A composite oxide catalyst for the synthesis of isophthalonitrile and its preparation and application

Abstract

This invention discloses a method for preparing a catalyst for the production of isophthalonitrile from m-xylene and its application. The catalyst comprises an active component containing manganese, cobalt, copper, and optionally at least one selected from sodium, potassium, magnesium, and calcium; optionally at least one selected from iron, nickel, zinc, aluminum, and lead; and optionally at least one selected from boron, phosphorus, and sulfur. In the presence of the catalyst, isophthalonitrile is obtained by one-step ammoxidation of m-xylene as a raw material in an atmosphere of air and ammonia. The catalyst used in this invention has the advantages of low cost, good thermal conductivity, strong water resistance, strong cycle stability, high reactivity, ability to reduce reaction temperature, inhibition of deep oxidation, and improved reaction selectivity.

Description

Technical Field

[0001] This invention relates to the field of preparation technology of improved catalysts for the production of isophthalonitrile, and specifically to a method for preparing a manganese-cobalt-copper-based catalyst for the production of isophthalonitrile from m-xylene and its application. Background Technology

[0002] Aromatic nitriles such as isophthalonitrile are very useful compounds with wide applications in pharmaceuticals, dyes, herbicides, agrochemicals, and electronic materials. In organic synthesis, they are also important organic raw material intermediates. Utilizing the high reactivity of the cyano group and its ability to activate other sites on the benzene ring, amines, amides, aldehydes, carboxylic acids, and heterocyclic compounds can be synthesized through reactions such as hydrolysis, hydrogenation, addition, condensation, polymerization, and halogenation.

[0003] Traditionally, nitriles can be synthesized through nucleophilic reactions of alkyl halides, aryl sulfonates, diazonium salts, or nitro compounds with various metal cyanides. However, these methods have many problems. Using stoichiometric or excess inorganic cyanide salts as raw materials is not only highly toxic but also generates large amounts of inorganic salt waste, and the required raw materials are not readily available. Alternatively, using m-dichlorobenzene as a raw material and hydrogen cyanide as the cyanide source, isophthalonitrile is produced at temperatures above 500°C on a nickel oxide catalyst supported on alumina, with a yield of only 41.7%. Moreover, hydrogen cyanide is a highly toxic compound, so this method is not only low in yield but also highly dangerous. In contrast, the ammonia oxidation method using m-xylene as a raw material has attracted widespread attention and is currently the simplest and most economical method for producing isophthalonitrile. This method uses m-xylene as a raw material and, under the conditions of a catalyst, ammonia, and air, produces isophthalonitrile in one step through an ammonia oxidation reaction. It features safe production, a simple process, and the ability to produce in large quantities. The core technology of ammonia oxidation is the development of catalysts. It is urgent to develop catalysts with advantages such as low cost, high reactivity, and high selectivity.

[0004] Early catalysts used for producing isophthalonitrile primarily employed simple vanadium oxides, using m-xylene as a raw material. The ammonia oxidation reaction was carried out under ammonia and air conditions at temperatures exceeding 400°C. While isophthalonitrile could be produced, the yield was low. Adding modifying elements is the main method to further improve the reaction performance of vanadium-based catalysts. Among them, V-Cr catalysts have been widely used due to their ease of industrial scale-up, good batch stability, and high ammonia oxidation activity. However, V-Cr catalysts also suffer from problems such as deep oxidation, numerous side reactions, and strong ammonia decomposition capabilities, resulting in the generation of large amounts of CO, CO2, and HCN, leading to low selectivity and yield of the target product, isophthalonitrile. Therefore, other catalyst systems have been developed, but they still have some drawbacks. Patent CN109847744B discloses a method for preparing a V-Pb-Pd based catalyst and a method for preparing isophthalonitrile from m-xylene via ammonia oxidation. By precisely controlling the ratio of Pb to Pd, the activation energy in the ammonia oxidation reaction can be effectively reduced, resulting in high m-xylene conversion, high selectivity, and high yield of isophthalonitrile at lower reaction temperatures. However, the use of one or more noble metals such as Pd, Ir, Rh, and Ru increases the preparation cost of the catalyst. Patent CN115041203A discloses a method for preparing and applying an ammonia oxidation catalyst. By introducing Tl and S into the catalyst's active components V and Cr, the introduction of S solves the problem of deep oxidation and improves catalyst selectivity. Although this catalyst has good reactivity and thermal conductivity, and achieves a high yield of isophthalonitrile, Tl is a typical rare dispersed element found in nature and is highly toxic, polluting the environment and causing significant harm to the human body. Thallium compounds are mutagenic, carcinogenic, and teratogenic. Patent CN114471645A discloses a vanadium and cerium composite oxide for the gas-phase ammonia oxidation to produce isophthalonitrile. While this catalyst exhibits high conversion rates of m-xylene and good selectivity for isophthalonitrile, the reaction temperature is high, and the alumina support used is prone to transformation at high temperatures, leading to a decrease in catalyst activity. Considering the various shortcomings of currently used catalysts, designing and synthesizing catalysts with better performance is urgently needed and has significant practical and scientific research value. Summary of the Invention

