Catalyst for preparing 2-cyanopyridine through catalytic ammoxidation and preparation method thereof

Abstract

The invention relates to a catalyst for preparing 2-cyanopyridine through catalytic ammoxidation and a preparation method of the catalyst, and belongs to the field of chemical engineering. Specifically, titanium dioxide is taken as a carrier, vanadium oxide and magnesium oxide-zinc auxiliaries are added to improve the specific surface area and porosity of the catalyst, and then water, oxalic acid and ammonium molybdate are added to prepare the catalyst. The yield of 2-cyanopyridine prepared by using the catalyst to catalyze ammoxidation reaction is greater than or equal to 91%, and the conversion rate is gt; 99.9%, and the reaction selectivity is gt; 92%. The preparation method of the catalyst is simple and convenient, the cost is low, the specific surface area and porosity of the catalyst are high, more lattice oxygen can be loaded, the activity of the catalyst is improved, and finally the yield, the conversion rate and the selectivity of 2-cyanopyridine prepared through ammoxidation are improved.

Description

Technical Field

[0001] The invention specifically relates to a catalyst for preparing 2-cyanopyridine by catalytic ammoxidation and a preparation method thereof, and belongs to the field of chemical industry. Background Art

[0002] 2-Cyanopyridine is an important organic synthesis intermediate. As an intermediate of monoamine oxidase inhibitors, analgesics, antibiotics and anticancer drugs, it plays a key role in pharmaceutical processes and pesticide synthesis. 2-Cyanopyridine is also used in metal surface treatment processes. It can be used as a passivating agent to form a protective film on the metal surface to prevent metal corrosion and oxidation. In the electronics, textiles, leather, coatings and other industries, 2-Cyanopyridine is also used as an intermediate of liquid crystal materials, pigments and dyes in the production of liquid crystals, optical materials, pigments and dyes.

[0003] The existing preparation process of 2-cyanopyridine includes continuous method, chemical synthesis method, ammoxidation method and pyridine synthesis method, among which the ammoxidation method has been widely used due to its simple process and convenient operation. However, in the ammoxidation process, the intermediate product of methyl oxidation (-CO-, -CNH, etc.) is very unstable, so the ammoxidation preparation of 2-cyanopyridine has the problems of low yield, poor selectivity and more by-products. Therefore, it is very important to prepare a catalyst with good selectivity, high yield and high conversion rate for the improvement of production efficiency and reduction of production cost of ammoxidation synthesis of 2-cyanopyridine.

[0004] Catalysts play an important role in the preparation of 2-cyanopyridine by ammoxidation. By optimizing the composition and preparation method of the catalyst, the efficiency and selectivity of the reaction can be significantly improved, the formation of by-products can be reduced, and thus the yield and quality of 2-cyanopyridine can be improved.

[0005] At present, in the field of catalyst preparation for catalytic ammoxidation reaction to prepare 2-cyanopyridine, patent CN107537537A adds P2O5 and MoO3 to the TiO2 carrier, so that the conversion rate of 2-methylpyridine reaches more than 98%, and its selectivity can reach more than 90%; patent CN115041160A adds citric acid to the mixture of V2O5 and MoO3, so that the yield of 2-cyanopyridine can reach 78-81%; patent CN116408116A mixes vanadium oxide with other transition metal oxides and non-metallic oxides to form a promoter, so that the conversion rate of 2-methylpyridine is greater than 99.9%, the selectivity is greater than 88%, and the yield is greater than 88%; they all use titanium dioxide as a carrier and add different additives to enhance the activity of the catalyst, but most of the additives have a small surface area and porosity, and the loaded lattice oxygen is less, resulting in low activity of the catalyst, which affects the conversion rate and yield of 2-cyanopyridine.

[0006] Patent CN116078371A uses mesoporous carbon as a carrier, and loads a specific ratio of tin dioxide and antimony trioxide as a catalyst, which improves the conversion rate of 2-methylpyridine raw materials and the selectivity of 2-cyanopyridine products. However, the tin and antimony used in this method are relatively rare, and the acid treatment method is used in the preparation of the catalyst, which will cause equipment corrosion and environmental pollution, and there are certain operational risks. In addition, the preparation of the catalyst takes a long time and the method is more complicated.

[0007] In summary, the existing catalysts for catalytic ammoxidation reaction to prepare 2-cyanopyridine have the following problems: small surface area and porosity of the catalyst promoter, less loaded lattice oxygen, low catalyst activity, environmentally unfriendly preparation process, and affected conversion rate and yield of 2-cyanopyridine. Summary of the invention

[0008] In order to solve the above technical problems, the present invention provides a catalyst for preparing 2-cyanopyridine by catalytic ammoxidation and a preparation method thereof. The present invention uses magnesium oxide-zinc adjuvant as a catalyst adjuvant to prepare a highly active and highly selective catalyst, which can improve the reaction rate and activity, increase the diffusion rate of reactants, and promote the reaction.

[0009] To achieve the above purpose, the technical solution of the present invention is as follows:

[0010] The present invention provides a method for preparing a catalyst for preparing 2-cyanopyridine by catalytic ammoxidation, comprising the following steps:

[0011] Titanium dioxide, V2O5 and magnesium oxide-zinc additive are added into water and stirred to mix evenly, then oxalic acid and ammonium molybdate are added, the temperature is raised to 50-60° C. and stirred to obtain a viscous yellow solid; the yellow solid is dried and calcined to obtain a catalyst for preparing 2-cyanopyridine by catalytic ammoxidation with high efficiency.

[0012] In one embodiment of the present invention, the preparation method of the magnesium oxide-zinc additive is:

[0013] Mg(NO3)2·6H2O, Zn(NO3)2 6H2O and water are stirred and mixed to obtain a mixture; ammonia water and ammonium bicarbonate are then added, and magnesium oxide-zinc additive is obtained by ultrasonication, filtration, drying and sieving;

[0014] Among them, the mass ratio of Mg(NO3)2·6H2O, Zn(NO3)2·6H2O, water, ammonia water and ammonium bicarbonate is (15-35):(20-35):(100-200):(2.0-5.0):(5.0-10); preferably, the mass ratio of Mg(NO3)2·6H2O, Zn(NO3)2·6H2O, water, ammonia water and ammonium bicarbonate is (20-31):(23-33):(130-200):(3.0-4.0):(7.0-9.0).

[0015] The ultrasonic conditions are 25 to 80 KHz for 30 to 60 minutes.

[0016] The drying conditions are 90-110°C for 8-12 hours.

[0017] The particle size after sieving is 60 to 80 μm.

