Oxidation catalysts, methods of making and using the same, and methods of making c3-c4 alkenoic acids

Abstract

The present application relates to the technical field of oxidation catalyst, in particular to an oxidation catalyst, a preparation method and application thereof and a preparation method of C3-C4 alkenoic acid.The oxidation catalyst provided by the present application has a ratio of surface Fe element content to total Fe element content of the catalyst <0.1, more Fe elements are sealed inside the catalyst, and the surface iron molybdate content is as low as possible;the iron molybdate compound inside the catalyst can provide more active oxygen for the reaction, and can also promote the re-oxidation of the catalyst, thereby improving the catalyst and activity.The oxidation catalyst is used for the oxidation of aldehyde to prepare acid, such as the oxidation of propenal to prepare propenoic acid, and has high propenal conversion rate and high propenoic acid yield.

Description

Technical Field

[0001] This invention relates to the field of oxidation catalyst technology, specifically to an oxidation catalyst, its preparation method and application, and a method for preparing C3-C4 olefinic acid. Background Technology

[0002] Acrylic acid, as one of the important basic chemical raw materials, is mainly used in the production of butyl acrylate and ethyl acrylate comonomers for water-soluble coatings and adhesives, as well as in the production of superabsorbent resins. The selective oxidation of propylene to produce acrylic acid is the most important method. This method currently mostly employs a two-step process. In the first reactor, propylene is oxidized to acrolein and some acrylic acid, and then in the second reactor, acrolein is further oxidized to acrylic acid. The second reactor typically uses transition metal composite oxides such as Mo, V, Sb, and Nb as catalysts (Catalysis Today 49 (1999) 141-153).

[0003] In Mo-based composite oxides, the addition of Fe significantly enhances the redox activity of the composite oxide catalyst (Applied Catalysis: A General 145, 1996). This is because Fe... 3+ Particle radius and Mo 6+ With similar ionic radii, they can enter the molybdenum-oxygen structure and replace part of the Mo. 6+ And Fe 3+ / Fe 2+ Redox pairs can significantly promote oxygen mobility, thereby enhancing catalyst activity (Applied Catalysis: A General 543, 2017). However, iron-molybdenum oxides themselves cannot selectively catalyze the oxidation of unsaturated hydrocarbons or aldehydes. Summary of the Invention

[0004] The purpose of this invention is to overcome the problem that iron-molybdenum compounds in the prior art cannot selectively catalyze the oxidation of hydrocarbons or aldehydes, and to provide an oxidation catalyst, its preparation method and application, and a method for preparing C3-C4 olefinic acids. This oxidation catalyst is used for the oxidation of aldehydes to prepare acids, such as the oxidation of acrolein to prepare acrylic acid, and has the advantages of high acrolein conversion rate and high acrylic acid yield.

[0005] To achieve the above objectives, a first aspect of the present invention provides an oxidation catalyst comprising a catalyst having the general formula VMo. a W b X c Y d Cu e Fe f Z g O jThe active component comprises, wherein X is selected from at least one of Sb, Nb, Cr and Ta, Y is selected from at least one of Li, K, Na and Rb, and Z is selected from at least one of Mg, Ba and Ca; a is the molar ratio of Mo to V, with a value of 1 to 6; b is the molar ratio of W to V, with a value of 0.3 to 1; c is the molar ratio of X to V, with a value of 0.1 to 0.6; d is the molar ratio of Y to V, with a value of 0.01 to 0.4; e is the molar ratio of Cu to V, with a value of 0.2 to 3; f is the molar ratio of Fe to V, with a value of 0.1 to 0.5; g is the molar ratio of Z to V, with a value of 0.01 to 0.5; j is the number of moles of oxygen atoms required to satisfy the valence of each element in the active component; the ratio of Fe content on the catalyst surface to the total Fe content of the catalyst is <0.1.

