A sulfur-doped catalyst, a preparation method and application thereof

Abstract

This invention relates to the field of catalyst preparation technology, specifically to a sulfur-doped catalyst, its preparation method, and its application. The catalyst comprises an active catalyst component and a support. The active catalyst component is a sulfur-doped Mo-V-W-Cu-Sb pentagonal metal oxide powder, with the general formula Mo… 12 V a W b Cu c Sb d S e O x In the formula, a, b, c, d, and e represent the atomic ratios of each element, where a = 1~5, b = 0.5~2.5, c = 0.5~3, d = 0~1.5, and e = 0.05~2. This invention utilizes the large atomic radius and low electronegativity of sulfur atoms to improve the electron cloud structure of the active center of the Mo-V-W-Cu-Sb pentagonal metal oxide catalyst, thereby enhancing the catalyst's selectivity for acrylic acid, lowering the oxidation reaction initiation temperature, and extending the catalyst lifetime. Simultaneously, the in-situ addition of sulfur enhances the catalyst's sulfur resistance.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation technology, specifically to a sulfur-doped catalyst, its preparation method, and its application. Background Technology

[0002] Acrylic acid is an important organic chemical raw material, widely used in the production of polyacrylates, superabsorbent resins, flocculants, dispersants, and other polymer materials. It plays an irreplaceable role in coatings, textiles, building materials, and water treatment. Currently, the mainstream industrial process for producing acrylic acid involves a two-step oxidation of propylene from acrolein. The second step, "oxidation of acrolein to acrylic acid," is the key step determining the yield and purity of the main product. The core of this reaction lies in the development of highly active and selective catalysts.

[0003] In existing technologies, the catalysts for the oxidation of acrolein to acrylic acid are mainly molybdenum-vanadium (Mo-V) metal oxide catalysts. Simultaneously, key auxiliary agents such as tungsten (W), copper (Cu), and antimony (Sb) are introduced to synergistically regulate catalyst performance, ensuring catalyst activity, selectivity, and lifespan. Specifically, Mo-V acts as the catalyst matrix, forming the core active phase and providing lattice oxygen responsible for the activation of C–H bonds and the insertion of O atoms in acrolein. W is doped into the Mo-V lattice, improving the catalyst's thermal stability, anti-sintering ability, and mechanical strength. Cu and Mo form CuMoO4, increasing the acidic sites on the catalyst surface, enhancing the adsorption and activation of acrolein, while also improving redox cycle capability and increasing acrylic acid selectivity. Sb acts as a structural auxiliary agent, stabilizing the active phase, inhibiting the aggregation and loss of active components, and fine-tuning the catalyst surface acidity and oxygen migration rate to reduce deep oxidation and improve resistance to coking.

[0004] Existing technologies, such as invention patents CN101328116B, CN101274279B, CN101507927B, CN102451702B, and CN112547082B, incorporate heteroatoms such as alkaline earth metals, Nb, Te, Ce, La, Nd, Sm, Cs, and Ge during catalyst preparation to improve the acidity of the catalyst surface and the redox capacity of the active centers, thereby enhancing catalyst activity and acrylic acid selectivity. Furthermore, invention patent CN106881101B discloses a method using elemental silicon as a diluent to improve the thermal conductivity of the catalyst, avoid surface hotspots, and enhance catalyst activity and selectivity. Invention patent CN114425382B discloses a method utilizing the excellent binding properties and thermal stability of AlPO4 to improve the dispersibility and stability of the active phase of the catalyst, thereby increasing acrylic acid selectivity. Patent CN112439441B discloses a method of incorporating high-strength powders such as potassium titanate and silicon nitride into the catalyst raw powder to improve catalyst strength.

[0005] The aforementioned patents provide numerous methods for improving the catalytic activity, structural stability, and selectivity of the Mo-VW-Cu-Sb pentagonal metal oxide system in the oxidation of acrolein to acrylic acid. However, in practical applications, drawbacks remain, such as long preparation processes, expensive raw materials, and impacts on product distribution or catalyst stability. Therefore, providing a highly efficient catalyst with a low activation temperature and long stability has promising market application prospects. Furthermore, in the propylene oxidation to acrylic acid reaction, the total sulfide content in the raw materials must be below 5 ppm to avoid catalyst sulfur poisoning, which results in high initial material purification costs for industrial plants. Therefore, a catalyst with strong sulfur resistance is beneficial for reducing raw material requirements, thereby lowering production costs. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing Mo-VW-Cu-Sb pentagonal metal oxide catalyst systems in the oxidation of acrolein to acrylic acid, such as long preparation process, expensive raw materials, and impact on product distribution or catalyst stability. This invention provides an in-situ doping method using non-metallic sulfur, utilizing the larger atomic radius and lower electronegativity of sulfur atoms to improve the electron cloud structure of the active center of the Mo-VW-Cu-Sb pentagonal metal oxide catalyst, thereby enhancing the selectivity for acrylic acid, lowering the oxidation reaction initiation temperature, and extending the catalyst lifetime. Simultaneously, the in-situ introduction of sulfur during catalyst synthesis improves the catalyst's sulfur resistance.

