Supported heteropolyacid catalyst, synthesis thereof and method for preparing acrylic acid by using supported heteropolyacid catalyst

Abstract

The invention discloses a supported heteropolyacid catalyst, a synthesis method thereof and a method for preparing acrylic acid by using the supported heteropolyacid catalyst, and particularly relates to a method for preparing a catalyst by introducing other metals into the vacancy of Keggin type heteropolyacid and preparing acrylic acid (ester) by using the catalyst in aldol condensation reaction to catalyze a formaldehyde and acetic acid mixed solution (or a mixed aqueous solution). The introduced metals comprise one or more of Fe, Cs, La, Si, Zn, P, V, Ti, Ba and Ce, different metal substituted heteropolyacid with a Keggin structure is synthesized by adopting a step-by-step acidification-step feeding method, and then the heteropolyacid is loaded on a carrier for preparing acrylic acid. The catalyst provided by the invention has the advantages of bifunctional active center, strong activity, good selectivity and the like.

Description

Technical Field

[0001] The present invention relates to a supported heteropolyacid catalyst and its synthesis and method for preparing acrylic acid, and specifically relates to the preparation of a catalyst in which other metals are introduced at the vacant sites of a Keggin-type heteropolyacid, and the use of the catalyst in the aldol condensation reaction to catalyze the preparation of acrylic acid (ester) from a mixed solution of formaldehyde and acetic acid (or a mixed aqueous solution). Background Art

[0002] Acrylic acid is the simplest unsaturated carboxylic acid, with strong polymerization ability and esterification ability, and is widely used in industries such as building materials, automobiles, and medical and health. The industrial process for producing acrylic acid is mainly the propylene oxidation method. At present, with the depletion of petroleum resources and the oversupply of acetic acid and formaldehyde production, the reaction of preparing acrylic acid by aldol condensation of acetic acid and formaldehyde has gradually attracted people's attention. This non-petroleum route for synthesizing acrylic acid products from coal chemical industry has great potential application value.

[0003] From the reaction mechanism, it can be seen that the catalysts used in aldol condensation reactions can be roughly divided into three categories: acidic catalysts, basic catalysts, and acid-base bifunctional catalysts. Common acidic catalysts include niobic acid (Nb2O5·nH2O), MFI zeolite, (VO)2P2O7, α-VOHPO4, and some metal phosphate oxides studied by US Patent No. 4,677,225 and Ai (Journal of Catalysis, 1987, 107: 201-208), etc. These acidic catalysts have certain effects on the catalytic performance due to differences in surface acidity types, spatial distributions, and acid contents. Common basic catalysts are supported catalysts, with active components selected from metal ions such as Na, K, Rb, Mg, Ca, Sr, Cs, etc., which are supported on carriers such as SiO2, ZrO2, and synthetic zeolites (such as Ind. Eng. Chem. Prod. Res. Dev. 1966, 5: 50., Chemical Engineering, 2010, 38(5): 83-86., Journal of Natural Science of Heilongjiang University, 2011, 28(2): 213-217., Refining and Chemical Industry, 2009, 2: 17-19., etc.). Common acid-base bifunctional catalysts include NiO-P2O5, Mn2O5-P2O5, Fe2O3-P2O5, Ni-P, Mn-P, Fe-P, and hydrotalcite (such as Applied Catalysis A: General, 1999, 178: 145-157., Journal of Catalysis, 1987, 107(1): 201-208., Applied Catalysis A General, 2003, 252(1): 185-191., Journal of Industrial and Engineering Chemistry, 2016, 40: 145-151., Catalysis Today, 2018, 316: 122-128., etc.). However, water is inevitably produced in aldol condensation reactions, which easily causes hydrolysis of raw materials and products and deactivation of the catalyst, resulting in problems such as low catalyst activity and poor selectivity. Although some studies have proposed modifying the carrier or adding a small amount of water-resistant additives to improve the water resistance of the catalyst, the effect is not very obvious, so it has been difficult to be industrially promoted and utilized. Summary of the Invention

[0004] The main technical problem to be solved by the present invention is to provide a method for preparing a catalyst for aldol condensation reaction by introducing other metals at the vacant sites of Keggin-type heteropolyacids and using the catalyst to prepare acrylic acid (esters) from a mixed solution of formaldehyde and acetic acid (or a mixed aqueous solution).

[0005] A supported heteropolyacid catalyst, specifically:

[0006] Its chemical formula is H n [Z a+ (H2O)X b+ W 11 O 39 ·mH2O / S (simplified formula is XW 11 Z / S), where the substituted metal Z is one or more of Fe, Cs, La, Zn, V, Ti, Ba, Ce; X is one or two of P, Si; where the molar ratio of the substituted element X: the substituted metal Z: the central atom W is 1:1:11; where m is the number of crystal water molecules, n + a + b = 12, a and b are the valence states of the corresponding elements respectively, and n, a, and b are integers respectively; H n [Z a+ (H2O)X b+ W 11 O 39 ·mH2O is a heteropolyacid and S is a catalyst support.

[0007] The support includes one or more of γ-Al2O3, SBA-15, SiO2, ZSM-5;

[0008] The mass fraction of the heteropolyacid in the catalyst (based on the support) is 5 - 50 wt%, preferably 5 - 30%.

[0009] The described catalyst preparation method is characterized in that:

[0010] (1) Weigh 10 - 50 g of Na2WO4·2H2O, add it to deionized water at 50 - 70 °C to form an aqueous solution with a concentration of 0.1 - 1 mol / L, adjust the pH of the solution to 3 - 6 with 30 - 80 wt% acetic acid and / or 1 - 30 wt% hydrochloric acid, and then heat the solution to boiling;

[0011] (2) Weigh the precursor containing element Z, add it to deionized water at 50 - 70 °C to form an aqueous solution with a concentration of 0.1 - 2 mol / L, and then add this solution to the boiling solution in step (1) with stirring, and heat it to boiling under reflux and stir for 30 - 120 min;

[0012] (3) Weigh the precursor containing element X, add it to deionized water at 50 - 70 °C to form an aqueous solution with a concentration of 0.1 - 2 mol / L, and then add this solution to the boiling solution in step (2), adjust the pH of the solution to 2 - 6 with 30 - 80 wt% acetic acid and / or 1 - 30 wt% hydrochloric acid and keep stirring, continuously supplement water during the stirring process, and maintain the pH value at about 2 - 6, and stop stirring after 0.5 - 3 h;

[0013] (4) After cooling the solution in step (3) to room temperature, add anhydrous ethanol with the same volume as the solution in step (3) to obtain the product. Transfer the product into a separatory funnel, add 20 - 100 ml of ether and shake well to extract and separate the product. After shaking, the extraction phase, which is a mixture of heteropolyacid and ether, is located at the bottom layer of the solution, and the raffinate phase, which is the remaining aqueous solution of heteropolyacid after extraction, is located at the upper layer of the solution. Add 20 - 100 ml of ether to the raffinate phase and repeat the extraction 1 - 5 times. Collect the extraction phase and dissolve it in 50 - 200 ml of water, and transfer the solution to + an H-type Amberlite IR-120 cation exchange column for ion exchange. Repeat the ion exchange of the solution until the pH is less than 1 to obtain a solution;

[0014] (5) Weigh the support and add it to the solution prepared in step (4). After mixing evenly, filter off the excess water and dry it at 80 - 150 °C for 1 - 6 h, and then calcine it at 200 - 400 °C for 1 - 10 h to obtain the substituted heteropolyacid used as the catalyst XW 11 Z / S for the aldol condensation reaction.

