Modified carrier, composite metal oxide catalyst prepared from modified carrier and application of composite metal oxide catalyst

Abstract

The present invention discloses a modified carrier and a composite metal oxide catalyst prepared by using the modified carrier, and particularly relates to the technical field of catalyst preparation, the modified carrier comprises a carrier and a composite metal oxide impregnated and adsorbed on the carrier, the general formula of the composite metal oxide is Mo12VaAbBcCdDeEfFgOn, the carrier is selected from at least one of aluminum oxide, silicon dioxide, titanium dioxide, magnesium oxide, zirconium oxide, a silicon dioxide-aluminum oxide composite carrier, silicon carbide, silicon nitride, diatomite and zeolite, and the carrier is pretreated to improve the specific surface area and porosity of the carrier. By pretreating the carrier, reasonably selecting composite metal oxide elements and adopting various loading methods, the problems of insufficient activity, selectivity and stability of the existing catalyst, poor carrier performance and the like are solved, and the catalyst has the advantages of improving catalytic performance, optimizing reaction conditions and feed gas adaptability and facilitating product separation and purification.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation, and more specifically, to a modified carrier and a composite metal oxide catalyst prepared by using the modified carrier and application thereof. Background Art

[0002] In the modern chemical industry, catalysts play a vital role. They can accelerate the rate of chemical reactions, improve the selectivity of reactions, and reduce the activation energy of reactions, thus having a wide range of applications in many fields such as energy utilization, environmental protection, and material synthesis. For example, in the process of oil refining, catalysts can convert crude oil into a variety of valuable fuels and chemical raw materials; in the field of environmental protection, catalysts can be used to treat harmful pollutants in exhaust gas and convert them into harmless substances.

[0003] Composite metal oxide catalysts have become key catalysts for many chemical reactions due to their unique structure and properties. However, traditional composite metal oxide catalysts still have limitations in some aspects. For example, in the reaction of catalyzing the conversion of low-carbon olefins into unsaturated aldehydes and / or unsaturated carboxylic acids, existing catalysts may have problems such as insufficient activity, poor selectivity, and poor stability.

[0004] In the acrylic acid production process, the catalyst used may be easily deactivated under high temperature, high pressure and other reaction conditions, resulting in unstable acrylic acid yield and quality. At the same time, there are also certain challenges in the adaptability of various components in the raw gas and the precise control of reaction conditions.

[0005] As an important component of the catalyst, the carrier not only supports the active components, but also affects the activity, selectivity and stability of the catalyst. For example, the specific surface area, porosity, surface activity and other properties of the carrier will directly affect the dispersion and adsorption capacity of the active components on its surface.

[0006] Existing carriers have deficiencies in some aspects, such as small specific surface area, which leads to uneven dispersion of active components and affects the catalytic effect; inappropriate porosity may limit the diffusion of reactants and products and reduce reaction efficiency; low surface activity is not conducive to the adsorption and fixation of active components, thus affecting the overall performance of the catalyst.

[0007] Therefore, a modified carrier and a composite metal oxide catalyst prepared using the modified carrier and applications thereof are proposed. Summary of the invention

[0008] In order to overcome the above-mentioned defects of the prior art, the present invention provides a modified carrier and a composite metal oxide catalyst prepared by using the modified carrier and applications thereof, so as to solve the problems raised in the above-mentioned background technology.

[0009] To achieve the above object, the present invention provides the following technical solution: a modified carrier, comprising a carrier and a composite metal oxide impregnated and adsorbed on the carrier, wherein the general formula of the composite metal oxide is: Mo 12 V a A b B c C d D e E f F g O n (I), in which: A is selected from at least one of W, Nb, Ta, Cr, Ce, P, Te, Pb, As, and Zn; B is at least one selected from Cu, Ni, Co, Fe, Mn, Zn and lanthanide elements; C is selected from at least one of Sb, Te and Bi; D, E, and F are independently selected from at least one of Group IA, Group IIA, Group IIIA, Group IVB-VIB, and Group VIB elements except the selected elements in A and B; The value range of a is 2 to 4; The value range of b is 0.4 to 2; The value range of c is 1 to 5; The value range of d is 0.2 to 1.5; The value range of e is 0.1~0.8; The value range of f is 0.2 to 1; The value range of g is 1 to 5; n is the total number of oxygen atoms required to satisfy the valence of other elements.