[0007] In a first aspect, the present invention provides a sulfur-doped catalyst comprising a catalyst active component and a support, wherein the catalyst active component is a sulfur-doped Mo-VW-Cu-Sb pentagonal metal oxide powder, having the general formula Mo 12 V a W b Cu c Sb d S e O x In the formula, a, b, c, d, and e represent the atomic ratios of each element, where a = 1~5, b = 0.5~2.5, c = 0.5~3, d = 0~1.5, and e = 0.05~2.

[0008] In some preferred embodiments, the carrier is selected from at least one of silicon carbide microspheres, aluminum nitride microspheres, pure silicon microspheres, alumina microspheres, and silicon oxide microspheres.

[0009] Secondly, the present invention provides a method for preparing a sulfur-doped catalyst, comprising the following steps:

[0010] S1. Calculate the feed ratio of each raw material using the target catalyst, dissolve some of the Mo, V, W, Cu, and Sb metal salts and sulfur-containing raw materials in deionized water, and carry out a hydrothermal reaction to obtain aqueous slurry I.

[0011] S2. Dissolve the remaining Mo, V, W, Cu, and Sb metal salts in deionized water and carry out a hydrothermal reaction to obtain aqueous slurry II;

[0012] S3. Pour aqueous slurry I into aqueous slurry II, heat and stir to obtain precursor slurry; spray dry the precursor slurry to obtain solid powder, and calcine to obtain catalyst active raw powder.

[0013] S4. Mix and coat the catalyst active powder with the support, and spray atomized binder to obtain the catalyst precursor.

[0014] S5. The catalyst precursor is dried, cooled, and calcined to obtain the catalyst.

[0015] In some preferred embodiments, the metal salt of Mo is selected from at least one of ammonium molybdate and ammonium paramolybdate; the metal salt of V is selected from at least one of vanadium oxalate and ammonium metavanadate; the metal salt of W is selected from at least one of ammonium tungstate, ammonium paratungstate, and ammonium metatungstate; the metal salt of Cu is selected from at least one of copper carbonate, copper nitrate, copper sulfate, basic copper sulfate, copper acetate, copper oxalate, and copper phosphate; the metal salt of Sb is selected from at least one of antimony acetate and antimony oxide; and the sulfur-containing raw material is selected from at least one of ammonium sulfate, ammonium thiosulfate, thiourea, and thioacetamide.

[0016] In some preferred embodiments, in S1, the amount of the Mo, V, W, Cu, and Sb metal salts fed is 5 to 30 wt% of the total amount fed.

[0017] In some preferred embodiments, in S1, the hydrothermal reaction is carried out continuously at 75~110°C for 3~8 hours.

[0018] In some preferred embodiments, in S2, the hydrothermal reaction is carried out continuously at 75~110°C for 1~4 hours.

[0019] In some preferred embodiments, in S3, the heating and stirring conditions are a continuous reaction at 75~110°C for 1~4 hours.

[0020] In some preferred embodiments, in S3, the spray drying processing conditions are: inlet temperature 120~180℃, outlet temperature 70~100℃.

[0021] In some preferred embodiments, in S3, the calcination conditions are to heat to 200-400°C at a heating rate of 3-8°C / min and maintain the temperature for 6-8 hours.

[0022] In some preferred embodiments, the binder is selected from an aqueous solution of at least one of hydroxypropyl methylcellulose, methylcellulose, ethylcellulose, and microcrystalline cellulose.

[0023] In some preferred embodiments, the mass ratio of the catalyst active powder to the support is (100-150):200.

[0024] In some preferred embodiments, in S5, the drying conditions are hot air drying at 80~150℃ for 2~5 hours, and the calcination conditions are heating to 300~450℃ at a heating rate of 2~4℃ / min and holding for 3~6 hours.

