An ammonia oxidation catalyst, a preparation method and application thereof

Abstract

The application provides an ammonia oxidation catalyst, which comprises a HZSM-5 carrier and an active component, the active component comprising: V; one or more of Cr, Zr, Ti and Mo; one or more of Al, Ga and Ag; and one or more of Bi, P and Sb. The application also provides a preparation method of the ammonia oxidation catalyst, which comprises mixing an aluminum source and a silicon source to obtain a first reaction solution; mixing an aqueous solution containing a compound of the active component with the first reaction solution to obtain an impregnation mixed solution, and performing concentration, drying and calcination to obtain the ammonia oxidation catalyst. The ammonia oxidation catalyst of the application can improve product selectivity, reduce the degree of deep oxidation of raw materials, improve the conversion rate of raw materials, reduce the waste of raw materials, and has high stability and mechanical strength, and is suitable for large-scale industrial production and application.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to an ammonia oxidation catalyst, its preparation method, and its application. Background Technology

[0002] Aromatic cyanides possess high chemical reactivity and can be synthesized into various fine chemical products through hydrogenation and condensation reactions. They are widely used in many industries, including pharmaceuticals, fragrances, pesticides, and resins. As an important raw material source, the demand for aromatic cyanides has been growing both domestically and internationally in recent years. Their synthesis involves the ammoxidation of aromatic hydrocarbons to obtain aromatic cyanides under ammonia and catalyst conditions. Due to the advantages of this manufacturing process, such as simple operation, safety, high yield, and low pollution, many scholars both domestically and internationally have invested heavily in research to achieve widespread application.

[0003] In the 1950s, Allied pioneered the research and development of aromatic hydrocarbon ammoxidation technology. Simultaneously, many other companies, such as Distiller and Bayer, also began research on related ammoxidation catalysts. In 1969, Nippon Shokubai Chemical Co., Ltd. built a production plant for phthalonitrile and benzonitrile using its own developed technology via mixed aromatic hydrocarbon ammoxidation. In 1970, a Japanese company collaborated with an American company to build an isophthalonitrile production plant. Subsequently, Mitsubishi Gas Chemical of Japan successfully built an industrial-scale isophthalonitrile production plant with Bagder Corporation of the United States, leading to the widespread adoption and application of aromatic hydrocarbon ammoxidation technology.

[0004] CN114950404A relates to a wear-resistant ammonia oxidation catalyst with the general formula V-(1.0)Ce-aX-bY-cO-d / C@S; X is selected from one or more transition metals Ti, Zr, Mo, W, and Pd; Y is selected from one or more KR group elements B, In, P, and Sb; the atomic ratio of a is 0.15-1.0, the atomic ratio of b is 0.05-1.0, the atomic ratio of c is 0.01-0.1, and d is the number of oxygen atoms required to satisfy the valence of other elements; the general formula of the support component is C@S, where C is selected from porous carbon materials, and S represents the shell layer covering the catalyst. This document claims that the obtained catalyst not only has good mechanical properties and high thermal stability, but also exhibits significantly improved stability during the reaction, making it suitable for large-scale stable industrial production.

[0005] CN114471645A discloses a catalyst for the gas-phase ammoxidation of m-xylene to isophthalonitrile, its preparation method, and its application. The active component of the catalyst comprises a composite oxide containing vanadium and cerium, wherein CeVO4 accounts for 35-75% of the catalyst mass. This catalyst is suitable for the fluidized bed process of gas-phase ammoxidation of m-xylene to isophthalonitrile.

[0006] CN106362760A discloses a mixed catalyst V for ammonia oxidation. 1.0 Cr a A b B c C d D e E f M g O x Wherein, A is selected from at least one element in Group IIIA of the periodic table; B is selected from at least one element in Group VA of the periodic table; C is selected from at least one element in alkali metals or alkaline earth metals; D is selected from at least one element in Group VIII of the periodic table; E is selected from at least one of Mo, Ti, and Nb; and M is selected from at least one of Zr and W. This literature claims that its method effectively improves the wear resistance of the catalyst while maintaining its high activity and selectivity, and that the resulting catalyst can be applied to the industrial production of aromatic hydrocarbon ammoxidation.

