Ammonia oxidation catalyst as well as preparation method and application thereof

Abstract

The invention relates to an ammoxidation catalyst and a preparation method and application thereof, the ammoxidation catalyst comprises a carrier and active components, the carrier is silicon dioxide (SiO2), the active components comprise boron and chromium elements, and the boron element exists in the ammoxidation catalyst in the form of chromium boride. The catalyst belongs to a V-Cr system catalyst, loss of a boron element is reduced through chromium boride, deep oxidation of the catalyst caused by the loss of the boron element is prevented from being increased, the CO2 selectivity is prevented from being increased, the nitrile product selectivity is prevented from being reduced, the yield of the nitrile product under long-period operation is guaranteed, and the mechanical strength of the catalyst is improved. According to the present invention, the catalyst is used as the catalyst, and the cometallic element and the stoichiometric ratio are limited, such that the ammonia conversion rate in the ammoxidation reaction can be effectively improved, the selectivity of the catalyst on nitrile products is improved, and the catalyst is suitable for large-scale ammoxidation industrial production application, and is especially suitable for m-xylene ammoxidation preparation of isophthalonitrile.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of catalysts, and relates to an ammoxidation catalyst, in particular to an ammoxidation catalyst, a preparation method and application thereof. BACKGROUND

[0002] The aromatic nitrile cyanide has high chemical activity, and various fine chemical products can be synthesized through hydrogenation and condensation reaction. The aromatic nitrile has been widely used in many industries such as medicine, perfume, pesticide and resin. In recent years, the demand for aromatic nitrile as an important raw material source has shown a growth trend at home and abroad. The synthesis principle is that the aromatic nitrile cyanide is oxidized under the condition of ammonia and a catalyst to obtain aromatic nitrile from aromatic hydrocarbon ammoxidation.

[0003] The raw materials for ammoxidation are usually aromatic hydrocarbons, ammonia and air. In order to ensure the conversion rate of aromatic hydrocarbons, ammonia and air need to be greatly excessive. In order to ensure the safety of the reaction, the oxygen in the tail gas needs to be reduced to below the safety range to avoid combustion and explosion. This process is achieved by deep oxidation of organic matter and combustion of ammonia, which reduces the yield of the main product (nitrile) and greatly reduces the economic benefit. Therefore, it is necessary to enhance the oxygen consumption capacity of ammonia without affecting the yield of the main product.

[0004] CN111770911A relates to a catalyst for manufacturing nitriles, with a general formula of VaCrbBcXdOe, Cr represents chromium, B represents boron, X is selected from one element of phosphorus, molybdenum, iron, tungsten, germanium, manganese, tin, tantalum, antimony, sodium, potassium, magnesium, calcium, and the carrier is titanium oxide. The atomic ratio a = 1, b = 0.5-2.0, c = 0.01-1.5, d = 0-2.0, and e represents the oxygen number of the oxide or composite oxide formed by the combination of the above elements. The catalyst can inhibit hot spots, eliminate side reactions, etc., making stable operation possible, but the problem of loss of active components and reduction of activity during long-term operation of the catalyst has not been solved.

[0005] CN202210543813.X relates to a wear-resistant ammoxidation catalyst with a general formula of V-(1.0)Ce-aX-bY-cO-d / C@S; X is selected from one or more of transition metals Ti, Zr, Mo, W, Pd; Y is selected from one or more of main group elements B, In, P, Sb; a atomic ratio is 0.15-1.0, b atomic ratio is 0.05-1.0, c atomic ratio is 0.01-0.1, d is the number of oxygen atoms required to satisfy the valence of other elements; the carrier component has a general formula of C@S, C is selected from porous carbon material, and S represents a shell coated outside the catalyst. The catalyst has good mechanical properties, high thermal stability, and significantly improved reaction stability, but no improvement measures for long-term activity of the catalyst are mentioned.

[0006] CN106362760A discloses an ammoxidation mixed catalyst V 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 metal or alkaline earth metal; 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, Nb; M is selected from at least one of Zr, W. The patent effectively improves the wear resistance of the catalyst, while maintaining the high activity selectivity of the catalyst, and the obtained catalyst can be applied to the industrial production of aromatic ammoxidation, but there is still a problem of how to improve the long-period activity and catalyst life of the catalyst.

[0007] In summary, the existing technology for ammoxidation catalysts mainly focuses on optimizing the wear resistance, raw material cost and hot spot control to improve the catalytic performance, but lacks effective solutions to the problem of how to avoid deep oxidation caused by the loss of active components, leading to the increase of CO2 selectivity and the decrease of nitrile product selectivity. SUMMARY

[0008] To solve the above technical problems in the prior art, one of the purposes of the present application is to provide an ammoxidation catalyst, which belongs to a V-Cr system catalyst. The B element is introduced in the form of chromium boride (CrB), which can improve the mechanical strength of the catalyst, reduce the loss of boron element, and avoid deep oxidation caused by the loss of boron element, leading to the increase of CO2 selectivity and the decrease of nitrile product selectivity.

