Ammonia oxidation catalyst, preparation method and application thereof, and method for preparing isophthalonitrile

Abstract

The invention relates to the field of catalysts, and discloses an ammoxidation catalyst, a preparation method and application thereof, and a method for preparing isophthalonitrile. The catalyst comprises a carrier and an active component, the active component comprises a vanadium-cerium composite oxide composed of a CeVO4 crystal phase; wherein in XPS element analysis on the surface of the catalyst, Ce < 4 + > and Ce < 3 + > are contained, and the mole number of the Ce < 3 + > is not lower than that of the Ce < 4 + >. The catalyst disclosed by the invention has excellent catalytic activity and high target product selectivity when being used in ammoxidation reaction.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to an ammonia oxidation catalyst, its preparation method and application, and a method for preparing isophthalonitrile. Background Technology

[0002] Due to the high reactivity of their cyano groups, aromatic nitriles can be prepared into a variety of organic chemical intermediates through a series of reactions such as addition, hydrolysis, and polymerization, giving them a crucial position in the fine chemical industry. Isophthalonitrile is the aromatic nitrile product with the largest market demand. It can be chlorinated to produce chlorothalonil for pesticide production; it can also be hydrogenated to obtain m-phenylenediamine, which is subsequently used to produce specialty nylon MXD6, etc.

[0003] Aromatic nitriles can be prepared by chemical methods and ammoxidation. Compared with chemical synthesis, gas-phase ammoxidation has advantages such as low cost, atom economy, short steps, high product quality, and environmental friendliness, making it the main production process for synthesizing aromatic nitrile compounds. However, this process requires high-performance catalysts. Studies have shown that vanadium oxide is very effective for the ammoxidation of aromatics; however, using vanadium oxide as a single-component catalyst results in an overly vigorous reaction, poor selectivity, and low yield of isophthalonitrile. Adding modifying elements is the main method to further improve the reaction performance of vanadium-based catalysts. Current reports in the field of m-xylene gas-phase ammonia oxidation mainly include V-Cr, VP, and Sb-Fe systems. Among these systems, the relatively low solubility of Sb salts leads to complex preparation processes and difficulties in preparing catalyst spray slurries, resulting in high catalyst preparation costs and hindering industrial application. The VP system, due to the complexity of the VP phase, has a very complicated catalyst preparation process with many influencing factors. Furthermore, the phosphorus component significantly affects the catalyst particle strength, reducing the wear resistance of fine-particle catalysts in fluidized beds. In addition, phosphorus is easily lost during the reaction, resulting in poor stability of VP catalysts, limiting industrial applications. The V-Cr system is relatively easy to prepare and has good reaction performance, but the two-component system still has shortcomings in target product selectivity and catalyst strength, especially the unsatisfactory selectivity, which easily leads to deep oxidation to CO. x And HCN, which affects the economics of the product, is therefore still not suitable for industrial production.

[0004] In the 1980s, Mitsubishi Gas Industries of Japan introduced V-Cr-B-Mo and V-Cr-BP system catalysts, followed by a V-Cr-BP-Mo five-component catalyst (EP0525367A1) in the 1990s, which improved reaction selectivity and increased isophthalonitrile yield. However, this required the use of phosphomolybdic acid as a raw material, resulting in high catalyst preparation costs. BASF reported K, Fe, and W modified V-Sb system fixed-bed catalysts. Due to the strong exothermic effect of the ammonia oxidation reaction itself, large-scale production using fixed beds carries certain risks, leading to a very low market share for this process. The Shanghai Petrochemical Research Institute developed a multi-element modified fluidized bed catalyst based on the V-Cr system, achieving a molar yield of approximately 80.76% for isophthalonitrile. However, Cr is a heavy metal component that causes significant environmental pollution in V-Cr system fluidized bed catalysts. Under today's increasingly stringent environmental protection requirements, catalyst production and waste catalyst disposal face significant limitations, thus requiring further catalyst improvements.

[0005] CN114471645A reports an environmentally friendly V-Ce system catalyst using Ce instead of Cr. However, due to the strong oxidizing properties of Ce, the catalyst has high activity, but the selectivity and yield of isophthalonitrile are low. Therefore, the V-Ce system catalyst needs further improvement. Summary of the Invention

[0006] The purpose of this invention is to overcome the problems of low target product yield due to low activity of existing ammonia oxidation catalysts or low target product selectivity due to high activity of catalysts, and to provide a new ammonia oxidation catalyst. At the same time, the invention also provides a method for preparing the catalyst, its application, and a method for preparing isophthalonitrile.

[0007] To achieve the above objectives, a first aspect of the present invention provides an ammonia oxidation catalyst, comprising a support and an active component; the active component comprises a vanadium-cerium composite oxide containing a CeVO4 crystal phase; wherein, XPS elemental analysis of the catalyst surface shows the presence of Ce. 4+ With Ce 3+ And Ce 3+ The number of moles is not less than Ce 4+ The number of moles.

[0008] A second aspect of the present invention provides a method for preparing the ammonia oxidation catalyst of the present invention, the method comprising:

[0009] (1) The solution L3 containing cerium source is brought into first contact with the solution L1 containing vanadium source and reducing agent to obtain solution L4;

[0010] (2) Optionally, solution L4 is brought into a second contact with solution L2 containing an auxiliary agent source, and then into a third contact with a carrier precursor. Optionally, it is then concentrated and finally dried and calcined.

[0011] The calcination is carried out in an inert atmosphere.

[0012] A third aspect of the present invention provides the application of the ammonia oxidation catalyst described herein in the preparation of aromatic nitrile.

[0013] A fourth aspect of the present invention provides a method for preparing isophthalonitrile. The method includes: in the presence of the ammonia oxidation catalyst described in the present invention, m-xylene, an ammonia source and an oxygen-containing gas undergo an ammonia oxidation reaction.