[0015] The precursor of the substituted metal Z is one or more of nitrates, carbonates or acetates of Fe, Cs, La, Zn, Ba, Ce, or one or more of tetrabutyl titanate and ammonium metavanadate; the precursor of the substituted element X is one or more of phosphoric acid, phytic acid, dibutyl phosphate, triethyl phosphate, tetraethyl orthosilicate, tetramethyl orthosilicate, and silica sol.

[0016] The application of the catalyst is that this series of catalysts can be applied to the preparation of acrylic acid (and / or acrylate) from a mixed solution of formaldehyde and acetic acid or an aqueous mixed solution of formaldehyde and acetic acid. Using a fixed-bed reactor, the raw materials are a mixed solution of formaldehyde and acetic acid or an aqueous mixed solution of formaldehyde and acetic acid; the reaction temperature is 200 - 270 °C, the pressure is 0.05 - 1 MPa, and the LHSV during the reaction process is 0.1 - 3 h -1 ; the carrier gas is an oxygen-containing inert atmosphere, the O2 content is 1 - 5 vol% (preferably 1 - 3.5 vol%), and the inert gas is N2. The product that can be collected is a mixed solution containing acrylic acid and / or acrylate.

[0017] In the mixed solution of formaldehyde and acetic acid or the aqueous mixed solution of formaldehyde and acetic acid, n 甲醛 :n 醋酸 = 1:(1 - 10), preferably n 甲醛 :n 醋酸 = 1:(1 - 5). The mass content of water in the mixed solution is less than or equal to 36.2%;

[0018] Using a fixed-bed reactor, the middle section of the bed is filled with the catalyst (the formed catalyst is selected from 20 - 100 mesh), and the upper and lower sections are filled with quartz sand respectively.

[0019] The advantages of the present invention are that the catalyst has dual-functional active centers, strong activity, good selectivity, etc.

[0020] The beneficial technical effects of the present invention:

[0021] 1. The prepared heteropolyacid is a heteropolyacid with a Keggin-type structure, and its primary structure is a weak base. Therefore, the catalyst has certain acid-base active sites, mild reaction conditions, good catalyst activity and stability;

[0022] 2. As petroleum resources are facing depletion, the price of propylene, a petrochemical product, has increased, while the prices of acetic acid and formaldehyde, coal chemical products, are low, and the production exceeds the demand. Therefore, the process of preparing acrylic acid from acetic acid and formaldehyde through aldol condensation has great potential application value. It effectively improves the new structure of new coal-based downstream products. Specific embodiments

[0023] The preferred embodiments of the present invention are described in detail below, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0024] Example 1

[0025] Weigh 25 g of Na2WO4·2H2O and add it to deionized water at 50 °C to form an aqueous solution with a concentration of 0.55 mol / L. Adjust the pH of this solution to 5.3 with 45 wt% acetic acid, and then heat it to boiling, denoted as solution A; weigh 10.1 g of Fe(NO3)3·9H2O and add it to deionized water at 50 °C to form an aqueous solution with a concentration of 0.5 mol / L. Then add this solution to solution A under stirring and stir for 30 min, denoted as solution B; weigh 3.92 g of phosphoric acid and add it to deionized water at 50 °C to form an aqueous solution with a concentration of 0.8 mol / L. Then add this solution to solution B, adjust the pH to 5.0 with 60 wt% acetic acid and continue stirring. During the stirring process, continuously supplement water and maintain the pH value at 5.0. Stop stirring after 1.5 h, denoted as solution C. After solution C is cooled to room temperature, add 237.80 ml of absolute ethanol to obtain the product. Transfer the product to a separating funnel, add 40 ml of ether and shake it vigorously to extract and separate the product. Add 40 ml of ether to the raffinate phase (the remaining heteropolyacid mixed aqueous solution after extraction) and repeat the extraction 3 times. The extract phase (the mixture of heteropolyacid and ether) is dissolved in 100 ml of water, and the solution is transferred to H +In a type A Amberlite IR-120 cation exchange column, the solution was repeatedly ion-exchanged until the pH < 1, and the resulting heteropolyacid was H4Fe(H2O)PW 11 O 39 ·8H2O, denoted as D.

[0026] Weighed 20 g of the support γ-Al2O3 and added it to the prepared solution D, and continuously stirred for 6 h under the action of magnetic stirring; then carried out suction filtration, dried at 120 °C for 6 h, and finally calcined in a muffle furnace at 300 °C in an air atmosphere for 6 h to obtain the required catalyst, denoted as 5% FeW 11 P / γ-Al2O3;

[0027] The obtained sample was tableted into 40 - 60 mesh, and then loaded into a stainless steel tube fixed-bed reactor (the inner diameter of the fixed bed is 8 mm). The middle section of the bed was filled with the aldol condensation reaction catalyst, and the upper and lower sections of the catalyst bed were filled with quartz sand respectively; the raw material was a mixed solution of formaldehyde and acetic acid, the molar ratio of formaldehyde to acetic acid was 1:1, the reaction temperature was 270 °C, the pressure was 0.20 MPa, the residence time was 4 s, and the raw material LHSV = 3 h -1 The carrier gas was an oxygen-containing inert atmosphere (O2 content 5 vol%), and the inert gas was N2. Online gas chromatography monitoring; finally, after analysis, the formaldehyde conversion rate was 45.2%, and the selectivity of acrylic acid (and esters) was 89.3%.