[0018] In one embodiment of the present invention, the addition ratio of titanium dioxide, V2O5, magnesium oxide-zinc additive, water, oxalic acid, and ammonium molybdate is (130-230 g): (25-35 g): (1-7 g): (800-1200 mL): (1-5 g): (1-5 g);

[0019] Preferably, the addition ratio of titanium dioxide, V2O5, magnesium oxide-zinc additive, water, oxalic acid and ammonium molybdate is (150-210g):(25-32g):(2-6g):(800-1200mL):(2-2.5g):(1-2g).

[0020] In one embodiment of the present invention, the heating temperature is 50-60°C.

[0021] In one embodiment of the present invention, the method is:

[0022] Titanium dioxide, V2O5 and magnesium oxide-zinc additive are added to water, stirred for the first time, oxalic acid and ammonium molybdate are added, the temperature is raised to 50-60°C, stirred for the second time, and a viscous yellow solid is obtained; the yellow solid is dried for the first time, extruded to obtain a columnar embryo; dried for the second time, calcined, and cooled to prepare a catalyst for preparing 2-cyanopyridine by catalytic ammoxidation;

[0023] The preparation method of the magnesium oxide-zinc auxiliary agent is as follows: Mg(NO3)2·6H2O, Zn(NO3)2 6H2O and water are stirred and mixed to obtain a mixture; ammonia water and ammonium bicarbonate are added, and the magnesium oxide-zinc auxiliary agent is obtained by ultrasonication, filtration, drying and sieving.

[0024] In one embodiment of the present invention, the mass ratio of Mg(NO3)2·6H2O, Zn(NO3)2·6H2O, water, aqueous ammonia and ammonium bicarbonate is (15-35):(20-35):(100-200):(2.0-5.0):(5.0-10).

[0025] Preferably, the mass ratio of Mg(NO3)2·6H2O, Zn(NO3)2·6H2O, water, aqueous ammonia and ammonium bicarbonate is (20-31):(23-33):(130-200):(3.0-4.0):(7.0-9.0).

[0026] In one embodiment of the present invention, the ultrasonic condition is 25-80KHz for 30-60min.

[0027] In one embodiment of the present invention, the drying condition is drying at 90-110° C. for 8-12 hours.

[0028] In one embodiment of the present invention, the particle size of the magnesium oxide-zinc additive is 60 to 80 μm.

[0029] In one embodiment of the present invention, the specific surface area of ​​the magnesium oxide-zinc additive is 350 to 390 m 2 / g, the porosity is 40% to 60%, and the loaded lattice oxygen content is 6% to 10%.

[0030] In one embodiment of the present invention, the addition ratio of titanium dioxide, V2O5, magnesium oxide-zinc additive, water, oxalic acid, and ammonium molybdate is (130-230 g): (25-35 g): (1-7 g): (800-1200 mL): (1-5 g): (1-5 g);

[0031] Preferably, the addition ratio of titanium dioxide, V2O5, magnesium oxide-zinc additive, water, oxalic acid and ammonium molybdate is (150-210g):(25-32g):(2-6g):(800-1200mL):(2-2.5g):(1-2g).

[0032] In one embodiment of the present invention, the heating temperature is 50-60°C.

[0033] In one embodiment of the present invention, the first stirring condition is stirring at 180-250 r / min for 1-3 hours.

[0034] In one embodiment of the present invention, the second stirring condition is stirring at 200-300 r / min for 10-18 hours.

[0035] In one embodiment of the present invention, the first drying condition is 50-60° C. for 1-3 hours.

[0036] In one embodiment of the present invention, the second drying is performed at 100-110° C. for 2-6 hours.

[0037] In one embodiment of the present invention, the diameter of the columnar embryo is 4 to 5 mm.

[0038] In one embodiment of the present invention, the calcination condition is calcination at 300-800° C. for 14-18 hours.

[0039] In one embodiment of the present invention, the components of the catalyst for catalytic ammoxidation to prepare 2-cyanopyridine and their mass contents are as follows: V: Mo: Mg: Zn: TiO2 = (10-15%): (0.1-2%): (0.1-2%): (0.1-2%): (70%-95%);

[0040] Preferably, the components of the catalyst for catalytic ammoxidation to prepare 2-cyanopyridine and their mass contents are as follows: V:Mo:Mg:Zn:TiO2=(10-15%):(0.8-1.5%):(0.5-1.4%):(0.5-1.5%):(80%-90%).

[0041] The present invention also provides a method for preparing a magnesium oxide-zinc additive for preparing a catalyst, the method comprising:

[0042] Mg(NO3)2·6H2O, Zn(NO3)2 6H2O and water are stirred and mixed to obtain a mixture; ammonia water and ammonium bicarbonate are added, and the mixture is subjected to ultrasonication, filtration, drying and sieving to obtain a magnesium oxide-zinc auxiliary agent.

[0043] In one embodiment of the present invention, the catalyst is a catalyst for catalyzing ammoxidation to prepare 2-cyanopyridine.

[0044] In one embodiment of the present invention, the mass ratio of Mg(NO3)2·6H2O, Zn(NO3)2·6H2O, water, aqueous ammonia and ammonium bicarbonate is (15-35):(20-35):(100-200):(2.0-5.0):(5.0-10).

[0045] Preferably, the mass ratio of Mg(NO3)2·6H2O, Zn(NO3)2·6H2O, water, aqueous ammonia and ammonium bicarbonate is (20-31):(23-33):(130-200):(3.0-4.0):(7.0-9.0).

[0046] In one embodiment of the present invention, the ultrasonic condition is 25-80KHz for 30-60min.

[0047] In one embodiment of the present invention, the drying condition is 90-110° C. for 8-12 hours.

[0048] In one embodiment of the present invention, the particle size of the magnesium oxide-zinc additive is 60 to 80 μm.

[0049] In one embodiment of the present invention, the specific surface area of ​​the magnesium oxide-zinc additive is 350 to 390 m 2 / g, the porosity is 40% to 60%, and the loaded lattice oxygen content is 6% to 10%.

[0050] The present invention also provides a magnesium oxide-zinc auxiliary agent, and the magnesium oxide-zinc auxiliary agent is prepared by the above-mentioned preparation method.

[0051] In one embodiment of the present invention, the particle size of the magnesium oxide-zinc additive is 60 to 80 μm.

[0052] In one embodiment of the present invention, the specific surface area of ​​the magnesium oxide-zinc additive is 350 to 390 m 2 / g, the porosity is 40% to 60%, and the loaded lattice oxygen content is 6% to 10%.

[0053] The present invention also provides a catalyst for preparing 2-cyanopyridine by catalytic ammoxidation, and the catalyst is prepared by using the above preparation method.

