Reactor filled with catalyst, use thereof and method for preparing phthalic anhydride

Abstract

The present invention relates to the field of catalyst technology and discloses a reactor filled with a catalyst, the reactor comprising at least three catalyst beds arranged in sequence, wherein the activity of the catalyst in the second and subsequent catalyst beds increases in sequence, and the activity of the catalyst in the first catalyst bed is between the activities of the catalyst in the second and final catalyst beds. The present invention also provides a method for preparing phthalic anhydride, the method comprising introducing naphthalene and oxygen into the reactor and sequentially contacting the catalyst in the first and subsequent catalyst beds to react. This method improves the activity of the catalyst in the inlet section, reduces the distance to the catalyst activation section, improves the utilization efficiency of the catalyst beds, and thereby improves the yield of the reaction product, phthalic anhydride.

Description

Technical Field

[0001] The present invention relates to the technical field of phthalic anhydride preparation, and in particular to a reactor filled with a catalyst, and an application thereof and a method for preparing phthalic anhydride. Background Art

[0002] Phthalic anhydride (PA), also known as phthalic anhydride, is the primary market application for o-xylene (OX). Among the four major organic anhydrides, it has the largest production and consumption. Phthalic anhydride has three main uses: first, in the preparation of phthalate plasticizers (accounting for half of global phthalic anhydride production, primarily dioctyl phthalate (DOP), used as a plasticizer in polyvinyl chloride (PVC) resins); second, in the manufacture of unsaturated polyesters for glass-reinforced thermosetting engineering plastics; and third, in the manufacture of alkyd resins for surface coatings. With the development of the petrochemical industry, demand for PA is increasing. However, the persistently high price of o-xylene, the raw material used in phthalic anhydride production, has led to an inverse relationship between phthalic anhydride and raw material prices, impacting business operations. The recent decline in industrial naphthalene prices has prompted some phthalic anhydride producers to reconsider using the naphthalene process to reduce costs and increase competitiveness. Consequently, the new naphthalene process and its corresponding catalysts are gaining market favor.

[0003] Currently, patents for naphthalene oxidation to produce phthalic anhydride mainly focus on the optimization of additives and formulations. BASF has developed a new catalyst for the process of producing phthalic anhydride by the mixed oxidation of o-xylene and naphthalene. The active components of this catalyst are vanadium oxide and titanium dioxide, and may contain mixed oxides of cesium compounds, phosphorus compounds, antimony oxide, and specific metals (such as lithium, potassium, rubidium, etc.). The preparation method of this catalyst is to apply one or more shell-like coatings on an inert porous carrier, so that the alkali metal content of one catalyst layer A is the highest; in the flow direction, the catalyst layers B, C, etc. located after catalyst layer A have an alkali metal content ranging from 0% to 90% of that of catalyst layer A, and the alkali metal content of each catalyst layer is higher than the alkali metal of the catalyst layer after it in the flow direction. However, this method suffers from the problem of insufficient catalyst bed utilization efficiency.

[0004] Klein Corporation has developed a multilayer catalyst for producing phthalic anhydride. This catalyst utilizes a catalyst arrangement comprising a first catalyst layer at the gas inlet side and at least one second catalyst layer with different catalytic activity downstream of the first catalyst layer along the gas flow direction. However, this method suffers from low yields.

[0005] The imported phthalic anhydride catalysts used in China for the naphthalene process mainly come from BASF. The company divides the catalyst into 3-6 beds. The catalyst distribution is the same as that of the o-naphthalene mixed process. The raw material feed rate is 60-80g / Nm 3 The pure yield of phthalic anhydride in the first year is 102-103%. However, this method also has the problem of low product yield.