[0010] The carrier is selected from at least one of alumina, silica, titania, magnesia, zirconia, a silica-alumina composite carrier, silicon carbide, silicon nitride, diatomaceous earth, and zeolite, and the carrier is pretreated to increase its specific surface area and porosity; Based on the total mass of the carrier, the loading rate of the composite metal oxide is 1 to 25%, preferably 5 to 20%.

[0011] Preferably, the pretreatment includes at least one of acid washing, alkali washing, heat treatment or plasma treatment of the carrier surface to improve its surface activity and adsorption capacity for the composite metal oxide.

[0012] Preferably, the composite metal oxide is loaded on the carrier by at least one of a wet chemical method, a sol-gel method, an impregnation method, a co-precipitation method or a vapor deposition method.

[0013] A composite metal oxide catalyst comprises the modified carrier described above, and a composite metal oxide having the general formula shown in formula (I) supported on the modified carrier.

[0014] A method for preparing a composite metal oxide catalyst is used to prepare the composite metal oxide catalyst described above, and the preparation method comprises: a) dissolving a compound containing the elements Mo, V, A, B, C, D, E, and F in a solvent to form a mixed solution, wherein the compounds of each element in the mixed solution interact with the surface of the support in subsequent steps and react chemically during drying and calcining to form a composite metal oxide; b) immersing the pretreated modified support in the mixed solution for adsorption, at which time the composite metal oxide precursor begins to be adsorbed on the surface of the support and undergoes a preliminary reaction; c) drying the modified carrier after adsorption to remove the solvent and promote further conversion of the composite metal oxide precursor on the carrier surface; d) calcining the dried support to form a composite metal oxide catalyst. During the calcination process, complex chemical reactions occur between the elements to form a stable structure having the general formula shown in formula (I).

[0015] Preferably, the calcination temperature in step d) is 300-500° C., and the calcination time is 1-10 hours, preferably 350-450° C., and the calcination time is 2-8 hours.

[0016] Preferably, the composite metal oxide catalyst prepared by the preparation method is used in converting low-carbon olefins into unsaturated aldehydes and / or unsaturated carboxylic acids by subjecting low-carbon olefins to a gas-phase catalytic oxidation reaction with oxygen molecules or a gas containing oxygen molecules to generate unsaturated aldehydes and / or unsaturated carboxylic acids.

[0017] A method for producing acrylic acid, using the composite metal oxide catalyst prepared by the preparation method to catalytically oxidize acrolein to produce acrylic acid, the catalytic oxidation reaction is carried out in a fixed bed reactor, the ratio of acrolein, oxygen, water vapor and inert gas in the raw gas is 1-15% acrolein, 3-20% oxygen, 0-20% water vapor, and the balance is inert gas.

[0018] Preferably, the conditions of the catalytic oxidation reaction include: reaction temperature of 230-280°C, reaction pressure of 0.01-0.2 MPa, and space velocity of 500-1700 h -1 , the inner diameter of the reaction tube is 25-30 mm, and the length of the reaction tube is 3500 mm. Preferably, the method further comprises separating and purifying the reaction product to obtain a high-purity acrylic acid product.

[0019] The modified carrier provided by the present invention, the composite metal oxide catalyst prepared using the modified carrier, and the application thereof have the following beneficial effects: 1. Pretreatment of the carrier (such as acid washing, alkali washing, heat treatment or plasma treatment, etc.) can effectively increase the specific surface area and porosity of the carrier. A larger specific surface area can make the composite metal oxide more evenly dispersed on the carrier surface, increase the number of active sites, and thus improve the activity of the catalyst. Appropriate porosity is conducive to the diffusion of reactants and products, and improves the reaction rate and selectivity.

[0020] 2. The surface activity of the pretreated carrier is enhanced, and the adsorption capacity of the composite metal oxide is also improved accordingly. This enables the composite metal oxide to be better fixed on the carrier, reducing the loss during the reaction process, improving the stability of the catalyst, and also helps to improve the interaction between the active components and the reactants, further improving the catalytic effect.

[0021] 3. The general formula of composite metal oxides includes a variety of elements. By rationally selecting different combinations of elements, the electronic structure and chemical properties of the catalyst can be optimized, thereby improving the activity and selectivity of the catalyst. For example, the addition of certain elements can adjust the redox properties of the catalyst, making it more suitable for a specific reaction.