[0025] Thirdly, this invention provides an application of a sulfur-doped catalyst for the catalytic oxidation of acrolein to prepare acrylic acid.

[0026] Compared with existing technologies, the beneficial effects are as follows:

[0027] 1. This invention utilizes the large atomic radius and low electronegativity of sulfur atoms to improve the active center electron cloud structure of the Mo-VW-Cu-Sb pentagonal metal oxide catalyst, thereby enhancing the acrylic acid selectivity of the catalyst, reducing the oxidation reaction initiation temperature, and extending the catalyst lifetime.

[0028] 2. The present invention specifically introduces sulfur element in situ during the catalyst synthesis stage, thereby improving the catalyst's sulfur resistance performance. Attached Figure Description

[0029] Figure 1 This is a comparison diagram of the bed temperature distribution of the catalysts in Example 1 and Comparative Example 1.

[0030] Figure 2 XPS spectra of Cu element in the catalysts of Example 1 and Comparative Example 1.

[0031] Figure 3 The image shows the XRD pattern of the catalyst in Example 1.

[0032] Figure 4 This is a SEM mapping image of the catalyst in Example 1.

[0033] Figure 5 The spherical catalyst for the oxidation of acrolein to acrylic acid prepared in Example 1. Detailed Implementation

[0034] The present invention can be better understood through the following examples.

[0035] Example 1: Mo 12 V4W 2.2 Cu2Sb 0.8 S 0.5 O x Preparation of (STL-R2-S0.5)

[0036] S1. Heat 200 mL of deionized water to 95℃, and add 5.50 g ammonium heptamolybdate, 1.21 g ammonium metavanadate, 1.41 g ammonium metatungstate, 1.25 g copper nitrate, 0.62 g antimony triacetate and 0.99 g thiourea in sequence. Stir continuously for 3 hours to obtain a uniform aqueous slurry I.

[0037] S2. Add 49.50 g ammonium heptamolybdate, 10.93 g ammonium metavanadate, 12.66 g ammonium metatungstate, 11.29 g copper nitrate and 5.59 g antimony triacetate sequentially to 300 mL of deionized water at 95℃, and stir continuously for 1 hour to obtain slurry II.

[0038] S3. Slowly add slurry I dropwise into slurry II, and continuously stir at 95°C for 1 hour to obtain a precursor slurry; after cooling the precursor slurry to 40°C, spray dry it, controlling the inlet air temperature at 130°C and adjusting the feeding rate to maintain the outlet temperature at 96°C; collect the product from the cyclone separator, and calcine it in an air atmosphere at 390°C for 6 hours to obtain a catalyst active powder, the general formula of which is Mo. 12 V4W 2.2 Cu2Sb 0.8 S 0.5 O x ;

[0039] S4. Take 120 g of catalyst active powder and 200 g of spherical α-alumina support and put them into a centrifugal granulation and coating machine for rolling, while spraying cellulose aqueous solution for coating, to obtain catalyst precursor;

[0040] S5. The catalyst precursor was dried at 90℃ for 2 hours, cooled, and then heated to 390℃ at a rate of 5℃ / min, and calcined for 6 hours to obtain the finished catalyst, denoted as STL-R2-S0.5. Its reaction bed distribution diagram and XPS spectrum are shown below. Figure 1 and 2 XRD patterns, SEM images, and physical images are shown below. Figures 3-5 .

[0041] Example 2: Mo 12 V4W 2.2 Cu2Sb 0.8 S 0.2 O x Preparation of (STL-R2-S0.2)

[0042] S1. Heat 200 mL of deionized water to 95℃, and add 5.50 g ammonium heptamolybdate, 1.21 g ammonium metavanadate, 1.41 g ammonium metatungstate, 1.25 g copper nitrate, 0.62 g antimony triacetate and 0.40 g thiourea in sequence. Stir continuously for 3 hours to obtain a uniform aqueous slurry I.

[0043] S2. Add 49.50 g ammonium heptamolybdate, 10.93 g ammonium metavanadate, 12.66 g ammonium metatungstate, 11.29 g copper nitrate and 5.59 g antimony triacetate sequentially to 300 mL of deionized water at 95℃, and stir continuously for 1 hour to obtain slurry II.

