Catalyst for synthesizing pyromellitic dianhydride through durene gas-phase oxidation as well as preparation method and application of catalyst

Abstract

The invention relates to the field of catalysts, and discloses a catalyst for synthesizing pyromellitic dianhydride through durene gas-phase oxidation, the catalyst contains a molecular sieve with an AFI structure, a V element and a Ti element, and the XRD diffraction pattern of the catalyst has main diffraction characteristic peaks when 2 theta = 7.4, 12.9, 14.9, 19.8, 21.0, 22.4, 26.0, 27.4, 29.1, 30.1, 34.6, 36.1, 37.8, 39.2, 41.2, 44.1, 54.3, 56.6, 62.7, 64.0, 69.0 and 69.8. The preparation method of the catalyst comprises the steps that a vanadium source, a titanium source and raw materials used for synthesizing the molecular sieve of the AFI structure form a material to be subjected to hydrothermal crystallization, then hydrothermal crystallization and roasting are conducted, and the pH of the material to be subjected to hydrothermal crystallization is 1-4. The catalyst provided by the invention is especially suitable for oxidation synthesis of pyromellitic dianhydride from durene, and has high pyromellitic dianhydride yield. When the catalyst is used for synthesizing pyromellitic dianhydride through durene gas-phase oxidation, the yield of pyromellitic dianhydride can reach 86.2%, and a good technical effect is achieved.

Description

Technical Field

[0001] This invention relates to the field of catalysts, specifically to a catalyst for the gas-phase oxidation of mesitylene to synthesize homogeneous anhydride, its preparation method, and its application. Background Technology

[0002] With the rapid development of industries such as petroleum refining, polyester, and chemical fibers, large-scale refineries and aromatics disproportionation and isomerization units produce large quantities of C10 aromatics as byproducts. Currently, how to efficiently utilize C10 aromatic resources has become a major issue in the petrochemical industry. Pyromellitic dianhydride (PMDA) is a widely used, high-value-added fine chemical product, used as a high-temperature curing agent, matting agent, plasticizer, high-temperature insulating varnish, and adhesive. Most importantly, dianhydride is a key monomer for synthesizing high-performance polymers—polyimides. Currently, my country mainly relies on imports for high-end polyimides. To achieve a breakthrough in my country's polyimide industry, the efficient development and production of its key monomer, dianhydride, is crucial. Therefore, extracting the high-content mesitylene from refining byproducts of C10 aromatics and further processing it into high-value-added dianhydride is of great significance.

[0003] Currently, the synthesis of homohydric anhydride from mesitylene is mostly carried out via gas-phase oxidation. However, this process is a complex heterogeneous catalytic process with various side reactions, resulting in very low homohydric anhydride yields. The gas-phase oxidation method for preparing homohydric anhydride catalysts primarily uses vanadium-titanium-based spray-coated catalysts, supplemented with small amounts of auxiliary elements, to form a slurry. The active component slurry is then sprayed onto an inert support. Summary of the Invention

[0004] TiO2 has a certain impact on the yield of homogenized anhydride. Currently, the titanium dioxide phase used in industrial applications is mainly anatase TiO2. When it is used in industry, the mass yield of homogenized anhydride is far lower than the theoretical yield of homogenized anhydride.

[0005] The purpose of this invention is to overcome the problem that the mass yield of homohydric anhydride in the gas-phase oxidation of mesitylene to homohydric anhydride is far lower than the theoretical yield, and to provide a new catalyst for the gas-phase oxidation of mesitylene to homohydric anhydride. The catalyst has high catalytic activity, high homohydric anhydride yield, and stable catalyst structure.

[0006] To achieve the above objectives, a first aspect of the present invention provides a catalyst for the gas-phase oxidation of mesitylene to synthesize homohydric anhydride. The catalyst contains an AFI-structured molecular sieve, as well as V and Ti elements. The XRD diffraction pattern of the catalyst exhibits major characteristic diffraction peaks at 2θ = 7.4, 12.9, 14.9, 19.8, 21.0, 22.4, 26.0, 27.4, 29.1, 30.1, 34.6, 36.1, 37.8, 39.2, 41.2, 44.1, 54.3, 56.6, 62.7, 64.0, 69.0, and 69.8. Among these, the peaks at 2θ = 27.4, 39.2, 41.2, 44.1, 54.3, 56.6, 62.7, 64.0, 69.0, and 69.8 are attributed to rutile TiO2 diffraction peaks. The aforementioned technical solution has the advantages of high anhydride yield and stable catalyst structure.

[0007] A second aspect of this invention provides a method for preparing the catalyst described herein. The method includes forming a hydrothermal crystallization material by combining a vanadium source, a titanium source, and raw materials for synthesizing a molecular sieve with an AFI structure, followed by hydrothermal crystallization and calcination. The pH of the hydrothermal crystallization material is 1-4. The aforementioned technical solution offers advantages such as high anhydride yield and stable catalyst structure.

[0008] A third aspect of the present invention provides a catalyst obtained by the preparation method described herein.

[0009] The fourth aspect of this invention provides the application of the catalyst described herein in the synthesis of homotoluene by the oxidation of mesitylene.

[0010] The catalyst of this invention is a molecular sieve with an AFI structure, and incorporates V and Ti elements. This catalyst exhibits high catalytic activity and a high yield of homogeneous anhydride. The preparation method of the catalyst of this invention is simple, efficient, uses readily available raw materials, and is convenient and reliable. The catalyst of this invention is particularly suitable for the gas-phase oxidation of mesitylene to homogeneous anhydride, achieving a high homogeneous anhydride yield. When using the catalyst of this invention for the gas-phase oxidation of mesitylene to homogeneous anhydride, the homogeneous anhydride mass yield can reach 86.2%, achieving good technical results. Attached Figure Description

[0011] Figure 1 This is the XRD pattern of the catalyst synthesized in Example 1. Detailed Implementation

[0012] 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.