[0054] In one embodiment of the present invention, the components of the catalyst for catalytic ammoxidation to prepare 2-cyanopyridine and their mass contents are as follows: V: Mo: Mg: Zn: TiO2 = (10-15%): (0.1-2%): (0.1-2%): (0.1-2%): (70%-95%);

[0055] Preferably, the components of the catalyst for catalytic ammoxidation to prepare 2-cyanopyridine and their mass contents are as follows: V:Mo:Mg:Zn:TiO2=(10-15%):(0.8-1.5%):(0.5-1.4%):(0.5-1.5%):(80%-90%).

[0056] The present invention also provides a method for preparing 2-cyanopyridine, wherein the method uses the above catalyst to carry out an ammoxidation reaction to prepare the 2-cyanopyridine.

[0057] In one embodiment of the present invention, the method is:

[0058] 2-methylpyridine, ammonia and air are mixed in a molar ratio of 1: (40-70): (200-400), the 2-methylpyridine feed rate is 10-30 g / h, 500-550 g of the above catalyst is loaded, and an ammoxidation reaction is carried out to obtain 2-cyanopyridine;

[0059] Preferably, 2-methylpyridine, ammonia and air are mixed in a molar ratio of 1:60:300, and the feed rate of 2-methylpyridine is 21 g / h.

[0060] In one embodiment of the present invention, the mixing condition is 180-220°C.

[0061] In one embodiment of the present invention, the ammoxidation reaction is carried out at a temperature of 300-400°C.

[0062] Beneficial Effects

[0063] (1) The catalyst and magnesium oxide-zinc additive preparation methods of the present invention are simple, low in cost, and suitable for industrial production.

[0064] (2) The catalyst for preparing 2-cyanopyridine by catalytic ammoxidation prepared by the present invention is used to carry out an ammoxidation reaction to prepare 2-cyanopyridine. The results show that the yield of 2-cyanopyridine is ≥91%, the conversion rate is >99.9%, the selectivity of the reaction is >92%, and the production of by-products pyridine and 2-nicotinamide is reduced.

[0065] (3) The catalyst promoter of the present invention has a large surface area and porosity, and carries more lattice oxygen. Adding magnesium oxide-zinc oxide promoter to vanadium oxide to prepare a catalyst can increase the specific surface area of ​​the catalyst, increase the contact area of ​​the reaction, and obtain a higher porosity, which can load more lattice oxygen in the catalyst pores, increase the loading amount of the ammonia oxidation reaction, and thus improve the activity and selectivity of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 The present invention is a flow chart of the preparation process of the magnesium oxide-zinc additive.

[0067] Figure 2 The present invention is a process flow chart for preparing the catalyst. DETAILED DESCRIPTION

[0068] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explaining the present invention and are not used to limit the present invention.

[0069] In the following examples, unless otherwise specified, the materials involved are all commercially available and the solutions mentioned all use water as the solvent.

[0070] The catalysts prepared in the following Examples 1 to 7 have a service life of more than 5 years.

[0071] The determination methods and experimental methods involved in the following examples are as follows:

[0072] 1. Determination method of 2-cyanopyridine yield

[0073] The content of 2-cyanopyridine aqueous solution was determined by high performance liquid chromatography (HPLC) with C18 column as chromatographic condition and 2-cyanopyridine as internal standard;

[0074] The calculation formula of absorption rate is as follows:

[0075]

[0076] In formula (1): γ: 2-cyanopyridine yield; m1: mass of aqueous solution; wt1%: mass content of 2-cyanopyridine; M1: molecular weight of 2-methylpyridine; M2: molecular weight of 2-cyanopyridine; m2: feed amount.

[0077] 2. Determination of 2-methylpyridine conversion rate

[0078] The content of 2-methylpyridine aqueous solution was determined by high performance liquid chromatography (HPLC) with 2-methylpyridine as internal standard.

[0079] The calculation formula of 2-methylpyridine conversion rate is as follows:

[0080]

[0081] In formula (2): α: 2-methylpyridine conversion rate; m1: mass of aqueous solution; wt2%: mass content of 2-methylpyridine; m2: feed amount.

[0082] 3. Determination of the selectivity of 2-cyanopyridine reaction

[0083] The reaction selectivity of the present invention refers to the ability to catalyze the oxidation of ammonia to generate 2-cyanopyridine, thereby reducing the production of side reactions such as pyridine and 2-nicotinamide.

[0084] The calculation formula of 2-cyanopyridine reaction selectivity is as follows:

[0085] 2-Cyanopyridine reaction selectivity = 2-cyanopyridine yield / 2-methylpyridine conversion rate × 100% (3)

[0086] 4. Determination of by-product 2-nicotinamide content

[0087] The content of 2-nicotinamide aqueous solution was determined by high performance liquid chromatography (HPLC) with 2-nicotinamide as internal standard.

[0088] 5. Determination of by-product pyridine content

[0089] The content of pyridine aqueous solution was determined by high performance liquid chromatography (HPLC) with pyridine as internal standard.

[0090] 6. Determination method of specific surface area and porosity of magnesium oxide-zinc additive

[0091] (1) Specific surface area determination method:

[0092] Using BET test method:

[0093] The sample is placed in a system filled with N2 gas, and physical adsorption occurs on the surface of the additive at liquid nitrogen temperature. When the physical adsorption is in equilibrium, the adsorption amount of the monomolecular layer of the additive can be calculated by measuring the adsorption pressure and the flow rate of the adsorbed gas at equilibrium, thereby calculating the specific surface area of ​​the sample. The formula is as follows:

[0094] ①BET equation:

[0095] In formula (4): P: nitrogen partial pressure; P0: saturated vapor pressure of nitrogen at adsorption temperature; V: actual adsorption amount of nitrogen on the sample surface; Vm: saturated adsorption amount of nitrogen monolayer; C: constant related to the adsorption capacity of the sample;

[0096] ② Sg=4.36Vm / W (5)

[0097] In formula (5), Sg is the specific surface area; Vm is the saturated adsorption capacity of nitrogen monolayer; W is the sample weight.

[0098] (2) Porosity determination method:

[0099] The calculation formula for porosity (void ratio) is:

[0100] Porosity = micropore volume of additive / particle volume of additive × 100% (6)

[0101] In formula (6), the micropore volume of the additive can be obtained by pore volume measurement, and the particle volume of the additive can be obtained by density measurement.

[0102] 7. Determination of lattice oxygen content of magnesium oxide-zinc additive loading

[0103] The determination of lattice oxygen can be performed by X-ray photoelectron spectroscopy (XPS). By analyzing the O1s peak, the content of lattice oxygen can be determined.

[0104] The raw materials and equipment involved in the following embodiments are as follows:

[0105] Mg(NO3)2·6H2O, Zn(NO3)2·6H2O, ammonium bicarbonate, V2O5, and oxalic acid were purchased from Sinopharm Reagent Company;

[0106] Ammonia water (purity specification: 25% to 28%) was purchased from Xi'an Sanpu Chemical Reagent Co., Ltd.