[0014] Through the above technical solution, the main active phase of the ammonia oxidation catalyst in this invention is CeVO4 crystal phase, and the catalyst surface contains Ce. 3+ Ce 4+ And Ce on the catalyst surface 3+ More than Ce 4+ It can significantly improve the catalytic activity of ammonia oxidation catalysts and the selectivity of target products when used in ammonia oxidation reactions. Attached Figure Description

[0015] Figure 1 This is the XPS image of catalyst I for ammonia oxidation in Example 9;

[0016] Figure 2 This is the XPS image of the ammonia oxidation catalyst DA1 in Example 2;

[0017] Figure 3 This is the XRD pattern of ammonia oxidation catalyst I in Example 9. Detailed Implementation

[0018] The endpoints and any values ​​of the ranges 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 endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0019] The first aspect of this invention provides an ammonia oxidation catalyst, comprising a support and an active component; the active component comprises a vanadium-cerium composite oxide containing a CeVO4 crystal phase; wherein, XPS elemental analysis of the catalyst surface shows the presence of Ce. 4 + With Ce 3+ And Ce 3+ The number of moles is not less than Ce 4+ The number of moles.

[0020] In this invention, "ammonia oxidation catalyst" refers to a catalyst that is particularly suitable for ammonia oxidation reactions. The main active phase of the ammonia oxidation catalyst in this invention is the CeVO4 crystalline phase, and the active phase is controlled by the Ce on the catalyst surface. 3+ The number of moles is not less than Ce 4+ The molar number can significantly improve the catalytic activity of the catalyst and its selectivity for the target product when used in ammonia oxidation.

[0021] In this invention, the crystal structure of the catalyst was determined by X-ray diffraction (XRD) using a Bruker D8 X-ray powder diffractometer (XRD) from Germany, with a Cu-Kα ray source and a Kα1 wavelength λ = 1.5405980 angstroms. Nickel filter, operating voltage 40kV, current 40mA, scanning range 2θ=5~80°.

[0022] According to a preferred embodiment of the present invention, in the XPS elemental analysis of the catalyst surface, Ce 4+ With Ce 3+ The molar ratio is 0.2-0.8:1, for example, 0.2:1, 0.23:1, 0.24:1, 0.25:1, 0.28:1, 0.3:1, 0.4:1, 0.5:1, 0.55:1, 0.6:1, 0.7:1, 0.8:1, or any range of two of the above ratios. The ammonia oxidation catalyst under the aforementioned embodiments exhibits better catalytic activity and selectivity for the target product.

[0023] According to a preferred embodiment of the present invention, in the XPS elemental analysis of the catalyst surface, Ce 4+ With Ce 3+ The molar ratio is 0.2-0.6:1. The ammonia oxidation catalysts described in the aforementioned embodiments exhibit better catalytic activity and selectivity for the target product.

[0024] In this invention, the distribution of active metals on the catalyst surface was analyzed using a Perkin Elmer phi5000c X-ray photoelectron spectroscopy (XPS) instrument with a Mg Kα X-ray source, a working voltage of 15 kV, and a current of 20 mA. All spectra were calibrated to a C1s value of 284.8 eV.

[0025] In some existing ammonia oxidation catalysts, Cr is often added as a promoter to increase the catalyst activity. Preferably, the catalyst of the present invention does not contain Cr. In the present invention, good catalytic activity and target product selectivity can be achieved without the use of the heavy metal Cr, and the environmental protection requirements for catalyst production and preparation are reduced, the cost of waste catalyst treatment is significantly reduced, and the environmental friendliness is significantly improved.

[0026] According to a preferred embodiment of the present invention, the active component further contains adjuvant elements, calculated by element.

[0027] In this invention, the auxiliary elements refer to elements other than Ce and V. As long as the purpose of this invention can be achieved, the specific types of auxiliary elements are not particularly limited. In one embodiment, the auxiliary elements include: element A, which is selected from phosphorus and / or boron.

[0028] In this invention, when element A contains both phosphorus and boron, the content of phosphorus and boron is not specifically limited. For example, their molar ratio can be 1:(1-5), such as 1:1, 1:2, 1:2.5, 1:4, or 1:5.

[0029] According to a preferred embodiment of the present invention, the auxiliary element includes element B, which is selected from at least one element selected from manganese, nickel, cobalt, titanium, tungsten, molybdenum, niobium, copper, and iron. The catalyst under the aforementioned embodiment exhibits good catalytic activity and, when used, shows better selectivity for the target product.

[0030] According to a preferred embodiment of the present invention, element B is selected from at least one element selected from manganese, molybdenum, niobium, and iron. The catalyst under the aforementioned embodiment exhibits good catalytic activity and, when used, shows better selectivity for the target product.

[0031] In this invention, when element B is composed of multiple different types of metallic elements, there are no special restrictions on the specific proportions of the various elements within element B.

[0032] According to the present invention, in one embodiment, element B is Mo, Mn and Fe, preferably in a molar ratio of (1-3):(2-7):(0.05-1); in some embodiments of the present invention, embodiments in which B is Mo, Mn and Fe in a molar ratio of 2:6:1 are provided as non-limiting descriptions and should not be construed as limiting the present application.

[0033] According to the present invention, in one embodiment, element B is Mo and Mn, preferably in a molar ratio of (0.5-4):1; in some embodiments of the present invention, embodiments in which B is Mo and Mn in a molar ratio of 2:1 are provided as non-limiting descriptions and should not be construed as limiting the present application.

[0034] According to a preferred embodiment of the present invention, element B comprises at least niobium, and at least one element selected from manganese, molybdenum and iron.

[0035] According to the present invention, in one embodiment, element B is Mn, Mo, Nb and Fe, preferably in a molar ratio of (1-3):(2-7):(0.05-1):(0.05-1). In some embodiments of the present invention, embodiments in which B is Mn, Mo, Nb and Fe in a molar ratio of 2:5:0.1:0.1 or 2:3:1:1 are described as non-limiting and should not be construed as limiting the present application.

[0036] According to a preferred embodiment of the present invention, the adjuvant element includes: element C, wherein element C is selected from at least one element in groups IA and / or IIA.

[0037] According to a preferred embodiment of the present invention, element C is selected from at least one element selected from lithium, sodium, potassium, rubidium, calcium, and strontium. In the embodiments of the present invention, potassium is used as an example to illustrate the advantages of the present invention, but it should not be construed as a limitation of the present invention.

[0038] According to a preferred embodiment of the present invention, the molecular formula of the active component in atomic ratio is shown in formula (1):

[0039] V 1.0 Ce a A b B c C d O x Equation (1),

[0040] In equation (1): V is vanadium, Ce is cerium, the value of a ranges from 0.6 to 2.5, the value of b ranges from 0.2 to 1.2, the value of c ranges from 0.01 to 0.5, the value of d ranges from 0 to 0.5, and x is the number of oxygen atoms required to satisfy the oxidation state of each element in equation (1).