[0006] The reaction of naphthalene oxidation to produce phthalic anhydride is a typical exothermic oxidation reaction. When using catalysts of the same activity to carry out the reaction, due to the high concentration of reactants in the inlet section, local overheating can cause the product to further deeply oxidize to carbon oxides, reducing the yield of phthalic anhydride. In the prior art, in order to carry out the reaction process under relatively mild conditions, the catalyst bed is divided into several reaction zones, and catalysts of different activities are loaded to adapt to the concentration of reactants in different reaction zones. Generally, the catalyst bed is divided into four reaction zones, and the catalyst activity of each reaction zone increases successively from the inlet section, thereby avoiding catalyst overheating and deactivation caused by the high concentration of reactants in the inlet section or the deep oxidation of phthalic anhydride to carbon oxides. However, this method has low catalyst bed utilization and low phthalic anhydride yield. Summary of the Invention

[0007] The purpose of the present invention is to overcome the problems of low catalyst bed utilization and low phthalic anhydride yield in the prior art, and to provide a reactor filled with a catalyst and a method for using and preparing phthalic anhydride. When the reactor filled with the catalyst is used to prepare phthalic anhydride, the catalyst bed utilization can be improved and the phthalic anhydride yield can be improved.

[0008] The inventors considered the overall utilization of the catalyst bed and broke the prior art design method of increasing the vanadium content of the catalyst from the inlet section, appropriately improving the activity of the inlet section and increasing the yield of the reaction product phthalic anhydride.

[0009] In order to achieve the above-mentioned objectives, the first aspect of the present invention provides a reactor filled with a catalyst, which includes at least three catalyst beds arranged in sequence, wherein the vanadium content of the catalyst in the second and subsequent catalyst beds increases successively, and the vanadium content of the catalyst in the first catalyst bed is between the vanadium content of the catalyst in the second catalyst bed and the last catalyst bed.

[0010] A second aspect of the present invention provides a use of the above reactor in the preparation of phthalic anhydride.

[0011] A third aspect of the present invention provides a method for preparing phthalic anhydride, which comprises introducing naphthalene and oxygen into the above-mentioned reactor to sequentially contact the catalysts in the first and subsequent catalyst beds for reaction.

[0012] Compared with the prior art, the present invention provides a new catalyst loading method, which improves the yield of the reaction product phthalic anhydride by improving the activity of the catalyst in the inlet section. DETAILED DESCRIPTION

[0013] The endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0014] A first aspect of the present invention provides a reactor filled with a catalyst, which includes at least three catalyst beds arranged in sequence, wherein the vanadium content of the catalyst in the second and subsequent catalyst beds increases successively, and the vanadium content of the catalyst in the first catalyst bed is between the vanadium content of the catalyst in the second catalyst bed and the last catalyst bed.

[0015] According to the present invention, preferably, the catalysts in the catalyst bed each independently include a carrier and an active component supported on the carrier, and the active component includes V2O5 and TiO2.

[0016] According to the present invention, preferably, the V2O5 content in the catalyst in the second and subsequent catalyst beds is increased in a range of 0.2-2 wt%.

[0017] According to the present invention, preferably, the V2O5 content in the catalyst in the second catalyst bed is 5.5-6.6% by weight.

[0018] According to the present invention, preferably, the V2O5 content in the catalyst in the last catalyst bed is 8-11% by weight.

[0019] According to the present invention, preferably, the V2O5 content in the catalyst in the first catalyst bed is 5.7-7% by weight.

[0020] According to the present invention, preferably, the reactor comprises 3-10 catalyst beds, preferably 5 catalyst beds.

[0021] According to the present invention, preferably, the reactor includes 5 catalyst beds, wherein the molar ratio of V2O5 and TiO2 in the catalyst in the first catalyst bed is 0.028-0.034:1, the molar ratio of V2O5 and TiO2 in the catalyst in the second catalyst bed is 0.026-0.032:1, the molar ratio of V2O5 and TiO2 in the catalyst in the third catalyst bed is 0.029-0.033:1, the molar ratio of V2O5 and TiO2 in the catalyst in the fourth catalyst bed is 0.032-0.037:1, and the molar ratio of V2O5 and TiO2 in the catalyst in the fifth catalyst bed is 0.04-0.047:1.

[0022] According to the present invention, in order to improve the utilization rate of the catalyst bed, preferably, the thickness ratio of the first catalyst bed, the second catalyst bed, the third catalyst bed, the fourth catalyst bed and the fifth catalyst bed is (0.5-2): (1-2.3): (0.6-1.5): (1.5-2.2): 1, preferably (0.6-1.6): (1.2-2.2): (1-1.4): (1.6-2): 1.