[0022] 4. Composite metal oxides can be loaded on the carrier by various methods such as wet chemical method, sol-gel method, impregnation method, co-precipitation method or vapor deposition method. This diversity provides more choices and flexibility for the preparation of catalysts. The most appropriate loading method can be selected according to actual needs and conditions to obtain the catalyst with the best performance.

[0023] 5. In the application of converting low-carbon olefins into unsaturated aldehydes and / or unsaturated carboxylic acids, as well as in the production of acrylic acid, the composite metal oxide catalyst exhibits good catalytic performance. It has high activity and can achieve efficient conversion under relatively mild reaction conditions; it has good selectivity and can give priority to the production of target products and reduce the generation of by-products; it has high stability and can maintain good catalytic effects during long-term reactions, reduce the frequency of catalyst replacement, and improve production efficiency and economic benefits.

[0024] 6. In the process of producing acrylic acid, the catalyst has a wide adaptability range to the proportion of each component in the raw gas (acrolein, oxygen, water vapor and inert gas). At the same time, through the precise control of the reaction conditions (temperature, pressure, space velocity, etc.), the yield and quality of acrylic acid can be further improved to meet the needs of industrial production.

[0025] 7. Since the catalyst has high selectivity, fewer by-products are generated during the reaction, which makes it easier to separate and purify the reaction products, and high-purity acrylic acid products can be obtained, thereby improving product quality and market competitiveness. DETAILED DESCRIPTION

[0026] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0027] In the examples given below, the calculation methods for acrolein conversion, acrylic acid yield and selectivity are as follows: Acrolein conversion rate (%) = (number of moles of acrolein reacted / number of moles of acrolein in the raw material) × 100% Acrylic acid yield (%) = (moles of acrylic acid produced / moles of acrolein in the raw material) × 100% Selectivity of acrylic acid (%) = (moles of acrylic acid produced / moles of acrolein reacted) × 100% The present invention will be further described below by way of examples. Example 1

[0028] Preparation of modified carrier Alumina was selected as the carrier, 1500 g of alumina was weighed and subjected to acid washing pretreatment.

[0029] According to the general formula of composite metal oxide Mo 12 V a A b B c C d D e E f F g O n (Ⅰ), where A selects W, B selects Cu, C selects Sb, D selects Na, E selects Ca, F selects Si, a=3, b=1, c=2, d=0.5, e=0.3, f=0.2, g=1.

[0030] Preparation of composite metal oxide slurry: Weigh 81.53g of molybdenum trioxide, 12.88g of vanadium pentoxide, 13.4g of ammonium paratungstate, 7.51g of copper oxide, 0.44g of sodium oxide, 1.55g of calcium nitrate, 3.44g of antimony trioxide, and 2.84g of silicon dioxide in sequence and add them into 300ml of deionized water, and prepare slurry by coprecipitation method.

[0031] The acid-washed alumina support was immersed in the slurry for 24 hours.

[0032] After impregnation, the substrate was dried at 120°C for 12 hours and then calcined at 450°C for 4 hours to obtain a modified support.

[0033] Preparation of composite metal oxide catalysts In 1000 ml of deionized water, add at once: appropriate amount of concentrated nitric acid, 260.9 g of molybdenum trioxide, 41.2 g of vanadium pentoxide, 42.88 g of ammonium paratungstate, 24.03 g of copper oxide, 1.4 g of sodium oxide, 4.96 g of calcium nitrate, 11.01 g of antimony trioxide, and 9.07 g of silicon dioxide to form a mixed solution, and immerse the above-mentioned modified carrier in the mixed solution for adsorption for 12 hours. The adsorbed carrier is evaporated to dryness at 120°C and dried in an oven for 10 hours, and then calcined at 380°C for 6 hours to obtain a composite metal oxide catalyst.

[0034] Acrylic acid production application In a fixed bed reactor, the composite metal oxide catalyst is used to catalytically oxidize acrolein to produce acrylic acid. The acrolein content in the raw gas is 10%, the oxygen content is 15%, the water vapor content is 5%, and the balance is nitrogen. The reaction temperature is 250°C, the reaction pressure is 0.1Mpa, and the space velocity is 1700h -1 . Example 2

[0035] Preparation of modified carrier Silica was selected as the carrier, 1500 g of silica was weighed, and alkali washing and heat treatment pretreatment were performed.

