Catalyst for preparing pyromellitic dianhydride through durene oxidation, preparation method of catalyst and method for synthesizing pyromellitic dianhydride

Abstract

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

Description

Technical Field

[0001] The invention relates to the technical field of catalysis, and in particular to a catalyst for preparing anhydride by oxidizing durene, a preparation method thereof and a method for synthesizing anhydride. Background Art

[0002] With the rapid development of industries such as petroleum refining, polyester and chemical fiber, large-scale refinery units, aromatic disproportionation and isomerization units, etc. will produce a large amount of C10 aromatics as by-products. Nowadays, how to efficiently utilize C10 aromatic resources has become an important issue in petrochemicals. Pyromellitic dianhydride (PMDA, homoanhydride) is an important intermediate for high value-added fine chemicals with 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 from it can be widely used in high-end technical fields such as aviation and electronics industries. Therefore, it is of great significance to extract the high content of durenyl in the by-product C10 aromatics of refining and further process it into high value-added homoanhydride. Summary of the invention

[0003] In view of the problems existing in the prior art, the purpose of the present invention is to provide a new type of anhydride catalyst with a main active component that is more firmly bound. The catalyst is suitable for the industrial production of anhydride by gas-phase oxidation of durene, and has the characteristics of simple preparation process, high catalytic activity and high anhydride yield.

[0004] The present invention's research and analysis shows that the interaction between the active component and the carrier has an important influence on the preparation of anhydride by gas phase oxidation of durenyl. The existing technology for synthesizing anhydride by using durenyl as raw material mostly adopts gas phase oxidation method. Since this process is a complex multiphase catalytic process, there are many side reactions, resulting in a very low yield of anhydride. The gas phase oxidation method for preparing anhydride catalyst mainly adopts vanadium-titanium based spray-type catalyst, which is supplemented with a small amount of auxiliary elements to form a slurry, and the active component slurry is sprayed onto an inert carrier by spraying. The inert carrier is mostly made of α-Al 2 O 3 , silicon carbide and ceramic rings. However, for spray-type catalysts, the active components sprayed onto the inert carrier have a weak interaction with the carrier, and there is a risk of falling off during the reaction.

[0005] If a new type of anhydride catalyst with a carrier that is more firmly combined with the vanadium-titanium main active component can be developed, it will have important significance for the development of the synthetic anhydride industry and even the entire polyimide industry. Most of the molecular sieves in the prior art are mainly composed of Al, P and O. For the preparation of anhydride by vapor phase oxidation of durene of the present invention, the inventor believes that if V and Ti elements can be further effectively introduced and the composition state of Ti and V elements can be regulated, it is expected to synthesize an efficient catalyst for the oxidation of durene to prepare anhydride.

[0006] According to a first aspect of the present invention, the present invention provides a molecular sieve catalyst for synthesizing homoanhydride by gas phase oxidation of durene, wherein the molecular sieve catalyst comprises V, Al, P, O and Ti elements, and contains 0.1wt% to 10wt% V in terms of oxides. 2 O 5 , 30wt%~60wt%Al 2 O 3 , 30wt%~50wt%P 2 O 5 , 1wt%~20wt%TiO 2 The structure of the molecular sieve is AFI structure, wherein the Ti element is TiO 2 exists in the form of TiO 2 It is anatase type.

[0007] According to a second aspect of the present invention, the present invention provides a method for preparing 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 performing hydrothermal crystallization.

[0008] According to the third aspect of the present invention, the present invention provides a method for synthesizing homoanhydrides by oxidizing durenyl. In the presence of the molecular sieve catalyst of the present invention, homoanhydrides are prepared by reacting durenyl and oxygen-containing gas as raw materials.

[0009] The invention provides a molecular sieve catalyst for synthesizing anhydrides by gas phase oxidation of durenyl. The catalyst is suitable for industrial production of preparing anhydrides by gas phase oxidation of durenyl and has the characteristics of simple preparation process, high catalytic activity and high yield of anhydrides.