[0009] The second purpose of the present application is to provide a preparation method of the ammoxidation catalyst.

[0010] The third purpose of the present application is to provide the application of the ammoxidation catalyst, which can effectively improve the conversion rate of ammonia in the ammoxidation reaction, improve the selectivity of the catalyst to nitrile products, ensure the yield of nitrile products under long-period operation, and is suitable for large-scale ammoxidation industrial production, especially for the application in the preparation of m-xylene ammoxidation.

[0011] To achieve the above purposes, the technical scheme adopted by the present application is as follows:

[0012] In the first aspect of the present application, an ammoxidation catalyst is provided.

[0013] An ammonia oxidation catalyst, comprising a carrier and an active component, the carrier is silicon dioxide (SiO2), and the active component comprises boron and chromium elements, wherein the boron element exists in the ammonia oxidation catalyst in the form of chromium boride (CrB);

[0014] The active component satisfies the following general formula in terms of atomic ratio:

[0015] V 1.0 Cr a B b M c N d O x ;

[0016] wherein V represents vanadium, Cr represents chromium, B represents boron, M is selected from at least one of Sn, Ga, In, Ge, Sb or Mo, and N is selected from at least one of Rb, Na, K, Mg, P or Al;

[0017] wherein a=0.05-5, b=0.001-1, c=0.001-1, d=0.001-1, x=2.5-9.0, and x is a value determined by the oxidation degree of other elements.

[0018] It is worth noting that the boron element in the active component of the ammonia oxidation catalyst exists in the form of chromium boride (CrB), and in addition to boron and part of chromium combined with boron, other active components generally exist in the form of oxides, and a small amount of metal elements, compounds or salts may also exist due to the influence of specific operation conditions in the preparation process.

[0019] In an embodiment, the particle size D50 of the ammonia oxidation catalyst is 40-100 um, preferably 50-80 um, such as 40 um, 50 um, 60 um, 70 um, 80 um, 90 um or 100 um, etc., but not limited to the listed values, and other values not listed in the above value range are also applicable.

[0020] The ammonia oxidation catalyst prepared by the traditional method contains B elements in the form of boron oxide, but boron oxide will be converted into metaboric acid and boric acid and other B-containing impurities when it encounters water at high temperature. Boric acid and metaboric acid are volatile, so the content of B elements in the catalyst will gradually decrease as the reaction proceeds, and the presence of B-containing impurities will inhibit the deep oxidation of the catalyst, resulting in an increase in the deep oxidation ability of the catalyst and an increase in the CO2 selectivity, a decrease in the selectivity of nitrile products, and a decrease in the product yield as the running time increases.

[0021] The present inventors found in experiments that in the ammonia oxidation catalyst of the V-Cr system, by changing the existence mode of the B element, forming chromium boride with the Cr element, using the stability of the chromium boride, the phenomenon of gradual loss of the B element with the reaction can be reduced, the deep oxidation of the catalyst caused by the loss of the boron element is avoided, the selectivity of CO2 is improved, the selectivity of nitrile product is reduced, the yield of nitrile product under long-period operation is ensured, and the mechanical strength of the catalyst is improved.

[0022] Further, the present inventors also found that the ammonia oxidation catalyst can effectively ensure the selectivity of the nitrile and the mechanical strength of the catalyst by accurately limiting the stoichiometric ratio of the M type and N type metal elements in the active component, and ensure the stability of the ammonia oxidation catalyst in the long-period operation process.

[0023] It is worth noting that in the general formula V 1.0 Cr a B b M c N d O x , a=0.05-5, such as 0.05, 0.1, 0.3, 0.5, 0.7, 1, 1.5, 2, 3, 3.5, 4 or 5, b=0.001-1, such as 0.001, 0.003, 0.005, 0.008, 0.01, 0.03, 0.05, 0.08, 0.1, 0.3, 0.5 or 1, c=0.001-1, such as 0.001, 0.003, 0.005, 0.008, 0.01, 0.03, 0.05, 0.08, 0.1, 0.3, 0.5 or 1, d=0.001-1, such as 0.001, 0.003, 0.005, 0.008, 0.01, 0.03, 0.05, 0.08, 0.1, 0.3, 0.5 or 1, but not limited to the listed values, other values not listed in the above value range are also applicable.

[0024] As a preferred technical solution of the present application, the mass percentage content of the active component is 20-70%, preferably 25%-65%, and the balance is the carrier, based on the total mass of the ammonia oxidation catalyst.

[0025] It is worth noting that the mass percentage content of the active component is 20-70%, such as 20%, 30%, 40%, 50%, 60% or 70%, but not limited to the listed values, other values not listed in the above value range are also applicable.

