Phthalonitrile catalyst and preparation method thereof

Abstract

The invention provides a phthalonitrile catalyst and a preparation method thereof, and belongs to the technical field of organic synthesis catalysts. Metal oxides such as vanadium, titanium and molybdenum are used as active components. The vanadium oxide has a good ammoxidation active center and can promote activation of methyl in o-xylene and the ammoxidation reaction process; the titanium oxide is beneficial to improving the structural stability of the catalyst, and the unique crystal structure and electronic characteristics of the titanium oxide can effectively disperse the active components and prevent sintering of the active components, so that the service life of the catalyst is prolonged; molybdenum oxide plays a key role in adjusting the oxidation-reduction performance of the catalyst, and can optimize the electron transfer path in the reaction process and improve the selectivity of the reaction. Through the synergistic effect of the three components, the catalyst shows excellent performance in the o-xylene ammoxidation reaction, and has important significance.

Description

Technical Field

[0001] The present invention relates to the technical field of organic synthesis catalysts, and particularly relates to a phthalonitrile catalyst and a preparation method thereof. Background Art

[0002] Phthalonitrile is an important organic chemical intermediate, which is widely used in fields such as dyes, pesticides, pharmaceuticals, and polymer materials. At present, the industrial production of phthalonitrile mainly adopts the ammoxidation method of o-xylene. This method has the advantages of cheap and easily available raw materials and relatively simple process flow. However, this reaction process faces many challenges. For example, it is difficult for the existing catalysts to break through a relatively high conversion rate of o-xylene, generally only reaching about 85% - 90%. This is mainly because the active center structure of the traditional catalyst is not optimized enough, and the activation ability of the methyl group in the o-xylene molecule is insufficient, resulting in some o-xylene not fully participating in the ammoxidation reaction. For example, in the reaction process of a single vanadium oxide catalyst, the electron cloud distribution of the vanadium active center is not reasonable enough, making the adsorption and reaction efficiency of o-xylene with the active center relatively low, thus limiting the further improvement of the conversion rate. The selectivity of phthalonitrile is usually between 80% - 85%, and there are many by-products generated. This is because the regulation of the redox performance of the traditional catalyst is not precise enough. During the ammoxidation of o-xylene, over-oxidation or other side reactions are likely to occur. For example, when the reaction temperature is slightly higher or the ratio of ammonia to o-xylene is unbalanced, in addition to phthalonitrile, nitrile derivatives formed by further oxidation of the cyano group, phthalic anhydride and other by-products will be produced. These by-products not only reduce the yield of the target product, but also increase the difficulty and cost of subsequent separation and purification. During the long-term operation of the traditional catalyst, the activity and selectivity will gradually decrease. On the one hand, the active components are prone to sintering or loss under high-temperature reaction conditions. For example, during the long-term ammoxidation reaction, the vanadium oxide may undergo a phase transformation, resulting in the destruction of the active center structure and a reduction in the number of active sites. On the other hand, the interaction between the carrier and the active components is not strong enough. Under the scouring of the reaction gas flow and the action of the reaction heat, the active components are easily detached from the surface of the carrier, deteriorating the performance of the catalyst. Generally, after the traditional catalyst operates continuously for 500 - 800 hours, the conversion rate of o-xylene may decrease by 5% - 10%, and the selectivity of phthalonitrile decreases by 3% - 8%. It is necessary to frequently replace the catalyst, increasing the production cost and the risk of production interruption. Therefore, the development of efficient and stable catalysts is of great significance for the process of ammoxidizing o-xylene to phthalonitrile. Summary of the Invention

[0003] The object of the present invention is to provide a phthalonitrile catalyst and a preparation method thereof, which are used to solve the technical problems in the prior art that the catalytic efficiency of the ammoxidation reaction of o-xylene, the yield and selectivity of phthalonitrile are not high, and the thermal stability and service life of the phthalonitrile catalyst are insufficient.

[0004] In order to achieve the above object of the invention, the present invention provides the following technical solutions:

[0005] The present invention provides a phthalonitrile catalyst, and the chemical general formula of the phthalonitrile catalyst is V a Ti b Mo c O d , where 3 ≤ a ≤ 5, 2 ≤ b ≤ 4, 1 ≤ c ≤ 7, 5 ≤ d ≤ 27.

