Catalyst for oxidizing durene to prepare homoanhydride, preparation method and application thereof

Abstract

The present invention relates to the technical field of catalysts, and discloses a catalyst for the gas-phase oxidation of durene to pyromellitic dianhydride, its preparation method and application. The catalyst is a three-stage bed catalyst, including section A, section B and section C catalysts sequentially arranged from the gas inlet end to the gas outlet end. The catalysts in sections A, B and C each include a carrier and an active substance supported on the carrier. The active substance includes V, Cs, Ti, a promoter component and optionally P; wherein, based on the mass content of the total amount of the active substance in each section of the catalyst, the arrangement order of the mass percentage content of the V element in each section of the catalyst in the corresponding three sections of the catalyst is section B catalyst < section A catalyst < section C catalyst. This catalyst has high activity and overall utilization efficiency of the catalyst. The method for the gas-phase oxidation of durene to pyromellitic dianhydride using this catalyst not only has a high pyromellitic dianhydride yield, but also has a high load.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and more particularly to a catalyst for preparing pyromellitic dianhydride by gas-phase oxidation of durene, and a preparation method and application thereof. Background Art

[0002] Pyromellitic dianhydride (1,2,4,5-pyromellitic dianhydride, hereinafter referred to as "pyromellitic anhydride") is a very important chemical raw material. Pyromellitic anhydride and its derivatives have a wide range of important applications, particularly as a key monomer in the production of polyimides. Due to their comprehensive performance at high temperatures, polyimides are currently the most widely used organic polymer materials in the widest temperature range, offering excellent dimensional stability, radiation resistance, mechanical properties, electrical properties, and corrosion resistance at high temperatures.

[0003] In the past, the production of pyromellitic anhydride from durenyl was primarily achieved through a liquid-phase oxidation process, where the raw material was oxidized to acid, which was then dehydrated to anhydride. Currently, the most widely used method involves using durenyl as the raw material and producing pyromellitic dianhydride in a single step through air oxidation. This method is characterized by its simplicity, eliminating the dehydration step to anhydride. Using air as the oxidant eliminates the need for the catalyst separation step required in liquid-phase oxidation processes, allows for continuous production, and is easily automated.

[0004] The catalyst compositions of the prior art for preparing pyromellitic dianhydride are mostly oxides of elements such as V / Ti / Mo / Fe. Chinese patent document CN107866241A discloses a catalyst for the oxidation of durenyl to produce homogenous anhydride, which uses an oxide catalyst, wherein the catalyst uses α-Al2O3, silicon carbide, porcelain rings, or a mixture thereof as a carrier, and the active components include vanadium, titanium, and at least one of Group VA elements and alkali metal elements. Chinese patent document CN107866257A discloses a catalyst for the production of homogenous anhydride from durenyl. It uses an oxide catalyst, wherein the catalyst uses α-Al2O3, silicon carbide, porcelain rings, or a mixture thereof as a carrier, and the active components include vanadium, iron-based elements, and at least one of Group IIB elements and alkali metal elements. However, the yield of homogenous anhydride in the above-mentioned documents needs to be further improved.

[0005] Therefore, how to provide a catalyst for preparing pyromellitic dianhydride by gas-phase oxidation of durene to further improve the yield of durene dianhydride is a current research direction. Summary of the Invention

[0006] Aiming at the problem of low yield of pyromellitic dianhydride in the gas-phase oxidation of mesitylene to pyromellitic dianhydride in the prior art, the present invention provides a catalyst for the oxidation of mesitylene to pyromellitic dianhydride, its preparation method and application. This catalyst has high activity and overall utilization efficiency of the catalyst. The method for the gas-phase oxidation of mesitylene to pyromellitic dianhydride using this catalyst not only has a high yield of pyromellitic dianhydride, but also has a high load.

[0007] One of the objectives of the present invention is to provide a catalyst. The catalyst is a three-stage bed catalyst, including an A-stage catalyst, a B-stage catalyst and a C-stage catalyst arranged in sequence from the gas inlet end to the gas outlet end. Each of the A-stage catalyst, B-stage catalyst and C-stage catalyst includes a carrier and an active substance supported on the carrier. The active substance includes V, Cs, Ti, a promoter component and optionally P; the promoter component is selected from at least one of the metal elements in the fourth period, fifth period and sixth period except V, Cs and Ti; wherein, based on the mass content of the total amount of the active substance in each stage of the catalyst, the arrangement order of the mass percentage content of the V element in each stage of the catalyst in the corresponding three-stage catalyst is B-stage catalyst < A-stage catalyst < C-stage catalyst.

[0008] According to the present invention, based on the mass of each stage of the catalyst, the arrangement order of the mass percentage content of the V element in the corresponding three-stage catalyst is B-stage catalyst < A-stage catalyst < C-stage catalyst. Such a three-stage bed catalyst has good technical effects. In a preferred embodiment of the present invention, based on the mass content of the total amount of the active substance in each stage of the catalyst being 100%, each stage of the catalyst includes: 4% - 12% of V2O5; 0 - 0.5% of P2O5; 0 - 1% of Cs2O; 1% - 10% of the promoter component; and TiO2. More preferably, based on the mass content of the total amount of the active substance in each stage of the catalyst being 100%, each stage of the catalyst includes: 4.5% - 7.5% of V2O5; 0 - 0.4wt% of P2O5; 0.22wt% - 0.61wt% of Cs2O; 1.8wt% - 2.8wt% of the promoter component calculated as metal oxide; and TiO2.

[0009] The V in each stage of the catalyst can be selected within a relatively wide range. In a preferred embodiment of the present invention, based on the mass content of the total amount of the active substance in each stage of the catalyst being 100%, the content of V is calculated as V2O5. The content of V2O5 in the A-stage catalyst is 5wt% - 7wt%; the content of V2O5 in the B-stage catalyst is 4wt% - 6wt%; the content of V2O5 in the C-stage catalyst is 6wt% - 8wt%;

[0010] In a more preferred embodiment of the present invention, taking the total mass content of active substances in each stage catalyst as 100%, the mass content of V is calculated as V2O5, the V2O5 content in the stage A catalyst is 5.6wt%-6.5wt%; the V2O5 content in the stage B catalyst is 4.5wt%-5.5wt%; and the V2O5 content in the stage C catalyst is 6.6wt%-7.5wt%.

[0011] According to the present invention, the active material loading in each catalyst stage can be selected within a wide range. In a preferred embodiment of the present invention, based on the mass content of the respective carrier in each catalyst stage being 100%, the active material loading in each catalyst stage is 12 wt%-17 wt%, preferably 13 wt%-16.5 wt%. That is, the mass ratio of the active material loading in each catalyst stage to the corresponding carrier is (12-17):100, preferably (13-16.5):100.

[0012] According to the present invention, the active substances other than V in each stage catalyst can be selected within a wide range. In a preferred embodiment of the present invention, taking the total mass content of the active substances in each stage catalyst as 100%, the stage A catalyst, the stage B catalyst and the stage C catalyst each further contain: 0-0.5wt% P2O5; 0.1wt%-1wt% Cs2O; and 1wt%-10wt% of a co-catalyst component calculated as a metal oxide.

[0013] According to the present invention, the active substances other than V in each stage catalyst can be selected within a wide range. In a preferred embodiment of the present invention, taking the total mass content of the active substances in each stage catalyst as 100%, the stage A catalyst, the stage B catalyst and the stage C catalyst each further contain: 0-0.4wt% P2O5; 0.22wt%-0.61wt% Cs2O; 1.8wt%-2.8wt% of a co-catalyst component calculated as a metal oxide; and the remainder of the active substance is TiO2.

[0014] According to the present invention, the co-catalyst component can be selected from a wide range. In a preferred embodiment of the present invention, the co-catalyst component is selected from at least one of rubidium, cerium, niobium, chromium, tungsten, silver, cobalt, gallium, indium, antimony, bismuth, zirconium and erbium elements; preferably, the co-catalyst component is selected from at least one of niobium, antimony and zirconium, for example, it can be one, two or three.

[0015] According to the present invention, the carrier material can be selected from a wide range. In a preferred embodiment of the present invention, the carrier material is selected from at least one of steatite ring, silicon carbide, silicon dioxide, quartz and ceramics.

[0016] According to the present invention, the volume ratio of the stage A catalyst, the stage B catalyst and the stage C catalyst can be selected within a wide range. In a preferred embodiment of the present invention, the volume ratio of the stage A catalyst, the stage B catalyst and the stage C catalyst is 1:(0.8-1):(0.6-1).

[0017] According to the present invention, the content of active components in the stage A catalyst can be selected within a wide range. In a more preferred embodiment of the present invention, based on the mass content of the total amount of active substances in the stage A catalyst as 100%, the stage A catalyst contains: 5.6wt%-6.5wt% of V2O5; 0-0.01wt% of P2O5; 0.3wt%-0.39wt% of CsO2; and 2.2wt%-2.4wt% of co-catalyst components.