[0036] According to the general formula of composite metal oxide Mo 12 V a A b B c C d D e E f F g O n (Ⅰ), where A selects Nb, B selects Ni, C selects Te, D selects K, E selects Mg, F selects Al, a=2, b=1.5, c=3, d=0.8, e=0.5, f=0.4, g=2.

[0037] Preparation of composite metal oxide slurry: 81.53 g of molybdenum trioxide, 8.58 g of vanadium pentoxide, 41.2 g of nickel nitrate, 2.8 g of magnesium nitrate, 9.4 g of niobium pentoxide, 6 g of tellurium dioxide, and 4.82 g of aluminum oxide were weighed and added to 80 ml of ethanol in sequence to prepare a slurry by a sol-gel method. The pretreated silica carrier was impregnated in the slurry for 24 hours.

[0038] After impregnation, the substrate was dried at 120°C for 12 hours and then calcined at 420°C for 3 hours to obtain a modified support.

[0039] Preparation of composite metal oxide catalysts Weigh 100g of ammonium paramolybdate and 11.04g of ammonium metavanadate, add 260.9g of molybdenum trioxide, 27.5g of vanadium pentoxide, 131.77g of nickel nitrate, 8.96g of magnesium nitrate, 30.11g of niobium pentoxide, 19.28g of tellurium dioxide and 15.4g of aluminum oxide into 1000ml of deionized water at once to form a mixed solution, immerse the above-mentioned modified carrier in the mixed solution for adsorption for 18 hours, evaporate the slurry of the adsorbed carrier at 120°C and dry it in an oven for 12 hours, and then calcine at 360°C for 4 hours to obtain a composite metal oxide catalyst.

[0040] Acrylic acid production application In a fixed bed reactor, the composite metal oxide catalyst is used to catalytically oxidize acrolein to produce acrylic acid. The acrolein content in the raw gas is 12%, the oxygen content is 18%, the water vapor content is 8%, and the balance is nitrogen. The reaction temperature is 280°C, the reaction pressure is 0.1 MPa, and the space velocity is 1700 h -1 . Example 3

[0041] Preparation of modified carrier A titanium dioxide-alumina composite carrier was selected, and 1500 g of the titanium dioxide-alumina composite carrier (in which titanium dioxide and alumina each accounted for 50%) was weighed and pre-treated with plasma.

[0042] According to the general formula of composite metal oxide Mo 12 V a A b B c C d D e E f F g O n (Ⅰ), where A selects Ta, B selects Co, C selects Bi, D selects Li, E selects Ba, and F selects Ti, a=4, b=0.8, c=4, d=0.3, e=0.2, f=0.6, and g=3.

[0043] Preparation of composite metal oxide slurry: In 300 ml of deionized water, appropriate amount of concentrated nitric acid, 81.53 g of molybdenum trioxide, 17.2 g of vanadium pentoxide, 54.95 g of cobalt nitrate, 5.59 g of bismuth nitrate, 7.4 g of barium nitrate, 0.35 g of lithium carbonate, 8.34 g of tantalum pentoxide, and 11.31 g of titanium dioxide were added in sequence to prepare slurry by impregnation method. The pretreated composite support was impregnated in the slurry for 24 hours.

[0044] After impregnation, the substrate was dried at 120°C for 12 hours and then calcined at 400°C for 5 hours to obtain a modified support.

[0045] Preparation of composite metal oxide catalysts In 1000 ml of deionized water, add at once: appropriate amount of concentrated nitric acid, 260.9 g of molybdenum trioxide, 54.94 g of vanadium pentoxide, 175.83 g of cobalt nitrate, 17.9 g of bismuth nitrate, 23.68 g of barium nitrate, 1.11 g of lithium carbonate, 26.7 g of tantalum pentoxide, and 36.2 g of titanium dioxide to form a mixed solution, and immerse the above-mentioned modified carrier in the mixed solution to form adsorption for 24 hours. The adsorbed carrier is evaporated to dryness at 120° C. and dried in an oven for 12 hours, and then calcined at 380° C. for 6 hours to obtain a composite metal oxide catalyst.

[0046] Acrylic acid production application In a fixed bed reactor, the composite metal oxide catalyst is used to catalytically oxidize acrolein to produce acrylic acid. The acrolein content in the raw gas is 8%, the oxygen content is 20%, the water vapor content is 3%, and the balance is nitrogen. The reaction temperature is 240°C, the reaction pressure is 0.1 MPa, and the space velocity is 1700 h -1 .