[0013] This invention provides a catalyst for the gas-phase oxidation of mesitylene to synthesize homohydric anhydride. The catalyst contains an AFI-structured molecular sieve, as well as V and Ti elements. The XRD diffraction pattern of the catalyst exhibits major characteristic diffraction peaks at 2θ = 7.4, 12.9, 14.9, 19.8, 21.0, 22.4, 26.0, 27.4, 29.1, 30.1, 34.6, 36.1, 37.8, 39.2, 41.2, 44.1, 54.3, 56.6, 62.7, 64.0, 69.0, and 69.8. Among these, the peaks at 2θ = 27.4, 39.2, 41.2, 44.1, 54.3, 56.6, 62.7, 64.0, 69.0, and 69.8 are attributed to rutile TiO2 diffraction peaks. Catalysts with the aforementioned composition and structure exhibit high catalytic activity and high anhydride yield.

[0014] In this invention, V and Ti elements serve as the main active components. This invention does not impose special requirements on the content of V and Ti elements in the catalyst. According to a preferred embodiment of this invention, the catalyst contains, by weight percentage of oxides, 1 wt%–20 wt% TiO2, 0.1 wt%–10 wt% V2O5, and 60 wt%–90 wt% AFI-structured molecular sieve. Using the aforementioned technical solution has the advantage of high anhydride yield.

[0015] In this invention, the molecular sieve with AFI structure serves as a carrier, enabling it to support the active components of the catalyst. According to this invention, the types of elements in the molecular sieve with AFI structure can be selected as needed. An exemplary embodiment is provided, but this does not limit the scope of the invention. For example, the molecular sieve with AFI structure contains Al, P, and O elements.

[0016] This invention does not have special requirements for the content of Al, P, and O elements in the catalyst. According to a preferred embodiment of this invention, the catalyst contains, by weight percentage of oxides, 30wt% to 60wt% Al₂O₃ and 30wt% to 50wt% P₂O₅. The aforementioned technical solution has the advantages of high anhydride yield and stable catalyst structure.

[0017] Catalysts having the aforementioned composition can achieve the purpose of the present invention. According to a preferred embodiment of the present invention, the catalyst of the present invention contains, by weight percentage of oxides: 0.1wt% to 10wt% V2O5, 30wt% to 60wt% Al2O3, 30wt% to 50wt% P2O5, and 1wt% to 20wt% TiO2.

[0018] According to a preferred embodiment of the present invention, the catalyst of the present invention contains, by weight percentage of oxides: 6.0 wt% to 8.5 wt% V2O5, 35 wt% to 45 wt% Al2O3, 38 wt% to 43 wt% P2O5, and 11.0 wt% to 14.5 wt% TiO2.

[0019] In this invention, Ti element exists in the form of TiO2.

[0020] This invention does not have special requirements for the specific surface area of ​​the catalyst. However, according to a preferred embodiment of this invention, the specific surface area of ​​the catalyst is 200-400 m². 2 / g. The aforementioned technical solution has the advantages of high anhydride yield and stable catalyst structure.

[0021] According to a preferred embodiment of the present invention, the catalyst of the present invention has a specific surface area of ​​280-310 m². 2 / g.

[0022] As long as the objective of this invention can be achieved, there are no special requirements for the preparation method of the catalyst of this invention. This invention provides a method for preparing a catalyst for the gas-phase oxidation of mesitylene to synthesize homogeneous anhydride. This method includes forming a hydrothermal crystallization material by combining a vanadium source, a titanium source, and raw materials for synthesizing molecular sieves with an AFI structure, followed by hydrothermal crystallization and calcination. The pH of the hydrothermal crystallization material is 1-4. Using the aforementioned technical solution has the advantages of high homogeneous anhydride yield and stable catalyst structure.

[0023] In this invention, the range of vanadium sources is relatively wide. One embodiment is illustrated by example, but this does not limit the scope of the invention. For example, the vanadium source is selected from one or more of vanadium oxysulfate, vanadium pentoxide, vanadium oxyphosphate, vanadium hydroperoxide, and vanadium oxyoxate.

[0024] According to a preferred embodiment of the present invention, the vanadium source is selected from one or more of vanadium oxysulfate and vanadium pentoxide.

[0025] In this invention, the range of titanium sources is relatively wide. One embodiment is illustrated by way of example, but it does not limit the scope of the invention. For example, the titanium source is selected from one or more of titanium tetrachloride, tetraisopropyl titanate, and tetraethyl titanate.

[0026] According to a preferred embodiment of the present invention, the titanium source is titanium tetrachloride. The aforementioned technical solution has the advantages of high anhydride yield and stable catalyst structure.

[0027] In this invention, adding the vanadium source in the form of a sol-state vanadium source yields better results. One embodiment is illustrated, but this does not limit the scope of the invention. The method for preparing the sol-state vanadium source includes the following steps:

[0028] (1) Mix the vanadium source with water to obtain a vanadium solution;

[0029] (2) Add alkali to the vanadium solution obtained in step (1) to react and generate a suspension;

[0030] (3) Add acid to the suspension in step (2) to obtain a sol-state vanadium source.

[0031] According to a preferred embodiment of the present invention, in step (1) of the present invention, there are no special requirements for the water content in the vanadium solution, and the mass ratio of V to water is 1:(5-20), for example, the mass ratio of V to water is 1:5, 1:8, 1:10, 1:12, 1:14, 1:16, 1:18, 1:20.

[0032] According to a preferred embodiment of the present invention, in step (1), the mixing temperature is 10-80°C, for example, the mixing temperature is 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, or 80°C.

[0033] In step (1) of the present invention, the addition of an auxiliary agent is beneficial to the dispersion of the vanadium source. The range of auxiliary agents is relatively wide. According to a preferred embodiment of the present invention, the auxiliary agent is selected from one or more of oxalic acid, citric acid, and tartaric acid.

[0034] According to a preferred embodiment of the present invention, the molar ratio of the additive to V in the vanadium source is 1:(0.5-1), for example, the molar ratio of the additive to V in the vanadium source is 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, or 1:1.

[0035] In step (2) of this invention, the purpose of adding alkali is to adjust the pH of the mixture to 4-8, for example, adding alkali to adjust the pH of the mixture to 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, or 8. The range of alkalis that can be selected is relatively wide. According to a preferred embodiment of this invention, the alkali is selected from one or more of sodium hydroxide, potassium hydroxide, and ammonia water.