[0018] According to the present invention, the content of active components in the stage B catalyst can be selected within a wide range. In a more preferred embodiment of the present invention, based on the total mass content of active substances in the stage B catalyst being 100%, the stage B catalyst contains: 4.5wt%-5.5wt% of V2O5; 0.48wt%-0.61wt% of CsO2; and 1.9wt%-2.3wt% of a co-catalyst component.

[0019] According to the present invention, the content of active components in the C-stage catalyst can be selected within a wide range. In a more preferred embodiment of the present invention, based on the mass content of the total amount of active substances in the C-stage catalyst as 100%, the C-stage catalyst contains: 6.5wt%-7.5wt% of V2O5; 0.34wt%-0.38wt% of P2O5; 0.22wt%-0.25wt% of CsO2; and 2.7wt%-3wt% of co-catalyst components.

[0020] In a more preferred embodiment of the present invention, the catalyst contains, based on the total mass content of active substances in the stage A catalyst as 100%, 5.6wt%-6.5wt% of V2O5; 0-0.01wt% of P2O5; 0.3wt%-0.39wt% of CsO2; 2.2wt%-2.4wt% of the promoter component; based on the total mass content of active substances in the stage B catalyst as 100%, the stage B catalyst contains: 4.5wt% t%-5.5wt% of V2O5;; 0.48wt%-0.61wt% of CsO2; 1.9wt%-2.3wt% of co-catalyst components; based on the mass content of the total amount of active substances in the C-stage catalyst as 100%, the C-stage catalyst contains: 6.5wt%-7.5wt% of V2O5; 0.34wt%-0.38wt% of P2O5; 0.22wt%-0.25wt% of CsO2; 2.7wt%-3wt% of co-catalyst components.

[0021] More preferably, based on the mass content of the respective carriers in each stage catalyst being 100%, the loading amount of the active substance in each stage catalyst is 12wt%-17wt%, and the remainder of the active substance in the stage A catalyst, the stage B catalyst and the stage C catalyst is TiO2.

[0022] A second object of the present invention is to provide a method for preparing the catalyst described above, comprising loading a vanadium compound, a cesium compound, a titanium compound, a compound containing a co-catalyst component, and an optional phosphorus compound on a carrier according to their composition and ratio to obtain a stage A catalyst, a stage B catalyst, and a stage C catalyst, respectively; and loading the stage A catalyst, the stage B catalyst, and the stage C catalyst in sequence from the gas inlet end to the gas outlet end to obtain a three-stage bed catalyst.

[0023] In a preferred embodiment of the present invention, the preparation methods of the stage A catalyst, the stage B catalyst and the stage C catalyst each include: step A: adding oxalic acid, a vanadium compound, a cesium compound and an optional phosphorus compound to a solvent and dissolving them to form a solution; step B: mixing the solution obtained in step A with titanium dioxide, a compound containing a co-catalyst component and a binder to form a spray slurry; step C: spraying the spray slurry onto a carrier material and then drying it.

[0024] In a preferred embodiment of the present invention, in step A, the solvent is a mixed solution of water and a water-soluble organic solvent; preferably, the water-soluble organic solvent is selected from at least one of methanol, ethanol, formamide and N,N-dimethylamide; the mass ratio of the water-soluble organic solvent to water is (0.1-1):1, preferably (0.1-0.7):1.

[0025] In a preferred embodiment of the present invention, the vanadium compound is selected from ammonium metavanadate and / or vanadium pentoxide.

[0026] In a preferred embodiment of the present invention, the phosphorus compound is selected from at least one of diammonium phosphate, triammonium phosphate and phosphorus pentoxide.

[0027] In a preferred embodiment of the present invention, the cesium compound is selected from at least one of cesium nitrate, cesium sulfate and cesium chloride.

[0028] In a preferred embodiment of the present invention, in step A, the mass ratio of the solvent to oxalic acid is 100:(15-25); preferably 100:(18-24); the mass ratio of the solvent to the vanadium compound is 100:(7-11); preferably 100:(6.5-10); the mass ratio of the solvent to the phosphorus compound is 100:(0-0.8); preferably 100:(0.1-0.72); the mass ratio of the solvent to the cesium compound is 100:(0.1-1); preferably 100:(0.3-0.9).

[0029] In a preferred embodiment of the present invention, in step B, the titanium dioxide is anatase titanium dioxide with a specific surface area of 10m 2 / g-30m 2 / g, preferably 15m 2 / g-25m 2 / g.

[0030] In a preferred embodiment of the present invention, the adhesive is at least one of vinyl acetate acrylate copolymer, vinyl acetate ethylene copolymer, vinyl acetate maleate copolymer and acrylic acid maleic acid copolymer.

[0031] In a preferred embodiment of the present invention, in step B, the viscosity of the spray slurry obtained is 10Pa·s-40Pa·s, preferably 12Pa·s-25Pa·s. Preferably, the binder used in the present invention is a copolymerized vinyl acetate emulsion, and the viscosity of the catalyst active component slurry is controlled to 10Pa·s-40Pa·s, preferably 12Pa·s-25Pa·s by controlling the amount of binder added. In the preparation method described in the present invention, the binder is at least one of the following: vinyl acetate / acrylate, vinyl acetate / ethylene, vinyl acetate / maleic acid ester, and acrylic acid / maleic acid copolymer.

[0032] In a preferred embodiment of the present invention, the mass ratio of the solvent in step A to the mass ratio of titanium dioxide, the compound containing the co-catalyst component, and the binder in step B is 100:(100-110):(2-4.5):(13-25); preferably 100:(103-107):(2.8-4.4):(13.5-22.5).

[0033] In a preferred embodiment of the present invention, the carrier temperature is 80°C-130°C; and / or,

[0034] The drying temperature is 100-120° C.; and / or the spraying rate is 30-60 ml / min.

[0035] In a preferred embodiment of the present invention, the preparation method of the catalyst for producing anhydride by oxidation of durene comprises:

[0036] Step A: adding oxalic acid, a vanadium compound, a cesium compound and an optional phosphorus compound into a solvent and dissolving them to prepare a solution;

[0037] Step B: The solution obtained in step A, titanium dioxide, a compound containing a co-catalyst component, and a binder are thoroughly ball-milled to prepare a spray slurry;

[0038] Step C: spraying the spray slurry onto a support material and drying with hot air to obtain the catalyst.

[0039] More preferably, in step A, the solvent is a mixed solution of water and a water-soluble organic solvent; the water-soluble organic solvent is selected from at least one of methanol, ethanol, formamide, and N,N-dimethylamide; the mass ratio of the water-soluble organic solvent to water is (0.1-1):1, preferably (0.1-0.7):1.

[0040] In the preparation method of the present invention, the amount of the vanadium compound, phosphorus compound, cesium compound, titanium dioxide, and compound containing a co-catalyst component added is preferably such that the content of the active component in the final catalyst is within the range described in the present invention, and technicians can adjust it according to actual conditions; in the present invention, the above range can be preferably adopted.

[0041] In a more preferred embodiment of the present invention, the method for preparing the catalyst comprises:

[0042] Step A: adding oxalic acid, a vanadium compound, a phosphorus compound, and a cesium compound into a certain amount of solvent and dissolving them to prepare a solution;

[0043] Step B: Add the solution obtained in step A, titanium dioxide, a co-catalyst, and an appropriate amount of a binder into a ball mill and mix them thoroughly to prepare a slurry to be sprayed;

[0044] Step C: using a spraying device, spray the slurry to be sprayed onto the carrier material at a spraying rate of 30 ml / min under the conditions that the carrier temperature reaches 130° C. and the hot air temperature is 100° C., to prepare a homogeneous anhydride catalyst.

[0045] Preferably, in the preparation method of the present invention, the vanadium compound is one or more selected from ammonium metavanadate and vanadium pentoxide, preferably ammonium metavanadate; and / or the phosphorus compound is one or more selected from ammonium dihydrogen phosphate, triammonium phosphate and phosphorus pentoxide, preferably ammonium dihydrogen phosphate; and / or the cesium compound is one or more selected from cesium nitrate, cesium sulfate and cesium chloride, preferably cesium sulfate.

[0046] In the preparation method described in the present invention, the spraying amount of the catalytically active components of the catalyst is controlled by means of the drum speed, spraying rate, loss rate and spraying time, so that the obtained catalyst has both high activity and can reduce the generation of by-products, thereby improving the mass yield of the anhydride.

[0047] A third object of the present invention is to provide a method for oxidizing durenyl to produce pyromellitic anhydride, comprising contacting a mixed gas containing durenyl and air with the catalyst described above or the catalyst prepared by the preparation method described above, and performing an oxidation reaction to obtain pyromellitic dianhydride.

[0048] According to the present invention, the catalytic reaction temperature can be selected within a wide range. In a preferred embodiment of the present invention, the reaction temperature is 300°C-450°C, preferably 330°C-400°C.