[0026] The support in the ammonia oxidation catalyst of this invention is SiO2, which can be a commercially available product or prepared by a known conventional method. For example, it can be obtained from conventional sources such as silica sol, water glass, tetraethyl orthosilicate, or SiO2 solid powder. This invention does not have specific requirements.

[0027] Optionally, the support is silicon dioxide (SiO2), or it can be modified by known conventional methods such as impregnation loading to achieve high selectivity for nitrile conversion.

[0028] In the ammonia oxidation catalyst of this invention, the main active components are V and Cr, with chromium boride as the key structure. Specifically, oxygen supply is provided during the ammonia oxidation process by supplying lattice oxygen. The valence change of V is dominant; V alone would cause over-oxidation of the reactants to carbon dioxide. The addition of Cr promotes uniform dispersion of V on the support and reduces V's oxygen supply capacity. An appropriate Cr content gives the catalyst good reactivity and nitrile selectivity. By adding M-type elements and precisely controlling their content, the catalyst can ensure the yield of the main product while improving the conversion of ammonia, consuming a large amount of oxygen, and ensuring the safety and operability of the reaction. By adding N-type elements and precisely controlling the ratio, the pore structure of the support can be improved. The size of the pores in the support can be effectively controlled to be comparable to the molecular dynamics diameter of benzene (approximately 0.6 nm), thus improving shape selectivity and enhancing the adsorption of ammonia, improving the selectivity of aromatic products, reducing the degree of deep oxidation of the raw materials, preventing deep oxidation of reactants on the catalyst surface, and improving the selectivity of the pores for the production of nitriles from aromatic hydrocarbons.

[0029] In a second aspect of the invention, a method for preparing the ammonia oxidation catalyst is provided.

[0030] A method for preparing an ammonia oxidation catalyst includes the following steps:

[0031] S1: Prepare an aqueous solution of vanadium salt and chromium salt, add silica carrier to it, mix evenly and stir continuously to obtain a mixed solution;

[0032] S2: Prepare aqueous solutions of elemental salt M and elemental salt N respectively, then mix them with chromium boride, add them to the mixture in step S1, mix evenly and stir continuously to obtain a slurry;

[0033] S3: The slurry from step S2 is concentrated, dried, and calcined to obtain the ammonia oxidation catalyst.

[0034] The preparation method of the present invention determines the amount of each raw material according to the general formula of the active component in the ammonia oxidation catalyst. Specifically, those skilled in the art can adjust and optimize the amount based on known calculation methods and actual needs. The present invention will not provide a detailed description here.

[0035] In detail, the amounts of vanadium salt, chromium salt, M elemental salt, N elemental salt, and chromium boride used in steps S1-S3 are determined based on the active elements they contain, according to the general formula of the active components in the ammonia oxidation catalyst to be prepared. That is, the raw material ratio is adjusted so that the atomic ratio of V, Cr, B, M, and N elements in them satisfies the general formula V 1.0 Cr a B b M c N d O x Alternatively, the ratio of the amount of vanadium salt to chromium salt, M element salt, N element salt, and chromium boride, calculated based on the V, Cr, B, M, and N elements contained, shall satisfy a mass ratio of 1.0:0.05~5:0.001~1:0.001~1:0.001~1.

[0036] In one embodiment, the vanadium salt in step S1 is a soluble salt of vanadium, selected from at least one of vanadium oxalate, vanadium sulfate, sodium vanadate, ammonium vanadate, and ammonium metavanadate, preferably at least one of vanadium oxalate and ammonium metavanadate.

[0037] In one embodiment, the chromium salt in step S1 is a soluble salt of chromium, selected from at least one of chromium oxalate, chromium nitrate, chromic anhydride, and chromium chloride, preferably at least one of chromium oxalate and chromium nitrate.

[0038] In one embodiment, the aqueous solution of vanadium salt and chromium salt prepared in step S1 contains 1-40 wt% vanadium salt and 1-40 wt% chromium salt. Specifically, the vanadium salt content is 1-40 wt%, for example, 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, or 40 wt%, and the chromium salt content is 1-40 wt%, for example, 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, or 40 wt%, but is not limited to the listed values; other unlisted values ​​within the above range are also applicable.