[0007] In summary, existing technologies have optimized the wear resistance and raw material cost of ammonia oxidation catalysts, but they do not mention methods for integrating support modification with catalyst molding, nor do they address technical solutions for reducing the degree of deep oxidation of reactants and decreasing the selectivity of small molecule products such as carbon dioxide and carbon monoxide. Therefore, there is an urgent need to develop a novel ammonia oxidation catalyst and its preparation method, which aims to not only improve product selectivity, reduce the degree of deep oxidation of reactants, increase the conversion rate of reactants, and reduce waste, but also improve the stability and mechanical strength of ammonia oxidation catalysts, thereby increasing catalyst production efficiency and making them suitable for large-scale industrial production applications. Summary of the Invention

[0008] To address the problems existing in the prior art, the present invention provides an ammonia oxidation catalyst, its preparation method, and its application. The ammonia oxidation catalyst can not only improve product selectivity, reduce the degree of deep oxidation of raw materials, increase the conversion rate of raw materials, and reduce raw material waste, but also has high stability and mechanical strength, improves production efficiency, and is suitable for large-scale industrial production applications. It is suitable for application in the ammonia oxidation of aromatic hydrocarbons to prepare m-aromatic nitrile, and is especially suitable for application in the ammonia oxidation of m-xylene to prepare isophthalonitrile.

[0009] To achieve its purpose, the present invention adopts the following technical solution:

[0010] In one aspect of the present invention, a method for preparing an ammonia oxidation catalyst is provided, comprising the following steps:

[0011] (1) Mix the aluminum source and the silicon source to obtain a first mixture; mix the first mixture with an additive to obtain a first reaction solution;

[0012] (2) Prepare an aqueous solution containing the active component of the compound to obtain the second reaction solution;

[0013] (3) Slowly mix the second reaction solution with the first reaction solution to form an impregnation mixture;

[0014] (4) The impregnation mixture is concentrated, dried and calcined to obtain the ammonia oxidation catalyst;

[0015] in,

[0016] The auxiliary agent is an organic dicarboxylic acid;

[0017] The active components include: V; Cr; one or more of Zr, Ti and Mo; one or more of Al, Ga and Ag; and one or more of Bi, P and Sb.

[0018] In the preparation method of the ammonia oxidation catalyst of the present invention, a second reaction solution is prepared, a support synthesis solution is prepared and mixed with an auxiliary agent to form a first reaction solution, the first reaction solution and the second reaction solution are mixed to allow some components in the first reaction solution and the second reaction solution to react, and the active component is impregnated on the support. The resulting impregnated mixture is then concentrated, dried and calcined in sequence to obtain the ammonia oxidation catalyst.

[0019] In step (2), it is involved in preparing an aqueous solution containing the active component of the compound. It should be noted that, in the technical field of the present invention, when the active component of the catalyst is determined, a person skilled in the art can appropriately select the compound containing the active component and obtain a mixed solution of the compound containing these active components in a suitable manner. The compound containing the active component is, for example, an acid, oxide, ammonium salt, acetate, and nitrate containing these active components.

[0020] In a preferred embodiment of the present invention, the auxiliary agent is a C2-C6 organic dicarboxylic acid, more preferably one or more of oxalic acid, succinic acid and adipic acid, and most preferably oxalic acid.

[0021] In a preferred embodiment of the present invention, the molar ratio of the adjuvant to the active component V is 0.1-30:1, preferably 0.5-20:1, for example 1:1, 3:1, 5:1, 8:1, 10:1, 15:1, 20:1, 25:1, etc., and also for example 1.5:1, 2:1, 4:1, 6:1, 9:1, 11:1, 13:1, 16:1, 18:1, etc.

[0022] The inventors of this application have surprisingly discovered that by adding an auxiliary agent to the first reaction solution, the size and number of pores in the carrier can be controlled, which is beneficial for the target raw material to enter the pores and combine with the reactive sites during the ammonia oxidation catalytic reaction.

[0023] Unbound by any theoretical constraints, it is worth noting that the addition of auxiliary agents to the first reaction solution of this invention has a significant auxiliary effect on the pore-expanding modification of SiO2 and the increase of acidic sites. This effectively controls the pore size in the support to be comparable to the molecular dynamics diameter of benzene molecules (approximately 0.6 nm), thus improving shape selectivity. It also enhances the adsorption of ammonia, increases the selectivity of aromatic products, and reduces the degree of deep oxidation of the raw materials. The organic dicarboxylic acid auxiliary agent is also an oxidant for the reduction of the valence states of active components V and Cr, further facilitating the formation of the active component CrVO4.

[0024] In a preferred embodiment of the present invention, the aluminum source includes sodium aluminate and / or aluminum sulfate.

[0025] In a preferred embodiment of the invention, the silicon source comprises tetraethyl orthosilicate and / or silica sol. Aluminum in the aluminum source also serves as an active component of the catalyst.

