A multi-level pore molybdenum-bismuth composite metal oxide catalyst, a preparation method and application thereof

Abstract

The application provides a multi-level hole molybdenum-bismuth composite metal oxide catalyst and a preparation method thereof. 12 Bi 1.5 Fe 1.5 Co5Ce x Gd y K 0.5 O / TiO2, wherein 0 < x <= 1.2 and 0 < y <= 0.3. The catalyst comprises a carrier and a composite metal oxide, the composite metal oxide is dispersed in the carrier, the carrier is a multi-level hole TiO2, and the composite metal oxide is a composite oxide of molybdenum-bismuth-iron-cobalt-potassium and at least two kinds of rare earth metals. The catalyst is prepared by a deposition precipitation method. The multi-level hole molybdenum-bismuth composite metal oxide catalyst prepared by the application has a large specific surface area and contains at least two kinds of rare earth metals, which promotes high dispersion of active components, a synergistic effect between the rare earth metals, an increase in the number of active oxygen species and an increase in the selectivity of the catalyst for selective oxidation products.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalyst preparation, in particular to a multi-level hole molybdenum bismuth composite metal oxide catalyst and a preparation method and application thereof. BACKGROUND

[0002] Isobutene, as a kind of low-carbon olefin, is mainly derived from petroleum cracking and isobutane dehydrogenation technology. With the increase of domestic isobutene production, the clean utilization of high value of isobutene becomes more and more important. The downstream products of isobutene mainly include methyl methacrylate, isoprene, butyl rubber and polyisobutene products. According to the isobutene consumption structure in recent years, the isobutene consumption structure of preparing methyl methacrylate from isobutene accounts for a large proportion. Methyl methacrylate is an extremely important raw material and polymerization monomer in chemical production, and is widely used in automobiles, buildings, electronics and advertising decoration.

[0003] At present, there are three kinds of process routes for preparing methyl methacrylate from isobutene oxidation: isobutene is oxidized to prepare methyl methacrylaldehyde (MAL), and then oxidized to obtain methyl methacrylate; this method has the disadvantages of long process, low yield, etc. Isobutene is oxidized to prepare methyl methacrylate, and then esterified to methyl methacrylate; this method has not been industrialized. Isobutene is oxidized to prepare MAL, and then directly oxidized and esterified with methanol to prepare methyl methacrylate; this method can greatly reduce the production cost due to the shorter synthesis route, and is more green. From the scientific point of view, the selective oxidation of isobutene to prepare MAL is one of the necessary steps of isobutene oxidation method, and is also the most critical step. On the one hand, isobutene and more active product MAL both have two same position active α-CH3 and are easy to undergo deep oxidation under reaction conditions; on the other hand, the reaction by-products and unreacted isobutene are not conducive to the catalyst used in the later oxidation step. Therefore, how to realize the efficient selective activation of isobutene C-H bond and make it directional conversion to MAL is a very challenging technical problem, and has a great theoretical research significance.

[0004] The preparation of MAL from isobutene is an exothermic reaction, and the selectivity of the target product is reduced due to the increase of by-products in the process of obtaining the target product. The reaction is usually activated by Mo-Bi composite metal oxides. The preparation methods of Mo-Bi composite metal oxides include direct mixing method, coprecipitation method and hydrothermal synthesis method. The direct mixing method is to mix the metal precursor solution of Mo with the metal precursor solution containing Bi, Fe, Co and the like, without using a precipitant for precipitation. The coprecipitation method mixes the metal precursor solution of Mo with the metal precursor solution containing Bi, Fe, Co and the like, and then adjusts the pH value of the slurry. Patents CN103721722A and CN103157483A relate to Mo-Bi composite metal oxide catalysts prepared by the coprecipitation method. The catalyst prepared by this method is affected by many factors, such as the addition and precipitation sequence of metal ions, the adjustment of pH value, the calcination temperature and the like. The hydrothermal synthesis method is generally used for laboratory preparation, and the catalyst prepared has relatively complex phases, and the interphase synergistic effect exists, and the selectivity of the catalyst is good. The specific surface area of pure Mo-Bi catalyst is small, which is not conducive to the dispersion of various elements, and the selectivity of the product is low. Therefore, the Mo-Bi composite metal oxide needs to be further studied in the art. SUMMARY

[0005] The main purpose of the present application is to provide a large specific surface area multi-level pore Mo-Bi composite metal oxide catalyst and its preparation method and application, so as to overcome the defects of poor product selectivity of Mo-Bi composite metal oxide catalyst in the prior art.