[0039] In one embodiment, the amount of silica support added in step S1 is calculated based on the mass of the ammonia oxidation catalyst product prepared in step S3, and the content is controlled to be 30% to 80%; for example, 30%, 40%, 50%, 60%, 70% or 80%, etc., but not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0040] In one embodiment, the stirring temperature in step S1 is 55-100°C, preferably 60-90°C, such as 55°C, 60°C, 70°C, 80°C, 90°C or 100°C, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0041] In one embodiment, the stirring speed in step S1 is 50-500 r / min, and the time is 0.5-24 h; specifically, the stirring speed is 50-500 r / min, such as 50 r / min, 100 r / min, 200 r / min, 300 r / min, 400 r / min, or 500 r / min, etc., and the time is 0.5-24 h, such as 0.5 h, 1 h, 5 h, 10 h, 15 h, 20 h, or 24 h, etc., but is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0042] Optionally, the stirring pressure is 30 to 101 kPa; for example, 30 kPa, 40 kPa, 50 kPa, 60 kPa, 70 kPa, 80 kPa, 90 kPa or 101 kPa, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0043] In one embodiment, the M element salt in step S2 is a soluble salt selected from at least one of molybdenum oxide, ammonium molybdate, indium nitrate, gallium nitrate, antimony oxide, antimony acetate, germanium nitrate, and tin chloride, preferably at least one of indium nitrate, gallium nitrate, antimony acetate, and ammonium molybdate.

[0044] Optionally, the aqueous solution of the M element salt has a concentration of 0-25 wt%, such as 0 wt%, 0.1 wt%, 1 wt%, 5 wt%, 8 wt%, 10 wt%, 15 wt%, 20 wt%, or 25 wt%, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0045] In one embodiment, the N element salt in step S2 is a soluble salt selected from at least one of potassium chloride, sodium chloride, magnesium chloride, sodium aluminate, potassium aluminate, potassium acetate, sodium acetate, magnesium acetate, phosphoric acid, metaphosphoric acid, potassium phosphate, sodium phosphate, magnesium phosphate, rubidium chloride, etc., preferably at least one of potassium acetate, sodium acetate, magnesium acetate, phosphoric acid, and sodium aluminate.

[0046] Optionally, the aqueous solution of the N elemental salt has a concentration of 0-40 wt%, such as 0 wt%, 0.1 wt%, 1 wt%, 3 wt%, 5 wt%, 8 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, or 40 wt%, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0047] In one embodiment, the chromium boride described in step S2 is an existing product. The present invention does not have specific requirements regarding its source; it can be a commercially available product or prepared using known conventional methods, such as the following methods:

[0048] Weigh out a certain amount of chromium source and boron source, add aluminum powder and / or magnesium powder as reaction aids, mix evenly and react at a certain temperature to generate chromium boride.

[0049] The chromium source is selected from at least one of chromium oxalate, chromium nitrate, chromic anhydride, and chromium chloride, preferably at least one of chromium oxalate, chromium nitrate, and chromic anhydride.

[0050] The boron source is selected from at least one of elemental boron, boron oxide, and boric acid, preferably at least one of boron oxide and boric acid;

[0051] The molar ratio of the chromium source and the boron source, calculated by the Cr and B elements respectively, is 1:0.1 to 10.

[0052] The aluminum powder and / or magnesium powder and the boron source, based on the element B, have a molar ratio of 1:0.1 to 10.

[0053] The reaction is carried out at a temperature of 550–1000℃, preferably 600–900℃, for a time of 0.1–15 h.

[0054] In one embodiment, the aqueous solution of element M salt, the aqueous solution of element N salt, and chromium boride mentioned in step S2 are slowly added to the mixture in step S1 by dripping.

[0055] Optionally, the feeding time is 0.5 to 15 hours, preferably 1 to 12 hours, such as 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours or 12 hours, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0056] In one embodiment, the stirring temperature in step S2 is 60–90°C, and the stirring time is 0.2–24 h; specifically, the temperature is 60–90°C, for example, 60°C, 70°C, 80°C, or 90°C, and the stirring time is 0.2–24 h, for example, 0.2 h, 1 h, 5 h, 10 h, 15 h, 20 h, or 24 h, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0057] Optionally, the stirring speed is 150–600 r / min, such as 150 r / min, 200 r / min, 300 r / min, 400 r / min, 500 r / min, or 600 r / min, but is not limited to the listed values; other unlisted values ​​within the above range are also applicable.

[0058] Optionally, the stirring pressure is 30 to 101 kPa, such as 30 kPa, 40 kPa, 50 kPa, 60 kPa, 70 kPa, 80 kPa, 90 kPa or 101 kPa, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0059] In one implementation, the concentration in step S3 is achieved by evaporation concentration.