[0005] This invention uses m-xylene as a raw material and performs a one-step gas-phase ammonia oxidation to obtain m-benzonitrile under conditions of a heterogeneous metal catalyst, ammonia, and air. The conversion rate of m-xylene is 99.7%, the yield of m-benzonitrile is 99.0%, and the selectivity is 99.3%. The heterogeneous metal catalyst used in this invention has a simple metal composition and is inexpensive, avoiding the use of precious metals in other patents. By adjusting the ratio of manganese, cobalt, and copper, alkali metals, alkaline earth metals, transition metals, and non-metallic heteroatoms are introduced into the manganese-based catalyst, which increases the number of lattice oxygen and crystal surface defects in the catalyst. This achieves high catalytic activity, lowers the reaction temperature, maintains high selectivity for the conversion of m-xylene to isophthalonitrile, and simultaneously enhances the catalyst's water resistance and extends its service life.

[0006] This invention is mainly achieved through the following technical solutions:

[0007] A composite oxide catalyst for the synthesis of isophthalonitrile, characterized in that the composite oxide catalyst comprises an active component and a silica support, wherein the active component contains manganese, cobalt, copper, and optionally at least one of sodium, potassium, magnesium, and calcium, optionally at least one of iron, nickel, zinc, aluminum, and lead, and optionally at least one of boron, phosphorus, and sulfur.

[0008] The active component of the ammonia oxidation catalyst, calculated in atomic ratios, satisfies the following general formula: Mn 2.0 Co 2.0 Cu 1.0 A a B b C c O x A is selected from at least one of sodium, potassium, magnesium, and calcium; B is selected from at least one of iron, nickel, zinc, aluminum, and lead; and C is selected from at least one of boron, phosphorus, and sulfur.

[0009] The value of 'a' ranges from 1.5 to 3.5; preferably from 1.0 to 2.0.

[0010] The value of b ranges from 0.3 to 1.5; preferably from 0.5 to 1.0.

[0011] The value of c ranges from 0.05 to 1.0; preferably from 0.1 to 0.5.

[0012] x represents the proportion of oxygen atoms required to satisfy the oxidation state of the metal;

[0013] The silica support required for the ammonia oxidation catalyst is one or more of silica sol, SBA-15, and FDU-12.

[0014] The method for preparing the catalyst for producing isophthalonitrile includes the following steps:

[0015] (1) Disperse or dissolve the required metal precursor salt in water according to the proportions in the general formula of the catalyst, and stir evenly to obtain solution I. (2) Disperse the required support for the catalyst in water and stir at room temperature for 30 min to obtain solution II. (3) Under stirring conditions, add solution I to solution II, sonicate for 30 min, then heat to 60℃ and continue stirring for 2 h to obtain a precursor mixture of the catalyst. (4) Spray dry the precursor mixture into the required particles, then dry at 100-200℃, preferably 120-150℃, and then heat at 5-15℃ / min, preferably 5-10℃ / min, to 300-800℃, preferably 600-800℃, and calcine at this temperature for 2-10 h, preferably 6-8 h, to obtain the composite oxide catalyst product.