[0026] In a preferred embodiment of the present invention, the silicon-to-aluminum ratio of the silicon source to the aluminum source is 1:0.001-0.1, preferably 1:0.005-0.07, for example 1:0.008, 1:0.01, 1:0.03, 1:0.05, 1:0.09, etc., and also for example 1:0.007, 1:0.009, 1:0.015, 1:0.02, 1:0.04, 1:0.06, etc.

[0027] It is worth noting that by precisely adjusting the silica-alumina ratio of the first reaction solution, the Al2O3 content in the carrier can be precisely adjusted, thereby controlling the acidity of the carrier and providing more ammonia adsorption sites for the subsequent ammonia oxidation reaction. If the silica-alumina ratio is higher than the range selected in this invention, there will be insufficient acidic sites, resulting in insufficient ammonia adsorption capacity and an inability to reduce the degree of xylene oxidation. If the silica-alumina ratio is lower than the range selected in this invention, there will be an increase in strong acidic sites, leading to excessive ammonia adsorption and difficulty in reacting with xylene in the ammonia oxidation reaction, resulting in a deeper degree of xylene oxidation to produce carbon dioxide.

[0028] In a preferred embodiment of the present invention, the slow mixing in step (3) involves adding the second reaction solution dropwise to the first reaction solution to carry out a dropwise reaction.

[0029] In a preferred embodiment of the present invention, the dripping time in step (3) is 0.5-15h, preferably 1-12h, such as 2h, 4h, 6h, 8h, 10h, 14h, etc.

[0030] In a preferred embodiment of the present invention, the temperature of the dropwise reaction in step (3) is 50-120°C, for example 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, etc.

[0031] In a preferred embodiment of the present invention, the pressure of the dropwise reaction in step (3) is 30-110 kPa, such as 40 kPa, 50 kPa, 60 kPa, 70 kPa, 80 kPa, 90 kPa, 100 kPa and atmospheric pressure.

[0032] In a preferred embodiment of the present invention, the concentration in step (4) is evaporative concentration, with a temperature of 50-120°C, such as 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, etc.; and a pressure of 30-900 mbar, such as 50 mbar, 100 mbar, 300 mbar, 500 mbar, 550 mbar, 600 mbar, 800 mbar, etc.

[0033] In a preferred embodiment of the present invention, the evaporation and concentration yields a slurry with a solid content of 30-70%, wherein the solid content can be, for example, 35%, 40%, 45%, 50%, 55%, 60%, 65%, etc.

[0034] In a preferred embodiment of the present invention, the drying in step (4) is spray drying. Preferably, the inlet temperature of the spray dryer is 150-350°C, for example, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 280°C, 290°C, etc. The outlet temperature of the spray dryer is 90-190°C, for example, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, or 180°C, etc.

[0035] In a preferred embodiment of the present invention, the heating rate of the calcination in step (4) is 1-10℃ / min, preferably 2-6℃ / min, such as 3℃ / min, 5℃ / min, 7℃ / min or 10℃ / min, and also, for example, 2.5℃ / min, 3.5℃ / min, 4.5℃ / min, 5.5℃ / min. The calcination temperature is 500-750℃, preferably 550-700℃, such as 600℃, 650℃, etc. The calcination time is 2-12h, preferably 3-9h, such as 4h, 6h, 8h, 10h, etc. Preferably, only one-stage calcination is performed in step (4).

[0036] In another aspect of the invention, an ammonia oxidation catalyst is provided, comprising a support and an active component, wherein the support is an HZSM-5 molecular sieve; and the active component satisfies the following formula:

[0037] V 1.0 Cr a B b C c Dd O x

[0038] in,

[0039] B is selected from one or more of Zr, Ti and Mo; C is selected from one or more of Al, Ga and Ag; and D is selected from one or more of Bi, P and Sb.

[0040] a = 0.05-5.0, preferably a = 0.08-3.0; b = 0.01-2.0, preferably b = 0.05-1.0; c = 0.001-1.0, preferably c = 0.01-0.8; d = 0.001-1.0, preferably d = 0.01-0.5; x is the atomic ratio of oxygen required to satisfy the oxidation states of each element, preferably x = 2.0-9.0.

[0041] In the ammonia oxidation catalyst of this invention, by precisely defining the stoichiometric ratio of V to Cr in the active component and defining the stoichiometric ratio of C-type metal elements, effective composite reaction active sites can be formed. This enables the active component and the support to form synergistic reaction active sites, effectively reducing the activation energy of the ammonia oxidation reaction, increasing the adsorption of ammonia, reducing the degree of deep oxidation of aromatic hydrocarbon feedstocks, reducing the generation of small molecule products, and ensuring the conversion rate of aromatic hydrocarbon feedstocks and product selectivity.