[0006] The present invention provides a preparation method of a phthalonitrile catalyst, which includes the following steps:

[0007] Step 1), mixing a vanadium salt solution, a titanium dispersion system, a molybdenum salt solution and an alkaline solution, and carrying out a coprecipitation reaction to obtain a precipitate;

[0008] Step 2), subjecting the obtained precipitate to aging, filtration, washing, drying, calcination and activation in sequence to obtain a phthalonitrile catalyst.

[0009] Further, in step 1), the concentration of the vanadium salt solution is 0.1 - 3 mol / L, the concentration of the titanium dispersion system is 0.05 - 3 mol / L, the concentration of the molybdenum salt solution is 0.01 - 5 mol / L, and the concentration of the alkaline solution is 0.2 - 3 mol / L;

[0010] In step 1), the temperature of the coprecipitation reaction is 32 - 45 °C;

[0011] In step 2), the temperature of the aging is 65 - 85 °C, and the aging time is 6 - 8 h;

[0012] The drying temperature is 110 - 150 °C, and the drying time is 10 - 15 h;

[0013] The calcination temperature is 450 - 650 °C, the calcination time is 3 - 5 h, and the heating rate is 3 - 7 °C / min;

[0014] In step 2), the activation is carried out in a nitrogen atmosphere, the activation temperature is 400 - 480 °C, and the activation time is 2 - 5 h.

[0015] The present invention provides a preparation method of a phthalonitrile catalyst, which includes the following steps:

[0016] Step a): Mix vanadium pentoxide, titanium dioxide, molybdenum trioxide and oxalic acid solution to obtain a mixed metal salt impregnation solution;

[0017] Step b): Immerse the pretreated carrier in the mixed metal salt impregnation solution, and then sequentially dry, calcine and activate the obtained material to obtain a phthalonitrile catalyst.

[0018] Further, in step a), the concentration of the oxalic acid solution is 1 - 1.5 mol / L, and the dosage ratio of vanadium pentoxide to the oxalic acid solution is 30 - 50 g: 800 mL.

[0019] Further, in step b), the pretreatment is to calcine the carrier at 500 - 600 °C for 2.5 - 4 h. The carrier includes alumina and / or silica, and the dosage ratio of the mixed metal salt impregnation solution to the carrier is 800 - 1000 mL: 1000 - 1400 g;

[0020] The specific surface area of the carrier is 180 - 220 m 2 / g, the pore volume is 0.3 - 0.7 cm 3 / g, and the average pore diameter is 8 - 12 nm;

[0021] The drying temperature is 110 - 150 °C, and the drying time is 8 - 12 h;

[0022] The calcination temperature is 550 - 600 °C, the calcination time is 3 - 7 h, and the heating rate is 5 - 10 °C / min;

[0023] The activation temperature is 400 - 500 °C, and the activation time is 1.5 - 4 h.

[0024] The present invention provides a preparation method of a phthalonitrile catalyst, including the following steps:

[0025] Step 1): Mix vanadyl acetylacetonate and isopropanol to obtain a vanadium sol;

[0026] Step 2): Mix isopropyl titanate, isopropanol and water, and obtain a titanium sol under the catalysis of concentrated hydrochloric acid;

[0027] Step 3): Sequentially mix the titanium sol and ammonium heptamolybdate solution with the vanadium sol and then carry out a gelation reaction, and then sequentially dry, calcine and activate the obtained gel to obtain a phthalonitrile catalyst.

[0028] Further, in step 1), the dosage ratio of vanadyl acetylacetonate to isopropanol is 20 - 50 g: 400 mL;

[0029] In step 1), the mixing is carried out under stirring, the stirring temperature is 23 - 32 °C, and the stirring time is 0.5 - 2 h.

[0030] Further, in step (ii), the dosage ratio of isopropyl titanate, isopropanol and water is 30 - 50 g: 180 - 220 mL: 80 - 120 mL, and the dosage ratio of isopropyl titanate and concentrated hydrochloric acid is 30 - 50 g: 4 - 7 mL;

[0031] In step (ii), the mixing is carried out under stirring, the temperature of stirring is 23 - 32 °C, and the time of stirring is 1 - 3 h.