[0006] In order to achieve the above purpose, the present application provides a multi-level pore Mo-Bi composite metal oxide catalyst, the general formula of which is Mo 12 Bi 1.5 Fe 1.5 Co5Ce x Gd y K 0.5 O / TiO2, wherein 0 12 Bi 1.5 Fe 1.5 Co5Ce x Gd y K 0.5 O.

[0007] The multi-level pore molybdenum-bismuth composite metal oxide catalyst, wherein the carrier accounts for 30-80% of the weight percentage of the catalyst.

[0008] To achieve the above object, the application further provides a preparation method of the multi-level pore molybdenum-bismuth composite metal oxide catalyst, comprising the following steps:

[0009] Step 1, preparation of a multi-level pore TiO2 carrier;

[0010] Step 2, preparation of a solution containing Mo precursor, Bi precursor, Fe precursor, Co precursor, Ce precursor, Gd precursor and K precursor;

[0011] Step 3, mixing the multi-level pore TiO2 carrier with the solution in step 2, adding a precipitant for deposition precipitation to obtain the multi-level pore molybdenum-bismuth composite metal oxide catalyst.

[0012] The preparation method of the multi-level pore molybdenum-bismuth composite metal oxide catalyst, wherein the preparation method of the multi-level pore TiO2 carrier comprises the following steps: uniformly mixing a mesopore template agent and a macropore template agent, adding a titanium precursor, and then aging, drying and calcining to obtain the multi-level pore TiO2 carrier.

[0013] The preparation method of the multi-level pore molybdenum-bismuth composite metal oxide catalyst, wherein the mesopore template agent is F127 and / or P123; and the macropore template agent is PS ball and / or PMMA ball.

[0014] The preparation method of the multi-level pore molybdenum-bismuth composite metal oxide catalyst, wherein the Mo precursor is ammonium molybdate and / or molybdenum trioxide; and the Bi precursor, Fe precursor, Co precursor, Ce precursor, Gd precursor and K precursor are nitrate or chloride of Bi, Fe, Co, Ce, Gd and K.

[0015] The preparation method of the multi-level pore molybdenum-bismuth composite metal oxide catalyst, wherein the precipitant is at least one of ammonia, urea and sodium hydroxide; and the addition amount of the precipitant is such that the pH value of the mixed solution is 5.0-7.0.

[0016] The preparation method of the multi-level pore molybdenum-bismuth composite metal oxide catalyst, wherein the preparation method of the multi-level pore TiO2 carrier comprises the following steps:

[0017] The mesopore template agent is dissolved in ethanol, hydrochloric acid and / or acetic acid is added and stirred; the macropore template agent is added and stirred, and then the titanium precursor is added, and then aging, drying and calcining are performed to obtain the multi-level pore TiO2 carrier.

[0018] The preparation method of the multi-level pore molybdenum bismuth composite metal oxide catalyst, wherein the dry method is rotary evaporation or / and oven drying.

[0019] To achieve the above-mentioned purpose, the application further provides application of the multi-level pore molybdenum bismuth composite metal oxide catalyst in the reaction of preparing methyl propyl aldehyde by selective oxidation of isobutene.

[0020] The application has the following beneficial effects:

[0021] The multi-level pore molybdenum bismuth composite metal oxide catalyst prepared by the application has a large specific surface area and contains at least two kinds of rare earth metals, promotes high dispersion of active components, and has a synergistic effect between the rare earth metals, thereby increasing the number of active oxygen species and improving the product selectivity of the catalyst. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The field emission scanning electron microscope (FESEM) (100 nm) of the mesoporous-macroporous TiO2 in Example 1 of the application.

[0023] Figure 2 The field emission scanning electron microscope (FESEM) (1 μm) of the mesoporous-macroporous TiO2 in Example 1 of the application. DETAILED DESCRIPTION

[0024] The technical solutions of the application are described in detail below, and the following embodiments are implemented on the premise of the technical solutions of the application, and a detailed implementation process is given, but the protection scope of the application is not limited to the following embodiments, and the structures or experimental methods not marked with specific conditions in the following embodiments are usually according to conventional conditions.

[0025] The application provides a multi-level pore molybdenum bismuth composite metal oxide catalyst, and the general formula of the multi-level pore molybdenum bismuth composite metal oxide catalyst is Mo 12 Bi 1.5 Fe 1.5 Co5Ce x Gd y K 0.5 O / TiO2, wherein 0 < x ≤ 1.2 and 0 < y ≤ 0.3. The catalyst comprises a carrier and a composite metal oxide, the composite metal oxide is dispersed in the carrier, the carrier is a multi-level pore TiO2, and the composite metal oxide is a composite oxide of molybdenum bismuth iron cobalt potassium and at least two kinds of rare earth metals.