[0041] In this invention, the content of each element in the active component and the carrier are calculated according to the feeding ratio.

[0042] In this invention, the value of d ranges from 0 to 0.5, indicating whether the auxiliary agent C is present or not.

[0043] According to the present invention, in formula (1), the values ​​of a can be listed as 0.6, 0.8, 1.0, 1.5, 2.0, 2.5, and any two of the above values ​​are in the range. Preferably, the value range of a is 0.6-1.0.

[0044] According to the present invention, in formula (1), the values ​​of b can be listed as 0.2, 0.4, 0.5, 0.75, 0.8, 1.0, 1.2, or any two of the above values. Preferably, the value range of b is 0.4-0.8.

[0045] According to the present invention, in formula (1), the values ​​of c can be 0.01, 0.05, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.5, or any two of the above values, preferably 0.01-0.15.

[0046] According to the present invention, in formula (1): when d is 0, it means that there is no C element. The possible values ​​of d are 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.08, 0.1, 0.2, 0.3, 0.4, 0.5, or any two of the above values, preferably 0-0.2.

[0047] According to a preferred embodiment of the present invention, in the catalyst, CeVO4 accounts for 70%-98% of the active component by mass, for example, 70%, 72%, 80%, 85%, 92%, 95%, 96%, 98%, or any two of the above values, preferably 85%-95%.

[0048] In this invention, those skilled in the art can use methods well known in the art to test the mass of CeVO4 in the active component of the catalyst, such as loading different masses of pure cerium vanadate onto a support, performing XRD characterization, creating a standard curve, and comparing it with the catalyst XRD to determine the amount of cerium vanadate in the catalyst.

[0049] According to the present invention, the content of the active component in the catalyst is not particularly limited as long as the purpose of the present invention can be achieved. Preferably, the mass ratio of the active component to the support in the catalyst is (0.6-1.6):1, for example, 0.6:1, 0.7:1, 0.8:1, 1:1, 1.05:1, 1.2:1, 1.4:1, 1.6:1, or any range of two of the above ratios, preferably (0.8-1.2):1.

[0050] According to the present invention, the specific type of support is not particularly limited as long as the purpose of the present invention can be achieved. Preferably, the support is selected from at least one of SiO2, Al2O3, TiO2, ZrO2, MgO and molecular sieve, and preferably SiO2.

[0051] According to the present invention, the median particle size of the catalyst can be any median particle size of existing catalysts. As a preferred embodiment without limitation, the median particle size of the catalyst is 45 μm-55 μm.

[0052] According to the present invention, the overall particle size distribution of the catalyst is generally within a certain range. The overall particle size range of the catalyst described in the present invention can be any particle size range of existing catalysts. As a preferred embodiment without limitation, the overall particle size range of the catalyst is 1μm-120μm.

[0053] The catalyst of this invention has excellent strength, and as a preferred embodiment (not limiting), the catalyst wear rate is no higher than 1.1 wt%.

[0054] The abrasion rate was tested using a method conforming to ASTM D5757-00 (Determining the relative abrasion characteristics of powdered catalysts by air jet abrasion method). The abrasion rate of the finished catalyst was measured as the abrasion rate per hour, expressed in wt%.

[0055] According to the present invention, the preparation method of the ammonia oxidation catalyst of the present invention is not particularly limited as long as the purpose of the present invention can be achieved. Preferably, the second aspect of the present invention provides a preparation method of the ammonia oxidation catalyst of the present invention, the preparation method comprising:

[0056] (1) The solution L3 containing cerium source is brought into first contact with the solution L1 containing vanadium source and reducing agent to obtain solution L4;

[0057] (2) Optionally, solution L4 is brought into a second contact with solution L2 containing an auxiliary agent source, and then into a third contact with a carrier precursor. Optionally, it is then concentrated and finally dried and calcined.

[0058] The calcination is carried out in an inert atmosphere.

[0059] In this invention, the order of addition of each component is strictly controlled during the preparation process, and the catalyst obtained by calcination under an inert gas atmosphere can improve its surface Ce content. 3+ The content of Ce on the catalyst surface 3+ More than Ce 4+ When used, it can significantly improve the catalytic activity of the catalyst and the selectivity of the target product during use.

[0060] According to the present invention, the inert gas refers to a gas that does not chemically react with metal compounds. In some preferred embodiments, the inert atmosphere is selected from at least one of carbon dioxide, group zero gases, and nitrogen.

[0061] According to a preferred embodiment of the present invention, the inert atmosphere is selected from carbon dioxide, as well as group zero gases and / or nitrogen. The catalyst prepared by the foregoing embodiments exhibits better catalytic activity and target product selectivity.

[0062] According to the present invention, as long as the purpose of the present invention can be achieved, there are no particular restrictions on the amount of carbon dioxide used in the preparation of the catalyst, and the amount of group zero gas and / or nitrogen is not limited. Preferably, the volume ratio of carbon dioxide to group zero gas and / or nitrogen is 1-3:10.

[0063] According to a preferred embodiment of the present invention, the calcination is carried out at least at 450-750°C, preferably at 500-600°C.

[0064] According to a preferred embodiment of the present invention, the total roasting time is 7-28 hours, preferably 12-21 hours.

[0065] According to a more preferred embodiment of the present invention, the roasting is a two-stage roasting, wherein the temperature of the first stage roasting is lower than the temperature of the second stage roasting.

[0066] According to a more preferred embodiment of the present invention, the conditions for the first stage of roasting include: a temperature of 150-220°C, preferably 180-200°C; and a time of 2-8 hours, preferably 4-6 hours.

[0067] According to a more preferred embodiment of the present invention, the conditions for the second stage of roasting include: a temperature of 450-750°C, preferably 500-600°C; and a time of 5-20 hours, preferably 8-15 hours.

[0068] According to the present invention, optional concentration means that those skilled in the art may or may not concentrate as needed. For example, when the solvent content in the material obtained by the third contact with the carrier precursor is higher than 65 wt%, concentration (e.g., thermal concentration) may be carried out to concentrate it into a viscous slurry of 30 wt%-65 wt% in order to facilitate subsequent drying.

[0069] According to the present invention, the drying method is not particularly limited as long as it achieves the purpose of the invention. Preferably, the drying method is spray molding. The catalyst prepared by spray molding in the present invention has high particle strength.

