Catalyst for oxidation of durene to produce phthalic anhydride, method for preparing the same and method for synthesizing phthalic anhydride

Abstract

The application discloses a molecular sieve catalyst for synthesizing dianhydride from durene by gas phase oxidation, a preparation method of the molecular sieve catalyst and a method for synthesizing dianhydride, the molecular sieve catalyst comprises V, Al, P, O and Ti elements, and contains 0.1wt%-10wt% V2O5, 30wt%-60wt% Al2O3, 30wt%-50wt% P2O5 and 1wt%-20wt% TiO2 in terms of oxides; the structure of the molecular sieve is AFI structure, wherein the Ti element exists in the form of TiO2, and the TiO2 is in the form of anatase. The molecular sieve catalyst comprises V, Al, P, O and Ti elements. The catalyst is suitable for industrial production of dianhydride prepared from durene by gas phase oxidation, and has the characteristics of simple preparation process, high catalytic activity and high dianhydride yield.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalysis technology, in particular to a catalyst for preparing pyromellitic dianhydride from oxidation of durene, a preparation method of the catalyst and a method for synthesizing pyromellitic dianhydride. BACKGROUND

[0002] With the rapid development of petroleum refining, polyester and chemical fiber industries, a large number of C10 aromatic hydrocarbons are produced as by-products in large refinery devices and aromatic hydrocarbon disproportionation and isomerization devices. At present, how to efficiently utilize C10 aromatic hydrocarbon resources has become an important issue in the petroleum chemical industry. Pyromellitic dianhydride (PMDA, pyromellitic dianhydride) as an important intermediate of high value-added fine chemicals has excellent heat resistance, electrical insulation and chemical resistance. It can be used to produce monomers of heat-resistant resins such as polyimide and polyimidazole, pharmaceutical intermediates, epoxy resin curing agents, etc. The products made of it can be widely used in high-end technical fields such as aviation and electronic industry. Therefore, it is of great significance to extract durene with high content from C10 aromatic hydrocarbons produced in refining and further process it into high value-added pyromellitic dianhydride. SUMMARY

[0003] In view of the problems existing in the prior art, the purpose of the present application is to provide a new type of pyromellitic dianhydride catalyst with a main active component combined firmly, which is suitable for industrial production of pyromellitic dianhydride prepared by gas phase oxidation of durene, and has the characteristics of simple preparation process, high catalytic activity and high pyromellitic dianhydride yield.

[0004] The present application research and analysis considers that the interaction force between the active component and the carrier has an important influence on the preparation of pyromellitic dianhydride by gas phase oxidation of durene, and most of the existing technologies for synthesizing pyromellitic dianhydride from durene as raw material adopt gas phase oxidation method. Since this process is a complex heterogeneous catalytic process, there are many side reactions, resulting in very low yield of pyromellitic dianhydride. The vanadium-titanium-based spray catalyst is mainly used in the preparation of pyromellitic dianhydride catalyst, in which a small amount of auxiliary elements is added to form a slurry, and the active component slurry is sprayed onto the inert carrier by spraying method. The inert carrier is mostly made of α-Al2O3, silicon carbide and porcelain ring. However, the active component sprayed onto the inert carrier has weak interaction with the carrier, and there is a risk of falling off during the reaction process.

[0005] If a new type of pyromellitic dianhydride catalyst with a carrier and vanadium-titanium main active component combined firmly can be developed, it will have important significance for the development of the synthesis of pyromellitic dianhydride industry and even the entire polyimide industry. Most of the existing technologies are mainly composed of Al, P and O in the molecular sieve, and for the preparation of pyromellitic dianhydride by gas phase oxidation of durene, the inventors believe that if V and Ti elements can be further effectively introduced and the composition state of Ti and V elements is controlled, it is expected to synthesize efficient pyromellitic dianhydride catalyst for oxidation of durene.

[0006] According to a first aspect of the present application, the present application provides a molecular sieve catalyst for synthesizing dianhydride from durene by gas phase oxidation, the molecular sieve catalyst comprising V, Al, P, O and Ti elements, containing 0.1wt%-10wt% V2O5, 30wt%-60wt% Al2O3, 30wt%-50wt% P2O5 and 1wt%-20wt% TiO2 in terms of oxides; the structure of the molecular sieve is AFI structure, wherein the Ti element exists in the form of TiO2, and the TiO2 presents an anatase type.

[0007] According to a second aspect of the present application, the present application provides a preparation method of the molecular sieve catalyst, the preparation method comprising: mixing a vanadium source, an aluminum source, a phosphorus source, a titanium source, water and a template agent to obtain a mixed solution, and hydrothermally crystallizing.