[0016] The source of manganese in the ammonia oxidation catalyst is selected from one or more of manganese sulfate, manganese nitrate, manganese acetate, and manganese chloride; the source of cobalt is selected from one or more of cobalt sulfate, cobalt nitrate, cobalt acetate, cobalt acetylacetonate, and cobalt chloride; the source of copper is selected from one or more of copper sulfate, copper nitrate, copper acetate, copper chloride, and copper acetylacetonate; the source of A is selected from the chloride of the element it represents; the source of B is selected from one or more of the nitrate, chloride, and acetate of the element it represents; and the source of C is selected from one or more of boric acid, sodium monohydrogen phosphate, sodium dihydrogen phosphate, sodium phosphate, and sodium sulfide.

[0017] The silica support of the ammonia oxidation catalyst has a content of 30wt%-80wt%, preferably 40wt%-60wt%, by mass fraction.

[0018] The application method of the aforementioned ammonia oxidation catalyst is as follows:

[0019] isophthalonitrile is prepared by ammonia oxidation of m-xylene, ammonia, and air in the presence of the catalyst used for the production of isophthalonitrile. The molar ratio of m-xylene, ammonia, and air is 1:2-15:50; the reaction temperature is 250℃-400℃, preferably 260℃-350℃; the pressure is 1-400 kPa, preferably 20-300 kPa; the reactants are vaporized, uniformly mixed, and then introduced into the reactor; the catalyst weight loading is 0.01-0.5 h. -1 , preferably 0.03-0.4h -1 .

[0020] This invention primarily addresses the problems of high cost (due to the use of precious metals) and low reactivity, poor selectivity, and low product yield of catalysts produced in existing technologies when used in ammonia oxidation reactions. In the presence of the catalyst, m-xylene is used as a raw material for one-step ammonia oxidation to isophthalonitrile in an atmosphere of air and ammonia. The catalyst used in this invention has advantages such as low cost, good thermal conductivity, strong water resistance, strong cycle stability, high reactivity, ability to reduce reaction temperature, inhibition of deep oxidation, and improved reaction selectivity.

[0021] The present invention has the following advantages and effects compared with the prior art:

[0022] (1) The multiphase metal catalyst used in this invention has a simple metal composition, which avoids the use of precious metals in existing catalysts and greatly reduces production costs.

[0023] (2) The catalyst described in this invention can increase the number of lattice oxygen and crystal surface defects in the catalyst by adjusting the ratio of manganese, cobalt and copper, introducing alkali metals, alkaline earth metals, transition metals and non-metal heteroatoms into the manganese-based catalyst. This not only achieves high catalytic activity and reduces the reaction temperature, but also maintains the high selectivity of catalytic conversion of xylene to isophthalonitrile, while enhancing the water resistance of the catalyst and extending its service life.

[0024] (3) The present invention uses m-xylene as raw material and obtains m-benzonitrile by gas-phase ammonia oxidation under the conditions of multiphase metal catalyst, ammonia and air. The conversion rate of m-xylene is 99.7% and the yield of m-benzonitrile is 99.0%, so the selectivity is 99.3%, which has the prospect of industrial production. Detailed Implementation

[0025] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto:

[0026] Example 1

[0027] 84.5g of manganese sulfate monohydrate, 124.5g of cobalt acetate tetrahydrate, 60.4g of copper nitrate trihydrate, 18.6g of potassium chloride, 29.7g of nickel chloride hexahydrate, and 1.5g of boric acid were weighed and dissolved in water, stirred until homogeneous, to obtain solution I. 431.3g of silica sol (40wt%) was weighed and stirred at room temperature for 30 min to obtain solution II. Under stirring conditions, solution I was added to solution II, sonicated for 30 min, then heated to 60℃ and stirred for 2 h to obtain a catalyst precursor mixture. The precursor mixture was spray-dried into the desired particles, then dried at 120℃, and then calcined in an atmosphere furnace at 600℃ for 6 h at an air atmosphere, with the temperature increased at 10℃ / min, to obtain the composite oxide catalyst product, the composition of which can be expressed as Mn2.0 Co 2.0 Cu 1.0 K1Ni 0.5 B 0.1 O 6.2 / SiO2, wherein the content of SiO2 is 60wt%.

