MFI molecular sieve-metal composite material, preparation method and application thereof, and method for catalyzing oxidation synthesis of pyromellitic dianhydride from durene

Abstract

The invention provides an MFI molecular sieve-metal composite material, the material contains a molecular sieve with an MFI structure and active component elements, the active component elements comprise V and Ti, the Ti element is not on a framework of the molecular sieve with the MFI structure, and the preparation method comprises the following steps: forming a material to be subjected to hydrothermal crystallization from a vanadium source, a titanium source and raw materials for synthesizing the molecular sieve with the MFI structure, and then carrying out hydrothermal crystallization and roasting. The composite material provided by the invention adopts the molecular sieve and the titanium dioxide with specific crystal forms, and exerts excellent catalytic performance, especially oxidation performance, such as the performance of preparing pyromellitic dianhydride through durene gas phase oxidation, so that higher pyromellitic dianhydride yield is obtained.

Description

Technical Field

[0001] This invention relates to the field of materials preparation, specifically to MFI molecular sieve-metal composite materials, their preparation methods and applications, and a method for catalytic oxidation of mesitylene to synthesize homohydric anhydride. Background Technology

[0002] With the rapid development of industries such as petroleum refining, polyester, and chemical fibers, large-scale refineries and aromatic disproportionation and isomerization units generate 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), as an important intermediate for high-value-added fine chemicals, possesses excellent heat resistance, electrical insulation, and chemical resistance. It can be used to produce monomers for heat-resistant resins such as polyimide and polyimide, as a pharmaceutical intermediate, and as an epoxy resin curing agent. Pyromellitic dianhydride and its derivatives have wide applications in organic synthesis and new chemical materials industries, making them high-value-added chemical intermediates. 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 achieved through gas-phase oxidation. However, this process is a complex heterogeneous catalytic process with various side reactions, resulting in very low homohydric anhydride yields. Gas-phase oxidation catalysts for homohydric anhydride preparation primarily employ vanadium-titanium-based spray-coated catalysts, supplemented with small amounts of auxiliary elements to form a slurry. This active component slurry is then sprayed onto an inert support. Previous studies have suggested that TiO2 has a certain impact on homohydric anhydride yield. Researchers have investigated anatase and rutile titanium dioxide-supported vanadium-based catalysts. Chinese patent CN102319580 proposes that catalysts prepared from anatase TiO2 exhibit relatively better performance in the gas-phase oxidation of mesitylene to homohydric anhydride compared to rutile TiO2. Currently, the titanium dioxide phase used in industrial applications is mainly anatase TiO2, and when applied industrially, the mass yield of homohydric anhydride is far lower than the theoretical yield (163%). Summary of the Invention

[0004] In nature, TiO2 is a polycrystalline compound, existing in three crystalline forms: rutile, anatase, and brookite. For a long time, due to the relatively immature preparation methods for pure brookite TiO2, research on its structure and properties has been neglected. In fact, compared to anatase and rutile TiO2, brookite TiO2 possesses many unique characteristics. Meanwhile, MFI-structured molecular sieves exhibit a certain three-dimensional pore structure with anisotropy. Furthermore, the ZSM-5 molecular sieve in MFI molecular sieves possesses strong acidic sites due to the partial substitution of silicon atoms with aluminum atoms in its framework, making it a suitable oxide catalyst carrier and demonstrating good catalytic activity in some oxidation reactions. If a method can be developed to efficiently synthesize a molecular sieve-brookite composite catalyst in a one-step process, and achieve superior performance in the oxidation of mesitylene to homohydric anhydride, it will have significant implications for the development of the homohydric anhydride synthesis industry and even the entire polyimide industry.

[0005] The purpose of this invention is to provide a novel composite material containing a molecular sieve with an MFI structure and active component elements, including V and Ti. The composite material of this invention is particularly suitable for use as a catalyst, especially an oxidation catalyst, and is particularly suitable for the gas-phase oxidation of mesitylene to prepare homohydric anhydride.

[0006] To achieve the above objectives, the present invention provides an MFI molecular sieve-metal composite material containing an MFI molecular sieve and active component elements, wherein the active component elements include V and Ti, and the Ti element is not on the framework of the MFI molecular sieve.

[0007] The composite material has a stable structure and the Ti element, which does not enter the MFI framework, exists in the form of oxides, which makes it more stable during the reaction process.

[0008] In this invention, there are no special requirements for the content of each substance. According to a preferred embodiment of the invention, the material contains 1 wt% to 20 wt% TiO2, 0.1 wt% to 10 wt% V2O5, and 70 wt% to 99 wt% MFI molecular sieves by weight percentage of oxides.