[0023] According to the present invention, the preparation method of the catalyst is not particularly limited and can be prepared according to methods commonly used in the art. Preferably, the preparation method of the catalyst in each catalyst bed independently comprises: contacting a slurry containing a vanadium source, a titanium source, and an optional auxiliary agent with a support, and then drying and activating the contact product to obtain the catalyst. Further preferably, the preparation method of the catalyst comprises: mixing a solution A containing a vanadium source and an auxiliary agent with a titanium source, an antimony source, and a binder to obtain a slurry, contacting the slurry with a support, and then drying and activating the contact product to obtain the catalyst.

[0024] According to the preparation method of the catalyst of the present invention, preferably, the weight gain of the dried product is 14-18% by weight relative to every 2000 g of the carrier.

[0025] According to the present invention, preferably, based on the total amount of active components in the catalyst, the amounts of the titanium source, vanadium source, and promoter are such that, in each catalyst bed, the catalyst has a V2O5 content of 5-15% by weight, preferably 5.5-9.6% by weight, a TiO2 content of 80-94% by weight, preferably 88-93% by weight, and a promoter content, calculated as oxide, of 0.5-10% by weight, preferably 0.8-4% by weight. The active components include V2O5, TiO2, and the oxides of the promoters.

[0026] According to the present invention, preferably, the difference between the V2O5 content in the catalyst in the fifth catalyst bed and the V2O5 content in the catalyst in the fourth catalyst bed is 1-10 times, preferably 2-8 times, and more preferably 3-5 times the difference between the V2O5 content in the catalyst in the third catalyst bed and the V2O5 content in the catalyst in the second catalyst bed.

[0027] According to the present invention, preferably, the V2O5 content in the catalyst in the first catalyst bed is 5.7-5.8 weight %, the V2O5 content in the catalyst in the second catalyst bed is 5.5-5.6 weight %, the V2O5 content in the catalyst in the third catalyst bed is 5.9-6.1 weight %, the V2O5 content in the catalyst in the fourth catalyst bed is 6.5-6.7 weight %, and the V2O5 content in the catalyst in the fifth catalyst bed is 8.2-8.5 weight %.

[0028] According to the present invention, preferably, the carrier is at least one of talc, silicon carbide, aluminum silicate, quartz and ceramics, more preferably talc.

[0029] According to the present invention, the shape of the carrier is not particularly limited, and can be, for example, cylindrical, spherical, annular or granular. Preferably, the shape of the carrier is an annular carrier.

[0030] According to the present invention, the type of the titanium source is not particularly limited. Preferably, the titanium source is titanium dioxide and / or metatitanic acid. Further preferably, the titanium dioxide is anatase-type titanium dioxide, and the specific surface area of the titanium dioxide is 10-30 m 2 / g, more preferably 15-25m 2 / g.

[0031] According to the present invention, the type of the vanadium source is not particularly limited. Preferably, the vanadium source is ammonium metavanadate and / or vanadium pentoxide, more preferably ammonium metavanadate.

[0032] According to the present invention, the type of the additive is not particularly limited, as long as it contains the corresponding additive element. The additive is a substance that can be subsequently treated to obtain an oxide of the corresponding additive element. Preferably, the additive contains at least one element selected from phosphorus, cesium, niobium, silver, antimony, zirconium, rubidium, cerium, chromium, tungsten, cobalt, gallium, indium, bismuth, and erbium.

[0033] According to the present invention, preferably, the catalysts in the first catalyst bed and the second catalyst bed do not contain phosphorus as a promoter.

[0034] According to the present invention, preferably, the catalysts in the first catalyst bed, the second catalyst bed and the third catalyst bed do not contain the promoter zirconium element.

[0035] According to the present invention, preferably, the catalysts in the third catalyst bed, the fourth catalyst bed and the fifth catalyst bed do not contain the promoter silver element.