[0036] According to a preferred embodiment of the present invention, the reaction temperature in step (2) is 10-80°C, for example, the reaction temperature is 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, or 80°C.

[0037] In step (3) of this invention, the purpose of adding acid is to dissolve the precipitate in the suspension obtained in step (2) to obtain a sol-state vanadium source. The range of acids that can be selected is relatively wide. According to a preferred embodiment of this invention, the acid includes one or more of sulfuric acid and nitric acid, such as 50wt% sulfuric acid or 60wt% sulfuric acid.

[0038] According to a preferred embodiment of the present invention, the molar ratio of the amount of acid to the V element in the vanadium source in step (3) is 1:(0.5 to 2.0), for example, the molar ratio of the amount of acid to the V element in the vanadium source in step (3) is 1:0.5, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.8, or 1:2.0.

[0039] According to a preferred embodiment of the present invention, the reaction temperature in step (3) is 10-80°C, for example, the reaction temperature is 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, or 80°C.

[0040] The catalyst preparation method described in this invention is simple, the raw materials used are readily available, and it has good application prospects.

[0041] As long as the purpose of this invention can be achieved, there are no special requirements for the elemental composition of the molecular sieve with AFI structure in the catalyst. For example, the molecular sieve with AFI structure contains Al, P and O elements.

[0042] According to a preferred embodiment of the present invention, the catalyst preparation method of the present invention includes: forming a material to be hydrothermally crystallized from a vanadium source, an aluminum source, a phosphorus source, a titanium source, water, and a template agent, followed by hydrothermal crystallization and calcination. The aforementioned technical solution has the advantages of high anhydride yield and stable catalyst structure.

[0043] As long as the objective of this invention can be achieved, there are no special requirements for the amount of each substance used in the catalyst preparation process. According to a preferred embodiment of this invention, the vanadium source is calculated as V2O5, the aluminum source as Al2O3, the phosphorus source as P2O5, and the titanium source as TiO2. The weight ratio of vanadium source: aluminum source: phosphorus source: titanium source: template agent: water is (0.01~0.35):1:(0.5~1.3):(0.03~0.7):(1~5):(30~200). Using the aforementioned technical solution has the advantages of high anhydride yield and stable catalyst structure.

[0044] According to a preferred embodiment of the present invention, the vanadium source is calculated as V2O5, the aluminum source as Al2O3, the phosphorus source as P2O5, and the titanium source as TiO2, and the weight ratio of vanadium source: aluminum source: phosphorus source: titanium source: template agent: water is (0.1~0.25):1:(0.9~1.2):(0.2~0.5):(1~2):(35~50).

[0045] In this invention, the range of aluminum sources is relatively wide. One embodiment is illustrated by example, but this does not limit the scope of the invention. For example, the aluminum source is selected from one or more of boehmite, aluminum isopropoxide, aluminum nitrate, and aluminum hydroxide.

[0046] According to a preferred embodiment of the present invention, the aluminum source is selected from one or more of boehmite and aluminum isopropoxide.

[0047] In this invention, the range of phosphorus sources is relatively wide. One embodiment is illustrated by way of example, but it does not limit the scope of the invention. For example, the phosphorus source is selected from one or more of phosphoric acid, ammonium dihydrogen phosphate, pyrophosphate, and phosphorous acid.

[0048] According to a preferred embodiment of the present invention, the phosphorus source is phosphoric acid.

[0049] In this invention, the template agent can be selected from a wide range of options. One embodiment is illustrated by way of example, but it does not limit the scope of the invention. For example, the template agent is selected from one or more of triethylamine, tri-n-propylamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, pentaerythritol, tetramethylammonium bromide, and tetraethylammonium bromide.

[0050] According to a preferred embodiment of the present invention, the template agent is selected from a mixture of triethylamine and pentaerythritol, and the molar ratio of the two is 0.5-10:1.

[0051] According to a preferred embodiment of the present invention, the hydrothermal crystallization temperature is 150–200°C. The aforementioned technical solution has the advantages of high anhydride yield and stable catalyst structure.

[0052] According to a preferred embodiment of the present invention, the crystallization temperature is 180–200°C.

[0053] According to a preferred embodiment of the present invention, the crystallization time is 8–48 hours. The aforementioned technical solution has the advantages of high anhydride yield and stable catalyst structure.

[0054] According to a preferred embodiment of the present invention, the crystallization time is 10 to 24 hours.

[0055] After hydrothermal crystallization, the product is filtered, washed, dried, and then calcined. Filtering, washing, and drying are conventional steps in this field and can be performed according to existing technology. The drying time and temperature can be selected as needed, for example, the drying time is 3-5 hours and the drying temperature is 90-120℃.

[0056] The purpose of calcination is to remove the template agent from the molecular sieve and improve the crystallinity and structural stability of the catalyst. According to a preferred embodiment of the present invention, the calcination temperature is 650-750℃. The aforementioned technical solution has the advantages of high anhydride yield and stable catalyst structure.

[0057] According to a preferred embodiment of the present invention, the calcination time is 2-10 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours. The aforementioned technical solution has the advantages of high anhydride yield and stable catalyst structure.

[0058] This invention provides the application of the catalyst described herein in the synthesis of homotoluene by the oxidation of mesitylene.

[0059] The catalyst of this invention is particularly suitable for the oxidation of mesitylene to homohydric anhydride. Specifically, this invention provides the application of the catalyst described herein in the oxidation of mesitylene to homohydric anhydride, wherein the mass concentration of mesitylene is 15–45 g / m³. 3 For example, the mass concentration of mesitylene is 15 g / m³. 3 20g / m 3 25g / m 3 30g / m 3 35g / m 3 40g / m 3 45g / m 3 Volumetric hourly space velocity is 4000–8000 hr. -1 For example, a volumetric hourly space velocity of 4000 hr -1 5000hr -1 6000hr -1 7000hr -1 8000hr -1 The reaction temperature is 330–500℃, for example, 330℃, 350℃, 380℃, 400℃, 420℃, 450℃, 480℃, and 500℃; the reaction pressure is atmospheric pressure.