[0032] Further, in step (iii), the mixing is carried out during stirring, the temperature of the gelation reaction is 55 - 65 °C, and the time is 1.5 - 3 h;

[0033] In step (iii), the temperature of drying is 90 - 120 °C, and the time of drying is 18 - 25 h;

[0034] In step (iii), the temperature of calcination is 450 - 500 °C, the time of calcination is 5 - 8 h, and the heating rate is 5 - 8 °C / min;

[0035] In step (iii), the temperature of activation is 400 - 450 °C, and the time of activation is 3 - 6 h.

[0036] Advantages of the present invention:

[0037] The catalyst of the present invention uses metal oxides such as vanadium (V), titanium (Ti), and molybdenum (Mo) as active components. Vanadium oxide has good ammonia oxidation active centers, which can promote the activation of methyl groups in o - xylene and the ammonia oxidation reaction process; titanium oxide helps to improve the structural stability of the catalyst, and its unique crystal structure and electronic properties can effectively disperse the active components, preventing the sintering of the active components, thereby prolonging the service life of the catalyst; molybdenum oxide plays a key role in regulating the redox performance of the catalyst, can optimize the electron transfer path during the reaction, and improve the selectivity of the reaction. There is a synergistic effect among the three, making the catalyst show excellent performance in the ammonia oxidation reaction of o - xylene.

[0038] The present invention selects alumina (Al2O3), silica (SiO2) or their composite carriers, and pre - treats and modifies the carriers. By controlling the specific surface area of the carrier (for example, in the range of [lower specific surface area value] - [upper specific surface area value] m 2 / g), pore volume ([lower pore volume value] - [upper pore volume value] cm 3 / g) and the average pore diameter ([lower limit of average pore diameter]-[upper limit of average pore diameter] nm), providing a suitable dispersion environment for the active component, increasing the exposure number of active sites, while ensuring good diffusion performance of reactants and products in the catalyst pores, reducing the occurrence of side reactions, and improving the selectivity of phthalonitrile.

[0039] In the ammoxidation reaction of o-xylene, using the catalyst prepared by the present invention, the conversion rate of o-xylene can be as high as over 99.5%. For example, under typical reaction conditions (such as the molar ratio of o-xylene to ammonia and air being 1:8:40, reaction temperature 400 °C, pressure 0.1 MPa, and the space velocity of the mixed gas being 2000 h -1 ), after multiple repeated experiments, the conversion rate of o-xylene is stably maintained between 99% and 99.8%, showing a significant improvement compared with traditional catalysts (the conversion rate is generally between 85% and 90%).

[0040] The selectivity of phthalonitrile is also greatly improved, reaching over 88%. Under the same reaction conditions as above, the selectivity of phthalonitrile can reach 88% - 92%, while the selectivity of traditional catalysts is usually only 80% - 85%. High selectivity means a significant reduction in the amount of by-products generated, not only reducing the cost of subsequent separation and purification, but also improving the quality and purity of the product, making the product more in line with the application requirements of the high-end chemical industry.

[0041] The catalyst of the present invention exhibits excellent stability and can maintain good catalytic performance during long-term continuous operation. In the 1000-hour stability test, the conversion rate only decreased from the initial 99.5% to 99.0%, and the selectivity decreased from 90% to 89.5%. This indicates that the active component of the catalyst is not easily lost and the structure does not change significantly during long-term operation, effectively reducing problems such as increased production costs and production interruptions caused by frequent catalyst replacement, and significantly improving production efficiency and economic benefits. Detailed implementation mode

[0042] The present invention provides a phthalonitrile catalyst, and the chemical general formula of the phthalonitrile catalyst is V a Ti b Mo c O d , where 3 ≤ a ≤ 5, 2 ≤ b ≤ 4, 1 ≤ c ≤ 7, 5 ≤ d ≤ 27.

[0043] In the present invention, in the chemical general formula of the phthalonitrile catalyst, the value of a is preferably 4; the value of b is preferably 3; the value of c is preferably 2 - 5, more preferably 3; the value of d is preferably 8 - 23, more preferably 12 - 20, and even more preferably 15.