[0042] Furthermore, in the ammonia oxidation catalyst of the present invention, by precisely defining the stoichiometric ratio of type B and type D metal elements in the active component, the stability and mechanical strength of the ammonia oxidation catalyst can be effectively guaranteed, thus ensuring the stability of the ammonia oxidation catalyst during long-term operation.

[0043] In formula V 1.0 Cr a B b C c D d O x In this context, a = 0.05-5.0, for example, 0.1, 0.3, 0.5, 0.7, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, etc.; b = 0.01-2.0, for example, 0.03, 0.05, 0.08, 0.1, 0.3, 0.5, 0.7, 1.0, 1.3, 1.5, 1.7, etc.; c = 0.00 1-1.0, for example 0.003, 0.005, 0.008, 0.01, 0.03, 0.05, 0.08, 0.1, 0.3, 0.5, 0.7, etc.; d=0.001-1.0, for example 0.003, 0.005, 0.008, 0.01, 0.03, 0.05, 0.08, 0.1, 0.3, 0.5, 0.7, etc.

[0044] As a preferred technical solution of the present invention, in formula V 1.0 Cr a B b C c D d O x In this context, a = 0.08-3.0, for example, 0.15, 0.35, 0.65, 0.85, 1.2, 1.8, 2.3, 2.5, 2.8, etc.; b = 0.05-1, for example, 0.07, 0.11, 0.15, 0.25, 0.45, 0.65, 0.85, 0.9, etc.; c = 0.01-0.8, for example, 0.02, 0.05, 0.06, 0.07, 0.09, 0.12, 0.2, 0.4, 0.6; d = 0.01-0.5, for example, 0.02, 0.04, 0.06, 0.09, 0.12, 0.15, 0.23, 0.35, 0.45, etc.

[0045] In a preferred embodiment of the present invention, the ammonia oxidation catalyst described above is obtained by the above preparation method.

[0046] In a preferred embodiment of the present invention, the content of the active component, calculated as a metal oxide, is 20-70 wt%, for example, 30%, 40%, 50%, 60%, etc.

[0047] The carrier described in this invention is HZSM-5 molecular sieve, which belongs to the artificially synthesized Al2O3 / SiO2 type molecular sieve and has a double ten-membered ring cross-channel structure.

[0048] In a preferred embodiment of the present invention, the silicon-to-aluminum ratio of the carrier is 1:0.001-0.1, preferably 1:0.005-0.07, based on the molar ratio of SiO2 to Al, for example 1:0.008, 1:0.01, 1:0.03, 1:0.05, 1:0.09, etc., and also for example 1:0.007, 1:0.009, 1:0.015, 1:0.02, 1:0.04, 1:0.06, etc.

[0049] In another aspect of the invention, a method for preparing an aromatic nitrile is disclosed, comprising using an aromatic hydrocarbon, ammonia, and an oxygen-containing gas as raw materials, and subjecting the aromatic hydrocarbon to ammoxidation in the presence of a catalyst to obtain the aromatic nitrile, wherein the catalyst is an ammoxidation catalyst obtained by the above-described preparation method or the aforementioned ammoxidation catalyst. Preferably, the aromatic hydrocarbon is m-xylene, and the aromatic nitrile is isophthalonitrile.

[0050] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in the following aspects:

[0051] (1) By precisely limiting the stoichiometric ratio of V to Cr in the active component and limiting the stoichiometric ratio of B, C and D metal elements, it can not only improve product selectivity, reduce the degree of deep oxidation of raw materials, increase the conversion rate of raw materials and reduce raw material waste, but also have high stability and mechanical strength, ensure that the support and catalyst are integrally formed, improve the catalyst production efficiency, and be suitable for large-scale industrial production applications.

[0052] (2) The support in the ammonia oxidation catalyst of the present invention is an HZSM-5 type molecular sieve that is integrally generated with the catalyst. By precisely adjusting the silicon-aluminum ratio of the first reaction liquid during the preparation process, the Al2O3 content in the support can be precisely adjusted, thereby controlling the acidity of the support and providing more ammonia adsorption sites for the subsequent ammonia oxidation reaction.