[0028] Example 2

[0029] 84.5g of manganese sulfate monohydrate, 124.5g of cobalt acetate tetrahydrate, 60.4g of copper nitrate trihydrate, 14.6g of sodium chloride, 29.7g of nickel chloride hexahydrate, and 1.5g of boric acid were weighed and dissolved in water, stirred until homogeneous, to obtain solution I. 416.2g of silica sol (40wt%) was weighed and stirred at room temperature for 30 min to obtain solution II. Under stirring conditions, solution I was added to solution II, sonicated for 30 min, then heated to 60℃ and stirred for 2 h to obtain a catalyst precursor mixture. The precursor mixture was spray-dried into the desired particles, then dried at 120℃, and then calcined in an atmosphere furnace at 600℃ for 6 h at an air atmosphere, with the temperature increased at 10℃ / min, to obtain the composite oxide catalyst product, the composition of which can be expressed as Mn 2.0 Co 2.0 Cu 1.0 Na1Ni 0.5 B 0.1 O 6.2 / SiO2, wherein the content of SiO2 is 60wt%.

[0030] Example 3

[0031] 84.5g of manganese sulfate monohydrate, 124.5g of cobalt acetate tetrahydrate, 60.4g of copper nitrate trihydrate, 23.8g of magnesium chloride, 29.7g of nickel chloride hexahydrate, and 1.5g of boric acid were weighed and dissolved in water, stirred until homogeneous, to obtain solution I. 425g of silica sol (40wt%) was weighed and stirred at room temperature for 30 min to obtain solution II. Under stirring conditions, solution I was added to solution II, sonicated for 30 min, then heated to 60℃ and stirred for 2 h to obtain a catalyst precursor mixture. The precursor mixture was spray-dried into the desired particles, then dried at 120℃, and then calcined in an atmosphere furnace at 600℃ for 6 h at an air atmosphere, with the temperature increased at 10℃ / min, to obtain the composite oxide catalyst product, the composition of which can be expressed as Mn 2.0 Co 2.0 Cu 1.0 Mg1Ni 0.5 B 0.1 O 6.7 / SiO2, wherein the content of SiO2 is 60wt%.

[0032] Example 4

[0033] 84.5g of manganese sulfate monohydrate, 124.5g of cobalt acetate tetrahydrate, 60.4g of copper nitrate trihydrate, 27.7g of calcium chloride, 29.7g of nickel chloride hexahydrate, and 1.5g of boric acid were weighed and dissolved in water, stirred until homogeneous, to obtain solution I. 440g of silica sol (40wt%) was weighed and stirred at room temperature for 30 minutes to obtain solution II. Under stirring conditions, solution I was added to solution II, sonicated for 30 minutes, then heated to 60℃ and stirred for 2 hours to obtain a catalyst precursor mixture. The precursor mixture was spray-dried into the desired particles, then dried at 120℃, and then calcined in an atmosphere furnace at 600℃ for 6 hours at an air atmosphere, with the temperature increased at 10℃ / min, to obtain the composite oxide catalyst product, whose composition can be expressed as Mn 2.0 Co 2.0 Cu 1.0 Ca1Ni 0.5 B 0.1 O 6.7 / SiO2, wherein the content of SiO2 is 60wt%.

[0034] Example 5

[0035] 84.5g of manganese sulfate monohydrate, 124.5g of cobalt acetate tetrahydrate, 60.4g of copper nitrate trihydrate, 18.6g of potassium chloride, 29.7g of nickel chloride hexahydrate, and 1.5g of boric acid were weighed and dissolved in water, stirred until homogeneous, to obtain solution I. 400g of silica sol (40wt%) was weighed and stirred at room temperature for 30 minutes to obtain solution II. Under stirring conditions, solution I was added to solution II, sonicated for 30 minutes, then heated to 60℃ and stirred for 2 hours to obtain a catalyst precursor mixture. The precursor mixture was spray-dried into the desired particles, then dried at 120℃, and then calcined in an atmosphere furnace at 600℃ for 6 hours at an air atmosphere, with the temperature increased at 10℃ / min, to obtain the composite oxide catalyst product, the composition of which can be expressed as Mn 2.0 Co 2.0 Cu 1.0 K1Ni 0.5 B 0.1 O 6.2 / SiO2, of which the content of SiO2 is 55.6wt%.