[0036] According to the present invention, preferably, the promoter in the catalyst in the first catalyst bed is selected from cesium, niobium, silver and antimony elements, the promoter in the catalyst in the second catalyst bed is selected from cesium, niobium, silver and antimony elements, the promoter in the catalyst in the third catalyst bed is selected from cesium, phosphorus, niobium and antimony elements, the promoter in the catalyst in the fourth catalyst bed is selected from cesium, phosphorus, niobium, zirconium and antimony elements, and the promoter in the catalyst in the fifth catalyst bed is selected from cesium, phosphorus, niobium, zirconium and antimony elements.

[0037] According to the present invention, the auxiliary agent may include a phosphorus source capable of providing phosphorus element. Preferably, the phosphorus source is at least one of ammonium dihydrogen phosphate, triammonium phosphate and phosphorus pentoxide, more preferably ammonium dihydrogen phosphate.

[0038] According to the present invention, the auxiliary agent may include a metal oxide and / or a water-soluble metal salt capable of providing the above-mentioned metal elements; further preferably, the metal oxide is silver oxide and / or antimony oxide, and the water-soluble metal salt is at least one of water-soluble salts of cesium, niobium, zirconium, rubidium, cerium, chromium, tungsten, cobalt, gallium, indium, bismuth and erbium.

[0039] In the present invention, the water-soluble metal salt may be nitrate, carbonate, sulfate, oxalate, chloride, or the like.

[0040] According to the present invention, preferably, the water-soluble salt of cesium is at least one of cesium nitrate, cesium sulfate and cesium chloride, more preferably cesium sulfate.

[0041] According to the present invention, preferably, the water-soluble salt of niobium is niobium oxalate.

[0042] According to the present invention, the drying conditions can be selected in a wide range. Preferably, the drying temperature is 80-120°C.

[0043] According to the present invention, the activation conditions can be selected from a wide range. Preferably, the activation conditions include: a temperature of 390-410° C. and a time of 4-24 h.

[0044] According to the present invention, preferably, the slurry further contains a binder. Further preferably, the binder is at least one of a vinyl acetate-acrylate copolymer emulsion, a vinyl acetate-ethylene copolymer emulsion, a vinyl acetate-maleic acid copolymer emulsion, and an acrylic acid-maleic acid copolymer emulsion, and is preferably a vinyl acetate-ethylene copolymer emulsion.

[0045] The present invention allows for a wide range of binder dosage. To ensure a more uniform loading of the active ingredient on the carrier, the binder is preferably added in an amount such that the slurry viscosity is 10-40 mPa·s, preferably 12-25 mPa·s. The binder can be used in any form as long as the slurry viscosity is within the specified range. Preferably, the binder is used in the form of an emulsion. Furthermore, preferably, the binder has a solids content of 10-15% by weight.

[0046] According to the present invention, preferably, the solvent in the slurry includes water and an organic solvent.

[0047] According to the present invention, preferably, the organic solvent is at least one of methanol, ethanol, formamide, and N,N-dimethylformamide.

[0048] According to the present invention, preferably, the mass ratio of the organic solvent to water in the slurry is 0.1-0.5:1, preferably 0.1-0.4:1.

[0049] According to the present invention, the loading method is not particularly limited, as long as the slurry can be loaded onto the carrier. Preferably, the loading method is spraying, and the temperature of the slurry during the spraying process is 20-60°C.

[0050] According to the present invention, preferably, the spraying rate is 30-70 mL / min, preferably 35-60 mL / min, per 2000 g of the carrier.

[0051] According to the present invention, in order to make the slurry adhere to the carrier more easily, preferably, the carrier is heated before spraying so that the temperature of the carrier is maintained at 70-140°C, preferably 80-130°C.

[0052] A second aspect of the present invention provides an application of the above-mentioned reactor in the production of phthalic anhydride by oxidation of naphthalene.

[0053] A third aspect of the present invention provides a method for preparing phthalic anhydride, which comprises introducing naphthalene and oxygen into the above-mentioned reactor to sequentially contact the catalysts in the first and subsequent catalyst beds for reaction.