[0008] According to a third aspect of the present application, the present application provides a method for synthesizing dianhydride from durene by oxidation; the dianhydride is prepared by reacting durene and an oxygen-containing gas in the presence of the molecular sieve catalyst.

[0009] The present application provides a molecular sieve catalyst for synthesizing dianhydride from durene by gas phase oxidation, which is suitable for industrial production of dianhydride from durene by gas phase oxidation, and has the characteristics of simple preparation process, high catalytic activity and high dianhydride yield.

[0010] Compared with the prior art, the key of the present application is that the catalyst uses a molecular sieve with a specific structure, which exhibits excellent performance in synthesizing dianhydride from durene by gas phase oxidation, and a higher dianhydride yield is obtained. When the catalyst of the present application is used for synthesizing dianhydride from durene by gas phase oxidation, the dianhydride yield can reach more than 85wt%, and good technical effects are achieved. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is the XRD spectrum of the molecular sieve with a specific crystal form synthesized in Example 1. DETAILED DESCRIPTION

[0012] The specific embodiments of the present application are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application.

[0013] The present application provides a molecular sieve catalyst for synthesizing dianhydride from durene by gas phase oxidation, the molecular sieve catalyst comprising V, Al, P, O and Ti elements, containing 0.1wt%-10wt% V2O5, 30wt%-60wt% Al2O3, 30wt%-50wt% P2O5 and 1wt%-20wt% TiO2 in terms of oxides; the structure of the molecular sieve is AFI structure, wherein the Ti element exists in the form of TiO2, and the TiO2 presents an anatase type.

[0014] According to a preferred embodiment of the present application, the vanadium species in the molecular sieve catalyst is not formed into a crystal phase, but is dispersed in the catalyst in a monolayer covering form. In the present application, monolayer dispersion refers to the absence of obvious V2O5 phase crystal characteristic body diffraction peaks in XRD.

[0015] According to a preferred embodiment of the present application, the catalyst contains 5wt% to 9wt% V2O5, 35wt% to 45wt% Al2O3, 35wt% to 45wt% P2O5, and 3wt% to 15wt% TiO2 in terms of oxides.

[0016] According to the present application, the XRD diffraction pattern of the molecular sieve catalyst has main diffraction characteristic peaks at 2θ = 7.4, 12.9, 14.9, 19.8, 21.0, 22.4, 25.3, 26.0, 29.1, 30.1, 34.6, 36.9, 37.7, 38.5, 47.9, 53.8, 55.0, 62.6, 68.6, 70.2, 74.9°, wherein the peaks at 2θ = 25.3, 36.9, 37.7, 38.5, 47.9, 53.8, 55.0, 62.6, 68.6, 70.2 and 74.9° belong to the diffraction peaks of anatase TiO2.

[0017] In the present application, the peaks at 2θ = 25.3, 36.9, 37.7, 38.5, 47.9, 53.8, 55.0, 62.6, 68.6, 70.2 and 74.9° belong to the diffraction peaks of anatase TiO2, and the peaks at 2θ = 7.4, 12.9, 14.9, 19.8, 21.0, 22.4, 26.0, 29.1, 30.1 and 34.6° belong to the molecular sieve with AFI structure.

[0018] According to a preferred embodiment of the present application, the molecular sieve catalyst is prepared by a hydrothermal crystallization method; more preferably, in the hydrothermal crystallization process, the vanadium element of the molecular sieve catalyst comes from a sol-state vanadium source.

[0019] According to a preferred embodiment of the present application, the preparation method of the sol-state vanadium source comprises the following steps:

[0020] (1) mixing a vanadium source with water to obtain a vanadium solution;

[0021] (2) adding a base to the vanadium solution obtained in step (1) to generate a precipitate by reaction;

[0022] (3) adding an acid to the product of step (2) to obtain a sol-state vanadium source.

[0023] According to a preferred embodiment of the present application, an additive is added in the mixing in step (1); the additive includes at least one of oxalic acid, citric acid, tartaric acid, and hydrogen peroxide; preferably, the amount of the additive added is in a molar ratio of 1:0.5-1 to the V element in the vanadium source, and when hydrogen peroxide is used, the concentration of the hydrogen peroxide is 10-30wt%.

[0024] According to a preferred embodiment of the present application, the mass ratio of V to water in step (1) is 1:5-15, the time for mixing and dissolving is 1-2h, and the temperature is 40-60℃.

[0025] According to a preferred embodiment of the present application, the base in step (2) includes at least one of sodium hydroxide, potassium hydroxide, and tetraethylammonium hydroxide, and preferably, the amount of the base added is such that the pH value of the mixture is 4-8, preferably 5.5-6; preferably, the reaction temperature is 10-80℃, preferably 50-70℃, such as 50℃, 60℃, or 70℃; and the reaction time is 1-3h, such as 1h, 2h, or 3h.