[0070] According to a preferred embodiment of the present invention, the conditions for spray drying include: a gas inlet temperature of 250-350°C for the spray dryer.

[0071] According to a preferred embodiment of the present invention, the conditions for spray drying include an outlet temperature of 120-180°C.

[0072] According to a preferred embodiment of the present invention, the conditions for spray drying include a rotation speed of 3000-6000 r / min.

[0073] According to the present invention, there are no special restrictions on the conditions of the first contact, the second contact and the third contact, as long as the components are thoroughly mixed.

[0074] According to the present invention, there is no special limitation on the specific type of cerium source as long as the purpose of the present invention can be achieved, as long as cerium ions can be provided. Preferably, the cerium source is selected from nitrates and / or ammonium nitrates corresponding to the element cerium. Examples of cerium sources include Ce(NO3)3·6H2O, Ce(NH4)2(NO3)6, etc.

[0075] According to the present invention, the specific type of vanadium source is not particularly limited as long as the purpose of the present invention can be achieved, as long as vanadium element can be provided. Preferably, the vanadium source is selected from at least one of the oxides, ammonium salts, sulfates, oxalates and tartrates corresponding to vanadium element. Examples of vanadium sources include V2O5, NH4VO3, vanadium sulfate, vanadium oxalate, vanadium tartrate, etc.

[0076] According to a preferred embodiment of the present invention, the auxiliary agent source includes a precursor A, a precursor B, and optionally a precursor C, wherein the precursor A is selected from at least one of the acids, ammonium salts, and oxides corresponding to each of elements P and / or B; the precursor B is selected from at least one of the acids, ammonium salts, oxides, and nitrates corresponding to each of at least one of elements Mn, Ni, Co, Ti, W, Mo, Nb, Cu, and Fe; and the precursor C is selected from the nitrates corresponding to at least one element in Group IA and / or IIA.

[0077] According to the present invention, the type of reducing agent is not particularly limited as long as the purpose of the present invention can be achieved, and preferably the reducing agent is selected from at least one of oxalic acid, formic acid, citric acid and hydroxylamine hydrochloride.

[0078] According to a preferred embodiment of the present invention, the molar ratio of the reducing agent to vanadium is 0.5-1.5:1, preferably 0.8-1.3.

[0079] According to the present invention, there is no particular limitation on the specific type of carrier precursor, as long as a corresponding carrier can be provided, such as one or more of silica sol, water glass, pseudoboehmite, aluminosilicate sol, TiO2, ZrO2, MgO and molecular sieve, preferably silica sol.

[0080] In this invention, silica sol refers to a dispersion of nano-sized silica particles in water, such as silica sol with a silica content of 35-50 wt%.

[0081] According to the present invention, the solution L3 containing cerium source, the solution L1 containing vanadium source and reducing agent, and the solution L2 containing auxiliary agent source refer to the corresponding solute being dispersed or dissolved in the corresponding solvent, which is generally water.

[0082] According to the present invention, the content of cerium source in solution L3 is not particularly limited, for example, the mass content of cerium source in solution L3 is 40-70 wt%.

[0083] According to the present invention, in the solution L1 containing vanadium source and reducing agent, the content of vanadium source and reducing agent is not particularly limited. For example, in solution L1, the mass content of vanadium source is 10-30 wt%.

[0084] According to the present invention, the content of the auxiliary agent source in the solution L2 containing the auxiliary agent source is not particularly limited, for example, the mass content of the auxiliary agent source in the solution L2 is 8-20 wt%.

[0085] According to the present invention, when the adjuvant sources are of different types, solutions containing different adjuvant sources can be prepared separately and then mixed, or different types of adjuvant sources can be added to the solvent in sequence to prepare corresponding solutions L2.

[0086] A third aspect of the present invention provides the application of the ammonia oxidation catalyst described herein in the preparation of aromatic nitrile.

[0087] In this invention, the ammonia oxidation catalyst of this invention is used to catalytically prepare aromatic nitrile, which has excellent catalytic activity and selectivity for aromatic nitrile.

[0088] A fourth aspect of the present invention provides a method for preparing isophthalonitrile. The method includes: in the presence of the ammonia oxidation catalyst described in the present invention, m-xylene, an ammonia source and an oxygen-containing gas undergo an ammonia oxidation reaction.

[0089] The ammonia oxidation catalyst of this invention is used in the gas-phase ammonia oxidation of m-xylene to produce isophthalonitrile, and has achieved a high yield of isophthalonitrile, thus achieving good technical results.

[0090] According to a preferred embodiment of the present invention, the ammonia source is NH3, and the molar ratio of the m-xylene to the ammonia source is 1:5-12.

[0091] According to the present invention, under normal circumstances, a low oxygen ratio will lead to a decrease in reaction conversion rate and an increase in the selectivity of m-methylbenzonitrile, while a high oxygen ratio will lead to deep oxidation. In a preferred embodiment, the oxygen-containing gas is oxygen, and the molar ratio of m-xylene to the oxygen-containing gas is 1:2-10.

[0092] According to a preferred embodiment of the present invention, the oxygen-containing component is selected from air and / or oxygen.

[0093] In a preferred embodiment of the present invention, the ammonia source is selected from ammonia gas.

[0094] According to a preferred embodiment of the present invention, the ammonia oxidation reaction is carried out in a fluidized bed reactor.

[0095] In this invention, the ammonia oxidation reaction can be applied in a conventional fluidized bed reactor. It is only necessary to ensure the quality of fluidization and avoid the generation of abnormal fluidization phenomena such as channeling, bubbles, and surging. At the same time, the degree of backmixing of the gas flow should be reduced. Moreover, the ammonia oxidation reaction in the fluidized bed reactor can avoid the problems of needing a large number of complex heat removal devices in the fixed bed reaction system. The equipment is highly safe, the product is easy to separate, the operation is simple, and the operating cost is significantly advantageous.

[0096] According to the present invention, the conversion rate of m-xylene is relatively low and the selectivity of the intermediate m-methylbenzonitrile is relatively high when the ammonia oxidation reaction is carried out at lower temperatures; while at higher reaction temperatures, the conversion rate of m-xylene increases, the degree of oxidation deepens, and CO is generated. x In addition to HCN and demethylation products, preferably, the conditions for the ammonia oxidation reaction include a reaction temperature of 350-430°C.