[0060] Optionally, the evaporation and concentration temperature is 50-100°C, preferably 60-90°C, such as 50°C, 60°C, 70°C, 80°C, 90°C or 100°C, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0061] Preferably, the evaporation and concentration yields a slurry with a solid content of 30-75%. The solid content can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or 75%, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0062] In one implementation, the drying in step S3 is spray drying;

[0063] Optionally, the inlet temperature of the spray dryer is 150–350°C, such as 150°C, 160°C, 180°C, 170°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 280°C, 290°C, or 350°C, and the outlet temperature is 90–190°C, such as 90°C, 100°C, 120°C, 140°C, 150°C, 160°C, 170°C, or 180°C, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0064] In one embodiment, the roasting temperature in step S3 is 500-750°C, preferably 550-700°C, such as 500°C, 550°C, 600°C, 620°C, 650°C, 680°C, 700°C or 750°C, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0065] Optionally, the heating rate of the calcination is 1 to 10 °C / min, preferably 2 to 6 °C / min, such as 1 °C / min, 3 °C / min, 5 °C / min, 7 °C / min or 10 °C / min, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0066] In one embodiment, the roasting time in step S3 is 1 to 15 hours, preferably 2 to 10 hours, such as 1 hour, 3 hours, 5 hours, 7 hours, 9 hours, 11 hours, 13 hours or 15 hours, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0067] In a third aspect of the invention, the use of the ammonia oxidation catalyst is provided.

[0068] The ammonia oxidation catalyst described in this invention can be used to prepare nitrile products by ammonia oxidation reaction, and is particularly suitable for the ammonia oxidation of m-xylene to prepare isophthalonitrile.

[0069] Specifically, a method for preparing isophthalonitrile, the method comprising the following steps:

[0070] Using the ammonia oxidation catalyst described in the first aspect, or the ammonia oxidation catalyst prepared by the method described in the second aspect, m-xylene, ammonia, and oxygen-containing gas are subjected to an ammonia oxidation reaction under the action of the ammonia oxidation catalyst to obtain isophthalonitrile.

[0071] Optionally, the reaction is carried out under the following operating conditions:

[0072] The feed molar ratio of m-xylene to ammonia and oxygen-containing gas is 1:2-14:20-50;

[0073] The oxygen-containing gas is selected from air;

[0074] The amount of ammonia oxidation catalyst used is based on a space velocity of: catalyst mass (g) / m-xylene feed rate (g / h) = 0.01–1 h. -1 ;

[0075] The ammonia oxidation reaction is carried out at a temperature of 370–440°C, a time of 2–1000 h, and a pressure of 10–100 kPa.

[0076] Compared with the prior art, the present invention has at least the following beneficial effects:

[0077] (1) The ammonia oxidation catalyst described in this invention belongs to the V-Cr system catalyst. By changing the existence mode of element B, the stability of chromium boride is utilized to reduce the phenomenon of element B gradually being lost as the reaction proceeds. This avoids the deep oxidation of the catalyst caused by the loss of element boron, which would lead to increased CO2 selectivity and decreased nitrile product selectivity. This ensures the yield of nitrile products under long-term operation and improves the mechanical strength of the catalyst.

[0078] (2) The ammonia oxidation catalyst of the present invention can ensure the uniform dispersion of active components by adding M and N elements and precisely controlling the ratio, effectively controlling the size of the pores in the support to be equivalent to the molecular dynamic diameter of benzene (about 0.6 nm), and can also enhance the adsorption of ammonia, improve the conversion rate of ammonia (increase oxygen consumption), improve the selectivity of aromatic products, reduce the degree of deep oxidation of raw materials, prevent the reactants from being deeply oxidized on the catalyst surface, improve the selectivity of the pores for the production of nitriles from aromatic hydrocarbons, and reduce the risk of combustion and explosion in the reaction.

[0079] (3) The ammonia oxidation catalyst of the present invention has a simple process and high operability. The catalyst prepared has high activity and selectivity, which facilitates the large-scale industrial production of the catalyst. Detailed Implementation

[0080] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0081] The applicant declares that the detailed process equipment and process flow of this invention are illustrated through the above embodiments, but this invention is not limited to the above detailed process equipment and process flow, that is, it does not mean that this invention must rely on the above detailed process equipment and process flow to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the products of this invention, additions of auxiliary components, and selection of specific methods, all fall within the protection scope and disclosure scope of this invention.

[0082] It should be noted that the endpoints and any values ​​of the ranges disclosed in this specification 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.

[0083] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0084] Unless otherwise specified, the reagents, materials and instruments used in the following examples are all conventional reagents, materials and instruments in the art, and can be obtained commercially. The reagents involved can also be synthesized by conventional methods in the art.

[0085] All raw materials used in the examples are conventional raw materials in the art, and the purity specification used is AR grade.

[0086] The ammonia supplier is Anhui Haoyuan Chemical Group.

[0087] The air used is compressed air from within the factory, and all other raw materials used, such as chromium boride, are manufactured by Beijing Innocare Technology Co., Ltd.

[0088] The main analytical methods used in the embodiments and comparative examples of this invention are as follows:

[0089] Laser particle size analyzer for determining product particle size distribution;

[0090] The contents of CO2, CO, O2 and N2 in the reaction products were determined by Agilent 1260 liquid chromatography (mobile phase: water and ethanol, column oven temperature: 40℃, test pressure: 80-170mbar) TCD circuit.

