Supported heteropolyacid catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of olefine aldehyde oxidation, and discloses a supported heteropolyacid catalyst and a preparation method and application thereof.The supported heteropolyacid catalyst comprises a carrier and heteropolyacid supported on the carrier, the carrier is ammonium modified diatomite, and the heteropolyacid comprises phosphorus, vanadium and molybdenum. The invention discloses a method for preparing a supported heteropolyacid catalyst. The method comprises the following steps: (1) contacting diatomite with an ammonium modification reagent for reaction to obtain ammonium modified diatomite; wherein the ammonium modification reagent is inorganic salt containing nitrogen element; and (2) loading heteropoly acid on the ammonium modified diatomite, wherein the heteropoly acid contains phosphorus, vanadium and molybdenum. The catalyst provided by the invention has high olefine aldehyde conversion rate and olefine acid selectivity in olefine aldehyde oxidation preparation of olefine acid.

Description

Technical Field

[0001] The invention relates to the technical field of olefin aldehyde oxidation, and in particular to a supported heteropolyacid catalyst and a preparation method and application thereof. Background Art

[0002] Keggin-type heteropolyacids are a class of metal-oxygen cluster compounds formed by oxygen atoms bridging metal atoms. They are highly efficient bifunctional catalysts with both acid catalytic properties and redox properties, and are widely used in catalytic reactions. In recent years, with the increase in market demand for methyl methacrylate, as a key step in the preparation of methyl methacrylate by the isobutylene method, the oxidation of methacrolein to methacrylic acid has been favored by the scientific research and industrial communities, and the Keggin-type heteropolyacid catalyst used in this process has become a research hotspot. Although the catalyst has been industrially applied, there are still problems with low methacrolein conversion and low methacrylic acid yield, so it is urgent to improve the performance of Keggin-type heteropolyacid catalysts. Summary of the invention

[0003] The purpose of the present invention is to overcome the problem of poor catalyst stability of supported heteropolyacid catalysts in catalyzing olefin aldehyde oxidation reactions in the prior art, and to provide a supported heteropolyacid catalyst and a preparation method and application thereof.

[0004] In order to achieve the above objectives, the first aspect of the present invention provides a supported heteropolyacid catalyst, which includes a carrier and a heteropolyacid supported on the carrier, wherein the carrier is ammonium-modified diatomaceous earth, and the heteropolyacid includes phosphorus, vanadium and molybdenum.

[0005] The second aspect of the present invention provides a method for preparing a supported heteropolyacid catalyst, the method comprising:

[0006] (1) contacting diatomaceous earth with an ammonium modification reagent to react to obtain ammonium-modified diatomaceous earth; wherein the ammonium modification reagent is an inorganic salt containing nitrogen;

[0007] (2) A heteropoly acid is supported on ammonium-modified diatomaceous earth, wherein the heteropoly acid contains phosphorus, vanadium and molybdenum.

[0008] The third aspect of the present invention provides a catalyst prepared by the method described above.

[0009] The fourth aspect of the present invention provides the use of the above-mentioned catalyst and / or the catalyst prepared by the above-mentioned method in the oxidation of olefinic aldehyde to produce olefinic acid, and particularly preferably in the oxidation of methacrolein to produce methacrylic acid.

[0010] A fifth aspect of the present invention provides a method for preparing enoic acid by oxidation of enoaldehyde, the method comprising: in the presence of the above-mentioned catalyst and / or the catalyst prepared by the above-mentioned method, allowing enoaldehyde to undergo oxidation reaction to produce enoic acid.

[0011] Through the above technical solution, the present invention achieves the following beneficial effects:

[0012] (1) The catalyst of the present invention has a high olefin conversion rate and olefin acid selectivity in the preparation of olefin acid by olefin oxidation, especially a high methacrolein conversion rate and methacrylic acid selectivity in the preparation of methacrylic acid by methacrolein oxidation. The catalyst has high stability and can still maintain a high olefin conversion rate and olefin acid selectivity after long-term operation.

[0013] (2) The catalyst prepared by the method of the present invention is prepared by using natural diatomaceous earth as a carrier after being modified with ammonium, and loading a heteropoly acid containing phosphorus, vanadium and molybdenum on the carrier. The carrier raw material of the present invention has a wide source, the carrier preparation method is simple, time-saving, easy to operate, and is conducive to industrial application. In addition, the three wastes are less discharged during the catalyst preparation process. In the carrier preparation process of the present invention, there is no need to use expensive templates and silane coupling agents, and the cost of the catalyst is greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a SEM picture of the catalyst prepared in Example 1;

[0015] Figure 2 This is the BET adsorption-desorption curve of the catalyst prepared in Example 1. DETAILED DESCRIPTION

[0016] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0017] The first aspect of the present invention provides a supported heteropolyacid catalyst, which comprises a carrier and a heteropolyacid supported on the carrier, wherein the carrier is ammonium-modified diatomaceous earth, and the heteropolyacid comprises phosphorus, vanadium and molybdenum.

[0018] According to the present invention, preferably, the heteropoly acid is composed of A a B b C c P x V y Mo12 O z , wherein P, V, Mo, and O represent phosphorus, vanadium, molybdenum, and oxygen, respectively; A is at least one of iron, cobalt, nickel, zinc, chromium, copper, magnesium, manganese, germanium, bismuth, zirconium, silver, barium, gallium, cerium, selenium, silicon, boron, tungsten, and lanthanide elements other than promethium; B is at least one of arsenic, tellurium, and antimony; C is an alkali metal element and / or NH4 + ; a, b, c, x, y and z are the atomic ratios of the elements, wherein a is 0-3, b is 0-3, c is 0-3, preferably 0.01-3, x is 0.5-3, y is 0.01-3, and z is the atomic ratio of oxygen element required to satisfy the valence of the above-mentioned components.