[0028] Example 2

[0029] Weighed 35 g of Na2WO4·2H2O and added it to deionized water at 50 °C to form an aqueous solution of 0.55 mol / L. The pH of this solution was adjusted to 6.0 with 60 wt% acetic acid, and then heated to boiling, denoted as solution A; weighed 1.62 g of lanthanum nitrate and added it to deionized water at 50 °C to form an aqueous solution of 0.1 mol / L. Then, this solution was added to solution A under stirring, and stirred for 30 min, denoted as solution B; weighed 4.17 g of tetraethyl orthosilicate and added it to ethanol to form a solution of 0.4 mol / L. Then, this solution was added to solution B, and 20 wt% hydrochloric acid was added to adjust the pH to 6.0 and continuously stirred. During the stirring process, water was continuously supplemented to keep the pH value around 6.0. After 1.5 h, the stirring was stopped, denoted as solution C. After solution C was cooled to room temperature, anhydrous ethanol was added to obtain the product. The product was transferred to a separatory funnel, and 70 ml of ether was added and shaken well to extract and separate the product. The raffinate phase (the remaining heteropolyacid mixed aqueous solution after extraction) was added with 70 ml of ether and extracted 3 times repeatedly. The extract phase (the mixture of heteropolyacid and ether) was dissolved in 200 ml of water, and the solution was transferred to H +In a Type A Amberlite IR-120 cation exchange column, the solution was repeatedly ion-exchanged until the pH < 1, and the resulting heteropolyacid was H5La(H2O)SiW 11 O 39 ·9H2O, denoted as D.

[0030] Weighed 20 g of the support SBA-15 and added it to the prepared solution D, and continuously stirred for 6 h under magnetic stirring; then carried out suction filtration, dried at 120 °C for 3 h, and finally calcined in a muffle furnace at 350 °C in an air atmosphere for 6 h to obtain the required catalyst denoted as 20% LaW 11 Si / SBA-15;

[0031] The obtained sample was pressed into tablets of 40-60 mesh, and then loaded into a stainless steel tube fixed-bed reactor (inner diameter of the fixed bed: 8 mm). The raw materials were a mixed solution of formaldehyde and acetic acid, with a molar ratio of formaldehyde:acetic acid of 1:2, a reaction temperature of 270 °C, a pressure of 0.05 MPa, a residence time of 4 s, and LHSV = 3 h -1 . The carrier gas was an oxygen-containing inert atmosphere (O2 content: 5 vol%), and the inert gas was N2. Online gas chromatography monitoring; finally, after analysis, the formaldehyde conversion rate was 50%, and the selectivity for acrylic acid (ester) was 80.73%.

[0032] Example 3

[0033] Weighed 25 g of Na2WO4·2H2O and added it to deionized water at 60 °C to form an aqueous solution of 0.30 mol / L. The pH of this solution was adjusted to 5.6 with 20 wt% hydrochloric acid, and then heated to boiling, denoted as solution A; weighed 3.26 g of Ce(NO3)3 and added it to deionized water at 60 °C to form an aqueous solution of 0.2 mol / L. Then this solution was added to solution A under stirring and stirred for 30 min, denoted as solution B; weighed 9.11 g of triethyl phosphate and added it to deionized water at 60 °C to form an aqueous solution of 1.0 mol / L. Then this solution was added to solution B, and the pH was adjusted to 3.5 with 1 wt% hydrochloric acid and continuously stirred. During the stirring process, water was continuously replenished and the pH value was maintained at about 3.5. After 1.5 h, the stirring was stopped, denoted as solution C. After solution C was cooled to room temperature, anhydrous ethanol (352.64 ml) was added to obtain the product. The product was transferred to a separatory funnel, and 60 ml of ether was added and shaken well to extract and separate the product. The raffinate phase (the remaining heteropolyacid mixed aqueous solution after extraction) was added with 60 ml of ether and extracted 3 times repeatedly. The extract phase (the mixture of heteropolyacid and ether) was dissolved in 150 ml of water, and the solution was transferred to an H + type Amberlite IR-120 cation exchange column, and the solution was repeatedly ion-exchanged until the pH < 1 to obtain the heteropolyacid H3Ce(H2O)PW11 O 39 ·16H₂O, denoted as D.

[0034] Weigh 20 g of the carrier SiO₂ and add it to the prepared solution D, and continuously stir for 6 h under magnetic stirring; then perform suction filtration, dry at 120 °C for 6 h, and finally calcine in a muffle furnace at 200 °C in an air atmosphere for 10 h to obtain the required catalyst, denoted as 5% CeW 11 P / SiO₂;

[0035] Press the obtained sample into tablets of 40 - 60 mesh, and then load it into a stainless steel tube fixed-bed reactor (inner diameter of the fixed bed is 8 mm). The raw materials are a mixed solution of formaldehyde and acetic acid, and the molar ratio of formaldehyde to acetic acid is 1:1.5. The reaction temperature is 200 °C, the pressure is 0.05 MPa, the residence time is 4 s, and LHSV = 2 h -1 . The carrier gas is an oxygen-containing inert atmosphere (O₂ content 3.5 vol%), and the inert gas is N₂. Online monitoring by gas chromatography; finally, after analysis, the formaldehyde conversion rate is 50.40%, and the selectivity of acrylic acid (ester) is 80.09%.

[0036] Example 4

[0037] Weigh 45 g of Na₂WO₄·2H₂O, add it to deionized water at 60 °C to form an aqueous solution of 0.45 mol / L, adjust the pH of the solution to 5.5 with 30 wt% acetic acid, and then heat to boiling, denoted as solution A; weigh 34.04 g of tetrabutyl titanate, add it to anhydrous ethanol at 60 °C to form an aqueous solution of 2.0 mol / L, and then add this solution to solution A under stirring and stir for 30 min, denoted as solution B; weigh 9.01 g of silica sol (mass concentration 40 wt%), add it to deionized water at 60 °C to form an aqueous solution of 1.2 mol / L, and then add this solution to solution B, adjust the pH to 5.5 with 30 wt% acetic acid and continuously stir, continuously supplement water during the stirring process, and keep the pH value around 5.5. Stop stirring after 1.5 h, denoted as solution C. After solution C is cooled to room temperature, add 403.17 ml of anhydrous ethanol to obtain the product. Transfer the product to a separatory funnel, add 80 ml of ether and shake well to extract and separate the product. Add 80 ml of ether to the raffinate phase (the remaining heteropolyacid mixed aqueous solution after extraction) and repeat extraction 4 times. The extract phase (the mixture of heteropolyacid and ether) is dissolved in 200 ml of water, and transfer the solution to an H + type Amberlite IR-120 cation exchange column, and repeatedly perform ion exchange on the solution until the pH < 1, and the obtained heteropolyacid is H₄Ti(H₂O)SiW 11 O 39 ·22H₂O, denoted as D.

[0038] Weigh 20 g of the support γ-Al2O3 and add it to the prepared solution D, and continuously stir for 6 h under magnetic stirring; then perform suction filtration, dry at 120 °C for 1 h, and finally calcine in a muffle furnace at 300 °C in an air atmosphere for 6 h to obtain the required catalyst, denoted as 10% TiW 11 Si / γ-Al2O3;

[0039] Press the obtained sample into tablets with a particle size of 40-60 mesh, and then load it into a stainless steel tube fixed-bed reactor (inner diameter of the fixed bed: 8 mm). The raw material is a mixed solution of formaldehyde and acetic acid, with a molar ratio of formaldehyde to acetic acid of 1:10, a reaction temperature of 250 °C, a pressure of 0.10 MPa, a residence time of 4 s, and LHSV = 2 h -1 . The carrier gas is an oxygen-containing inert atmosphere (O2 content: 2.5 vol%), and the inert gas is N2. Online monitoring by gas chromatography; finally, after analysis, the formaldehyde conversion rate is 46.10%, and the selectivity to acrylic acid (ester) is 87.6%.