[0006] A second aspect of the present invention provides a method for preparing the oxidation catalyst of the present invention, the method comprising:

[0007] (1) According to the ratio, prepare solutions i containing V, W and X; prepare solutions ii containing Mo; prepare solutions iii containing Fe; and prepare solutions iv containing Y, Z and Cu.

[0008] (2) Mix solutions ii and iii to carry out a precipitation reaction to obtain slurry I; add acidic substances to adjust the pH to less than 4 and maintain it for at least 15 minutes;

[0009] (3) Then, solution i and solution iv are added to slurry I in sequence to obtain slurry II. Slurry II is concentrated, dried and calcined.

[0010] A third aspect of the present invention provides the application of the oxidation catalyst described herein in the preparation of acids from aldehydes.

[0011] A fourth aspect of this invention provides a method for preparing C3-C4 enoic acid, the method comprising:

[0012] In the presence of a catalyst, a feed gas containing C3-C4 enal is reacted with an oxygen-containing oxidizing gas, wherein the catalyst contains the oxidation catalyst described in this invention.

[0013] Through the above technical solution, the oxidation catalyst provided by the present invention has a surface Fe element content to total catalyst Fe element content ratio of <0.1, which seals more Fe elements inside the catalyst and keeps the surface iron molybdate content as low as possible; the iron-molybdenum compounds inside the catalyst can increase more active oxygen for the reaction and also promote the re-oxidation of the catalyst, thereby improving the activity of the catalyst.

[0014] The oxidation catalyst described in this invention is used for the oxidation of aldehydes to prepare acids, such as the oxidation of acrolein to prepare acrylic acid, and has the advantages of high acrolein conversion rate and high acrylic acid yield.

[0015] The reason is speculated to be that before the formation of the active phase, iron-molybdenum compounds are first precipitated under acidic conditions, avoiding the formation of ferric hydroxide and thus reducing the occurrence of side reactions. After adjusting the pH, other active components are added and thoroughly and uniformly mixed to react and coat the iron-molybdenum compounds. The iron-molybdenum compounds under the active components can increase the amount of active oxygen for the reaction and also promote the re-oxidation of the catalyst, thereby improving the catalyst activity. Detailed Implementation

[0016] The endpoints and any values ​​of the ranges disclosed herein 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 the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0017] A first aspect of the present invention provides an oxidation catalyst comprising a catalyst having the general formula VMo a W b X c Y d Cu e Fe f Z g O j The active component comprises, wherein X is selected from at least one of Sb, Nb, Cr and Ta, Y is selected from at least one of Li, K, Na and Rb, and Z is selected from at least one of Mg, Ba and Ca; a is the molar ratio of Mo to V, with a value of 1 to 6; b is the molar ratio of W to V, with a value of 0.3 to 1; c is the molar ratio of X to V, with a value of 0.1 to 0.6; d is the molar ratio of Y to V, with a value of 0.01 to 0.4; e is the molar ratio of Cu to V, with a value of 0.2 to 3; f is the molar ratio of Fe to V, with a value of 0.1 to 0.5; g is the molar ratio of Z to V, with a value of 0.01 to 0.5; j is the number of moles of oxygen atoms required to satisfy the valence of each element in the active component; the ratio of Fe content on the catalyst surface to the total Fe content of the catalyst is <0.1. The oxidation catalyst provided by this invention has a surface Fe element content to total catalyst Fe element content ratio of <0.1, which encapsulates more Fe element inside the catalyst and minimizes the surface iron molybdate content. The iron-molybdenum compounds inside the catalyst can increase more active oxygen for the reaction and also promote catalyst re-oxidation, thereby improving the stability and activity of the catalyst.

[0018] According to a preferred embodiment of the present invention, the ratio of Fe content on the catalyst surface to the total Fe content of the catalyst is greater than 0 and less than 0.05, which is beneficial to improving the activity of the catalyst.

[0019] According to a preferred embodiment of the present invention, the value of a is 2 to 4; the value of b is 0.4 to 0.7; the value of c is 0.2 to 0.5; the value of d is 0.05 to 0.2; the value of e is 0.5 to 2; the value of f is 0.2 to 0.4; and the value of g is 0.1 to 0.3, which is beneficial to improving the stability and activity of the catalyst.