[0049] According to the present invention, the air velocity can be selected within a wide range. In a preferred embodiment of the present invention, the air velocity is 1500 h -1 -5000h -1 , preferably 4000h -1 -5000h -1 .

[0050] According to the present invention, the mass concentration of durenyl can be selected within a wide range. In a preferred embodiment of the present invention, the mass concentration of durenyl is 50-70 g / m 3 , preferably 55-65g / m 3 .

[0051] In a more preferred embodiment of the present invention, the reaction temperature is 300°C-450°C, preferably 330°C-400°C; the air space velocity is 1500h -1 -5000h -1 , preferably 4000h -1 -5000h -1 ; The mass concentration of durene is 50-70g / m3 , preferably 55-65 g / m 3 .

[0052] According to the present invention, the pressure used in the method for oxidizing pseudocumene to pyromellitic anhydride can be negative pressure, atmospheric pressure and positive pressure, and preferably the reaction is carried out under atmospheric pressure.

[0053] The process of the present invention uses a fixed-bed reactor and adopts molten salt circulation for heat exchange. During the evaluation of the reaction process, there is a temperature distribution in the catalyst bed layer. The highest value in the temperature region is called the reaction hot spot temperature. In the present invention, a thermocouple is used to measure the temperature of the pulling bed layer. The concentration of pseudocumene refers to the number of grams of pseudocumene contained in unit volume of air. The higher the value, the higher the content of pseudocumene in the air.

[0054] Through the above technical solution, the catalyst in the present invention adopts the design of a three-stage bed catalyst, including an A-stage catalyst, a B-stage catalyst and a C-stage catalyst sequentially arranged from the gas inlet end to the gas outlet end. By adopting a specific distribution of V content in each stage of the catalyst (based on the mass of each stage of the catalyst, the arrangement order of the mass percentage content of V element in the corresponding three-stage catalysts is B-stage catalyst < A-stage catalyst < C-stage catalyst), a new three-stage bed catalyst is obtained. This catalyst has high activity and overall utilization efficiency of the catalyst. The method for gas-phase oxidation of pseudocumene to pyromellitic dianhydride using this catalyst not only has a high pyromellitic dianhydride yield, but also has a high load. The catalyst for oxidizing pseudocumene to pyromellitic anhydride provided by the present invention is a three-stage catalyst. By balancing the reaction heat release, the overall selectivity of the catalyst is improved. When evaluated on a 2000 ml bed layer using this catalyst, the molten salt temperature is 342 °C, and the pseudocumene concentration is 63.3 g / Nm 3 , and the mass yield of pyromellitic anhydride can reach 103.9%.

[0055] The reason why the catalyst of the present invention has the above advantages is that through research, the inventor of the present invention believes that the reason may be:

[0056] The three-stage catalyst of the present invention adopts the above specific V content arrangement, and preferably adopts the specific component content in the present invention, so that the catalyst has high activity at the inlet section. At the same time, the bed temperature distribution of the catalyst in the application is more uniform. It is speculated that the catalyst design of the present invention reduces the concentrated heat release during the catalytic reaction process, reduces the degree of peroxidation of the reactants, and improves the overall utilization efficiency of the bed layer while ensuring the activation speed. Detailed implementation mode

[0057] The present invention will be described in detail below with reference to specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art to the present invention based on the contents of the present invention still fall within the scope of protection of the present invention.

[0058] All raw materials used in the examples are commercially available. In the following examples and comparative examples, the term "balance TiO2" in the composition of a catalyst section refers to the balance of catalytically active substances in that section of the catalyst, i.e., the difference between the total content of catalytically active substances (100%) and the sum of the listed catalytically active substances.

[0059] In the following examples, the composition of the gas was analyzed by chemical titration.

[0060] The calculation method of the average anhydride yield is: average anhydride yield = average anhydride production / durene consumption × 100%; the above production and consumption are both measured in mol.

[0061] The molten salt temperature was measured by a thermocouple.

[0062] The mass content of each active substance in the following examples and comparative examples is calculated based on the feed amount.

[0063] Example 1

[0064] Preparation of catalyst in stage A:

[0065] Step A: Prepare a solution of 50.22 g ammonium metavanadate, 130.64 g oxalic acid, 2.86 g cesium sulfate, and 220 ml formamide in 350 g water. The mass ratio of formamide to water is 0.7:1.

[0066] Step B: The solution obtained in Step A was mixed with 630 g of titanium dioxide, 4.31 g of niobium oxalate, and 14.55 g of antimony trioxide and placed in a ball mill. 70 g of vinyl acetate / ethylene copolymer emulsion was added and ball milled for 4 hours to emulsify the catalytically active components into a uniform suspension emulsion. The emulsion viscosity was controlled to 12 Pa·s.

[0067] Step C: Place 2000 grams of a talc ring carrier with an outer diameter of 8 mm, a height of 6 mm, and a wall thickness of 1.5 mm in a rotating drum at a speed of 10 rpm; add the prepared emulsion to the stirring tank of the liquid spraying system and stir; start the hot air blower to allow hot air to enter the drum to preheat the carrier ring. When the carrier temperature reaches 130°C, open the feed nozzle, control the hot air temperature to 100°C, and spray the liquid at a rate of 30 ml / min; spray the catalytically active material emulsion onto the surface of the carrier talc ring through the nozzle and rapidly dry it with the hot air. Spraying is complete until the catalytically active material content reaches 13.5% of the carrier weight, and the Stage A catalyst is prepared. Based on the total weight content of active material in this stage catalyst being 100%, its composition is as follows:

[0068] V2O5: 5.68%

[0069] P2O5: 0%

[0070] Cs2O: 0.32%

[0071] Nb: 0.16%

[0072] Zr: 0%

[0073] Sb: 2.12%

[0074] The balance of the catalytically active material is TiO2.

[0075] Preparation of catalyst in stage B:

[0076] Step A: Prepare a solution of 39.74 g ammonium metavanadate, 123.26 g oxalic acid, 4.21 g cesium sulfate, and 220 ml formamide in 350 g water. The mass ratio of formamide to water is 0.7:1.

[0077] Step B: The solution obtained in Step A was mixed with 630 g of titanium dioxide, 5.05 g of niobium oxalate, and 12.21 g of antimony trioxide and placed in a ball mill. 70 g of vinyl acetate / ethylene copolymer emulsion was added and ball milled for 4 hours to emulsify the catalytically active components into a uniform suspension emulsion. The emulsion viscosity was controlled to 12 Pa·s.

[0078] Step C: Place 2000 grams of talc rings (8 mm outer diameter, 6 mm height, 1.5 mm wall thickness) in a rotating drum at a speed of 10 rpm. Add the prepared emulsion to the stirring tank of the liquid spraying system and stir. Turn on the hot air blower to allow hot air to enter the drum to preheat the carrier rings. When the carrier temperature reaches 130°C, open the feed nozzle, control the hot air temperature to 100°C, and spray the liquid at a rate of 30 ml / min. Spray the catalytically active material emulsion onto the surface of the carrier talc rings through the nozzle and rapidly dry them with the hot air. When the catalytically active material content reaches 13.6% of the carrier weight, spraying is complete, and the Stage B catalyst is prepared. Based on the total weight of the active material in this stage catalyst being 100%, its composition is as follows:

[0079] V2O5: 4.56%

[0080] P2O5: 0%

[0081] Cs2O: 0.48%

[0082] Nb: 0.18%

[0083] Zr: 0%

[0084] Sb: 1.8%

[0085] The balance is TiO2.

[0086] Preparation of catalyst in stage C:

[0087] Step A: Prepare a solution by adding 59.75 g of ammonium metavanadate, 138.82 g of oxalic acid, 2.04 g of cesium sulfate, 3.88 g of ammonium dihydrogen phosphate, and 220 ml of formamide to 350 g of water. The mass ratio of formamide to water is 0.7:1.

[0088] Step B: The solution, 630 g of titanium dioxide, 16.81 g of antimony trioxide, 3.59 g of niobium oxalate, and 3.48 g of zirconium sulfate tetrahydrate were poured into a ball mill. 100 g of vinyl acetate / ethylene copolymer emulsion was added and ball milled for 4 hours to emulsify the catalytically active components into a uniform suspension emulsion. The emulsion viscosity was controlled to 12 Pa·s.

[0089] Step C: Place 2000 grams of talc rings (8 mm outer diameter, 6 mm height, 1.5 mm wall thickness) in a rotating drum at a speed of 10 rpm. Add the prepared emulsion to the stirring tank of the liquid spraying system and stir. Turn on the hot air blower to allow hot air to enter the drum to preheat the carrier rings. When the carrier temperature reaches 110°C, turn on the feed nozzle and control the hot air temperature to 110°C. The liquid spraying rate is 60 ml / min. Spray the catalytically active material emulsion onto the surface of the carrier talc rings through the nozzle and rapidly dry them with the hot air. Spraying is complete until the catalytically active material content reaches 16.2% of the carrier weight. The catalyst in Stage C is prepared. Based on the total weight of the active material in this stage catalyst as 100%, its composition is as follows:

[0090] V2O5: 6.64%

[0091] P2O5: 0.34%

[0092] Cs2O: 0.23%

[0093] Nb: 0.13%

[0094] Zr: 0.22%

[0095] Sb: 2.4%

[0096] The balance is TiO2.

