CN116060062A

CN116060062A - Composite catalyst bed for preparing phthalic anhydride from o-xylene, preparation method of composite catalyst bed and method for preparing phthalic anhydride from o-xylene

Info

Publication number: CN116060062A
Application number: CN202111282767.4A
Authority: CN
Inventors: 刘玉芬; 安欣; 袁滨
Original assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Current assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Priority date: 2021-11-01
Filing date: 2021-11-01
Publication date: 2023-05-05

Abstract

The invention relates to the technical field of phthalic anhydride catalysts, in particular to a composite catalyst bed for preparing phthalic anhydride from o-xylene, a preparation method thereof and a method for preparing phthalic anhydride from o-xylene. Along the material flow direction, the composite catalyst bed comprises a catalyst E, a catalyst F, a catalyst G and a catalyst H, wherein the catalyst E, the catalyst F, the catalyst G and the catalyst H respectively and independently comprise a carrier and an active component loaded on the carrier; wherein the active ingredient contains V ₂ O ₅ Wherein the catalyst E and the catalyst F each independently contain a heat transfer medium, and the catalyst G and the catalyst H do not contain a heat transfer medium. The method for preparing phthalic anhydride by oxidizing o-xylene by using the composite catalyst bed provided by the invention can effectively improve the conversion rate of o-xylene and the yield of phthalic anhydride.

Description

Composite catalyst bed for preparing phthalic anhydride from o-xylene, preparation method of composite catalyst bed and method for preparing phthalic anhydride from o-xylene

Technical Field

The invention relates to the technical field of phthalic anhydride catalysts, in particular to a composite catalyst bed for preparing phthalic anhydride from o-xylene, a preparation method thereof and a method for preparing phthalic anhydride from o-xylene.

Background

Phthalic Anhydride (PA), abbreviated as phthalic anhydride, is the major market application area for ortho-xylene (OX). Phthalic anhydride is used as an important organic chemical raw material, the yield and consumption of the phthalic anhydride are the largest among four organic anhydrides, and the consumption uses mainly include three: firstly, dioctyl phthalate (DOP) is used for preparing phthalate plasticizers, such as plasticizer for polyvinyl chloride (PVC) resin; secondly, the glass reinforced thermosetting engineering plastic is used for manufacturing unsaturated polyester; thirdly, the alkyd resin is used for manufacturing alkyd resin and producing paint. With the development of petrochemical industry, the phthalic anhydride production capacity of the world steadily increases, and the annual production capacity of China is about 300 ten thousand tons.

The production process of phthalic anhydride mainly comprises two kinds of processes: fluidized bed gas phase oxidation process (nearly obsolete) of naphthalene and fixed bed gas phase oxidation process of ortho-xylene, the latter yield accounts for more than 90% of the world's total yield of phthalic anhydride.

The foreign phthalic anhydride catalyst is mainly researched and developed by BASF and other companies, the catalyst has a four-six-section system, and the feeding load is 90-100g/Nm ³ The yield of the phthalic anhydride is 114wt% in the first year.

In order to improve the quality and yield of phthalic anhydride, besides improving the process, the most important means is to improve the performance of the catalyst, so as to improve the feeding load, the yield of phthalic anhydride and the quality of phthalic anhydride, which represent the technical level and development trend of phthalic anhydride production.

The reaction for preparing phthalic anhydride by oxidizing o-xylene belongs to typical exothermic oxidation reaction, and for a composite catalyst bed system commonly used in industry, the reaction mainly concentrates on the inlet direction of o-xylene, and the reaction is usually intense, the hot spot temperature is high, deep oxidation is easy to occur, the byproduct carbon oxide is more, and the oxidizing capacity, namely the feeding load, is reduced.

Thus, there is a need for a new composite catalyst bed for the production of phthalic anhydride from ortho-xylene.

Disclosure of Invention

The invention aims to solve the problems of low catalytic efficiency of a catalyst, low phthalic anhydride yield and the like caused by uneven temperature distribution of a bed layer of a catalyst bed layer system for preparing phthalic anhydride by oxidizing o-xylene, and provides a novel composite catalyst bed layer for preparing phthalic anhydride by o-xylene, a preparation method thereof and a method for preparing phthalic anhydride by o-xylene.

In order to achieve the above object, a first aspect of the present invention provides a composite catalyst bed for producing phthalic anhydride from o-xylene, the composite catalyst bed comprising a catalyst E, a catalyst F, a catalyst G and a catalyst H, each independently comprising a support and an active component supported on the support, along a material flow direction;

Wherein the active ingredient contains V ₂ O ₅ ；

Wherein the catalyst E and the catalyst F also independently contain a heat conducting medium, and the catalyst G and the catalyst H do not contain a heat conducting medium.

The second aspect of the invention provides a method for preparing a composite catalyst bed for preparing phthalic anhydride from o-xylene, which comprises the following steps:

(1) Loading a first slurry containing a vanadium source, a titanium source, an optional phosphorus source, an optional cesium source, an auxiliary compound and a heat-conducting medium on a carrier, and drying and roasting to obtain a catalyst E;

(2) Loading a second slurry containing a vanadium source, a titanium source, an optional phosphorus source, an optional cesium source, an auxiliary compound and a heat-conducting medium on a carrier, and drying and roasting to obtain a catalyst F;

(3) Loading a third slurry containing a vanadium source, a titanium source, an optional phosphorus source, an optional cesium source and an auxiliary compound on a carrier, and drying and roasting to obtain a catalyst G;

(4) Loading a fourth slurry containing a vanadium source, a titanium source, an optional phosphorus source, an optional cesium source and an auxiliary compound on a carrier, and drying and roasting to obtain a catalyst H;

and the catalyst E, the catalyst F, the catalyst G and the catalyst H form a composite catalyst bed along the material flow direction.

In a third aspect, the present invention provides a method for producing phthalic anhydride from o-xylene, comprising: and (3) contacting and reacting o-xylene and oxygen-containing gas with the composite catalyst bed provided in the first aspect or the composite catalyst bed prepared by the method provided in the second aspect to obtain phthalic anhydride.

Compared with the prior art, the invention has the following advantages:

(1) According to the composite catalyst bed provided by the invention, the composite catalyst bed is limited to comprise the catalyst E, the catalyst F, the catalyst G and the catalyst H, and the catalyst E and the catalyst F are combined to contain the heat conducting medium, the catalyst G and the catalyst H do not contain the heat conducting medium, and particularly the physical property parameters of the heat conducting medium in the catalyst E and the catalyst F are limited, so that the heat conducting problem of the catalyst in the strong heat release section of the reaction can be effectively improved, the temperature of the bed is more uniform, and the reaction load, the selectivity and the catalytic performance of the catalyst bed are improved;

(2) The method for preparing phthalic anhydride by oxidizing o-xylene by using the composite catalyst bed provided by the invention can effectively improve the conversion rate of o-xylene and the yield of phthalic anhydride, namely, the conversion rate of o-xylene is up to 99.9%, and the yield of phthalic anhydride is up to 117.3%.