[0019] According to the present invention, preferably, the alkali metal element includes at least one of sodium, potassium, rubidium and cesium.

[0020] According to the present invention, preferably, the specific surface area of ​​the catalyst is 20-60m 2 / g.

[0021] According to the present invention, preferably, the ammonium content in the carrier is 1-5% by weight, for example, it can be 1% by weight, 1.5% by weight, 2% by weight, 2.5% by weight, 3% by weight, 3.5% by weight, 4% by weight, 4.5% by weight, 5% by weight, and a range consisting of any two of the above, more preferably 4-5% by weight.

[0022] According to the present invention, the catalyst contains mesopores and micropores. Preferably, the average pore size of the mesopores in the catalyst is 3.0-4.6 nm, and the percentage of the pore volume occupied by the mesopores to the total pore volume is 90-100%. In the present invention, the percentage of the pore volume occupied by the mesopores to the total pore volume can be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, and the range consisting of any two of the above points.

[0023] According to the present invention, preferably, the content of the carrier is 20-70% by weight based on the total weight of the catalyst. The content of each component in the catalyst of the present invention is calculated based on the feed amount.

[0024] According to the present invention, preferably, based on the total weight of the catalyst, the content of the heteropolyacid is 30-80 wt%, for example, 30 wt%, 40 wt%, 50 wt%, 60 wt%, 70 wt%, 80 wt%, and a range consisting of any two of the above.

[0025] The second aspect of the present invention provides a method for preparing a supported heteropolyacid catalyst, the method comprising:

[0026] (1) contacting diatomaceous earth with an ammonium modification reagent to perform an ammonium modification reaction to obtain ammonium-modified diatomaceous earth; wherein the ammonium modification reagent is an inorganic salt containing nitrogen;

[0027] (2) A heteropoly acid is supported on ammonium-modified diatomaceous earth, wherein the heteropoly acid contains phosphorus, vanadium and molybdenum.

[0028] The inventors of the present invention speculate that the diatomaceous earth treated with an ammonium modification reagent containing an inorganic salt of nitrogen element can effectively prevent the (Keggin-type) heteropoly acid from reacting with silicon in the diatomaceous earth, thereby avoiding destruction of the structure of the (Keggin-type) heteropoly acid. As a result, the prepared catalyst has a higher catalytic performance for preparing olefinic acid by oxidation of olefinic aldehydes, and the catalyst has excellent stability.

[0029] According to the present invention, preferably, the specific surface area of ​​the diatomaceous earth is 35-65m 2 / g.

[0030] According to the present invention, preferably, the content of silicon dioxide in the diatomaceous earth is 65-100% by weight, and more preferably, the content of silicon oxide in the diatomaceous earth is 95-99.9% by weight.

[0031] According to the present invention, preferably, the inorganic salt of the nitrogen-containing element is an ammonium salt, more preferably, the inorganic salt of the nitrogen-containing element includes at least one of ammonium chloride, ammonium nitrate, ammonium sulfate, ammonium carbonate, ammonium phosphate and ammonium acetate; more preferably, the inorganic salt of the nitrogen-containing element includes at least one of ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium carbonate, ammonium bicarbonate and ammonium monohydrogen phosphate.

[0032] According to the present invention, preferably, the (total) amount of the ammonium modification agent calculated as nitrogen element is 0.1-4 mol per 100 g of diatomaceous earth, for example, it can be 0.1 mol, 0.5 mol, 1 mol, 1.5 mol, 2 mol, 2.5 mol, 3 mol, 3.5 mol, 4 mol, and a range consisting of any two of the above points.

[0033] According to the present invention, preferably, the ammonium modification reagent is in the form of a solution and is contacted with diatomaceous earth for reaction. More preferably, the concentration of the ammonium modification reagent in the ammonium modification reagent solution is 0.1-2 mol / L. The solvent in the ammonium modification reagent solution can be water, or any solvent that can dissolve the ammonium modification reagent and will not inhibit the reaction. Preferably, the solvent in the ammonium modification reagent solution is water.

[0034] According to the present invention, under normal circumstances, diatomite can be contacted with an ammonium modification agent once, or it can be contacted with an ammonium modification agent multiple times. Preferably, the ammonium modification agent is contacted with diatomite in several portions in sequence. More preferably, the mode of contacting diatomite with an ammonium modification agent for reaction includes: the ammonium modification agent is formulated into an aqueous solution, then divided into two equal parts, first contacting diatomite with a first portion of an ammonium modification agent aqueous solution for reaction (through suction filtration, washing, drying) to obtain a modified diatomite; and then contacting the modified diatomite with a second portion of an ammonium modification agent aqueous solution for reaction (through suction filtration, washing, drying) to obtain ammonium modified diatomite. By contacting the ammonium modification agent with diatomite for reaction in batches, the silicon in diatomite can be further avoided from reacting with heteropolyacids, and the olefin aldehyde conversion rate and olefin acid selectivity of the catalyst, as well as the stability of the catalyst, can be improved.

[0035] According to the present invention, in order to further increase the amino loading of diatomite and improve the catalytic effect and stability of the catalyst, preferably, the conditions of the ammonium modification reaction include: temperature of 25-100° C. and time of 4-96 h.

[0036] In the present invention, the device for the ammonium modification reaction is not particularly limited, and any device that can meet the temperature required for the ammonium modification reaction can be used, for example, a reactor containing diatomaceous earth and a reaction solution of an ammonium modification agent is placed in a water bath to carry out the ammonium modification reaction. Generally, the ammonium modification reaction is carried out under stirring, and the stirring speed can be 100-700 r / min.