[0097] Catalyst performance was assessed using a single-tube reactor simulating industrial production conditions. The fixed-bed single-tube reactor had an inner diameter of 29 mm and a tube length of 4400 mm. Molten salt circulation was used to transfer heat externally, and a multi-point temperature measurement system was installed within the reactor tube. The homogeneous anhydride catalysts A, B, and C were loaded from top to bottom, with a catalyst loading height of 3100 mm. Catalyst A was loaded at a height of 1200 mm, Catalyst B at a height of 1100 mm, and Catalyst C at a height of 800 mm, resulting in a three-stage bed catalyst.

[0098] Example 2

[0099] Preparation of catalyst in stage A:

[0100] Step A: Prepare a solution of 50.22 g ammonium metavanadate, 130.64 g oxalic acid, 2.86 g cesium sulfate, and 220 ml formamide in 350 g water. The mass ratio of formamide to water is 0.7:1.

[0101] Step B: The solution obtained in Step A was mixed with 630 g of titanium dioxide, 4.31 g of niobium oxalate, and 14.55 g of antimony trioxide and placed in a ball mill. 70 g of vinyl acetate / ethylene copolymer emulsion was added and ball milled for 4 hours to emulsify the catalytically active components into a uniform suspension emulsion. The emulsion viscosity was controlled to 12 Pa·s.

[0102] Step C: Place 2000 grams of talc rings (8 mm outer diameter, 6 mm height, 1.5 mm wall thickness) in a rotating drum at a speed of 10 rpm. Add the prepared emulsion to the stirring tank of the liquid spraying system and stir. Turn on the hot air blower to allow hot air to enter the drum to preheat the carrier rings. When the carrier temperature reaches 130°C, open the feed nozzle, control the hot air temperature to 100°C, and spray the liquid at a rate of 30 ml / min. Spray the catalytically active substance emulsion onto the surface of the carrier talc rings through the nozzle and rapidly dry them with the hot air. When the catalytically active substance content reaches 14.2% of the carrier weight, spraying is complete, and the Stage A catalyst is prepared. Based on the total weight of the active substance in this stage catalyst being 100%, its composition is as follows:

[0103] V2O5: 5.68%

[0104] P2O5: 0%

[0105] Cs2O: 0.32%

[0106] Nb: 0.16%

[0107] Zr: 0%

[0108] Sb: 2.12%

[0109] The balance is TiO2.

[0110] Preparation of catalyst in stage B:

[0111] Step A: Prepare a solution of 47.85 g ammonium metavanadate, 113.37 g oxalic acid, 5.33 g cesium sulfate, and 220 ml formamide in 350 g water. The mass ratio of formamide to water is 0.7:1.

[0112] Step B: The solution obtained in Step A was mixed with 630 g of titanium dioxide, 6.52 g of niobium oxalate, and 13.78 g of antimony trioxide and placed in a ball mill. 70 g of vinyl acetate / ethylene copolymer emulsion was added and ball milled for 4 hours to emulsify the catalytically active components into a uniform suspension emulsion. The emulsion viscosity was controlled to 12 Pa·s.

[0113] Step C: Place 2000 grams of talc rings (8 mm outer diameter, 6 mm height, 1.5 mm wall thickness) in a rotating drum at a speed of 10 rpm. Add the prepared emulsion to the stirring tank of the liquid spraying system and stir. Turn on the hot air blower to allow hot air to enter the drum to preheat the carrier rings. When the carrier temperature reaches 130°C, open the feed nozzle, control the hot air temperature to 100°C, and spray the liquid at a rate of 30 ml / min. Spray the catalytically active material emulsion onto the surface of the carrier talc rings through the nozzle and rapidly dry them with the hot air. When the catalytically active material content reaches 13.7% of the carrier weight, spraying is complete, and the Stage B catalyst is prepared. Based on the total weight of the active material in this stage catalyst being 100%, its composition is as follows:

[0114] V2O5: 5.42%

[0115] P2O5: 0%

[0116] Cs2O: 0.6%

[0117] Nb: 0.23%

[0118] Zr: 0%

[0119] Sb: 2%

[0120] The balance is TiO2.

[0121] Preparation of catalyst in stage C:

[0122] Step A: Prepare a solution by adding 59.75 g of ammonium metavanadate, 138.82 g of oxalic acid, 2.04 g of cesium sulfate, 3.88 g of ammonium dihydrogen phosphate, and 220 ml of formamide to 350 g of water. The mass ratio of formamide to water is 0.7:1.

[0123] Step B: The solution, 630 g of titanium dioxide, 16.81 g of antimony trioxide, 3.59 g of niobium oxalate, and 3.48 g of zirconium sulfate tetrahydrate were poured into a ball mill. 100 g of vinyl acetate / ethylene copolymer emulsion was added and ball milled for 4 hours to emulsify the catalytically active components into a uniform suspension emulsion. The emulsion viscosity was controlled to 12 Pa·s.

[0124] Step C: Place 2000 grams of talc rings (8mm outer diameter, 6mm height, 1.5mm wall thickness) in a rotating drum at a speed of 10 rpm. Add the prepared emulsion to the stirring tank of the liquid spraying system and stir. Turn on the hot air blower to allow hot air to enter the drum to preheat the carrier rings. When the carrier temperature reaches 110°C, turn on the feed nozzle and control the hot air temperature to 110°C. The liquid spraying rate is 60 ml / min. Spray the catalytically active material emulsion onto the surface of the carrier talc rings through the nozzle and rapidly dry them with the hot air. When the catalytically active material content reaches 15.9% of the carrier weight, spraying is complete, and the Stage C catalyst is prepared. Based on the total weight content of active material in this stage catalyst being 100%, its composition is as follows:

[0125] V2O5: 6.64%

[0126] P2O5: 0.34%

[0127] Cs2O: 0.23%

[0128] Nb: 0.13%

[0129] Zr: 0.22%

[0130] Sb: 2.4%

[0131] The balance is TiO2.

[0132] The stage A catalyst, stage B catalyst and stage C catalyst were loaded according to the method of Example 1 to obtain a three-stage bed catalyst.

[0133] Example 3

[0134] Preparation of catalyst in stage A:

[0135] Step A: Prepare a solution of 57.61 g ammonium metavanadate, 138.37 g oxalic acid, 3.42 g cesium sulfate, and 220 ml formamide in 350 g water. The mass ratio of formamide to water is 0.7:1.

[0136] Step B: The solution obtained in Step A was mixed with 630 g of titanium dioxide, 4.69 g of niobium oxalate, and 15.46 g of antimony trioxide and placed in a ball mill. 70 g of vinyl acetate / ethylene copolymer emulsion was added and ball milled for 4 hours to emulsify the catalytically active components into a uniform suspension emulsion. The emulsion viscosity was controlled to 12 Pa·s.

[0137] Step C: Place 2000 grams of talc rings (8 mm outer diameter, 6 mm height, 1.5 mm wall thickness) in a rotating drum at a speed of 10 rpm. Add the prepared emulsion to the stirring tank of the liquid spraying system and stir. Turn on the hot air blower to allow hot air to enter the drum to preheat the carrier rings. When the carrier temperature reaches 130°C, open the feed nozzle, control the hot air temperature to 100°C, and spray the liquid at a rate of 30 ml / min. Spray the catalytically active substance emulsion onto the surface of the carrier talc rings through the nozzle and rapidly dry them with the hot air. When the catalytically active substance content reaches 14.4% of the carrier weight, spraying is complete, and the Stage A catalyst is prepared. Based on the total weight of the active substance in this stage catalyst being 100%, its composition is as follows:

[0138] V2O5: 6.45%

[0139] P2O5: 0%

[0140] Cs2O: 0.38%

[0141] Nb: 0.17%

[0142] Zr: 0%

[0143] Sb: 2.23%

[0144] The balance is TiO2.

[0145] Preparation of catalyst in stage B:

[0146] Step A: Prepare a solution of 47.85 g ammonium metavanadate, 113.37 g oxalic acid, 5.33 g cesium sulfate, and 220 ml formamide in 350 g water. The mass ratio of formamide to water is 0.7:1.

[0147] Step B: The solution obtained in Step A was mixed with 630 g of titanium dioxide, 6.52 g of niobium oxalate, and 13.78 g of antimony trioxide and placed in a ball mill. 70 g of vinyl acetate / ethylene copolymer emulsion was added and ball milled for 4 hours to emulsify the catalytically active components into a uniform suspension emulsion. The emulsion viscosity was controlled to 12 Pa·s.