[0060] The catalyst described in this invention is highly active and yields a high homohydric anhydride when applied to the oxidation of mesitylene to homohydric anhydride.

[0061] The catalyst described in this invention employs a molecular sieve with an AFI structure and incorporates V and Ti elements, exhibiting excellent performance in the gas-phase oxidation of mesitylene to homohydric anhydride, resulting in a high homohydric anhydride yield. When using the catalyst described in this invention for the gas-phase oxidation of mesitylene to homohydric anhydride, the homohydric anhydride yield can reach 86.2 wt%, achieving good technical results.

[0062] The crystal structure of the catalyst was analyzed using a Rigaku D / max-1400 powder X-ray diffractometer (XRD) of Cu Kα (λ = 0.15406 nm), with an operating current of 200 mA, an operating voltage of 40 kV, a scanning range of 5°–80°, and a scanning rate of 12°·min. -1 .

[0063] The BET specific surface area of ​​the catalyst was measured using a Micrometrics ASAP-2010 physical adsorption instrument manufactured by Micrometrics Instruments, employing a low-temperature nitrogen adsorption method.

[0064] Example 1

[0065] (1) Weigh vanadium oxysulfate VOSO4 at 50℃, disperse it in water at a mass ratio of V to water of 1:10, stir and dissolve for 2 hours to obtain vanadium solution.

[0066] (2) At 70°C, sodium hydroxide was added to the vanadium solution obtained in step (1) to adjust the pH value to 6, and the reaction was allowed to stand for 2 hours to obtain a precipitate.

[0067] (3) At 70°C, add 50wt% sulfuric acid solution to the suspension obtained in step (2) at a sulfuric acid:V molar ratio of 1:1, mix for 2 hours to allow the precipitate to redissolve and obtain a sol-state V source.

[0068] Using triethylamine as template agent R, aluminum isopropoxide as aluminum source, phosphoric acid as phosphorus source, titanium tetrachloride as titanium source, and a sol-state V source as V source, a catalyst was prepared. The catalyst was fed in a ratio of V₂O₅:Al₂O₃:P₂O₅:TiO₂:R:H₂O = 0.15:1:1:0.3:1.5:45, and the pH was adjusted to 2 with nitric acid. The catalyst was then crystallized at 200℃ for 16 h, filtered, washed, dried at 110℃ for 4 h, and calcined in a muffle furnace at 700℃ for 6 h to obtain the catalyst.

[0069] The XRD pattern of the obtained catalyst is shown in the figure. Figure 1As shown in the figure, the molecular sieve in the catalyst is an AFI structure molecular sieve. The catalyst exhibits major diffraction characteristic peaks at 2θ = 7.4, 12.9, 14.9, 19.8, 21.0, 22.4, 26.0, 27.4, 29.1, 30.1, 34.6, 36.1, 37.8, 39.2, 41.2, 44.1, 54.3, 56.6, 62.7, 64.0, 69.0, and 69.8. Among these, the peaks at 2θ = 27.4, 39.2, 41.2, 44.1, 54.3, 56.6, 62.7, 64.0, 69.0, and 69.8 are attributed to the diffraction peaks of rutile TiO2. Simultaneously, the pore structure of the catalyst was analyzed, and the specific surface area of ​​the catalyst was measured to be 280 m². 2 / g.

[0070] The resulting catalyst contains, by weight percentage of oxides, 12.2 wt% TiO2, 6.1 wt% V2O5, 40.8 wt% Al2O3, and 40.8 wt% P2O5.

[0071] Next, using mesitylene and air as raw materials, a fixed-bed reactor was used to prepare homogenate in the presence of a catalyst at a reaction temperature of 420°C and a gas hourly space velocity of 5000 h⁻¹. -1 Raw material feed concentration 20g / m³ 3 The yield of anhydride was measured to be 85.1%.

[0072] Example 2

[0073] (1) At 50℃, vanadium pentoxide (V2O5) was weighed and dispersed in water at a mass ratio of V to water of 1:10. Oxalic acid was added at a molar ratio of auxiliary agent to V of 1:0.8. The mixture was stirred and dissolved for 2 hours to obtain a vanadium solution.

[0074] (2) At 70°C, sodium hydroxide was added to the solution obtained in step (1) to adjust the pH value to 5.5, and the reaction was allowed to stand for 2 hours to obtain a precipitate.

[0075] (3) At 70°C, add 50wt% sulfuric acid to the suspension obtained in step (2) at a sulfuric acid:V molar ratio of 1:1 and mix for 2 hours to allow the precipitate to redissolve and obtain a sol-state V source.

[0076] Triethylamine was used as the template agent R, boehmite as the aluminum source, phosphoric acid as the phosphorus source, titanium tetrachloride as the titanium source, and a sol-state V source was prepared as the V source. The catalyst was fed in a ratio of V₂O₅:Al₂O₃:P₂O₅:TiO₂:R:H₂O = 0.2:1:1.1:0.3:1.5:45, and the pH was adjusted to 3 with nitric acid. The catalyst was then crystallized at 190°C for 24 h, filtered, washed, dried at 100°C for 4 h, and calcined in a muffle furnace at 650°C for 6 h to obtain the catalyst. The XRD pattern of the obtained catalyst was similar to that of Example 1. The pore structure of the catalyst was analyzed, and the specific surface area was measured to be 304 m². 2 / g.

[0077] The resulting catalyst contains, by weight percentage of oxides, 11.5 wt% TiO2, 7.7 wt% V2O5, 38.5 wt% Al2O3, and 42.3 wt% P2O5.

[0078] Next, using mesitylene and air as raw materials, a fixed-bed reactor was used to prepare homogenate in the presence of a catalyst at a reaction temperature of 420°C and a gas hourly space velocity of 5000 h⁻¹. -1 Raw material feed concentration 20g / m³ 3 The yield of anhydride was measured to be 84.7 wt%.

[0079] Example 3

[0080] (1) Weigh vanadium oxysulfate VOSO4 at 50℃, disperse it in water at a mass ratio of V to water of 1:10, and stir to dissolve for 2 hours.