[0037] According to the present invention, preferably, step (1) further comprises solid-liquid separation of the product of the ammonium modification reaction to obtain a solid material, and then drying the solid material. The solid-liquid separation method may be filtration, suction filtration, etc. commonly used in the art. Drying may be a drying method commonly used in the art, such as drying in a vacuum drying oven, a blast drying oven, a constant temperature drying oven, and a programmed temperature drying oven, etc., the drying temperature is usually 50-150°C, and the drying time is usually 12-72h.

[0038] According to the present invention, preferably, before the solid material is dried, the solid material is washed, and distilled water or deionized water can be used for washing.

[0039] According to the present invention, preferably, in step (2), the amounts of the ammonium-modified diatomaceous earth and the heteropoly acid are such that the content of the heteropoly acid in the obtained catalyst is 30-80% by weight.

[0040] According to the present invention, preferably, in step (2), the amounts of the ammonium-modified diatomaceous earth and the heteropoly acid are such that the content of the ammonium-modified diatomaceous earth in the obtained catalyst is 20-70% by weight.

[0041] According to the present invention, the loading method is not particularly limited and can be a conventional choice in the art, as long as the Keggin-type heteropoly acid can be loaded on the carrier, for example, an impregnation method, a kneading method, a coating method, etc. can be used. Preferably, the loading method includes: contacting ammonium-modified diatomaceous earth with a heteropolyacid solution, and then calcining the solid phase product obtained by the contact to obtain a catalyst.

[0042] According to the present invention, preferably, the contact temperature is not higher than 150°C, more preferably 40-100°C, and the contact time is 4-48h, more preferably 8-24h.

[0043] According to the present invention, preferably, the calcination temperature is 300-390° C. and the calcination time is 2-10 h.

[0044] According to the present invention, preferably, the loading method further comprises: solid-liquid separation and drying of the mixture after the ammonium-modified diatomaceous earth contacts the heteropolyacid solution, wherein the drying method can be one of rotary evaporation drying, freeze drying, oven drying and spray drying.

[0045] According to the present invention, preferably, the heteropolyacid solution contains a phosphorus source, a vanadium source and a molybdenum source; wherein the molar ratio of the phosphorus source, the vanadium source and the molybdenum source is 0.5-3:0.01-3:12, wherein the phosphorus source is calculated as phosphorus element, the vanadium source is calculated as vanadium element, and the molybdenum source is calculated as molybdenum element.

[0046] According to the present invention, the phosphorus source can be any substance that can provide phosphorus element. Preferably, the phosphorus source includes at least one of phosphoric acid, monoammonium hydrogen phosphate, diammonium hydrogen phosphate and triammonium phosphate, more preferably phosphoric acid.

[0047] According to the present invention, the vanadium source may be any substance that can provide vanadium element. Preferably, the vanadium source includes vanadium pentoxide and / or ammonium metavanadate, and more preferably vanadium pentoxide.

[0048] According to the present invention, the molybdenum source can be any substance that can provide the molybdenum element. Preferably, the molybdenum source includes at least one of molybdenum oxide, ammonium molybdate and molybdic acid, and more preferably molybdenum oxide.

[0049] According to the present invention, preferably, the heteropolyacid solution further contains component A, component B and component C, wherein the molar ratio of component A, component B and component C is 0-3:0-3:0.01-3 calculated on an element basis.

[0050] According to the present invention, preferably, component A includes at least one of an iron source, a cobalt source, a nickel source, a zinc source, a chromium source, a copper source, a magnesium source, a manganese source, a germanium source, a bismuth source, a zirconium source, a silver source, a barium source, a gallium source, a cerium source, a selenium source, a silicon source, a boron source, a tungsten source and a lanthanide metal source other than promethium.

[0051] According to the present invention, preferably, component B includes at least one of an arsenic source, a tellurium source and an antimony source.

[0052] According to the present invention, preferably, component C comprises an alkali metal source and / or an ammonium source. More preferably, the alkali metal source comprises at least one of a sodium source, a potassium source, a rubidium source and a cesium source.

[0053] In the present invention, the component A, component B and component C can be independently any substance that can provide the above-mentioned element, for example, the hydroxide, nitrate, sulfate, chloride, acetate, carbonate, oxide of the element, or an acid containing the element. The cesium source can be cesium nitrate, the copper source can be copper nitrate, the selenium source can be selenic acid, the zinc source can be zinc acetate, the antimony source can be antimony oxide, the tellurium source can be telluric acid, the germanium source can be germanium oxide, the potassium source can be potassium hydroxide, the arsenic source can be arsenic acid, and the ammonium source can be ammonium carbonate.

[0054] In the present invention, the preparation method of the heteropolyacid solution can be a conventional method in the art, for example, method 1: the method for preparing a Keggin type heteropolyacid solution comprises: heating an aqueous solution containing a phosphorus source, a vanadium source and a molybdenum source at 50-150°C (stirring in an oil bath) for 0.5-12h to obtain a Keggin type heteropolyacid solution. Method 2: the method for preparing a Keggin type heteropolyacid solution comprises: (1) heating an aqueous solution containing a phosphorus source, a vanadium source and a molybdenum source at 50-150°C (stirring in an oil bath) for 0.5-12h to obtain a solution A; (2) mixing a solution B containing component C with a solution A and heating at 50-150°C (stirring in an oil bath) for 0.5-12h to obtain a Keggin type heteropolyacid solution. Method 3: The method for preparing a Keggin-type heteropolyacid solution comprises: (1) heating an aqueous solution containing a phosphorus source, a vanadium source and a molybdenum source at 50-150°C (stirring in an oil bath) for 0.5-12 h to obtain a liquid A; (2) mixing a liquid B containing component C with a liquid A and heating them at 50-150°C (stirring in an oil bath) for 0.5-12 h to obtain a liquid C; (3) mixing a liquid D containing component A and / or component B with a liquid C and heating them at 50-150°C (stirring in an oil bath) for 0.5-12 h to obtain a Keggin-type heteropolyacid solution.