[0148] Step C: Place 2000 grams of talc rings (8 mm outer diameter, 6 mm height, 1.5 mm wall thickness) in a rotating drum at a speed of 10 rpm. Add the prepared emulsion to the stirring tank of the liquid spraying system and stir. Turn on the hot air blower to allow hot air to enter the drum to preheat the carrier rings. When the carrier temperature reaches 130°C, open the feed nozzle, control the hot air temperature to 100°C, and spray the liquid at a rate of 30 ml / min. Spray the catalytically active material emulsion onto the surface of the carrier talc rings through the nozzle and rapidly dry them with the hot air. When the catalytically active material content reaches 13.4% of the carrier weight, spraying is complete, and the Stage B catalyst is prepared. Based on the total weight of the active material in this stage catalyst being 100%, its composition is as follows:

[0149] V2O5: 5.42%

[0150] P2O5: 0%

[0151] Cs2O: 0.6%

[0152] Nb: 0.23%

[0153] Zr: 0%

[0154] Sb: 2%

[0155] The balance is TiO2.

[0156] Stage C catalyst preparation:

[0157] Step A: Prepare a solution by adding 59.75 g of ammonium metavanadate, 138.82 g of oxalic acid, 2.04 g of cesium sulfate, 3.88 g of ammonium dihydrogen phosphate, and 220 ml of formamide to 350 g of water. The mass ratio of formamide to water is 0.7:1.

[0158] Step B: The solution, 630 g of titanium dioxide, 16.81 g of antimony trioxide, 3.59 g of niobium oxalate, and 3.48 g of zirconium sulfate tetrahydrate were poured into a ball mill. 100 g of vinyl acetate / ethylene copolymer emulsion was added and ball milled for 4 hours to emulsify the catalytically active components into a uniform suspension emulsion. The emulsion viscosity was controlled to 12 Pa·s.

[0159] Step C: Place 2000 grams of talc rings (8mm outer diameter, 6mm height, 1.5mm wall thickness) in a rotating drum at a speed of 10 rpm; add the prepared emulsion to the stirring tank of the liquid spraying system and stir; start the hot air blower to allow hot air to enter the drum to preheat the carrier rings. When the carrier temperature reaches 110°C, open the feed nozzle and control the hot air temperature to 110°C. The liquid spraying rate is 60 ml / min; spray the catalytically active material emulsion onto the surface of the carrier talc rings through the nozzle and rapidly dry them with the hot air. When the catalytically active material content reaches 15.7% of the carrier weight, spraying is complete, and the Stage C catalyst is prepared. Based on the total weight content of active material in this stage catalyst as 100%, its composition is as follows:

[0160] V2O5: 6.64%

[0161] P2O5: 0.34%

[0162] Cs2O: 0.23%

[0163] Nb: 0.13%

[0164] Zr: 0.22%

[0165] Sb: 2.4%

[0166] The balance is TiO2.

[0167] The stage A catalyst, stage B catalyst and stage C catalyst were loaded according to the method of Example 1 to obtain a three-stage bed catalyst.

[0168] Example 4

[0169] Preparation of catalyst in stage A:

[0170] Step A: Prepare a solution of 57.61 g ammonium metavanadate, 138.37 g oxalic acid, 3.42 g cesium sulfate, and 220 ml formamide in 350 g water. The mass ratio of formamide to water is 0.7:1.

[0171] Step B: The solution obtained in Step A was mixed with 630 g of titanium dioxide, 4.69 g of niobium oxalate, and 15.46 g of antimony trioxide and placed in a ball mill. 70 g of vinyl acetate / ethylene copolymer emulsion was added and ball milled for 4 hours to emulsify the catalytically active components into a uniform suspension emulsion. The emulsion viscosity was controlled to 12 Pa·s.

[0172] Step C: Place 2000 grams of talc rings (8 mm outer diameter, 6 mm height, 1.5 mm wall thickness) in a rotating drum at a speed of 10 rpm. Add the prepared emulsion to the stirring tank of the liquid spraying system and stir. Turn on the hot air blower to allow hot air to enter the drum to preheat the carrier rings. When the carrier temperature reaches 130°C, open the feed nozzle, control the hot air temperature to 100°C, and spray the liquid at a rate of 30 ml / min. Spray the catalytically active substance emulsion onto the surface of the carrier talc rings through the nozzle and rapidly dry them with the hot air. When the catalytically active substance content reaches 14.2% of the carrier weight, spraying is complete, and the Stage A catalyst is prepared. Based on the total weight of the active substance in this stage catalyst being 100%, its composition is as follows:

[0173] V2O5: 6.45%

[0174] P2O5: 0%

[0175] Cs2O: 0.38%

[0176] Nb: 0.17%

[0177] Zr: 0%

[0178] Sb: 2.23%

[0179] The balance is TiO2.

[0180] Preparation of catalyst in stage B:

[0181] Step A: Prepare a solution of 47.85 g ammonium metavanadate, 113.37 g oxalic acid, 5.33 g cesium sulfate, and 220 ml formamide in 350 g water. The mass ratio of formamide to water is 0.7:1.

[0182] Step B: The solution obtained in Step A was mixed with 630 g of titanium dioxide, 6.52 g of niobium oxalate, and 13.78 g of antimony trioxide and placed in a ball mill. 70 g of vinyl acetate / ethylene copolymer emulsion was added and ball milled for 4 hours to emulsify the catalytically active components into a uniform suspension emulsion. The emulsion viscosity was controlled to 12 Pa·s.

[0183] Step C: Place 2000 grams of talc rings (8 mm outer diameter, 6 mm height, 1.5 mm wall thickness) in a rotating drum at a speed of 10 rpm. Add the prepared emulsion to the stirring tank of the liquid spraying system and stir. Turn on the hot air blower to allow hot air to enter the drum to preheat the carrier rings. When the carrier temperature reaches 130°C, open the feed nozzle, control the hot air temperature to 100°C, and spray the liquid at a rate of 30 ml / min. Spray the catalytically active material emulsion onto the surface of the carrier talc rings through the nozzle and rapidly dry them with the hot air. When the catalytically active material content reaches 13.5% of the carrier weight, spraying is complete, and the Stage B catalyst is prepared. Based on the total weight of the active material in this stage catalyst being 100%, its composition is as follows:

[0184] V2O5: 5.42%

[0185] P2O5: 0%

[0186] Cs2O: 0.6%

[0187] Nb: 0.23%

[0188] Zr: 0%

[0189] Sb: 2%

[0190] The balance is TiO2.

[0191] Stage C catalyst preparation:

[0192] Step A: Prepare a solution by adding 67.25 g of ammonium metavanadate, 159.31 g of oxalic acid, 2.26 g of cesium sulfate, 4.26 g of ammonium dihydrogen phosphate, and 220 ml of formamide to 350 g of water. The mass ratio of formamide to water is 0.7:1.

[0193] Step B: The solution, 630 g of titanium dioxide, 18.33 g of antimony trioxide, 3.94 g of niobium oxalate, and 3.85 g of zirconium sulfate tetrahydrate were poured into a ball mill. 100 g of vinyl acetate / ethylene copolymer emulsion was added and ball milled for 4 hours to emulsify the catalytically active components into a uniform suspension emulsion. The emulsion viscosity was controlled to 12 Pa·s.

[0194] Step C: Place 2000 grams of talc rings (8 mm outer diameter, 6 mm height, 1.5 mm wall thickness) in a rotating drum at a speed of 10 rpm; add the prepared emulsion to the stirring tank of the liquid spraying system and stir; start the hot air blower to allow hot air to enter the drum to preheat the carrier rings. When the carrier temperature reaches 110°C, open the feed nozzle and control the hot air temperature to 110°C. The liquid spraying rate is 60 ml / min; spray the catalytically active material emulsion onto the surface of the carrier talc rings through the nozzle and rapidly dry them with the hot air. When the catalytically active material content reaches 15.8% of the carrier weight, spraying is complete, and the Stage C catalyst is prepared. Based on the total weight content of active material in this stage catalyst being 100%, its composition is as follows:

[0195] V2O5: 7.39%

[0196] P2O5: 0.37%

[0197] Cs2O: 0.25%

[0198] Nb: 0.14%

[0199] Zr: 0.24%

[0200] Sb: 2.59%

[0201] The balance is TiO2.

[0202] The stage A catalyst, stage B catalyst and stage C catalyst were loaded according to the method of Example 1 to obtain a three-stage bed catalyst.

[0203] Example 5

[0204] Preparation of catalyst in stage A:

[0205] Step A: Prepare a solution of 57.61 g ammonium metavanadate, 138.37 g oxalic acid, 3.42 g cesium sulfate, and 220 ml formamide in 350 g water. The mass ratio of formamide to water is 0.7:1.

[0206] Step B: The solution obtained in Step A was mixed with 630 g of titanium dioxide, 4.69 g of niobium oxalate, and 15.46 g of antimony trioxide and placed in a ball mill. 70 g of vinyl acetate / ethylene copolymer emulsion was added and ball milled for 4 hours to emulsify the catalytically active components into a uniform suspension emulsion. The emulsion viscosity was controlled to 12 Pa·s.