Detailed Description

The endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and are understood to encompass values approaching those ranges or values. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.

In the present invention, the terms "first", "second", "third" and "fourth" are used neither to indicate a sequence nor to limit the respective materials or steps, but are used only to distinguish between the respective materials or steps, for example, "first", "second", "third" and "fourth" among "first", "second", "third" and "fourth" are used only to distinguish between the same slurry.

The first aspect of the invention provides a composite catalyst bed for preparing phthalic anhydride from o-xylene, which comprises a catalyst E, a catalyst F, a catalyst G and a catalyst H along the flow direction of materials, wherein the catalyst E, the catalyst F, the catalyst G and the catalyst H respectively and independently comprise a carrier and an active component loaded on the carrier;

Wherein the active ingredient contains V ₂ O ₅ ；

The inventors of the present invention studied and found that: by defining catalyst E, catalyst F, catalyst G and catalyst H to contain V along the flow of the feed ₂ O ₅ And the catalyst E and the catalyst F are limited to contain specific heating media so as to improve the heat dissipation of the catalyst in the bed layer, ensure that the temperature distribution of the reaction zone is more uniform, and finally improve the overall performance of the catalyst, namely the reaction load, the selectivity and the catalytic performance of the catalyst.

In the present invention, unless otherwise specified, the catalyst E, the catalyst F, the catalyst G and the catalyst H are supported catalysts, and the supported catalysts comprise a carrier and an active component supported on the carrier, and the active component contains V ₂ O ₅ The catalyst E and the catalyst F contain a heat conducting medium; the catalyst G and the catalyst H do not contain a heat transfer medium.

In the invention, when the loading of the active components in the catalyst E, the catalyst F, the catalyst G and the catalyst H is too low, the conversion rate of o-xylene is relatively low; when the loading of active components in the catalyst E, the catalyst F, the catalyst G and the catalyst H is too high, the catalyst can be seriously subjected to deep oxidation, more byproducts are caused, and the yield of phthalic anhydride is obviously reduced.

In some embodiments of the present invention, preferably, in the catalyst E, the catalyst F, the catalyst G, and the catalyst H, the weight ratio of the carrier and the active component is 100:8-20, e.g., 100:8, 100:10, 100:12, 100:14, 100:15, 100:16, 100:20, and any value in the range of any two values, preferably 100:10-16. Wherein the weight ratio of the carrier to the active component means that 8-20g of the active component is loaded per 100g of the carrier.

In some embodiments of the invention, it is preferred that the active components each independently further comprise an adjunct, tiO ₂ Optionally a phosphorus compound, optionally a cesium compound.

In the invention, the types of the auxiliary agents have a wider selection range, so long as the auxiliary agents contain corresponding auxiliary agent elements, and the auxiliary agents are substances capable of obtaining corresponding auxiliary agent element oxides through subsequent treatment. Preferably, the promoter is selected from at least one of rubidium, cerium, niobium, chromium, silver, cobalt, gallium, indium, antimony, bismuth, zirconium and tungsten elements.

In some embodiments of the present invention, preferably, the phosphorus compound content in terms of P in each of the catalyst E, catalyst F, catalyst G and catalyst H is 0 to 0.5wt%, preferably 0 to 0.25wt%, based on the total weight of the active components; the cesium compound content in terms of Cs is 0-1wt%, preferably 0.05-1wt%; the content of auxiliaries calculated as oxide is 0.1-10wt%, preferably 0.5-5wt%; tiO (titanium dioxide) ₂ The content is 71-98.3wt%, preferably 76.95-98.75wt%. The adoption of the preferable conditions is more beneficial to the improvement of the catalytic activity of the catalyst bed layer.

In some embodiments of the present invention, preferably, in the catalyst E, V is based on the total weight of the active component ₂ O ₅ The content of (C) is 3-12wt%, preferably 4-11wt%.

In some embodiments of the present invention, preferably, in the catalyst F, V, based on the total weight of the active component ₂ O ₅ The content of (C) is 4-13wt%, preferably 6-12wt%.

In some embodiments of the present invention, preferably, in the catalyst G, V is based on the total weight of the active component ₂ O ₅ The content of (C) is 6-17wt%, preferably 7-16wt%.

In some embodiments of the present invention, preferably, in the catalyst H, V is based on the total weight of the active component ₂ O ₅ The content of (C) is 7-19wt%, preferably 8-18wt%.

In the present invention, the content of the heat conducting medium in the catalyst E and the catalyst F may be the same or may not be different, unless otherwise specified; preferably the same.

In some embodiments of the present invention, preferably, in the catalyst E and the catalyst F, a weight ratio of the heat conducting medium to the active component is 1 to 10:100, for example, any of the ranges 1:100, 3-100, 5-100, 6:100, 8:100, 10:100, and any two values, preferably 3-8:100. the adoption of the preferable conditions is more beneficial to providing heat dissipation of the catalyst E and the catalyst F and avoiding the deep oxidation of the product.

In some embodiments of the present invention, preferably, the heat-conducting medium is selected from BN whiskers and/or SiC whiskers, which have oxidation stability, high-temperature corrosion resistance and excellent heat conduction properties, and may assist in strengthening heat dissipation of the concentrated reaction section, reducing deep oxidation of the reaction, and increasing yield of phthalic anhydride.

In the present invention, the source of the heat-conducting medium has a wide selection range, and can be obtained through purchase or preparation, and the present invention is not described herein.

In some embodiments of the present invention, preferably, the heat-conducting medium exists in a fibrous form, so as to enhance the heat dissipation effect of the reaction concentrated heat dissipation section and avoid the deep oxidation of o-xylene; further preferably, the diameter size of the heat conducting medium is 0.1 to 10 μm, preferably 0.1 to 3 μm; aspect ratio is 40-200:1, preferably 80-150:1.

in the present invention, the kind of the carrier has a wide selection range, that is, the carrier is a kind conventional in the art. Preferably, the support is a non-porous inert support, preferably one or more selected from talc, silicon carbide, aluminum silicate, quartz and ceramic, preferably talc.

In the present invention, the shape of the carrier is not particularly limited, and may be, for example, cylindrical, spherical, annular or granular material, preferably annular.