[0054] According to the present invention, preferably, the reaction conditions include: temperature of 300-450°C, pressure of 0-0.1 MPa, oxygen volume space velocity of 300-1000h -1 , the concentration of naphthalene is 70-85g / Nm 3 .

[0055] According to the present invention, the oxygen can be provided in the form of pure oxygen or in the form of an oxygen-containing gas. Preferably, the oxygen is provided in the form of air, and more preferably, the volume space velocity of the air is 1500-5000h -1 , more preferably 3000-4000h -1 .

[0056] The present invention will be described in detail below by way of examples.

[0057] The carrier is talc ring.

[0058] Titanium dioxide is anatase-type titanium dioxide with a specific surface area of 20 m 2 / g.

[0059] The catalytic products were analyzed by chromatography.

[0060] Phthalic anhydride yield = weight of product phthalic anhydride ÷ weight of reacted naphthalene × 100%.

[0061] Preparation Example 1

[0062] (1) 53.84 g of ammonium metavanadate, 128.95 g of oxalic acid, 5.05 g of cesium sulfate, 5.94 g of niobium oxalate, 220 g of formamide and 2200 g of water were prepared into a solution.

[0063] (2) The solution, 663.24 g of titanium dioxide, 0.92 g of silver oxide, and 11.45 g of antimony trioxide were poured into a ball mill, and an appropriate amount of vinyl acetate-ethylene copolymer emulsion was added. The mixture was ball milled for 4 h to form a uniform slurry, and the slurry viscosity was controlled to 16 Pa·s.

[0064] (3) Place 2000 g of the carrier in a rotating drum at a speed of 10 rpm; add the slurry prepared above to the stirring tank of the liquid spraying system and stir; start the hot air blower, allowing hot air to penetrate the drum to preheat the carrier. 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 60 mL / min; spray the slurry onto the carrier surface through the nozzle and rapidly dry it with the hot air. The carrier weight increases by 14.6 wt% after spraying is completed, and then activate at 400°C for 4 h to prepare Catalyst A.

[0065] Preparation Example 2

[0066] (1) 51.26 g of ammonium metavanadate, 115.33 g of oxalic acid, 4.93 g of cesium sulfate, 5.72 g of niobium oxalate, 220 g of formamide and 1100 g of water were prepared into a solution.

[0067] (2) The solution, 663.24 g of titanium dioxide, 0.84 g of silver oxide, and 11.62 g of antimony trioxide were poured into a ball mill, and an appropriate amount of vinyl acetate-ethylene copolymer emulsion was added. The mixture was ball milled for 4 h to form a uniform slurry, and the viscosity of the slurry was controlled to be 12 Pa·s.

[0068] (3) Place 2000g of the carrier in a rotating drum at a speed of 10rpm; add the slurry prepared above to the stirring tank of the liquid spraying system and stir; start the hot air blower, and allow hot air to penetrate 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 60mL / min; spray the catalytically active material emulsion onto the surface of the carrier magnetic ring through the nozzle and rapidly dry it with hot air. The carrier weight increases by 15.2wt% after spraying is completed, and is activated at 400°C for 4h to prepare Catalyst B.

[0069] Preparation Example 3

[0070] (1) Prepare a solution of 56.27 g of ammonium metavanadate, 131.46 g of oxalic acid, 5.21 g of cesium sulfate, 1.51 g of ammonium dihydrogen phosphate, 6.15 g of niobium oxalate, 220 g of formamide and 750 g of water.

[0071] (2) The solution, 663.24 g of titanium dioxide, and 11.15 g of antimony trioxide were poured into a ball mill, and an appropriate amount of vinyl acetate-ethylene copolymer emulsion was added. The mixture was ball milled for 4 h to form a uniform slurry, and the viscosity of the slurry was controlled to be 14 Pa·S.

[0072] (3) Place 2000 g of the carrier in a rotating drum at a speed of 10 rpm; add the slurry prepared above to the stirring tank of the liquid spraying system and stir; start the hot air blower, allowing hot air to penetrate 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 60 mL / min; spray the slurry onto the carrier surface through the nozzle and rapidly dry it with the hot air. The carrier weight increases by 16.6 wt% after spraying is completed, and then activate at 400°C for 4 h to prepare Catalyst C.