[0081] (2) At 70°C, sodium hydroxide was added to the solution obtained in step (1) to adjust the pH value to 5.5, and the reaction was allowed to stand for 2 hours to obtain a precipitate.

[0082] (3) At 70°C, add 60wt% phosphoric acid to the suspension obtained in step (2) at a phosphoric acid:V ratio of 1:1, mix for 2 hours to allow the precipitate to redissolve and obtain a sol-state V source.

[0083] Using tetraethylammonium hydroxide as template agent R, aluminum isopropoxide as aluminum source, phosphoric acid as phosphorus source, titanium tetrachloride as titanium source, and a sol-state V source as V source, a feeding ratio of V₂O₅:Al₂O₃:P₂O₅:TiO₂:R:H₂O was 0.2:1:1:0.3:1.2:40 was adopted, and the pH was adjusted to 2 with nitric acid. The catalyst was then crystallized at 180℃ for 10 h, filtered, washed, dried at 120℃ for 3 h, and calcined in a muffle furnace at 750℃ for 6 h to obtain the catalyst. The XRD pattern of the obtained catalyst was similar to that of Example 1. Simultaneously, the pore structure of the catalyst was analyzed, and the specific surface area of ​​the catalyst was measured to be 292 m². 2 / g.

[0084] The resulting catalyst contains, by weight percentage of oxides, 12 wt% TiO2, 8 wt% V2O5, 40 wt% Al2O3, and 40 wt% P2O5.

[0085] Next, using mesitylene and air as raw materials, a fixed-bed reactor was used to prepare homogenate in the presence of a catalyst at a reaction temperature of 420°C and a gas hourly space velocity of 5000 h⁻¹. -1 Raw material feed concentration 20g / m³ 3 The yield of anhydride was measured to be 84.1 wt%.

[0086] Example 4

[0087] At 50℃, vanadium pentoxide (V₂O₅) was weighed and dispersed in water at a mass ratio of V to water of 1:10. Oxalic acid was added at a molar ratio of auxiliaries to V of 1:0.8. The mixture was stirred and dissolved for 2 hours to obtain a vanadium solution.

[0088] (2) At 70°C, sodium hydroxide was added to the solution obtained in step (1) to adjust the pH value to 5.5, and the reaction was allowed to stand for 2 hours to obtain a precipitate.

[0089] (3) At 70°C, add 50wt% sulfuric acid to the suspension obtained in step (2) at a sulfuric acid:V molar ratio of 1:1 and mix for 2 hours to allow the precipitate to redissolve and obtain a sol-state V source.

[0090] Triethylamine was used as the template agent R, boehmite as the aluminum source, phosphoric acid as the phosphorus source, titanium tetrachloride as the titanium source, and a sol-state V source was prepared as the V source. The catalyst was fed in a ratio of V₂O₅:Al₂O₃:P₂O₅:TiO₂:R:H₂O = 0.2:1:1.1:0.3:1.5:45, and the pH was adjusted to 3 with nitric acid. The catalyst was then crystallized at 190°C for 24 h, filtered, washed, dried at 100°C for 4 h, and calcined in a muffle furnace at 750°C for 6 h to obtain the catalyst. The XRD pattern of the obtained catalyst was similar to that of Example 1. The pore structure of the catalyst was analyzed, and the specific surface area was measured to be 285 m². 2 / g.

[0091] The resulting catalyst contains, by weight percentage of oxides, 11.5 wt% TiO2, 7.7 wt% V2O5, 38.5 wt% Al2O3, and 42.3 wt% P2O5.

[0092] Next, using mesitylene and air as raw materials, a fixed-bed reactor was used to prepare homohydric anhydride in the presence of a catalyst at a reaction temperature of 420°C and a gas hourly space velocity of 5000 h⁻¹. -1 Raw material feed concentration 20g / m³3 The yield of anhydride was measured to be 83.8 wt%.

[0093] Example 5

[0094] (1) Weigh vanadium oxysulfate VOSO4 at 50℃, disperse it in water at a mass ratio of V to water of 1:10, stir and dissolve for 2 hours to obtain vanadium solution.

[0095] (2) At 70°C, sodium hydroxide was added to the vanadium solution obtained in step (1) to adjust the pH value to 6, and the reaction was allowed to stand for 2 hours to obtain the precipitate.

[0096] (3) At 70°C, add 50wt% sulfuric acid solution to the suspension obtained in step (2) at a sulfuric acid:V molar ratio of 1:1, mix for 2 hours to allow the precipitate to redissolve and obtain a sol-state V source.

[0097] Using triethylamine as a template agent, aluminum isopropoxide as an aluminum source, phosphoric acid as a phosphorus source, titanium tetrachloride as a titanium source, and a sol-state V source as the V source, a feedstock was prepared according to the ratio of V₂O₅:Al₂O₃:P₂O₅:TiO₂:R:H₂O = 0.15:1:1:0.3:1.5:45, and the pH was adjusted to 5.5 with sodium hydroxide. The catalyst was then crystallized at 200℃ for 20 h, filtered, washed, dried at 110℃ for 4 h, and calcined in a muffle furnace at 700℃ for 6 h to obtain the catalyst. The XRD pattern of the obtained catalyst was similar to that of Example 1. Simultaneously, the pore structure of the catalyst was analyzed, and the specific surface area of ​​the catalyst was measured to be 290 m². 2 / g.

[0098] The resulting catalyst contains, by weight percentage of oxides, 12.2 wt% TiO2, 6.1 wt% V2O5, 40.8 wt% Al2O3, and 40.8 wt% P2O5.

[0099] Next, using mesitylene and air as raw materials, a fixed-bed reactor was used to prepare homohydric anhydride in the presence of a catalyst at a reaction temperature of 420°C and a gas hourly space velocity of 5000 h⁻¹. -1 Raw material feed concentration 20g / m³ 3 The yield of anhydride was measured to be 82.1 wt%.