[0055] The third aspect of the present invention provides a catalyst prepared by the method described above.

[0056] The fourth aspect of the present invention provides the use of the above-mentioned catalyst and / or the catalyst prepared by the above-mentioned method in the oxidation of olefinic aldehyde to produce olefinic acid, and particularly preferably in the oxidation of methacrolein to produce methacrylic acid.

[0057] A fifth aspect of the present invention provides a method for preparing enoic acid by oxidation of enoaldehyde, the method comprising: in the presence of the above-mentioned catalyst and / or the catalyst prepared by the above-mentioned method, allowing enoaldehyde to undergo oxidation reaction to produce enoic acid.

[0058] According to the present invention, preferably, the alkenal is C3-C 10 The aldehyde is more preferably methacrolein.

[0059] According to the present invention, preferably, the oxidation reaction conditions include: a temperature of 280-320°C, a weight space velocity of olefinic aldehyde of 600-1600h -1 .

[0060] According to the present invention, preferably, the oxidant used in the oxidation reaction is oxygen.

[0061] According to the present invention, preferably, the molar ratio of the olefinic aldehyde to oxygen is 1:0.5-5.

[0062] According to the present invention, preferably, the method further comprises causing the olefinic aldehyde to undergo an oxidation reaction to generate olefinic acid in the presence of water and / or an inert gas. The inert gas may be an inert gas (e.g., at least one of helium, neon, argon and krypton) and / or nitrogen. The molar ratio of the olefinic aldehyde to water and the inert gas is 1:1.5-10:10-40.

[0063] According to the present invention, preferably, before the oxidation reaction, the catalyst is further formed. More preferably, the forming method can be a forming method commonly used in the art, for example, stamping forming, extrusion forming, spraying forming, tablet forming, granulation forming, kneading forming, etc.

[0064] According to a particularly preferred embodiment of the present invention, the method for preparing a supported heteropolyacid catalyst comprises:

[0065] (1) Add diatomite to NH4Cl solution, stir in a water bath at 70-80°C for 4-4.5 hours, filter, wash and dry to obtain a first modified diatomite. Then add the first modified diatomite to NH4Cl solution, stir in a water bath at 70-80°C for 4-4.5 hours, filter, wash and dry to obtain ammonium modified diatomite. The concentration of NH4Cl solution is 0.8-1 mol / L; in each ammonium modification process, the amount of ammonium modification reagent (NH4Cl) in terms of nitrogen element is 0.9-1 mol per 100 g of diatomite.

[0066] (2) 20-22 g of MoO3, 1.1-1.2 g of V2O5 and 1.2-1.3 g of H3PO4 are dissolved in 150-160 ml of water, and refluxed at 100-120° C. with stirring for 4-8 hours to form liquid A; 6.8-7 g of cesium nitrate is dissolved in water to form liquid B; liquid B is added dropwise to liquid A, and refluxed at 100-120° C. with stirring for 1-2 hours to obtain liquid C; 1.4-1.5 g of copper nitrate, 2-2.1 g of selenic acid, 1.3-1.4 g of zinc acetate, 3.4-3.5 g of antimony trioxide and 2.7-2.8 g of telluric acid are dissolved in water to form liquid D, and liquid D is added dropwise to liquid C, and refluxed at 100-120° C. with stirring for 5-6 hours to obtain heteropolyacid solution E.

[0067] (3) Add 33-35 g of ammonium-modified diatomaceous earth to solution E, stir at 60-65° C. for 12-15 h, and then dry and calcine at 370-380° C. for 3-4 h.

[0068] The present invention will be described in detail below by way of examples. In the following examples,

[0069] The reaction products were detected by gas chromatography, and the conversion of methacrolein and the selectivity of methacrylic acid were calculated;

[0070] Methacrolein conversion rate (%) = the number of moles of methacrolein consumed in the reaction / the number of moles of methacrolein added to the reactor × 100%;

[0071] Selectivity of methacrylic acid (%) = the number of moles of methacrylic acid generated in the reaction / the number of moles of methacrolein consumed in the reaction × 100%;

[0072] The specific surface area of ​​diatomaceous earth is 45m 2 / g, the content of silicon dioxide in diatomaceous earth is 99.7% by weight.

[0073] The specific surface areas of the catalysts in the following examples were obtained by nitrogen adsorption and desorption testing.

[0074] The ammonium content in the ammonium-modified diatomaceous earth is obtained by thermogravimetric analysis. The specific test method is to weigh 15 mg of ammonium-modified diatomaceous earth, put it into a thermogravimetric instrument, and raise the temperature to 800°C at a rate of 10°C per minute, wherein the weight loss between 300°C and 600°C is the ammonium content.

[0075] Example 1

[0076] (1) Add diatomaceous earth to NH4Cl solution, stir in a water bath at 70°C for 4 hours, filter, wash and dry to obtain a first-modified diatomaceous earth. Then add the first-modified diatomaceous earth to NH4Cl solution, stir in a water bath at 70°C for 4 hours, filter, wash and dry to obtain ammonium-modified diatomaceous earth. The concentration of NH4Cl solution is 1 mol / L; in each ammonium modification process, the amount of ammonium modification reagent (NH4Cl) used in terms of nitrogen element is 1 mol per 100 g of diatomaceous earth.