[0073] Preparation Example 4

[0074] (1) 62.33 g of ammonium metavanadate, 144.52 g of oxalic acid, 2.99 g of cesium sulfate, 3.87 g of ammonium dihydrogen phosphate, 3.67 g of niobium oxalate, 3.41 g of zirconium sulfate tetrahydrate, 220 g of formamide and 550 g of water were prepared into a solution.

[0075] (2) The solution, 663.24 g of titanium dioxide, and 16.65 g of antimony trioxide were poured into a ball mill, and an appropriate amount of vinyl acetate-ethylene copolymer emulsion was added. The mixture was ball milled for 4 h to form a uniform slurry, and the viscosity of the slurry was controlled to be 10 Pa·S.

[0076] (3) 2000 g of the carrier was placed in a rotating drum at a speed of 10 rpm. The slurry prepared above was added to the stirring tank of the liquid spraying system and stirred. The hot air blower was turned on to allow hot air to enter the drum to preheat the carrier. When the carrier temperature reached 130°C, the feed nozzle was turned on and the hot air temperature was controlled to 100°C. The liquid spraying rate was 60 mL / min. The slurry was sprayed onto the carrier surface through the nozzle and rapidly dried by the hot air. The carrier weight increased by 16.7 wt% after spraying was completed. The catalyst was activated at 400°C for 4 h to prepare Catalyst D.

[0077] Preparation Example 5

[0078] (1) 78.56 g of ammonium metavanadate, 182.45 g of oxalic acid, 0.36 g of cesium sulfate, 4.93 g of ammonium dihydrogen phosphate, 6.84 g of niobium oxalate, 4.19 g of zirconium sulfate tetrahydrate, 220 g of formamide and 2200 g of water were prepared into a solution.

[0079] (2) The solution, 663.24 g of titanium dioxide, and 2.44 g of antimony trioxide were poured into a ball mill, and an appropriate amount of vinyl acetate-ethylene copolymer emulsion was added. The mixture was ball milled for 4 h to form a uniform slurry, and the viscosity of the slurry was controlled to be 30 Pa·S.

[0080] (3) 2000 g of the carrier was placed in a rotating drum at a speed of 10 rpm. The slurry prepared above was added to the stirring tank of the liquid spraying system and stirred. The hot air blower was turned on to allow hot air to enter the drum to preheat the carrier. When the carrier temperature reached 130°C, the feed nozzle was turned on and the hot air temperature was controlled to 100°C. The liquid spraying rate was 60 mL / min. The slurry was sprayed onto the carrier surface through the nozzle and rapidly dried by the hot air. The carrier weight increased by 17.5 wt% after spraying was completed. The catalyst was activated at 400°C for 4 h to prepare Catalyst E.

[0081] Preparation Example 6

[0082] A catalyst was prepared according to the method of Preparation Example 1, except that the amounts of ammonium metavanadate, oxalic acid, cesium sulfate, niobium oxalate, silver oxide, and antimony trioxide were 65.37 g, 167.66 g, 5.25 g, 6.15 g, 0.99 g, and 12.6 g, respectively. The carrier weight gain upon spraying was 14.3 wt%. The resulting catalyst was designated A1.

[0083] Preparation Example 7

[0084] A catalyst was prepared according to the method of Preparation Example 2, except that the amounts of ammonium metavanadate, oxalic acid, cesium sulfate, niobium oxalate, silver oxide, and antimony trioxide were 61.75 g, 135.96 g, 5.09 g, 5.99 g, 0.89 g, and 11.89 g, respectively. Upon completion of spraying, the carrier gained 15.5 wt%. The resulting catalyst was designated B1.

[0085] Preparation Example 8

[0086] A catalyst was prepared according to the method of Preparation Example 3, except that the amounts of ammonium metavanadate, oxalic acid, cesium sulfate, ammonium dihydrogen phosphate, niobium oxalate, and antimony trioxide were 64.56 g, 148.57 g, 5.46 g, 1.78 g, 6.45 g, and 11.98 g, respectively. Upon completion of spraying, the carrier gained 16.3 wt%. The resulting catalyst was designated C1.