[0040] Example 5

[0041] Weigh 25 g of Na2WO4·2H2O, add it to deionized water at 70 °C to form a 2 mol / L aqueous solution, then heat to boiling, and slowly dropwise add 21 ml of 15 wt% hydrochloric acid to the solution under stirring, denoted as solution A; weigh 2.75 g of ammonium metavanadate, add it to deionized water at 70 °C to form a 0.2 mol / L aqueous solution, and then quickly add this solution to solution A. Dropwise add a 15 wt% hydrochloric acid solution to keep the pH around 5.5, and boil for 1 h and then cool to room temperature, denoted as solution B; then add 12.52 g of phytic acid to solution B, wash with cold water and filter to obtain the heteropolyacid PW 11 VO 39 ·13H2O, denoted as C.

[0042] Weigh 20 g of the support ZSM-5 and add it to the prepared solution C, and continuously stir for 6 h under magnetic stirring; then perform suction filtration, dry at 120 °C for 6 h, and finally calcine in a muffle furnace at 400 °C in an air atmosphere for 6 h to obtain the required catalyst, denoted as 15% PW 11 V / ZSM-5;

[0043] Press the obtained sample into tablets with a particle size of 40-60 mesh, and then load it into a stainless steel tube fixed-bed reactor (inner diameter of the fixed bed: 8 mm). The raw material is a mixed solution of formaldehyde and acetic acid, with a molar ratio of formaldehyde to acetic acid of 1:5, a reaction temperature of 200 °C, a pressure of 0.05 MPa, a residence time of 4 s, and LHSV = 1.5 h -1The carrier gas is an oxygen-containing inert atmosphere (O2 content: 5.0 vol%), and the inert gas is N2. Online gas chromatography monitoring; finally, through analysis, the conversion rate of formaldehyde is 42.7%, and the selectivity of acrylic acid (ester) is 94.5%.

[0044] Example 6

[0045] Weigh 25 g of Na2WO4·2H2O, add it to deionized water at 65 °C to form an aqueous solution with a concentration of 0.55 mol / L, adjust the pH of the solution to 4.6 with 1 wt% hydrochloric acid, and then heat it to boiling, denoted as solution A; weigh 3.31 g of Zn(NO3)2, add it to deionized water at 65 °C to form an aqueous solution with a concentration of 0.35 mol / L, and then add this solution to solution A under stirring and stir for 30 min, denoted as solution B; weigh 15.22 g of methyl orthosilicate, add it to high-temperature deionized water to form an aqueous solution with a concentration of 2.0 mol / L, and then add this solution to solution B, adjust the pH to 3.5 with 80 wt% acetic acid and continue stirring. During the stirring process, continuously supplement water and keep the pH value around 3.5. Stop stirring after 1.5 h, denoted as solution C. After solution C is cooled to room temperature, add 237.80 ml of absolute ethanol to obtain the product. Transfer the product into a separatory funnel, add 100 ml of ether and shake it well to extract and separate the product. Add ether to the raffinate phase (the remaining aqueous solution of heteropolyacid mixture after extraction) and repeat the extraction 2 times. The extract phase (the mixture of heteropolyacid and ether) is dissolved in 150 ml of water, and transfer the solution to + an H-type Amberlite IR-120 cation exchange column, and repeatedly perform ion exchange on the solution until the pH < 1, and the obtained heteropolyacid is H4Zn(H2O)SiW 11 O 39 ·11H2O, denoted as D.

[0046] Weigh 20 g of the carrier SBA-15 and add it to the prepared solution D, and continuously stir for 6 h under the action of magnetic stirring; then perform suction filtration, dry at 120 °C for 5 h, and finally calcine in a muffle furnace at 250 °C in an air atmosphere for 6 h. The obtained sample is the catalyst for producing methyl methacrylate, denoted as 10% ZnW 11 Si / SBA-15;

[0047] Press the obtained sample into tablets with a mesh size of 40 - 60, and then load it into a stainless steel tube fixed-bed reactor (the inner diameter of the fixed bed is 8 mm). The raw material is a mixed solution of formaldehyde and acetic acid, the molar ratio of formaldehyde to acetic acid is 1:7, the reaction temperature is 240 °C, the pressure is 0.15 MPa, the residence time is 10 s, and LHSV = 3 h -1The carrier gas is an oxygen-containing inert atmosphere (O2 content 1.5 vol%), and the inert gas is N2. Online gas chromatography monitoring; finally, the conversion rate of formaldehyde is analyzed to be 43.8%, and the selectivity of acrylic acid (ester) is 92.2%.

[0048] Example 7

[0049] Weigh 25 g of Na2WO4·2H2O and add it to deionized water at 60 °C to form an aqueous solution with a concentration of 0.10 mol / L. Adjust the pH of this solution to 6.0 with 2 wt% acetic acid, and then heat it to boiling, denoted as solution A; weigh 16.29 g of Cs2CO3 and add it to high-temperature deionized water to form an aqueous solution with a concentration of 1.0 mol / L. Then, add this solution to solution A with stirring and stir for 30 min, denoted as solution B; weigh 19.97 g of dibutyl phosphate and add it to high-temperature deionized water to form an aqueous solution with a concentration of 1.9 mol / L. Then, add this solution to solution B and adjust the pH to 5.0 with 30 wt% hydrochloric acid while continuously stirring. During the stirring process, continuously supplement water and maintain the pH value at about 5.0. Stop stirring after 1.5 h, denoted as solution C. After solution C is cooled to room temperature, add 857.92 ml of absolute ethanol to obtain the product. Transfer the product to a separatory funnel, add 90 ml of ether and shake it well to extract and separate the product. Add 90 ml of ether to the raffinate phase (the remaining aqueous solution of heteropolyacid mixture after extraction) and repeat the extraction 4 times. The extract phase (the mixture of heteropolyacid and ether) is dissolved in 150 ml of water, and the solution is transferred to an H + type Amberlite IR-120 cation exchange column, and the solution is repeatedly ion-exchanged until the pH < 1 to obtain the heteropolyacid H6Cs(H2O)PW 11 O 39 ·11H2O, denoted as D.