[0053] (3) The support in the ammonia oxidation catalyst of the present invention is an HZSM-5 type molecular sieve that is integrally generated with the catalyst. By adding an auxiliary agent, it has a good auxiliary effect on the pore-expanding modification of SiO2 and the increase of acid sites. It can effectively control the size of the pores in the support to be equivalent to the molecular dynamic diameter of benzene (about 0.6 nm), that is, improve the shape selectivity. It can also enhance the adsorption of ammonia, improve the selectivity of aromatic products, reduce the degree of deep oxidation of raw materials, and make the active component oxidant and the support auxiliary agent integrated. The auxiliary agent used is pollution-free, reduces production costs, and improves production efficiency. Detailed Implementation

[0054] The present invention will be described in further detail below, but the present invention is not limited thereto.

[0055] raw material

[0056] Unless otherwise specified, all raw materials mentioned in this article are commercially available and of AR purity.

[0057] Test methods

[0058] Catalyst composition and active component content: measured using an inductively coupled plasma (ICP) spectrometer.

[0059] The calculation methods for the conversion rate of the feedstock m-xylene and the selectivity of the target product m-phthalonitrile in the examples are as follows:

[0060] m-Xylene conversion rate (%) = (moles of m-xylene reacted / moles of m-xylene fed) × 100%;

[0061] Selectivity of isophthalonitrile (%) = (moles of isophthalonitrile produced / moles of m-xylene reacted) × 100%.

[0062] Example

[0063] Example 1

[0064] I. Preparation of ammonia oxidation catalyst

[0065] (1) Add 2.49g NaAlO2 to 120g water and stir at room temperature until completely dissolved to form an aluminum source; add the aluminum source to 404.5g silica sol with a mass percentage of 30% and mix to obtain the first mixture; then add 295g oxalic acid to the first mixture to obtain the first reaction solution.

[0066] (2) First, slowly add 44.6g of vanadium pentoxide to 106.8g of chromic acid solution (concentration of 55wt%), then dissolve 7.28g of ammonium molybdate, 3.28g of phosphoric acid and 1.9g of antimony acetate in 100g of water respectively, and add them to the above chromic acid solution to form a second reaction solution;

[0067] (3) The second reaction solution containing the active component is slowly added dropwise to the first reaction solution in step (1) to form an impregnation mixture. The slow dropwise addition reaction time is 2 hours, the temperature is 60°C, and the pressure is atmospheric pressure.

[0068] (4) The impregnation mixture described in step (3) is evaporated and concentrated at 85°C and pressure of 550 mbar until a slurry with a solid content of 50% is obtained. The obtained slurry is spray-dried at an inlet temperature of 250°C and an outlet temperature of 170°C to obtain a catalyst precursor. The obtained catalyst precursor is placed in a muffle furnace and calcined at a heating rate of 2°C / min to 600°C and held at that temperature for 3 hours. Finally, it is cooled to room temperature to obtain ammonia oxidation catalyst 1#.

[0069] Testing revealed that the proportion of active components in the aforementioned ammonia oxidation catalyst #1 was as follows:

[0070] V 1.0 Cr 1.0 Mo 0.08 P 0.05 Al 0.01 Sb 0.012 O 5.91 The content of the active component, calculated as a metal oxide, is 56 wt%.

[0071] II. Evaluation of Catalyst Reaction Performance

[0072] The ammonia oxidation catalyst No. 1 obtained above was loaded into an ammonia oxidation fluidized bed reactor for reaction performance evaluation. The feed ratio of the reaction raw materials was 1:3.1:12 molar ratio of m-xylene:ammonia:oxygen. The reaction temperature of the ammonia oxidation reactor was 400℃, the reaction pressure (gauge pressure) was 70 kPa, and the catalyst weight load in the reactor was 0.05 h⁻¹.-1 .

[0073] After the reactor ran for 100 hours, the conversion rate of m-xylene was 99.5%, and the selectivity of isophthalonitrile was 99.59%.

[0074] Example 2

[0075] I. Preparation of ammonia oxidation catalyst

[0076] (1) Add 2.49g NaAlO2 to 120g water and stir at room temperature until completely dissolved to form an aluminum source; add the aluminum source to 404.5g silica sol with a mass percentage of 30% and mix to obtain the first mixture; then add 295g oxalic acid to the first mixture to obtain the first reaction solution.

[0077] (2) First, slowly add 44.6g of vanadium pentoxide to 160.02g of chromic acid solution (concentration of 55wt%), then dissolve 7.28g of ammonium molybdate, 3.28g of phosphoric acid and 19g of antimony acetate in 100g of water respectively, and add them to the above chromic acid solution to form a second reaction solution;

[0078] (3) The second reaction solution containing the active component is slowly added dropwise to the first reaction solution in step (1) to form an impregnation mixture. The slow dropwise addition reaction time is 2 hours, the temperature is 60°C, and the pressure is atmospheric pressure.