In some embodiments of the invention, preferably, the carrier has an outer diameter of 3-13mm, preferably 3-8mm; the void fraction is 0 to 10%, preferably 1 to 8%.

In some embodiments of the present invention, preferably, in the composite catalyst bed, the packing height ratio of the catalyst E, the catalyst F, the catalyst G, and the catalyst H is 1 to 3:1-2:1-2:1, preferably 2-3:1.2-1.9:1.5-1.8:1. the high selectivity of the catalyst is divided into the E section and the F section so as to fully improve the selective oxidation of the catalyst.

According to a preferred embodiment of the present invention, preferably, the composite catalyst bed comprises catalyst E, catalyst F, catalyst G and catalyst H, each independently comprising a support and an active component supported on the support, along the flow direction of the stream;

wherein the active ingredient contains V ₂ O ₅ And V contained in each of the catalyst E and the catalyst F ₂ O ₅ The content of (2) is sequentially increased;

According to a particularly preferred embodiment of the invention, the composite catalyst bed comprises, along the material flow direction, catalyst E, catalyst F, catalyst G and catalyst H, each independently comprising a support and an active component supported on the support;

wherein the catalyst E and the catalyst F also independently contain a heat conducting medium, and the catalyst G and the catalyst H do not contain a heat conducting medium;

wherein, in the catalyst E and the catalyst F, the weight ratio of the heat conducting medium to the active components is 3-8:100;

wherein the heat conducting medium is selected from BN whisker and/or SiC whisker.

In some embodiments of the invention, preferably, the viscosity of the first, second, third and fourth slurries is each independently 10-40 mPa-s, preferably 12-20 mPa-s. In the present invention, the viscosity parameter is measured at 25 ℃.

In some embodiments of the present invention, preferably, in step (1), the preparing of the first slurry includes: (1-i) mixing oxalic acid, a vanadium source, an optional phosphorus source, an optional cesium source and a solvent to obtain a solution E; (1-ii) mixing the solution E with a heat transfer medium, a titanium source, an auxiliary compound, and a binder to obtain a first slurry.

In some embodiments of the present invention, preferably, the weight ratio of oxalic acid, vanadium source, phosphorus source, cesium source, solvent, heat conducting medium, titanium source, auxiliary compound and binder in the first slurry is 5-12:2-6:0-0.05:0-1:100:0-10:30-60:0.1-1.2:3-6, preferably 6-11:3-5:0-0.01:0.2-0.8:100:1-5:40-50:0.3-1:4-5.

In some embodiments of the present invention, preferably, in step (2), the preparing of the second slurry includes: (2-i) mixing oxalic acid, a vanadium source, an optional phosphorus source, an optional cesium source and a solvent to obtain a solution F; (2-ii) mixing the solution F with a heat transfer medium, a titanium source, an auxiliary compound, and a binder to obtain a second slurry.

In some embodiments of the present invention, preferably, the weight ratio of oxalic acid, vanadium source, phosphorus source, cesium source, solvent, heat conducting medium, titanium source, auxiliary compound and binder in the second slurry is 6-14:3-7:0-0.05:0-0.5:100:0-10:30-60:0.5-1.5:3-6, preferably 8-13:3-6:0-0.01:0.1-0.4:100:1-5:40-50:0.6-1.2:4-5.

In some embodiments of the present invention, preferably, in step (3), the preparing of the third slurry includes: (3-i) mixing oxalic acid, a vanadium source, an optional phosphorus source, an optional cesium source and a solvent to obtain a solution G; (3-ii) mixing the solution G with a titanium source, an auxiliary compound and a binder to obtain a third slurry.

In some embodiments of the present invention, preferably, the weight ratio of oxalic acid, vanadium source, phosphorus source, cesium source, solvent, titanium source, auxiliary compound and binder in the third slurry is 7-16:4-8:0-1:0-0.4:100:30-60:1-3:3-6, preferably 9-14:5-7:0.2-0.6:0.05-0.3:100:40-50:1.2-2.5:4-5.

In some embodiments of the present invention, preferably, in step (4), the preparing of the fourth slurry includes: (4-i) mixing oxalic acid, a vanadium source, an optional phosphorus source, an optional cesium source and a solvent to obtain a solution H; (4-ii) mixing the solution H with a titanium source, an auxiliary compound and a binder to obtain a fourth slurry.

In some embodiments of the present invention, preferably, the weight ratio of oxalic acid, vanadium source, phosphorus source, cesium source, solvent, titanium source, auxiliary compound and binder in the fourth slurry is 9-18:5-9:0-1:0-0.3:100:30-60:1-5:3-6, preferably 10-16:6-8:0.2-0.6:0.01-0.1:100:40-50:1.5-3:4-5.

According to the present invention, the manner of mixing in the steps (1), (2), (3) and (4) is not particularly limited, and wet milling may be employed, and the milling convenience and timeliness are combined, preferably the mixing is performed in a ball mill, more preferably the milling time in the ball mill is 1 to 5 hours, and preferably 2 to 4 hours.

In some embodiments of the present invention, preferably, the solvents in the first slurry, the second slurry, the third slurry, and the fourth slurry are each independently water-containing and water-soluble organic solvents; further preferably, the water-soluble organic solvent includes, but is not limited to, at least one of methanol, ethanol, formamide and N, N-dimethylamide.

In the present invention, the term "water-soluble" means readily soluble in water, or readily soluble in water by the aid of an auxiliary agent, unless otherwise specified.

In some embodiments of the present invention, preferably, the solvent has a weight ratio of water-soluble organic solvent to water of 1:4-16, e.g., 1:4, 1:5, 1:6, 1:7, 1:8, 1:10, 1:12, 1:14, 1:16, 1:18, and any of a range of any two values, preferably 1:5-8.

In the present invention, the binder is intended to promote a more uniform loading of the slurry on the carrier. Preferably, the binder is selected from at least one of vinyl acetate-acrylate copolymer emulsion, vinyl acetate-ethylene copolymer emulsion, vinyl acetate-maleate copolymer emulsion, and acrylic acid-maleic acid copolymer emulsion, preferably vinyl acetate-ethylene copolymer emulsion.

In the present invention, the kind of the vanadium source has a wide selection range. Preferably, the vanadium source is selected from ammonium metavanadate and/or vanadium pentoxide, preferably ammonium metavanadate.

In the present invention, the kind of the phosphorus source has a wide selection range. Preferably, the phosphorus source is selected from at least one of monoammonium phosphate, triammonium phosphate and phosphorus pentoxide, preferably monoammonium phosphate.