[0010] Compared with the prior art, the key of the present invention is that the catalyst uses a molecular sieve with a specific structure, which exerts an excellent performance of preparing anhydride by gas phase oxidation of durene, and obtains a higher yield of anhydride. When the catalyst of the present invention is used for synthesizing anhydride by gas phase oxidation of durene, the yield of anhydride can reach more than 85wt%, and a good technical effect is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This 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 invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0013] The present invention provides a molecular sieve catalyst for synthesizing homoanhydride by gas phase oxidation of durene. The molecular sieve catalyst comprises V, Al, P, O and Ti elements, and contains 0.1wt% to 10wt% V in terms of oxide. 2 O 5 , 30wt%~60wt%Al 2 O 3 , 30wt%~50wt%P 2 O 5 , 1wt%~20wt%TiO 2 The structure of the molecular sieve is AFI structure, wherein the Ti element is TiO 2 exists in the form of TiO 2 It is anatase type.

[0014] According to a preferred embodiment of the present invention, the vanadium species in the molecular sieve catalyst does not form a crystalline phase, but is dispersed in the catalyst in the form of a monomolecular layer. In the present invention, the monomolecular layer dispersion means that no obvious V 2 O 5 Crystalline characteristic diffraction peaks of the physical phase.

[0015] According to a preferred embodiment of the present invention, the catalyst contains 5 wt% to 9 wt% V in terms of oxide. 2 O 5 , 35wt%~45wt%Al 2 O 3 , 35wt%~45wt%P 2 O 5 , 3wt%~15wt%TiO 2 .

[0016] According to the present invention, the XRD diffraction spectrum 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, and 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° are attributed to anatase TiO 2 diffraction peaks.

[0017] In the present invention, 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° are attributed to anatase TiO 2The diffraction peaks of 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 of AFI structure.

[0018] According to a preferred embodiment of the present invention, the molecular sieve catalyst is prepared by a hydrothermal crystallization method; more preferably, during 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 invention, the method for preparing 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 react and generate a precipitate;

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

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

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

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

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

[0027] In the present invention, during the preparation of the colloidal vanadium source, the vanadium source includes at least one of vanadyl sulfate, vanadium pentoxide, ammonium metavanadate, vanadyl phosphate, vanadium hydrogen phosphate, and vanadyl oxalate, 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 invention has no special requirements for the preparation method of the molecular sieve catalyst. Any catalyst having the characteristics of the present invention can be used in the present invention. 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. According to the present invention, a preparation method of the molecular sieve catalyst is provided, which comprises: 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 to obtain the molecular sieve.

[0029] In the present invention, various raw materials can be adapted to the present invention, and the following is an exemplary description, but the scope of the present invention is not limited thereby.

[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 includes at least one of phosphoric acid, diammonium 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 includes 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 ratios can further improve the activity of the catalyst. In the embodiment of the present invention, 1:1 is used as an exemplary illustration to illustrate the advantages, but it is not limited to the scope of the present invention.

[0034] For example, by weight, 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, wherein the vanadium source is V 2 O 5 The aluminum source is Al 2 O 3 P source is P 2 O 5 Calculation, Ti source is TiO 2 count.

[0035] In the present invention, the pH of the mixed solution is preferably controlled to be 4.2 to 6.6, preferably 5.0 to 6.0. Preferably, the pH is adjusted with aqueous ammonia having a mass concentration of 10 wt% to 25 wt%.

[0036] According to the present invention, in the preparation method, the hydrothermal crystallization equipment is preferably an autoclave, and the pressure is autogenous pressure, which can be 1.0 to 2.5 MPa.

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

[0038] According to the present invention, in the preparation method, washing, filtering and drying steps can be performed after hydrothermal crystallization. Conventional parameters can be used for drying, preferably drying at 80-120° C. for 2-12 hours.