[0079] (4) The impregnation mixture described in step (3) is evaporated and concentrated at 85°C and pressure of 550 mbar until a slurry with a solid content of 50% is obtained. The obtained slurry is spray-dried at an inlet temperature of 250°C and an outlet temperature of 170°C to obtain a catalyst precursor. The obtained catalyst precursor is placed in a muffle furnace and calcined at a heating rate of 2°C / min to 600°C and held at that temperature for 3 hours. Finally, it is cooled to room temperature to obtain ammonia oxidation catalyst 2#.

[0080] Testing revealed that the proportion of active components in the aforementioned ammonia oxidation catalyst #2 was as follows:

[0081] V 1.0 Cr 1.5 Mo 0.08 P 0.05 Al 0.01 Sb 0.12 O 7.56 The content of the active component, calculated as a metal oxide, is 60 wt%.

[0082] II. Evaluation of Catalyst Reaction Performance

[0083] The ammonia oxidation catalyst No. 2 obtained above was loaded into an ammonia oxidation fluidized bed reactor for reaction performance evaluation. The feed ratio of the reaction raw materials was 1:3.1:12 molar ratio of m-xylene:ammonia:oxygen. The reaction temperature of the ammonia oxidation reactor was 400℃, the reaction pressure (gauge pressure) was 70 kPa, and the catalyst weight load in the reactor was 0.05 h⁻¹. -1 .

[0084] After the reactor ran for 100 hours, the conversion rate of m-xylene was 97.5%, and the selectivity of isophthalonitrile was 95.8%.

[0085] Example 3

[0086] I. Preparation of ammonia oxidation catalyst

[0087] (1) Add 2.49g NaAlO2 to 120g water and stir at room temperature until completely dissolved to form an aluminum source; add the aluminum source to 404.5g silica sol with a mass percentage of 30% and mix to obtain the first mixture; then add 295g oxalic acid to the first mixture to obtain the first reaction solution.

[0088] (2) First, slowly add 44.6g of vanadium pentoxide to 160.02g of chromic acid solution (concentration of 55wt%), then dissolve 7.28g of ammonium molybdate, 6.27g of gallium nitrate and 19g of antimony acetate in 100g of water respectively, and add them to the above chromic acid solution to form a second reaction solution;

[0089] (3) The second reaction solution containing the active component is slowly added dropwise to the first reaction solution in step (1) to form an impregnation mixture. The slow dropwise addition reaction time is 2 hours, the temperature is 60°C, and the pressure is atmospheric pressure.

[0090] (4) The impregnation mixture described in step (3) is evaporated and concentrated at 85°C and pressure of 550 mbar until a slurry with a solid content of 50% is obtained. The obtained slurry is spray-dried at an inlet temperature of 250°C and an outlet temperature of 170°C to obtain a catalyst precursor. The obtained catalyst precursor is placed in a muffle furnace and calcined at a heating rate of 2°C / min to 600°C and held at that temperature for 3 hours. Finally, it is cooled to room temperature to obtain ammonia oxidation catalyst #3.

[0091] Testing revealed that the proportion of active components in the aforementioned ammonia oxidation catalyst #3 was as follows:

[0092] V 1.0 Cr 1.5 Mo 0.08 Ga 0.05 Al 0.01 Sb 0.12 O 7.51The content of the active component, calculated as a metal oxide, is 60 wt%.

[0093] II. Evaluation of Catalyst Reaction Performance

[0094] The ammonia oxidation catalyst #3 obtained above was loaded into an ammonia oxidation fluidized bed reactor for performance evaluation. The feed ratio of the reactants was 1:3.1:12 (molecular weight of xylene:ammonia:oxygen). The reaction temperature of the ammonia oxidation reactor was 400℃, the reaction pressure (gauge pressure) was 70 kPa, and the catalyst weight load in the reactor was 0.05 h⁻¹. -1 .

[0095] After the reactor ran for 100 hours, the conversion rate of m-xylene was 98.5%, and the selectivity of isophthalonitrile was 96.3%.

[0096] Example 4

[0097] I. Preparation of ammonia oxidation catalyst

[0098] (1) Add 2.49g NaAlO2 to 120g water and stir at room temperature until completely dissolved to form an aluminum source; add the aluminum source to 404.5g silica sol with a mass percentage of 30% and mix to obtain the first mixture; then add 295g oxalic acid to the first mixture to obtain the first reaction solution.