[0044] In the present invention, the phthalonitrile catalyst is preferably used in a fixed-bed reactor.

[0045] The present invention provides a method for preparing a phthalonitrile catalyst, comprising the following steps:

[0046] Step 1), mixing a vanadium salt solution, a titanium dispersion system, a molybdenum salt solution and an alkaline solution, followed by coprecipitation reaction to obtain a precipitate;

[0047] Step 2), subjecting the obtained precipitate to aging, filtration, washing, drying, calcination and activation in sequence to obtain the phthalonitrile catalyst.

[0048] In the present invention, in Step 1), the concentration of the vanadium salt solution is 0.1 - 3 mol / L, preferably 0.5 - 2 mol / L, more preferably 1 mol / L; the concentration of the titanium dispersion system is 0.05 - 3 mol / L, preferably 1 - 2 mol / L, more preferably 1.5 mol / L; the concentration of the molybdenum salt solution is 0.01 - 5 mol / L, preferably 1 - 3 mol / L, more preferably 2 mol / L; the concentration of the alkaline solution is 0.2 - 3 mol / L, preferably 1 - 2 mol / L, more preferably 1.5 mol / L.

[0049] In the present invention, in Step 1), the vanadium salt solution is preferably an ammonium metavanadate solution or a sodium vanadate solution, the titanium dispersion system is preferably a titanium sulfate solution or a titanium sol, and the molybdenum salt solution is preferably an ammonium molybdate solution; the alkaline solution is preferably ammonia water or an ammonium carbonate solution.

[0050] In the present invention, in Step 1), according to the different raw material systems, the following preferred schemes can be implemented for the coprecipitation reaction:

[0051] a. Slowly drop the ammonium metavanadate solution, the titanium sol and the ammonium molybdate solution into ammonia water simultaneously. The concentration of ammonium metavanadate is 0.1 - 3 mol / L, preferably 0.5 - 2 mol / L, more preferably 1 mol / L; the concentration of the titanium sol is 0.05 - 3 mol / L, preferably 1 - 2 mol / L, more preferably 1.5 mol / L; the concentration of the ammonium molybdate solution is 0.01 - 5 mol / L, preferably 1 - 3 mol / L, more preferably 2 mol / L; the concentration of ammonia water is 1.5 mol / L. The volumes of the ammonium metavanadate solution, the titanium sol and the ammonium molybdate solution are preferably added according to the molar ratio range of each element in the phthalonitrile catalyst; the volume of ammonia water is 200 - 1000 mL, preferably 400 - 800 mL, more preferably 600 mL;

[0052] Among them, the titanium sol is formed by slowly dropping tetrabutyl titanate into 300 mL of ethanol and 200 mL of a nitric acid solution with a concentration of 0.1 mol / L and stirring at room temperature for 2 h;

[0053] b. Slowly and simultaneously drop the sodium vanadate solution, titanium sulfate solution, and ammonium molybdate solution into the ammonium carbonate solution. The concentration of the sodium vanadate solution is 0.5 - 1 mol / L, more preferably 0.8 mol / L; the concentration of the titanium sulfate solution is 0.2 - 0.7 mol / L, more preferably 0.4 mol / L; the concentration of the ammonium molybdate solution is 0.1 - 0.5 mol / L, more preferably 0.3 mol / L; the concentration of the ammonium carbonate solution is 2 - 3 mol / L, more preferably 2.5 mol / L. The volumes of the sodium vanadate solution, titanium sulfate solution, and ammonium molybdate solution are preferably added according to the molar ratio range of each element in the phthalonitrile catalyst. The volume of the ammonium carbonate solution is 200 - 1000 mL, preferably 400 - 800 mL, and more preferably 600 mL.

[0054] In the present invention, the system temperature of the coprecipitation reaction is 30 - 45 °C, preferably 35 - 40 °C, and more preferably 38 °C.

[0055] In the present invention, in step 1), the temperature of the coprecipitation reaction is 32 - 45 °C, preferably 35 - 42 °C, and more preferably 40 °C.