[0009] In this invention, there are no special requirements for the elemental composition of the MFI structure molecular sieve. According to a preferred embodiment of this invention, the MFI structure molecular sieve in the material contains Si, O elements and optionally Al elements.

[0010] Materials having the aforementioned composition and content can achieve the purpose of this invention. According to a preferred embodiment of this invention, the material contains 0 wt% to 4.0 wt% Al2O3 and 70 wt% to 99 wt% SiO2 by weight percentage of oxides.

[0011] According to a preferred embodiment of the present invention, the material contains, by weight percentage of oxides: 0.1wt% to 10wt% V2O5, 0wt% to 4.0wt% Al2O3, 70wt% to 99wt% SiO2, and 1wt% to 20wt% TiO2.

[0012] According to a preferred embodiment of the present invention, the material contains, by weight percentage of oxides: 0.3wt% to 0.5wt% V2O5, 0wt% to 0.5wt% Al2O3, 97.6wt% to 97.9wt% SiO2, and 1.5wt% to 2.0wt% TiO2.

[0013] In this invention, as long as the purpose of this invention can be achieved, there are no special requirements on the form in which Ti element exists. According to a preferred embodiment of this invention, Ti element exists in the form of TiO2.

[0014] According to a preferred embodiment of the present invention, TiO2 exhibits a brookite-like form. TiO2 existing in the form of brookite, together with an MFI-structured molecular sieve, forms a composite catalyst, which has the advantage of high catalytic efficiency.

[0015] In this invention, any material having the aforementioned composition and content can achieve the purpose of this invention. There are no special requirements for the specific surface area of ​​the material. According to a preferred embodiment of this invention, the specific surface area of ​​the material is 300-600 m². 2 / g can provide more active sites, which is beneficial to the reaction.

[0016] According to a preferred embodiment of the present invention, the specific surface area of ​​the material is 540-560 m². 2 / g.

[0017] In this invention, as long as the objective of the invention can be achieved, there are no special requirements for the XRD diffraction pattern of the material. According to a preferred embodiment of the invention, the XRD diffraction pattern of the material is in the range of 2θ = 8.0, 8.8, 8.9, 9.1, 13.2, 13.9, 14.8, 14.9, 15.6, 15.9, 17.6, 17.8, 19.2, 20.4, 20.9, 23.1, 23.3, 23.7, 23.9, 24.4, 25.4. The main diffraction characteristic peaks are located at 25.6, 26.5, 26.9, 29.3, 29.9, 30.1, 30.8, 34.4, 36.2, 40.2, 46.1, 48.0, 49.2, 54.2, 55.2, and 57.2. Among them, the peaks at 2θ = 25.4, 30.8, 36.2, 40.2, 46.1, 48.0, 49.2, 54.2, 55.2, and 57.2 are diffraction peaks of brookite type TiO2.

[0018] In this invention, the range of selectable MFI molecular sieves is relatively wide. One embodiment is illustrated by way of example, but it does not limit the scope of the invention. For example, the MFI molecular sieve is ZSM-5 and / or Silicalite-1.

[0019] The second aspect of the present invention provides a method for preparing MFI molecular sieve-metal composite material, characterized in that the method includes forming a material to be hydrothermally crystallized by combining a vanadium source, a titanium source and raw materials for synthesizing the molecular sieve structure, followed by hydrothermal crystallization and calcination.

[0020] The MFI molecular sieve-metal composite materials obtained by the aforementioned preparation methods can all achieve the objectives of this invention. There are no special requirements for the form of vanadium source addition. According to a preferred embodiment of this invention, the vanadium source is added in the form of a sol-gel vanadium source, which has the advantage of high catalytic efficiency.

[0021] In this invention, as long as a sol-state vanadium source can be obtained, there are no special requirements for its preparation method. An exemplary embodiment is described, but this does not limit the scope of the invention. For example, the preparation method of the sol-state vanadium source includes: (1) mixing the vanadium source with water to obtain a vanadium solution; (2) adding an alkali to the vanadium solution obtained in step (1) to react and generate a suspension; (3) adding an acid to the product of step (2) to obtain a sol-state vanadium source.

[0022] More specifically, for example, the preparation method of sol-state vanadium source includes: (1) weighing vanadium source at 40-80℃, dispersing it in water at a mass ratio of vanadium to water of 1:(1-20), stirring and dissolving for 1-6 hours to obtain vanadium solution.

[0023] (2) At 40-80℃, add alkali to the vanadium solution obtained in step (1) to adjust the pH to 5-8, and the reaction produces a suspension.