[0020] Oxidation catalysts having the aforementioned composition of this invention can all achieve the objectives of this invention, and there are no special requirements for their preparation methods. Regarding this invention, according to a preferred embodiment of this invention, this invention provides a method for preparing the oxidation catalyst of this invention, the method comprising:

[0021] (1) According to the ratio, prepare solutions i containing compounds V, W and X; prepare solutions ii containing compounds Mo; prepare solutions iii containing compounds Fe; and prepare solutions iv containing compounds Y, Z and Cu.

[0022] (2) Mix solutions ii and iii to carry out a precipitation reaction to obtain slurry I; add acidic substances to adjust the pH to less than 4 and maintain it for at least 15 minutes;

[0023] (3) Then, solution i and solution iv are added to slurry I in sequence to obtain slurry II. Slurry II is concentrated, dried and calcined.

[0024] In this invention, the amount of each substance fed according to the proportions should satisfy the general formula of the catalyst of this invention.

[0025] In this invention, there are no requirements for the preparation order of solutions i-iv; they are only used to differentiate the preparation of solutions containing different components.

[0026] According to a preferred embodiment of the present invention, in step (2), an acidic substance is added to adjust the pH to 3-3.5, preferably after adjusting the pH to 3-3.5, the mixture is left to stand for 15-30 minutes under stirring.

[0027] According to a preferred embodiment of the present invention, before adding solution i and solution iv to slurry I, an alkaline substance is added to adjust the pH to be greater than 5. Preferably, after adjusting the pH to be greater than 5, the mixture is left to stand for 15 to 30 minutes under stirring conditions; more preferably, the pH is adjusted to 6-8.

[0028] In this invention, the acidic substance can be selected from a wide range of types, as long as it can be removed during the roasting process. According to a preferred embodiment of this invention, the acidic substance is selected from at least one of nitric acid and hydrochloric acid.

[0029] In this invention, the alkaline substance can be selected from a wide range of types. According to a preferred embodiment of this invention, the alkaline substance is selected from at least one of ammonia, urea, ammonium carbonate, and ammonium bicarbonate.

[0030] In this invention, there is no particular limitation on the concentration temperature of slurry II, as long as the water can be evaporated and slurry II can be concentrated. According to a preferred embodiment of the present invention, the concentration temperature is 90-110°C.

[0031] In this invention, there are no particular limitations on the drying conditions, as long as water can be removed. According to a preferred embodiment of the invention, the drying conditions include: a temperature of 70 to 160°C; the drying time can be reasonably adjusted according to actual needs, preferably 2 to 24 hours.

[0032] In this invention, the range of selectable roasting conditions is relatively wide. According to a preferred embodiment of this invention, the roasting conditions include: a temperature of 350 to 600°C; and a roasting time that is reasonably adjusted according to the roasting temperature. Preferably, the roasting time is 1 to 4 hours.

[0033] In this invention, there are no special requirements for the types of compounds containing V, W, X, Mo, Fe, Y, Z, and Cu, as long as they are soluble in water, such as at least one of their soluble salts. This invention will not describe them in detail here.

[0034] For example, the V-containing compound may include, but is not limited to, ammonium metavanadate.

[0035] According to a preferred embodiment of the present invention, the W-containing compound is selected from one or more of ammonium tungstate, tungsten trioxide, tungstic acid, sodium tungstate, and ammonium metatungstate.

[0036] According to a preferred embodiment of the present invention, the X-containing compound is selected from at least one of niobium oxalate, niobium pentoxide, niobium pentachloride, niobic acid, niobyl nitrate, antimony nitrate, antimony tartrate, and chromium trioxide.

[0037] According to a preferred embodiment of the present invention, the Mo-containing compound may be selected from, but is not limited to, one or more of: ammonium molybdate, molybdenum trioxide, molybdenum nitrate, molybdic acid, and sodium molybdate.