[0026] The molybdenum-bismuth composite metal oxide catalyst has a multi-stage pore structure and contains at least two rare earth metals, the active components are highly dispersed due to the large specific surface area, and the amount of active oxygen species is increased due to the synergistic effect between the rare earth metals, thereby improving the product selectivity of the catalyst.

[0027] In an embodiment, the carrier of the present application accounts for 30% to 80% by weight of the catalyst, preferably 50% to 70%.

[0028] The carrier of the present application is TiO2, and the catalyst of the present application can be represented as: Mo 12 Bi 1.5 Fe 1.5 Co5Ce x Gd y K 0.5 O / TiO2, wherein 0 < x ≤ 1.2, preferably x = 0.2-0.8, 0 < y ≤ 0.3, preferably y = 0.1-0.2. In an embodiment, the TiO2 is a multi-stage pore TiO2.

[0029] In an embodiment, the preparation method of the multi-stage pore molybdenum-bismuth composite metal oxide catalyst of the present application comprises the following steps:

[0030] Step 1, preparation of a multi-stage pore TiO2 carrier;

[0031] Step 2, preparation of a solution containing Mo precursor, Bi precursor, Fe precursor, Co precursor, Ce precursor, Gd precursor, and K precursor;

[0032] Step 3, mixing the multi-stage pore TiO2 carrier with the solution described in step 2, adding a precipitant for deposition precipitation to obtain a multi-stage pore molybdenum-bismuth composite metal oxide catalyst.

[0033] In an embodiment, the preparation method of the multi-stage pore TiO2 comprises the following steps: dissolving a mesopore template agent in ethanol, adding hydrochloric acid and / or acetic acid, and stirring; adding a macropore template agent, stirring, and then adding a titanium precursor, aging, drying, and calcining to obtain a multi-stage pore TiO2 carrier.

[0034] In an embodiment, the mesopore template agent is F127 (acrylated polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer) or P123; and the macropore template agent is a PS ball or a PMMA ball.

[0035] In an embodiment, the titanium precursor is titanium isopropoxide, titanium tetrachloride, or tetrabutyl titanate.

[0036] In the preparation process of the multi-level pore TiO2, hydrochloric acid and acetic acid are added to prevent excessive hydrolysis of titanium precursors such as titanium isopropoxide. In an embodiment, in the preparation process of the multi-level pore TiO2 carrier, the aging temperature is 30-50℃, the aging time is 1-6 days, the drying temperature is 100-140℃, the drying time is 6-18 hours, and the calcination temperature is 350-600℃, and the calcination time is 1-10 hours.

[0037] In a specific embodiment, the preparation method of the multi-level pore TiO2 carrier of the present application is as follows:

[0038] The multi-level pore TiO2 is prepared by a soft template method. The mesoporous template agent is dissolved in ethanol, hydrochloric acid and acetic acid are added and stirred for 10 minutes; the macroporous template agent is added, stirred at room temperature for 6 hours, and then titanium isopropoxide is added and stirred at room temperature for another 3 hours. Aging is carried out at a certain temperature for 5 days, drying is carried out at 120℃ for 12 hours, and then calcination is carried out in air at a certain temperature for 4 hours, to obtain the mesoporous-macroporous TiO2 carrier.

[0039] In an embodiment, the Mo precursor is ammonium molybdate or molybdenum trioxide, and the Bi precursor, Fe precursor, Co precursor, Ce precursor, Gd precursor, and K precursor are nitrate or chloride of Bi, Fe, Co, Ce, Gd, and K. In another embodiment, step 1 of the present application is as follows: the Mo precursor is dissolved in water to obtain solution A; the Bi precursor, Fe precursor, Co precursor, Ce precursor, Gd precursor, and K precursor are dissolved in dilute nitric acid solution to obtain solution B; solution B is added to solution A and stirred, to obtain a composite metal oxide precursor slurry.

[0040] Step 3 is as follows: the multi-level pore TiO2 carrier is mixed with the solution obtained in step 2, a precipitant is added for deposition precipitation, to obtain a multi-level pore molybdenum-bismuth composite metal oxide catalyst.

[0041] In an embodiment, the TiO2 carrier is the multi-level pore TiO2 carrier prepared as described above, the multi-level pore TiO2 carrier is added to the solution obtained in step 2, and then a precipitant is added to adjust the pH value of the solution, for example, the pH value is 5.0-7.0, preferably 6.5, and then aging, drying, and calcination are carried out, and the multi-level pore molybdenum-bismuth composite metal oxide catalyst is obtained by tabletting.