[0097] According to the present invention, the ammonia oxidation reaction system can be at atmospheric pressure or under pressure. Preferably, the conditions for the ammonia oxidation reaction include a reaction pressure of 101-120 kPa.

[0098] According to a preferred embodiment of the present invention, the conditions for the ammonia oxidation reaction include: a catalyst loading of 0.04-0.08 h. -1 .

[0099] The present invention will be described in detail below through embodiments. In the following embodiments and comparative examples:

[0100] All raw materials are commercially available products;

[0101] The catalyst evaluation was conducted using a fluidized bed reactor with a diameter of φ=40mm and a length of 1800mm, with a catalyst loading of 550g.

[0102] The conversion rate of m-xylene, the selectivity of isophthalonitrile, and the yield of isophthalonitrile are defined as follows:

[0103]

[0104]

[0105]

[0106] Example 1

[0107] Preparation of ammonia oxidation catalyst A:

[0108] 140g of V2O5 was added to 600ml of an aqueous solution containing 141g of oxalic acid monohydrate, and the mixture was stirred thoroughly to obtain a blue solution L1.

[0109] Solution L2 was prepared by mixing 48g boric acid with 250g water, 15g ammonium molybdate with 100g water, 4.7g potassium nitrate with 8g water, 8.28g niobium oxalate with 100g water, 5.5g manganese nitrate with 50g water, 3.72g ferric nitrate with 50g water, and 0.38mol phosphoric acid.

[0110] Dissolve 534g of cerium nitrate hexahydrate in 800g of water and stir rapidly until completely dissolved to obtain solution L3;

[0111] Solution L3 was quickly added to solution L1 and stirred for 30 minutes to obtain solution L4;

[0112] Then add solution L2 to solution L4 and stir for 30 minutes to obtain solution L5;

[0113] Finally, solution L5 was slowly added to 1250g of silica sol with a SiO2 content of 40wt% under stirring to obtain a dark yellow mixture (mixed slurry L). Then, it was heated and concentrated under stirring to obtain a viscous slurry with a solid content of 30wt%.

[0114] The above slurry was spray-dried and shaped. The inlet temperature of the spray dryer was 380℃, the outlet temperature was 175℃, and the centrifugal nozzle speed was 4500 r / min. The fine catalyst particles obtained by spraying were calcined at 600℃ under nitrogen atmosphere for 10 hours to obtain ammonia oxidation catalyst A, whose composition is V. 1.0 Ce 0.8 Mo 0.05 Mn 0.02 Fe 0.01 Nb 0.01 P 0.25 B 0.5 K 0.03 / SiO2.

[0115] The active component to support mass ratio in ammonia oxidation catalyst A is 1.05:1, and the median particle size of ammonia oxidation catalyst A is 50 μm. The CeVO4 crystalline phase accounts for 47 wt% of the weight of ammonia oxidation catalyst A, and the Ce on the surface of catalyst A... 4+ molar amount / Ce 3+ The molar amount is 0.25.

[0116] Performance evaluation of ammonia oxidation catalyst A:

[0117] Feed molar ratio of m-xylene:NH3:O2 = 1:10:7; catalyst loading 0.060 h⁻¹ -1 The reaction temperature was 405℃ and the reaction system pressure was 101kPa.

[0118] Reaction results: m-xylene conversion 99.2%; isophthalonitrile selectivity 82.5%; isophthalonitrile yield 81.8%; catalyst attrition rate 1.1%.

[0119] Example 2

[0120] Preparation of ammonia oxidation catalyst B:

[0121] The method of Example 1 was followed, except that the amounts of manganese nitrate (27.5g), ammonium molybdate (45g), niobium oxalate (41.4g), and ferric nitrate (18.6g) were controlled, while the rest remained the same as in Example 1. The final composition of the ammonia oxidation catalyst B was V. 1.0 Ce 0.8 Mo 0.15 Mn 0. 1Fe 0.05 Nb 0.05 P 0.25 B 0.5 K 0.03 / SiO2.

[0122] In the ammonia oxidation catalyst B, the mass ratio of active component to support is 1.1:1, and the median particle size of the ammonia oxidation catalyst B is 48 μm. The CeVO4 crystalline phase accounts for 45 wt% of the weight of the ammonia oxidation catalyst B, and the CeV4 crystalline phase on the surface of the ammonia oxidation catalyst B... 4+ molar amount / Ce 3+ The molar amount is 0.2.

[0123] Performance evaluation of ammonia oxidation catalyst B:

[0124] Feed molar ratio of m-xylene:NH3:O2 = 1:10:7; catalyst loading 0.060 h⁻¹ -1 The reaction temperature was 405℃ and the reaction system pressure was 101kPa.

[0125] Reaction results: m-xylene conversion rate 98.9%; isophthalonitrile selectivity 81.4%; isophthalonitrile yield 80.5%; catalyst attrition rate 1.08%.

[0126] Example 3

[0127] Preparation of ammonia oxidation catalyst C:

[0128] The method of Example 1 was followed, except that the phosphoric acid was controlled at 0.608 mol, boric acid at 76.8 g, and potassium nitrate at 31.3 g, while the rest was the same as in Example 1. The final composition of the ammonia oxidation catalyst C was V. 1.0 Ce 0.8 Mo 0.05 Mn 0.02 Fe 0.01 Nb 0.0 1P 0.4 B0.8 K 0.2 / SiO2.

[0129] The active component to support mass ratio in ammonia oxidation catalyst C is 1.06:1, and the median particle size of ammonia oxidation catalyst C is 49 μm. The CeVO4 crystalline phase accounts for 46 wt% of the weight of ammonia oxidation catalyst C, and the Ce crystalline phase on the surface of ammonia oxidation catalyst C... 4+ molar amount / Ce 3+ The molar amount is 0.4.

[0130] Performance evaluation of ammonia oxidation catalyst C:

[0131] Feed molar ratio of m-xylene:NH3:O2 = 1:10:7; catalyst loading 0.060 h⁻¹ -1 The reaction temperature was 405℃ and the reaction system pressure was 101kPa.

[0132] Reaction results: m-xylene conversion 98.5%; isophthalonitrile selectivity 81.9%; isophthalonitrile yield 80.7%; catalyst attrition rate 1.09%.