[0047] Comparative Example 1 Preparation of modified carrier Alumina without pretreatment was selected as the carrier, and 1500 g of alumina was weighed.

[0048] According to the general formula of composite metal oxide Mo 12 V a A b B c C d D e E f F g O n (Ⅰ), where A selects W, B selects Cu, C selects Sb, D selects Na, E selects Ca, F selects Si, a=3, b=1, c=2, d=0.5, e=0.3, f=0.2, g=1.

[0049] Preparation of composite metal oxide slurry: Add appropriate amount of concentrated nitric acid, 81.53g of molybdenum trioxide, 12.88g of vanadium pentoxide, 13.4g of ammonium paratungstate, 7.51g of copper oxide, 0.44g of sodium oxide, 1.55g of calcium nitrate, 3.44g of antimony trioxide, and 2.84g of silicon dioxide in 300ml of deionized water in sequence, and prepare the slurry by coprecipitation method.

[0050] The alumina support was immersed in the slurry for 24 hours.

[0051] After impregnation, the substrate was dried at 120°C for 12 hours and then calcined at 450°C for 4 hours to obtain a modified support.

[0052] Preparation of composite metal oxide catalysts In 1000 ml of deionized water, add in sequence: appropriate amount of concentrated nitric acid, 260.9 g of molybdenum trioxide, 41.2 g of vanadium pentoxide, 42.88 g of ammonium paratungstate, 24.03 g of copper oxide, 1.4 g of sodium oxide, 4.96 g of calcium nitrate, 11.01 g of antimony trioxide, and 9.07 g of silicon dioxide to form a mixed solution, and immerse the above-mentioned modified carrier in the mixed solution for adsorption for 12 hours. The adsorbed carrier is evaporated to dryness at 120°C and dried in an oven for 12 hours, and then calcined at 380°C for 6 hours to obtain a composite metal oxide catalyst.

[0053] Acrylic acid production application In a fixed bed reactor, the composite metal oxide catalyst is used to catalytically oxidize acrolein to produce acrylic acid. The feed gas contains 10% acrolein, 15% oxygen, a trace amount of water vapor (assumed to be 0.1%), and the remainder is nitrogen. The reaction temperature is 250°C, the reaction pressure is 0.1 MPa, and the space velocity is 1700 h -1 .

[0054] Comparative Example 2 Preparation of modified carrier Silica was selected as the carrier, 1500 g of silica was weighed, and alkali washing pretreatment was performed.

[0055] According to the general formula of composite metal oxide Mo 12 V a A b B c C d D e E f F g O n (Ⅰ), where A selects Nb, B selects Ni, C selects Te, D selects K, E selects Mg, F selects Al, a=2, b=1.5, c=3, d=0.8, e=0.5, f=0.4, g=2.

[0056] Preparation of composite metal oxide slurry: Weigh 81.53g of molybdenum trioxide, 8.58g of vanadium pentoxide, 41.18g of nickel nitrate, 2.39g of potassium nitrate, 2.8g of magnesium nitrate, 9.4g of niobium pentoxide, 6.03g of tellurium dioxide, and 4.81g of aluminum oxide, add appropriate amounts into 800ml of ethanol in sequence, and prepare a slurry by a sol-gel method.

[0057] The alkali-washed silica support was immersed in the slurry for 24 hours.

[0058] After impregnation, the substrate was dried at 120°C for 12 hours and then calcined at 420°C for 3 hours to obtain a modified support.

[0059] Preparation of composite metal oxide catalysts In 1000 ml of deionized water, add: 260.9 g of molybdenum trioxide, 27.5 g of vanadium pentoxide, 131.77 g of nickel nitrate, 7.64 g of potassium nitrate, 8.96 g of magnesium nitrate, 30.11 g of niobium pentoxide, 19.28 g of tellurium dioxide, and 15.4 g of aluminum oxide at once to form a mixed solution, and immerse the above-mentioned modified carrier in the mixed solution for adsorption for 12 hours. The adsorbed carrier is evaporated to dryness at 120°C and dried in an oven for 12 hours, and then calcined at 360°C for 8 hours to obtain a composite metal oxide catalyst.