[0042] The present application does not make special limitations on the precipitant, which is for example, ammonia, urea, and sodium hydroxide, etc. In an embodiment, in the preparation process of the multi-level pore molybdenum-bismuth composite metal oxide catalyst, the aging temperature is 30-50℃, the aging time is 10-60 minutes, the drying method is rotary evaporation or / and oven drying, the drying temperature is 100-140℃, the drying time is 6-24 hours, the calcination temperature is 400-500℃, preferably 450℃, and the calcination time is 1-10 hours.

[0043] The macroporous template PS ball and PMMA ball used in the application have regular spherical morphology, the specific surface area of the synthesized hierarchical pore titanium dioxide is high, 200m 2 ·g -1 The pore diameter is large, which is beneficial to the uniform dispersion of active components and mass transfer.

[0044] The hierarchical pore molybdenum-bismuth composite metal oxide catalyst is suitable for the reaction of preparing methyl propyl aldehyde by selective oxidation of isobutene, and can improve the selectivity of the target product methyl propyl aldehyde.

[0045] The hierarchical pore Mo-Bi composite metal oxide used in the application can utilize the large specific surface area and hierarchical pore structure of the material, on the one hand, the active species are better dispersed, which is beneficial to the rapid diffusion of reactants and products, and the synergistic effect between rare earth metals is more conducive to the regulation of active oxygen species, thereby improving the catalytic activity and selectivity; on the other hand, the hierarchical pore structure is easy to diffuse heat, avoids the formation of hot spots in the reaction bed, and the reaction process can be effectively controlled.

[0046] The technical solutions of the application will be described below through specific examples.

[0047] Raw materials or equipment sources:

[0048] F127 (Sigma), ethanol (Chengdu Kolon Chemicals Co., Ltd.), hydrochloric acid (Chengdu Kolon Chemicals Co., Ltd.), acetic acid (Chengdu Kolon Chemicals Co., Ltd.), titanium isopropoxide (Anjieji Chemical), nitric acid (Chengdu Kolon Chemicals Co., Ltd.), ammonium molybdate (Chengdu Kolon Chemicals Co., Ltd.), bismuth nitrate (Tianjin Chemical Reagent Factory No. 3), ferric nitrate (Xilong Chemical Co., Ltd.), cobalt nitrate (Xilong Science Co., Ltd.), potassium nitrate (Sichuan Xilong Chemical Co., Ltd.), cerium nitrate (Chengdu Kolon Chemicals Co., Ltd.), gadolinium nitrate (Aladdin Reagent), fixed bed micro-reaction evaluation device (Tianjin Pengxiang Technology Co., Ltd.), gas chromatograph (Shimadzu GC-2014C).

[0049] Evaluation and analysis method:

[0050] The selective oxidation reaction conditions of isobutene are 360-420℃, under normal pressure, the volume space velocity of the raw material gas relative to the catalyst is 9200h -1 , and the space velocity ratio of air to isobutene is 96:4.

[0051] In the reaction of the application, the definitions of conversion rate, selectivity and yield are as follows:

[0052] Isobutene conversion rate (%) = 100 x total carbon number of generated products / carbon number of supplied isobutene

[0053] MAL selectivity (%) = 100 × number of carbons in methacrolein formation / number of carbons in the supplied isobutylene

[0054] MAL yield (%) = Conversion rate (%) × Selectivity (%) / 100

[0055] In one embodiment of the present invention, the reaction product is methane as the associated gas, analyzed online by a gas chromatograph (Shimadzu GC-2014C). Gases such as methane, ethane, ethylene, and isobutylene are detected by an Al2O3 column, while CO is... x Products were detected using a TDX-01 column, while other products such as acetic acid, acetone, and methacrolein were detected using a DB-5 column. Relative correction factors for each organic product were calculated. Conversion and selectivity were calculated using carbon balance as the standard.

[0056] Example 1

[0057] 6g of F127 was dissolved in 75mL of ethanol and stirred at room temperature for 30min. Then, 6g of hydrochloric acid was added and stirred for 5min, followed by 6g of acetic acid and stirring for 5min. The mixture was then further heated to 40℃ and stirred for 2h. 15g of PS spheres were added and stirred at room temperature for 6h. Then, 8.5g of titanium isopropoxide was added and stirred at room temperature for 3h. The mixture was aged at 30℃ for 5 days. Finally, it was calcined in air at 450℃ for 4h to obtain mesoporous TiO2. N2 adsorption-desorption experiments showed that the specific surface area of ​​TiO2 was 268m². 2 ·g -1 The average pore size of macropores is 303 nm, and the average pore size of mesopores is 16 nm.