[0026] According to a preferred embodiment of the present application, the acid in step (3) includes at least one of sulfuric acid and nitric acid; preferably, the amount of the acid is in a molar ratio of 1:0.5-2.0 to the V element in the vanadium source, such as 1:0.5, 1:1, 1:1.5, or 1:2, and the operating conditions include: 60-80℃, such as 60℃, 70℃, or 80℃; time of 1-3h, such as 1h, 2h, or 3h; and acid concentration of 50-70wt%.

[0027] In the present application, in the preparation of the sol-state vanadium source, the vanadium source includes at least one of vanadyl sulfate, vanadium pentoxide, ammonium metavanadate, phosphovanadyl, phosphovanadyl hydrogen, and oxalate vanadyl, and preferably one or more of vanadyl sulfate, vanadium pentoxide, and ammonium metavanadate, and more preferably ammonium metavanadate. This can further improve the activity of the catalyst.

[0028] The present application does not have special requirements for the preparation method of the molecular sieve catalyst, and the catalysts with the features of the present application can be used in the present application, and preferably, the molecular sieve catalyst is prepared by a hydrothermal crystallization method. More preferably, the vanadium element of the molecular sieve catalyst comes from a sol-state vanadium source; for the present application, a preparation method of the molecular sieve catalyst is provided, which includes: mixing a vanadium source, an aluminum source, a phosphorus source, a titanium source, water, and a template agent to obtain a mixed solution, and hydrothermal crystallization to obtain the molecular sieve.

[0029] In the present application, various raw materials can be adapted to the present application, and the following exemplary descriptions are provided, but the scope of the present application is not limited thereto.

[0030] For example, the aluminum source includes one or more of pseudo-boehmite, aluminum isopropoxide, aluminum nitrate, and aluminum hydroxide.

[0031] For example, the phosphorus source comprises at least one of phosphoric acid, ammonium dihydrogen phosphate, pyrophosphoric acid, and phosphorous acid.

[0032] For example, the titanium source is at least one of titanium sulfate, tetrabutyl titanate, and isobutyl titanate, preferably titanium sulfate.

[0033] For example, the template agent comprises at least one of triethylamine, tri-n-propylamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, and hexamethyleneimine, preferably the template agent is a mixture of triethylamine and hexamethyleneimine, and the molar ratio of the two is 0.1-10:1. The above molar ratio can further improve the activity of the catalyst. In the embodiments of the present application, 1:1 is exemplarily described as the advantage, but it is not limited to the scope of the present application.

[0034] For example, the vanadium source: aluminum source: phosphorus source: titanium source: template agent: water = 0.01-0.35:1:0.5-1.3:0.03-0.7:1-5:30-200 by weight, wherein the vanadium source is calculated as V2O5, the aluminum source is calculated as Al2O3, the P source is calculated as P2O5, and the Ti source is calculated as TiO2.

[0035] In the present application, the pH of the mixed solution is preferably controlled to be 4.2-6.6, preferably 5.0-6.0. Preferably, the pH is adjusted with ammonia water. The mass concentration of the ammonia water is 10wt%-25wt%.

[0036] According to the present application, in the preparation method, the hydrothermal crystallization device is preferably an autoclave, and the pressure is autogenous pressure. The pressure can be 1.0-2.5 MPa.

[0037] According to the present application, the hydrothermal crystallization temperature is 150-200°C, preferably 170-190°C, for example 170°C, 180°C, or 190°C; and the hydrothermal crystallization time is 8-48h, preferably 10-24h, for example 10h, 12h, 14h, 16h, 18h, 20h, 22h, or 24h.

[0038] According to the present application, in the preparation method, after hydrothermal crystallization, steps such as washing, filtering, and drying can be performed. The drying can be performed at a conventional parameter, preferably at 80-120°C for 2-12h.

[0039] According to a preferred embodiment of the present application, the vanadium source is added in the form of a sol-state vanadium source; preferably, the preparation method of the sol-state vanadium source comprises the following steps:

[0040] (1) mixing the vanadium source with water to obtain a vanadium solution;

[0041] (2) adding a base to the vanadium solution obtained in step (1) to generate a precipitate by reaction;

[0042] (3) adding acid to the product of step (2) to obtain a sol-state vanadium source.

[0043] According to a preferred embodiment of the present application, an additive is added in the mixing in step (1); the additive includes at least one of oxalic acid, citric acid, tartaric acid, and hydrogen peroxide; preferably, the additive is added in a molar ratio of 1:0.5-1 to the V element in the vanadium source, and when hydrogen peroxide is used, the concentration of the hydrogen peroxide is 10-30wt%.