[0044] S3. Slowly add slurry I dropwise into slurry II, and continuously stir at 95°C for 1 hour to obtain a precursor slurry; after cooling the precursor slurry to 40°C, spray dry it, controlling the inlet air temperature at 130°C and adjusting the feeding rate to maintain the outlet temperature at 96°C; collect the product from the cyclone separator, and calcine it in an air atmosphere at 390°C for 6 hours to obtain a catalyst active powder, the general formula of which is Mo. 12 V4W 2.2 Cu2Sb 0.8 S 0.2 O x ;

[0045] S4. Take 120 g of catalyst active powder and 200 g of spherical α-alumina support and put them into a centrifugal granulation and coating machine for rolling, while spraying cellulose aqueous solution for coating, to obtain catalyst precursor;

[0046] S5. The catalyst precursor is dried at 90℃ for 2 hours, cooled, and then heated to 390℃ at a heating rate of 5℃ / min. After calcination for 6 hours, the catalyst product is obtained and is denoted as STL-R2-S0.2.

[0047] Example 3: Mo 12 V4W 2.2 Cu2Sb 0.8 S 0.5 O x Preparation of (STL-R2-S0.5-15)

[0048] S1. Heat 200 mL of deionized water to 95℃, and add 8.25 g ammonium heptamolybdate, 1.82 g ammonium metavanadate, 2.11 g ammonium metatungstate, 1.88 g copper nitrate, 0.93 g antimony triacetate and 0.99 g thiourea in sequence. Stir continuously for 3 hours to obtain a uniform aqueous slurry I.

[0049] S2. Add 46.75 g ammonium heptamolybdate, 10.33 g ammonium metavanadate, 11.96 g ammonium metatungstate, 10.66 g copper nitrate and 5.28 g antimony triacetate sequentially to 300 mL of deionized water at 95℃, and stir continuously for 1 hour to obtain slurry II.

[0050] S3. Slowly add slurry I dropwise into slurry II, and continuously stir at 95°C for 1 hour to obtain a precursor slurry; after cooling the precursor slurry to 40°C, spray dry it, controlling the inlet air temperature at 130°C and adjusting the feeding rate to maintain the outlet temperature at 96°C; collect the product from the cyclone separator, and calcine it in an air atmosphere at 390°C for 6 hours to obtain a catalyst active powder, the general formula of which is Mo. 12 V4W 2.2 Cu2Sb 0.8 S 0.5 O x ;

[0051] S4. Take 120 g of catalyst active powder and 200 g of spherical α-alumina support and put them into a centrifugal granulation and coating machine for rolling, while spraying cellulose aqueous solution for coating, to obtain catalyst precursor;

[0052] S5. The catalyst precursor is dried at 90°C for 2 hours, cooled, and then heated to 390°C at a heating rate of 5°C / min. After calcination for 6 hours, the catalyst product is obtained and is denoted as STL-R2-S0.5-15, where 15 indicates that the amount of the corresponding metal salts of Mo, V, W, Cu and Sb in step S1 is 15wt% of the total amount of feed.

[0053] Example 4: Mo 12 V4W 2.2 Cu2Sb 0.8 SO x Preparation of (STL-R2-S1.0)

[0054] S1. Heat 200 mL of deionized water to 95℃, and add 5.50 g ammonium heptamolybdate, 1.21 g ammonium metavanadate, 1.41 g ammonium metatungstate, 1.25 g copper nitrate, 0.62 g antimony triacetate and 1.98 g thiourea in sequence. Stir continuously for 3 hours to obtain a uniform aqueous slurry I.

[0055] S2. Add 49.50 g ammonium heptamolybdate, 10.93 g ammonium metavanadate, 12.66 g ammonium metatungstate, 11.29 g copper nitrate and 5.59 g antimony triacetate sequentially to 300 mL of deionized water at 95℃, and stir continuously for 1 hour to obtain slurry II.

[0056] S3. Slowly add slurry I dropwise into slurry II, and continuously stir at 95°C for 1 hour to obtain a precursor slurry; after cooling the precursor slurry to 40°C, spray dry it, controlling the inlet air temperature at 130°C and adjusting the feeding rate to maintain the outlet temperature at 96°C; collect the product from the cyclone separator, and calcine it in an air atmosphere at 390°C for 6 hours to obtain a catalyst active powder, the general formula of which is Mo. 12 V4W 2.2 Cu2Sb 0.8 SO x ;

[0057] S4. Take 120 g of catalyst active powder and 200 g of spherical α-alumina support and put them into a centrifugal granulation and coating machine for rolling, while spraying cellulose aqueous solution for coating, to obtain catalyst precursor;

[0058] S5. The catalyst precursor is dried at 90℃ for 2 hours, cooled, and then heated to 390℃ at a heating rate of 5℃ / min. After calcination for 6 hours, the catalyst product is obtained and is designated as STL-R2-S1.0.