[0058] In a round-bottom flask, 10.59 g of (NH4)6MoO2 was added. 24 Solution A was prepared by dissolving 4H₂O in 80 mL of water at 50 °C and stirring for 30 min. Solution B was prepared by dissolving 3.64 g Bi(NO₃)₃·5H₂O, 3.03 g Fe(NO₃)₃·9H₂O, 7.28 g Co(NO₃)₂·6H₂O, 0.43 g Ce(NO₃)₃·6H₂O, 0.45 g Gd(NO₃)₃·6H₂O, and 0.25 g KNO₃ in 20 mL of 5 M HNO₃ + 20 mL H₂O solution and stirring at room temperature for 30 min. Solution B was then added dropwise to solution A at 50 °C, followed by the addition of 40 g mesoporous TiO₂. After stirring for 1 h, the pH was adjusted to 5.0 with ammonia, and the mixture was stirred for 30 min. The mixture was then rotary evaporated at 70 °C for 4 h, dried overnight at 120 °C, and calcined at 450 °C for 3 h to obtain a product containing 20 wt% Mo. 12 Bi 1.5 Fe 1.5 Co5Ce 0.2 Gd 0.2 K 0.5 A catalyst containing O and 80 wt% TiO2. For Mo12 Bi 1.5 Fe 1.5 Co5Ce 0.2 Gd 0. 2K 0.5 O / TiO2 powder was compressed into tablets, formed at 10 MPa, and sieved into 20-40 mesh particles for reaction evaluation.

[0059] Figure 1 , 2 This is a field emission scanning electron microscope (FESEM) image of mesopore-macropore TiO2 from Example 1. Figure 1 , 2 As shown, the TiO2 prepared in Example 1 has an ordered mesoporous-macroporous hierarchical pore structure.

[0060] Example 2

[0061] 6.5 g of P123 was dissolved in 75 mL of ethanol and stirred at room temperature for 30 min. Then, 7 g of hydrochloric acid was added and stirred for 5 min, followed by 5.5 g of acetic acid and stirring for 5 min. The mixture was then stirred at 60 °C for 2 h. 15 g of PMMA balls were added and stirred at room temperature for 6 h. Then, 8.5 g of titanium isopropoxide was added and stirred at room temperature for 3 h. The mixture was aged at 35 °C for 5 days. Finally, it was calcined in air at 350 °C for 4 h to obtain mesoporous TiO2. N2 adsorption-desorption experiments showed that the specific surface area of ​​TiO2 was 223 m² / g. 2 ·g -1 The average pore size of macropores is 289 nm, and the average pore size of mesopores is 14 nm.

[0062] In a round-bottom flask, 10.59 g of (NH4)6MoO2 was added. 24 Solution A was prepared by dissolving 4H₂O in 80 mL of water at 50 °C and stirring for 30 min. Solution B was prepared by dissolving 3.64 g Bi(NO₃)₃·5H₂O, 3.03 g Fe(NO₃)₃·9H₂O, 7.28 g Co(NO₃)₂·6H₂O, 2.60 g Ce(NO₃)₃·6H₂O, 0.23 g Gd(NO₃)₃·6H₂O, and 0.25 g KNO₃ in 20 mL of 5 M HNO₃ + 20 mL H₂O solution and stirring at room temperature for 30 min. Solution B was then added dropwise to solution A at 50 °C, followed by the addition of 10 g mesoporous TiO₂. After stirring for 1 h, the pH was adjusted to 6.0 with ammonia, and the mixture was stirred for 30 min. The mixture was then dried overnight at 120 °C and calcined at 400 °C for 3 h. A product containing 50 wt% Mo was obtained. 12 Bi 1. 5Fe 1.5 Co5Ce 1.2 Gd 0.1 K 0.5 A catalyst containing O and 50 wt% TiO2. For Mo...12 Bi 1.5 Fe 1.5 Co5Ce 1.2 Gd 0.1 K 0.5 O / TiO2powder was pressed into pellets, shaped at 10 MPa, sieved into 20-40 mesh particles for reaction evaluation.