[0036] Example 6

[0037] 84.5g of manganese sulfate monohydrate, 124.5g of cobalt acetate tetrahydrate, 60.4g of copper nitrate trihydrate, 18.6g of potassium chloride, 29.7g of nickel chloride hexahydrate, and 1.5g of boric acid were weighed and dissolved in water, stirred until homogeneous, to obtain solution I. 300g of silica sol (40wt%) was weighed and stirred at room temperature for 30 minutes to obtain solution II. Under stirring conditions, solution I was added to solution II, sonicated for 30 minutes, then heated to 60℃ and stirred for 2 hours to obtain a catalyst precursor mixture. The precursor mixture was spray-dried into the desired particles, then dried at 120℃, and then calcined in an atmosphere furnace at 600℃ for 6 hours at an air atmosphere, with the temperature increased at 10℃ / min, to obtain the composite oxide catalyst product, the composition of which can be expressed as Mn 2.0 Co 2.0 Cu 1.0 K1Ni 0.5 B 0.1 O 6.2 / SiO2, of which the content of SiO2 is 41.7wt%.

[0038] Example 7

[0039] 98.9g of manganese chloride tetrahydrate, 124.5g of cobalt acetate tetrahydrate, 60.4g of copper nitrate trihydrate, 18.6g of potassium chloride, 29.7g of nickel chloride hexahydrate, and 1.5g of boric acid were weighed and dissolved in water, stirred until homogeneous, to obtain solution I. 431.3g of silica sol (40wt%) was weighed and stirred at room temperature for 30 min to obtain solution II. Under stirring conditions, solution I was added to solution II, sonicated for 30 min, then heated to 60℃ and stirred for 2 h to obtain a catalyst precursor mixture. The precursor mixture was spray-dried into the desired particles, then dried at 120℃, and then calcined in an atmosphere furnace at 600℃ for 6 h at an air atmosphere, with the temperature increased at 10℃ / min, to obtain the composite oxide catalyst product, the composition of which can be expressed as Mn 2.0 Co 2.0 Cu 1.0 K1Ni 0.5 B 0.1 O 6.2 / SiO2, wherein the content of SiO2 is 60wt%.

[0040] Example 8

[0041] 98.9g of manganese chloride tetrahydrate, 124.5g of cobalt acetate tetrahydrate, 60.4g of copper nitrate trihydrate, 18.6g of potassium chloride, 47.5g of nickel chloride hexahydrate, and 1.5g of boric acid were weighed and dissolved in water, stirred until homogeneous, to obtain solution I. 400g of silica sol (40wt%) was weighed and stirred at room temperature for 30 minutes to obtain solution II. Under stirring conditions, solution I was added to solution II, sonicated for 30 minutes, then heated to 60℃ and stirred for 2 hours to obtain a catalyst precursor mixture. The precursor mixture was spray-dried into the desired particles, then dried at 120℃, and then calcined in an atmosphere furnace at 700℃ (10℃ / min) for 6 hours to obtain the composite oxide catalyst product, whose composition can be expressed as Mn 2.0 Co 2.0 Cu 1.0 K1Ni 0.8 B 0.1 O 6.5 / SiO2, of which the content of SiO2 is 57.3wt%.