[0060] Acrylic acid production application In a fixed bed reactor, the composite metal oxide catalyst is used to catalytically oxidize acrolein to produce acrylic acid. The acrolein content in the raw gas is 12%, the oxygen content is 18%, the water vapor content is 8%, and the balance is nitrogen. The reaction temperature is 250°C, the reaction pressure is 0.1 MPa, and the space velocity is 1700 h -1 .

[0061] Comparative Example 3 Preparation of modified carrier A titanium dioxide-alumina composite carrier was selected, and 1500 g of the titanium dioxide-alumina composite carrier (in which titanium dioxide and alumina each accounted for 50%) was weighed without pretreatment.

[0062] According to the general formula of composite metal oxide Mo 12 V a A b B c C d D e E f F g O n(Ⅰ), where A selects Ta, B selects Co, C selects Bi, D selects Li, E selects Ba, and F selects Ti, a=4, b=0.8, c=4, d=0.3, e=0.2, f=0.6, and g=3.

[0063] Preparation of composite metal oxide slurry: In 300 ml of deionized water, appropriate amounts of concentrated nitric acid, 81.53 g of molybdenum trioxide, 17.2 g of vanadium pentoxide, 54.95 g of cobalt nitrate, 5.59 g of bismuth nitrate, 7.4 g of barium nitrate, 0.35 g of lithium carbonate, 8.34 g of tantalum pentoxide, and 11.31 g of titanium dioxide were added in sequence to prepare a slurry by impregnation.

[0064] The pretreated composite support was immersed in the slurry for 24 hours.

[0065] After impregnation, the substrate was dried at 120°C for 12 hours and then calcined at 400°C for 5 hours to obtain a modified support.

[0066] Preparation of composite metal oxide catalysts In 1000 ml of deionized water, the following were added in sequence: appropriate amount of concentrated nitric acid, 260.9 g of molybdenum trioxide, 54.94 g of vanadium pentoxide, 175.83 g of cobalt nitrate, 17.9 g of bismuth nitrate, 23.68 g of barium nitrate, 1.11 g of lithium carbonate, 26.7 g of tantalum pentoxide, and 36.2 g of titanium dioxide to form a mixed solution. The modified carrier was immersed in the mixed solution to form adsorption for 24 hours. The adsorbed carrier was evaporated to dryness at 120° C. and dried in an oven for 12 hours, and then calcined at 380° C. for 6 hours to obtain a composite metal oxide catalyst.

[0067] Acrylic acid production application The composite metal oxide catalyst is used in a fixed bed reactor to catalyze the oxidation of acrolein to produce acrylic acid. The acrolein content in the raw gas is 8%, the oxygen content is 20%, the water vapor content is 3%, and the balance is nitrogen. The reaction temperature is 250°C, the reaction pressure is 0.1 MPa, and the space velocity is 1700 h -1 .

[0068] Experimental example The catalysts prepared in Examples 1-3 and Comparative Examples 1-3 were evaluated under different conditions. The evaluation results are shown in Table 1.

[0069] Table 1 Evaluation results of examples and comparative examples project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Carrier pretreatment method Pickling Alkaline washing + heat treatment Plasma treatment none Alkaline washing none Composite metal oxide carrier modification method Coprecipitation Sol-Gel Method Dipping method Coprecipitation Sol-Gel Method Dipping method Acrylic acid yield (%) 96.5 94.6 93.8 92.2 91.2 90.3 Acrylic acid selectivity (%) 97.5 96.5 95.2 95 95 95.2 Catalyst stability (h) 1000 1200 900 600 800 700 From the evaluation results table we can see that: The pretreated carrier is superior to the unpretreated carrier in terms of acrylic acid yield, selectivity and catalyst stability (Comparative Example 1). Different pretreatment methods also have a certain impact on the results. For example, the combination of alkali washing and heat treatment in Example 2 performs better in terms of acrylic acid yield and catalyst stability; Different loading methods have some influence on the results, but the difference is relatively small. For example, Example 1 uses the coprecipitation method for loading, and Example 2 uses the sol-gel method for loading. The acrylic acid yield of Example 2 is slightly higher than that of Example 1, but the difference in selectivity and stability is not significant; Therefore, it can be seen that the examples as a whole are superior to the comparative examples in terms of acrylic acid yield, selectivity and catalyst stability, indicating that the preparation method and application of the modified carrier and composite metal oxide catalyst of the present invention have better application effects.