[0077] (2) 20.0 g MoO3, 1.1 g V2O5 and 1.3 g H3PO4 were dissolved in 150 ml deionized water, and refluxed at 100 °C with stirring for 8 h to form liquid A; 6.8 g cesium nitrate was dissolved in 20 ml deionized water to form liquid B; liquid B was added dropwise to liquid A, and refluxed at 100 °C with stirring for 1 h to obtain liquid C; 1.4 g copper nitrate, 2.1 g selenic acid, 1.3 g zinc acetate, 3.4 g antimony trioxide and 2.7 g telluric acid were dissolved in 40 ml water to form liquid D, and liquid D was added dropwise to liquid C, and refluxed at 100 °C with stirring for 5 h to obtain heteropolyacid solution E.

[0078] (3) Add 35g of ammonium-modified diatomaceous earth to liquid E, stir at 60°C for 12h, then evaporate to dryness by rotary evaporation, calcine (calcine at 380°C for 4h), tablet, and sieve to obtain a 20-40 mesh heteropoly acid@diatomaceous earth catalyst. The catalyst composition is Cs3Cu 0.5 Se 0.5 Zn 0.5 Sb2TePMo 12 V@diatomite, wherein the Keggin-type heteropoly acid content in the catalyst, the specific surface area of ​​the catalyst, the average pore size of the mesopores, and the percentage of the pore volume occupied by the mesopores in the total pore volume are shown in Table 1. The SEM image of the catalyst is shown in Figure 1 As shown by Figure 1 It can be seen that the heteropoly acid presents irregular particle morphology; the nitrogen adsorption-desorption curve of the catalyst is as follows Figure 2 As shown by Figure 2 It can be seen that the curve has an obvious hysteresis loop, indicating that there are certain mesopores in the catalyst.

[0079] (4) 3 g of the catalyst was loaded into a fixed bed reactor of a stainless steel tube with a diameter of 10 mm and a length of 800 mm, and the reaction was carried out at 310° C. and normal pressure. The molar ratio of methacrolein: oxygen: water: nitrogen was 1:2.5:4:15, and the reaction space velocity of methacrolein was 1100 h -1 The methacrolein conversion and methacrylic acid selectivity after the reaction was carried out for 6 h and 100 h are shown in Table 1, respectively.

[0080] Example 2

[0081] (1) Add diatomite to NH4NO3 solution, stir in a water bath at 100°C for 12 hours, filter, wash and dry to obtain a first-modified diatomite. Then add the first-modified diatomite to NH4NO3 solution, stir in a water bath at 100°C for 12 hours, filter, wash and dry to obtain ammonium-modified diatomite. The concentration of the NH4NO3 solution is 1 mol / L; in each ammonium modification process, the amount of ammonium modification reagent (NH4NO3) used in terms of nitrogen element is 2 mol per 100 g of diatomite.

[0082] (2) 20.0 g MoO3, 1.1 g V2O5 and 1.3 g H3PO4 were dissolved in 150 ml deionized water, and refluxed at 100 °C with stirring for 8 h to form liquid A; 4.5 g cesium nitrate was dissolved in 20 ml deionized water to form liquid B; liquid B was added dropwise to liquid A, and refluxed at 100 °C with stirring for 1 h to obtain liquid C; 1.4 g copper nitrate, 1.7 g antimony trioxide and 2.7 g telluric acid were dissolved in 30 ml water to form liquid D, and liquid D was added dropwise to liquid C, and refluxed with stirring for 5 h, and refluxed at 100 °C with stirring for 5 h to obtain heteropolyacid solution E.

[0083] (3) 10 g of ammonium-modified diatomaceous earth was added to liquid E, stirred at 100 ° C for 4 h, then evaporated to dryness, calcined (at 350 ° C for 3 h), pressed into tablets, and sieved to obtain a 20-40 mesh heteropoly acid @ diatomaceous earth catalyst. The catalyst composition is Cs2Cu 0.5 SbTeP 12 V@diatomite. The Keggin heteropoly acid content in the catalyst, the specific surface area of ​​the catalyst, the average pore diameter of the mesopores, and the percentage of the pore volume occupied by the mesopores in the total pore volume are shown in Table 1.

[0084] (4) 3 g of the catalyst was loaded into a fixed bed reactor of a stainless steel tube with a diameter of 10 mm and a length of 800 mm, and the reaction was carried out at 320° C. and normal pressure. The molar ratio of methacrolein: oxygen: water: nitrogen was 1:2:2:10, and the reaction space velocity of methacrolein was 600 h -1 The methacrolein conversion and methacrylic acid selectivity after the reaction was carried out for 6 h and 100 h are shown in Table 1, respectively.

[0085] Example 3

[0086] (1) Add diatomaceous earth to (NH4)2SO4 solution, stir in a water bath at 25°C for 48 hours, filter, wash and dry to obtain a first-modified diatomaceous earth. Then add the first-modified diatomaceous earth to (NH4)2SO4 solution, stir in a water bath at 25°C for 48 hours, filter, wash and dry to obtain ammonium-modified diatomaceous earth. The concentration of the (NH4)2SO4 solution is 0.1 mol / L; in each ammonium modification process, the amount of ammonium modification reagent used in terms of nitrogen element is 0.2 mol per 100 g of diatomaceous earth.

[0087] (2) 20.0 g MoO3, 1.1 g V2O5 and 1.3 g H3PO4 were dissolved in 150 ml deionized water, and refluxed at 100 °C with stirring for 8 h to form liquid A; 4.5 g cesium nitrate was dissolved in 20 ml deionized water to form liquid B; liquid B was added dropwise to liquid A, and the mixture was refluxed at 100 °C with stirring for 1 h to obtain liquid C; 1.3 g zinc acetate, 0.6 g germanium oxide and 3.4 g antimony trioxide were dissolved in 20 ml water to form liquid D, and liquid D was added dropwise to liquid C, and the mixture was refluxed at 100 °C with stirring for 5 h to obtain heteropolyacid solution E.