[0107] Titanium dioxide was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.;

[0108] Ammonium molybdate was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0109] The muffle furnace was purchased from Changzhou Jintan Jingda Instrument Manufacturing Co., Ltd.;

[0110] The tubular fixed-bed reactor was purchased from Jiangxi Shengshi Times Information Technology Co., Ltd.

[0111] Embodiment 1:

[0112] (1) Preparation of magnesium oxide-zinc additive:

[0113] At room temperature 25°C, 25.6g of Mg(NO3)2·6H2O, 27.3g of Zn(NO3)2 6H2O and 133g of water were stirred for 30 minutes, followed by the addition of 3.5g of ammonia water and 8.0g of ammonium bicarbonate as precipitants, ultrasonication at 30KHz for 40 minutes, vacuum filtration, leaving the precipitated magnesium and zinc metal ions, while separating other ions. Subsequently, the mixture was dried at 100°C for 10 hours, ball milled and sieved to obtain a magnesium oxide-zinc additive (particle size 60-80μm). The preparation process is as follows: Figure 1 shown.

[0114] The specific surface area of ​​the prepared magnesium oxide-zinc additive is 360m 2 / g, the porosity is 47.3%, and the supported lattice oxygen content is 7.3%.

[0115] (2) Preparation of crude catalyst:

[0116] At room temperature of 25°C, 178.3 g of titanium dioxide, 25.2 g of vanadium oxide V2O5, 2.5 g of the magnesium oxide-zinc additive obtained in step (1), and 1000 mL of deionized water were added to a three-necked flask, and stirred at 200 r / min for 2 h. After stirring, 2.5 g of oxalic acid and 2.0 g of ammonium molybdate were added, the temperature was raised to 50°C, and stirred at 230 r / min for 12 h to obtain a viscous yellow solid;

[0117] (3) Drying extrusion:

[0118] The viscous yellow solid obtained in step (2) is dried at 60° C. for 2 h, and then extruded using an extruder to obtain a columnar embryo with a diameter of 4 to 5 mm;

[0119] (4) Preparation of finished catalyst:

[0120] The columnar embryo obtained in step (3) is dried at 100° C. for 4 h, calcined in a muffle furnace at 430° C. for 14 h, and cooled to obtain a catalyst for preparing 2-cyanopyridine by catalytic oxidation of ammonia.

[0121] The mass contents of V, Mo, Mg, Zn and TiO2 components in the catalyst for preparing 2-cyanopyridine by highly efficient catalytic ammoxidation prepared in Example 1 are: V:Mo:Mg:Zn:TiO2=12.0%:0.91%:0.58%:0.62%:84.7%.

[0122] (5) Preparation of 2-cyanopyridine by ammoxidation reaction:

[0123] In a tubular fixed-bed reactor, 2-methylpyridine, ammonia and air were mixed at a molar ratio of 1:45:230 at 200°C, and the feed rate of 2-methylpyridine was 14 g / h. 518 g of the prepared catalyst was loaded, and an ammoxidation reaction was carried out at 340°C. The reaction was stabilized for 2 hours before detection.

[0124] Catalyst preparation process Figure 2 shown.

[0125] Test results:

[0126] The yield of 2-cyanopyridine was 88.92%, the conversion rate of 2-methylpyridine was 99.91%, the reaction selectivity was 89.00%, the content of by-product 2-nicotinamide was 2.12%, and the content of pyridine was 3.34%.

[0127] Embodiment 2:

[0128] (1) Preparation of magnesium oxide-zinc additive:

[0129] At room temperature 25°C, 24.3g of Mg(NO3)2·6H2O, 26.9g of Zn(NO3)2 6H2O and 147g of water were stirred for 30 minutes, followed by the addition of 3.2g of aqueous ammonia and 7.4g of ammonium bicarbonate as precipitants, ultrasonication at 50KHz for 50min, vacuum filtration, and subsequent drying at 110°C for 8h. Magnesium oxide-zinc additive (particle size 60-80μm) was obtained by ball milling and sieving.

[0130] The specific surface area of ​​the prepared magnesium oxide-zinc additive is 367m 2 / g, the porosity is 49.3%, and the supported lattice oxygen content is 7.2%.

[0131] (2) Preparation of crude catalyst:

[0132] At room temperature of 25°C, 200.3 g of titanium dioxide, 25.9 g of vanadium oxide V2O5, 2.6 g of the magnesium oxide-zinc additive obtained in step (1), and 1000 mL of deionized water were added to a three-necked flask, and stirred at 200 r / min for 2 h. After stirring, 2.5 g of oxalic acid and 2.0 g of ammonium molybdate were added, the temperature was raised to 56°C, and stirred at 250 r / min for 14 h to obtain a viscous yellow solid;

[0133] (3) Drying extrusion:

[0134] The viscous yellow solid obtained in step (2) is dried at 60° C. for 2 h, and then extruded using an extruder to obtain a columnar embryo with a diameter of 4 to 5 mm;

[0135] (4) Preparation of finished catalyst:

[0136] The columnar embryo obtained in step (3) is dried at 100° C. for 4 h, calcined in a muffle furnace at 480° C. for 15 h, and cooled to obtain a catalyst for preparing 2-cyanopyridine by catalytic oxidation of ammonia.

[0137] The mass contents of the components in the catalyst for preparing 2-cyanopyridine by highly efficient catalytic ammoxidation prepared in Example 2 are V:Mo:Mg:Zn:TiO2=11.1%:0.88%:0.51%:0.59%:85.6%.

[0138] (5) Preparation of 2-cyanopyridine by ammoxidation reaction:

[0139] In a tubular fixed-bed reactor, 2-methylpyridine, ammonia and air were mixed at a molar ratio of 1:48:240 at 210°C, and the feed rate of 2-methylpyridine was 18 g / h. 530 g of the prepared catalyst was loaded, and ammoxidation reaction was carried out at 345°C. The reaction was stabilized for 2 hours before detection.

[0140] Test results:

[0141] The yield of 2-cyanopyridine was 89.36%, the conversion rate of 2-methylpyridine was 99.96%, the reaction selectivity was 89.39%, the content of by-product 2-nicotinamide was 2.54%, and the content of pyridine was 2.84%.