[0059] Example 5: Mo 12 V4W 2.2 Cu2Sb 0.8 S 0.5 O x Preparation of (STL-R2-S0.5-AS)

[0060] S1. Heat 200 mL of deionized water to 95℃, and add 5.50 g ammonium heptamolybdate, 1.21 g ammonium metavanadate, 1.41 g ammonium metatungstate, 1.25 g copper nitrate, 0.62 g antimony triacetate and 1.72 g ammonium sulfate in sequence. Stir continuously for 3 hours to obtain a uniform aqueous slurry I.

[0061] S2. Add 49.50 g ammonium heptamolybdate, 10.93 g ammonium metavanadate, 12.66 g ammonium metatungstate, 11.29 g copper nitrate and 5.59 g antimony triacetate sequentially to 300 mL of deionized water at 95℃, and stir continuously for 1 hour to obtain slurry II.

[0062] S3. Slowly add slurry I dropwise into slurry II, and continuously stir at 95°C for 1 hour to obtain a precursor slurry; after cooling the precursor slurry to 40°C, spray dry it, controlling the inlet air temperature at 130°C and adjusting the feeding rate to maintain the outlet temperature at 96°C; collect the product from the cyclone separator, and calcine it in an air atmosphere at 390°C for 6 hours to obtain a catalyst active powder, the general formula of which is Mo. 12 V4W 2.2 Cu2Sb 0.8 S 0.5 Ox ;

[0063] S4. Take 120 g of catalyst active powder and 200 g of spherical α-alumina support and put them into a centrifugal granulation and coating machine for rolling, while spraying cellulose aqueous solution for coating, to obtain catalyst precursor;

[0064] S5. The catalyst precursor is dried at 90℃ for 2 hours, cooled, and then heated to 390℃ at a heating rate of 5℃ / min. After calcination for 6 hours, the catalyst product is obtained, denoted as STL-R2-S0.5-AS, where AS represents ammonium sulfate.

[0065] Example 6: Mo 12 V4W 2.2 Cu2Sb 0.8 S 0.5 O x Preparation of (STL-R2-S0.5-ATS)

[0066] S1. Heat 200 mL of deionized water to 95℃, and add 5.50 g ammonium heptamolybdate, 1.21 g ammonium metavanadate, 1.41 g ammonium metatungstate, 1.25 g copper nitrate, 0.62 g antimony triacetate and 0.96 g ammonium thiosulfate in sequence. Stir continuously for 3 hours to obtain a uniform aqueous slurry I.

[0067] S2. Add 49.50 g ammonium heptamolybdate, 10.93 g ammonium metavanadate, 12.66 g ammonium metatungstate, 11.29 g copper nitrate and 5.59 g antimony triacetate sequentially to 300 mL of deionized water at 95℃, and stir continuously for 1 hour to obtain slurry II.

[0068] S3. Slowly add slurry I dropwise into slurry II, and continuously stir at 95°C for 1 hour to obtain a precursor slurry; after cooling the precursor slurry to 40°C, spray dry it, controlling the inlet air temperature at 130°C and adjusting the feeding rate to maintain the outlet temperature at 96°C; collect the product from the cyclone separator, and calcine it in an air atmosphere at 390°C for 6 hours to obtain a catalyst active powder, the general formula of which is Mo. 12 V4W 2.2 Cu2Sb 0.8 S 0.5 O x ;

[0069] S4. Take 120 g of catalyst active powder and 200 g of spherical α-alumina support and put them into a centrifugal granulation and coating machine for rolling, while spraying cellulose aqueous solution for coating, to obtain catalyst precursor;

[0070] S5. The catalyst precursor is dried at 90℃ for 2 hours, cooled, and then heated to 390℃ at a heating rate of 5℃ / min. After calcination for 6 hours, the catalyst product is obtained, which is denoted as STL-R2-S0.5-ATS, where ATS represents ammonium thiosulfate.

[0071] Example 7: Mo 12 V4W 2.2 Cu2Sb 0.8 S 0.5 O x Preparation of (STL-R2-S0.5-CuS)

[0072] S1. Heat 200 mL of deionized water to 95℃, and add 5.50 g ammonium heptamolybdate, 1.21 g ammonium metavanadate, 1.41 g ammonium metatungstate, 0.58 g copper sulfate, 0.62 g antimony triacetate and 0.99 g thiourea in sequence. Stir continuously for 3 hours to obtain a uniform aqueous slurry I.