[0091] The contents of intermediate xylene and isophthalonitrile in the reaction products were determined by Shimadzu gas chromatography (test temperature 250℃, carrier gas helium, and conventional analysis of oxygen and nitrogen).

[0092] The formulas for calculating the conversion rate of the feedstock m-xylene and the selectivity of the target product m-phthalonitrile in the examples are as follows:

[0093] m-Xylene conversion rate (%) = (moles of m-xylene reacted / moles of m-xylene fed) × 100%;

[0094] Selectivity of isophthalonitrile (%) = (moles of isophthalonitrile produced / moles of m-xylene reacted) × 100%.

[0095] Example 1

[0096] The steps for preparing ammonia oxidation catalyst A are as follows:

[0097] S1: Weigh 367.53g of chromium nitrate and 305.89g of vanadium oxalate, add water and stir thoroughly to dissolve, and prepare an aqueous solution containing V and Cr elements, wherein the chromium nitrate content is 27.3wt% and the vanadium oxalate content is 22.7wt%. Then, under the conditions of 55kPa pressure, 60℃ temperature and 250r / min stirring, add 300g of silica powder, and continue stirring and heating for 0.5h to form a mixed solution.

[0098] S2: Weigh 116.48g of ammonium molybdate to prepare an aqueous solution with a concentration of 25wt%, weigh 16.2g of potassium acetate to prepare an aqueous solution with a concentration of 40wt%, mix with 37.03g of chromium boride, and add dropwise to the mixture in step S1 over 1 hour. Then stir for 0.5 hours at a pressure of 55kPa, a temperature of 60℃, and a rotation speed of 250r / min to obtain a slurry.

[0099] S3: The slurry from step S2 is continuously evaporated and concentrated at 80°C for 12 hours to obtain a slurry with a solid content of 40%. Then, it is spray-dried at an inlet temperature of 200°C and an outlet temperature of 105°C. Finally, it is calcined in a muffle furnace at 600°C for 5 hours at a calcination heating rate of 4°C / min to obtain ammonia oxidation catalyst A.

[0100] The active component is V 1.0 Cr 1.0 B 0.3 Mo 0.33 K 0.16 O 5.5 The boron element exists in the form of chromium boride; the active component content is 59.1 wt%, and the particle size D50 is 65 μm.

[0101] Example 2

[0102] The steps for preparing ammonia oxidation catalyst B are as follows:

[0103] S1: Weigh 87.84g of chromium oxalate and 305.89g of vanadium oxalate, add water and stir thoroughly to dissolve, and prepare an aqueous solution containing V and Cr elements, wherein the content of chromium oxalate is 11.15wt% and the content of vanadium oxalate is 38.85wt%. Then, under the conditions of 90kPa pressure, 90℃ temperature and 400r / min stirring, add 300g of silica powder, and continue stirring and heating for 1h to form a mixed solution.

[0104] S2: Weigh 58.24g of ammonium molybdate and 13.4g of gallium nitrate to prepare an aqueous solution with a total concentration of 10wt%, weigh 8.1g of potassium acetate and 6.56g of phosphoric acid to prepare an aqueous solution with a total concentration of 30wt%, mix with 37.03g of chromium boride, and add dropwise to the mixture in step S1 over 1.5h. Then stir for 1h at a pressure of 90kPa, a temperature of 90℃ and a speed of 400r / min to obtain a slurry.

[0105] S3: The slurry from step S2 is continuously evaporated and concentrated at 90℃ for 20h to obtain a slurry with a solid content of 65%. Then, it is spray-dried at an inlet temperature of 280℃ and an outlet temperature of 150℃. Finally, it is calcined in a muffle furnace at 550℃ for 9h at a calcination heating rate of 2℃ / min to obtain ammonia oxidation catalyst B.

[0106] The active component is V 1.0 Cr 0.54 B 0.3 Mo 0.16 Ga 0.026 P 0.034 K 0.1 O 4.369 The boron element exists in the form of chromium boride; the active component content is 50.9 wt%, and the particle size D50 is 75 μm.

[0107] Example 3

[0108] The steps for preparing ammonia oxidation catalyst C are as follows:

[0109] S1: Weigh 338.34g of chromium oxalate and 305.89g of vanadium oxalate, add water and stir thoroughly to dissolve, and prepare an aqueous solution containing V and Cr elements, wherein the content of chromium oxalate is 26.25wt% and the content of vanadium oxalate is 23.7wt%. Then, under the conditions of 55kPa pressure, 80℃ temperature and 300r / min stirring, add 300g of silica powder, and continue stirring and heating for 1h to form a mixed solution.