[0039] According to a preferred embodiment of the present invention, 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 a vanadium source with water to obtain a vanadium solution;

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

[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 invention, an auxiliary agent is added to the mixing in step (1); the auxiliary agent includes at least one of oxalic acid, citric acid, tartaric acid and hydrogen peroxide; preferably, the molar ratio of the added auxiliary agent to the V element in the vanadium source is 1:0.5-1, and when hydrogen peroxide is used, the concentration of hydrogen peroxide is 10-30wt%.

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

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

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

[0047] In the present invention, during the preparation of the colloidal vanadium source, the vanadium source includes at least one of vanadyl sulfate, vanadium pentoxide, ammonium metavanadate, vanadyl phosphate, vanadium hydrogen phosphate, and vanadyl oxalate, 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.

[0048] The invention provides a method for synthesizing homoanhydride by oxidation of durenyl. In the presence of the molecular sieve catalyst of the invention, durenyl and oxygen-containing gas are used as raw materials to react and prepare homoanhydride.

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

[0050] In the present invention, the reaction temperature is 420°C and the gas hourly volume space velocity is 5000h -1 , Raw material feed concentration 20g / m 3 The advantages of the present invention are explained as examples.

[0051] Example 1

[0052] (1) At 50°C, weigh vanadium oxysulfate VOSO 4 , dispersed in water at a mass ratio of V to water of 1:10, stirred and dissolved for 2 hours to obtain a vanadium solution.

[0053] (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.

[0054] (3) At 70° C., add 50 wt % sulfuric acid aqueous solution to the suspension obtained in step (2) at a sulfuric acid:V molar ratio of 1:1, and mix for 2 h to allow the precipitate to dissolve again, thereby obtaining a sol-state V source.

[0055] Using triethylamine as template R, aluminum isopropoxide as aluminum source, phosphoric acid as phosphorus source, titanium sulfate as titanium source, and the prepared sol-state V source as V source. 2 O 5 :Al 2 O 3 :P 2 O 5 :TiO 2 :R:H 2 The materials were added in a weight ratio of O=0.15:1:1:0.3:1.5:45, and the pH was adjusted to 5.5 with 10wt% ammonia water.

[0056] Then, the product was crystallized at 190°C for 16 hours, filtered, washed, and dried at 110°C for 4 hours to obtain the AIPO5 molecular sieve containing vanadium and titanium.

[0057] The XRD spectrum of the obtained molecular sieve is shown in Figure 1 . As can be seen from the figure, the molecular sieve is an AFI structure molecular sieve. The XRD diffraction spectrum 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, and 74.9°, among which 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 anatase TiO 2 There is no obvious diffraction peak of V in the XRD pattern. 2 O 5 The crystal characteristic diffraction peaks of the physical phase indicate that the vanadium species has not formed a crystal phase and is dispersed in the catalyst in the form of a monomolecular layer.

[0058] Preparation of homoanhydride:

[0059] Then, durene and air were used as raw materials in a fixed bed reactor to prepare homoanhydride in the presence of a catalyst; at a reaction temperature of 420°C and a gas hourly space velocity of 5000 h -1 , Raw material feed concentration 20g / m 3 (refers to durene, per m 3 When 20 g durene was added under air, the yield of homoanhydride was measured to be 85.3 wt%.

[0060] Example 2

[0061] (1) At 50°C, weigh V 2 O 5 , dispersed in water at a mass ratio of V to water of 1:10, added with 20wt% hydrogen peroxide at a molar ratio of the auxiliary agent to V of 1:0.8, stirred and dissolved for 2h to obtain a vanadium solution.

[0062] (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 h to obtain a precipitate.

[0063] (3) At 70° C., 50 wt % sulfuric acid was added to the suspension obtained in step (2) at a sulfuric acid:V molar ratio of 1:1, and mixed for 2 h to allow the precipitate to dissolve again, thereby obtaining a sol-state V source.