[0073] S2. Add 49.50 g ammonium heptamolybdate, 10.93 g ammonium metavanadate, 12.66 g ammonium metatungstate, 5.21 g copper sulfate and 5.59 g antimony triacetate sequentially to 300 mL of deionized water at 95℃, and stir continuously for 1 hour to obtain slurry II.

[0074] S3. Slowly add slurry I dropwise into slurry II, and continuously stir at 95°C for 1 hour to obtain a precursor slurry; after cooling the precursor slurry to 40°C, spray dry it, controlling the inlet air temperature at 130°C and adjusting the feeding rate to maintain the outlet temperature at 96°C; collect the product from the cyclone separator, and calcine it in an air atmosphere at 390°C for 6 hours to obtain a catalyst active powder, the general formula of which is Mo. 12 V4W 2.2 Cu2Sb 0.8 S 0.5 O x ;

[0075] S4. Take 120 g of catalyst active powder and 200 g of spherical α-alumina support and put them into a centrifugal granulation and coating machine for rolling, while spraying cellulose aqueous solution for coating, to obtain catalyst precursor;

[0076] S5. The catalyst precursor is dried at 90℃ for 2 hours, cooled, and then heated to 390℃ at a heating rate of 5℃ / min. After calcination for 6 hours, the catalyst product is obtained, denoted as STL-R2-S0.5-CuS, where CuS represents copper sulfate.

[0077] Comparative Example 1: Mo 12 V4W 2.2 Cu2Sb 0.8 Ox Preparation of (STL-R2-S0*)

[0078] S1. Heat 500 mL of deionized water to 95℃, and add 55.00 g of ammonium heptamolybdate, 12.14 g of ammonium metavanadate, 14.07 g of ammonium metatungstate, 12.54 g of copper nitrate and 6.21 g of antimony triacetate in sequence. Stir continuously for 4 hours to obtain a uniform aqueous slurry.

[0079] S2. After the above aqueous slurry cools to 40°C, it is spray-dried, with the inlet air temperature controlled at 130°C and the feeding rate adjusted to maintain the outlet temperature at 96°C. The product from the cyclone separator is collected and calcined in air at 390°C for 6 hours to obtain the catalyst active powder, whose elemental ratio is given by the general formula Mo. 12 V4W 2.2 Cu2Sb 0.8 O x ;

[0080] S3. Take 120 g of catalyst active powder and 200 g of spherical α-alumina support and put them into a centrifugal granulation and coating machine for rolling, while spraying cellulose aqueous solution for coating, to obtain catalyst precursor;

[0081] S4. The catalyst precursor was dried at 90℃ for 2 hours, cooled, and then heated to 390℃ at a rate of 5℃ / min, and calcined for 6 hours to obtain the finished catalyst, denoted as STL-R2-S0*. Its reaction bed distribution diagram and XPS spectrum are shown below. Figure 1 and 2 .

[0082] Comparative Example 2: Mo 12 V4W 2.2 Cu2Sb 0.8 O x Preparation of (STL-R2-S0-CuS*)

[0083] S1. Heat 500 mL of deionized water to 95℃, and add 55.00 g of ammonium heptamolybdate, 12.14 g of ammonium metavanadate, 14.07 g of ammonium metatungstate, 5.79 g of copper sulfate and 6.21 g of antimony triacetate in sequence. Stir continuously for 4 hours to obtain a uniform aqueous slurry.

[0084] S2. After the above mixed slurry cools to 40°C, it is spray-dried, with the inlet air temperature controlled at 130°C and the feeding rate adjusted to maintain the outlet temperature at 96°C. The product in the cyclone separator is collected and calcined in air at 390°C for 6 hours to obtain the catalyst active powder, whose elemental ratio is given by the general formula Mo. 12 V4W 2.2 Cu2Sb 0.8 Ox ;

[0085] S3. Take 120 g of catalyst active powder and 200 g of spherical α-alumina support and put them into a centrifugal granulation and coating machine for rolling, while spraying cellulose aqueous solution for coating, to obtain catalyst precursor;

[0086] S4. The catalyst precursor is dried at 90°C for 2 hours, cooled, and then heated to 390°C at a heating rate of 5°C / min. After calcination for 6 hours, the catalyst product is obtained, denoted as STL-R2-S0-CuS*, where CuS represents copper sulfate.