[0050] Weigh 20 g of the carrier γ-Al2O3 and add it to the prepared solution D, and continuously stir it for 3 h under the action of magnetic stirring; then carry out suction filtration, dry it at 120 °C for 6 h, and finally calcine it in a muffle furnace at 350 °C in an air atmosphere for 8 h to obtain the required catalyst, denoted as 8% CsW 11 P / γ-Al2O3;

[0051] Press the obtained sample into tablets with a size of 40 - 60 mesh, and then load it into a stainless steel tube fixed-bed reactor (the inner diameter of the fixed bed is 8 mm). The raw material is a mixed solution of formaldehyde and acetic acid, and the molar ratio of formaldehyde to acetic acid is 1:8. The reaction temperature is 270 °C, the pressure is 0.15 MPa, the residence time is 10 s, and LHSV = 3 h -1The carrier gas is an oxygen-containing inert atmosphere (O2 content 4.5 vol%), and the inert gas is N2. Online gas chromatography monitoring; finally, the conversion rate of formaldehyde is analyzed to be 42.6%, and the selectivity of acrylic acid (ester) is 94.8%.

[0052] Example 8

[0053] Weigh 35 g of Na2WO4·2H2O and add it to deionized water at 50 °C to form an aqueous solution with a concentration of 0.55 mol / L. Adjust the pH of this solution to 5.2 with 30 wt% hydrochloric acid, and then heat it to boiling, denoted as solution A; weigh 2.48 g of barium acetate, add it to deionized water at 50 °C to form an aqueous solution with a concentration of 0.22 mol / L, and then add this solution to solution A with stirring and stir for 30 min, denoted as solution B; weigh 11.84 g of triethyl phosphate, add it to deionized water at 50 °C to form an aqueous solution with a concentration of 1.3 mol / L, and then add this solution to solution B. Adjust the pH to 4.0 with 1.5 wt% hydrochloric acid and continue stirring. Continuously replenish water during the stirring process and keep the pH value around 4.0. Stop stirring after 1.5 h, denoted as solution C. After solution C is cooled to room temperature, add 292.93 ml of absolute ethanol to obtain the product. Transfer the product to a separatory funnel, add 100 ml of ether and shake it well to extract and separate the product. Add 100 ml of ether to the raffinate phase (the remaining mixed aqueous solution of heteropolyacid after extraction) and repeat the extraction 3 times. The extract phase (the mixture of heteropolyacid and ether) is dissolved in 200 ml of water, and transfer the solution to + an H-type Amberlite IR-120 cation exchange column, and repeatedly perform ion exchange on the solution until the pH < 1. The obtained heteropolyacid is H5Ba(H2O)PW 11 O 39 ·8H2O, denoted as D.

[0054] Weigh 20 g of the carrier SiO2 and add it to the prepared solution D, and continuously stir for 6 h under the action of magnetic stirring; then perform suction filtration, dry at 120 °C for 1 h, and finally calcine in a muffle furnace at 300 °C in an air atmosphere for 3 h. The obtained sample is the catalyst for producing methyl methacrylate, denoted as 12% BaW 11 P / SiO2;

[0055] Press the obtained sample into tablets with a size of 40 - 60 mesh, and then load it into a stainless steel tube fixed-bed reactor (the inner diameter of the fixed bed is 8 mm). The raw materials are a mixed solution of formaldehyde and acetic acid, and the molar ratio of formaldehyde to acetic acid is 1:3.5. The reaction temperature is 250 °C, the pressure is 0.15 MPa, the residence time is 10 s, and LHSV = 3 h -1The carrier gas is an oxygen-containing inert atmosphere (O2 content 4.5 vol%), and the inert gas is N2. Online gas chromatography monitoring; finally, the conversion rate of formaldehyde is analyzed to be 47.6%, and the selectivity of acrylic acid (ester) is 84.80%.

[0056] Example 9

[0057] Weigh 25 g of Na2WO4·2H2O, add it to deionized water at 60 °C to form an aqueous solution with a concentration of 0.35 mol / L, adjust the pH of the solution to 6.0 with 1 wt% hydrochloric acid, and then heat it to boiling, denoted as solution A; weigh 2.45 g of Ce(NO3)3, add it to deionized water at 60 °C to form an aqueous solution with a concentration of 0.15 mol / L, and then add this solution to solution A with stirring and stir for 30 min, denoted as solution B; weigh 7.74 g of triethyl phosphate, add it to deionized water at 60 °C to form an aqueous solution with a concentration of 0.85 mol / L, and then add this solution to solution B, adjust the pH to 2.0 with 80 wt% acetic acid and continue stirring. During the stirring process, continuously supplement water and keep the pH value around 2.0. Stop stirring after 1.5 h, denoted as solution C. After solution C is cooled to room temperature, add 316.55 ml of absolute ethanol to obtain the product. Transfer the product to a separating funnel, add 60 ml of ether and shake it well to extract and separate the product. Add 60 ml of ether to the raffinate phase (the remaining aqueous solution of heteropolyacid mixture after extraction) and repeat the extraction 3 times. The extract phase (the mixture of heteropolyacid and ether) is dissolved in 150 ml of water, and transfer the solution to an H + type Amberlite IR-120 cation exchange column, and repeatedly perform ion exchange on the solution until the pH < 1, and the obtained heteropolyacid is H3Ce(H2O)PW 11 O 39 ·16H2O, denoted as D.

[0058] Weigh 20 g of the carrier ZSM-5 and add it to the prepared solution D, and continuously stir for 6 h under the action of magnetic stirring; then perform suction filtration, dry at 120 °C for 6 h, and finally calcine in a muffle furnace at 400 °C in an air atmosphere for 6 h to obtain the required catalyst, denoted as 50% CeW 11 P / ZSM-5;

[0059] Press the obtained sample into tablets with a size of 40 - 60 mesh, and then load it into a stainless steel tube fixed-bed reactor (the inner diameter of the fixed bed is 8 mm). The raw material is a mixed solution of formaldehyde and acetic acid, the molar ratio of formaldehyde to acetic acid is 1:1.5, the reaction temperature is 200 °C, the pressure is 0.05 MPa, the residence time is 4 s, and LHSV = 2 h -1The carrier gas is an oxygen-containing inert atmosphere (O2 content 3.5 vol%), and the inert gas is N2. Online gas chromatography monitoring; finally, the formaldehyde conversion rate is analyzed to be 52.50%, and the selectivity of acrylic acid (ester) is 80.2%.