[0088] (3) 70 g of ammonium-modified diatomaceous earth was added to liquid E, stirred at 40 ° C for 48 h, then evaporated to dryness, calcined (calcined at 390 ° C for 2 h), pressed into tablets, and sieved to obtain a 20-40 mesh heteropoly acid @ diatomaceous earth catalyst. The catalyst composition is Cs2Zn 0.5 Ge 0.5 Sb2P 12 V@diatomite. The Keggin heteropoly acid content in the catalyst, the specific surface area of ​​the catalyst, the average pore diameter of the mesopores, and the percentage of the pore volume occupied by the mesopores in the total pore volume are shown in Table 1.

[0089] (4) 3 g of the catalyst was loaded into a fixed bed reactor of a stainless steel tube with a diameter of 10 mm and a length of 800 mm, and the reaction was carried out at 308° C. and normal pressure. The molar ratio of methacrolein: oxygen: water: nitrogen was 1:4:6:30, and the reaction space velocity of methacrolein was 1600 h -1 The methacrolein conversion and methacrylic acid selectivity after the reaction was carried out for 6 h and 100 h are shown in Table 1, respectively.

[0090] Example 4

[0091] (1) Add diatomite to NH4NO3 solution, stir in a water bath at 70°C for 4 hours, filter, wash and dry to obtain a first-modified diatomite. Then add the first-modified diatomite to NH4NO3 solution, stir in a water bath at 70°C for 4 hours, filter, wash and dry to obtain ammonium-modified diatomite. The concentration of the NH4NO3 solution is 1 mol / L; in each ammonium modification process, the amount of ammonium modification reagent used in terms of nitrogen element is 1 mol per 100 g of diatomite.

[0092] (2) 20.0 g MoO3, 1.1 g V2O5 and 1.3 g H3PO4 were dissolved in 150 ml deionized water, and refluxed at 100 °C with stirring for 8 h to form liquid A; 4.5 g cesium nitrate and 0.7 g potassium hydroxide were dissolved in 20 ml deionized water to form liquid B; liquid B was added dropwise to liquid A, and the mixture was refluxed at 100 °C with stirring for 1 h to obtain liquid C; 5.6 g copper nitrate and 4.9 g arsenic acid were dissolved in 30 ml water to form liquid D, and liquid D was added dropwise to liquid C, and the mixture was refluxed at 100 °C with stirring for 5 h to obtain heteropolyacid solution E.

[0093] (3) 20 g of ammonium-modified diatomaceous earth was added to liquid E, stirred at 40 ° C for 48 h, then evaporated to dryness, calcined (at 380 ° C for 4 h), tableted, and sieved to obtain a 20-40 mesh heteropoly acid @ diatomaceous earth catalyst, the catalyst composition of which is KCs2Cu2As3PMo 12 V@diatomite. The Keggin heteropoly acid content in the catalyst, the specific surface area of ​​the catalyst, the average pore diameter of the mesopores, and the percentage of the pore volume occupied by the mesopores in the total pore volume are shown in Table 1.

[0094] (4) 3 g of the catalyst was loaded into a fixed bed reactor of a stainless steel tube with a diameter of 10 mm and a length of 800 mm, and the reaction was carried out at 305° C. and normal pressure. The molar ratio of methacrolein: oxygen: water: nitrogen was 1:2:5:16, and the reaction space velocity of methacrolein was 1205 h -1 The methacrolein conversion and methacrylic acid selectivity after the reaction was carried out for 6 h and 100 h are shown in Table 1, respectively.

[0095] Example 5

[0096] (1) According to step (1) of Example 1, ammonium-modified diatomaceous earth was prepared.

[0097] (2) 20.0 g MoO3, 1.1 g V2O5 and 1.3 g H3PO4 were dissolved in 150 ml deionized water, and refluxed at 100 °C with stirring for 8 h to form liquid A; 2.3 g cesium nitrate and 1.3 g potassium hydroxide were dissolved in 20 ml deionized water to form liquid B; liquid B was added dropwise to liquid A, and the mixture was refluxed at 100 °C with stirring for 1 h to obtain liquid C; 8.4 g copper nitrate and 5.3 g telluric acid were dissolved in 30 ml water to form liquid D, and liquid D was added dropwise to liquid C, and the mixture was refluxed at 100 °C with stirring for 5 h to obtain heteropolyacid solution E.

[0098] (3) 20 g of ammonium-modified diatomaceous earth was added to liquid E, stirred at 40 ° C for 48 h, then evaporated to dryness, calcined (at 380 ° C for 4 h), tableted, and sieved to obtain a 20-40 mesh heteropoly acid @ diatomaceous earth catalyst, the catalyst composition of which is K2CsCu3Te2PMo 12 V@diatomite. The Keggin heteropoly acid content in the catalyst, the specific surface area of ​​the catalyst, the average pore diameter of the mesopores, and the percentage of the pore volume occupied by the mesopores in the total pore volume are shown in Table 1.

[0099] (4) 3 g of the catalyst was loaded into a fixed bed reactor of a stainless steel tube with a diameter of 10 mm and a length of 800 mm, and the reaction was carried out at 295° C. and normal pressure. The molar ratio of methacrolein: oxygen: water: nitrogen was 1:3.5:4.5:18, and the reaction space velocity of methacrolein was 905 h -1 The methacrolein conversion and methacrylic acid selectivity after the reaction was carried out for 6 h and 100 h are shown in Table 1, respectively.

[0100] Example 6

[0101] (1) According to step (1) of Example 2, ammonium-modified diatomaceous earth was prepared.