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A modified carrier, characterized in that: It includes a carrier and a composite metal oxide impregnated and adsorbed on the carrier, and the general formula of the composite metal oxide is: Mo 12 V a A b B c C d D e E f F g O n (Ⅰ), among which: A is selected from at least one of W, Nb, Ta, Cr, Ce, P, Te, Pb, As, and Zn; B is at least one selected from Cu, Ni, Co, Fe, Mn, Zn and lanthanide elements; C is selected from at least one of Sb, Te and Bi; D, E, and F are independently selected from at least one of Group IA, Group IIA, Group IIIA, Group IVB-VIB, and Group VIB elements except the selected elements in A and B; The value range of a is 2 to 4; The value range of b is 0.4 to 2; The value range of c is 1 to 5; The value range of d is 0.2 to 1.5; The value range of e is 0.1~0.8; The value range of f is 0.2 to 1; The value range of g is 1 to 5; n is the total number of oxygen atoms required to satisfy the valence of other elements; The carrier is selected from at least one of alumina, silica, titania, magnesia, zirconia, a silica-alumina composite carrier, silicon carbide, silicon nitride, diatomaceous earth, and zeolite, and the carrier is pretreated to increase its specific surface area and porosity; Based on the total mass of the carrier, the loading rate of the composite metal oxide is 1 to 25%.

2. The modified carrier according to claim 1, characterized in that The pretreatment includes at least one of acid washing, alkali washing, heat treatment or plasma treatment of the carrier surface to improve its surface activity and adsorption capacity for composite metal oxides.

3. The modified carrier according to claim 2, characterized in that The composite metal oxide is loaded on the carrier by at least one method selected from the group consisting of a wet chemical method, a sol-gel method, an impregnation method, a coprecipitation method, and a vapor deposition method.

4. A composite metal oxide catalyst, characterized in that It comprises the modified carrier as claimed in claim 3, and a composite metal oxide having the general formula shown in formula (I) loaded on the modified carrier.

5. A method for preparing a composite metal oxide catalyst, for preparing the composite metal oxide catalyst according to claim 4, characterized in that: The preparation method comprises: a) dissolving a compound containing the elements Mo, V, A, B, C, D, E, and F in a solvent to form a mixed solution, wherein the compounds of each element in the mixed solution interact with the surface of the support in subsequent steps and react chemically during drying and calcining to form a composite metal oxide; b) immersing the pretreated modified support in the mixed solution for adsorption, at which time the composite metal oxide precursor begins to be adsorbed on the surface of the support and undergoes a preliminary reaction; c) drying the modified carrier after adsorption to remove the solvent and promote further conversion of the composite metal oxide precursor on the carrier surface; d) calcining the dried support to form a composite metal oxide catalyst. During the calcination process, complex chemical reactions occur between the elements to form a stable structure having the general formula shown in formula (I).

6. The method for preparing a composite metal oxide catalyst according to claim 5, characterized in that: The calcination temperature in step d) is 300-500° C. and the calcination time is 1-10 hours.

7. Use of the composite metal oxide catalyst prepared by the preparation method according to claim 6 in converting low-carbon olefins into unsaturated aldehydes and / or unsaturated carboxylic acids, characterized in that: The unsaturated aldehyde and / or unsaturated carboxylic acid are generated by subjecting low-carbon olefins to a gas-phase catalytic oxidation reaction with oxygen molecules or a gas containing oxygen molecules.

8. A method for producing acrylic acid, characterized in that: The composite metal oxide catalyst prepared by the preparation method of claim 6 is used to catalyze the oxidation of acrolein to produce acrylic acid. The catalytic oxidation reaction is carried out in a fixed bed reactor. The ratio of acrolein, oxygen, water vapor and inert gas in the raw gas is 1-15% acrolein, 3-20% oxygen, 0-20% water vapor, and the balance is inert gas.

9. The method for producing acrylic acid according to claim 8, characterized in that The conditions of the catalytic oxidation reaction include: reaction temperature of 230-280°C, reaction pressure of 0.01-0.2 MPa, and space velocity of 500-1700 h -1 The inner diameter of the reaction tube is 25-30 mm, and the length of the reaction tube is 3500 mm.

10. The method for producing acrylic acid according to claim 9, characterized in that The method further comprises the steps of separating and purifying the reaction product.