[0038] According to a preferred embodiment of the present invention, the Fe-containing compound may be selected from, but is not limited to, one or more of: ferric nitrate, ferric sulfate, ferric chloride, ferric oxide, and ferrous sulfate.

[0039] According to a preferred embodiment of the present invention, the Y-containing compound may be selected from, but is not limited to, one or more of potassium nitrate, rubidium nitrate, sodium nitrate, sodium sulfate, sodium chloride, sodium acetate, sodium hydroxide, lithium nitrate, and cesium nitrate.

[0040] According to a preferred embodiment of the present invention, the Z-containing compound may be selected from, but is not limited to, at least one of: magnesium nitrate, magnesium sulfate, magnesium chloride, magnesium oxide, magnesium acetate, barium nitrate, and calcium nitrate.

[0041] According to a preferred embodiment of the present invention, the Cu-containing compound may be selected from, but is not limited to, at least one of copper nitrate and copper chloride.

[0042] A third aspect of this invention provides the application of the oxidation catalyst described herein in the oxidation of aldehydes to prepare acids. According to a preferred embodiment of the invention, the aldehyde is a C3-C4 aldehyde, preferably a C3-C4 enaldehyde, and more preferably acrolein. The oxidation catalyst described herein, used in the oxidation of aldehydes to prepare acids, such as the oxidation of acrolein to prepare acrylic acid, has the advantages of high acrylic acid activity and yield, and a stable catalyst structure.

[0043] A fourth aspect of this invention provides a method for preparing C3-C4 enoic acid, the method comprising:

[0044] In the presence of a catalyst, a feed gas containing C3-C4 acrolein is reacted with an oxygen-containing oxidizing gas. The catalyst contains the oxidation catalyst described in this invention. The oxidation catalyst of this invention is used for the oxidation of C3-C4 aldehydes to acids, such as the oxidation of acrolein to acrylic acid, and has the advantages of high acrylic acid activity and yield, as well as a stable catalyst structure.

[0045] In this invention, there is no particular limitation on the type of oxygen-containing oxidizing gas. According to a preferred embodiment of the invention, the oxygen-containing oxidizing gas is one or more of oxygen and air, more preferably air.

[0046] In this invention, the conditions for the contact reaction can be selected from a wide range. According to a preferred embodiment of this invention, the contact reaction conditions include: a temperature of 200 to 400°C and a pressure of 0.01 to 0.08 MPa, where the pressure is gauge pressure.

[0047] According to a preferred embodiment of the present invention, the volumetric hourly space velocity of the feed gas is 1000–1800 h⁻¹. -1 In the raw gas, the volume ratio of C3-C4 alkenes to air is 1:(1-6).

[0048] According to a preferred embodiment of the present invention, the raw gas also contains dilutive gaseous materials.

[0049] According to a preferred embodiment of the present invention, the volume ratio of C3-C4 alkenal: air: diluent gaseous material is 1:(1.5-5):(0.5-3).

[0050] According to a preferred embodiment of the present invention, the dilutive gaseous material is water vapor.

[0051] According to a preferred embodiment of the present invention, the C3-C4 olefin is acrolein.

[0052] The present invention will be described in detail below through embodiments.

[0053] In the following examples, the catalyst evaluation conditions are as follows:

[0054] Reactor: Fixed-bed reactor, inner diameter 25 mm, reactor length 600 mm;

[0055] Catalyst: 200 grams;

[0056] Reaction temperature: 260℃;

[0057] Reaction pressure: 0.03 MPa (gauge pressure);

[0058] Acrolein: Air: Water vapor (raw material volume ratio) = 1:3:2;

[0059] Total volumetric space velocity of raw materials: 1400 h -1 ;

[0060] The reaction products were analyzed by gas chromatography (Agilent 7890A).

[0061] The conversion rate of acrolein and the yield of acrylic acid are defined as follows:

[0062] Acrolein conversion rate = (molar amount of acrolein reacted / total molar amount of acrolein added) × 100%;

[0063] Acrylic acid yield = (molar amount of acrylic acid produced / total molar amount of acrolein added) × 100%.

