MoBi. 0.3 Fe 0.1 Co 0.5 Ni 0.5 Sb 0. 1W 0.4 K 0.01 P 0.3 O j .

[0078] [Example 5]

[0079] Weigh ammonium molybdate equivalent to 1 mol of Mo, diammonium hydrogen phosphate 0.3 mol of P and ammonium metatungstate 0.1 mol of W and dissolve them in 3000 g of water to obtain solution 1. After reflux at 90°C for 3 hours, adjust the pH value to 2 with nitric acid. Weigh bismuth nitrate equivalent to 0.3 mol of Bi and dissolve it in 150 ml of 10% nitric acid to obtain solution 2, and add solution 1, reflux at 80°C for 3 hours to obtain slurry 1. Ferric nitrate containing 0.5 mol of Fe, magnesium nitrate containing 0.2 mol of Mg, rubidium nitrate containing 0.03 mol of Rb, and sodium nitrate containing 0.03 mol of Na are dissolved in 200 g of water to obtain solution 3. Slurry 1 and solution 3 are mixed to obtain slurry 2. Concentrate at 65°C to a viscous paste, dry at 80°C for 6 hours, and then calcine in an air atmosphere at 550°C for 2 hours to obtain the catalyst MoBi. 0.3 Fe 0.5 Mg 0.2 W 0.1 R 0.03 Na 0.03 P 0.3 O j .

[0080] [Example 6]

[0081] Weigh ammonium molybdate equivalent to 1 mol of Mo, diammonium hydrogen phosphate of 0.45 mol of P and ammonium niobium oxalate of 0.2 mol of Nb and dissolve them in 3000 g of water to obtain solution 1. After reflux at 90°C for 3 hours, adjust the pH value to 2 with nitric acid. Weigh bismuth nitrate equivalent to 0.5 mol of Bi and dissolve it in 150 ml of 10% nitric acid to obtain solution 2, and add solution 1, reflux at 80°C for 3 hours to obtain slurry 1. Iron nitrate containing 0.3 mol of Fe, cobalt nitrate containing 0.5 mol of Co, and rubidium nitrate containing 0.04 mol of Rb are dissolved in 200 g of water to obtain solution 3. Slurry 1 and solution 3 are mixed to obtain slurry 2. Concentrate at 65°C to a viscous paste, dry at 80°C for 6 hours, and then calcine in an air atmosphere at 550°C for 2 hours to obtain the catalyst MoBi. 0.5 Fe 0.3 Co 0.5 Nb 0.2 R 0.04 P 0.45 O j .

[0082] [Comparative Example 1]

[0083] Weigh ammonium molybdate equivalent to 1 mol of Mo and ammonium niobium oxalate equivalent to 0.2 mol of Nb and dissolve them in 3000 g of water to obtain solution 1. After reflux at 90°C for 3 hours, adjust the pH value to 2 with nitric acid. Weigh bismuth nitrate equivalent to 0.3 mol of Bi and dissolve it in 150 ml of 10% nitric acid to obtain solution 2, and add solution 1, reflux at 80°C for 3 hours to obtain slurry 1. Iron nitrate containing 0.3 mol of Fe, cobalt nitrate containing 0.5 mol of Co, and rubidium nitrate containing 0.04 mol of Rb are dissolved in 200 g of water to obtain solution 3. Slurry 1 and solution 3 are mixed to obtain slurry 2. Concentrate at 65°C to a viscous paste, dry at 80°C for 6 hours, and then calcine in an air atmosphere at 550°C for 2 hours to obtain the catalyst MoBi. 0.3 Fe 0.3 Co 0.5 Nb 0.2 R 0.04 O j .

[0084] [Comparative Example 2]

[0085] Weigh ammonium molybdate equivalent to 1 mol of Mo, diammonium hydrogen phosphate of 0.5 mol of P and ammonium niobium oxalate of 0.2 mol of Nb and dissolve them in 3000 g of water to obtain solution 1. After reflux at 90°C for 3 hours, adjust the pH value to 2 with nitric acid. Weigh bismuth nitrate equivalent to 0.3 mol of Bi and dissolve it in 150 ml of 10% nitric acid to obtain solution 2, and add solution 1, reflux at 80°C for 3 hours to obtain slurry 1. Iron nitrate containing 0.3 mol of Fe, cobalt nitrate containing 0.5 mol of Co, and rubidium nitrate containing 0.04 mol of Rb are dissolved in 200 g of water to obtain solution 3. Slurry 1 and solution 3 are mixed to obtain slurry 2. Concentrate at 65°C to a viscous paste, dry at 80°C for 6 hours, and then calcine in an air atmosphere at 550°C for 2 hours to obtain the catalyst MoBi. 0.3 Fe 0.3 Co 0.5 Nb 0.2 R 0.04 P 0.5 O j .