[0064] Using triethylamine as template R, pseudoboehmite as aluminum source, phosphoric acid as phosphorus source, titanium sulfate as titanium source, and the prepared sol-state V source as V source. 2 O 5 :Al 2 O 3 :P 2 O 5 :TiO 2 :R:H 2 O=0.2:1:1.1:0.3:1.5:45 weight ratio, and adjust pH to 5.5 with sodium hydroxide. Then crystallize at 190℃ for 24h, filter, wash, and dry at 100℃ for 3h to obtain AIPO5 molecular sieve containing vanadium and titanium. The molecular sieve is AFI structure molecular sieve, and the XRD spectrum is similar to that of Example 1, indicating that TiO 2 Anatase TiO 2 The vanadium species did not form a crystalline phase and was dispersed in the catalyst in the form of a monomolecular layer.

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

[0066] Example 3

[0067] (1) At 50°C, weigh VOSO 4 , disperse it in water at a mass ratio of V to water of 1:10, and stir to dissolve for 2 hours.

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

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

[0070] Tetraethylammonium hydroxide is used as the template R, aluminum isopropoxide is used as the aluminum source, phosphoric acid is used as the phosphorus source, titanium sulfate is used as the titanium source, and the prepared sol-state V source is used as the V source. 2 O 5 :Al 2 O 3 :P 2 O 5 :TiO 2 :R:H 2 O=0.2:1:1:0.1:1.2:40, and the pH was adjusted to 5.5 with sodium hydroxide.

[0071] Then, crystallization was carried out at 180°C for 10 h, and after filtration, washing, and drying at 120°C for 3 h, an AIPO5 molecular sieve containing vanadium and titanium was obtained. The molecular sieve was an AFI structure molecular sieve, and the XRD spectrum was similar to that of Example 1, indicating that TiO 2 Anatase TiO 2 The vanadium species did not form a crystalline phase and was dispersed in the catalyst in the form of a monomolecular layer.

[0072] The preparation of the anhydride was the same as in Example 1: the yield of the anhydride was measured to be 84.2 wt%.

[0073] Example 4

[0074] (1) At 50°C, weigh VOSO 4 , dispersed in water at a mass ratio of V to water of 1:10, added 20wt% hydrogen peroxide at a molar ratio of auxiliary agent to V of 1:0.5, and stirred to dissolve for 2h.

[0075] (2) At 70° C., sodium hydroxide was added to the solution obtained in step (1), the pH value was adjusted to 5.5, and the reaction was allowed to stand for 2 h to obtain a precipitate.

[0076] (3) At 70° C., 60 wt % phosphoric acid was added to the suspension obtained in step (2) at a phosphoric acid:V ratio of 1:1, and mixed for 2 h to allow the precipitate to dissolve again, thereby obtaining a sol-state V source.

[0077] Triethylamine was used as the template, aluminum isopropoxide was used as the aluminum source, phosphoric acid was used as the phosphorus source, and titanium sulfate was used as the titanium source. 2 O 5 :Al 2 O 3 :P 2 O 5 :TiO 2 :R:H 2 O=0.15:1:1.05:0.3:1.5:45 weight ratio, and adjust pH to 5.5 with 10wt% ammonia water. Then crystallize at 180℃ for 12h, filter, wash, and dry at 110℃ for 4h to obtain AIPO5 molecular sieve containing vanadium and titanium. The molecular sieve is AFI structure molecular sieve, and the XRD spectrum is similar to that of Example 1, indicating that TiO 2 Anatase TiO 2 The vanadium species did not form a crystalline phase and was dispersed in the catalyst in the form of a monomolecular layer.

[0078] The preparation of the anhydride was the same as in Example 1: the yield of the anhydride was measured to be 84.3 wt%.

[0079] Example 5

[0080] (1) At 50°C, weigh VOSO 4 , dispersed in water at a mass ratio of V to water of 1:10, added citric acid at a molar ratio of the additive to V of 1:1.0, and stirred 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 mixture was allowed to react for 2 h to obtain a precipitate.

[0082] (3) At 70° C., 60 wt % phosphoric acid was added to the suspension obtained in step (2) at a phosphoric acid:V ratio of 1:1, and mixed for 2 h to allow the precipitate to dissolve again, thereby obtaining a sol-state V source.