[0064] In the following examples, the Fe content on the catalyst surface (Fe-surface) was determined by XPS, and the normalized Fe atomic molar percentage was calculated after excluding oxygen atoms. The total Fe content of the catalyst (Fe-body) was determined by ICP, and the normalized Fe atomic molar percentage was calculated after excluding all metal elements.

[0065] Example 1

[0066] (1) Dissolve ammonium metavanadate containing 0.1 mol V, ammonium metatungstate containing 0.05 mol W, niobium oxalate containing 0.02 mol Nb, and antimony tartrate containing 0.02 mol Sb in 150 g of hot water to obtain solution i; dissolve ammonium molybdate containing 0.3 mol Mo in 100 g of hot water to obtain solution ii; dissolve ferric nitrate containing 0.03 mol Fe in 200 g of water to obtain solution iii; dissolve potassium nitrate containing 0.01 mol K, magnesium nitrate containing 0.02 mol Mg, and copper nitrate containing 0.1 mol Cu in 50 g of water to obtain solution iv.

[0067] (2) Mix solutions ii and iii to carry out a precipitation reaction to obtain slurry I. Adjust the pH of slurry I to 3.5 with HNO3 and stir for 30 minutes. Then adjust the pH to 7 with ammonia and stir for 20 minutes.

[0068] (3) Solution i and solution iv were added to slurry I in sequence to obtain slurry II. The slurry was heated to 90°C and evaporated and concentrated to a viscous consistency. After drying at 120°C for 20 hours, it was shaped and then calcined at 450°C for 2 hours to obtain the product with the composition VMo3W. 0.5 Nb 0.2 Sb 0.2 K 0.1 Cu1Fe 0.3 Mg 0.2 O g Catalyst.

[0069] Example 2

[0070] (1) Dissolve ammonium metavanadate containing 0.1 mol V, ammonium metatungstate containing 0.07 mol W, chromium trioxide containing 0.01 mol Cr, and antimony tartrate containing 0.01 mol Sb in 150 g of hot water to obtain solution i; dissolve ammonium molybdate containing 0.2 mol Mo in 100 g of hot water to obtain solution ii; dissolve ferric nitrate containing 0.02 mol Fe in 200 g of water to obtain solution iii; dissolve potassium nitrate containing 0.005 mol K, magnesium nitrate containing 0.03 mol Mg, and copper nitrate containing 0.05 mol Cu in 50 g of water to obtain solution iv.

[0071] (2) Mix solutions ii and iii to carry out a precipitation reaction to obtain slurry I. Adjust the pH of slurry I to 3.5 with HNO3 and stir for 30 minutes. Then adjust the pH to 7 with ammonia and stir for 20 minutes.

[0072] (3) Solution i and solution iv were added to slurry I in sequence to obtain slurry II. The slurry was heated to 90°C and evaporated and concentrated to a viscous consistency. After drying at 120°C for 20 hours, it was shaped and then calcined at 450°C for 2 hours to obtain a product with the composition VMo2W. 0.7 Cr 0.1 Sb0.1 K 0.05 Cu 0. 5Fe 0.2 Mg 0.3 O g Catalyst.

[0073] Example 3

[0074] (1) Dissolve ammonium metavanadate containing 0.1 mol V, ammonium metatungstate containing 0.04 mol W, niobium oxalate containing 0.03 mol Nb, and antimony tartrate containing 0.02 mol Sb in 150 g of hot water to obtain solution i; dissolve ammonium molybdate containing 0.4 mol Mo in 100 g of hot water to obtain solution ii; dissolve ferric nitrate containing 0.04 mol Fe in 200 g of water to obtain solution iii; dissolve potassium nitrate containing 0.02 mol K, magnesium nitrate containing 0.01 mol Mg, and copper nitrate containing 0.2 mol Cu in 50 g of water to obtain solution iv.