[0100] Example 6

[0101] Triethylamine was used as the template agent R, aluminum isopropoxide as the aluminum source, phosphoric acid as the phosphorus source, and titanium tetrachloride as the titanium source. The materials were fed in a ratio of Al₂O₃:P₂O₅:TiO₂:R:H₂O = 1:1:0.3:1.5:45, and the pH was adjusted to 2 with nitric acid. The mixture was then crystallized at 200℃ for 16 h, filtered, washed, dried at 110℃ for 4 h, and finally calcined in a muffle furnace at 700℃ for 6 h to obtain the catalyst precursor.

[0102] Subsequently, (1) at 50°C, vanadium oxysulfate VOSO4 was weighed and dispersed in water at a mass ratio of V to water of 1:10. The solution was stirred and dissolved for 2 hours to obtain a vanadium solution.

[0103] (2) At 70°C, sodium hydroxide was added to the vanadium solution obtained in step (1) to adjust the pH value to 6, and the reaction was allowed to stand for 2 hours to obtain a precipitate.

[0104] (3) At 70°C, add 50wt% sulfuric acid solution to the suspension obtained in step (2) at a sulfuric acid:V molar ratio of 1:1, mix for 2 hours to allow the precipitate to redissolve and obtain a sol-state V source.

[0105] (4) The above-mentioned sol-state V source was loaded onto the catalyst precursor by impregnation at a ratio of V2O5:Al2O3 = 0.15:1. The loaded catalyst was aged at room temperature for 12 h, dried in an oven at 100 °C for 12 h, and then calcined in a muffle furnace at 500 °C for 5 h to obtain the final catalyst. Compared with Example 1, the XRD pattern of the obtained catalyst showed new characteristic diffraction peaks at 20.3 and 31.0 °C, which are peaks of V2O5. At the same time, the pore structure of the catalyst was analyzed, and the specific surface area of ​​the catalyst was measured to be 309 m². 2 / g.

[0106] The catalyst contains, by weight percentage of oxides, 12.2 wt% TiO2, 6.1 wt% V2O5, 40.8 wt% Al2O3, and 40.8 wt% P2O5.

[0107] Next, using mesitylene and air as raw materials, a fixed-bed reactor was used to prepare homohydric anhydride in the presence of a catalyst at a reaction temperature of 420°C and a gas hourly space velocity of 5000 h⁻¹. -1 Raw material feed concentration 20g / m³ 3 The average anhydride yield was measured to be 81.2%.

[0108] Example 7

[0109] (1) Weigh vanadium oxysulfate VOSO4 at 50℃, disperse it in water at a mass ratio of V to water of 1:10, stir and dissolve for 2 hours to obtain vanadium solution.

[0110] (2) At 70°C, sodium hydroxide was added to the vanadium solution obtained in step (1) to adjust the pH value to 6, and the reaction was allowed to stand for 2 hours to obtain a precipitate.

[0111] (3) At 70°C, add 50wt% sulfuric acid solution to the suspension obtained in step (2) at a sulfuric acid:V molar ratio of 1:1, mix for 2 hours to allow the precipitate to redissolve and obtain a sol-state V source.

[0112] Using triethylamine as template agent R, aluminum isopropoxide as aluminum source, phosphoric acid as phosphorus source, titanium tetrachloride as titanium source, and a sol-state V source as V source, a catalyst was prepared. The catalyst was fed in a ratio of V₂O₅:Al₂O₃:P₂O₅:TiO₂:R:H₂O = 0.4:1:1:0.4:1.5:45, and the pH was adjusted to 2 with nitric acid. The catalyst was then crystallized at 200℃ for 16 h, filtered, washed, dried at 110℃ for 4 h, and calcined in a muffle furnace at 700℃ for 6 h to obtain the catalyst.

[0113] The XRD pattern of the obtained catalyst was similar to that of Example 1. Simultaneously, the pore structure of the catalyst was analyzed, and the specific surface area was measured to be 281 m². 2 / g.

[0114] The resulting catalyst contains, by weight percentage of oxides, 14.3 wt% TiO2, 14.3 wt% V2O5, 35.7 wt% Al2O3, and 35.7 wt% P2O5.

[0115] Next, using mesitylene and air as raw materials, a fixed-bed reactor was used to prepare homogenate in the presence of a catalyst at a reaction temperature of 420°C and a gas hourly space velocity of 5000 h⁻¹. -1 Raw material feed concentration 20g / m³ 3 The yield of anhydride was measured to be 80.2%.

[0116] Example 8

[0117] (1) Weigh vanadium oxysulfate VOSO4 at 50℃, disperse it in water at a mass ratio of V to water of 1:10, stir and dissolve for 2 hours to obtain vanadium solution.

[0118] (2) At 70°C, sodium hydroxide was added to the vanadium solution obtained in step (1) to adjust the pH value to 6, and the reaction was allowed to stand for 2 hours to obtain a precipitate.

[0119] (3) At 70°C, add 50wt% sulfuric acid solution to the suspension obtained in step (2) at a sulfuric acid:V molar ratio of 1:1, mix for 2 hours to allow the precipitate to redissolve and obtain a sol-state V source.

[0120] Using triethylamine as template agent R, aluminum isopropoxide as aluminum source, phosphoric acid as phosphorus source, titanium tetrachloride as titanium source, and a sol-state V source as V source, a catalyst was prepared. The catalyst was fed in a ratio of V₂O₅:Al₂O₃:P₂O₅:TiO₂:R:H₂O = 0.2:1:1:0.8:1.5:45, and the pH was adjusted to 2 with nitric acid. The catalyst was then crystallized at 200℃ for 16 h, filtered, washed, dried at 110℃ for 4 h, and calcined in a muffle furnace at 700℃ for 6 h to obtain the catalyst.

[0121] The XRD pattern of the obtained catalyst was similar to that of Example 1. Simultaneously, the pore structure of the catalyst was analyzed, and the specific surface area was measured to be 285 m². 2 / g.

[0122] The resulting catalyst contains, by weight percentage of oxides, 26.7 wt% TiO2, 6.7 wt% V2O5, 33.3 wt% Al2O3, and 33.3 wt% P2O5.