[0102] (2) 20.0 g MoO3, 1.1 g V2O5 and 1.3 g H3PO4 were dissolved in 150 ml deionized water, and refluxed at 100 °C with stirring for 8 h to form liquid A; 2.3 g cesium nitrate and 1.7 g ammonium carbonate were dissolved in 20 ml deionized water to form liquid B; liquid B was added dropwise to liquid A, and the mixture was refluxed at 100 °C with stirring for 1 h to obtain liquid C; 5.6 g copper nitrate was dissolved in 30 ml water to form liquid D, and liquid D was added dropwise to liquid C, and the mixture was refluxed at 100 °C with stirring for 5 h to obtain heteropolyacid solution E.

[0103] (3) 10 g of ammonium-modified diatomaceous earth was added to liquid E, stirred at 40°C for 48 h, then evaporated to dryness by rotary evaporation, calcined (at 380°C for 4 h), tableted, and sieved to obtain a 20-40 mesh heteropoly acid@diatomaceous earth catalyst, the catalyst composition of which is CsCu2(NH4) 1.7 PMo 12V@diatomite. The Keggin heteropoly acid content in the catalyst, the specific surface area of ​​the catalyst, the average pore diameter of the mesopores, and the percentage of the pore volume occupied by the mesopores in the total pore volume are shown in Table 1.

[0104] (4) 3 g of the catalyst was loaded into a fixed bed reactor of a stainless steel tube with a diameter of 10 mm and a length of 800 mm, and the reaction was carried out at 315° C. and normal pressure. The molar ratio of methacrolein: oxygen: water: nitrogen was 1:2.5:3.5:20, and the reaction space velocity of methacrolein was 1400 h -1 The methacrolein conversion and methacrylic acid selectivity after the reaction was carried out for 6 h and 100 h are shown in Table 1, respectively.

[0105] Example 7

[0106] (1) According to step (1) of Example 1, ammonium-modified diatomaceous earth was prepared.

[0107] (2) 20.0 g MoO3, 1.1 g V2O5 and 1.3 g H3PO4 were dissolved in 150 ml deionized water and refluxed at 100 °C with stirring for 8 h to obtain heteropolyacid solution E.

[0108] (3) 10 g of ammonium-modified diatomaceous earth was added to liquid E, stirred at 40 ° C for 48 h, then evaporated to dryness, calcined (at 380 ° C for 4 h), tableted, and sieved to obtain a 20-40 mesh heteropoly acid @ diatomaceous earth catalyst. The catalyst composition is HPMo 12 V@diatomite. The Keggin heteropoly acid content in the catalyst, the specific surface area of ​​the catalyst, the average pore diameter of the mesopores, and the percentage of the pore volume occupied by the mesopores in the total pore volume are shown in Table 1.

[0109] (4) 3 g of the catalyst was loaded into a fixed bed reactor of a stainless steel tube with a diameter of 10 mm and a length of 800 mm, and the reaction was carried out at 320° C. and normal pressure. The molar ratio of methacrolein: oxygen: water: nitrogen was 1:1.5:5.5:20, and the reaction space velocity of methacrolein was 850 h -1 The methacrolein conversion and methacrylic acid selectivity after the reaction was carried out for 6 h and 100 h are shown in Table 1, respectively.

[0110] Comparative Example 1

[0111] (1) According to step (2) of Example 1, a heteropoly acid solution E was prepared, and then rotary evaporated to dryness, calcined, and pressed into tablets to obtain a heteropoly acid catalyst Cs3Cu 0.5 Se 0.5 Zn 0.5 Sb2TePMo 12 V, standby.

[0112] (2) 3 g of the catalyst was loaded into a fixed bed reactor of a stainless steel tube with a diameter of 10 mm and a length of 800 mm, and the reaction was carried out at 310° C. and normal pressure. The molar ratio of methacrolein: oxygen: water: nitrogen was 1:2.5:4:15, and the reaction space velocity of methacrolein was 1100 h -1 The conversion of acrolein and the selectivity of methacrylic acid after the reaction was carried out for 6 h and 100 h are shown in Table 1, respectively.

[0113] Comparative Example 2

[0114] The method of Example 5 was followed, except that the ammonium-modified diatomaceous earth was replaced with an equal weight of silicon oxide.

[0115] Comparative Example 3

[0116] The method of Example 1 is followed, except that step (1), i.e., adding the unammonium-modified diatomaceous earth to liquid E, is not included.

[0117] Comparative Example 4

[0118] The method of Example 1 is followed, except that in step (1), NH4Cl is replaced by N-[3-(trimethoxysilyl)propyl]ethylenediamine, and the amount of N-[3-(trimethoxysilyl)propyl]ethylenediamine used is half the molar amount of NH4Cl.

[0119] Comparative Example 5

[0120] The method of Example 1 is followed, except that NH4Cl is replaced by ethylenediamine, and the amount of ethylenediamine used is half the molar number of NH4Cl.

[0121] Table 1

[0122]

[0123] Note: V 介 / V 总 It indicates the percentage of the pore volume occupied by mesopores in the catalyst to the total pore volume.

[0124] It can be seen from the results in Table 1 that, compared with the comparative example, the catalyst of the embodiment of the present invention still has a higher methacrolein conversion rate and methacrylic acid selectivity after 100 hours of reaction; while the methacrolein conversion rate of the catalysts of comparative examples 1-5 has dropped to less than 60% and the methacrylic acid selectivity has dropped to less than 52% after 18 hours of reaction, indicating that the catalyst of the present invention has excellent stability.

[0125] By comparing Comparative Example 2 with Example 5 of the present invention, it can be seen that, under the condition of the same Keggin-type heteropolyacid content, Example 5 of the present invention can not only maintain a high methacrolein conversion rate and methacrylic acid selectivity after 100 hours, but also has a high methacrolein conversion rate and methacrylic acid selectivity in the initial reaction period (within 6 hours of reaction).

[0126] Preferably, Examples 1, 5 and 7 of the present invention use the same ammonium-modified diatomaceous earth as a carrier. When the Keggin-type heteropoly acid in Example 1 is used, the stability of the catalyst and the initial conversion rate and selectivity of the catalyst can be further improved.