In the present invention, the cesium source has a wide selection range for the species. Preferably, the cesium source is selected from at least one of cesium nitrate, cesium sulfate, cesium chloride and cesium carbonate, preferably cesium sulfate.

In the present invention, the titanium source is selected from a wide range of types. Preferably, the titanium source is titanium dioxide; further preferably, the titanium dioxide is anatase TiO ₂ Specific surface area of 10-50m ² /g, e.g. 10m ² /g、15m ² /g、17m ² /g、20m ² /g、25m ² /g、30m ² /g、40m ² /g、50m ² G, and any value in the range of any two values, preferably 15-25m ² /g。

In some embodiments of the present invention, preferably, the promoter compound is a metal oxide and/or metal water-soluble salt containing at least one element selected from rubidium, cerium, niobium, chromium, silver, cobalt, gallium, indium, antimony, bismuth, zirconium, and tungsten. Further preferably, the metal oxide is an oxide of silver and/or an oxide of antimony, and the metal water-soluble salt is at least one of water-soluble salts of rubidium, cerium, niobium, chromium, tungsten, cobalt, bismuth, zirconium and tungsten elements.

In the present invention, the metal water-soluble salt may be nitrate, carbonate, sulfate, oxalate or the like unless otherwise specified.

In the present invention, the types of the carrier and the heat conducting medium are defined according to the above description, and the present invention is not repeated here.

In the present invention, the manner of loading in steps (1), (2), (3) and (4) is not particularly limited as long as the first slurry, the second slurry, the third slurry and the fourth slurry can be each independently loaded on the carrier. Preferably, the loading is by spraying.

According to the present invention, in order to accelerate volatilization of water and a soluble organic solvent in the first slurry, the second slurry, the third slurry, and the fourth slurry, the active ingredient is rapidly and effectively adhered. Preferably, hot air at 80-150 ℃ is adopted for drying in the spraying process; more preferably, the drying is carried out by hot air at 100 to 130 ℃.

In some embodiments of the present invention, preferably, the spray rates of the first, second, third, and fourth slurries satisfy: the weight of the carrier is increased by 0.5 to 0.75g/min, preferably 0.4 to 0.6g/min, per 100g of carrier. Controlling the spray rate within the above-defined range can prevent waste of the slurry and falling of the active component in the slurry.

According to the present invention, in order to make the first slurry, the second slurry, the third slurry, and the fourth slurry more easily adhere to the carrier. Preferably, the carrier is heated prior to spraying to maintain the temperature of the carrier at any value in the range of 80-150 ℃, e.g., 80 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃, 130 ℃, 150 ℃, and any two values, preferably 100-130 ℃.

According to the invention, the conditions of the calcination may be selected in a wide range. Preferably, the roasting conditions include: 400-450 ℃ for 2-24h.

The high temperature can make the adhesive disappear, and the adhesive force of the active component on the catalyst is reduced, so that the active component falls off in the catalyst filling process, so that in order to avoid the active component falling off in the catalyst filling process, the carrier is filled in the reactor, and then the catalyst is obtained by roasting in the reactor.

The device used for the spraying according to the present invention is not particularly limited as long as it can satisfy the requirement of the spraying.

In a third aspect, the present invention provides a method for producing phthalic anhydride from o-xylene, comprising: and (3) contacting and reacting o-xylene and air with the composite catalyst bed provided in the first aspect or the composite catalyst bed prepared by the method provided in the second aspect to obtain phthalic anhydride.

According to the present invention, preferably, the reaction conditions include: the molten salt temperature is 300-400 ℃, preferably 340-360 ℃; the volume airspeed is 1500-5000h ^-1 Preferably 3000-4000h ^-1 The method comprises the steps of carrying out a first treatment on the surface of the The concentration of o-xylene is 90-115g/m ³ Preferably 100-110g/m ³ . In the present invention, the pressure of the reaction is normal pressure, that is, the pressure is 0.1MPa.

In the present invention, the concentration of o-xylene refers to the number of g of o-xylene contained in a unit volume of air, and the higher the number, the higher the content of o-xylene in the air, unless otherwise specified.

According to the present invention, the reaction for producing phthalic anhydride from o-xylene may be carried out in a fixed bed or in a fluidized bed, preferably, the reaction for producing phthalic anhydride from o-xylene is carried out in a fixed bed single tube reactor, and more preferably, the fixed bed single tube reactor has a tube length of 3000 to 4800mm and an inner diameter of 20 to 30mm. The outside of the reaction tube of the fixed bed single tube reactor adopts circulating flowing molten salt to exchange reaction heat forcefully, a thermowell with the outer diameter of 5-10mm is arranged in the reaction tube, and a plurality of thermocouples with the same interval are arranged in the thermowell and are used for measuring the temperature of a reaction bed layer and the temperature of the molten salt, wherein the highest value of a temperature area is called as the temperature of a reaction hot spot. The outlet of the fixed bed single-tube reactor is connected with a product trapping device, and a sampling port is arranged at the outlet of the lower end of the reaction tube.

According to the invention, preferably, the catalyst in the reaction tube of the fixed bed single tube reactor adopts a sectional filling mode, and the total filling height is 2400-3400mm; according to the material direction, the filling height of the catalyst E is 30-50% of the total filling height, the filling height of the catalyst F is 10-30% of the total filling height, the filling height of the catalyst G is 15-35% of the total filling height, and the filling height of the catalyst H is 10-20% of the total filling height.

The present invention will be described in detail by examples.

Ammonium metavanadate having the molecular formula NH ₄ VO ₃ Its relative molecular weight is 116.98g/mol;

ammonium dihydrogen phosphate has the molecular formula of NH ₄ H ₂ PO ₄ Its relative molecular weight is 115.03g/mol;

cesium sulfate has the formula Cs ₂ SO ₄ Its relative molecular weight is 361.87g/mol;

the titanium dioxide is anatase titanium dioxide with specific surface area of 20-30m ² /g；

The reaction product is analyzed by a chromatographic analysis and chemical titration method;

the conversion (%) of o-xylene was calculated as:

the yield (%) of phthalic anhydride was calculated as:

example 1

(1)Catalyst E1

Solution E1 was prepared from 61.13g of ammonium metavanadate, 141.09g of oxalic acid, 5.57g of cesium sulfate, 3.14g of niobium oxalate, 200mL of formamide and 1200mL of water; wherein, the mass ratio of the formamide to the water is 1:6, preparing a base material;

pouring the solution E1 and 19.83g of heat-conducting medium (SiC whisker diameter 2 mu m, length-diameter ratio 100:1), 600g of titanium dioxide and 7.81g of antimonous oxide into a ball mill, adding 60g of vinyl acetate/ethylene copolymer emulsion, ball milling for 4 hours to form uniform first slurry, and controlling the viscosity of the first slurry to be 12 mPa.s;