[0087] Preparation Example 9

[0088] A catalyst was prepared according to the method of Preparation Example 4, except that the amounts of ammonium metavanadate, oxalic acid, cesium sulfate, ammonium dihydrogen phosphate, niobium oxalate, zirconium sulfate tetrahydrate, and antimony trioxide were 72.33 g, 172.32 g, 3.78 g, 4.12 g, 3.89 g, and 3.65 g, respectively. Upon completion of spraying, the carrier had a weight gain of 16.9 wt%. The resulting catalyst was designated D1.

[0089] Preparation Example 10

[0090] A catalyst was prepared according to the method of Preparation Example 5, except that the amounts of ammonium metavanadate, oxalic acid, cesium sulfate, ammonium dihydrogen phosphate, niobium oxalate, zirconium sulfate tetrahydrate, and antimony trioxide were 91.22 g, 204.52 g, 0.42 g, 5.28 g, 7.61 g, 4.67 g, and 2.68 g, respectively. Upon completion of spraying, the carrier had a weight gain of 17 wt%. The resulting catalyst was designated E1.

[0091] Test Case

[0092] The catalyst obtained in the above preparation example was characterized for the content of each active component. The weight content of each active component in the catalyst prepared above was analyzed by XPS. The percentage of the oxide of each active component in the catalyst relative to the total weight of the catalyst's active components is shown in Table 1.

[0093] Table 1

[0094]

[0095] Example 1

[0096] A fixed-bed single-tube reactor simulating industrial production conditions was used to load the catalyst. The inner diameter of the fixed-bed single-tube reactor was 29 mm, the tube length was 4400 mm, and the loading height was 3400 mm. In the direction of raw material flow, the catalyst bed was divided into the first reaction zone, the second reaction zone, the third reaction zone, the fourth reaction zone, and the fifth reaction zone. The first reaction zone to the fifth reaction zone were loaded with catalyst A, catalyst B, catalyst C, catalyst D, and catalyst E, respectively. The loading lengths from the first reaction zone to the fifth reaction zone were 300 mm, 1100 mm, 700 mm, 800 mm, and 500 mm, respectively.

[0097] Example 2

[0098] The catalyst was loaded according to the method of Example 1, except that the loading lengths from the first reaction zone to the fifth reaction zone were 800 mm, 600 mm, 700 mm, 800 mm, and 500 mm, respectively.

[0099] Example 3

[0100] The catalyst was loaded according to the method of Example 1, except that the loading lengths from the first reaction zone to the fifth reaction zone were 800 mm, 600 mm, 500 mm, 1000 mm, and 500 mm, respectively.

[0101] Example 4

[0102] The catalysts were loaded according to the method of Example 1, except that the first reaction zone to the fifth reaction zone were loaded with catalyst A1, catalyst B1, catalyst C1, catalyst D1 and catalyst E1 in sequence.

[0103] Example 5

[0104] The catalyst was loaded according to the method of Example 4, except that the loading lengths from the first reaction zone to the fifth reaction zone were 800 mm, 600 mm, 700 mm, 800 mm, and 500 mm, respectively.

[0105] Example 6

[0106] The catalyst was loaded according to the method of Example 1, except that the loading lengths from the first reaction zone to the fifth reaction zone were 1000 mm, 500 mm, 300 mm, 1100 mm, and 500 mm, respectively.

[0107] Comparative Example 1

[0108] A fixed-bed single-tube reactor simulating industrial production conditions was used for loading the catalyst. The inner diameter of the fixed-bed single-tube reactor was 29 mm, the tube length was 4400 mm, and the loading height was 3400 mm. In the direction of raw material flow, the catalyst bed was divided into the first reaction zone, the second reaction zone, the third reaction zone, and the fourth reaction zone. The first reaction zone to the fourth reaction zone were loaded with catalyst B, catalyst C, catalyst D, and catalyst E in sequence. The loading lengths from the first reaction zone to the fourth reaction zone were 1400 mm, 700 mm, 800 mm, and 500 mm, respectively.