[0127] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A supported heteropolyacid catalyst, characterized in that The catalyst comprises a carrier and a heteropoly acid loaded on the carrier, wherein the carrier is ammonium-modified diatomaceous earth, and the heteropoly acid comprises phosphorus, vanadium and molybdenum.

2. The catalyst according to claim 1, wherein The composition of the heteropoly acid is A a B b C c P x V y Mo 12 O z , wherein P, V, Mo, and O represent phosphorus, vanadium, molybdenum, and oxygen, respectively; A is at least one of iron, cobalt, nickel, zinc, chromium, copper, magnesium, manganese, germanium, bismuth, zirconium, silver, barium, gallium, cerium, selenium, silicon, boron, tungsten, and lanthanide elements other than promethium; B is at least one of arsenic, tellurium, and antimony; C is an alkali metal element and / or NH4 + ; a, b, c, x, y and z are the atomic ratios of the elements, wherein a is 0-3, b is 0-3, c is 0-3, preferably 0.01-3, x is 0.5-3, y is 0.01-3, and z is the atomic ratio of oxygen element required to satisfy the valence of the above components; Preferably, the alkali metal element includes at least one of sodium, potassium, rubidium and cesium.

3. The catalyst according to claim 1, wherein The specific surface area of ​​the catalyst is 20-60m 2 / g; And / or, the average pore size of the mesopores in the catalyst is 3.0-4.6 nm, and the pore volume occupied by the mesopores accounts for 90-100% of the total pore volume; and / or, the content of ammonium in the carrier is 1-5% by weight; And / or, based on the total weight of the catalyst, the content of the carrier is 20-70 wt %, and the content of the heteropolyacid is 30-80 wt %.

4. A method for preparing a supported heteropolyacid catalyst, characterized in that: The method includes: (1) contacting diatomaceous earth with an ammonium modification reagent to react to obtain ammonium-modified diatomaceous earth; wherein the ammonium modification reagent is an inorganic salt containing nitrogen; (2) A heteropoly acid is supported on ammonium-modified diatomaceous earth, wherein the heteropoly acid contains phosphorus, vanadium and molybdenum.

5. The method according to claim 4, wherein: The specific surface area of ​​the diatomaceous earth is 35-65m 2 / g, and / or, the silicon oxide content in the diatomaceous earth is 65-100 wt %; And / or, the inorganic salt containing nitrogen element includes at least one of ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium carbonate, ammonium bicarbonate and ammonium monohydrogen phosphate; Preferably, the amount of the ammonium modification agent used is 0.1-4 mol in terms of nitrogen element per 100 g of diatomaceous earth; Preferably, the ammonium modification reagent is in the form of a solution and is contacted with diatomaceous earth to carry out the ammonium modification reaction. More preferably, the concentration of the ammonium modification reagent in the ammonium modification reagent solution is 0.1-2 mol / L.

6. The method according to claim 4, wherein: The conditions of the ammonium modification reaction include: temperature of 25-100° C. and time of 4-96 hours.

7. The method according to claim 4, wherein: In step (2), the amounts of ammonium-modified diatomaceous earth and heteropolyacid used are such that the content of heteropolyacid in the obtained catalyst is 30-80% by weight, and the content of ammonium-modified diatomaceous earth is 20-70% by weight.

8. The method according to claim 4, wherein: The loading method includes: contacting ammonium-modified diatomaceous earth with a heteropolyacid solution, and then calcining the solid phase product obtained by the contact to obtain a catalyst; Preferably, the contact temperature is not higher than 150°C, preferably 40-100°C, and the contact time is 4-48h, preferably 8-24h; Preferably, the calcination temperature is 300-390°C and the calcination time is 2-10h; Preferably, the heteropolyacid solution contains a phosphorus source, a vanadium source and a molybdenum source; wherein the molar ratio of the phosphorus source, the vanadium source and the molybdenum source is 0.5-3:0.01-3:12, wherein the phosphorus source is calculated as phosphorus element, the vanadium source is calculated as vanadium element, and the molybdenum source is calculated as molybdenum element; More preferably, the heteropolyacid solution further contains component A, component B and component C, wherein the molar ratio of component A, component B and component C, calculated as elements, is 0-3:0-3:0.01-3; component A includes at least one of an iron source, a cobalt source, a nickel source, a zinc source, a chromium source, a copper source, a magnesium source, a manganese source, a germanium source, a bismuth source, a zirconium source, a silver source, a barium source, a gallium source, a cerium source, a selenium source, a silicon source, a boron source, a tungsten source and a lanthanide metal source other than promethium; component B includes at least one of an arsenic source, a tellurium source and an antimony source; component C includes an alkali metal source and / or an ammonium source; preferably, the alkali metal source includes at least one of a sodium source, a potassium source, a rubidium source and a cesium source.

9. The catalyst prepared by the method according to any one of claims 4 to 8.

10. Use of the catalyst according to any one of claims 1 to 3 and 9 and / or the catalyst prepared by the method according to any one of claims 4 to 8 in the oxidation of olefinic aldehydes to produce olefinic acid, particularly preferably in the oxidation of methacrolein to produce methacrylic acid.

11. A method for preparing enoic acid by oxidation of enoaldehyde, characterized in that: The method comprises: in the presence of the catalyst described in any one of claims 1 to 3 and 9 and / or the catalyst prepared by the method described in any one of claims 4 to 8, allowing olefinic aldehyde to undergo oxidation reaction to generate olefinic acid; Preferably, the alkenal is methacrolein; Preferably, the oxidation reaction conditions include: a temperature of 280-320°C, a weight space velocity of olefinic aldehyde of 600-1600h -1 .

Images