[0087] Comparative Example 3: Mo 12 V4W 2.2 Cu2Sb 0.8 S 0.5 O x Preparation of (STL-R2-S0.5*)

[0088] S1. Heat 500 mL of deionized water to 95℃, and add 55.00 g of ammonium heptamolybdate, 12.14 g of ammonium metavanadate, 14.07 g of ammonium metatungstate, 12.54 g of copper nitrate, 6.21 g of antimony triacetate, and 0.99 g of thiourea in sequence. Stir continuously for 4 hours to obtain a uniform aqueous slurry.

[0089] S2. After the above aqueous slurry cools to 40°C, it is spray-dried, with the inlet air temperature controlled at 130°C and the feeding rate adjusted to maintain the outlet temperature at 96°C. The product from the cyclone separator is collected and calcined in air at 390°C for 6 hours to obtain the catalyst active powder, whose elemental ratio is given by the general formula Mo. 12 V4W 2.2 Cu2Sb 0.8 S 0.5 O x ;

[0090] S3. Take 120 g of catalyst active powder and 200 g of spherical α-alumina support and put them into a centrifugal granulation and coating machine for rolling, while spraying cellulose aqueous solution for coating, to obtain catalyst precursor;

[0091] S4. The catalyst precursor is dried at 90℃ for 2 hours, cooled, and then heated to 390℃ at a heating rate of 5℃ / min. After calcination for 6 hours, the catalyst product is obtained and is denoted as STL-R2-S0.5*.

[0092] Performance testing

[0093] 1. Catalyst performance evaluation

[0094] The experiment was conducted in a side-stream reaction tube containing two fixed beds. The first fixed bed was used for in-situ generation of acrolein, and the second fixed bed was used to test the catalysts prepared in Examples 1-7 and Comparative Examples 1-3. The specific reaction conditions were: propylene / water / air1 / nitrogen / air2 = 1 / 1.00 / 8.13 / 2.40 / 2.39, and the propylene space velocity in the first fixed bed was 90 h⁻¹. -1 The propylene concentration was 8.0%, the inlet pressure was 40 kPa, and the temperature was 330℃; the outlet pressure of the second-stage fixed bed was 20 kPa, and the reaction temperature was 255-260℃. Gas chromatography was used to analyze the reaction performance of the second-stage fixed bed, and the specific results are shown in Table 1 below.

[0095] Table 1. Comparison of catalytic performance between Examples 1-7 and Comparative Examples 1-3

[0096]

[0097] As shown in Table 1, Examples 1, 2, 4 and Comparative Example 1, adding non-metallic sulfur to the Mo-VW-Cu-Sb pentagonal metal oxide can lower the catalyst reaction temperature. With a 5°C decrease in reaction temperature, the catalyst's conversion rate of acrolein increased from 98.11% to 99.98%, and the yield of acrylic acid increased from 90.25% to 97.89%. Figure 1 It can be seen that the hot spot temperature distribution of catalyst STL-R2-S0.5 is effectively reduced compared with catalyst STL-R2-S0*, with the highest temperature decreasing from 295.7℃ to 284.1℃. This feature can effectively extend the service life of the catalyst.

[0098] pass Figure 2 It can be seen that the binding energy of Cu decreases after doping with S, which is beneficial to increasing the catalytic activity. Meanwhile, Comparative Example 2 shows that replacing copper nitrate with copper sulfate in the reaction system can also lower the reaction temperature and increase the acrylic acid yield by 92.77%, but it does not effectively reduce the catalyst hotspot and cannot flexibly change the S content in the catalyst system. Comparative Example 3 shows that in the catalyst synthesis process, using the "one-pot method" to synthesize the target catalyst resulted in not only a high catalyst bed hotspot temperature, but also an acrylic acid yield of only 86.46%, indicating the necessity of a stepwise method for catalyst preparation.

[0099] As can be seen from Examples 1 and 3, increasing the separation ratio of the Mo-VW-Cu-Sb pentagonal metal salt from 10% to 15% has little impact on the catalyst activity.

[0100] Examples 1, 5, and 6 show that different sulfur raw materials have strong universality for the Mo-VW-Cu-Sb pentagonal metal oxide catalyst, but thiourea has the best effect and can achieve the best reaction conditions.

[0101] As can be seen from Examples 1 and 7, using thiourea as a sulfur dopant, copper sulfate raw material cannot improve the catalyst performance.

[0102] 2. Catalyst Sulfur Resistance Experiment

[0103] Example 1 and Comparative Example 1 were compared using the same two-stage fixed-bed reactor as the catalyst evaluation experiment, except that the propylene introduced into the reactor contained trace amounts of SO2. The experimental results are shown in Table 2.