[0024] (3) At 40-80℃, acid is added to the suspension obtained in step (2) to precipitate and dissolve to obtain sol-state V source.

[0025] According to a preferred embodiment of the present invention, the molecular sieve with the MFI structure contains Si, O and optionally Al elements, and the preparation method of the MFI molecular sieve-metal composite material includes: mixing a vanadium source, a silicon source, a titanium source, water, a template agent and optionally an aluminum source, hydrothermally crystallizing and calcining.

[0026] In this invention, as long as the purpose of this invention can be achieved, there are no special requirements for the amount of silicon source, vanadium source, aluminum source, titanium source, template agent and water in the raw materials. According to a preferred embodiment of this invention, the vanadium source is calculated as V2O5, the aluminum source is calculated as Al2O3, the silicon source is calculated as SiO2, the Ti source is calculated as TiO2, and the weight ratio of silicon source: vanadium source: aluminum source: titanium source: template agent: water = 1: (0.001~0.14): (0~0.045): (0.011~0.30): (0.1~0.50): (5~200).

[0027] According to a preferred embodiment of the present invention, the vanadium source is calculated as V2O5, the aluminum source as Al2O3, the silicon source as SiO2, and the Ti source as TiO2. The weight ratio of silicon source: vanadium source: aluminum source: titanium source: template agent: water is 1:(0.003~0.005):(0~0.005):(0.015~0.02):(0.1~0.50):(20~100).

[0028] In this invention, the range of vanadium sources is relatively wide, for example, selected from one or more of vanadium oxysulfate, vanadium acetate, vanadium pentoxide, vanadium oxyphosphate, vanadium hydroperoxide, and vanadium oxyoxate.

[0029] According to a preferred embodiment of the present invention, the vanadium source is selected from vanadium oxysulfate and / or vanadium pentoxide. The aforementioned technical solution has the advantages of high anhydride yield and stable catalyst structure.

[0030] In this invention, the range of aluminum sources is relatively wide, for example, selected from one or more of boehmite, aluminum isopropoxide, aluminum nitrate, and aluminum hydroxide.

[0031] According to a preferred embodiment of the present invention, the aluminum source is selected from aluminum isopropoxide and / or boehmite.

[0032] In this invention, the range of silicon sources is relatively wide, for example, one or more selected from silica sol, coarse-porous silica gel, sodium silicate, and water glass.

[0033] According to a preferred embodiment of the present invention, the silicon source is selected from silica sol and / or sodium silicate.

[0034] In this invention, the range of titanium sources is relatively wide, for example, one or more selected from titanium tetrachloride, titanium sulfate, tetraisopropyl titanate and tetraethyl titanate.

[0035] According to a preferred embodiment of the present invention, the titanium source is selected from titanium tetrachloride and / or titanium sulfate.

[0036] In this invention, the template agent has a wide range of options, such as one or more selected from triethylamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, methyldipropylamine, and ethyldibutylamine.

[0037] According to a preferred embodiment of the present invention, the template agent is selected from a mixture of tetrapropylammonium hydroxide and methyldipropylamine, and the molar ratio of the two is 0.2-5:1. According to a preferred embodiment of the present invention, the pH of the material to be hydrothermally crystallized is 9-12, for example, pH 9, 9.5, 10, 10.5, 11, 11.5, 12. Using the aforementioned technical solution, it has the advantages of high anhydride yield and stable catalyst structure.

[0038] In this invention, commonly used alkali sources can be used to adjust the pH of the material to be hydrothermally crystallized. For example, the alkali source is selected from one or more of sodium hydroxide or potassium hydroxide.

[0039] According to a preferred embodiment of the present invention, the conditions for hydrothermal crystallization include: the temperature of hydrothermal crystallization is 150 to 200°C, for example 150°C, 160°C, 170°C, 180°C, 190°C, or 200°C.

[0040] According to a preferred embodiment of the present invention, the conditions for hydrothermal crystallization include: the hydrothermal crystallization time is 8 to 48 hours, for example, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 24 hours, 28 hours, 32 hours, 36 hours, 42 hours, and 48 hours.

[0041] After hydrothermal crystallization, drying is usually carried out using conventional parameters, such as a drying temperature of 85–240°C and a drying time of 4–48 hours.

[0042] According to a preferred embodiment of the present invention, the calcination conditions include: a calcination temperature of 550 to 700°C, for example, 550°C, 580°C, 600°C, 620°C, 650°C, 680°C, or 700°C.

[0043] According to a preferred embodiment of the present invention, the roasting conditions include: a roasting time of 2 to 10 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours.