2000g of talc ring carrier (outer diameter 8mm, height 6mm, wall thickness 1.5 mm) was placed in a drum of a spraying apparatus, and the drum speed was controlled to 10rpm; adding the prepared first slurry into a stirring tank of a feed liquid spraying system for stirring; starting an air heater, enabling hot air to penetrate into the rotary drum, preheating the carrier ring, and when the carrier temperature reaches 100 ℃, starting an atomization and feeding nozzle, controlling the hot air temperature to be 100 ℃, wherein the spraying rate is 0.5g/min for increasing the weight of each 100g of carrier; the first slurry is sprayed on the surface of the carrier magnetic ring through a nozzle and is quickly dried through hot air; the content of the active component reaches 15wt% of the weight of the carrier, spraying is completed, and the catalyst is roasted for 5 hours at 400 ℃ to obtain a catalyst E1;

Wherein the active component in the catalyst E1 contains V ₂ O ₅ Cesium compound, auxiliary agent (Nb, sb), heat-conducting medium and TiO ₂ The method comprises the steps of carrying out a first treatment on the surface of the V based on the content of the active ingredient ₂ O ₅ The content of cesium compound in terms of Cs was 7wt%, the content of Nb in terms of oxide was 0.23wt%, the content of Sb in terms of oxide was 1.15wt%, and TiO was 0.6wt% ₂ The content is 91.02wt%;

in the catalyst E1, the weight ratio of the heat conducting medium to the active component is 3:100.

(2)Catalyst F1

Solution F1 was prepared from 69.46g of ammonium metavanadate, 159.76g of oxalic acid, 3.61g of cesium sulfate, 3.57g of niobium oxalate, 200mL of formamide and 1200mL of water; wherein, the mass ratio of the formamide to the water is 1:6, preparing a base material;

pouring the solution F1 and 20.13g of heat conducting medium (SiC whisker diameter is 2 mu m, length-diameter ratio is 100:1), 600g of titanium dioxide and 12.72g of antimonous oxide into a ball mill, adding 60g of vinyl acetate/ethylene copolymer emulsion, ball milling for 4 hours to form uniform second slurry, and controlling the viscosity of the second slurry to be 12 mPa.s;

2000g of talc ring carrier (outer diameter 8mm, height 6mm, wall thickness 1.5 mm) were placed in a drum, and the drum speed was controlled to 10rpm; adding the prepared second slurry into a stirring tank of a feed liquid spraying system for stirring; starting an air heater, enabling hot air to penetrate into the rotary drum, preheating the carrier ring, and when the carrier temperature reaches 100 ℃, starting an atomization and feeding nozzle, controlling the hot air temperature to be 100 ℃, wherein the spraying rate is 0.5g/min for increasing the weight of each 100g of carrier; the second slurry is sprayed on the surface of the carrier magnetic ring through a nozzle and is quickly dried through hot air; the content of the active component reaches 15wt% of the weight of the carrier, spraying is completed, and the catalyst F1 is obtained after roasting for 5 hours at 400 ℃;

Wherein the active component in the catalyst F1 contains V ₂ O ₅ Cesium compound, auxiliary agent (Nb, sb), heat-conducting medium and TiO ₂ The method comprises the steps of carrying out a first treatment on the surface of the V based on the content of the active ingredient ₂ O ₅ The content of cesium compound in terms of Cs was 0.38wt%, nb in terms of oxide was 0.24wt%, sb in terms of oxide was 1.84wt%, tiO ₂ The content was 89.74wt%;

wherein, in the catalyst F1, the weight ratio of the heat conducting medium to the active component is 3:100.

(3)Catalyst G1

Solution G1 was prepared from 80.61G ammonium metavanadate, 185.45G oxalic acid, 1.96G cesium sulfate, 6.21G monoammonium phosphate, 3.67G niobium oxalate, 200mL formamide and 1200mL water; wherein, the mass ratio of the formamide to the water is 1:6, preparing a base material;

pouring the solution G1, 600G of titanium dioxide and 19.35G of antimonous oxide into a ball mill, adding 60G of vinyl acetate/ethylene copolymer emulsion, ball milling for 4 hours to form uniform third slurry, and controlling the viscosity of the third slurry to be 15 mPa.s;

2000g of talc ring carrier (outer diameter 8mm, height 6mm, wall thickness 1.5 mm) were placed in a drum, and the drum speed was controlled to 10rpm; adding the prepared third slurry into a stirring tank of a feed liquid spraying system for stirring; starting an air heater, enabling hot air to penetrate into the rotary drum, preheating the carrier ring, and when the carrier temperature reaches 100 ℃, starting an atomization and feeding nozzle, controlling the hot air temperature to be 100 ℃, wherein the spraying rate is 0.5g/min for increasing the weight of each 100g of carrier; the third slurry is sprayed on the surface of the carrier magnetic ring through a nozzle and is quickly dried through hot air; the content of the active component reaches 15wt% of the weight of the carrier, spraying is completed, and the catalyst is roasted for 5 hours at 400 ℃ to obtain a catalyst G1;

Wherein the active component in the catalyst G1 contains V ₂ O ₅ Cesium compound, phosphorus compound, auxiliary (Nb, sb) and TiO ₂ ；

Wherein, in the catalyst G1, based on the content of the active component, V ₂ O ₅ The content of cesium compound in terms of Cs was 9.1wt%, the content of cesium compound in terms of P was 0.21wt%, and the phosphorus compound in terms of P was obtainedThe content of the compound was 0.24wt%, the content of Nb was 0.26wt% in terms of oxide, the content of Sb was 2.89wt% in terms of oxide, and TiO ₂ The content was 87.3wt%.