[0056] In the present invention, in step 2), the temperature of the aging is 65 - 85 °C, preferably 70 - 80 °C, and more preferably 75 °C. The aging time is 6 - 8 h, preferably 7 h.

[0057] The drying temperature is 110 - 150 °C, preferably 120 - 140 °C, and more preferably 130 °C. The drying time is 10 - 15 h, preferably 13 h.

[0058] In the present invention, in step 2), the calcination temperature is 450 - 650 °C. According to the different coprecipitation reactions in step 1), the following optimization schemes can be implemented:

[0059] A. When the coprecipitation reaction is carried out according to Scheme a, the calcination temperature is preferably 470 - 550 °C, and more preferably 500 °C.

[0060] B. When the coprecipitation reaction is carried out according to Scheme b, the calcination temperature is preferably 570 - 620 °C, and more preferably 600 °C.

[0061] In the present invention, the calcination time is 3 - 5 h, preferably 4 h, and the heating rate is 3 - 7 °C / min, preferably 5 °C / min.

[0062] In the present invention, in step 2), the calcination is preferably carried out in an air atmosphere.

[0063] In step 2), the activation is carried out under a nitrogen atmosphere. The activation temperature is 400 - 480 °C, preferably 420 - 460 °C, and more preferably 450 °C. The activation time is 2 - 5 h, preferably 3 h.

[0064] The present invention provides a method for preparing a phthalonitrile catalyst, comprising the following steps:

[0065] Step a): Mix vanadium pentoxide, titanium dioxide, molybdenum trioxide and an oxalic acid solution to obtain a mixed metal salt impregnation solution;

[0066] Step b): Immerse the pretreated carrier in the mixed metal salt impregnation solution, and then sequentially dry, calcine and activate the obtained material to obtain a phthalonitrile catalyst.

[0067] In the present invention, in step a), the concentration of the oxalic acid solution is 1 - 1.5 mol / L, preferably 1.2 mol / L. The dosage ratio of vanadium pentoxide to the oxalic acid solution is 30 - 50 g:800 mL, preferably 40 g:800 mL. The mass ratio of vanadium pentoxide, titanium dioxide and molybdenum trioxide is 3 - 5:2 - 4:1 - 3, preferably 4:3:2.

[0068] In the present invention, in step b), the pretreatment is to calcine the carrier at 500 - 600 °C for 2.5 - 4 h. The pretreatment temperature is preferably 550 °C and the time is preferably 3 h. The carrier includes alumina and / or silica, preferably alumina or silica, and more preferably silica. The dosage ratio of the mixed metal salt impregnation solution to the carrier is 800 - 1000 mL:1000 - 1400 g, preferably 900 mL:1200 g;

[0069] The specific surface area of the carrier is 180 - 220 m 2 / g, preferably 200 m 2 / g, the pore volume is 0.3 - 0.7 cm 3 / g, preferably 0.5 cm 3 / g, and the average pore diameter is 8 - 12 nm, preferably 10 nm;

[0070] The drying temperature is 110 - 150 °C, preferably 120 - 140 °C, and more preferably 130 °C. The drying time is 8 - 12 h, preferably 10 h;

[0071] The calcination temperature is 550 - 600 °C, preferably 580 °C. The calcination time is 3 - 7 h, preferably 5 h, and the heating rate is 5 - 10 °C / min, preferably 8 °C / min;

[0072] The activation temperature is 400 to 500 °C, preferably 420 to 480 °C, more preferably 450 °C, and the activation time is 1.5 to 4 h, preferably 2 to 3 h, more preferably 2.5 h.

[0073] The present invention provides a method for preparing a phthalonitrile catalyst, comprising the following steps:

[0074] Step 1): Mix vanadyl acetylacetonate and isopropanol to obtain a vanadium sol;

[0075] Step 2): Mix isopropyl titanate, isopropanol and water, and obtain a titanium sol under the catalysis of concentrated hydrochloric acid;

[0076] Step 3): Sequentially mix the titanium sol and ammonium heptamolybdate solution with the vanadium sol and then carry out a gelation reaction, and then sequentially dry, calcine and activate the obtained gel to obtain a phthalonitrile catalyst.