[0083] Tetraethylammonium hydroxide was used as a template, 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 prepared sol-state V source was used as a V source. 2 O 5 :Al 2 O 3 :P 2 O 5 :TiO 2 :R:H 2O=0.15:1:1:0.2:1.5:40, and the pH was adjusted to 5.5 with sodium hydroxide. Then, crystallization was carried out at 170°C for 20 hours, and after filtration, washing, and drying at 90°C for 5 hours, an AIPO5 molecular sieve containing vanadium and titanium was obtained. The molecular sieve was an AFI structure molecular sieve, and the XRD spectrum was similar to that of Example 1, indicating that TiO 2 Anatase TiO 2 The vanadium species did not form a crystalline phase and was dispersed in the catalyst in the form of a monomolecular layer.

[0084] The preparation of the anhydride was the same as in Example 1: the yield of the anhydride was measured to be 84.1 wt%.

[0085] Example 6

[0086] Tetraethylammonium hydroxide is used as a template, aluminum isopropoxide is used as an aluminum source, phosphoric acid is used as a phosphorus source, titanium sulfate is used as a titanium source, and ammonium metavanadate is used as a V source. 2 O 5 :Al 2 O 3 :P 2 O 5 :TiO 2 :R:H 2 O=0.15:1:1:0.2:1.5:40, and the pH was adjusted to 5.5 with sodium hydroxide. Then, crystallization was carried out at 170°C for 20 hours, and after filtration, washing, and drying at 90°C for 5 hours, an AIPO5 molecular sieve containing vanadium and titanium was obtained. The molecular sieve was an AFI structure molecular sieve, and the XRD spectrum showed V at 20.3 and 31.0. 2 O 5 The characteristic diffraction peaks of the species indicate that the vanadium species forms a crystalline phase and is not dispersed in the catalyst in the form of a single molecular layer.

[0087] The preparation of the anhydride was the same as in Example 1: the yield of the anhydride was measured to be 81.7 wt%.

[0088] Example 7

[0089] (1) At 50°C, weigh V 2 O 5 , dispersed in water at a mass ratio of V to water of 1:10, added with 20wt% hydrogen peroxide at a molar ratio of the auxiliary agent to V of 1:0.8, stirred and dissolved 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 reaction was allowed to stand for 2 h to obtain a precipitate.

[0091] (3) At 70° C., 50 wt % sulfuric acid was added to the suspension obtained in step (2) at a sulfuric acid:V molar ratio of 1:1, and mixed for 2 h to allow the precipitate to dissolve again, thereby obtaining a sol-state V source.

[0092] A mixture of triethylamine and hexamethyleneimine (molar ratio 1:1) was used as the template R, pseudoboehmite was used as the aluminum source, phosphoric acid was used as the phosphorus source, titanium sulfate was used as the titanium source, and the prepared sol-state V source was used as the V source. 2 O 5 :Al 2 O 3 :P 2 O 5 :TiO 2 :R:H 2 O=0.2:1:1.1:0.3:1.5:45 weight ratio, and adjust pH to 5.5 with sodium hydroxide. Then crystallize at 190℃ for 24h, filter, wash, and dry at 100℃ for 3h to obtain AIPO5 molecular sieve containing vanadium and titanium. The molecular sieve is AFI structure molecular sieve, and the XRD spectrum is similar to that of Example 1, indicating that TiO 2 Anatase TiO 2 The vanadium species did not form a crystalline phase and was dispersed in the catalyst in the form of a monomolecular layer.

[0093] Preparation of the anhydride was the same as in Example 1: the yield of the anhydride was 86.1 wt%.

[0094] Example 8

[0095] (1) At 50°C, weigh ammonium metavanadate and disperse it in water at a mass ratio of V to water of 1:10. Add oxalic acid at a molar ratio of the additive to V of 1:0.5 and stir to dissolve for 2 h.