[0123] Next, using mesitylene and air as raw materials, a fixed-bed reactor was used to prepare homohydric anhydride in the presence of a catalyst at a reaction temperature of 420°C and a gas hourly space velocity of 5000 h⁻¹. -1 Raw material feed concentration 20g / m³ 3 The average anhydride yield was measured to be 79.8%.

[0124] Example 9

[0125] (1) Weigh vanadium oxysulfate VOSO4 at 50℃, disperse it in water at a mass ratio of V to water of 1:10, stir and dissolve for 2 hours to obtain vanadium solution.

[0126] (2) At 70°C, sodium hydroxide was added to the vanadium solution obtained in step (1) to adjust the pH value to 6, and the reaction was allowed to stand for 2 hours to obtain a precipitate.

[0127] (3) At 70°C, add 50wt% sulfuric acid solution to the suspension obtained in step (2) at a sulfuric acid:V molar ratio of 1:1, mix for 2 hours to allow the precipitate to redissolve and obtain a sol-state V source.

[0128] Using triethylamine as template agent R, aluminum isopropoxide as aluminum source, phosphoric acid as phosphorus source, tetraisopropyl titanate as titanium source, and a sol-state V source as V source, a catalyst was prepared. The catalyst was fed in a ratio of V₂O₅:Al₂O₃:P₂O₅:TiO₂:R:H₂O = 0.15:1:1:0.3:1.5:45, and the pH was adjusted to 2 with nitric acid. The catalyst was then crystallized at 200℃ for 16 h, filtered, washed, dried at 110℃ for 4 h, and calcined in a muffle furnace at 700℃ for 6 h to obtain the catalyst.

[0129] The XRD pattern of the obtained catalyst was similar to that of Example 1. Simultaneously, the pore structure of the catalyst was analyzed, and the specific surface area was measured to be 290 m². 2 / g.

[0130] The resulting catalyst contains, by weight percentage of oxides, 12.2 wt% TiO2, 6.1 wt% V2O5, 40.8 wt% Al2O3, and 40.8 wt% P2O5.

[0131] Next, using mesitylene and air as raw materials, a fixed-bed reactor was used to prepare homogenate in the presence of a catalyst at a reaction temperature of 420°C and a gas hourly space velocity of 5000 h⁻¹. -1 Raw material feed concentration 20g / m³ 3 The yield of anhydride was measured to be 80.5%.

[0132] Example 10

[0133] (1) Weigh vanadium oxysulfate VOSO4 at 50℃, disperse it in water at a mass ratio of V to water of 1:10, stir and dissolve for 2 hours to obtain vanadium solution.

[0134] (2) At 70°C, sodium hydroxide was added to the vanadium solution obtained in step (1) to adjust the pH value to 6, and the reaction was allowed to stand for 2 hours to obtain a precipitate.

[0135] (3) At 70°C, add 50wt% sulfuric acid solution to the suspension obtained in step (2) at a sulfuric acid:V molar ratio of 1:1, mix for 2 hours to allow the precipitate to redissolve and obtain a sol-state V source.

[0136] A mixture of triethylamine and pentaerythritol (triethylamine:pentaerythritol molar ratio = 1:1) was used as template agent R, aluminum isopropoxide as aluminum source, phosphoric acid as phosphorus source, titanium tetrachloride as titanium source, and a sol-state V source was prepared as V source. The materials were fed in a ratio of V₂O₅:Al₂O₃:P₂O₅:TiO₂:R:H₂O = 0.15:1:1:0.3:1.5:45, and the pH was adjusted to 2 with nitric acid. The mixture was then crystallized at 200℃ for 16 h, filtered, washed, dried at 110℃ for 4 h, and calcined in a muffle furnace at 700℃ for 6 h to obtain the catalyst.

[0137] The XRD pattern of the obtained catalyst was similar to that of Example 1. Simultaneously, the pore structure of the catalyst was analyzed, and the specific surface area was measured to be 286 m². 2 / g.

[0138] The resulting catalyst contains, by weight percentage of oxides, 12.2 wt% TiO2, 6.1 wt% V2O5, 40.8 wt% Al2O3, and 40.8 wt% P2O5.

[0139] Next, using mesitylene and air as raw materials, a fixed-bed reactor was used to prepare homohydric anhydride in the presence of a catalyst at a reaction temperature of 420°C and a gas hourly space velocity of 5000 h⁻¹. -1 Raw material feed concentration 20g / m³ 3 The average anhydride yield was measured to be 86.2%.

[0140] Comparative Example 1

[0141] Triethylamine was used as a template agent, aluminum isopropoxide as the aluminum source, and phosphoric acid as the phosphorus source. The materials were fed in a ratio of Al₂O₃:P₂O₅:R:H₂O = 1:1:1.5:45, and the pH was adjusted to 2 with nitric acid. The mixture was then crystallized at 200°C for 16 hours, filtered, washed, dried at 110°C for 4 hours, and calcined in a muffle furnace at 700°C for 6 hours to obtain the catalyst.

[0142] Next, using mesitylene and air as raw materials, a fixed-bed reactor was used to prepare homohydric anhydride in the presence of a catalyst at a reaction temperature of 420°C and a gas hourly space velocity of 5000 h⁻¹. -1 Raw material feed concentration 20g / m³ 3 The measured conversion rate of mesitylene was <50%, indicating that the catalyst activity was significantly insufficient.

[0143] Comparative Example 2

[0144] (1) Weigh vanadium oxysulfate VOSO4 at 50℃, disperse it in water at a mass ratio of V to water of 1:10, stir and dissolve for 2 hours to obtain vanadium solution.

[0145] (2) At 70°C, sodium hydroxide was added to the vanadium solution obtained in step (1) to adjust the pH value to 6, and the reaction was allowed to stand for 2 hours to obtain a precipitate.

[0146] (3) At 70°C, add 50wt% sulfuric acid solution to the suspension obtained in step (2) at a sulfuric acid:V molar ratio of 1:1, mix for 2 hours to allow the precipitate to redissolve and obtain a sol-state V source.