(4)Catalyst H1

Solution H1 was prepared from 84.08g of ammonium metavanadate, 194.2g of oxalic acid, 0.87g of cesium sulfate, 5.91g of monoammonium phosphate, 6.23g of niobium oxalate, 200mL of formamide and 1200mL of water; wherein, the mass ratio of the formamide to the water is 1:6, preparing a base material;

pouring the solution H1, 600g of titanium dioxide and 19.35g of antimonous oxide into a ball mill, adding 60g of vinyl acetate/ethylene copolymer emulsion, ball milling for 4 hours to form uniform fourth slurry, and controlling the viscosity of the fourth slurry to be 15 mPa.s;

2000g of talc ring carrier (outer diameter 8mm, height 6mm, wall thickness 1.5 mm) were placed in a drum, and the drum speed was controlled to 10rpm; adding the prepared fourth slurry into a stirring tank of a feed liquid spraying system for stirring; starting an air heater, enabling hot air to penetrate into the rotary drum, preheating the carrier ring, and when the carrier temperature reaches 100 ℃, starting an atomization and feeding nozzle, controlling the hot air temperature to be 100 ℃, wherein the spraying rate is 0.5g/min for increasing the weight of each 100g of carrier; the fourth slurry is sprayed on the surface of the carrier magnetic ring through a nozzle and is quickly dried through hot air; the content of the active component reaches 15wt% of the weight of the carrier, spraying is completed, and the catalyst H1 is obtained after roasting for 5 hours at 400 ℃;

Wherein the active component in the catalyst H1 contains V ₂ O ₅ Cesium compound, phosphorus compound, auxiliary (Nb, sb) and TiO ₂ ；

Wherein, based on the content of the active component, V ₂ O ₅ The content of cesium compound in terms of Cs was 9.47wt%, the content of phosphorus compound in terms of P was 0.09wt%, the content of Nb in terms of oxide was 0.45wt%, the content of Sb in terms of oxide was 2.8wt%, and TiO was 0.23wt%, respectively ₂ The content is 86.96wt%;

along the material flow direction, the catalyst E1, the catalyst F1, the catalyst G1 and the catalyst H1 form a composite catalyst bed S1.

Example 2

(1)Catalyst E2

The preparation method of the catalyst E1 in example 1 was followed, except that 19.83g of the heat-conducting medium (SiC whisker diameter 2 μm, aspect ratio 100:1) was replaced with 57.88g of the heat-conducting medium (BN whisker diameter 2 μm, aspect ratio 100:1), and the other conditions were the same, to obtain a catalyst E2.

Wherein the active component in the catalyst E2 contains V ₂ O ₅ Cesium compound, auxiliary agent (Nb, sb), heat-conducting medium and TiO ₂ The method comprises the steps of carrying out a first treatment on the surface of the V based on the content of the active ingredient ₂ O ₅ The content of cesium compound in terms of Cs was 7wt%, the content of Nb in terms of oxide was 0.23wt%, the content of Sb in terms of oxide was 1.15wt%, and TiO was 0.6wt% ₂ The content is 91.02wt%;

in the catalyst E2, the weight ratio of the heat conducting medium to the active component is 8:100.

(2)Catalyst F2

The preparation method of the catalyst F1 in example 1 was followed, except that 20.13g of the heat-conducting medium (SiC whisker diameter 2 μm, aspect ratio 100:1) was replaced with 53.68g of the heat-conducting medium (BN whisker diameter 2 μm, aspect ratio 100:1), and the other conditions were the same, to obtain a catalyst F2.

Wherein the active component in the catalyst F2 contains V ₂ O ₅ Cesium compound, auxiliary agent (Nb, sb), heat-conducting medium and TiO ₂ The method comprises the steps of carrying out a first treatment on the surface of the V based on the content of the active ingredient ₂ O ₅ The content of cesium compound in terms of Cs was 0.38wt%, nb in terms of oxide was 0.24wt%, sb in terms of oxide was 1.84wt%, tiO ₂ The content was 89.74wt%;

wherein, in the catalyst F2, the weight ratio of the heat conducting medium to the active component is 8:100.

(3)Catalyst G2

Catalyst G1 prepared in example 1 was used as catalyst G2.

(4)Catalyst H2

Catalyst H1 prepared in example 1 was used as catalyst H2;

along the material flow direction, the catalyst E2, the catalyst F2, the catalyst G2 and the catalyst H2 form a composite catalyst bed S2.

Example 3

(1)Catalyst E3

The preparation method of the catalyst E1 in example 1 was followed, except that 19.83g of the heat-conducting medium (SiC whisker diameter 2 μm, aspect ratio 100:1) was replaced with 39.66g of the heat-conducting medium (SiC whisker diameter 2 μm, aspect ratio 100:1), and the other conditions were the same, to obtain a catalyst E3.

Wherein the active component in the catalyst E3 contains V ₂ O ₅ Cesium compound, auxiliary agent (Nb, sb), heat-conducting medium and TiO ₂ The method comprises the steps of carrying out a first treatment on the surface of the V based on the content of the active ingredient ₂ O ₅ The content of cesium compound in terms of Cs was 7wt%, the content of Nb in terms of oxide was 0.23wt%, the content of Sb in terms of oxide was 1.15wt%, and TiO was 0.6wt% ₂ The content is 91.02wt%;

in the catalyst E3, the weight ratio of the heat conducting medium to the active component is 6:100.

(2)Catalyst F3

The preparation method of the catalyst F1 in example 1 was followed, except that 20.13g of the heat-conducting medium (SiC whisker diameter 2 μm, aspect ratio 100:1) was replaced with 40.26g of the heat-conducting medium (SiC whisker diameter 2 μm, aspect ratio 100:1), and the other conditions were the same, to obtain a catalyst F3.

Wherein the active component in the catalyst F3 contains V ₂ O ₅ Cesium compound, auxiliary agent (Nb, sb), heat-conducting medium and TiO ₂ The method comprises the steps of carrying out a first treatment on the surface of the V based on the content of the active ingredient ₂ O ₅ The content of cesium compound in terms of Cs was 0.38wt%, nb in terms of oxide was 0.24wt%, sb in terms of oxide was 1.84wt%, tiO ₂ The content was 89.74wt%;

wherein, in the catalyst F3, the weight ratio of the heat conducting medium to the active component is 6:100.

(3) Catalyst G1 prepared in example 1 was used as catalyst G3.

(4) Catalyst H1 prepared in example 1 was used as catalyst H3;

along the material flow direction, the catalyst E3, the catalyst F3, the catalyst G3 and the catalyst H3 form a composite catalyst bed S3.

Example 4

According to example 1, except that catalyst F1 was replaced with catalyst F2 prepared in example 2, the remaining conditions were the same;

along the material flow direction, the catalyst E1, the catalyst F2, the catalyst G1 and the catalyst H1 form a composite catalyst bed S4.

Example 5

According to example 1, except,

in the catalyst E1, the weight ratio of the heat conducting medium to the active components is respectively replaced by 10:100, and the rest conditions are the same, so that a catalyst E5 is obtained;

in the catalyst F1, the weight ratio of the heat-conducting medium to the active components is respectively replaced by 10:100, and the rest conditions are the same, so that the catalyst F5 is obtained;

along the material flow direction, the catalyst E5, the catalyst F5, the catalyst G1 and the catalyst H1 form a composite catalyst bed S5.