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

[0097] (3) At 70° C., 60 wt % phosphoric acid was added to the suspension obtained in step (2) at a phosphoric acid:V ratio of 1:1, and mixed for 2 h to allow the precipitate to dissolve again, thereby obtaining a sol-state V source.

[0098] Triethylamine was used as the template, aluminum isopropoxide was used as the aluminum source, phosphoric acid was used as the phosphorus source, and titanium sulfate was used as the titanium source. 2 O 5 :Al 2 O 3 :P 2 O 5 :TiO 2 :R:H 2O=0.15:1:1.05:0.3:1.5:45 weight ratio, and adjust pH to 5.5 with 10wt% ammonia water. Then crystallize at 180℃ for 12h, filter, wash, and dry at 110℃ for 4h to obtain AIPO5 molecular sieve containing vanadium and titanium. The molecular sieve is AFI structure molecular sieve, and the XRD spectrum is similar to that of Example 1, indicating that TiO 2 Anatase TiO 2 The vanadium species did not form a crystalline phase and was dispersed in the catalyst in the form of a monomolecular layer.

[0099] The preparation of the anhydride was the same as in Example 1: the yield of the anhydride was measured to be 85.9 wt%.

[0100] Comparative Example 1

[0101] AlPO without adding V and Ti elements 4 -5 catalyst preparation.

[0102] Triethylamine was used as the template, aluminum isopropoxide was used as the aluminum source, and phosphoric acid was used as the phosphorus source. 2 O 3 :P 2 O 5 :R:H 2 O=1:1.05:1.5:45, then crystallize at 180℃ for 16h, filter, wash, and dry at 110℃ for 4h to obtain molecular sieve.

[0103] The preparation of homoanhydride was the same as in Example 1: the measured conversion rate of durene was <50%, and the catalyst activity was obviously insufficient.

[0104] Comparative Example 2

[0105] AlPO without adding Ti element 4 -5 catalyst preparation.

[0106] (1) At 50°C, weigh vanadium oxysulfate VOSO 4 , dispersed in water at a mass ratio of V to water of 1:10, stirred and dissolved for 2 hours to obtain a vanadium solution.

[0107] (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.

[0108] (3) At 70° C., 50 wt % sulfuric acid solution was added to the suspension obtained in step (2) at a sulfuric acid:V molar ratio of 1:1, and mixed for 2 h to allow the precipitate to dissolve again, thereby obtaining a sol-state V source.

[0109] Triethylamine was used as the template agent R, aluminum isopropoxide was used as the aluminum source, phosphoric acid was used as the phosphorus source, and the prepared sol-state V source was used as the V source. 2 O 5 :Al 2 O 3 :P 2 O 5 :R:H 2 The materials were added in a weight ratio of O=0.15:1:1:1.5:45, and the pH was adjusted to 5.5 with 10wt% ammonia water.

[0110] Then, the product was crystallized at 190° C. for 16 h, filtered, washed, and dried at 110° C. for 4 h to obtain the vanadium-containing AIPO5 molecular sieve.

[0111] The preparation of the average anhydride was the same as in Example 1: the average anhydride yield was measured to be 74.2 wt%.

[0112] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A molecular sieve catalyst for synthesizing homoanhydrides by gas phase oxidation of durene, characterized in that: The molecular sieve catalyst includes V, Al, P, O and Ti elements, and contains 0.1wt% to 10wt% V2O5, 30wt% to 60wt% Al2O3, 30wt% to 50wt% P2O5, and 1wt% to 20wt% TiO2 in terms of oxides; the structure of the molecular sieve is an AFI structure, wherein the Ti element exists in the form of TiO2, and TiO2 is anatase-type.

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 monomolecular layer; and / or The catalyst contains 5wt% to 9wt% V2O5, 35wt% to 45wt% Al2O3, 35wt% to 45wt% P2O5, and 3wt% to 15wt% TiO2, calculated as oxides; and / or The molecular sieve catalyst is prepared by hydrothermal crystallization method; More preferably, during the hydrothermal crystallization process, the vanadium element of the molecular sieve catalyst comes from a sol-state vanadium source.