[0109] Comparative Example 2

[0110] The catalyst was loaded according to the method of Comparative Example 1, except that the first reaction zone to the fourth reaction zone were loaded with catalyst B1, catalyst C1, catalyst D1 and catalyst E1 in sequence, and the loading lengths from the first reaction zone to the fourth reaction zone were 1400 mm, 700 mm, 800 mm and 500 mm, respectively.

[0111] Comparative Example 3

[0112] The catalysts were loaded according to the method of Example 1, except that the order of catalyst A and catalyst B was swapped, that is, the catalysts were loaded in the order of increasing catalyst activity.

[0113] Test Example 2

[0114] The reaction gas was introduced into the fixed bed single tube reactor loaded with the catalyst of the above examples and comparative examples for evaluation. The evaluation conditions included: pressure of 0.01 MPa, air volume space velocity of 3000 h -1 The evaluation results are shown in Table 2.

[0115] Table 2

[0116]

[0117] The results in Table 2 show that the method of the present invention can improve the yield of phthalic anhydride. In particular, the methods of Examples 1-3 can achieve a higher yield of phthalic anhydride.

[0118] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A reactor filled with a catalyst, characterized in that The reactor comprises at least three catalyst beds arranged in sequence, wherein the vanadium content of the catalyst in the second and subsequent catalyst beds increases successively, and the vanadium content of the catalyst in the first catalyst bed is between the vanadium content of the catalyst in the second catalyst bed and the last catalyst bed.

2. The reactor according to claim 1, wherein The reactor comprises 3 to 10 catalyst beds.

3. The reactor according to claim 1, wherein The catalysts in the catalyst bed each independently include a carrier and an active component supported on the carrier, and the active component includes V2O5 and TiO2.

4. The reactor according to claim 3, wherein The reactor comprises five catalyst beds, wherein: The molar ratio of V2O5 to TiO2 in the catalyst in the first catalyst bed is 0.028-0.034:

1. The molar ratio of V2O5 to TiO2 in the catalyst in the second catalyst bed is 0.026-0.032:

1. The molar ratio of V2O5 to TiO2 in the catalyst in the third catalyst bed is 0.029-0.033:

1. The molar ratio of V2O5 to TiO2 in the catalyst in the fourth catalyst bed is 0.032-0.037:

1. The molar ratio of V2O5 to TiO2 in the catalyst in the fifth catalyst bed is 0.04-0.047:

1.

5. The reactor according to claim 3, wherein The height ratio of the first catalyst bed, the second catalyst bed, the third catalyst bed, the fourth catalyst bed and the fifth catalyst bed is (0.5-2):(1-2.3):(0.6-1.5):(1.5-2.2):

1.

6. The reactor according to any one of claims 1 to 5, wherein The preparation method of the catalyst in each catalyst bed layer independently comprises: contacting a slurry containing a vanadium source, a titanium source and an optional auxiliary agent with a carrier, and then drying and activating the contact product to obtain the catalyst.

7. The reactor according to claim 6, wherein The carrier is at least one of talc, silicon carbide, aluminum silicate, quartz and ceramics; And / or, the titanium source is titanium dioxide and / or metatitanic acid; And / or, the vanadium source is ammonium metavanadate and / or vanadium pentoxide; And / or, the additive contains at least one element selected from phosphorus, cesium, niobium, silver, antimony, zirconium, rubidium, cerium, chromium, tungsten, cobalt, gallium, indium, bismuth and erbium.

8. Use of the reactor described in any one of claims 1 to 7 in the preparation of phthalic anhydride.

9. A method for preparing phthalic anhydride, characterized in that: The method comprises introducing naphthalene and oxygen into the reactor according to any one of claims 1 to 7 and sequentially contacting the catalysts in the first and subsequent catalyst beds to react.

10. The method according to claim 9, wherein: The reaction conditions include: temperature of 300-450°C, pressure of 0-0.1 MPa, oxygen volume space velocity of 300-1000 h -1 , the concentration of naphthalene is 70-85g / Nm 3 .

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