[0207] Step C: Place 2000 grams of talc rings (8 mm outer diameter, 6 mm height, 1.5 mm wall thickness) in a rotating drum at a speed of 10 rpm. Add the prepared emulsion to the stirring tank of the liquid spraying system and stir. Turn on the hot air blower to allow hot air to enter the drum to preheat the carrier rings. When the carrier temperature reaches 130°C, open the feed nozzle, control the hot air temperature to 100°C, and spray the liquid at a rate of 30 ml / min. Spray the catalytically active substance emulsion onto the surface of the carrier talc rings through the nozzle and rapidly dry them with the hot air. When the catalytically active substance content reaches 14.9% of the carrier weight, spraying is complete, and the Stage A catalyst is prepared. Based on the total weight content of active substance in this stage catalyst being 100%, its composition is as follows:

[0208] V2O5: 6.45%

[0209] P2O5: 0%

[0210] Cs2O: 0.38%

[0211] Nb: 0.17%

[0212] Zr: 0%

[0213] Sb: 2.23%

[0214] The balance is TiO2.

[0215] Preparation of catalyst in stage B:

[0216] Step A: Prepare a solution of 39.74 g ammonium metavanadate, 123.26 g oxalic acid, 4.21 g cesium sulfate, and 220 ml formamide in 350 g water. The mass ratio of formamide to water is 0.7:1.

[0217] Step B: The solution obtained in Step A was mixed with 630 g of titanium dioxide, 5.05 g of niobium oxalate, and 12.21 g of antimony trioxide and placed in a ball mill. 70 g of vinyl acetate / ethylene copolymer emulsion was added and ball milled for 4 hours to emulsify the catalytically active components into a uniform suspension emulsion. The emulsion viscosity was controlled to 12 Pa·s.

[0218] Step C: Place 2000 grams of talc rings (8 mm outer diameter, 6 mm height, 1.5 mm wall thickness) in a rotating drum at a speed of 10 rpm. Add the prepared emulsion to the stirring tank of the liquid spraying system and stir. Turn on the hot air blower to allow hot air to enter the drum to preheat the carrier rings. When the carrier temperature reaches 130°C, open the feed nozzle, control the hot air temperature to 100°C, and spray the liquid at a rate of 30 ml / min. Spray the catalytically active material emulsion onto the surface of the carrier talc rings through the nozzle and rapidly dry them with the hot air. When the catalytically active material content reaches 14.2% of the carrier weight, spraying is complete, and the Stage B catalyst is prepared. Based on the total weight of the active material in this stage catalyst being 100%, its composition is as follows:

[0219] V2O5: 4.56%

[0220] P2O5: 0%

[0221] Cs2O: 0.48%

[0222] Nb: 0.18%

[0223] Zr: 0%

[0224] Sb: 1.8%

[0225] The balance is TiO2.

[0226] Preparation of catalyst in stage C:

[0227] Step A: Prepare a solution by adding 59.75 g of ammonium metavanadate, 138.82 g of oxalic acid, 2.04 g of cesium sulfate, 3.88 g of ammonium dihydrogen phosphate, and 220 ml of formamide to 350 g of water. The mass ratio of formamide to water is 0.7:1.

[0228] Step B: The solution, 630 g of titanium dioxide, 16.81 g of antimony trioxide, 3.59 g of niobium oxalate, and 3.48 g of zirconium sulfate tetrahydrate were poured into a ball mill. 100 g of vinyl acetate / ethylene copolymer emulsion was added and ball milled for 4 hours to emulsify the catalytically active components into a uniform suspension emulsion. The emulsion viscosity was controlled to 12 Pa·s.

[0229] Step C: Place 2000 grams of talc rings (8 mm outer diameter, 6 mm height, 1.5 mm wall thickness) in a rotating drum at a speed of 10 rpm. Add the prepared emulsion to the stirring tank of the liquid spraying system and stir. Turn on the hot air blower to allow hot air to enter the drum to preheat the carrier rings. When the carrier temperature reaches 110°C, turn on the feed nozzle and control the hot air temperature to 110°C. The liquid spraying rate is 60 ml / min. Spray the catalytically active material emulsion onto the surface of the carrier talc rings through the nozzle and rapidly dry them with the hot air. Spraying is complete until the catalytically active material content reaches 15.6% of the carrier weight. The catalyst in Stage C is prepared. Based on the total weight of the active material in this stage catalyst as 100%, its composition is as follows:

[0230] V2O5: 6.64%

[0231] P2O5: 0.34%

[0232] Cs2O: 0.23%

[0233] Nb: 0.13%

[0234] Zr: 0.22%

[0235] Sb: 2.4%

[0236] The balance is TiO2.

[0237] The stage A catalyst, stage B catalyst and stage C catalyst were loaded according to the method of Example 1 to obtain a three-stage bed catalyst.

[0238] Example 6

[0239] Preparation of catalyst in stage A:

[0240] Step A: Prepare a solution of 45.32 g ammonium metavanadate, 117.23 g oxalic acid, 2.57 g cesium sulfate, and 220 ml formamide in 350 g water. The mass ratio of formamide to water is 0.7:1.

[0241] Step B: The solution obtained in Step A was mixed with 630 g of titanium dioxide, 3.91 g of niobium oxalate, and 13.12 g of antimony trioxide and placed in a ball mill. 70 g of vinyl acetate / ethylene copolymer emulsion was added and ball milled for 4 hours to emulsify the catalytically active components into a uniform suspension emulsion. The emulsion viscosity was controlled to 12 Pa·s.

[0242] Step C: Place 2000 grams of a talc ring carrier with an outer diameter of 8 mm, a height of 6 mm, and a wall thickness of 1.5 mm in a rotating drum at a speed of 10 rpm; add the prepared emulsion to the stirring tank of the liquid spraying system and stir; start the hot air blower to allow hot air to enter the drum to preheat the carrier ring. When the carrier temperature reaches 130°C, open the feed nozzle, control the hot air temperature to 100°C, and spray the liquid at a rate of 30 ml / min; spray the catalytically active material emulsion onto the surface of the carrier talc ring through the nozzle and rapidly dry it with the hot air. When the catalytically active material content reaches 13.8% of the carrier weight, spraying is complete, and the Stage A catalyst is prepared. Based on the total weight content of active material in this stage catalyst as 100%, its composition is as follows:

[0243] V2O5: 5.17%

[0244] P2O5: 0%

[0245] Cs2O: 0.29%

[0246] Nb: 0.14%

[0247] Zr: 0%

[0248] Sb: 1.93%

[0249] The balance of the catalytically active material is TiO2.

[0250] Preparation of catalyst in stage B:

[0251] Step A: Prepare a solution of 36.34 g ammonium metavanadate, 113.26 g oxalic acid, 3.92 g cesium sulfate, and 220 ml formamide in 350 g water. The mass ratio of formamide to water is 0.7:1.

[0252] Step B: The solution obtained in Step A was mixed with 630 g of titanium dioxide, 4.62 g of niobium oxalate, and 11.23 g of antimony trioxide and placed in a ball mill. 70 g of vinyl acetate / ethylene copolymer emulsion was added and ball milled for 4 hours to emulsify the catalytically active components into a uniform suspension emulsion. The emulsion viscosity was controlled to 12 Pa·s.

[0253] Step C: Place 2000 grams of talc rings (8 mm outer diameter, 6 mm height, 1.5 mm wall thickness) in a rotating drum at a speed of 10 rpm. Add the prepared emulsion to the stirring tank of the liquid spraying system and stir. Turn on the hot air blower to allow hot air to enter the drum to preheat the carrier rings. When the carrier temperature reaches 130°C, open the feed nozzle, control the hot air temperature to 100°C, and spray the liquid at a rate of 30 ml / min. Spray the catalytically active material emulsion onto the surface of the carrier talc rings through the nozzle and rapidly dry them with the hot air. When the catalytically active material content reaches 14.2% of the carrier weight, spraying is complete, and the Stage B catalyst is prepared. Based on the total weight of the active material in this stage catalyst being 100%, its composition is as follows:

[0254] V2O5: 4.19%

[0255] P2O5: 0%

[0256] Cs2O: 0.45%

[0257] Nb: 0.17%

[0258] Zr: 0%

[0259] Sb: 1.67%

[0260] The balance is TiO2.

[0261] Preparation of catalyst in stage C:

[0262] Step A: Prepare a solution by adding 53.97 g of ammonium metavanadate, 124.36 g of oxalic acid, 1.85 g of cesium sulfate, 3.52 g of ammonium dihydrogen phosphate, and 220 ml of formamide to 350 g of water. The mass ratio of formamide to water is 0.7:1.