[0060] Example 10

[0061] Weigh 45 g of Na2WO4·2H2O and add it to deionized water at 60 °C to form a 1.0 mol / L aqueous solution. Adjust the pH of this solution to 3.5 with 80 wt% acetic acid, and then heat it to boiling, denoted as solution A; weigh 4.08 g of tetrabutyl titanate and add it to anhydrous ethanol at 60 °C to form a 0.24 mol / L aqueous solution. Then, add this solution to solution A under stirring and stir for 30 min, denoted as solution B; weigh 5.11 g of silica sol (mass concentration 40 wt%) and add it to deionized water at 60 °C to form a 0.68 mol / L aqueous solution. Then, add this solution to solution B and adjust the pH to 3.5 with 23 wt% hydrochloric acid while continuously stirring. During the stirring process, continuously supplement water and keep the pH value around 3.5. Stop stirring after 1.5 h, denoted as solution C. After solution C is cooled to room temperature, add 236.43 ml of anhydrous ethanol to obtain the product. Transfer this product into a separatory funnel, add 80 ml of ether and shake it well to extract and separate the product. Add 80 ml of ether to the raffinate phase (the remaining mixed aqueous solution of heteropolyacid after extraction) and repeat the extraction 4 times. The extract phase (the mixture of heteropolyacid and ether) is dissolved in 200 ml of water, and transfer the solution to an H + type Amberlite IR-120 cation exchange column, and repeatedly perform ion exchange on the solution until the pH < 1, and the obtained heteropolyacid is H4Ti(H2O)SiW 11 O 39 ·22H2O, denoted as D.

[0062] Weigh 20 g of the carrier SBA-15 and add it to the prepared solution D, and continuously stir for 6 h under magnetic stirring; then perform suction filtration, dry at 120 °C for 1 h, and finally calcine in a muffle furnace at 250 °C in an air atmosphere for 6 h to obtain the required catalyst, denoted as 20% TiW 11 Si / SBA-15;

[0063] Press the obtained sample into tablets with a particle size of 40 - 60 mesh, and then load it into a stainless steel tube fixed-bed reactor (the inner diameter of the fixed bed is 8 mm). The raw material is a mixed solution of formaldehyde and acetic acid, and the molar ratio of formaldehyde to acetic acid is 1:10. The reaction temperature is 200 °C, the pressure is 0.10 MPa, the residence time is 4 s, and LHSV = 2 h -1The carrier gas is an oxygen-containing inert atmosphere (O2 content 2.5 vol%), and the inert gas is N2. Online gas chromatography monitoring; finally, the conversion rate of formaldehyde is analyzed to be 46.90%, and the selectivity of acrylic acid (ester) is 86.1%.

[0064] Example 11

[0065] Weigh 25 g of Na2WO4·2H2O and add it to deionized water at 60 °C to form an aqueous solution with a concentration of 0.20 mol / L. Adjust the pH of this solution to 4.9 with 30 wt% hydrochloric acid, and then heat it to boiling, denoted as solution A; weigh 26.07 g of Cs2CO3 and add it to high-temperature deionized water to form an aqueous solution with a concentration of 1.6 mol / L. Then, add this solution to solution A under stirring and stir for 30 min, denoted as solution B; weigh 13.66 g of dibutyl phosphate and add it to high-temperature deionized water to form an aqueous solution with a concentration of 1.3 mol / L. Then, add this solution to solution B, adjust the pH to 4.2 with 60 wt% acetic acid and continue stirring. During the stirring process, continuously supplement water and maintain the pH value at about 4.2. Stop stirring after 1.5 h, denoted as solution C. After solution C is cooled to room temperature, add 478.96 ml of absolute ethanol to obtain the product. Transfer this product to a separating funnel, add 90 ml of ether and shake it well to extract and separate the product. Add 90 ml of ether to the raffinate phase (the remaining aqueous solution of heteropolyacid mixture after extraction) and repeat the extraction 4 times. The extract phase (the mixture of heteropolyacid and ether) is dissolved in 150 ml of water, and transfer the solution to an H + type Amberlite IR-120 cation exchange column, and repeatedly perform ion exchange on the solution until the pH < 1, and the obtained heteropolyacid is H6Cs(H2O)PW 11 O 39 ·11H2O, denoted as D.

[0066] Weigh 20 g of the carrier SBA-15 and add it to the prepared solution D, and continuously stir for 3 h under the action of magnetic stirring; then perform suction filtration, dry at 120 °C for 6 h, and finally calcine in a muffle furnace at 400 °C in an air atmosphere for 8 h to obtain the required catalyst, denoted as 7% CsW 11 P / SBA-15;

[0067] Press the obtained sample into tablets with a size of 40 - 60 mesh, and then load it into a stainless steel tube fixed-bed reactor (the inner diameter of the fixed bed is 8 mm). The raw material is a mixed solution of formaldehyde and acetic acid, and the molar ratio of formaldehyde to acetic acid is 1:8. The reaction temperature is 270 °C, the pressure is 0.15 MPa, the residence time is 10 s, and LHSV = 3 h -1The carrier gas is an oxygen-containing inert atmosphere (O2 content: 4.5 vol%), and the inert gas is N2. Online gas chromatography monitoring; finally, through analysis, the conversion rate of formaldehyde is 43.3%, and the selectivity of acrylic acid (ester) is 93.2%.

[0068] Example 12

[0069] Weigh 35 g of Na2WO4·2H2O, add it to deionized water at 50 °C to form an aqueous solution with a concentration of 0.85 mol / L, adjust the pH of this solution to 5.3 with 60 wt% acetic acid, and then heat it to boiling, denoted as solution A; weigh 10.14 g of barium acetate, add it to deionized water at 50 °C to form an aqueous solution with a concentration of 0.90 mol / L, and then add this solution to solution A under stirring and stir for 30 min, denoted as solution B; weigh 7.92 g of triethyl phosphate, add it to deionized water at 50 °C to form an aqueous solution with a concentration of 0.87 mol / L, and then add this solution to solution B, adjust the pH to 4.0 with 30 wt% acetic acid and continue stirring. During the stirring process, continuously supplement water and keep the pH value around 4.0. Stop stirring after 1.5 h, denoted as solution C. After solution C is cooled to room temperature, add 224.83 ml of absolute ethanol to obtain the product. Transfer this product into a separating funnel, add 100 ml of ether and shake it well to extract and separate the product. Add 100 ml of ether to the raffinate phase (the remaining mixed aqueous solution of heteropolyacid after extraction) and repeat the extraction 3 times. The extract phase (the mixture of heteropolyacid and ether) is dissolved in 200 ml of water, and transfer the solution to an H + type Amberlite IR-120 cation exchange column, and repeatedly perform ion exchange on the solution until the pH < 1, and the obtained heteropolyacid is H5Ba(H2O)PW 11 O 39 ·8H2O, denoted as D.