[0075] (2) Mix solutions ii and iii to carry out a precipitation reaction to obtain slurry I. Adjust the pH of slurry I to 3.5 with HNO3 and stir for 30 minutes. Then adjust the pH to 7 with ammonia and stir for 20 minutes.

[0076] (3) Solution i and solution iv were added to slurry I in sequence to obtain slurry II. The slurry was heated to 90°C and evaporated and concentrated to a viscous consistency. After drying at 120°C for 20 hours, it was shaped and then calcined at 450°C for 2 hours to obtain VMo4W. 0.4 Nb 0.3 Sb 0.2 K 0.2 Cu2Fe 0.4 Mg 0.1 O g Catalyst.

[0077] Example 4

[0078] The method is the same as in Example 1, except that in step (2), the pH of slurry I is adjusted to 2 with nitric acid and stirred for 30 minutes, then the pH is adjusted to 7 with ammonia and stirred for 20 minutes. All other conditions are the same as in Example 1. A product with the composition VMo3W is obtained. 0. 5Nb 0.2 Sb 0.2 K 0.1 Cu1Fe 0.3 Mg 0.2 O g Catalyst.

[0079] Example 5

[0080] The method is the same as in Example 1, except that in step (2), the pH of slurry I is adjusted to 3.5 with nitric acid and stirred for 30 minutes, then the pH is adjusted to 9 with ammonia and stirred for 20 minutes. All other conditions are the same as in Example 1. A product with the composition VMo3W is obtained. 0.5 Nb 0.2 Sb 0.2 K 0.1 Cu1Fe 0.3 Mg 0.2 O g Catalyst.

[0081] Example 6

[0082] (1) Dissolve ammonium metavanadate containing 0.1 mol V, ammonium metatungstate containing 0.1 mol W, and chromium trioxide containing 0.01 mol Cr in 150 g of hot water to obtain solution i; dissolve ammonium molybdate containing 0.1 mol Mo in 100 g of hot water to obtain solution ii; dissolve ferric nitrate containing 0.01 mol Fe in 200 g of water to obtain solution iii; dissolve rubidium nitrate containing 0.001 mol Rb, magnesium nitrate containing 0.02 mol Mg, calcium nitrate containing 0.03 mol Ca, and copper nitrate containing 0.02 mol Cu in 50 g of water to obtain solution iv;

[0083] (2) Mix solutions ii and iii to carry out precipitation reaction to obtain slurry I. Adjust the pH of slurry I to 4 with HNO3 and stir for 30 minutes. Then adjust the pH to 5 with ammonia and stir for 20 minutes.

[0084] (3) Solution i and solution iv were added sequentially to slurry I to obtain slurry II. The slurry was heated to 90°C and evaporated and concentrated until it became viscous. After drying at 120°C for 20 hours, it was shaped and then calcined at 450°C for 2 hours to obtain a product with the composition VMo1W1Cr. 0.1 Rb 0.01 Cu 0.2 Fe 0. 1Mg 0.2 Ca 0.3 O g Catalyst.

[0085] Example 7

[0086] (1) Dissolve ammonium metavanadate containing 0.1 mol V, ammonium metatungstate containing 0.03 mol W, and antimony tartrate containing 0.06 mol Sb in 150 g of hot water to obtain solution i; dissolve ammonium molybdate containing 0.6 mol Mo in 100 g of hot water to obtain solution ii; dissolve ferric nitrate containing 0.05 mol Fe in 200 g of water to obtain solution iii; dissolve sodium nitrate containing 0.04 mol Na, barium nitrate containing 0.001 mol Ba, and copper nitrate containing 0.3 mol Cu in 50 g of water to obtain solution iv.

[0087] (2) Mix solutions ii and iii to carry out precipitation reaction to obtain slurry I. Adjust the pH of slurry I to 4 with HNO3 and stir for 30 minutes. Then adjust the pH to 5 with ammonia and stir for 20 minutes.