[0044] A third aspect of the present invention provides a composite material obtained by the preparation method described in the present invention.

[0045] The preparation method of this invention is simple and the raw materials are readily available. The prepared composite material has the advantages of high anhydride yield and stable catalyst structure, and has good application prospects.

[0046] The fourth aspect of the present invention provides the application of the composite material of the present invention as a catalyst, and the composite material of the present invention is particularly suitable for use as an oxidation catalyst.

[0047] The fifth aspect of the present invention provides a method for catalytic oxidation of mesitylene to synthesize homohydric anhydride, the method comprising: catalytically oxidizing mesitylene to synthesize homohydric anhydride in the presence of the composite material of the present invention.

[0048] According to a preferred embodiment of the present invention, the conditions for the catalytic oxidation of mesitylene to synthesize homohydric anhydride include: a mesitylene mass concentration of 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.

[0049] When the catalyst of this invention is used for the gas-phase oxidation of mesitylene to synthesize homohydric anhydride, the homohydric anhydride yield can reach more than 85.5 wt%, achieving good technical results.

[0050] Compared with the prior art, the key to this invention is that the composite material uses molecular sieves with specific crystal forms and titanium dioxide, which exhibits excellent catalytic performance, especially oxidation performance, such as the performance of gas-phase oxidation of mesitylene to homohydric anhydride, and achieves a high homohydric anhydride yield. Attached Figure Description

[0051] Figure 1 This is the XRD pattern of the MFI molecular sieve-titanium dioxide composite material synthesized in Example 1. Detailed Implementation

[0052] 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.

[0053] The present invention will be described in detail below through embodiments.

[0054] 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 .

[0055] 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.

[0056] Example 1

[0057] (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.

[0058] (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.

[0059] (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.

[0060] Using tetrapropylammonium hydroxide as the template agent R, aluminum isopropoxide as the aluminum source, silica sol as the silicon source, titanium sulfate as the titanium source, and a sol-state V source as the V source, a composite catalyst was prepared. The catalyst was fed with materials in a weight ratio of SiO2:V2O5:Al2O3:TiO2:template agent:water = 1:0.005:0.005:0.015:0.2:20, and the pH was adjusted to 11 with NaOH. 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 composite catalyst.

[0061] The XRD pattern of the obtained catalyst is shown in the figure. Figure 1 As shown in the figure, the molecular sieve in the catalyst is an MFI structure molecular sieve, and the MFI molecular sieve is ZSM-5. The catalyst exhibits characteristic diffraction peaks at 2θ = 8.0, 8.8, 8.9, 9.1, 13.2, 13.9, 14.8, 14.9, 15.6, 15.9, 17.6, 17.8, 19.2, 20.4, 20.9, 23.1, 23.3, 23.7, 23.9, 24.4, 25.4, 25.6, 26.5, 26.9, 29.3, 29.9, 30.1, 30.8, 34.4, 36.2, 40.2, 46.1, 48.0, 49.2, 54.2, 55.2, and 57.2. Among them, the peaks at 2θ = 25.4, 30.8, 36.2, 40.2, 46.1, 48.0, 49.2, 54.2, 55.2, and 57.2 are attributed to diffraction peaks of brookite-type TiO2. Simultaneously, the catalyst pore structure was analyzed, and the specific surface area of ​​the catalyst was measured to be 545 m². 2 / g.

[0062] The resulting catalyst contains, by weight percentage of oxides, 1.5 wt% TiO2, 0.5 wt% V2O5, 0.5 wt% Al2O3, and 97.5 wt% SiO2.

[0063] 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 85.5 wt%.

[0064] Example 2

[0065] (1) Weigh V2O5 at 50℃, disperse it in water at a mass ratio of V to water of 1:10, add oxalic acid at a molar ratio of 1:0.8 of the additive to V, stir and dissolve for 2 hours to obtain vanadium solution.

[0066] (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.

[0067] (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.

[0068] Triethylamine was used as the template agent R, boehmite as the aluminum source, sodium silicate as the silicon source, titanium tetrachloride as the titanium source, and a sol-state V source was prepared as the V source. The materials were fed in a weight ratio of SiO2:V2O5:Al2O3:TiO2:template agent:water = 1:0.005:0.003:0.015:0.5:50, and the pH was adjusted to 12 with NaOH. The mixture was then crystallized at 190℃ for 24 h, filtered, washed, dried at 100℃ for 4 h, and calcined in a muffle furnace at 650℃ for 6 h to obtain the composite catalyst. The XRD pattern of the obtained catalyst was similar to that of Example 1, indicating that the molecular sieve in the catalyst was an MFI structure molecular sieve, specifically ZSM-5, and the TiO2 was brookite TiO2. The pore structure of the catalyst was analyzed, and the specific surface area was measured to be 560 m². 2 / g.