[0142] Embodiment 3:

[0143] (1) Preparation of magnesium oxide-zinc additive:

[0144] At room temperature 25°C, 30.2 g of Mg(NO3)2·6H2O, 25.3 g of Zn(NO3)2 6H2O and 143 g of water were stirred for 30 min, then 3.8 g of ammonia water and 8.8 g of ammonium bicarbonate were added as precipitants, ultrasonicated at 60 KHz for 60 min, vacuum filtered, then dried at 108°C for 9 h, and ball milled to obtain a magnesium oxide-zinc additive (particle size 60-80 μm);

[0145] The specific surface area of ​​the prepared magnesium oxide-zinc additive is 369m 2 / g, porosity of 52.1%, and supported lattice oxygen content of 8.3%;

[0146] (2) Preparation of crude catalyst:

[0147] At room temperature of 25°C, 198.3 g of titanium dioxide, 26.7 g of vanadium oxide V2O5, 2.8 g of magnesium oxide-zinc additive and 1000 mL of deionized water were added to a three-necked flask and stirred at 220 r / min for 2 h. After stirring, 2.5 g of oxalic acid and 2.0 g of ammonium molybdate were added, the temperature was raised to 60°C and stirred at 250 r / min for 16 h to obtain a viscous yellow solid.

[0148] (3) Drying extrusion:

[0149] The viscous yellow solid obtained in step (2) is dried at 60° C. for 2 h, and then extruded using an extruder to obtain a columnar embryo with a diameter of 4 to 5 mm;

[0150] (4) Preparation of finished catalyst:

[0151] The columnar embryo obtained in step (3) is dried at 100° C. for 4 h, calcined in a muffle furnace at 680° C. for 18 h, and cooled to obtain a catalyst for preparing 2-cyanopyridine by catalytic oxidation of ammonia.

[0152] The mass contents of V, Mo, Mg, Zn and TiO2 components in the catalyst for preparing 2-cyanopyridine by highly efficient catalytic ammoxidation prepared in Example 3 are: V:Mo:Mg:Zn:TiO2=11.5%:0.82%:0.63%:0.57%:85.4%.

[0153] (5) Preparation of 2-cyanopyridine by ammoxidation reaction:

[0154] In a tubular fixed-bed reactor, 2-methylpyridine, ammonia and air were mixed at a ratio of 1:50:250 (molar ratio) at 205°C, and the feed rate of 2-methylpyridine was 16 g / h. 528 g of the prepared catalyst was loaded, and an ammoxidation reaction was carried out at 348°C. The reaction was stabilized for 2 hours before detection.

[0155] Test results:

[0156] The yield of 2-cyanopyridine was 90.84%, the conversion rate of 2-methylpyridine was 99.92%, the reaction selectivity was 90.91%, the content of by-product 2-nicotinamide was 2.84%, and the content of pyridine was 2.11%.

[0157] Embodiment 4:

[0158] (1) Preparation of magnesium oxide-zinc additive:

[0159] At room temperature 25°C, 23.4 g of Mg(NO3)2·6H2O and 32.8 g of Zn(NO3)2 6H2O were stirred and mixed with 193 g of water for 30 min, and then 3.0 g of ammonia water and 8.2 g of ammonium bicarbonate were added as precipitants, ultrasonicated at 80 KHz for 30 min, vacuum filtered, and then dried at 102°C for 10 h, and ball milled to obtain a magnesium oxide-zinc additive (particle size 60-80 μm);

[0160] The specific surface area of ​​the prepared magnesium oxide-zinc additive is 372m 2 / g, porosity of 51.2%, and supported lattice oxygen content of 8.0%;

[0161] (2) Preparation of crude catalyst:

[0162] At room temperature of 25°C, 168.4 g of titanium dioxide, 27.2 g of vanadium oxide V2O5, 3.0 g of magnesium oxide-zinc additive and 1000 mL of deionized water were added to a three-necked flask and stirred at 240 r / min for 2 h. After stirring, 2.5 g of oxalic acid and 2.0 g of ammonium molybdate were added, the temperature was raised to 53°C and stirred at 280 r / min for 12 h to obtain a viscous yellow solid.

[0163] (3) Drying extrusion:

[0164] The viscous yellow solid obtained in step (2) is dried at 60° C. for 2 h, and then extruded using an extruder to obtain a columnar embryo with a diameter of 4 to 5 mm;

[0165] (4) Preparation of finished catalyst:

[0166] The columnar embryo obtained in step (3) is dried at 100° C. for 4 h, calcined in a muffle furnace at 730° C. for 16 h, and cooled to obtain a catalyst for preparing 2-cyanopyridine by catalytic oxidation of ammonia.

[0167] The mass contents of V, Mo, Mg, Zn and TiO2 components in the catalyst for preparing 2-cyanopyridine by highly efficient catalytic ammoxidation prepared in Example 4 are: V:Mo:Mg:Zn:TiO2=13.4%:0.98%:0.66%:0.82%:82.9%.

[0168] (5) Preparation of 2-cyanopyridine by ammoxidation reaction:

[0169] In a tubular fixed-bed reactor, 2-methylpyridine, ammonia and air were mixed at a molar ratio of 1:55:280 at 208°C, and the feed rate of 2-methylpyridine was 20 g / h. 540 g of the prepared catalyst was loaded, and an ammoxidation reaction was carried out at 350°C. The reaction was stabilized for 2 hours before detection.

[0170] Test results:

[0171] The yield of 2-cyanopyridine was 91.36%, the conversion rate of 2-methylpyridine was 99.92%, the reaction selectivity was 91.43%, the content of by-product 2-nicotinamide was 2.32%, and the content of pyridine was 3.08%.

[0172] Embodiment 5:

[0173] (1) Preparation of magnesium oxide-zinc additive:

[0174] At room temperature 25°C, 28.3 g of Mg(NO3)2·6H2O and 23.3 g of Zn(NO3)2 6H2O were stirred and mixed with 130 g of water for 30 min, and then 3.4 g of ammonia water and 8.5 g of ammonium bicarbonate were added as precipitants, ultrasonicated at 70 KHz for 55 min, vacuum filtered, and then dried at 106°C for 10 h, and ball milled to obtain a magnesium oxide-zinc additive (particle size 60-80 μm);

[0175] The specific surface area of ​​the prepared magnesium oxide-zinc additive is 375m 2 / g, porosity of 50.7%, and supported lattice oxygen content of 8.9%;

[0176] (2) Preparation of crude catalyst:

[0177] At room temperature of 25°C, 202.6 g of titanium dioxide, 30.2 g of vanadium oxide V2O5, 5.2 g of magnesium oxide-zinc additive and 1000 mL of deionized water were added to a three-necked flask and stirred at 200 r / min for 2 h. After stirring, 2.5 g of oxalic acid and 2.0 g of ammonium molybdate were added, the temperature was raised to 54°C and stirred at 230 r / min for 17 h to obtain a viscous yellow solid.

[0178] (3) Drying extrusion:

[0179] The viscous yellow solid obtained in step (2) is dried at 60° C. for 2 h, and then extruded using an extruder to obtain a columnar embryo with a diameter of 4 to 5 mm;

[0180] (4) Preparation of finished catalyst:

[0181] The columnar embryo obtained in step (3) is dried at 100° C. for 4 h, calcined in a muffle furnace at 570° C. for 16 h, and cooled to obtain a catalyst for preparing 2-cyanopyridine by catalytic oxidation of ammonia.