[0088] (3) Solution i and solution iv were added to slurry I in sequence to obtain slurry II. The slurry was heated to 90°C and evaporated and concentrated to a viscous consistency. After drying at 120°C for 20 hours, it was shaped and then calcined at 450°C for 2 hours to obtain a product with the composition VMo6W. 0.3 Sb 0.6 Na 0.4 Cu3Fe 0.5 Ba 0.01 O g Catalyst.

[0089] Comparative Example 1

[0090] The method of Example 1 is the same, except that the active component does not contain iron, specifically:

[0091] Solution i is prepared by dissolving ammonium metavanadate (containing 0.1 mol V), ammonium molybdate (containing 0.3 mol Mo), ammonium metatungstate (containing 0.05 mol W), niobium oxalate (containing 0.02 mol Nb), and antimony tartrate (containing 0.02 mol Sb) in 150 g of hot water. Solution ii is prepared by dissolving potassium nitrate (containing 0.01 mol K), magnesium nitrate (containing 0.02 mol Mg), and copper nitrate (containing 0.1 mol Cu) in 50 g of water. Solution i and solution ii are mixed and subjected to a precipitation reaction to obtain a slurry. The slurry is heated to 90 °C, evaporated and concentrated to a viscous consistency, dried at 120 °C for 20 hours, shaped, and then calcined at 450 °C for 2 hours to obtain a product with the composition VMo3W. 0.5 Nb 0.2 Sb 0.2 K 0.1 Cu1Mg 0.2 O g Catalyst.

[0092] Comparative Example 2

[0093] The method of Example 1 differs in that, in step (2), an acidic substance is not used; instead, an alkaline substance is used to adjust the pH. Specifically:

[0094] (1) Dissolve ammonium metavanadate containing 0.1 mol V, ammonium metatungstate containing 0.05 mol W, niobium oxalate containing 0.02 mol Nb, and antimony tartrate containing 0.02 mol Sb in 150 g of hot water to obtain solution i; dissolve ammonium molybdate containing 0.3 mol Mo in 100 g of hot water to obtain solution ii; dissolve ferric nitrate containing 0.03 mol Fe in 200 g of water to obtain solution iii; dissolve potassium nitrate containing 0.01 mol K, magnesium nitrate containing 0.02 mol Mg, and copper nitrate containing 0.1 mol Cu in 50 g of water to obtain solution iv.

[0095] (2) Mix solution ii and solution iii to carry out precipitation reaction to obtain slurry I, and stir for 50 minutes.

[0096] (3) Solution i and solution iv were added to slurry I in sequence to obtain slurry II. The slurry was heated to 90°C and evaporated and concentrated to a viscous consistency. After drying at 120°C for 20 hours, it was shaped and then calcined at 450°C for 2 hours to obtain the product with the composition VMo3W. 0.5 Nb 0.2 Sb 0.2 K 0.1 Cu1Fe 0.3 Mg 0.2 O g Catalyst.

[0097] Table 1

[0098]

[0099] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An oxidation catalyst, characterized in that, The catalyst comprises a catalyst with the general formula VMo. a W b X c Y d Cu e Fe f Z g O j The active component, wherein X is selected from at least one of Sb, Nb, Cr and Ta; Y is selected from at least one of Li, K, Na, and Rb. Z is selected from at least one of Mg, Ba, and Ca; a is the molar ratio of Mo to V, and the value of a ranges from 1 to 6; b is the molar ratio of W to V, and the value of b ranges from 0.3 to 1. c is the molar ratio of X to V, and the value of c ranges from 0.1 to 0.

6. d is the molar ratio of Y to V, and the value of d ranges from 0.01 to 0.4; e is the molar ratio of Cu to V, and the value of e ranges from 0.2 to 3; f is the molar ratio of Fe to V, and the value of f ranges from 0.1 to 0.

5. g is the molar ratio of Z to V, and the value of g ranges from 0.01 to 0.

5. j represents the number of moles of oxygen atoms required to satisfy the oxidation states of each element in the active component; The ratio of Fe content on the catalyst surface to the total Fe content of the catalyst is greater than 0 and less than 0.