3. The molecular sieve catalyst according to claim 1 or 2, wherein: The XRD diffraction pattern of the 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, and 74.9°, among which 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 rutile TiO2.

4. The method for preparing the molecular sieve catalyst according to any one of claims 1 to 3, characterized in that: The preparation method comprises: mixing a vanadium source, an aluminum source, a phosphorus source, a titanium source, water and a template agent to obtain a mixed solution, and performing hydrothermal crystallization to obtain the molecular sieve.

5. The preparation method according to claim 4, wherein: 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: (1) mixing a vanadium source with water to obtain a vanadium solution; (2) adding a base to the vanadium solution obtained in step (1) to react and generate a precipitate; (3) Adding acid to the product of step (2) to obtain a sol-state vanadium source.

6. The preparation method according to claim 5, wherein: Adding an auxiliary agent to the mixing in step (1); the auxiliary agent comprises at least one of oxalic acid, citric acid, tartaric acid and hydrogen peroxide; preferably, the molar ratio of the amount of the auxiliary agent added to the V element in the vanadium source is 1:0.5-1, preferably, the concentration of the hydrogen peroxide is 10-30wt%; and / or The vanadium source in step (1) comprises at least one of vanadyl sulfate, vanadium pentoxide, ammonium metavanadate, vanadyl phosphate, vanadyl hydrogen phosphate, and vanadyl oxalate, preferably one or more of vanadyl sulfate, vanadium pentoxide, and ammonium metavanadate, more preferably ammonium metavanadate; and / or In step (1), the mass ratio of V to water is 1:5-15, the mixing and dissolving time is 1-2 hours, and the temperature is 40-60° C.; and / or The base in step (2) comprises at least one of sodium hydroxide, potassium hydroxide and tetraethylammonium hydroxide, and the amount of base added is such that the pH value of the mixture is 4 to 8, preferably 5.5 to 6.0; and / or the reaction temperature is 10 to 80° C., preferably 50 to 70° C.; the reaction time is 1 to 3 h; and / or The acid in step (3) includes at least one of sulfuric acid and nitric acid; preferably, the molar ratio of the acid to the V element in the vanadium source is 1:0.5-2.0, and the operating conditions include: 60-80°C, time is 1-3h, and the acid concentration is 50-70wt%.

7. The preparation method according to claim 5 or 6, wherein: The aluminum source comprises at least one of pseudo-boehmite, aluminum isopropoxide, aluminum nitrate, and aluminum hydroxide; and / or The phosphorus source comprises at least one of phosphoric acid, diammonium phosphate, pyrophosphoric acid and phosphorous acid; and / or The titanium source is at least one of titanium sulfate, tetrabutyl titanate and isobutyl titanate, preferably titanium sulfate; and / or The template agent includes 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; and / or By weight, vanadium source: aluminum source: phosphorus source: titanium source: template: water = 0.01-0.35:1:0.5-1.3:0.03-0.7:1-5:30-200, 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.

8. The preparation method according to claim 4, wherein: The pH of the mixed solution is controlled to be 4.2 to 6.6, preferably 5.0 to 6.0; the temperature of the hydrothermal crystallization is 150 to 200° C., preferably 170 to 190° C.; the time of the hydrothermal crystallization is 8 to 48 hours, preferably 10 to 24 hours.

9. A method for synthesizing homoanhydrides by oxidation of durenyl; in the presence of the molecular sieve catalyst according to any one of claims 1 to 3, homoanhydrides are prepared by reaction with durenyl and oxygen-containing gas as raw materials.

10. The method according to claim 9, wherein: The reaction conditions include: using a fixed bed reactor, the mass concentration of durene is 15 to 45 g / m 3 , volume space velocity is 4000~8000hr -1 , the reaction temperature is 330-500°C, the reaction pressure is normal pressure, and the oxygen-containing gas is air.

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