[0182] The mass contents of V, Mo, Mg, Zn and TiO2 components in the catalyst for preparing 2-cyanopyridine by highly efficient catalytic ammoxidation prepared in Example 5 are: V:Mo:Mg:Zn:TiO2=12.5%:0.88%:1.02%:1.08%:83.5%.

[0183] (5) Preparation of 2-cyanopyridine by ammoxidation reaction:

[0184] In a tubular fixed-bed reactor, 2-methylpyridine, ammonia and air were mixed at a ratio of 1:60:300 (molar ratio) at 210°C, and the feed rate of 2-methylpyridine was 21 g / h. 541 g of the prepared catalyst was loaded, and an ammoxidation reaction was carried out at 335°C. The reaction was stabilized for 2 hours before detection.

[0185] Test results:

[0186] The yield of 2-cyanopyridine was 91.92%, the conversion rate of 2-methylpyridine was 99.90%, the reaction selectivity was 92.01%, the content of by-product 2-nicotinamide was 2.92%, and the content of pyridine was 2.01%.

[0187] Embodiment 6:

[0188] (1) Preparation of magnesium oxide-zinc additive:

[0189] At room temperature 25°C, 23.3 g of Mg(NO3)2·6H2O and 25.3 g of Zn(NO3)2 6H2O were stirred and mixed with 150 g of water for 30 min, and then 3.2 g of ammonia water and 9.0 g of ammonium bicarbonate were added as precipitants, ultrasonicated at 40 KHz for 45 min, vacuum filtered, and then dried at 104°C for 8 h, and ball milled to obtain a magnesium oxide-zinc additive (particle size 60-80 μm);

[0190] The specific surface area of ​​the prepared magnesium oxide-zinc additive is 365m 2 / g, porosity of 49.3%, and supported lattice oxygen content of 7.8%;

[0191] (2) Preparation of crude catalyst:

[0192] At room temperature of 25°C, 170.9 g of titanium dioxide, 31.6 g of vanadium oxide V2O5, 5.9 g of magnesium oxide-zinc additive and 1000 mL of deionized water were added to a three-necked flask, stirred at 190 r / min for 2 h, and after stirring, 2.5 g of oxalic acid and 2.0 g of ammonium molybdate were added, the temperature was raised to 58°C and stirred at 290 r / min for 16 h to obtain a viscous yellow solid;

[0193] (3) Drying extrusion:

[0194] The viscous yellow solid obtained in step (2) is dried at 60° C. for 2 h, and then extruded using an extruder to obtain a columnar embryo with a diameter of 4 to 5 mm;

[0195] (4) Preparation of finished catalyst:

[0196] The columnar embryo obtained in step (3) is dried at 100° C. for 4 h, calcined in a muffle furnace at 550° C. for 18 h, and cooled to obtain a catalyst for preparing 2-cyanopyridine by catalytic oxidation of ammonia.

[0197] The mass contents of V, Mo, Mg, Zn and TiO2 components in the catalyst for preparing 2-cyanopyridine by highly efficient catalytic ammoxidation prepared in Example 6 are: V:Mo:Mg:Zn:TiO2=14.8%:1.42%:1.3%:0.9%:79.89%.

[0198] (5) Preparation of 2-cyanopyridine by ammoxidation reaction:

[0199] In a tubular fixed-bed reactor, 2-methylpyridine, ammonia and air were mixed at a ratio of 1:65:320 (molar ratio) at 202°C, and the feed rate of 2-methylpyridine was 25 g / h. 544 g of the prepared catalyst was loaded, and an ammoxidation reaction was carried out at 338°C. The reaction was stabilized for 2 hours before detection.

[0200] Test results:

[0201] The yield of 2-cyanopyridine was 89.11%, the conversion rate of 2-methylpyridine was 99.91%, the reaction selectivity was 89.19%, the content of by-product 2-nicotinamide was 2.13%, and the content of pyridine was 3.82%.

[0202] Embodiment 7:

[0203] (1) Preparation of magnesium oxide-zinc additive:

[0204] At room temperature 25°C, 20.3 g of Mg(NO3)2·6H2O and 23.9 g of Zn(NO3)2 6H2O were stirred and mixed with 160 g of water for 30 min, and then 3.3 g of ammonia water and 8.2 g of ammonium bicarbonate were added as precipitants, ultrasonicated at 65 KHz for 35 min, vacuum filtered, and then dried at 106°C for 9 h, and ball milled to obtain a magnesium oxide-zinc additive (particle size 60-80 μm);

[0205] The specific surface area of ​​the prepared magnesium oxide-zinc additive is 363m 2 / g, porosity of 52.3%, and supported lattice oxygen content of 8.0%;

[0206] (2) Preparation of crude catalyst:

[0207] At room temperature of 25°C, 158.3g of titanium dioxide, 26.4g of vanadium oxide V2O5, 5.1g of magnesium oxide-zinc additive and 1000mL of deionized water were added to a three-necked flask and stirred at 200r / min for 2h. After stirring, 2.5g of oxalic acid and 2.0g of ammonium molybdate were added, the temperature was raised to 57°C and stirred at 260r / min for 18h to obtain a viscous yellow solid.

[0208] (3) Drying extrusion:

[0209] The viscous yellow solid obtained in step (2) is dried at 60° C. for 2 h, and then extruded using an extruder to obtain a columnar embryo with a diameter of 4 to 5 mm;

[0210] (4) Preparation of finished catalyst:

[0211] The columnar embryo obtained in step (3) is dried at 100° C. for 4 h, calcined in a muffle furnace at 600° C. for 18 h, and cooled to obtain a catalyst for preparing 2-cyanopyridine by catalytic oxidation of ammonia.

[0212] The mass contents of V, Mo, Mg, Zn and TiO2 components in the catalyst for preparing 2-cyanopyridine by highly efficient catalytic ammoxidation prepared in Example 7 are: V:Mo:Mg:Zn:TiO2=12.4%:0.90%:1.16%:1.24%:83.12%.

[0213] (5) Preparation of 2-cyanopyridine by ammoxidation reaction:

[0214] In a tubular fixed-bed reactor, 2-methylpyridine, ammonia and air were mixed at a ratio of 1:58:310 (molar ratio) at 204°C, and the feed rate of 2-methylpyridine was 24 g / h. 550 g of the prepared catalyst was loaded, and an ammoxidation reaction was carried out at 343°C. The reaction was stabilized for 2 hours before detection.

[0215] Test results:

[0216] The yield of 2-cyanopyridine was 88.89%, the conversion rate of 2-methylpyridine was 99.93%, the reaction selectivity was 88.95%, the content of by-product 2-nicotinamide was 2.45%, and the content of pyridine was 2.95%.