[0099] (2) First, slowly add 44.6g of vanadium pentoxide to 106.8g of chromic acid solution (concentration of 55wt%), then dissolve 16.84g of zirconium nitrate, 4.16g of silver nitrate and 1.9g of antimony acetate in 230g of water and add them to the above chromic acid solution to form a second reaction solution;

[0100] (3) The second reaction solution containing the active component is slowly added dropwise to the first reaction solution in step (1) to form an impregnation mixture. The slow dropwise addition reaction time is 3.5h, the temperature is 60℃, and the pressure is atmospheric pressure.

[0101] (4) The impregnation mixture described in step (3) is evaporated and concentrated at 85°C and pressure of 550 mbar until a slurry with a solid content of 50% is obtained. The obtained slurry is spray-dried at an inlet temperature of 250°C and an outlet temperature of 170°C to obtain a catalyst precursor. The obtained catalyst precursor is placed in a muffle furnace and calcined at a heating rate of 2°C / min to 600°C and held at that temperature for 3 hours. Finally, it is cooled to room temperature to obtain ammonia oxidation catalyst #4.

[0102] Testing revealed that the proportion of active components in the aforementioned ammonia oxidation catalyst #4 was as follows:

[0103] V 1.0 Cr1.0 Zr 0.08 Ag 0.05 Al 0.01 Sb 0.012 O 5.718 The content of the active component, calculated as a metal oxide, is 56 wt%.

[0104] II. Evaluation of Catalyst Reaction Performance

[0105] The ammonia oxidation catalyst #4 obtained above was loaded into an ammonia oxidation fluidized bed reactor for performance evaluation. The feed ratio of the reactants was 1:3.1:12 (molecular weight of xylene:ammonia:oxygen). The reaction temperature of the ammonia oxidation reactor was 400℃, the reaction pressure (gauge pressure) was 70 kPa, and the catalyst weight load in the reactor was 0.05 h⁻¹. -1 .

[0106] After the reactor ran for 100 hours, the conversion rate of m-xylene was 99.15%, and the selectivity of isophthalonitrile was 97.83%.

[0107] Comparative Example 1

[0108] I. Preparation of ammonia oxidation catalyst

[0109] Step (1) is the same as in Example 1, except that oxalic acid is not added after obtaining the first mixture;

[0110] Steps (2) to (4) are the same as in Example 1, and the ammonia oxidation catalyst CE1 is obtained.

[0111] The proportion of active components in the above-mentioned ammonia oxidation catalyst CE1 was determined by testing:

[0112] V 1.0 Cr 1.0 Mo 0.08 P 0.05 Al 0.01 Sb 0.012 O 5.91 .

[0113] II. Evaluation of Catalyst Reaction Performance

[0114] Same as Example 1, except that catalyst CE1 is used.

[0115] After the reactor ran for 100 hours, the conversion rate of m-xylene was 67.8%, and the selectivity of isophthalonitrile was 40.5%.

[0116] Comparative Example 2

[0117] I. Preparation of ammonia oxidation catalyst

[0118] Step (1) is the same as in Example 3, except that no aluminum source is added. 295g of oxalic acid is added to 404.5g of silica sol with a mass percentage of 30% to obtain the first reaction solution.

[0119] Steps (2) to (4) are the same as in Example 3, and the ammonia oxidation catalyst CE2 is obtained.

[0120] The proportion of active components in the above-mentioned ammonia oxidation catalyst CE2 was determined by testing:

[0121] V 1.0 Cr 1.5 Mo 0.08 Ga 0.05 Sb 0.12 O 7.495 .

[0122] II. Evaluation of Catalyst Reaction Performance

[0123] Same as Example 3, except that the catalyst CE2 is used.

[0124] After the reactor ran for 100 hours, the conversion rate of m-xylene was 89.2%, and the selectivity of isophthalonitrile was 91.1%.

[0125] Comparative Example 3

[0126] I. Preparation of ammonia oxidation catalyst

[0127] Step (1) is the same as in Example 1;

[0128] Step (2) is the same as in Example 1, except that phosphoric acid and antimony acetate are not added;

[0129] Steps (3) to (4) are the same as in Example 1, and the ammonia oxidation catalyst CE3 is obtained.

[0130] The proportion of active components in the above-mentioned ammonia oxidation catalyst CE3 was determined by testing:

[0131] V 1.0 Cr 1.0 Mo 0.08 Al 0.01 O 4.225 .

[0132] II. Evaluation of Catalyst Reaction Performance

[0133] Same as Example 1, except that catalyst CE3 is used.