Example 6

According to example 1, except,

in the catalyst E1, 19.83g of heat-conducting medium (whisker diameter is 2 mu m, length-diameter ratio is 100:1) is replaced by 39.66g of graphite powder particles (diameter is less than or equal to 20 mu m), and the rest conditions are the same, so that the catalyst E6 is obtained, wherein in the catalyst E6, the weight ratio of the graphite powder particles to the active components is 6:100;

In the catalyst F1, 20.13g of heat-conducting medium (whisker diameter is 2 mu m, length-diameter ratio is 100:1) is replaced by 40.26g of graphite powder particles (diameter is less than or equal to 20 mu m), and the rest conditions are the same, so that the catalyst F6 is obtained, wherein in the catalyst F6, the weight ratio of the graphite powder particles to the active components is 6:100;

along the material flow direction, the catalyst E6, the catalyst F6, the catalyst G1 and the catalyst H1 form a composite catalyst bed S6.

Comparative example 1

According to example 1, except,

in the catalyst E1, 19.83g of heat conducting medium (whisker diameter 2 μm, length-diameter ratio 100:1) is not added, and the rest conditions are the same, so as to obtain a catalyst DE1;

20.13g of heat conducting medium (whisker diameter 2 μm, length-diameter ratio 100:1) is not added into the catalyst F1, and the rest conditions are the same, so as to obtain a catalyst DF1;

along the material flow direction, the catalyst DE1, the catalyst DF1, the catalyst G1 and the catalyst H1 form a composite catalyst bed DS1.

Comparative example 2

According to example 1, except,

20.61G of heat-conducting medium (whisker diameter 2 μm, length-diameter ratio 100:1) is added into the catalyst G1, and the rest conditions are the same, so as to obtain a catalyst DG2; wherein, in the catalyst DG2, the weight ratio of the heat conducting medium to the active component is 3:100;

20.7g of heat conducting medium (whisker diameter 2 μm, length-diameter ratio 100:1) is added into the catalyst H1, and the rest conditions are the same, so as to obtain a catalyst DH2; wherein, in the catalyst DH2, the weight ratio of the heat conducting medium to the active component is 3:100;

along the material flow direction, the catalyst E1, the catalyst F1, the catalyst DG2 and the catalyst DH2 form a composite catalyst bed DS2.

Test case

The composite catalyst beds (S1-S6 and DS1-DS 2) prepared in examples 1-6 and comparative examples 1-2 were subjected to catalytic performance testing.

The method comprises the steps of filling catalysts by adopting a fixed bed single tube reactor simulating industrial production conditions, wherein the inner diameter of the fixed bed single tube reactor is 29mm, the tube length is 4400mm, the filling height is 3400mm, a multi-point thermocouple is arranged in the tube for measuring temperature, circulating molten salt is adopted for heat exchange outside the tube, and the reactors are respectively filled with the catalysts E, F, G and H prepared in the examples and the comparative examples according to the material flow direction, wherein the filling height of the catalyst E is 1400mm, the filling height of the catalyst F is 700mm, the filling height of the catalyst G is 800mm, and the filling height of the catalyst H is 500mm. The outlet of the reactor is connected with a DSC analysis system, and the tail end of the reaction tube is connected with a product collecting box.

Preparation and preparationThe conditions for evaluating the catalysts are the same, after the catalyst E, the catalyst F, the catalyst G and the catalyst H are filled in a reaction tube, the temperature is raised to 400 ℃, the catalyst E, the catalyst F, the catalyst G and the catalyst H are activated for 10 hours in an oxidizing atmosphere, molten salt is cooled to 398 ℃ for feeding, the hot spot temperature is controlled after feeding, and the airspeed is 3500 hours ^-1 The pressure was 0.1MPa, the o-xylene feed concentration was gradually increased, and product sampling and analysis at each condition was performed at the reactor outlet to examine the catalyst peak load, o-xylene conversion and phthalic anhydride yield index, and the test results are shown in Table 1.

TABLE 1

As can be seen from the results of Table 1, the composite catalyst bed provided by the invention is used for preparing phthalic anhydride from o-xylene by limiting V in the catalyst E, the catalyst F, the catalyst G and the catalyst H ₂ O ₅ The content of the heat conducting medium in the catalyst E and the catalyst F can effectively improve the concentration and the conversion rate of the o-xylene and the yield of the phthalic anhydride, and particularly limit the V in the catalyst E, the catalyst F, the catalyst G and the catalyst H ₂ O ₅ The contents of the catalyst E and the catalyst F are in the preferred protective ranges, and the concentration and conversion rate of o-xylene and the yield of phthalic anhydride can be further improved.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, a number of simple variants of the technical solution of the invention are possible, including combinations of the individual technical features in any other suitable way, which simple variants and combinations should likewise be regarded as being disclosed by the invention, all falling within the scope of protection of the invention.

Claims

1. A composite catalyst bed for preparing phthalic anhydride from o-xylene, which is characterized in that the composite catalyst bed comprises a catalyst E, a catalyst F, a catalyst G and a catalyst H along the flow direction of materials, wherein the catalyst E, the catalyst F, the catalyst G and the catalyst H respectively and independently comprise a carrier and an active component loaded on the carrier;

wherein the active ingredient contains V ₂ O ₅ ；

2. The composite catalyst bed according to claim 1, wherein the weight ratio of the carrier to the active components in the catalyst E, catalyst F, catalyst G and catalyst H is 100:8-20, preferably 100:10-16;

And/or the active components each independently further comprise an auxiliary agent and TiO ₂ An optional phosphorus compound, an optional cesium compound;

and/or the auxiliary agent is selected from at least one of rubidium, cerium, niobium, chromium, silver, cobalt, gallium, indium, antimony, bismuth, zirconium and tungsten elements.

3. The composite catalyst bed according to claim 2, wherein the content of phosphorus compounds in terms of P in each of the catalyst E, catalyst F, catalyst G and catalyst H is 0-0.5wt%, preferably 0-0.25wt%, based on the total weight of the active components; the cesium compound content in terms of Cs is 0-1wt%, preferably 0.05-1wt%; the content of auxiliaries calculated as oxide is 0.1-10wt%, preferably 0.5-5wt%; tiO (titanium dioxide) ₂ The content is 71-98.3wt%, preferably 76.95-98.75wt%.

4. A composite catalyst bed according to any one of claims 1-3, wherein in the catalyst E, V, based on the total weight of the active components ₂ O ₅ The content of (2) is 3-12wt%, preferably 4-11wt%;

and/or, in the catalyst F, V based on the total weight of the active components ₂ O ₅ The content of (C) is 4-13wt%, preferably 6-12wt%；

And/or, in the catalyst G, V based on the total weight of the active components ₂ O ₅ The content of (2) is 6-17wt%, preferably 7-16wt%;

and/or, in the catalyst H, V based on the total weight of the active components ₂ O ₅ The content of (C) is 7-19wt%, preferably 8-18wt%.