[0217] Comparative Example 1:

[0218] The specific implementation method is the same as that of Example 5, except that magnesium oxide-zinc additive is not used, that is, step (1) is deleted and step (2) is adjusted to:

[0219] At room temperature of 25°C, add 202.6 g of titanium dioxide, 30.2 g of V2O5 and 1000 mL of deionized water into a three-necked flask and stir at 200 r / min for 2 h. After stirring, add 2.5 g of oxalic acid and 2.0 g of ammonium molybdate. Heat to 54°C and stir at 230 r / min for 17 h to obtain a viscous yellow solid.

[0220] The other conditions were the same as those in Example 5, and a catalyst for catalytic ammoxidation to prepare 2-cyanopyridine was prepared.

[0221] The mass contents of V, Mo and TiO2 components in the catalyst for preparing 2-cyanopyridine by catalytic ammoxidation prepared in this comparative example are V:Mo:TiO2=12.7%:0.87%:85.4%.

[0222] Comparative Example 2:

[0223] The specific implementation method is the same as that of Example 5, except that the magnesium oxide-zinc additive in the adjustment step (1) is a single magnesium oxide additive, that is, the adjustment step (1) is:

[0224] (1) Preparation of single magnesium oxide additive:

[0225] At room temperature of 25°C, 32.8 g of magnesium chloride was dissolved in 200 mL of water, and 27.6 g of sodium hydroxide was added to precipitate magnesium hydroxide. The precipitate was vacuum filtered, dried at 100°C for 4 h, and calcined at 400°C for 10 h to obtain a magnesium oxide additive.

[0226] The specific surface area of ​​the single magnesium oxide additive prepared in this comparative example is 220 m 2 / g, the porosity is 34.2%, and the supported lattice oxygen content is 5.2%.

[0227] The other conditions were the same as those in Example 5, and a catalyst for catalytic ammoxidation to prepare 2-cyanopyridine was prepared.

[0228] The mass contents of V, Mo, Mg and TiO2 components in the catalyst for preparing 2-cyanopyridine by catalytic ammoxidation prepared in this comparative example are V:Mo:Mg:TiO2=12.5%:0.86%:2.1%:83.5%.

[0229] Comparative Example 3:

[0230] Compared with Example 5, the magnesium oxide-zinc additive was changed to a single zinc oxide additive, and the rest was consistent with Example 5:

[0231] The specific implementation method is the same as that of Example 5, except that the magnesium oxide-zinc additive in the adjustment step (1) is a single zinc oxide additive, that is, the adjustment step (1) is:

[0232] (1) Preparation of zinc oxide additive:

[0233] At room temperature of 25°C, 28.9 g of zinc chloride was dissolved in 200 mL of water, and 18.2 g of sodium hydroxide was added to precipitate zinc hydroxide. The precipitate was vacuum filtered, dried at 100°C for 4 h, and calcined at 400°C for 10 h to obtain a zinc oxide additive.

[0234] The specific surface area of ​​the single zinc oxide additive prepared in this comparative example is 208m 2 / g, the porosity is 30.2%, and the supported lattice oxygen content is 3.4%.

[0235] The other conditions were the same as those in Example 5, and a catalyst for catalytic ammoxidation to prepare 2-cyanopyridine was prepared.

[0236] The mass contents of V, Mo, Mg and TiO2 components in the catalyst for preparing 2-cyanopyridine by catalytic ammoxidation prepared in this comparative example are V:Mo:Mg:TiO2=12.5%:0.85%:2.1%:83.5%.

[0237] Comparative Example 4:

[0238] The specific implementation method is the same as Example 5, except that the preparation of the auxiliary agent in step (1) is adjusted to use Ni(NO3)2·6H2O and Cu(NO3)2·H2O to prepare the catalyst auxiliary agent, that is, the adjustment step (1) is:

[0239] (1) Preparation of nickel oxide-copper additive:

[0240] At room temperature 25°C, 32.1g of Ni(NO3)2·6H2O and 22.8g of Cu(NO3)2·H2O were stirred and mixed with 140g of water for 30min, then 3.4g of ammonia water and 8.5g of ammonium bicarbonate were added as precipitants, and ultrasonic treatment was performed at 70KHz for 55min to precipitate the mixture, and the precipitate was obtained by centrifugation. Then, the mixture was dried at 106°C for 10h, and the nickel oxide-copper additive was obtained by ball milling and sieving.

[0241] The specific surface area of ​​the nickel oxide-copper additive prepared in this comparative example is 345m 2 / g, the porosity is 38.4%, and the supported lattice oxygen content is 5.2%.

[0242] The other conditions were the same as those in Example 5, and a catalyst for catalytic ammoxidation to prepare 2-cyanopyridine was prepared.

[0243] The mass contents of V, Mo, Ni, Cu and TiO2 components in the catalyst for preparing 2-cyanopyridine by catalytic ammoxidation prepared in this comparative example are V:Mo:Ni:Cu:TiO2=12.5%:0.83%:1.1.07%:1.03%:83.5%.

[0244] Comparative Example 5:

[0245] Compared with Example 5, the preparation method of the magnesium oxide-zinc additive was changed, and the rest was consistent with Example 5:

[0246] The specific implementation method is the same as that of Example 5, except that the Mg(NO3)2·6H2O in step (1) is adjusted to be another magnesium compound MgSO4; and the Zn(NO3)2 6H2O is adjusted to be another zinc compound ZnSO4·4H2O; that is, step (1) is adjusted to:

[0247] (1) Preparation of magnesium oxide-zinc additive:

[0248] At room temperature of 25°C, 25.8 g of MgSO4, 29.6 g of ZnSO4·4H2O and 130 g of water were stirred for 30 min, and then 3.4 g of ammonia water and 8.5 g of ammonium bicarbonate precipitant were added, ultrasonicated at 70 KHz for 55 min, vacuum filtered, and then dried at 106°C for 10 h, and ball milled and sieved to obtain a magnesium oxide-zinc additive;

[0249] The specific surface area of ​​the magnesium oxide-zinc additive prepared in this comparative example is 326 m 2 / g, the porosity is 35.3%, and the supported lattice oxygen content is 4.6%.

[0250] The other conditions were the same as those in Example 5, and a catalyst for catalytic ammoxidation to prepare 2-cyanopyridine was prepared.

[0251] The mass contents of V, Mo, Mg, Zn and TiO2 components in the catalyst for catalytic ammoxidation to prepare 2-cyanopyridine prepared in this comparative example are V:Mo:Mg:Zn:TiO2=12.5%:0.82%:1.42%:0.68%:83.5%.