[0063] Example 3

[0064] Take 6g F127, dissolved in 75ml ethanol, after stirring at room temperature for 30min, add 12g hydrochloric acid stirring for 10min, continue to rise to 40℃ stirring for 2h. Add 6g PS ball, stirring at room temperature for 6h, add 1.7g titanium isopropoxide, stirring at room temperature for 3h. Put in 40℃ aging for 5 days. In air 600℃ calcination for 4h to obtain meso-macroporous TiO2. By N2adsorption-desorption experiment can know the specific surface area of catalyst is 197m 2 ·g -1 , the average pore size of macropore is 278nm, the average pore size of mesopore is 15nm.

[0065] In a round bottom flask, 10.59g (NH4)6MoO 24 ·4H2O was dissolved in 80mL water at 50℃ stirring for 30min to prepare solution A. 3.64g Bi(NO3)3·5H2O, 3.03g Fe(NO3)3·9H2O, 7.28g Co(NO3)2·6H2O, 2.60g Ce(NO3)3·6H2O, 0.68g Gd(NO3)3·6H2O and 0.25g KNO3 were dissolved in 20mL 5M HNO3+20mL H2O solution, stirring at room temperature for 30min to obtain solution B. At 50℃, solution B was added dropwise to solution A, 4.2g meso-macroporous TiO2 was added, stirring for 1h, urea was used to adjust pH=7.0, stirring for 30min, rotary evaporation at 80℃ for 3h, drying at 120℃ overnight, calcination at 450℃ for 3h. A catalyst containing 70wt% Mo 12 Bi 1.5 Fe 1.5 Co5Ce 1.2 Gd 0.3 K 0.5 O and 30wt% TiO2 was obtained. Mo 12 Bi 1.5 Fe 1.5 Co5Ce 1.2 Gd 0. 3K 0.5 O / TiO2powder was pressed into pellets, shaped at 10 MPa, sieved into 20-40 mesh particles for reaction evaluation.

[0066] Example 4

[0067] 6g of F127 was dissolved in 75mL of ethanol and stirred at room temperature for 30min. Then, 6g of hydrochloric acid was added and stirred for 5min, followed by 6g of acetic acid and stirring for 5min. The mixture was then further heated to 40℃ and stirred for 2h. 15g of PS spheres were added and stirred at room temperature for 6h. Then, 8.5g of titanium isopropoxide was added and stirred at room temperature for 3h. The mixture was aged at 50℃ for 5 days. Finally, it was calcined in air at 450℃ for 4h to obtain mesoporous TiO2. N2 adsorption-desorption experiments showed that the catalyst had a specific surface area of ​​268m². 2 ·g -1 The average pore size of macropores is 303 nm, and the average pore size of mesopores is 16 nm.

[0068] In a round-bottom flask, 10.59 g of (NH4)6MoO2 was added. 24 Solution A was prepared by dissolving 4H₂O in 80 mL of water at 50 °C and stirring for 30 min. Solution B was prepared by dissolving 3.64 g Bi(NO₃)₃·5H₂O, 3.03 g Fe(NO₃)₃·9H₂O, 7.28 g Co(NO₃)₂·6H₂O, 0.87 g Ce(NO₃)₃·6H₂O, 0.45 g Gd(NO₃)₃·6H₂O, and 0.25 g KNO₃ in 20 mL of 5 M HNO₃ + 20 mL H₂O solution and stirring at room temperature for 30 min. Solution B was then added dropwise to solution A at 50 °C, followed by the addition of 20 g mesoporous TiO₂. After stirring for 1 h, the pH was adjusted to 5.0 with sodium hydroxide, and the mixture was stirred for 30 min. The mixture was then rotary evaporated at 70 °C for 4 h, dried overnight at 120 °C, and calcined at 450 °C for 3 h to obtain a product containing 33 wt% Mo. 12 Bi 1.5 Fe 1.5 Co5Ce 0.4 Gd 0.2 K 0.5 A catalyst containing O and 67 wt% TiO2. For Mo 12 Bi 1.5 Fe 1.5 Co5Ce 0. 4Gd 0.2 K 0.5 O / TiO2 powder was compressed into tablets, formed at 10 MPa, and sieved into 20-40 mesh particles for reaction evaluation.

[0069] Example 5

[0070] 6g of F127 was dissolved in 75mL of ethanol and stirred at room temperature for 30min. Then, 6g of hydrochloric acid was added and stirred for 5min, followed by 6g of acetic acid and stirring for 5min. The mixture was then stirred at 40℃ for 2h. 15g of PS spheres were added and stirred at room temperature for 6h. Then, 8.5g of titanium isopropoxide was added and stirred at room temperature for 3h. The mixture was aged at 30℃ for 5 days. Finally, it was calcined in air at 450℃ for 4h to obtain mesoporous TiO2. N2 adsorption-desorption experiments showed that the catalyst had a specific surface area of ​​268m². 2 ·g -1 The average pore size of macropores is 303 nm, and the average pore size of mesopores is 16 nm.