5. The composite catalyst bed according to any one of claims 1 to 4, wherein the weight ratio of the heat conducting medium to the active component in the catalyst E and the catalyst F is 1 to 10:100, preferably 3-8:100;

and/or the heat conducting medium is selected from BN whisker and/or SiC whisker;

and/or the heat-conducting medium is present in fibrous form;

and/or the diameter size of the heat-conducting medium is 0.1-10 μm, preferably 0.1-3 μm; aspect ratio is 40-200:1, preferably 80-150:1, a step of;

and/or the carrier is a non-porous inert carrier, preferably one or more selected from talc, silicon carbide, aluminum silicate, quartz and ceramic, preferably talc;

and/or the shape of the carrier is selected from cylindrical, spherical, annular or particulate material, preferably annular;

and/or the carrier has an outer diameter of 3-13mm, preferably 3-8mm; void fraction of 0-10%, preferably 1-8%;

and/or, in the composite catalyst bed, the filling height ratio of the catalyst E to the catalyst F to the catalyst G to the catalyst H is 1-3:1-2:1-2:1, preferably 2-3:1.2-1.9:1.5-1.8:1.

6. The preparation method of the composite catalyst bed for preparing phthalic anhydride from o-xylene is characterized by comprising the following steps:

7. The method of claim 6, wherein the viscosity of the first, second, third and fourth slurries is each independently 10-40 mPa-s, preferably 12-20 mPa-s;

And/or, in step (1), the preparation of the first slurry comprises:

(1-i) mixing oxalic acid, a vanadium source, an optional phosphorus source, an optional cesium source and a solvent to obtain a solution E;

(1-ii) mixing the solution E with a heat transfer medium, a titanium source, an auxiliary compound and a binder to obtain a first slurry;

and/or, in step (2), the preparation of the second slurry comprises:

(2-i) mixing oxalic acid, a vanadium source, an optional phosphorus source, an optional cesium source and a solvent to obtain a solution F;

(2-ii) mixing the solution F with a heat transfer medium, a titanium source, an auxiliary compound, and a binder to obtain a second slurry;

and/or, in step (3), the preparation of the third slurry comprises:

(3-i) mixing oxalic acid, a vanadium source, an optional phosphorus source, an optional cesium source and a solvent to obtain a solution G;

(3-ii) mixing the solution G with a titanium source, an auxiliary compound and a binder to obtain a third slurry;

and/or, in step (4), the preparation of the fourth slurry comprises:

(4-i) mixing oxalic acid, a vanadium source, an optional phosphorus source, an optional cesium source and a solvent to obtain a solution H;

(4-ii) mixing the solution H with a titanium source, an auxiliary compound and a binder to obtain a fourth slurry.

8. The method of claim 7, wherein the weight ratio of oxalic acid, vanadium source, phosphorus source, cesium source, solvent, heat conducting medium, titanium source, auxiliary compound and binder in the first slurry is 5-12:2-6:0-0.05:0-1:100:0-10:30-60:0.1-1.2:3-6, preferably 6-11:3-5:0-0.01:0.2-0.8:100:1-5:40-50:0.3-1:4-5;

and/or, in the second slurry, the weight ratio of oxalic acid, vanadium source, phosphorus source, cesium source, solvent, heat conducting medium, titanium source, auxiliary compound and adhesive is (by weight ratio) 6-14:3-7:0-0.05:0-0.5:100:0-10:30-60:0.5-1.5:3-6, preferably 8-13:3-6:0-0.01:0.1-0.4:100:1-5:40-50:0.6-1.2:4-5;

and/or, in the third slurry, the weight ratio of oxalic acid, vanadium source, phosphorus source, cesium source, solvent, titanium source, auxiliary compound and binder is 7-16:4-8:0-1:0-0.4:100:30-60:1-3:3-6, preferably 9-14:5-7:0.2-0.6:0.05-0.3:100:40-50:1.2-2.5:4-5;

and/or, in the fourth slurry, the weight ratio of oxalic acid, vanadium source, phosphorus source, cesium source, solvent, titanium source, auxiliary compound and binder is 9-18:5-9:0-1:0-0.3:100:30-60:1-5:3-6, preferably 10-16:6-8:0.2-0.6:0.01-0.1:100:40-50:1.5-3:4-5;

And/or the solvents in the first slurry, the second slurry, the third slurry and the fourth slurry are each independently water-containing and water-soluble organic solvents;

and/or, the weight ratio of the water-soluble organic solvent to the water in the solvent is 1:4-16, preferably 1:5-8;

and/or the water-soluble organic solvent is selected from at least one of methanol, ethanol, formamide and N, N-dimethylamide;

and/or the adhesive is selected from at least one of vinyl acetate-acrylic ester copolymer emulsion, vinyl acetate-ethylene copolymer emulsion, vinyl acetate-maleic ester copolymer emulsion and acrylic acid-maleic acid copolymer emulsion.

9. The method according to any one of claims 6-8, wherein the vanadium source is selected from ammonium metavanadate and/or vanadium pentoxide;

and/or the phosphorus source is selected from at least one of monoammonium phosphate, triammonium phosphate and phosphorus pentoxide;

and/or, the cesium source is selected from at least one of cesium nitrate, cesium sulfate, cesium chloride, and cesium carbonate;

and/or the titanium source is titanium dioxide, preferably anatase TiO ₂ Specific surface area of 10-50m ² /g, preferably 15-25m ² /g；

And/or the auxiliary compound is a metal oxide and/or metal water-soluble salt containing at least one element selected from rubidium, cerium, niobium, chromium, silver, cobalt, gallium, indium, antimony, bismuth, zirconium and tungsten;

and/or the heat-conducting medium is present in fibrous form;

and/or the carrier is selected from one or more of talc, silicon carbide, aluminum silicate, quartz and ceramic, preferably talc;

and/or the shape of the carrier is selected from cylindrical, spherical, annular or granular, preferably annular;

and/or the carrier has an outer diameter of 3-13mm, preferably 3-8mm; the void fraction is 0 to 10%, preferably 1 to 8%.

10. A method for producing phthalic anhydride from o-xylene, comprising: contacting and reacting o-xylene and an oxygen-containing gas with the composite catalyst bed according to any one of claims 1 to 5, or the composite catalyst bed produced by the method according to any one of claims 6 to 9, to obtain phthalic anhydride.