[0104] Table 2 Comparison of sulfur resistance performance between Example 1 and Comparative Example 1

[0105]

[0106] Table 2 shows that when the SO2 content in the reactants increased from 0 to 100 ppm, the acrolein conversion rate of catalyst STL-R2-S0.5 remained between 98.77% and 99.98%, and the acrylic acid yield remained between 96.72% and 97.89%. Catalyst STL-R2-S0*, however, showed a significant negative correlation; that is, when the SO2 content increased to 10 ppm, the acrolein conversion rate and acrylic acid yield decreased slightly; further increasing the SO2 content to 50 ppm or even 100 ppm significantly reduced both the acrolein conversion rate and acrylic acid yield, reaching a minimum of less than 50%. This indicates that actively introducing sulfur during the synthesis of the Mo-VW-Cu-Sb pentagonal metal oxide can improve the catalyst's sulfur resistance.

Claims

1. A sulfur-doped catalyst comprising a catalyst active component and a support, characterized in that, The catalyst active component is a sulfur-doped Mo-VW-Cu-Sb pentagonal metal oxide powder with the general formula Mo. 12 V a W b Cu c Sb d S e O x In the formula, a, b, c, d, and e represent the atomic ratios of each element, where a = 1~5, b = 0.5~2.5, c = 0.5~3, d = 0~1.5, and e = 0.05~2.

2. The catalyst according to claim 1, characterized in that, The carrier is selected from at least one of silicon carbide microspheres, aluminum nitride microspheres, pure silicon microspheres, alumina microspheres, and silicon oxide microspheres.

3. A method for preparing a sulfur-doped catalyst according to any one of claims 1-2, characterized in that, Includes the following steps: S1. Calculate the feed ratio of each raw material using the target catalyst, dissolve some of the Mo, V, W, Cu, and Sb metal salts and sulfur-containing raw materials in deionized water, and carry out a hydrothermal reaction to obtain aqueous slurry I. S2. Dissolve the remaining Mo, V, W, Cu, and Sb metal salts in deionized water and carry out a hydrothermal reaction to obtain aqueous slurry II; S3. Pour aqueous slurry I into aqueous slurry II, heat and stir to obtain precursor slurry; The precursor slurry was spray-dried to obtain a solid powder, which was then calcined to obtain the catalyst active raw powder. S4. Mix and coat the catalyst active powder with the support, and spray atomized binder to obtain the catalyst precursor. S5. The catalyst precursor is dried, cooled, and calcined to obtain the catalyst.

4. The preparation method according to claim 3, characterized in that, The metal salt of Mo is selected from at least one of ammonium molybdate and ammonium paramolybdate; the metal salt of V is selected from at least one of vanadium oxalate and ammonium metavanadate; the metal salt of W is selected from at least one of ammonium tungstate, ammonium paratungstate, and ammonium metatungstate; the metal salt of Cu is selected from at least one of copper carbonate, copper nitrate, copper sulfate, basic copper sulfate, copper acetate, copper oxalate, and copper phosphate; the metal salt of Sb is selected from at least one of antimony acetate and antimony oxide; and the sulfur-containing raw material is selected from at least one of ammonium sulfate, ammonium thiosulfate, thiourea, and thioacetamide.

5. The preparation method according to claim 3, characterized in that, In S1, the amount of the Mo, V, W, Cu, and Sb metal salts fed is 5 to 30 wt% of the total amount fed.

6. The preparation method according to claim 3, characterized in that, In S3, the spray drying conditions are: inlet temperature 120~180℃, outlet temperature 70~100℃.

7. The preparation method according to claim 3, characterized in that, In S3, the calcination conditions are to heat to 200-400°C at a heating rate of 3-8°C / min and hold for 6-8 hours.

8. The preparation method according to claim 3, characterized in that, The binder is selected from an aqueous solution of at least one of hydroxypropyl methylcellulose, methylcellulose, ethylcellulose, and microcrystalline cellulose.

9. The preparation method according to claim 3, characterized in that, In S5, the drying conditions are hot air drying at 80~150℃ for 2~5 hours, and the calcination conditions are heating to 300~450℃ at a heating rate of 2~4℃ / min and holding for 3~6 hours.

10. The application of a sulfur-doped catalyst according to any one of claims 1-2, characterized in that, It is used in the catalytic oxidation of acrolein to prepare acrylic acid.

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