[0071] In a round-bottom flask, 10.59 g of (NH4)6MoO2 was added. 24 Solution A was prepared by dissolving 4H₂O in 80 mL of water at 50 °C and stirring for 30 min. Solution B was prepared by dissolving 3.64 g Bi(NO₃)₃·5H₂O, 3.03 g Fe(NO₃)₃·9H₂O, 7.28 g Co(NO₃)₂·6H₂O, 1.74 g Ce(NO₃)₃·6H₂O, 0.23 g Gd(NO₃)₃·6H₂O, and 0.25 g KNO₃ in 20 mL of 5 M HNO₃ + 20 mL H₂O solution and stirring at room temperature for 30 min. Solution B was then added dropwise to solution A at 50 °C, followed by the addition of 15 g mesoporous TiO₂. After stirring for 1 h, the pH was adjusted to 5.5 with ammonia, and the mixture was stirred for 30 min. The mixture was then rotary evaporated at 70 °C for 4 h, dried overnight at 120 °C, and calcined at 500 °C for 3 h to obtain a product containing 40 wt% Mo. 12 Bi 1.5 Fe 1.5 Co5Ce 0.8 Gd 0.1 K 0.5 A catalyst containing O and 60 wt% TiO2. For Mo... 12 Bi 1.5 Fe 1.5 Co5Ce 0.8 Gd 0. 1K 0.5 O / TiO2 powder was compressed into tablets, formed at 10 MPa, and sieved into 20-40 mesh particles for reaction evaluation.

[0072] Comparative Example 1

[0073] The catalyst Mo was prepared using the same preparation process as in Example 1, without the addition of Ce(NO3)3·6H2O. 12 Bi 1.5 Fe 1.5 Co5Gd 0.2 K 0.5 O / TiO2.

[0074] Comparative Example 2

[0075] The catalyst Mo was prepared using the same process as in Example 2, without the addition of Gd(NO3)3·6H2O. 12 Bi 1.5 Fe 1.5 Co5Ce 0.2 K 0.5 O / TiO2.

[0076] Comparative Example 3

[0077] The catalyst Mo was prepared using the same preparation process as in Comparative Example 1, but without the addition of Ce(NO3)3·6H2O, but with the addition of 0.90 g of Gd(NO3)3·6H2O. 12 Bi 1.5 Fe 1.5 Co5Gd 0.4 K 0.5 O / TiO2.

[0078] Comparative Example 4

[0079] The catalyst Mo was prepared using the same process as in Comparative Example 2, but without the addition of Gd(NO3)3·6H2O, but with the addition of 2.82 g of Ce(NO3)3·6H2O. 12 Bi 1.5 Fe 1.5 Co5Ce 1.3 K 0.5 O / TiO2.

[0080] Comparative Example 5

[0081] The catalyst Mo was prepared using the same preparation process as in Example 3, without the addition of Ce(NO3)3·6H2O and Gd(NO3)3·6H2O. 12 Bi 1.5 Fe 1.5 Co5K 0.5 O / TiO2.

[0082] Comparative Example 6

[0083] In a round-bottom flask, 10.59 g of (NH4)6MoO2 was added. 24• 4H2O was dissolved in 80 mL water at 50°C and stirred for 30 min to obtain solution A. 3.64 g Bi(NO3)3.5H2O, 3.03 g Fe(NO3)3.9H2O, 7.28 g Co(NO3)2.6H2O, 0.43 g Ce(NO3)3.6H2O, 0.45 g Gd(NO3)3.6H2O and 0.25 g KNO3 were dissolved in 20 mL 5M HNO3+20 mL H2O solution and stirred at room temperature for 30 min to obtain solution B. Solution B was added dropwise to solution A at 50°C, stirred for 1 h, adjusted to pH=5.5 with ammonia water, stirred for 30 min, dried at 120°C overnight, and calcined at 450°C for 3 h to obtain Mo 12 Bi 1.5 Fe 1.5 Co5Ce 0.2 Gd 0.2 K 0.5 O catalyst. The powder was tabletted, shaped at 10 MPa, and sieved into 20-40 mesh particles for reaction evaluation.

[0084] Comparative Example 7

[0085] Prepared using the same preparation procedure of Example 1, adding commercial TiO2 to the precipitation deposition process to obtain the catalyst.