[0133] Example 4

[0134] Preparation of ammonia oxidation catalyst D:

[0135] The method is the same as in Example 1, except that the amount of silica sol with a SiO2 content of 40 wt% is 1640 g, and the rest is the same as in Example 1.

[0136] In the ammonia oxidation catalyst D, the mass ratio of active component to support is 0.8:1, and the median particle size of the ammonia oxidation catalyst D is 52 μm. The CeVO4 crystalline phase accounts for 40 wt% of the weight of the ammonia oxidation catalyst D, and the Ce crystalline phase on the surface of the ammonia oxidation catalyst D... 4+ molar amount / Ce 3+ The molar amount is 0.28.

[0137] Performance evaluation of ammonia oxidation catalyst D:

[0138] Feed molar ratio of m-xylene:NH3:O2 = 1:10:7; catalyst loading 0.060 h⁻¹ -1 The reaction temperature was 405℃ and the reaction system pressure was 101kPa.

[0139] Reaction results: m-xylene conversion 98.1%; isophthalonitrile selectivity 82.6%; isophthalonitrile yield 81.0%; catalyst attrition rate 1.08%.

[0140] Example 5

[0141] Preparation of ammonia oxidation catalyst E:

[0142] The method is the same as in Example 1, except that the order of adding materials in the preparation process is different. Specifically,

[0143] Solution L2 was rapidly added to L1 and stirred for 30 minutes to obtain solution L4; then solution L3 was added to L4 and stirred for 30 minutes to obtain solution L5; finally, solution L5 was added to the silica sol carrier and stirred thoroughly for 1 hour to obtain mixed slurry L.

[0144] In the ammonia oxidation catalyst E, the mass ratio of active component to support is 1.05:1, and the median particle size of the ammonia oxidation catalyst D is 51 μm. The CeVO4 crystalline phase accounts for 45 wt% of the weight of the ammonia oxidation catalyst D, and the Ce crystalline phase on the surface of the ammonia oxidation catalyst D... 4+ molar amount / Ce 3+ The molar amount is 0.5.

[0145] Performance evaluation of ammonia oxidation catalyst E:

[0146] Feed molar ratio of m-xylene:NH3:O2 = 1:10:7; catalyst loading 0.060 h⁻¹ -1 The reaction temperature was 405℃ and the reaction system pressure was 101kPa.

[0147] Reaction results: m-xylene conversion rate 99.3%; isophthalonitrile selectivity 80.7%; isophthalonitrile yield 80.1%; catalyst attrition rate 1.08%.

[0148] Example 6

[0149] Preparation of ammonia oxidation catalyst F:

[0150] The method of Example 1 differs in that:

[0151] Replace 8.28g of niobium oxalate with 3g of ammonium molybdate. Specifically, mix the following solutions: 48g of boric acid with 250g of water, 18g of ammonium molybdate with 100g of water, 4.7g of potassium nitrate with 8g of water, 5.5g of manganese nitrate with 50g of water, 3.72g of ferric nitrate with 50g of water, and 0.38mol of phosphoric acid to obtain solution L2.

[0152] The rest is the same as in Example 1, and the final ammonia oxidation catalyst F is obtained, with the composition V. 1.0 Ce 0.8 Mo 0.06 Mn 0.02 Fe 0.0 1P 0.25 B 0.5 K 0.03 / SiO2.

[0153] The active component to support mass ratio in ammonia oxidation catalyst F is 1.04:1, and the median particle size of ammonia oxidation catalyst F is 49 μm. CeVO4 crystalline phase accounts for 47 wt% of the weight of ammonia oxidation catalyst F, and Ce on the surface of ammonia oxidation catalyst F... 4+ molar amount / Ce 3+ The molar amount is 0.55.

[0154] Performance evaluation of ammonia oxidation catalyst F:

[0155] Feed molar ratio of m-xylene:NH3:O2 = 1:10:7; catalyst loading 0.060 h⁻¹ -1 The reaction temperature was 405℃ and the reaction system pressure was 101kPa.

[0156] Reaction results: m-xylene conversion rate 98.8%; isophthalonitrile selectivity 80.5%; isophthalonitrile yield 79.5%; catalyst attrition rate 1.09%.

[0157] Example 7

[0158] Preparation of ammonia oxidation catalyst G:

[0159] The method of Example 1 differs in that:

[0160] Replace 3.72g of ferric nitrate with 3g of ammonium molybdate. Specifically, mix the following solutions: 48g of boric acid with 250g of water, 18g of ammonium molybdate with 100g of water, 4.7g of potassium nitrate with 8g of water, 8.28g of niobium oxalate with 100g of water, 5.5g of manganese nitrate with 50g of water, and 0.38mol of phosphoric acid.

[0161] The rest is the same as in Example 1, and the final ammonia oxidation catalyst G is obtained, with a composition of V. 1.0 Ce 0.8 Mo 0.06 Mn 0.02 Nb 0.0 1P 0.25 B 0.5 K 0.03 / SiO2.

[0162] The active component to support mass ratio in ammonia oxidation catalyst G is 1.05:1, and the median particle size of ammonia oxidation catalyst G is 51 μm. The CeVO4 crystalline phase accounts for 47 wt% of the weight of ammonia oxidation catalyst G, and the Ce crystalline phase on the surface of ammonia oxidation catalyst G... 4+ molar amount / Ce 3+ The molar amount is 0.3.

[0163] Performance evaluation of ammonia oxidation catalyst G:

[0164] Feed molar ratio of m-xylene:NH3:O2 = 1:10:7; catalyst loading 0.060 h⁻¹ -1 The reaction temperature was 405℃ and the reaction system pressure was 101kPa.

[0165] Reaction results: m-xylene conversion rate 98.7%; isophthalonitrile selectivity 82.2%; isophthalonitrile yield 81.1%; catalyst attrition rate 1.09%.

[0166] Example 8

[0167] Preparation of ammonia oxidation catalyst H:

[0168] The method of Example 1 differs in that:

[0169] Replace 3.72g of ferric nitrate with 3g of ammonium molybdate, and replace 8.28g of niobium oxalate with 2.8g of manganese nitrate.

[0170] Specifically, solutions prepared by mixing 48g boric acid with 250g water, 18g ammonium molybdate with 100g water, 4.7g potassium nitrate with 8g water, 8.3g manganese nitrate with 50g water, and 0.38mol phosphoric acid were mixed to obtain solution L2.