[0044] According to a preferred embodiment of the present application, the mass ratio of V to water in step (1) is 1:5-15, the time for mixing and dissolving is 1-2h, and the temperature is 40-60℃.

[0045] According to a preferred embodiment of the present application, the base in step (2) includes at least one of sodium hydroxide, potassium hydroxide, and tetraethylammonium hydroxide, and preferably, the base is added in an amount such that the pH value of the mixture is 4-8, preferably 5.5-6; preferably, the reaction temperature is 10-80℃, preferably 50-70℃, for example 50℃, 60℃, or 70℃; and the reaction time is 1-3h, for example 1h, 2h, or 3h.

[0046] According to a preferred embodiment of the present application, the acid in step (3) includes at least one of sulfuric acid and nitric acid; preferably, the acid is added in a molar ratio of 1:0.5-2.0 to the V element in the vanadium source, for example 1:0.5, 1:1, 1:1.5, or 1:2; the operation conditions include 60-80℃, for example 60℃, 70℃, or 80℃; and the time is 1-3h, for example 1h, 2h, or 3h; and the concentration of the acid solution is 50-70wt%.

[0047] In the present application, in the process of preparing the sol-state vanadium source, the vanadium source includes at least one of vanadyl sulfate, divanadium pentoxide, ammonium metavanadate, phosphovanadyl, phosphovanadyl hydrogen, and oxalate vanadyl, and preferably one or more of vanadyl sulfate, divanadium pentoxide, and ammonium metavanadate, and more preferably ammonium metavanadate. Thus the activity of the catalyst can be further improved.

[0048] The present application provides a method for synthesizing dianhydride by oxidizing durene; durene and oxygen-containing gas are used as raw materials to prepare dianhydride in the presence of the molecular sieve catalyst.

[0049] According to the method of the present application, the preferred reaction conditions include: using a fixed bed reactor, the mass concentration of durene is 15-45g / m 3 , for example 15g / m 3 , 20g / m 3 , 25g / m 3 , 30g / m 3 , 35g / m 3, 40 g / m 3 , 45 g / m 3 ) refers to the mass of each m 3 gas raw material, the mass of durene is 15-45 g; the volume space velocity is 4000-8000 hr -1 (eg, 4000 hr -1 , 5000 hr -1 , 6000 hr -1 , 7000 hr -1 , 8000 hr -1 ), the reaction temperature is 330-500℃ (eg, 330℃, 350℃, 370℃, 390℃, 410℃, 430℃, 450℃, 470℃, 490℃, 500℃), the reaction pressure is normal pressure, and the oxygen-containing gas is air.

[0050] In the embodiment of the present application, the reaction temperature is 420℃, the gas hourly space velocity is 5000h -1 , and the raw material feed concentration is 20 g / m 3 as an exemplary illustration of the advantages of the present application.

[0051] Example 1

[0052] (1) At 50℃, vanadyl sulfate VOSO4 was weighed and dispersed in water according to the mass ratio of V to water 1:10, stirred and dissolved for 2h to obtain a vanadium solution.

[0053] (2) At 70℃, 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 2h to obtain a precipitate.

[0054] (3) At 70℃, 50wt% sulfuric acid aqueous solution was added to the suspension obtained in step (2) according to the molar ratio of sulfuric acid to V 1:1, and mixed for 2h to make the precipitate redissolve to obtain a sol state V source.

[0055] The sol state V source was prepared as the V source with triethylamine as the template agent R, aluminum isopropoxide as the aluminum source, phosphoric acid as the phosphorus source, and titanium sulfate as the titanium source. The raw materials were fed according to the weight ratio of V2O5:Al2O3:P2O5:TiO2:R:H2O=0.15:1:1:0.3:1.5:45, and the pH value was adjusted to 5.5 with 10wt% ammonia water.

[0056] Then, crystallization was carried out at 190℃ for 16h, and after suction filtration, washing, and drying at 110℃ for 4h, the AIPO5 molecular sieve containing vanadium and titanium was obtained.

[0057] The XRD spectrum of the obtained molecular sieve is shown in Figure 1It can be seen from the figure that the molecular sieve is an AFI structure molecular sieve. The XRD diffraction pattern of the molecular sieve has main diffraction characteristic peaks at 2θ = 7.4, 12.9, 14.9, 19.8, 21.0, 22.4, 25.3, 26.0, 29.1, 30.1, 34.6, 36.9, 37.7, 38.5, 47.9, 53.8, 55.0, 62.6, 68.6, 70.2, 74.9°, wherein the peaks at 2θ = 25.3, 36.9, 37.7, 38.5, 47.9, 53.8, 55.0, 62.6, 68.6, 70.2 and 74.9° belong to diffraction peaks of anatase TiO2, and there is no obvious crystal characteristic body diffraction peak of V2O5 phase in the XRD pattern, thus it is indicated that the vanadium species does not form a crystal phase, but is dispersed in the catalyst in the form of a monomolecular layer.