[0069] The resulting catalyst contains, by weight percentage of oxides, 1.5 wt% TiO2, 0.5 wt% V2O5, 0.3 wt% Al2O3, and 97.7 wt% SiO2.

[0070] 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 84.9 wt%.

[0071] Example 3

[0072] (1) Weigh 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.

[0073] (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.

[0074] (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.

[0075] Using tetraethylammonium hydroxide as the template agent R, aluminum isopropoxide as the aluminum source, silica sol as the silicon source, titanium tetrachloride as the titanium source, and a sol-state V source as the V source, the catalyst was prepared. The materials were fed in a weight ratio of SiO2:V2O5:Al2O3:TiO2:template:water = 1:0.003:0.002:0.02:0.5:100, and the pH was adjusted to 11 with NaOH. 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 composite catalyst. The XRD pattern of the obtained catalyst was similar to that of Example 1, indicating that the molecular sieve in the catalyst is an MFI structure molecular sieve, specifically ZSM-5, and the TiO2 is brookite TiO2. The pore structure of the catalyst was analyzed, and the specific surface area was measured to be 550 m². 2 / g.

[0076] The resulting catalyst contains, by weight percentage of oxides, 2.0 wt% TiO2, 0.3 wt% V2O5, 0.2 wt% Al2O3, and 97.5 wt% SiO2.

[0077] 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 84.8 wt%.

[0078] Example 4

[0079] (1) Weigh V2O5 at 50℃, disperse it in water at a mass ratio of V to water of 1:10, add oxalic acid at a molar ratio of 1:0.5 of the additive to V, stir and dissolve for 2 hours to obtain vanadium solution.

[0080] (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.

[0081] (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.

[0082] Triethylamine was used as a template agent, aluminum isopropoxide as the aluminum source, sodium silicate as the silicon source, and titanium tetrachloride as the titanium source. The catalyst was fed in a weight ratio of SiO2:V2O5:Al2O3:TiO2:template agent:water = 1:0.004:0.002:0.015:0.5:80, and the pH was adjusted to 12 with NaOH. The catalyst was then crystallized at 180℃ for 12 hours, filtered, washed, dried at 110℃ for 4 hours, and calcined in a muffle furnace at 700℃ for 5 hours to obtain the composite catalyst. The XRD pattern of the obtained catalyst was similar to that of Example 1, indicating that the molecular sieve in the catalyst is an MFI structure molecular sieve, specifically ZSM-5, and the TiO2 is brookite TiO2. The pore structure of the catalyst was analyzed, and the specific surface area was measured to be 540 m². 2 / g.

[0083] The resulting catalyst contains, by weight percentage of oxides, 1.5 wt% TiO2, 0.4 wt% V2O5, 0.2 wt% Al2O3, and 97.9 wt% SiO2.

[0084] 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 84.9 wt%.

[0085] Example 5

[0086] (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.

[0087] (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.

[0088] (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.

[0089] Using tetrapropylammonium hydroxide as template agent R, aluminum isopropoxide as aluminum source, silica sol as silicon source, titanium sulfate as titanium source, and a sol-state V source as V source, the catalyst was prepared. The materials were fed in a weight ratio of SiO2:V2O5:Al2O3:TiO2:template agent:water = 1:0.005:0.005:0.015:0.2:20, and the pH was adjusted to 8 with NaOH. 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 composite catalyst. The XRD pattern of the obtained catalyst was similar to that of Example 1, indicating that the molecular sieve in the catalyst is an MFI structure molecular sieve, specifically ZSM-5, and the TiO2 is brookite TiO2. The pore structure of the catalyst was analyzed, and the specific surface area was measured to be 556 m². 2 / g.

[0090] The resulting catalyst contains, by weight percentage of oxides, 1.5 wt% TiO2, 0.5 wt% V2O5, 0.5 wt% Al2O3, and 97.5 wt% SiO2.

[0091] 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 82.8 wt%.

[0092] Example 6

[0093] (1) Weigh V2O5 at 50℃, disperse it in water at a mass ratio of V to water of 1:10, add oxalic acid at a molar ratio of 1:0.8 of the additive to V, stir and dissolve for 2 hours to obtain vanadium solution.

[0094] (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.

[0095] (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.