[0171] The rest is the same as in Example 1, and the final ammonia oxidation catalyst H is obtained, with a composition of V. 1.0 Ce 0.8 Mo 0.06 Mn 0.03 P 0.2 5B 0.5 K 0.03 / SiO2.

[0172] In the ammonia oxidation catalyst H, the mass ratio of active component to support is 1.05:1, and the median particle size is 52 μm. The CeVO4 crystalline phase accounts for 47 wt% of the ammonia oxidation catalyst H, and the Ce crystalline phase on the surface of the ammonia oxidation catalyst H... 4+ molar amount / Ce 3+ The molar amount is 0.6.

[0173] Performance evaluation of ammonia oxidation catalyst H:

[0174] Feed molar ratio of m-xylene:NH3:O2 = 1:10:7; catalyst loading 0.060 h⁻¹ -1 The reaction temperature was 405℃ and the reaction system pressure was 101kPa.

[0175] Reaction results: m-xylene conversion 99.6%; isophthalonitrile selectivity 79.5%; isophthalonitrile yield 79.2%; catalyst attrition rate 1.1%.

[0176] Example 9

[0177] Preparation of ammonia oxidation catalyst I:

[0178] The method of Example 1 is followed, except that the calcination conditions are changed to: calcining at 180°C for 4 hours, then heating up and calcining at 500°C for 8 hours, and nitrogen is replaced with a mixture of carbon dioxide and nitrogen (volume ratio 1:10).

[0179] In ammonia oxidation catalyst I, the mass ratio of active component to support is 1.05:1, and the median particle size is 48 μm. The CeVO4 crystalline phase accounts for 47 wt% of the weight of ammonia oxidation catalyst I. The XPS spectrum of catalyst I is shown below. Figure 1 As shown, the XRD pattern is as follows Figure 3 As shown, Ce on the surface of ammonia oxidation catalyst I 4+ molar amount / Ce 3+ The molar amount is 0.23.

[0180] Performance evaluation of ammonia oxidation catalyst I:

[0181] Feed molar ratio of m-xylene:NH3:O2 = 1:10:7; catalyst loading 0.060 h⁻¹ -1 The reaction temperature was 405℃ and the reaction system pressure was 101kPa.

[0182] Reaction results: m-xylene conversion rate 99.3%; isophthalonitrile selectivity 83.5%; isophthalonitrile yield 82.9%; catalyst attrition rate 1.07%.

[0183] Example 10

[0184] Preparation of ammonia oxidation catalyst J:

[0185] The method of Example 1 is followed, except that the calcination conditions are changed to: calcining at a low temperature of 200°C for 6 hours, then heating up and calcining at 600°C for 15 hours, and nitrogen is replaced with a mixture of carbon dioxide and argon (volume ratio 3:10).

[0186] In the ammonia oxidation catalyst J, the mass ratio of active component to support is 1.05:1, and the median particle size of the ammonia oxidation catalyst J is 49 μm. The CeVO4 crystalline phase accounts for 47 wt% of the weight of the ammonia oxidation catalyst J, and the Ce crystalline phase on the surface of the ammonia oxidation catalyst J... 4+ molar amount / Ce 3+ The molar amount is 0.24.

[0187] Performance evaluation of ammonia oxidation catalyst J:

[0188] Feed molar ratio of m-xylene:NH3:O2 = 1:10:7; catalyst loading 0.060 h⁻¹ -1 The reaction temperature was 405℃ and the reaction system pressure was 101kPa.

[0189] Reaction results: m-xylene conversion rate 99.4%; isophthalonitrile selectivity 83.2%; isophthalonitrile yield 82.7%; catalyst attrition rate 1.08%.

[0190] Comparative Example 1

[0191] Preparation of ammonia oxidation catalyst DA1:

[0192] The method of Example 1 differs in that:

[0193] A solution prepared by mixing 48g boric acid with 250g water, a solution prepared by mixing 4.7g potassium nitrate with 8g water, and 0.38mol phosphoric acid were mixed to obtain solution L2. The solution was then calcined in air for 10 hours, with the rest being the same as in Example 1, to finally obtain the ammonia oxidation catalyst DA1.

[0194] XPS characterization of the ammonia oxidation catalyst DA1 is shown in [reference needed]. Figure 2 .

[0195] In the ammonia oxidation catalyst DA1, the mass ratio of active component to support is 1.01:1, and the median particle size of DA1 is 53 μm. The CeVO4 crystalline phase accounts for 40 wt% of the weight of the ammonia oxidation catalyst DA1, and the CeV4 surface of the ammonia oxidation catalyst J... 4+ molar amount / Ce 3+ The molar amount is 1.5.

[0196] Performance evaluation of DA1 ammonia oxidation catalyst:

[0197] Feed molar ratio of m-xylene:NH3:O2 = 1:10:7; catalyst loading 0.060 h⁻¹ -1 The reaction temperature was 405℃ and the reaction system pressure was 101kPa.

[0198] Reaction results: m-xylene conversion rate 99.8%; isophthalonitrile selectivity 75.8%; isophthalonitrile yield 75.6%; catalyst attrition rate 1.18%.

[0199] Comparative Example 2

[0200] Preparation of ammonia oxidation catalyst DA2:

[0201] The method of Example 1 differs in that:

[0202] Solution L1 was slowly added to 1250g of silica sol with a SiO2 content of 40wt% to obtain solution L4. Then, solution L2 was added to solution L4 and stirred for 30min to obtain solution L5. Finally, solution L3 was quickly added to solution L5. The mixture was then heated and concentrated under stirring to obtain a viscous slurry with a solid content of 30wt%. The slurry was then calcined in air for 10 hours, and the rest was the same as in Example 1, to finally obtain the ammonia oxidation catalyst DA2.

[0203] In the ammonia oxidation catalyst DA2, the mass ratio of active component to support is 1.06:1, and the median particle size is 54 μm. The CeVO4 crystalline phase accounts for 43 wt% of the weight of the ammonia oxidation catalyst DA2, and the CeV4 surface of the ammonia oxidation catalyst J... 4+ molar amount / Ce 3+ The molar amount is 1.4.

[0204] Performance evaluation of DA2 ammonia oxidation catalyst:

[0205] Feed molar ratio of m-xylene:NH3:O2 = 1:10:7; catalyst loading 0.060 h⁻¹ -1 The reaction temperature was 405℃ and the reaction system pressure was 101kPa.