[0070] Weigh 20 g of the carrier γ-Al2O3 and add it to the prepared solution D, and continuously stir for 6 h under the action of magnetic stirring; then perform suction filtration, dry at 120 °C for 1 h, and finally calcine in a muffle furnace at 300 °C in an air atmosphere for 3 h. The obtained sample is the catalyst for producing methyl methacrylate, denoted as 14% BaW 11 P / γ-Al2O3;

[0071] Press the obtained sample into tablets with a size of 40 - 60 mesh, and then load it into a stainless steel tube fixed-bed reactor (the inner diameter of the fixed bed is 8 mm). The raw materials are a mixed solution of formaldehyde and acetic acid, the molar ratio of formaldehyde to acetic acid is 1:3.5, the reaction temperature is 260 °C, the pressure is 0.15 MPa, the residence time is 10 s, and LHSV = 3 h -1The carrier gas is an oxygen-containing inert atmosphere (O2 content 4.5 vol%), and the inert gas is N2. Online gas chromatography monitoring; finally, the conversion rate of formaldehyde is analyzed to be 48.2%, and the selectivity of acrylic acid (ester) is 83.70%.

[0072] Comparative Example 1

[0073] Weigh 25 g of Na2WO4·2H2O and add it to deionized water at 50 °C to form an aqueous solution with a concentration of 0.55 mol / L. Adjust the pH of this solution to 5.3 with 45 wt% acetic acid, and then heat it to boiling, denoted as solution A; weigh 10.1 g of Fe(NO3)3·9H2O and add it to deionized water at 50 °C to form an aqueous solution with a concentration of 0.5 mol / L. Then, add this solution to solution A with stirring and stir for 30 min, denoted as solution B; weigh 3.92 g of phosphoric acid and add it to deionized water at 50 °C to form an aqueous solution with a concentration of 0.8 mol / L. Then, add this solution to solution B, adjust the pH to 5.0 with 60 wt% acetic acid and continue stirring. During the stirring process, continuously supplement water and maintain the pH value at 5.0. Stop stirring after 1.5 h, denoted as solution C. After solution C is cooled to room temperature, add 237.80 ml of absolute ethanol to obtain the product. Transfer the product to a separatory funnel, add 40 ml of ether and shake it well to extract and separate the product. Add 40 ml of ether to the raffinate phase (the remaining mixed aqueous solution of heteropolyacid after extraction) and repeat the extraction 3 times. The extract phase (the mixture of heteropolyacid and ether) is dissolved in 100 ml of water, and the solution is transferred to an H + type Amberlite IR-120 cation exchange column, and the solution is repeatedly ion-exchanged until the pH < 1 to obtain the heteropolyacid H4Fe(H2O)PW 11 O 39 ·8H2O. Place it in a muffle furnace at 300 °C and calcine it in an air atmosphere for 6 h to obtain the required catalyst, denoted as FeW 11 P;

[0074] Press the obtained sample into tablets with a size of 40 - 60 mesh, and then load it into a stainless steel tube fixed-bed reactor (the inner diameter of the fixed bed is 8 mm). Fill the middle section of the bed with the above aldol condensation reaction catalyst, and fill the upper and lower sections of the catalyst bed with quartz sand respectively; the raw material is a mixed solution of formaldehyde and acetic acid, and the molar ratio of formaldehyde to acetic acid is 1:1. The reaction temperature is 270 °C, the pressure is 0.20 MPa, the residence time is 4 s, and the raw material LHSV = 3 h -1 The carrier gas is an oxygen-containing inert atmosphere (O2 content 5 vol%), and the inert gas is N2. Online gas chromatography monitoring; finally, the conversion rate of formaldehyde is analyzed to be 15.2%, and the selectivity of acrylic acid (and ester) is 67.1%.

[0075] Comparative Example 2

[0076] Weigh 25 g of Na2WO4·2H2O and add it to deionized water at 50 °C to form an aqueous solution with a concentration of 0.55 mol / L. Adjust the pH of this solution to 5.3 with 45 wt% acetic acid, and then heat it to boiling. Denote this as solution A. Weigh 10.1 g of Fe(NO3)3·9H2O and add it to deionized water at 50 °C to form an aqueous solution with a concentration of 0.5 mol / L. Then, add this solution to solution A with stirring and stir for 30 min. Denote this as solution B. Weigh 3.92 g of phosphoric acid and add it to deionized water at 50 °C to form an aqueous solution with a concentration of 0.8 mol / L. Then, add this solution to solution B, adjust the pH to 5.0 with 60 wt% acetic acid, and continue stirring. Continuously replenish water during the stirring process and maintain the pH value at 5.0. Stop stirring after 1.5 h. Denote this as solution C. After solution C is cooled to room temperature, add 237.80 ml of absolute ethanol to obtain the product. Transfer this product to a separatory funnel, add 40 ml of ether, and shake it well to extract and separate the product. Add 40 ml of ether to the raffinate phase (the remaining mixed aqueous solution of heteropolyacid after extraction) and repeat the extraction 3 times. The extract phase (the mixture of heteropolyacid and ether) is dissolved in 100 ml of water. Transfer the solution to an H + type Amberlite IR-120 cation exchange column, and repeatedly perform ion exchange on the solution until the pH < 1. The obtained heteropolyacid is H4Fe(H2O)PW 11 O 39 ·8H2O, denoted as D.

[0077] Weigh 20 g of the support γ-Al2O3 and add it to the prepared solution D, and continuously stir for 6 h under the action of magnetic stirring; then perform suction filtration, dry at 120 °C for 6 h, and finally calcine in a muffle furnace at 300 °C in an air atmosphere for 6 h to obtain the required catalyst, denoted as 5% FeW 11 P / γ-Al2O3;

[0078] Press the obtained sample into tablets with a size of 40 - 60 mesh, and then load it into a stainless steel tube fixed-bed reactor (the inner diameter of the fixed bed is 8 mm). Fill the middle section of the bed with the above aldol condensation reaction catalyst, and fill the upper and lower sections of the catalyst bed with quartz sand respectively; the raw materials are a mixed solution of formaldehyde and acetic acid, and the molar ratio of formaldehyde to acetic acid is 1:1. The reaction temperature is 360 °C, the pressure is 0.20 MPa, the residence time is 4 s, and the raw material LHSV = 3 h -1 . The carrier gas is an oxygen-containing inert atmosphere (O2 content 5 vol%), and the inert gas is N2. Online monitoring by gas chromatography; finally, after analysis, the formaldehyde conversion rate is 10.2%, and the selectivity of acrylic acid (and esters) is 52.3%.

[0079] Comparative Example 3

[0080] Weigh 4.8 g of vanadium pentoxide and 72 ml of benzyl alcohol, reflux at 140 °C for 6 hours, add 2.1 g of PEG6000 to the reaction medium. After 1 hour, add 6.45 g of concentrated phosphoric acid with a mass percentage concentration of 85%, and reflux for 6 hours. The resulting dark blue suspension mixture is denoted as C. Weigh 58.5 g of the support ZSM-5 and add it to the prepared solution C, and continuously stir for 6 h under the action of magnetic stirring; then perform suction filtration, dry at 120 °C for 6 h, and finally calcine in a muffle furnace at 400 °C in an air atmosphere for 6 h to obtain the required catalyst denoted as 15% VPO / ZSM-5;

[0081] Press the obtained sample into tablets of 40 - 60 mesh, and then load it into a stainless steel tube fixed-bed reactor (the inner diameter of the fixed bed is 8 mm). The raw material is a mixed solution of formaldehyde and acetic acid, and the molar ratio of formaldehyde to acetic acid is 1:5. The reaction temperature is 200 °C, the pressure is 0.05 MPa, the residence time is 4 s, and LHSV = 1.5 h -1 . The carrier gas is an oxygen-containing inert atmosphere (O2 content 5.0 vol%), and the inert gas is N2. Online monitoring by gas chromatography; finally, after analysis, the formaldehyde conversion rate is 34.7%, and the selectivity of acrylic acid (ester) is 71.9%.