[0252] Comparative Example 6:

[0253] The specific implementation method is the same as that of Example 5, except that the preparation of the crude catalyst in step (2) is adjusted to use V2O3 instead of V2O5 to prepare the crude catalyst, that is, step (2) is adjusted to:

[0254] (2) Preparation of crude catalyst:

[0255] At room temperature of 25°C, add 202.6g of titanium dioxide, 30.2g of V2O3, 5.2g of magnesium oxide-zinc additive and 1000mL of deionized water into a three-necked flask and stir for 2h. After stirring, add 2.5g of oxalic acid and 2.0g of ammonium molybdate, heat to 54°C and stir for 17h to obtain a viscous yellow solid.

[0256] The mass contents of V, Mo, Mg, Zn and TiO2 components in the catalyst for catalytic ammoxidation to prepare 2-cyanopyridine prepared in this comparative example are V:Mo:Mg:Zn:TiO2=12.1%:0.83%:1.03%:1.10%:83.5%.

[0257] The catalyst obtained in Comparative Examples 1-6 is used for an ammoxidation reaction to prepare 2-cyanopyridine, which specifically comprises the following steps:

[0258] In a tubular fixed-bed reactor, 2-methylpyridine, ammonia and air were mixed at a molar ratio of 1:60:300 at 210°C, and the 2-methylpyridine feed rate was 21 g / h; 541 g of the catalyst prepared in the above comparative examples 1 to 6 were respectively filled, and ammoxidation reaction was carried out at 335°C. The reaction was stabilized for 2 hours before detection.

[0259] The yield of 2-cyanopyridine, the conversion rate of 2-methylpyridine, the reaction selectivity, the content of by-product 2-nicotinamide, and the content of pyridine are shown in Table 1.

[0260] Table 1

[0261] Comparative Example 2-Cyanopyridine yield% 2-Methylpyridine conversion rate % 2-Niacinamide content% Pyridine content% Reaction selectivity% 1 52.83 84.32 30.42 23.78 62.65 2 63.27 90.42 13.66 11.28 69.97 3 72.62 90.84 10.82 5.62 79.94 4 77.46 94.21 14.22 8.36 82.22 5 84.17 98.36 8.67 5.43 85.57 6 68.28 93.22 16.73 9.74 73.25

[0262] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A method for preparing a catalyst for catalytic ammoxidation to prepare 2-cyanopyridine, characterized in that: The steps include: Titanium dioxide, V2O5 and magnesium oxide-zinc additive are added into water and stirred to mix evenly, and then oxalic acid and ammonium molybdate are added, and the temperature is raised to 50-60° C. and stirred to obtain a viscous yellow solid; the yellow solid is dried and calcined to obtain a catalyst for catalytic ammoxidation to prepare 2-cyanopyridine; Among them, the addition ratio of titanium dioxide, V2O5, magnesium oxide-zinc additive, water, oxalic acid, and ammonium molybdate is (130-230g):(25-35g):(1-7g):(800-1200mL):(1-5g):(1-5g); The preparation method of magnesium oxide-zinc additive is as follows: Mg(NO3)2·6H2O, Zn(NO3)2 6H2O and water are stirred and mixed to obtain a mixture; then ammonia water and ammonium bicarbonate are added, and magnesium oxide-zinc additive is obtained by ultrasonication, filtration, drying and screening; wherein the mass ratio of Mg(NO3)2·6H2O, Zn(NO3)2·6H2O, water, ammonia water and ammonium bicarbonate is (15-35): (20-35): (100-200): (2.0-5.0): (5.0-10).

2. The preparation method according to claim 1, characterized in that: The addition ratio of titanium dioxide, V2O5, magnesium oxide-zinc additive, water, oxalic acid and ammonium molybdate is (150-210g):(25-32g):(2-6g):(800-1200mL):(2-2.5g):(1-2g).

3. The preparation method according to claim 1 or 2, characterized in that: The mass ratio of Mg(NO3)2·6H2O, Zn(NO3)2·6H2O, water, aqueous ammonia and ammonium bicarbonate is (20-31):(23-33):(130-200):(3.0-4.0):(7.0-9.0).

4. The preparation method according to claim 1, characterized in that: The specific steps include: Titanium dioxide, V2O5 and magnesium oxide-zinc additive are added to water, stirred for the first time, oxalic acid and ammonium molybdate are added, the temperature is raised to 50-60°C, stirred for the second time, and a viscous yellow solid is obtained; the yellow solid is dried for the first time, extruded to obtain a columnar embryo; dried for the second time, calcined, and cooled to obtain a catalyst for catalytic ammoxidation to prepare 2-cyanopyridine; Among them, the addition ratio of titanium dioxide, V2O5, magnesium oxide-zinc additive, water, oxalic acid, and ammonium molybdate is (130-230g):(25-35g):(1-7g):(800-1200mL):(1-5g):(1-5g); The preparation method of the magnesium oxide-zinc auxiliary agent is as follows: Mg(NO3)2·6H2O, Zn(NO3)2 6H2O and water are stirred and mixed to obtain a mixture; ammonia water and ammonium bicarbonate are added, and the magnesium oxide-zinc auxiliary agent is obtained by ultrasonication, filtration, drying and screening; wherein the mass ratio of Mg(NO3)2·6H2O, Zn(NO3)2·6H2O, water, ammonia water and ammonium bicarbonate is (15-35): (20-35): (100-200): (2.0-5.0): (5.0-10).

5. A method for preparing a magnesium oxide-zinc additive for preparing a catalyst, characterized in that: The steps include: Mg(NO3)2·6H2O, Zn(NO3)2 6H2O and water are stirred and mixed to obtain a mixture; ammonia water and ammonium bicarbonate are added, and magnesium oxide-zinc additive is obtained by ultrasonication, filtration, drying and sieving; Among them, the mass ratio of Mg(NO3)2·6H2O, Zn(NO3)2·6H2O, water, ammonia water and ammonium bicarbonate is (15-35):(20-35):(100-200):(2.0-5.0):(5.0-10).

6. The magnesium oxide-zinc additive prepared by the method according to claim 5.

7. A catalyst for preparing 2-cyanopyridine by catalytic ammoxidation prepared by the method according to any one of claims 1 to 4.

8. A method for preparing 2-cyanopyridine, characterized in that: The method uses the catalyst described in claim 7 to carry out ammoxidation reaction to prepare the product.

9. The method according to claim 8, characterized in that The steps include: 2-methylpyridine, ammonia and air are mixed, loaded with the catalyst according to claim 7, and subjected to an ammoxidation reaction to obtain 2-cyanopyridine.

10. The method according to claim 8 or 9, characterized in that: The specific steps include: 2-Methylpyridine, ammonia and air are mixed in a molar ratio of 1:(40-70):(200-400); the 2-methylpyridine feed rate is 10-30 g / h; and 500-550 g of the catalyst according to claim 7 is filled.

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