[0058] Preparation of pyromellitic dianhydride:

[0059] Then, using durene and air as raw materials, pyromellitic dianhydride was prepared in the presence of the catalyst by using a fixed bed reactor; under the conditions of a reaction temperature of 420℃, a gas hourly space velocity of 5000h-1, and a raw material feeding concentration of 20g / m3 (referring to durene, 20g of durene was fed under air), the pyromellitic dianhydride yield was measured to be 85.3wt%. -1 3 3

[0060] Example 2

[0061] (1) At 50℃, V2O5 was weighed and dispersed in water according to a mass ratio of V to water of 1:10, 20wt% hydrogen peroxide was added according to a molar ratio of the auxiliary to V of 1:0.8, and stirring and dissolution were carried out for 2h to obtain a vanadium solution.

[0062] (2) At 70℃, sodium hydroxide was added to the solution obtained in step (1) to adjust the pH value to 5.5, and standing and reaction were carried out for 2h to obtain a precipitate.

[0063] (3) At 70℃, 50wt% sulfuric acid was added to the suspension obtained in step (2) according to a molar ratio of sulfuric acid to V of 1:1, and mixing was carried out for 2h to make the precipitate redissolve to obtain a sol state V source.

[0064] ​​​The sol-gel V source prepared by using phosphoric acid as the phosphorus source, titanium sulfate as the titanium source, and triethylamine as the template R was used as the V source. The raw materials were added according to the weight ratio of V2O5:Al2O3:P2O5:TiO2:R:H2O = 0.2:1:1.1:0.3:1.5:45, and the pH was adjusted to 5.5 by using sodium hydroxide. Then, the mixture was crystallized at 190°C for 24h, and the AIPO5 molecular sieve containing vanadium and titanium was obtained by filtration, washing, and drying at 100°C for 3h. The molecular sieve was an AFI structure molecular sieve, and the XRD pattern was similar to that of Example 1, indicating that the TiO2 was anatase TiO2, and the vanadium species did not form a crystal phase, but was dispersed in the catalyst in the form of a monolayer.

[0065] The preparation of the phthalic anhydride was the same as in Example 1. The yield of the phthalic anhydride was 84.5wt%.

[0066] Example 3

[0067] (1) At 50°C, VOSO4 was weighed and dispersed in water according to the mass ratio of V to water of 1:10, and stirred and dissolved for 2h.

[0068] (2) At 70°C, sodium hydroxide was added to the solution obtained in step (1) to adjust the pH to 5.5, and the mixture was allowed to stand for 2h to obtain a precipitate.

[0069] (3) At 70°C, 60wt% phosphoric acid was added to the suspension obtained in step (2) according to the ratio of phosphoric acid to V of 1:1, and the mixture was stirred for 2h to dissolve the precipitate again, and a sol-gel V source was obtained.

[0070] The sol-gel V source prepared by using tetraethylammonium hydroxide as the template R, aluminum isopropoxide as the aluminum source, phosphoric acid as the phosphorus source, and titanium sulfate as the titanium source was used as the V source. The raw materials were added according to the weight ratio of V2O5:Al2O3:P2O5:TiO2:R:H2O = 0.2:1:1:0.1:1.2:40, and the pH was adjusted to 5.5 by using sodium hydroxide.

[0071] Then, the mixture was crystallized at 180°C for 10h, and the AIPO5 molecular sieve containing vanadium and titanium was obtained by filtration, washing, and drying at 120°C for 3h. The molecular sieve was an AFI structure molecular sieve, and the XRD pattern was similar to that of Example 1, indicating that the TiO2 was anatase TiO2, and the vanadium species did not form a crystal phase, but was dispersed in the catalyst in the form of a monolayer.

[0072] The preparation of the phthalic anhydride was the same as in Example 1. The yield of the phthalic anhydride was 84.2wt%.

[0073] Example 4

[0074] (1) At 50°C, VOSO4 was weighed and dispersed in water according to the mass ratio of V to water of 1:10, 20wt% hydrogen peroxide was added according to the molar ratio of the additive to V of 1:0.5, and stirred and dissolved for 2h.

[0075] (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 2h to obtain a precipitate.

[0076] (3) At 70°C, 60wt% phosphoric acid was added to the suspension obtained in step (2) according to the ratio of phosphoric acid to V of 1:1, and mixed for 2h to make the precipitate redissolve to obtain a sol state V source.