[0082] Under the same evaluation conditions, by comparing Comparative Example 1 with Example 1, it is found that without a carrier, both the formaldehyde conversion rate and the selectivity of acrylic acid decrease significantly. The reason may be that compared with having a carrier, it will cause a decrease in parameters such as specific surface area, pore volume, and pore diameter, which is not conducive to the diffusion of reactant molecules; by comparing Comparative Example 2 with Example 2, it is found that at a higher reaction temperature, the decomposition of heteropolyacid will further damage the structure of the catalyst and cause a change in its acidity. Therefore, the heteropolyacid catalyst is not conducive to the reaction at high temperatures; by comparing Comparative Example 3 with Example 5, it is found that the reason may be that the VPO / ZSM-5 catalyst is an L acid, and the PW11V / ZSM-5 catalyst has both B acid and L acid. Therefore, the PW11V / ZSM-5 catalyst has higher activity.

[0083] The above are only examples of the present invention, and do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the content of the specification of the present invention, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A supported heteropolyacid catalyst, characterized in that: Its chemical formula For H n [Z a+ (H2O)X b+ W 11 O 39 ·mH2O / S (simplified formula: XW 11 Z / S), where the substituted metal Z is one or more of Fe, Cs, La, Zn, V, Ti, Ba, Ce; X is one or two of P, Si; where the molar ratio of the substituted element X: the substituted metal Z: the central atom W is 1:1:11; where m is the number of water of crystallization, n + a + b = 12, a and b are the valence states of the corresponding elements respectively, and n, a and b are integers respectively; H n [Z a+ (H2O)X b + W 11 O 39 ·mH2O is a heteropolyacid and S is a catalyst support.

2. The catalyst according to claim 1, characterized in that, The carrier includes one or more of γ-Al2O3, SBA-15, SiO2, and ZSM-5; The mass fraction of the heteropolyacid in the catalyst (based on the carrier) is 5-50 wt%, preferably 5-30%.

3. A method for preparing the catalyst according to any one of claims 1 or 2, characterized in that: (1) Weigh 10-50 g of Na2WO4·2H2O, add it to deionized water at 50-70 °C to form an aqueous solution with a concentration of 0.1-1 mol / L. Adjust the pH of the solution to 3-6 with 30-80 wt% acetic acid and / or 1-30 wt% hydrochloric acid, and then heat the solution to boiling; (2) Weigh the precursor containing element Z, add it to deionized water at 50-70 °C to form an aqueous solution with a concentration of 0.1-2 mol / L, and then add this solution to the boiling solution in step (1) with stirring, and keep boiling under reflux and stirring for 30-120 min; (3) Weigh the precursor containing element X, add it to deionized water at 50-70 °C to form an aqueous solution with a concentration of 0.1-2 mol / L, and then add this solution to the boiling solution in step (2). Adjust the pH of the solution to 2-6 with 30-80 wt% acetic acid and / or 1-30 wt% hydrochloric acid and keep stirring. Continuously supplement water during the stirring process and maintain the pH value at about 2-6. Stop stirring after 0.5-3 h; (4)After cooling the solution in step (3) to room temperature, add anhydrous ethanol with the same volume as the solution in step (3) to obtain a product. Transfer the product into a separatory funnel, add 20 - 100 ml of ether and shake well to extract and separate the product. After shaking, the extraction phase, which is a mixture of heteropolyacid and ether, is located at the bottom layer of the solution, and the raffinate phase, which is the remaining aqueous solution of heteropolyacid after extraction, is located at the upper layer of the solution. Add 20 - 100 ml of ether to the raffinate phase and repeat the extraction 1 - 5 times. Collect the extraction phase and dissolve it in 50 - 200 ml of water. Transfer the solution to an H + -type Amberlite IR-120 cation exchange column for ion exchange. Repeat the ion exchange of the solution until the pH < 1 to obtain a solution; (5) Weigh the carrier and add it to the solution prepared in step (4). After mixing evenly, filter off the excess moisture and dry it at 80 - 150 °C for 1 - 6 h, and then calcine it at 200 - 400 °C for 1 - 10 h to obtain the substituted heteropolyacid catalyst XW 11 Z / S for the aldol condensation reaction.

4. The method for preparing the catalyst according to claim 3, characterized in that, The precursor of the substituted metal Z is one or more of nitrates, carbonates, or acetates of Fe, Cs, La, Zn, Ba, Ce, or one or more of tetrabutyl titanate and ammonium metavanadate; the precursor of the substituted element X is one or more of phosphoric acid, phytic acid, dibutyl phosphate, triethyl phosphate, tetraethyl orthosilicate, tetramethyl orthosilicate, and silica sol.

5. The application of the catalyst according to any one of claims 1 or 2, characterized in that: This series of catalysts can be applied to the preparation of acrylic acid (and / or acrylate) from a mixed solution of formaldehyde and acetic acid or an aqueous mixed solution of formaldehyde and acetic acid.

6. The application of the catalyst according to claim 5, characterized in that: Using a fixed-bed reactor, the raw materials are a mixed solution of formaldehyde and acetic acid or an aqueous mixed solution of formaldehyde and acetic acid; the reaction temperature is 200 - 270 °C, the pressure is 0.05 - 1 MPa, and the LHSV during the reaction process is 0.1 - 3 h -1 ; the carrier gas is an oxygen-containing inert atmosphere, the O2 content is 1 - 5 vol% (preferably 1 - 3.5 vol%), and the inert gas is N2. The product that can be collected is a mixed solution containing acrylic acid and / or acrylate.

7. The application of the catalyst according to claim 6, characterized in that: In the mixed solution of formaldehyde and acetic acid or the aqueous mixed solution of formaldehyde and acetic acid, n 甲醛 :n 醋酸 = 1:(1 - 10), preferably n 甲醛 :n 醋酸 = 1:(1 - 5).

8. The application of the catalyst according to claim 6, characterized in that: The mass content of water in the mixed solution is less than or equal to 36.2%; Using a fixed-bed reactor, fill the middle section of the bed with the catalyst (the formed catalyst is 20-100 mesh), and fill the upper and lower sections with quartz sand respectively.