1. The Fe content on the catalyst surface was determined by XPS, showing the normalized molar percentage of Fe atoms excluding oxygen atoms. The total Fe content of the catalyst was determined by ICP, showing the normalized molar percentage of Fe atoms for all metal elements.

2. The oxidation catalyst according to claim 1, wherein, The ratio of Fe content on the catalyst surface to the total Fe content of the catalyst is greater than 0 and less than 0.

05.

3. The oxidation catalyst according to claim 1 or 2, wherein, The values ​​of a are 2 to 4; the values ​​of b are 0.4 to 0.7; the values ​​of c are 0.2 to 0.5; the values ​​of d are 0.05 to 0.2; the values ​​of e are 0.5 to 2; the values ​​of f are 0.2 to 0.4; and the values ​​of g are 0.1 to 0.

3.

4. A method for preparing the oxidation catalyst according to any one of claims 1-3, characterized in that, The method includes: (1) According to the ratio, prepare solutions i containing V, W and X; prepare solutions ii containing Mo; prepare solutions iii containing Fe; and prepare solutions iv containing Y, Z and Cu. (2) Mix solution ii and solution iii to carry out precipitation reaction to obtain slurry I; add acidic substance to adjust pH to less than 4 and keep it for at least 15 min; add alkaline substance to adjust pH to greater than 5, and let it stand for 15~30 minutes under stirring conditions; (3) Then add solution i and solution iv in sequence to obtain slurry II. Concentrate slurry II, dry and calcine it.

5. The preparation method according to claim 4, wherein, In step (2), an acidic substance is added to adjust the pH to 3-3.5; and / or Add an alkaline substance to adjust the pH to 6-8.

6. The preparation method according to claim 5, wherein, In step (2), after adding acidic substances to adjust the pH to 3-3.5, let it stand for 15-30 minutes with stirring.

7. The preparation method according to claim 4 or 5, wherein, The acidic substance is selected from at least one of nitric acid and hydrochloric acid; and / or The alkaline substance is selected from at least one of ammonia, urea, ammonium carbonate, and ammonium bicarbonate.

8. The preparation method according to claim 5 or 6, wherein, The concentration temperature is 90-110℃; and / or Drying conditions include: a temperature of 70~160℃; and / or a time of 2~24h; and / or The roasting conditions include: a temperature of 350~600℃; and / or a time of 1~4h.

9. The use of the oxidation catalyst according to any one of claims 1-3 in the preparation of acids by aldehyde oxidation.

10. The application according to claim 9, wherein, The aldehyde is a C3-C4 aldehyde.

11. The application according to claim 9, wherein, The aldehyde is a C3-C4 enaldehyde.

12. The application according to claim 9, wherein, The aldehyde is acrolein.

13. A method for preparing C3-C4 enoic acid, characterized in that, The method includes: In the presence of a catalyst, a feed gas containing C3-C4 aldehydes is reacted with an oxygen-containing oxidizing gas, wherein the catalyst comprises an oxidation catalyst as described in any one of claims 1-3.

14. The preparation method according to claim 13, wherein, The oxygen-containing oxidizing gas is one or more of oxygen and air; The conditions for the contact reaction include: a temperature of 200~400℃; and a pressure of 0.01~0.08MPa, wherein the pressure is gauge pressure. The volumetric space velocity of the feed gas is 1000~1800 h⁻¹ -1 In the raw gas, the volume ratio of C3-C4 alkenes to air is 1:(1~6).

15. The preparation method according to claim 14, wherein, The oxygen-containing oxidizing gas is air.

16. The preparation method according to claim 13, wherein, The raw gas also contains dilutive gaseous materials. By volume ratio, the ratio of C3-C4 alkenes to air to dilutive gaseous materials is 1:(1.5~5):(0.5~3).

17. The preparation method according to claim 16, wherein the dilutive gaseous material is water vapor.

18. The preparation method according to claim 13, wherein, C3-C4 enaldehydes are acrolein.

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