[0263] Step B: The solution, 630 g of titanium dioxide, 14.26 g of antimony trioxide, 3.26 g of niobium oxalate, and 3.17 g of zirconium sulfate tetrahydrate were poured into a ball mill. 100 g of vinyl acetate / ethylene copolymer emulsion was added and ball milled for 4 hours to emulsify the catalytically active components into a uniform suspension emulsion. The emulsion viscosity was controlled to 12 Pa·s.

[0264] Step C: Place 2000 grams of talc rings (8 mm outer diameter, 6 mm height, 1.5 mm wall thickness) in a rotating drum at a speed of 10 rpm; add the prepared emulsion to the stirring tank of the liquid spraying system and stir; start the hot air blower to allow hot air to enter the drum to preheat the carrier rings. When the carrier temperature reaches 110°C, open the feed nozzle and control the hot air temperature to 110°C. The liquid spraying rate is 60 ml / min; spray the catalytically active material emulsion onto the surface of the carrier talc rings through the nozzle and rapidly dry them with the hot air. When the catalytically active material content reaches 15.8% of the carrier weight, spraying is complete, and the Stage C catalyst is prepared. Based on the total weight content of active material in this stage catalyst being 100%, its composition is as follows:

[0265] V2O5: 6.64%

[0266] P2O5: 0.34%

[0267] Cs2O: 0.23%

[0268] Nb: 0.13%

[0269] Zr: 0.22%

[0270] Sb: 2.4%

[0271] The balance is TiO2.

[0272] The stage A catalyst, stage B catalyst and stage C catalyst were loaded according to the method of Example 1 to obtain a three-stage bed catalyst.

[0273] Comparative Example 1

[0274] Catalyst preparation:

[0275] Step A: Prepare a solution of 57.61 g ammonium metavanadate, 138.37 g oxalic acid, 3.42 g cesium sulfate, and 220 ml formamide in 350 g water. The mass ratio of formamide to water is 0.7:1.

[0276] Step B: The solution obtained in Step A was mixed with 630 g of titanium dioxide, 4.69 g of niobium oxalate, and 15.46 g of antimony trioxide and placed in a ball mill. 70 g of vinyl acetate / ethylene copolymer emulsion was added and ball milled for 4 hours to emulsify the catalytically active components into a uniform suspension emulsion. The emulsion viscosity was controlled to 12 Pa·s.

[0277] Step C: Place 2000 grams of talc rings (8 mm outer diameter, 6 mm height, 1.5 mm wall thickness) in a rotating drum at a speed of 10 rpm; add the prepared emulsion to a stirring tank in a liquid spraying system and stir; start a hot air blower to allow hot air to enter the drum to preheat the carrier rings. When the carrier temperature reaches 130°C, open the feed nozzle, control the hot air temperature to 100°C, and spray the liquid at a rate of 30 ml / min; spray the catalytically active substance emulsion onto the surface of the carrier talc rings through the nozzle and rapidly dry them with the hot air. When the catalytically active substance content reaches 14.7% of the carrier weight, spraying is complete to prepare a catalyst. Based on the total weight of the active substance in this catalyst as 100%, its composition is as follows:

[0278] V2O5: 6.45%

[0279] P2O5: 0%

[0280] Cs2O: 0.38%

[0281] Nb: 0.17%

[0282] Zr: 0%

[0283] Sb: 2.23%

[0284] The balance is TiO2.

[0285] The catalysts in stage A, stage B and stage C in Example 1 were replaced, except that all the catalysts in this comparative example were filled, with a total height of 3100 mm.

[0286] Comparative Example 2

[0287] Catalyst preparation:

[0288] Step A: Prepare a solution of 50.22 g ammonium metavanadate, 130.64 g oxalic acid, 2.86 g cesium sulfate, and 220 ml formamide in 350 g water. The mass ratio of formamide to water is 0.7:1.

[0289] Step B: The solution obtained in Step A was mixed with 630 g of titanium dioxide, 4.31 g of niobium oxalate, and 14.55 g of antimony trioxide and placed in a ball mill. 70 g of vinyl acetate / ethylene copolymer emulsion was added and ball milled for 4 hours to emulsify the catalytically active components into a uniform suspension emulsion. The emulsion viscosity was controlled to 12 Pa·s.

[0290] Step C: Place 2000 grams of talc rings (8 mm outer diameter, 6 mm height, 1.5 mm wall thickness) in a rotating drum at a speed of 10 rpm; add the prepared emulsion to a stirring tank in a liquid spraying system and stir; start a hot air blower to allow hot air to enter the drum to preheat the carrier rings. When the carrier temperature reaches 130°C, open the feed nozzle, control the hot air temperature to 100°C, and spray the liquid at a rate of 30 ml / min; spray the catalytically active substance emulsion onto the surface of the carrier talc rings through the nozzle and rapidly dry them with the hot air. The catalytically active substance content reaches 14.2% of the carrier weight, and the spraying is complete. The catalyst is prepared. Based on the total weight of the active substance in this catalyst as 100%, its composition is as follows:

[0291] V2O5: 5.68%

[0292] P2O5: 0%

[0293] Cs2O: 0.32%

[0294] Nb: 0.16%

[0295] Zr: 0%

[0296] Sb: 2.12%

[0297] The balance is TiO2.

[0298] The catalysts in stage A, stage B and stage C in Example 1 were replaced, except that all the catalysts in this comparative example were filled, with a total height of 3100 mm.

[0299] Comparative Example 3

[0300] The catalysts of each stage in Example 2 were used as raw materials. The difference was that the loading order was changed. The specific loading order and height were as follows: the homogeneous anhydride catalyst BAC was loaded from top to bottom, the catalyst loading height was 3100 mm, the B stage catalyst loading height was 1100 mm, the A stage catalyst loading height was 1200 mm, and the C stage catalyst loading height was 800 mm, to obtain a three-stage bed catalyst.

[0301] Comparative Example 4

[0302] The catalysts of each section in Example 2 were used as raw materials. The difference was that the loading order was changed. The specific loading order and height were as follows: the sections of the homogeneous anhydride catalyst CBA were loaded from top to bottom, the catalyst loading height was 3100 mm, the C section catalyst loading height was 800 mm, the B section catalyst loading height was 1100 mm, and the A section catalyst loading height was 1200 mm, to obtain a three-stage bed catalyst.

[0303] Comparative Example 5

[0304] The catalysts of each stage in Example 2 were used as raw materials, except that only the catalysts of stage A and stage C were used, and the order of loading was changed. The specific loading order and height were as follows:

[0305] The sections of homogeneous anhydride catalyst AC were loaded from top to bottom. The loading height of the catalyst in section A was 2300 mm, and the loading height of the catalyst in section C was 800 mm, to obtain a two-stage bed catalyst.

[0306] Application example: Catalyst evaluation

[0307] Catalyst performance was assessed using a single-tube reactor simulating industrial production conditions. The fixed-bed single-tube reactor had an inner diameter of 29 mm and a length of 4400 mm. Molten salt circulation was used for heat transfer outside the reactor tube, and a multi-point temperature measurement system was installed inside the tube. The catalyst was loaded according to the methods described in the Examples and Comparative Examples above. The reactor outlet was connected to an analysis system and a reactant collection system.

[0308] All the prepared catalysts were evaluated under the same conditions. The catalysts were activated in an oxidizing atmosphere for 24 hours. After adding the materials, the operating temperature of the salt bath was controlled at 350-390℃ and the air velocity was controlled at 4000h -1 -5000h -1 Within the range, the durene feed concentration was gradually increased at the same initial feed concentration, and sampling and analysis of each condition were carried out at the reactor outlet to evaluate the performance indicators of each catalyst, such as the maximum load, optimal yield and the corresponding minimum molten salt temperature at this time, as shown in Table 1.

[0309] The composition of the gas is analyzed by chemical titration.

[0310] The calculation method of the anhydride yield is: anhydride production / durene consumption × 100%

[0311] The following are the evaluation results of the catalyst evaluation experiments in the examples and comparative examples. See Table 1.

[0312] Table 1

[0313]

[0314]

[0315] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation of the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

[0316] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings conventionally understood by those skilled in the art. In the event of conflict, the definitions in this specification shall prevail.

[0317] When this specification uses the prefix "well known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, the objects introduced by the prefix include those commonly used in the art when this application is filed, but also include those that are not commonly used at present but will become generally recognized in the art to be suitable for similar purposes.

[0318] The endpoints and any values of the ranges disclosed in this application document 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 each range, the endpoint values of each range and a separate point value, and the separate point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be considered as specifically disclosed in this article.

[0319] In the context of this specification, any matters or items not mentioned are directly applicable to those known in the art without any changes except those explicitly stated.

[0320] Moreover, any embodiment described herein may be freely combined with one or more other embodiments described herein, and the technical solutions or technical ideas thus formed shall be deemed as part of the original disclosure or original record of the present invention, and shall not be regarded as new content that has not been disclosed or anticipated herein, unless a person skilled in the art considers that the combination is obviously unreasonable.