[0110] S2: Weigh 232.96g of ammonium molybdate and 15.2g of antimony acetate to prepare an aqueous solution with a total concentration of 10wt%, weigh 27g of potassium acetate and 131.2g of phosphoric acid to prepare an aqueous solution with a total concentration of 40wt%, mix with 18.5g of chromium boride, and add dropwise to the mixture in step S1 over 2 hours. Then stir for 0.5 hours at a pressure of 80kPa, a temperature of 75℃ and a speed of 300r / min to obtain a slurry.

[0111] S3: The slurry from step S2 is continuously evaporated and concentrated at 75°C for 20 hours to obtain a slurry with a solid content of 75%. Then, it is spray-dried at an inlet temperature of 220°C and an outlet temperature of 120°C. Finally, it is calcined in a muffle furnace at 650°C for 3 hours at a calcination heating rate of 6°C / min to obtain ammonia oxidation catalyst C.

[0112] The active component is V 1.0 Cr 1.0 B 0.15 Mo 0.66 Sb 0.05 P 0.67 K 0.28 O 8.095 The boron element exists in the form of chromium boride; the active component content is 67.2 wt%, and the particle size D50 is 55 μm.

[0113] Comparative Example 1

[0114] Weigh 507.7g of chromium nitrate and 305.89g of vanadium oxalate, dissolve them thoroughly in water at a mass ratio of 1:1, and prepare an aqueous solution A containing V and Cr elements. Heat the solution in a water bath at 60℃ for 30 minutes, then add 300g of silica powder and continue stirring and heating to form a mixed solution.

[0115] Weigh out 116.48g of ammonium molybdate, 16.2g of potassium acetate, and 36.44g of boric acid. Dissolve them thoroughly in water at a mass ratio of 1:1 and then add the solution to the above mixture to form a mixture.

[0116] The mixture was continuously evaporated and concentrated for 12 hours, spray-dried, and then calcined in a muffle furnace at 600°C to obtain the ammonia oxidation catalyst D.

[0117] The active component is V 1.0 Cr 1.0 B 0.3 Mo 0.33 K 0.16 O 5.5 The boron element exists in the form of boron oxide; the active component content is 60.6 wt%, and the particle size D50 is 65 μm.

[0118] Application examples

[0119] The ammonia oxidation catalyst AD prepared in Examples 1-3 and Comparative Example 1 was used to prepare isophthalonitrile, and the results are shown in Table 1.

[0120] The method for preparing isophthalonitrile is as follows:

[0121] In the fluidized bed reactor, the feed ratio is m-xylene to ammonia and oxygen-containing gas in a molar ratio of 1:9:42. The oxygen-containing gas is selected from air. The ammonia oxidation catalyst dosage is: catalyst mass (g) / m-xylene feed rate (g / h) = 0.75h. -1 The reaction temperature was 410℃, the reaction duration was 4 hours, and the reaction pressure was 20 kPa. Samples were analyzed by gas chromatography and liquid chromatography, and the catalytic activity data of the catalyst were calculated.

[0122] Table 1

[0123] m-xylene conversion, % m-phthalonitrile selectivity, % CO2 selectivity / % Example 1 99.3 82.5 7.5 Example 2 99.1 82.7 7.7 Example 3 99.7 80.1 10.2 Comparative Example 1 99.4 81.3 7.9

[0124] Catalyst lifetime evaluation experiment:

[0125] The catalyst A prepared in Example 1 was evaluated for long-term lifespan, and the reaction results at different operating times are shown in Table 2.

[0126] Table 2. Reaction results for catalyst long-cycle lifetime evaluation in Example 1.

[0127]

[0128] The catalyst prepared in Comparative Example 1 was evaluated for its long-term lifespan. The reaction results at different operating times are shown in Table 3.

[0129] Table 3. Results of long-term life evaluation of catalyst D in Comparative Example 1.

[0130]

[0131]

Claims

1. An ammonia oxidation catalyst, characterized in that, It includes a support and an active component, wherein the support is silicon dioxide (SiO2) and the active component contains boron and chromium, wherein the boron exists in the form of chromium boride (CrB) in the ammonia oxidation catalyst; Furthermore, the active components, calculated in atomic ratios, satisfy the following general formula: V 1.0 Cr a B b M c N d O x ; Wherein, V represents vanadium, Cr represents chromium, B represents boron, M is selected from at least one of Sn, Ga, In, Ge, Sb or Mo, and N is selected from at least one of Rb, Na, K, Mg, P or Al; Where a = 0.05~5, b = 0.001~1, c = 0.001~1, d = 0.001~1, x = 2.5~9.0, and x is a value determined by the degree of oxidation of other elements.

2. The ammonia oxidation catalyst according to claim 1, characterized in that, Particle size D50 is 40-100 μm, preferably 50-80 μm; and / or The active component comprises 20-70% by mass, preferably 25%-65%, based on the total mass of the ammonia oxidation catalyst, with the remainder being a carrier.