[0134] After 100 hours of reactor operation, the conversion rate of m-xylene was 94.5%, and the selectivity of isophthalonitrile was 90.1%. The catalyst loss rate reached 2.3% after being removed from the fluidized bed. Due to the absence of D-type elements, the catalyst's stability and mechanical strength were reduced.

[0135] Although the invention has been described in detail above for illustrative purposes, it should be understood that such detailed description is merely for illustration, and modifications can be made by those skilled in the art without departing from the spirit and scope of the invention, which is defined only by the claims.

Claims

1. A method for preparing an ammonia oxidation catalyst, comprising the following steps: (1) Mix the aluminum source and the silicon source to obtain a first mixture; mix the first mixture with an additive to obtain a first reaction solution; (2) Prepare an aqueous solution containing the active component of the compound to obtain a second reaction solution; (3) The second reaction solution is slowly mixed with the first reaction solution to form an impregnation mixture; (4) The impregnation mixture is concentrated, dried and calcined to obtain the ammonia oxidation catalyst; in, The auxiliary agent is an organic dicarboxylic acid; Based on the molar ratio of SiO2 to Al, the silicon-to-aluminum ratio of the silicon source to the aluminum source is 1:0.001-0.1; The active component satisfies the following formula: V 1.0 Cr a B b C c D d O x in, B is selected from one or more of Zr, Ti and Mo; C is selected from one or more of Al, Ga and Ag; and D is selected from one or more of Bi, P and Sb. a = 0.05-5.0; b = 0.01-2.0; c = 0.001-1.0; d = 0.001-1.0; x is the atomic ratio of oxygen required to satisfy the oxidation states of each element.

2. The preparation method according to claim 1, wherein, a=0.08-3.0; b=0.05-1.0; c=0.01-0.8; d=0.01-0.5; x=2.0-9.

0.

3. The preparation method according to claim 1, wherein, The auxiliary agent is a C2-C6 organic dicarboxylic acid; and / or The molar ratio of the adjuvant to the active component V is 0.1-30:

1.

4. The preparation method according to claim 3, wherein, The adjuvant is one or more of oxalic acid, succinic acid, and adipic acid; and / or The molar ratio of the adjuvant to the active component V is 0.5-20:

1.

5. The preparation method according to claim 1, wherein, The aluminum source includes sodium aluminate and / or aluminum sulfate; and / or The silicon source includes tetraethyl orthosilicate and / or silica sol; Based on the molar ratio of SiO2 to Al, the silicon-to-aluminum ratio of the silicon source to the aluminum source is 1:0.005-0.

07.

6. The preparation method according to any one of claims 1-5, wherein, The slow mixing described in step (3) involves adding the second reaction solution dropwise to the first reaction solution to carry out a dropwise reaction.

7. The preparation method according to claim 6, wherein, The dropping time in step (3) is 0.5-15h; the temperature of the dropping reaction in step (3) is 50-120℃; the pressure of the dropping reaction in step (3) is 30-110kPa.

8. The preparation method according to claim 7, wherein, The dripping time in step (3) is 1-12 hours.

9. The preparation method according to any one of claims 1-5, wherein, The concentration described in step (4) is an evaporative concentration at a temperature of 50-120°C and a pressure of 30-900 mbar; and / or The drying described in step (4) is spray drying; and / or The heating rate of the roasting in step (4) is 1-10℃ / min; the roasting temperature is 500-750℃; and the roasting time is 2-12h.

10. The preparation method according to claim 9, wherein, The evaporation and concentration yields a slurry with a solid content of 30-70%; and / or The spray dryer has an inlet temperature of 150-350℃ and an outlet temperature of 90-190℃; and / or The heating rate of the roasting in step (4) is 2-6℃ / min; the roasting temperature is 550-700℃; and the roasting time is 3-9h.

11. The preparation method according to claim 9, wherein, In step (4), only the first-stage roasting is performed.

12. The ammonia oxidation catalyst obtained by the preparation method according to any one of claims 1-11.

13. The ammonia oxidation catalyst according to claim 12, wherein, The content of the active component, calculated based on metal oxides, is 20-70 wt%.

14. A method for preparing an aromatic nitrile, comprising using aromatic hydrocarbons, ammonia, and oxygen-containing gas as raw materials, and subjecting the aromatic hydrocarbons to ammoxidation in the presence of a catalyst to obtain the aromatic nitrile, wherein, The catalyst is an ammonia oxidation catalyst obtained by the preparation method according to any one of claims 1-11.

15. The preparation method according to claim 14, wherein, The aromatic hydrocarbon is m-xylene, and the aromatic nitrile is isophthalonitrile.