[0086] The catalysts obtained in Examples 1-5 and Comparative Examples 1-7 above were used in the reaction of selective oxidation of isobutylene to prepare MAL. The specific evaluation process was as follows:

[0087] 3.0 g of quartz sand was placed in the lower layer of the reactor tube, 1 mL of the catalyst tabletted and shaped was mixed with 1 mL of quartz sand to pack the catalyst, and 3.0 g of quartz sand was placed on the upper layer of the catalyst. The reaction conditions were: temperature 360-420°C, normal pressure, volume hourly space velocity of the raw gas isobutylene relative to the catalyst 9200 h -1 , and the air to isobutylene space velocity ratio was 96:4. After the reactor temperature, gas flow rate, etc. were stable (1 h), the isobutylene conversion rate and MAL yield were determined by sampling and analysis, and the results are shown in Table 1.

[0088] Table 1

[0089]

[0090] As shown in Table 1, the catalysts obtained in Examples 1-5 and Comparative Examples 1-7 were used to catalyze the selective oxidation of isobutylene to prepare methyl propyl aldehyde, and the conversion rates were basically equivalent, but the catalysts of Examples 1-5 had higher selectivity for the target product.

[0091] Of course, the present application can have other various embodiments, and those skilled in the art can make various corresponding changes and modifications according to the present application without departing from the spirit and essence of the present application, and these corresponding changes and modifications shall all belong to the protection scope of the claims of the present application.

Claims

1. A method for preparing a multi-level porous molybdenum-bismuth composite metal oxide catalyst by a deposition-precipitation method, characterized by, The preparation method comprises the following steps: Step 1, preparing a mesoporous-macroporous TiO2 carrier; Step 2, preparing a solution containing Mo precursor, Bi precursor, Fe precursor, Co precursor, Ce precursor, Gd precursor and K precursor; Step 3, mixing the mesoporous-macroporous TiO2 carrier with the solution in step 2, adding a precipitant for deposition precipitation to obtain a multi-porous Mo-Bi composite metal oxide catalyst; The general formula of the multi-level pore molybdenum bismuth composite metal oxide catalyst is Mo 12 Bi 1.5 Fe 1.5 Co5Ce x Gd y K 0.5 O / TiO2, wherein 0 < x ≤ 1.2 and 0 < y ≤ 0.3; the multi-level pore molybdenum bismuth composite metal oxide catalyst comprises a carrier and a composite metal oxide, the composite metal oxide is dispersed in the carrier, the carrier is a mesoporous-macroporous TiO2 carrier, and the composite metal oxide is Mo 12 Bi 1.5 Fe 1.5 Co5Ce x Gd y K 0.5 O.

2. The method for preparing a multi-level porous bismuth molybdenum composite metal oxide catalyst according to claim 1, characterized by, The preparation method of the mesoporous-macroporous TiO2 carrier comprises the following steps: uniformly mixing a mesoporous template agent and a macroporous template agent, adding a titanium precursor, and then aging, drying and calcining to obtain a multi-porous TiO2 carrier.

3. The method of claim 2, wherein the method is characterized by, The mesoporous template agent is F127 and / or P123; and the macroporous template agent is PS ball and / or PMMA ball.

4. The method of claim 1, wherein the method is characterized by, The Mo precursor is ammonium molybdate and / or molybdenum trioxide, and the Bi precursor, Fe precursor, Co precursor, Ce precursor, Gd precursor and K precursor are nitrate or chloride of Bi, Fe, Co, Ce, Gd and K.

5. The method of claim 1, wherein the method is characterized by: The precipitant is at least one of ammonia, urea and sodium hydroxide, and the adding amount of the precipitant is such that the pH value of the mixed solution is 5.0-7.

0.

6. The method of claim 1, wherein the method is characterized by: The preparation method of the mesoporous-macroporous TiO2 carrier comprises the following steps: The mesoporous template agent is dissolved in ethanol, hydrochloric acid and / or acetic acid is added and stirred, the macroporous template agent is added and stirred, then the titanium precursor is added, and the mixture is aged, dried and calcined to obtain the multi-porous TiO2 carrier.

7. The method of claim 2, wherein the method is characterized by, The drying mode is rotary evaporation or / and oven drying.

8. The method of claim 1, wherein the method is characterized by: The weight percentage of the carrier in the catalyst is 30%-80%.

9. Application of the multi-porous Mo-Bi composite metal oxide catalyst prepared by the preparation method in any one of claims 1-8 in a reaction of selectively oxidizing isobutene to prepare methacrolein.

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