[0096] Triethylamine was used as the template agent R, sodium silicate as the silicon source, titanium tetrachloride as the titanium source, and a sol-state V source was prepared as the V source. The materials were fed in a weight ratio of SiO2:V2O5:TiO2:template agent:water = 1:0.005:0.015:0.5:50, and the pH was adjusted to 12 with NaOH. The mixture was then crystallized at 190℃ for 24 h, filtered, washed, dried at 100℃ for 4 h, and calcined in a muffle furnace at 650℃ for 6 h to obtain the composite catalyst. The XRD pattern of the obtained catalyst was similar to that of Example 1, indicating that the molecular sieve in the catalyst is an MFI structure molecular sieve, specifically Silicalite-1, and the TiO2 is brookite TiO2. The pore structure of the catalyst was analyzed, and the specific surface area was measured to be 560 m². 2 / g.

[0097] The resulting catalyst contains, by weight percentage of oxides, 1.5 wt% TiO2, 0.5 wt% V2O5, and 98.0 wt% SiO2.

[0098] 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 81.8 wt%.

[0099] Example 7

[0100] Using tetrapropylammonium hydroxide as a template agent, aluminum isopropoxide as the aluminum source, and silica sol as the silicon source, materials were fed in a weight ratio of SiO2:Al2O3:template agent:water = 1:0.005:0.2:20, and the pH was adjusted to 11 with NaOH. 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 ZSM-5 molecular sieve. Vanadium source was then loaded onto brookite-type TiO2 using an impregnation method at a weight ratio of SiO2:V2O5:TiO2 = 1:0.005:0.015 to obtain vanadium-titanium oxide. This vanadium-titanium oxide was then mechanically mixed with the ZSM-5 molecular sieve to obtain a composite catalyst. Compared to Example 1, the XRD pattern of the obtained catalyst showed new characteristic diffraction peaks at 20.3° and 31.0°, which are peaks of V₂O₅ species. This indicates that the molecular sieve in the catalyst is an MFI structure molecular sieve, specifically ZSM-5, and the TiO₂ is brookite TiO₂, forming a non-monolayer-covered vanadium-oxygen species. Simultaneously, the pore structure of the catalyst was analyzed, and the specific surface area was measured to be 548 m². 2 / g.

[0101] The resulting catalyst contains, by weight percentage of oxides, 1.5 wt% TiO2, 0.5 wt% V2O5, 0.5 wt% Al2O3, and 97.5 wt% SiO2.

[0102] 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 wt%.

[0103] Example 8

[0104] (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.

[0105] (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.

[0106] (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.

[0107] Using tetrapropylammonium hydroxide as template agent R, aluminum isopropoxide as aluminum source, silica sol as silicon source, titanium sulfate as titanium source, and a sol-state V source as V source, the catalyst was prepared. The materials were fed in a weight ratio of SiO2:V2O5:Al2O3:TiO2:template agent:water = 1:0.005:0.05:0.015:0.2:20, and the pH was adjusted to 11 with NaOH. 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 a composite catalyst containing ZSM-5 and TiO2. The XRD pattern of the obtained catalyst was similar to that of Example 1, indicating that the molecular sieve in the catalyst is an MFI structure molecular sieve, specifically ZSM-5, and the TiO2 is brookite TiO2. The pore structure of the catalyst was analyzed, and the specific surface area was measured to be 558 m². 2 / g.

[0108] The resulting catalyst contains, by weight percentage of oxides, 1.4 wt% TiO2, 0.5 wt% V2O5, 4.7 wt% Al2O3, and 93.4 wt% SiO2.

[0109] 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 81.2 wt%.

[0110] Example 9

[0111] (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.

[0112] (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.

[0113] (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.

[0114] Using tetrapropylammonium hydroxide as template agent R, aluminum isopropoxide as aluminum source, silica sol as silicon source, titanium sulfate as titanium source, and a sol-state V source as V source, the catalyst was prepared. The materials were fed in a weight ratio of SiO2:V2O5:Al2O3:TiO2:template agent:water = 1:0.005:0.005:0.015:0.2:20, and the pH was adjusted to 13 with NaOH. 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 a composite catalyst containing ZSM-5 and TiO2. The XRD pattern of the obtained catalyst was similar to that of Example 1, indicating that the molecular sieve in the catalyst is an MFI structure molecular sieve, specifically ZSM-5, and the TiO2 is brookite TiO2. The pore structure of the catalyst was analyzed, and the specific surface area was measured to be 550 m². 2 / g.

[0115] The resulting catalyst contains, by weight percentage of oxides, 1.5 wt% TiO2, 0.5 wt% V2O5, 0.5 wt% Al2O3, and 97.5 wt% SiO2.