[0077] Triethylamine was used as a template agent, aluminum isopropoxide was used as an aluminum source, phosphoric acid was used as a phosphorus source, and titanium sulfate was used as a titanium source. The materials were added according to the weight ratio of V2O5:Al2O3:P2O5:TiO2:R:H2O = 0.15:1:1.05:0.3:1.5:45, and 10wt% ammonia water was used to adjust the pH value to 5.5. Then, the crystallization was carried out at 180°C for 12h, and after filtration, washing, and drying at 110°C for 4h, the AIPO5 molecular sieve containing vanadium and titanium was obtained. The molecular sieve was an AFI structure molecular sieve, and the XRD pattern was similar to that of Example 1, indicating that the TiO2 was anatase TiO2, and the vanadium species did not form a crystal phase, but dispersed in the catalyst in the form of a monolayer.

[0078] Preparation of homogeneous anhydride: The homogeneous anhydride yield was measured to be 84.3wt%.

[0079] Example 5

[0080] (1) At 50°C, VOSO4 was weighed and dispersed in water according to the mass ratio of V to water of 1:10, and citric acid was added to dissolve according to the molar ratio of the additive to V of 1:1.0, and stirred and dissolved for 2h.

[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 2h to obtain a precipitate.

[0082] (3) At 70°C, 60wt% phosphoric acid was added to the suspension obtained in step (2) according to the ratio of phosphoric acid to V of 1:1, and mixed for 2h to make the precipitate redissolve to obtain a sol state V source.

[0083] The sol-gel V source was prepared by using tetraethylammonium hydroxide as a template, aluminum isopropoxide as an aluminum source, phosphoric acid as a phosphorus source, and titanium sulfate as a titanium source. The V2O5:Al2O3:P2O5:TiO2:R:H2O was 0.15:1:1:0.2:1.5:40 by weight, and the pH was adjusted to 5.5 by using sodium hydroxide. Then, the crystallization was performed at 170°C for 20h, and the AIPO5 molecular sieve containing vanadium and titanium was obtained by filtration, washing, and drying at 90°C for 5h. The molecular sieve was an AFI structure molecular sieve, and the XRD pattern was similar to that of Example 1. It was indicated that the TiO2 was anatase TiO2, and the vanadium species was not formed into a crystal phase, but dispersed in the catalyst in a monolayer covering form.

[0084] The homomaleic anhydride was prepared according to Example 1, and the homomaleic anhydride yield was 84.1wt%.

[0085] Example 6

[0086] The sol-gel V source was prepared by using tetraethylammonium hydroxide as a template, aluminum isopropoxide as an aluminum source, phosphoric acid as a phosphorus source, and titanium sulfate as a titanium source. The V2O5:Al2O3:P2O5:TiO2:R:H2O was 0.15:1:1:0.2:1.5:40 by weight, and the pH was adjusted to 5.5 by using sodium hydroxide. Then, the crystallization was performed at 170°C for 20h, and the AIPO5 molecular sieve containing vanadium and titanium was obtained by filtration, washing, and drying at 90°C for 5h. The molecular sieve was an AFI structure molecular sieve, and the XRD pattern was similar to that of Example 1. It was indicated that the TiO2 was anatase TiO2, and the vanadium species was not formed into a crystal phase, but dispersed in the catalyst in a monolayer covering form.

[0087] The homomaleic anhydride was prepared according to Example 1, and the homomaleic anhydride yield was 81.7wt%.

[0088] Example 7

[0089] (1) At 50°C, V2O5 was weighed and dispersed in water according to the mass ratio of V to water of 1:10, 20wt% hydrogen peroxide was added according to the molar ratio of the additive to V of 1:0.8, and stirring and dissolution were performed for 2h to obtain a vanadium solution.

[0090] (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 precipitation was obtained by standing for 2h.

[0091] (3) At 70°C, 50wt% sulfuric acid was added to the suspension obtained in step (2) according to the molar ratio of sulfuric acid to V of 1:1, and the precipitation was redissolved by mixing for 2h to obtain a sol-gel V source.

[0092] A mixture of triethylamine and hexamethyleneimine (molar ratio 1:1) was used as template agent R, pseudoboehmite as aluminum source, phosphoric acid as phosphorus source, titanium sulfate as titanium source, and sol-state V source prepared as V source. The raw materials were added according to the weight ratio of V2O5:Al2O3:P2O5:TiO2:R:H2O = 0.2:1:1.1:0.3:1.5:45, and the pH was adjusted to 5.5 with sodium hydroxide. Then the mixture was crystallized at 190°C for 24h, and the AIPO5 molecular sieve containing vanadium and titanium was obtained after filtration, washing, and drying at 100°C for 3h. The molecular sieve was an AFI structure molecular sieve, and the XRD pattern was similar to that of Example 1, indicating that the TiO2 was anatase TiO2, and the vanadium species did not form a crystal phase, but was dispersed in the catalyst in the form of a monolayer.