[0147] Using triethylamine as template agent R, aluminum isopropoxide as aluminum source, phosphoric acid as phosphorus source, and a sol-state V source as V source, the catalyst was prepared. The catalyst was fed in a ratio of V₂O₅:Al₂O₃:P₂O₅:R:H₂O = 0.15:1:1:1.5:45, and the pH was adjusted to 2 with nitric acid. The catalyst was then crystallized at 200℃ for 16 h, filtered, washed, dried at 110℃ for 4 h, and calcined in a muffle furnace at 700℃ for 6 h.

[0148] Next, using mesitylene and air as raw materials, a fixed-bed reactor was used to prepare homohydric anhydride in the presence of a catalyst at a reaction temperature of 420°C and a gas hourly space velocity of 5000 h⁻¹. -1Raw material feed concentration 20g / m³ 3 The yield of anhydride was measured to be 74.2 wt%.

[0149] 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. A catalyst for the gas-phase oxidation of mesitylene to synthesize homohydric anhydride, characterized in that, The catalyst contains an AFI-structured molecular sieve, as well as V and Ti elements. The XRD diffraction pattern of the catalyst has major characteristic diffraction peaks at 2θ = 7.4, 12.9, 14.9, 19.8, 21.0, 22.4, 26.0, 27.4, 29.1, 30.1, 34.6, 36.1, 37.8, 39.2, 41.2, 44.1, 54.3, 56.6, 62.7, 64.0, 69.0, and 69.

8.

2. The catalyst according to claim 1, wherein, The catalyst contains 1 wt% to 20 wt% TiO2, 0.1 wt% to 10 wt% V2O5, and 60 wt% to 90 wt% AFI structured molecular sieves, by weight percentage of oxides.

3. The catalyst according to claim 1 or 2, wherein, In the catalyst, the AFI-structured molecular sieve contains Al, P, and O elements. Preferably, the catalyst contains 30 wt% to 60 wt% Al2O3 and 30 wt% to 50 wt% P2O5, based on the weight percentage of the oxides. More preferably, the catalyst contains, by weight percentage of oxides: 0.1 wt% to 10 wt% V2O5, 30 wt% to 60 wt% Al2O3, 30 wt% to 50 wt% P2O5, and 1 wt% to 20 wt% TiO2; More preferably, the catalyst contains, by weight percentage of oxides: 6.0 wt% to 8.5 wt% V2O5, 35 wt% to 45 wt% Al2O3, 38 wt% to 43 wt% P2O5, and 11.0 wt% to 14.5 wt% TiO2.

4. The catalyst according to any one of claims 1-3, wherein, Ti exists in the form of TiO2; and / or The specific surface area of ​​the catalyst is 200-400 m². 2 / g, preferably 280-310m 2 / g.

5. A method for preparing a catalyst for the gas-phase oxidation of mesitylene to synthesize homohydric anhydride, characterized in that, The method includes forming a hydrothermal crystallization material by combining a vanadium source, a titanium source, and raw materials for synthesizing molecular sieves with AFI structures, followed by hydrothermal crystallization and calcination, wherein the pH of the hydrothermal crystallization material is 1 to 4. Preferably, The vanadium source is selected from one or more of vanadium oxysulfate, vanadium pentoxide, vanadium oxyphosphate, vanadium hydroperoxide, and vanadium oxalate; preferably, the vanadium source is selected from one or more of vanadium oxysulfate and vanadium pentoxide; and / or The titanium source is selected from one or more of titanium tetrachloride, tetraisopropyl titanate, and tetraethyl titanate; preferably, the titanium source is titanium tetrachloride; preferably, the vanadium source is added in the form of a sol-gel vanadium source. More preferably, an additive is added to disperse the vanadium source during the preparation of the sol-state vanadium source, and the molar ratio of the additive to the V element in the vanadium source is 1:0.5 to 1.

6. The preparation method according to claim 5, wherein the AFI-structured molecular sieve contains Al, P, and O elements, and the method comprises: A vanadium source, aluminum source, phosphorus source, titanium source, water, and template agent are used to form a material to be hydrothermally crystallized, followed by hydrothermal crystallization and calcination. in, Preferably, the vanadium source is calculated as V2O5, the aluminum source as Al2O3, the phosphorus source as P2O5, and the titanium source as TiO2, and the weight ratio of vanadium source: aluminum source: phosphorus source: titanium source: template agent: water is (0.01~0.35):1:(0.5~1.3):(0.03~0.7):(1~5):(30~200); More preferably, the vanadium source is V2O5, the aluminum source is Al2O3, the phosphorus source is P2O5, the titanium source is TiO2, and the weight ratio of vanadium source: aluminum source: phosphorus source: titanium source: template agent: water is (0.1~0.25):1:(0.9~1.2):(0.2~0.5):(1~2):(35~50).

7. The preparation method according to claim 6, wherein, The aluminum source is selected from one or more of boehmite, aluminum isopropoxide, aluminum nitrate, and aluminum hydroxide, preferably one or more of boehmite and aluminum isopropoxide; and / or The phosphorus source is selected from one or more of phosphoric acid, ammonium dihydrogen phosphate, pyrophosphate, and phosphorous acid, preferably phosphoric acid; and / or The template agent is selected from one or more of triethylamine, tri-n-propylamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, pentaerythritol, tetramethylammonium bromide, and tetraethylammonium bromide, preferably a mixture of triethylamine and pentaerythritol, and the molar ratio of the two is 0.5-10:

1.

8. The preparation method according to any one of claims 5-7, wherein, The conditions for hydrothermal crystallization include: The temperature for hydrothermal crystallization is 150–200°C, preferably 180–200°C; and / or The hydrothermal crystallization time is 8–48 h, preferably 10–24 h; and / or The calcination temperature is 650-750℃; and / or The roasting time is 2-10 hours.

9. The catalyst obtained by the preparation method according to any one of claims 5-8.

10. The use of the catalyst according to any one of claims 1 to 4, 9 in the synthesis of homotoluene from mesitylene; Preferably, the mass concentration of mesitylene is 15–45 g / m³. 3 The volumetric hourly space velocity is 4000–8000 hr. -1 The reaction temperature is 330–500℃, and the reaction pressure is atmospheric pressure.

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