[0086] [Comparative Example 3]

[0087] Weigh ammonium molybdate equivalent to 1 mol of Mo, diammonium hydrogen phosphate 0.3 mol of P and ammonium niobium oxalate 0.2 mol of Nb and dissolve them in 3000 g of water to obtain solution 1, reflux at 90°C for 3 h, and adjust the pH value to 5 with nitric acid. Weigh bismuth nitrate equivalent to 0.3 mol of Bi and dissolve it in 150 ml of 10% nitric acid to obtain solution 2, and add solution 1, reflux at 80°C for 3 h to obtain slurry 1. 0.3 mol of Fe ferric nitrate, 0.5 mol of Co cobalt nitrate, and 0.04 mol of Rb rubidium nitrate are dissolved in 200 g of water to obtain solution 3. Slurry 1 and solution 3 are mixed to obtain slurry 2. Concentrate at 65°C to a viscous paste, dry at 80°C for 6 hours, and then calcine at 550°C in an air atmosphere for 2 hours to obtain the catalyst MoBi. 0.3 Fe 0.3 Co 0.5 Nb 0.2 R 0.04 P 0.3 O j .

[0088] The obtained catalyst was evaluated and tested, and the results are shown in Table 1.

[0089] Table 1

[0090]

Claims

1. A catalyst for selective oxidation of propylene to prepare acrolein and acrylic acid, the general formula of the catalyst being: MoBi a Fe b X c Y d Z e P f O j , wherein X is selected from at least one of Mg, Co, Ni, Ca, Cu, Zn, and Mn; Y is selected from at least one of Nb, Sb, and W; Z is selected from at least one of K, Rb, Na, Li, and Cs; a is the molar ratio of Bi to Mo, and the value of a is 0.1 to 0.6; b is the molar ratio of Fe to Mo, and the value of b is 0.1 to 0.5; c is the molar ratio of X to Mo, and the value of c is 0.2 to 1.0; d is the molar ratio of Y to Mo, and the value of d is 0.1 to 0.5; e is the molar ratio of Z to Mo, and the value of e is 0.01 to 0.06; f is the molar ratio of P to Mo, and the value of f is 0.1 to 0.6; j is the total number of oxygen atoms required to satisfy the valence of other elements; f / a is 0.8 to 1.

2.

2. The catalyst according to claim 1, characterized in that: The value of a is 0.2~0.4; the value of b is 0.2~0.4; the value of c is 0.3~0.7; the value of d is 0.2~0.4; the value of e is 0.02~0.05; the value of f is 0.2~0.5; f / a is 0.9~1.

1.

3. A method for preparing a catalyst for selectively oxidizing propylene to prepare acrolein and acrylic acid, comprising refluxing a first solution containing a Mo compound, a P compound and a Y compound, and then adjusting the pH value of the first solution to 0 to 3; adding a second solution containing a Bi compound to form a first slurry, and refluxing; The first slurry is mixed with a third solution containing an Fe compound, an X compound, and a Z compound to form a second slurry; and the mixture is dried and calcined.

4. The preparation method according to claim 3, characterized in that: The amount of each substance fed to the catalyst is such that the general formula of the catalyst prepared is: MoBi a Fe b X c Y d Z e P f O j , wherein X is selected from at least one of Mg, Co, Ni, Ca, Cu, Zn, and Mn; Y is selected from at least one of Nb, Sb, and W; Z is selected from at least one of K, Rb, Na, Li, and Cs; a is the molar ratio of Bi to Mo, and the value of a is 0.1 to 0.6; b is the molar ratio of Fe to Mo, and the value of b is 0.1 to 0.5; c is the molar ratio of X to Mo, and the value of c is 0.2 to 1.0; d is the molar ratio of Y to Mo, and the value of d is 0.1 to 0.5; e is the molar ratio of Z to Mo, and the value of e is 0.01 to 0.06; f is the molar ratio of P to Mo, and the value of f is 0.1 to 0.6; j is the total number of oxygen atoms required to satisfy the valence of other elements; f / a is 0.8 to 1.

2.

5. The preparation method according to claim 3, characterized in that: The first solution is refluxed at 80-100°C for 2-4h.

6. The preparation method according to claim 3, characterized in that: The first slurry is refluxed at 80-100° C. for 2-4 hours.

7. The preparation method according to claim 3, characterized in that: The drying conditions include: a temperature of 50 to 80°C and a time of 1 to 16 hours; and / or, The calcination conditions include: temperature of 400 to 650° C. and time of 1 to 12 hours.

8. The catalyst obtained according to the preparation method according to any one of claims 3 to 7.

9. A method for preparing acrolein and acrylic acid, comprising reacting propylene with an oxidizing gas containing oxygen in the presence of a catalyst, wherein: The catalyst is the catalyst according to claim 1 or 2 or the catalyst obtained by the preparation method according to any one of claims 3 to 7.

10. The method for preparing acrolein and acrylic acid according to claim 9, characterized in that: The reaction is carried out in the presence of a diluent gaseous material. Preferably, the diluent gaseous material is water vapor.

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