[0206] Reaction results: m-xylene conversion 99.2%; isophthalonitrile selectivity 75.5%; isophthalonitrile yield 74.9%; catalyst attrition rate 1.15%.

[0207] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An ammonia oxidation catalyst, characterized in that, It includes a carrier and an active component; the active component includes a vanadium-cerium composite oxide containing a CeVO4 crystal phase; Among them, XPS elemental analysis of the catalyst surface showed the presence of Ce. 4+ With Ce 3+ And Ce 3+ The number of moles is not less than Ce 4+ The number of moles.

2. The ammonia oxidation catalyst according to claim 1, wherein, In the XPS elemental analysis of the catalyst surface, Ce 4+ With Ce 3+ The molar ratio is 0.2-0.8:1, preferably 0.2-0.6:1; and / or The catalyst does not contain Cr. and / or The active component, calculated by element, further contains adjuvant elements, wherein the adjuvant elements include: Element A, selected from phosphorus and / or boron; and / or Element B, selected from at least one element chosen from manganese, nickel, cobalt, titanium, tungsten, molybdenum, niobium, copper, and iron, preferably selected from at least one element chosen from manganese, molybdenum, niobium, and iron, more preferably, element B includes at least niobium, and at least one element chosen from manganese, molybdenum, and iron; and / or The element C is selected from at least one element in Group IA and / or IIA, preferably from at least one element selected from lithium, sodium, potassium, rubidium, calcium and strontium.

3. The ammonia oxidation catalyst according to claim 2, wherein, The general molecular formula of the active component in atomic ratio is shown in formula (1): V 1.0 What a A b B c C d A x formula(1), In equation (1): V is vanadium, Ce is cerium, the value of a ranges from 0.6 to 2.5, the value of b ranges from 0.2 to 1.2, the value of c ranges from 0.01 to 0.5, the value of d ranges from 0 to 0.5, and x is the number of oxygen atoms required to satisfy the oxidation state of each element in equation (1). Preferably, in formula (1): The value of a ranges from 0.6 to 1.0; and / or The value of b ranges from 0.4 to 0.8; and / or The value of c ranges from 0.01 to 0.15; and / or The value of d ranges from 0 to 0.

2.

4. The ammonia oxidation catalyst according to any one of claims 1-3, wherein, In the catalyst, CeVO4 accounts for 70%-98% of the active component by mass, preferably 85%-95%; and / or In the catalyst, the mass ratio of the active component to the support is (0.6-1.6):1, preferably (0.8-1.2):1; and / or The support is selected from at least one of SiO2, Al2O3, TiO2, ZrO2, MgO and molecular sieves, preferably SiO2.

5. The ammonia oxidation catalyst according to any one of claims 1-4, wherein, The median particle size of the catalyst is 45 μm-55 μm; and / or, The catalyst attenuation rate is no higher than 1.1 wt%.

6. A method for preparing the ammonia oxidation catalyst according to any one of claims 1-5, characterized in that, The preparation method includes: (1) The solution L3 containing cerium source is brought into first contact with the solution L1 containing vanadium source and reducing agent to obtain solution L4; (2) Optionally, solution L4 is brought into a second contact with solution L2 containing an auxiliary agent source, and then into a third contact with a carrier precursor. Optionally, it is then concentrated and finally dried and calcined. The calcination is carried out in an inert atmosphere.

7. The preparation method according to claim 6, wherein, The inert atmosphere is selected from at least one of carbon dioxide, group zero gases, and nitrogen, preferably carbon dioxide, and group zero gases and / or nitrogen, preferably carbon dioxide, with a volume ratio of 1-3:10 to group zero gases and / or nitrogen; and / or The roasting is carried out at least at 450-750°C, preferably at 500-600°C, and the total roasting time is preferably 7-28 hours, more preferably 12-21 hours. Preferably, the roasting is a two-stage roasting, where the temperature of the first stage roasting is lower than the temperature of the second stage roasting; More preferably, The conditions for the first stage of roasting include: a temperature of 150-220℃, preferably 180-200℃; and / or a time of 2-8 hours, preferably 4-6 hours; and / or The conditions for the second stage of roasting include: a temperature of 450-750℃, preferably 500-600℃; and / or a time of 5-20 hours, preferably 8-15 hours.

8. The preparation method according to claim 6 or 7, wherein, The cerium source is selected from nitrates and / or ammonium nitrates corresponding to the element cerium; and / or The vanadium source is selected from at least one of the following: oxides, ammonium salts, sulfates, oxalates, and tartrates of vanadium; and / or The auxiliary agent source includes precursor A, precursor B, and optionally precursor C, wherein precursor A is selected from at least one of the acids, ammonium salts, and oxides corresponding to phosphorus and / or boron; precursor B is selected from at least one of the acids, ammonium salts, oxides, and nitrates corresponding to at least one of manganese, nickel, cobalt, titanium, tungsten, molybdenum, niobium, copper, and iron; precursor C is selected from nitrates corresponding to at least one element in Group IA and / or IIA; and / or The reducing agent is selected from at least one of oxalic acid, formic acid, citric acid, and hydroxylamine hydrochloride; and / or The vanadium source, calculated as vanadium element, has a molar ratio of reducing agent to vanadium of 0.5-1.5:1, preferably 0.8-1.

3.

9. The use of the ammonia oxidation catalyst according to any one of claims 1-5 in the preparation of aromatic nitrile.

10. A method for preparing isophthalonitrile, characterized in that, The method includes: In the presence of the ammonia oxidation catalyst according to any one of claims 1-5, m-xylene, an ammonia source, and an oxygen-containing gas undergo an ammonia oxidation reaction; Preferably, the ammonia source is NH3, and the molar ratio of m-xylene to the ammonia source is 1:5-12; and / or The oxygen-containing gas, expressed as oxygen, has a molar ratio of m-xylene to the oxygen-containing gas of 1:2-10; and / or The oxygen-containing element is selected from air and / or oxygen; and / or The ammonia source is selected from ammonia gas; and / or The ammonia oxidation reaction is carried out in a fluidized bed reactor; and / or The conditions for the ammonia oxidation reaction include: a reaction temperature of 350-430℃; and / or a reaction pressure of 101-120 kPa; and / or a catalyst loading of 0.04-0.08 h⁻¹. -1 .

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