[0042] Example 9

[0043] 98.9g of manganese chloride tetrahydrate, 124.5g of cobalt acetate tetrahydrate, 60.4g of copper nitrate trihydrate, 28.0g of potassium chloride, 47.5g of nickel chloride hexahydrate, and 1.5g of boric acid were weighed and dissolved in water, stirred until homogeneous, to obtain solution I. 400g of silica sol (40wt%) was weighed and stirred at room temperature for 30 minutes to obtain solution II. Under stirring conditions, solution I was added to solution II, sonicated for 30 minutes, then heated to 60℃ and stirred for 2 hours to obtain a catalyst precursor mixture. The precursor mixture was spray-dried into the desired particles, then dried at 120℃, and then calcined in an atmosphere furnace at 700℃ at a rate of 10℃ / min for 6 hours to obtain the composite oxide catalyst product, whose composition can be expressed as Mn 2.0 Co 2.0 Cu 1. 0K 1.5 Ni 0.8 B 0.1 O 6.7 / SiO2, of which the content of SiO2 is 56.3wt%.

[0044] Example 10

[0045] 98.9g of manganese chloride tetrahydrate, 124.5g of cobalt acetate tetrahydrate, 60.4g of copper nitrate trihydrate, 28.0g of potassium chloride, 75.0g of aluminum nitrate nonahydrate, and 1.5g of boric acid were weighed and dissolved in water, stirred until homogeneous, to obtain solution I. 350g of silica sol (40wt%) was weighed and stirred at room temperature for 30 min to obtain solution II. Under stirring conditions, solution I was added to solution II, sonicated for 30 min, then heated to 60℃ and stirred for 2 h to obtain a catalyst precursor mixture. The precursor mixture was spray-dried into the desired particles, then dried at 120℃, and then calcined in an atmosphere furnace at 700℃ at a rate of 10℃ / min for 6 h to obtain the composite oxide catalyst product, the composition of which can be expressed as Mn 2.0 Co 2.0 Cu 1. 0K 1.5 Al 0.8 B 0.1 O 7.1 / SiO2, of which the content of SiO2 is 54.3wt%.

[0046] Comparative Example 1

[0047] 84.5g of manganese sulfate monohydrate, 124.5g of cobalt acetate tetrahydrate, 60.4g of copper nitrate trihydrate, 29.7g of nickel chloride hexahydrate, and 1.5g of boric acid were weighed and dissolved in water, stirred until homogeneous, to obtain solution I. 400g of silica sol (40wt%) was weighed and stirred at room temperature for 30 minutes to obtain solution II. Under stirring conditions, solution I was added to solution II, sonicated for 30 minutes, then heated to 60℃ and stirred for 2 hours to obtain a catalyst precursor mixture. The precursor mixture was spray-dried into the desired particles, then dried at 120℃, and then calcined in an atmosphere furnace at 600℃ for 6 hours at an air atmosphere, with the temperature increased at 10℃ / min, to obtain the composite oxide catalyst product, the composition of which can be expressed as Mn 2.0 Co 2.0 Cu 1.0 Ni 0.5 B 0.1 O 5.7 / SiO2, of which the content of SiO2 is 59.8wt%.

[0048] Comparative Example 2

[0049] 98.9g of manganese chloride tetrahydrate, 124.5g of cobalt acetate tetrahydrate, 28.0g of potassium chloride, 75.0g of aluminum nitrate nonahydrate, and 1.5g of boric acid were weighed and dissolved in water, stirred until homogeneous, to obtain solution I. 350g of silica sol (40wt%) was weighed and stirred at room temperature for 30 min to obtain solution II. Under stirring conditions, solution I was added to solution II, sonicated for 30 min, then heated to 60℃ and stirred for 2 h to obtain a catalyst precursor mixture. The precursor mixture was spray-dried into the desired particles, then dried at 120℃, and then calcined in an atmosphere furnace at 700℃ at a rate of 10℃ / min for 6 h to obtain the composite oxide catalyst product, whose composition can be expressed as Mn 2.0 Co 2.0 K 1.5 Al 0.8 B 0.1 O 6.1 / SiO2, of which the content of SiO2 is 57.9wt%.

[0050] Comparative Example 3

[0051] Catalyst V was prepared according to Example 1 of patent CN 109847744B. 1.0 Pb 0.3 Pd 0.02 Fe 0.6 Ir 0.01 Ce 0.8 O x .

[0052] Comparative Example 4

[0053] Catalyst V was prepared according to Example 1 of patent CN 109847744B. 1.0 Pb 0.1 Pd 0.05 Co 0.5 Pt 0.002 La 0.002 O x .