[0116] 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%.

[0117] Example 10

[0118] Using tetrapropylammonium hydroxide as template agent R, aluminum isopropoxide as aluminum source, silica sol as silicon source, titanium sulfate as titanium source, and vanadium oxysulfate as vanadium source, the catalyst was prepared by feeding materials in a weight ratio of SiO2:V2O5:Al2O3:TiO2:template:water = 1:0.005:0.005:0.015:0.2:20, and adjusting the pH to 11 with NaOH. 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 composite catalyst. The XRD pattern of the obtained catalyst was similar to that of Example 1, indicating that the molecular sieve in the catalyst was an MFI structure molecular sieve, specifically ZSM-5, and the TiO2 was brookite TiO2. The pore structure of the catalyst was also analyzed, and the specific surface area was measured to be 558 m². 2 / g.

[0119] The resulting catalyst contains, by weight percentage of oxides, 1.5 wt% TiO2, 0.5 wt% V2O5, 0.5 wt% Al2O3, and 97.5 wt% SiO2.

[0120] 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 82.0 wt%.

[0121] Example 11

[0122] (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.

[0123] (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.

[0124] (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.

[0125] A mixture of tetrapropylammonium hydroxide and methyldipropylamine (molar ratio 1:1) was used as template agent R, aluminum isopropoxide as the aluminum source, silica sol as the silicon source, titanium sulfate as the titanium source, and a sol-state V source was prepared as the V source. The materials were fed in a weight ratio of SiO2:V2O5:Al2O3:TiO2:template agent:water = 1:0.005:0.005:0.015:0.2:20, and the pH was adjusted to 11 with NaOH. 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 composite catalyst.

[0126] The XRD pattern of the obtained catalyst was similar to that of Example 1, indicating that the molecular sieve in the catalyst was an MFI structure molecular sieve, specifically ZSM-5, and the TiO2 was brookite TiO2. Simultaneously, the pore structure of the catalyst was analyzed, and the specific surface area was measured to be 563 m². 2 / g.

[0127] The resulting catalyst contains, by weight percentage of oxides, 1.5 wt% TiO2, 0.5 wt% V2O5, 0.5 wt% Al2O3, and 97.5 wt% SiO2.

[0128] 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 86.2 wt%.

[0129] Comparative Example 1

[0130] Tetrapropylammonium hydroxide was used as the template agent R, aluminum isopropoxide as the aluminum source, and silica sol as the silicon source. The materials were fed in a weight ratio of SiO2:Al2O3:template agent:water = 1:0.005:0.2:20, and the pH was adjusted to 11 with NaOH. 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.

[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 measured conversion rate of mesitylene was <50%, indicating that the catalyst activity was significantly insufficient.

[0132] Comparative Example 2

[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] Using tetrapropylammonium hydroxide as the template agent R, aluminum isopropoxide as the aluminum source, silica sol as the silicon source, and a sol-state V source as the V source, the materials were added according to a weight ratio of SiO2:V2O5:Al2O3:template agent:water = 1:0.005:0.005:0.2:20, and the pH was adjusted to 11 with NaOH. 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] 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 75.3 wt%.

[0138] 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 MFI molecular sieve-metal composite material, characterized in that, The material contains a molecular sieve with an MFI structure and active component elements, including V and Ti, wherein the Ti element is not on the framework of the molecular sieve with the MFI structure.

2. The material according to claim 1, wherein, The material contains 1 wt% to 20 wt% TiO2, 0.1 wt% to 10 wt% V2O5, and 70 wt% to 99 wt% MFI structured molecular sieves, based on the weight percentage of oxides. Preferably, the molecular sieve with the MFI structure in the material contains Si, O and optionally Al elements; More preferably, the material contains 0 wt% to 4.0 wt% Al2O3 and 70 wt% to 99 wt% SiO2 by weight percentage of oxides.

3. The material according to claim 1 or 2, wherein, The material contains, by weight percentage of oxides: 0.1wt% to 10wt% V2O5, 0wt% to 4.0wt% Al2O3, 70wt% to 99wt% SiO2, and 1wt% to 20wt% TiO2; Preferably, the material contains, by weight percentage of oxides: 0.3wt% to 0.5wt% V2O5, 0wt% to 0.5wt% Al2O3, 97.6wt% to 97.9wt% SiO2, and 1.5wt% to 2.0wt% TiO2; and / or Ti exists in the form of TiO2, preferably TiO2 is of the brookite type; and / or The specific surface area of ​​the material is 300-600 m². 2 / g, preferably, the specific surface area of ​​the material is 540-560m². 2 / g; and / or The XRD diffraction patterns of the material are observed at 2θ = 8.0, 8.8, 8.9, 9.1, 13.2, 13.9, 14.8, 14.9, 15.6, 15.9, 17.6, 17.8, 19.2, 20.4, 20.9, 23.1, 23.3, 23.7, 23.9, 24.4, 25.4, 25.6, 26.5, 26.9, 29.3, and 29.