Claims

1. A catalyst, which is a three - bed catalyst, including A - section catalyst, B - section catalyst and C - section catalyst arranged in sequence from the gas inlet end to the gas outlet end. Each of the A - section catalyst, B - section catalyst and C - section catalyst includes a carrier and an active substance supported on the carrier. The active substance includes V, Cs, Ti, a promoter component and optionally P; The promoter component is selected from at least one of the metal elements in the fourth, fifth and sixth periods except V, Cs and Ti; in, Based on the mass content of the total amount of the active substance in each section of the catalyst, the arrangement order of the mass percentage content of V element in each section of the catalyst in the corresponding three - section catalyst is: B - section catalyst < A - section catalyst < C - section catalyst; Based on the mass content of the total amount of the active substance in each section of the catalyst being 100%, the mass content of V is calculated as V2O5; The content of V2O5 in the A - section catalyst is 5wt% - 7wt%; the content of V2O5 in the B - section catalyst is 4wt% - 6wt%; the content of V2O5 in the C - section catalyst is 6wt% - 8wt%.

2. The catalyst according to claim 1, characterized in that: The content of V2O5 in the A - section catalyst is 5.6wt% - 6.5wt%; the content of V2O5 in the B - section catalyst is 4.5wt% - 5.5wt%; the content of V2O5 in the C - section catalyst is 6.6wt% - 7.5wt%.

3. The catalyst according to claim 1 or 2, wherein: Based on the mass content of the carrier in each section of the catalyst being 100%, the loading amount of the active substance in each section of the catalyst is 12wt% - 17wt% respectively.

4. The catalyst according to claim 1 or 2, wherein: Based on the mass content of the carrier in each section of the catalyst being 100%, the loading amount of the active substance in each section of the catalyst is 13wt% - 16.5wt% respectively.

5. The catalyst according to claim 3, wherein: Based on the mass content of the total amount of the active substance in each section of the catalyst being 100%, each of the A - section catalyst, B - section catalyst and C - section catalyst contains: 0 - 0.5wt% of P2O5; 0.1wt% - 1wt% of Cs2O; 1wt% - 10wt% of the promoter component calculated as metal oxide.

6. The catalyst according to claim 3, wherein: Based on the mass content of the total amount of the active substance in each section of the catalyst being 100%, each of the A - section catalyst, B - section catalyst and C - section catalyst contains: 0 - 0.4wt% of P2O5; 0.22wt% - 0.61wt% of Cs2O; 1.8wt% - 2.8wt% of the promoter component calculated as metal oxide; The balance of the active substance is TiO2.

7. The catalyst according to claim 1, wherein: The promoter component is selected from at least one of rubidium, cerium, niobium, chromium, tungsten, silver, cobalt, gallium, indium, antimony, bismuth, zirconium and erbium elements; and / or, The carrier material is selected from at least one of talc rings, silicon carbide, silica, quartz and ceramics.

8. The catalyst according to claim 1, characterized in that: The promoter component is selected from at least one of niobium, antimony and zirconium.

9. The catalyst according to claim 1, characterized in that: The volume ratio of the stage A catalyst, the stage B catalyst and the stage C catalyst is 1:(0.8-1):(0.6-1).

10. The catalyst according to claim 1, characterized in that: Taking the total mass content of active substances in each stage catalyst as 100%, the stage A catalyst contains: 5.6wt%-6.5wt% V2O5; 0.3wt%-0.39wt% CsO2; 2.2 wt% to 2.4 wt% of a co-catalyst component; and / or, The B-stage catalyst contains: 4.5wt%-5.5wt% V2O5; 0.48wt%-0.61wt% CsO2; 1.9 wt% to 2.3 wt% of a co-catalyst component; and / or, The C-stage catalyst contains: 6.5wt%-7.5wt% V2O5; 0.34wt%-0.38wt% P2O5; 0.22wt%-0.25wt% CsO2; 2.7 wt%-3 wt% of a co-catalyst component.

11. The catalyst according to claim 10, characterized in that: The balance of active substances in the stage A catalyst, the stage B catalyst and the stage C catalyst is TiO2.

12. A method for preparing the catalyst according to any one of claims 1 to 11, comprising loading a vanadium compound, a cesium compound, a titanium compound, a compound containing a co-catalyst component, and an optional phosphorus compound on a carrier according to their respective compositions and ratios to obtain a stage A catalyst, a stage B catalyst, and a stage C catalyst, respectively; The stage A catalyst, stage B catalyst and stage C catalyst are sequentially loaded from the gas inlet end to the gas outlet end to obtain a three-stage bed catalyst.

13. The preparation method according to claim 12, characterized in that: The preparation methods of the stage A catalyst, stage B catalyst and stage C catalyst each include: Step A: adding oxalic acid, a vanadium compound, a cesium compound and an optional phosphorus compound into a solvent and dissolving them to prepare a solution; Step B: mixing the solution obtained in step A with titanium dioxide, a compound containing a co-catalyst component, and a binder to prepare a spray slurry; Step C: spraying the spray slurry onto a support material, followed by drying.

14. The preparation method according to claim 13, characterized in that: In step A, the solvent is a mixed solution of water and a water-soluble organic solvent; The water-soluble organic solvent is selected from at least one of methanol, ethanol, formamide and N,N-dimethylamide; The mass ratio of the water-soluble organic solvent to water is (0.1-1):

1.

15. The preparation method according to claim 14, characterized in that: In step A, the solvent is a mixed solution of water and a water-soluble organic solvent, and the water-soluble organic solvent is selected from at least one of methanol, ethanol, formamide and N,N-dimethylamide.

16. The preparation method according to claim 14, characterized in that: The mass ratio of the water-soluble organic solvent to water is (0.1-0.7):

1.

17. The preparation method according to claim 13, characterized in that: The vanadium compound is selected from ammonium metavanadate and / or vanadium pentoxide; and / or, The phosphorus compound is selected from at least one of diammonium phosphate, triammonium phosphate and phosphorus pentoxide; and / or, The cesium compound is selected from at least one of cesium nitrate, cesium sulfate and cesium chloride.

18. The preparation method according to claim 13, characterized in that: In the step A, The mass ratio of solvent to oxalic acid is 100:(15-25); The mass ratio of the solvent to the vanadium compound is 100:(7-11); The mass ratio of the solvent to the phosphorus compound is 100:(0-0.8); The mass ratio of the solvent to the cesium compound is 100:(0.1-1).

19. The preparation method according to claim 13, characterized in that: In the step A, The mass ratio of solvent to oxalic acid is 100:(18-24); The mass ratio of the solvent to the vanadium compound is 100:(6.5-10); The mass ratio of the solvent to the phosphorus compound is 100:(0.1-0.72); The mass ratio of the solvent to the cesium compound is 100:(0.3-0.9).

20. The preparation method according to claim 13, characterized in that: In step B, the titanium dioxide is anatase titanium dioxide with a specific surface area of 10m 2 / g-30m 2 / g; and / or, The adhesive is at least one of vinyl acetate acrylate copolymer, vinyl acetate ethylene copolymer, vinyl acetate maleate copolymer and acrylic acid maleic acid copolymer.

21. The preparation method according to claim 13, characterized in that: In step B, the titanium dioxide is anatase titanium dioxide with a specific surface area of 15m 2 / g-25m 2 / g.

22. The preparation method according to claim 13, wherein: In the step B, the viscosity of the spray slurry obtained is 10Pa·s-40Pa·s; and / or, The mass ratio of the solvent in step A to the titanium dioxide, the compound containing the co-catalyst component, and the binder in step B is 100:(100-110):(2-4.5):(13-25).

23. The preparation method according to claim 13, wherein: In step B, the viscosity of the spray slurry obtained is 12 Pa·s-25 Pa·s; and / or, The mass ratio of the solvent in step A to the titanium dioxide, the compound containing the co-catalyst component, and the binder in step B is 100:(103-107):(2.8-4.4):(13.5-22.5).

24. The preparation method according to claim 13, wherein: The temperature of the carrier is 80°C-130°C; and / or, The drying temperature is 100°C-120°C; and / or, The spraying rate is 30-60 ml / min.

25. A method for oxidizing durenyl to prepare pyromellitic anhydride, comprising contacting a mixed gas containing durenyl and air with the catalyst according to any one of claims 1 to 11 or the catalyst prepared by the preparation method according to any one of claims 12 to 24, and performing an oxidation reaction to obtain pyromellitic dianhydride.

26. The method for preparing homoanhydride by oxidizing durene according to claim 25, wherein: The reaction temperature is 300-450°C; and / or the air space velocity is 1500h -1 -5000h -1 ; and / or, the mass concentration of durene is 50-70g / m 3 .

27. The method for preparing homoanhydride by oxidizing durene according to claim 25, wherein: The reaction temperature is 330-400°C; and / or the air space velocity is 4000h -1 -5000h -1 ; and / or, the mass concentration of durene is 55-65g / m 3 .

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