[0054] Example 11

[0055] The catalysts obtained in Examples 1-10 and Comparative Examples 1-4 were used under the same conditions for the one-step ammoxidation of m-xylene to prepare isophthalonitrile, and the reaction conditions are as follows:

[0056] The catalyst was loaded into a reactor for activity evaluation. The reaction conditions were: m-xylene: ammonia: air = 1:3:50, reaction temperature 260℃, and reaction pressure (gauge pressure) 20 kPa.

[0057]

[0058] As can be seen from Example 11 above, the catalyst prepared by the present invention has the characteristics of high conversion rate, high selectivity and high yield of m-benzonitrile in the reaction of m-xylene ammoxidation to m-benzonitrile. Most importantly, the catalyst used is inexpensive and avoids the use of precious metals.

Claims

1. A composite oxide catalyst for synthesizing isophthalonitrile, characterized by: The complex oxide catalyst comprises an active component and a silica carrier, and the composition of the active component satisfies the following general formula in terms of atomic ratio: Mn 2.0 Co 2.0 Cu 1.0 A a B b C c O x , a, b, c respectively represent the amount-of-substance ratio of elements A, B, C; wherein A is selected from at least one of sodium, potassium, magnesium, calcium, B is selected from at least one of iron, nickel, zinc, aluminum, lead, and C is selected from at least one of boron, phosphorus, sulfur, a is in the range of 1.5-3.5; b is in the range of 0.3-1.5; c is in the range of 0.05-1.0; x is the proportion of oxygen atoms required to satisfy the oxidation state of the metal.

2. The composite oxide catalyst according to claim 1, characterized by The silica carrier is one or more of silica sol, SBA-15, and FDU-12. The silica carrier of the catalyst has a content of 30wt%-80wt% in terms of mass fraction.

3. A process for the preparation of a catalyst for the synthesis of isophthalonitrile according to any one of claims 1-2, characterized in that, The preparation method comprises the following steps: (1) dispersing or dissolving the required metal precursor salt in water according to the molar ratio of the metals in the general formula of the catalyst, and stirring uniformly to obtain solution I; (2) dispersing the required carrier of the catalyst in water, and stirring at room temperature to obtain solution II; (3) mixing solution I into solution II under stirring, ultrasonicating first, then heating to 50-80℃, and continuing to stir for 1-5h to obtain a precursor mixture of the catalyst; (4) spray drying the precursor mixture into the required particles, drying at 100-200℃, then heating to 300-800℃ at a rate of 5-15℃ / min, and calcining at the temperature for 2-10h to obtain the finished complex oxide catalyst.

4. The preparation method according to claim 3, wherein the precursor salt of manganese is selected from one or more of manganese sulfate, manganese nitrate, manganese acetate, and manganese chloride; the precursor salt of cobalt is selected from one or more of cobalt sulfate, cobalt nitrate, cobalt acetate, cobalt acetylacetonate, and cobalt chloride; the precursor salt of copper is selected from one or more of copper sulfate, copper nitrate, copper acetate, copper chloride, and copper acetylacetonate; the precursor salt of A is selected from the chlorides of the respective elements represented by A; the precursor salt of B is selected from one or more of the nitrates, chlorides, and acetates of the respective elements represented by B; and the source of C is selected from one or more of boric acid, sodium monohydrogen phosphate, sodium dihydrogen phosphate, sodium phosphate, and sodium sulfide.

5. Use of the complex oxide catalyst according to any one of claims 1-2 in the catalytic synthesis of isophthalonitrile. The method comprises the following steps:

6. Use according to claim 5, characterized in that, The isophthalonitrile is prepared by the ammoxidation reaction of m-xylene, ammonia, and air in the presence of the catalyst for synthesizing isophthalonitrile according to any one of claims 1-2. The molar ratio of the m-xylene, ammonia, and air is 1:2-15:50, the reaction temperature is 250-400℃, the pressure is 1-400 kPa, and the reaction raw materials are uniformly mixed after gasification and introduced into the reactor.

7. Use according to claim 6, characterized in that, ​

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