3. A method for preparing the ammonia oxidation catalyst according to claim 1 or 2, characterized in that, Includes the following steps: S1: Prepare an aqueous solution of vanadium salt and chromium salt, add silica carrier to it, mix evenly and stir continuously to obtain a mixed solution; S2: Prepare aqueous solutions of elemental salt M and elemental salt N respectively, then mix them with chromium boride, add them to the mixture in step S1, mix evenly and stir continuously to obtain a slurry; S3: The slurry from step S2 is concentrated, dried, and calcined to obtain the ammonia oxidation catalyst.

4. The preparation method according to claim 3, characterized in that, The ratio of the vanadium salt to the chromium salt, M element salt, N element salt, and chromium boride, calculated based on the content of V, Cr, B, M, and N elements, satisfies a mass ratio of 1.0:0.05~5:0.001~1:0.001~1:0.001~1; and / or The vanadium salt mentioned in step S1 is a soluble salt of vanadium, selected from at least one of vanadium oxalate, vanadium sulfate, sodium vanadate, ammonium vanadate, and ammonium metavanadate, preferably at least one of vanadium oxalate and ammonium metavanadate; and / or The chromium salt mentioned in step S1 is a soluble salt of chromium, selected from at least one of chromium oxalate, chromium nitrate, chromic anhydride, and chromium chloride, preferably at least one of chromium oxalate and chromium nitrate.

5. The preparation method according to claim 3 or 4, characterized in that, The aqueous solution prepared from the vanadium and chromium salts in step S1, wherein the content of vanadium salt is 1-40 wt% and the content of chromium salt is 1-40 wt%; and / or The amount of silica support added in step S1 is calculated based on the mass of the ammonia oxidation catalyst product prepared in step S3, and the content is controlled to be 30-80%; and / or The stirring temperature in step S1 is 55-100℃, preferably 60-90℃, and the stirring time is 0.5-24h; optionally, the stirring speed is 50-500r / min; optionally, the stirring pressure is 30-101kpa.

6. The preparation method according to any one of claims 3-5, characterized in that, The element salt M mentioned in step S2 is a soluble salt selected from at least one of molybdenum oxide, ammonium molybdate, indium nitrate, gallium nitrate, antimony oxide, antimony acetate, germanium nitrate, and tin chloride, preferably at least one of indium nitrate, gallium nitrate, antimony acetate, and ammonium molybdate; optionally, the aqueous solution of the element salt M has a concentration of 0-25 wt%; and / or The nitrogen salt mentioned in step S2 is a soluble salt selected from at least one of potassium chloride, sodium chloride, magnesium chloride, sodium aluminate, potassium aluminate, potassium acetate, sodium acetate, magnesium acetate, phosphoric acid, metaphosphoric acid, potassium phosphate, sodium phosphate, magnesium phosphate, and rubidium chloride, preferably at least one of potassium acetate, sodium acetate, magnesium acetate, phosphoric acid, and sodium aluminate; optionally, the aqueous solution of the nitrogen salt has a concentration of 0-40 wt%.

7. The preparation method according to any one of claims 3-6, characterized in that, The aqueous solutions of elemental salt M and elemental salt N, and chromium boride mentioned in step S2 are slowly added to the mixture from step S1 by dripping; optionally, the addition time is 0.5–15 h, preferably 1–12 h; and / or The stirring temperature in step S2 is 60–90°C, and the stirring time is 0.2–24 h; optionally, the stirring speed is 150–600 r / min; optionally, the stirring pressure is 30–101 kPa.

8. The preparation method according to any one of claims 3-7, characterized in that, The concentration in step S3 is achieved by evaporation concentration; optionally, the temperature of the evaporation concentration is 50-100℃, preferably 60-90℃; preferably, the evaporation concentration yields a slurry with a solid content of 30-75%; and / or The drying process described in step S3 is spray drying; optionally, the inlet temperature of the spray dryer is 150–350°C, and the outlet temperature is 90–190°C; and / or The roasting temperature in step S3 is 500-750℃, preferably 550-700℃; the time is 1-15h, preferably 2-10h; optionally, the roasting heating rate is 1-10℃ / min, preferably 2-6℃ / min.

9. The application of the ammonia oxidation catalyst according to claim 1 or 2, or the ammonia oxidation catalyst prepared by any one of claims 3-8, in the ammonia oxidation reaction to prepare nitrile products, especially suitable for the ammonia oxidation of m-xylene to prepare isophthalonitrile.

10. A method for preparing isophthalonitrile, characterized in that, The method uses the ammonia oxidation catalyst according to claim 1 or 2, or the ammonia oxidation catalyst prepared by any one of claims 3-8, to carry out the ammonia oxidation reaction of m-xylene, ammonia and oxygen-containing gas under the action of the ammonia oxidation catalyst to obtain isophthalonitrile.

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