[0093] The preparation of the homomaleic anhydride was the same as in Example 1. The yield of the homomaleic anhydride was 86.1wt%.

[0094] Example 8

[0095] (1) At 50°C, ammonium metavanadate was weighed and dispersed in water according to a mass ratio of V to water of 1:10, and oxalic acid was added according to a molar ratio of additive to V of 1:0.5, and stirred and dissolved for 2h.

[0096] (2) At 70°C, sodium hydroxide was added to the solution obtained in step (1) to adjust the pH to 5.5, and the mixture was allowed to stand for 2h to obtain a precipitate.

[0097] (3) At 70°C, 60wt% phosphoric acid was added to the suspension obtained in step (2) according to a ratio of phosphoric acid to V of 1:1, and the mixture was stirred for 2h to cause the precipitate to redissolve, and a sol-state V source was obtained.

[0098] Triethylamine was used as a template agent, aluminum isopropoxide as an aluminum source, phosphoric acid as a phosphorus source, and titanium sulfate as a titanium source. The raw materials were added according to the weight ratio of V2O5:Al2O3:P2O5:TiO2:R:H2O = 0.15:1:1.05:0.3:1.5:45, and the pH was adjusted to 5.5 with 10wt% ammonia water. Then the mixture was crystallized at 180°C for 12h, and the AIPO5 molecular sieve containing vanadium and titanium was obtained after filtration, washing, and drying at 110°C for 4h. The molecular sieve was an AFI structure molecular sieve, and the XRD pattern was similar to that of Example 1, indicating that the TiO2 was anatase TiO2, and the vanadium species did not form a crystal phase, but was dispersed in the catalyst in the form of a monolayer.

[0099] The preparation of the homomaleic anhydride was the same as in Example 1. The yield of the homomaleic anhydride was 85.9wt%.

[0100] Comparative Example 1

[0101] An AlPO4-5 catalyst was prepared without adding V and Ti elements.

[0102] Triethylamine as template agent, aluminum isopropoxide as aluminum source, phosphoric acid as phosphorus source. The raw materials were added according to the weight ratio of Al2O3:P2O5:R:H2O = 1:1.05:1.5:45. Then, the molecular sieve was obtained by crystallization at 180 ℃ for 16 h, filtration, washing, and drying at 110 ℃ for 4 h.

[0103] Preparation of pyromellitic dianhydride was the same as Example 1: the conversion rate of durene was less than 50%, and the catalyst activity was obviously insufficient.

[0104] Comparative Example 2

[0105] Preparation of AlPO4-5 catalyst without adding Ti element.

[0106] (1) Vanadyl sulfate VOSO4 was weighed and dispersed in water at a mass ratio of V to water of 1:10 at 50 ℃, and stirred and dissolved for 2 h to obtain a vanadium solution.

[0107] (2) Sodium hydroxide was added to the vanadium solution obtained in step (1) to adjust the pH value to 6 at 70 ℃, and the reaction was allowed to stand for 2 h to obtain a precipitate.

[0108] (3) 50wt% sulfuric acid solution was added to the suspension obtained in step (2) at a sulfuric acid:V molar ratio of 1:1 at 70 ℃, and mixed for 2 h to make the precipitate redissolve to obtain a sol state V source.

[0109] Triethylamine as template agent R, aluminum isopropoxide as aluminum source, phosphoric acid as phosphorus source, and the sol state V source prepared as V source. The raw materials were added according to the weight ratio of V2O5:Al2O3:P2O5:R:H2O = 0.15:1:1:1.5:45, and the pH value was adjusted to 5.5 with 10wt% ammonia water.

[0110] Then, the AIPO5 molecular sieve containing vanadium was obtained by crystallization at 190 ℃ for 16 h, filtration, washing, and drying at 110 ℃ for 4 h.

[0111] Preparation of pyromellitic dianhydride was the same as Example 1: the conversion rate of durene was less than 50%, and the catalyst activity was obviously insufficient.

[0112] The above only describes the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto, and any changes or replacements within the technical range disclosed by the present application can be easily thought of by those skilled in the art, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A molecular sieve catalyst for the gas-phase oxidation of mesitylene to synthesize homohydric anhydride, characterized in that, The molecular sieve catalyst comprises V, Al, P, O, and Ti elements, and contains, as oxides, 0.1wt%~10wt% V₂O₅, 30wt%~60wt% Al₂O₃, 30wt%~50wt% P₂O₅, and 1wt%~20wt% TiO₂; the molecular sieve has an AFI structure, wherein the Ti element exists in the form of TiO₂, and the TiO₂ exhibits anatase characteristics; Molecular sieve catalysts are prepared by hydrothermal crystallization. During the hydrothermal crystallization process, the vanadium element in the molecular sieve catalyst comes from a sol-state vanadium source.