9. The main diffraction characteristic peaks are located at 30.1, 30.8, 34.4, 36.2, 40.2, 46.1, 48.0, 49.2, 54.2, 55.2, and 57.2; among them, the peaks at 2θ = 25.4, 30.8, 36.2, 40.2, 46.1, 48.0, 49.2, 54.2, 55.2, and 57.2 are diffraction peaks of brookite type TiO2. and / or MFI molecular screening was performed using ZSM-5 and / or Silicalite-1.

4. A method for preparing an MFI molecular sieve-metal composite material, characterized in that, The method includes forming a material to be hydrothermally crystallized by combining a vanadium source, a titanium source, and raw materials for synthesizing molecular sieves with MFI structures, followed by hydrothermal crystallization and calcination. Preferably, the vanadium source is added in the form of a sol-gel vanadium source; More preferably, the method for preparing the sol-state vanadium source includes: (1) mixing the vanadium source with water to obtain a vanadium solution; (2) Add alkali to the vanadium solution obtained in step (1) to react and generate a suspension; (3) Add acid to the product of step (2) to obtain a sol-state vanadium source.

5. The preparation method according to claim 4, wherein the MFI-structured molecular sieve contains Si, O elements and optionally Al element, the method comprising: The vanadium source, silicon source, titanium source, water, template agent and optionally aluminum source are mixed, hydrothermally crystallized and calcined; in, Preferably, the vanadium source is calculated as V2O5, the aluminum source as Al2O3, the silicon source as SiO2, and the Ti source as TiO2. The weight ratio of silicon source: vanadium source: aluminum source: titanium source: template agent: water is 1:(0.001~0.14):(0~0.045):(0.011~0.30):(0.1~0.50):(5~200). More preferably, the vanadium source is calculated as V2O5, the aluminum source as Al2O3, the silicon source as SiO2, and the Ti source as TiO2, and the weight ratio of silicon source: vanadium source: aluminum source: titanium source: template agent: water is 1:(0.003~0.005):(0~0.005):(0.015~0.02):(0.1~0.50):(20~100).

6. The preparation method according to claim 4 or 5, wherein, The vanadium source is selected from one or more of vanadium oxysulfate, vanadium acetate, vanadium pentoxide, vanadium oxyphosphate, vanadium hydroperoxide, and vanadium oxalate. Preferably, the vanadium source is selected from vanadium oxysulfate and / or vanadium pentoxide; and / or The aluminum source is selected from one or more of boehmite, aluminum isopropoxide, aluminum nitrate, and aluminum hydroxide. Preferably, the aluminum source is selected from aluminum isopropoxide and / or boehmite; and / or The silicon source is selected from one or more of silica sol, coarse-porous silica gel, sodium silicate, and water glass. Preferably, the silicon source is selected from silica sol and / or sodium silicate; and / or The titanium source is selected from one or more of titanium tetrachloride, titanium sulfate, tetraisopropyl titanate, and tetraethyl titanate; preferably, the titanium source is selected from titanium tetrachloride and / or titanium sulfate; and / or The template agent is selected from one or more of triethylamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, methyldipropylamine, and ethyldibutylamine. Preferably, the template agent is selected from a mixture of tetrapropylammonium hydroxide and methyldipropylamine, and the molar ratio of the two is 0.2-5:

1.

7. The preparation method according to any one of claims 4-6, wherein, The pH of the material to be hydrothermally crystallized is 9-12; the alkali source is selected from one or more of sodium hydroxide or potassium hydroxide; and / or The conditions for hydrothermal crystallization include: The temperature for hydrothermal crystallization is 150–200℃; and / or The hydrothermal crystallization time is 8–48 hours; and / or The calcination temperature is 550-700℃; and / or The roasting time is 2-10 hours.

8. The composite material obtained by the method according to any one of claims 4-7.

9. The use of the composite material according to any one of claims 1 to 3 and 8 as a catalyst, preferably as an oxidation catalyst.

10. A method for catalytically oxidizing mesitylene to synthesize homohydric anhydride, characterized in that, The method includes: In the presence of the composite material described in any one of claims 1 to 3 and 8, mesitylene is catalytically oxidized to synthesize homohydric anhydride; 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.

Images