2. The molecular sieve catalyst according to claim 1, wherein, The vanadium species in the catalyst do not form a crystalline phase, but are dispersed in the catalyst in the form of a monolayer; and / or Based on oxides, the catalyst contains 5wt%~9wt% V2O5, 35wt%~45wt% Al2O3, 35wt%~45wt% P2O5, and 3wt%~15wt% TiO2.

3. The method for preparing the molecular sieve catalyst according to claim 1 or 2, characterized in that, The preparation method includes: mixing a vanadium source, an aluminum source, a phosphorus source, a titanium source, water, and a template agent to obtain a mixed solution, followed by hydrothermal crystallization to obtain the molecular sieve; the vanadium source is added in the form of a sol-gel vanadium source.

4. The preparation method according to claim 3, wherein, The preparation method of the sol-state vanadium source includes the following steps: (1) Mix 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 precipitate; (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, An auxiliary agent is added to the mixture described in step (1); the auxiliary agent includes at least one of oxalic acid, citric acid, tartaric acid, and hydrogen peroxide; and / or The vanadium source mentioned in step (1) includes at least one of vanadium oxysulfate, vanadium pentoxide, ammonium metavanadate, vanadium oxyphosphate, vanadium hydroperoxide, and vanadium oxyoxate; and / or In step (1), the mass ratio of V to water is 1:5-15, the mixing and dissolution time is 1-2 hours, and the temperature is 40-60℃; and / or The alkali mentioned in step (2) includes at least one of sodium hydroxide, potassium hydroxide, and tetraethylammonium hydroxide, and the amount of alkali added is such that the pH of the mixture is 4-8; and / or the reaction temperature is 10-80°C. o C; reaction time is 1-3 hours; and / or The acid mentioned in step (3) includes at least one of sulfuric acid and nitric acid; the operating conditions include: 60-80℃, time of 1-3h, and acid concentration of 50-70wt%.

6. The preparation method according to claim 5, wherein, The molar ratio of the additive to V in the vanadium source is 1:0.5~1; and / or The concentration of hydrogen peroxide is 10-30 wt%; and / or The vanadium source mentioned in step (1) is one or more of vanadium oxysulfate, vanadium pentoxide, and ammonium metavanadate; and / or In step (2), the amount of alkali added is such that the pH of the mixture is 5.5–6.0; and / or The reaction temperature in step (2) is 50-70℃; and / or In step (3), the molar ratio of acid to V in the vanadium source is 1:0.5~2.

0.

7. The preparation method according to claim 6, wherein, The vanadium source mentioned in step (1) is ammonium metavanadate.

8. The preparation method according to claim 3, wherein, The aluminum source includes at least one of boehmite, aluminum isopropoxide, aluminum nitrate, and aluminum hydroxide; and / or The phosphorus source includes at least one of phosphoric acid, ammonium dihydrogen phosphate, pyrophosphate, and phosphorous acid; and / or The titanium source is at least one selected from titanium sulfate, tetrabutyl titanate, and isobutyl titanate; and / or The template agent includes at least one of triethylamine, tri-n-propylamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, and hexamethyleneimine; and / or By weight, the 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, where vanadium source is calculated as V2O5, aluminum source as Al2O3, P source as P2O5, and Ti source as TiO2.

9. The preparation method according to claim 8, wherein, The titanium source is titanium sulfate; and / or The template agent is a mixture of triethylamine and hexamethyleneimine, and the molar ratio of the two is 0.1-10:

1.

10. The preparation method according to claim 3, wherein, The pH of the mixture was controlled at 4.2–6.6; the hydrothermal crystallization temperature was 150–200 °C. o C; The hydrothermal crystallization time is 8~48h.

11. The preparation method according to claim 10, wherein, The pH of the mixture was controlled at 5.0-6.0; the hydrothermal crystallization temperature was 170-190℃; and the hydrothermal crystallization time was 10-24h.

12. A method for synthesizing homohydric anhydride by oxidizing mesitylene; homohydric anhydride is prepared by reacting mesitylene and oxygen-containing gas as raw materials in the presence of the molecular sieve catalyst described in claim 1 or 2.

13. The method according to claim 12, wherein, The reaction conditions included: a fixed-bed reactor and 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℃ o C, the reaction pressure is atmospheric pressure, and the oxygen-containing gas is air.

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