[0077] In the present invention, in Step 1), the dosage ratio of vanadyl acetylacetonate to isopropanol is 20 to 50 g: 400 mL, preferably 30 g: 400 mL;

[0078] In Step 1), the mixing is carried out with stirring, the stirring temperature is 23 to 32 °C, preferably 28 °C, the stirring time is 0.5 to 2 h, preferably 1 to 1.5 h, more preferably 1.3 h.

[0079] In the present invention, in Step 2), the dosage ratio of isopropyl titanate, isopropanol and water is 30 to 50 g: 180 to 220 mL: 80 to 120 mL, preferably 40 g: 200 mL: 100 mL, and the dosage ratio of isopropyl titanate to concentrated hydrochloric acid is 30 to 50 g: 4 to 7 mL, preferably 40 g: 6 mL;

[0080] In Step 2), the mixing is carried out with stirring, the stirring temperature is 23 to 32 °C, preferably 25 to 30 °C, more preferably 28 °C, and the stirring time is 1 to 3 h, preferably 2 h.

[0081] In the present invention, in Step 3), the mixing is carried out with stirring, the temperature of the gelation reaction is 55 to 65 °C, preferably 60 °C, the time is 1.5 to 3 h, preferably 2 to 2.5 h, more preferably 2.3 h;

[0082] In Step 3), the drying temperature is 90 to 120 °C, preferably 100 °C, and the drying time is 18 to 25 h, preferably 20 to 23 h, more preferably 22 h;

[0083] In step (iii), the calcination temperature is 450 to 500 °C, preferably 480 °C, the calcination time is 5 to 8 h, preferably 7 h, and the heating rate is 5 to 8 °C / min, preferably 7 °C / min;

[0084] In step (iii), the activation temperature is 400 to 450 °C, preferably 420 to 440 °C, more preferably 430 °C, and the activation time is 3 to 6 h, preferably 4 h.

[0085] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0086] Example 1

[0087] Precisely weigh 300 g of ammonium metavanadate (NH4VO3), 250 g of tetrabutyl titanate (C 16 H 36 O4Ti) and 150 g of ammonium molybdate ((NH4)6Mo7O 24 ·4H2O). Dissolve ammonium metavanadate in 2000 ml of deionized water, heat to 60 °C and stir until completely dissolved to obtain a vanadium salt solution; slowly add tetrabutyl titanate dropwise to a mixed solution of 300 ml of ethanol and 200 ml of nitric acid (concentration 0.1 mol / L), stir at room temperature for 2 h to form a titanium sol; dissolve ammonium molybdate in 300 ml of deionized water, heat to 50 °C and stir until dissolved to obtain a molybdenum salt solution.

[0088] Slowly drop all the above three solutions simultaneously into 200 ml of ammonia water with a concentration of 1.5 mol / L. The dropping is carried out under stirring, the stirring speed is 300 r / min, and the dropping rate is controlled to keep the temperature of the reaction system at 35 °C. After the dropping is completed, continue to stir for 1 h to allow the coprecipitation reaction to proceed fully.

[0089] After the coprecipitation reaction ends, age the obtained precipitate at 80 °C for 8 h, filter it, wash it repeatedly with deionized water until the filtrate is neutral, and then dry it at 120 °C for 15 h to obtain a catalyst precursor powder. Then, heat this powder to 500 °C at a heating rate of 5 °C / min in an air atmosphere and calcine for 4 h. The calcined catalyst precursor is activated at 420 °C in a nitrogen atmosphere for 3 h to obtain V3TiMoO 12.5 , denoted as catalyst sample 1.

[0090] Reaction performance test:

[0091] A stainless steel fixed-bed reactor with an inner diameter of 25 mm and a length of 4000 mm was used. First, 50 mm thick 7*7*4 mm porcelain rings were filled at the bottom of the reactor as a support layer, and then 100 g of catalyst sample 1 was evenly loaded in the middle of the reactor. Another 50 mm thick 7*7*4 mm porcelain rings were filled above the catalyst bed as a covering layer to ensure uniform distribution of the materials.

[0092] The raw material o-xylene, ammonia, and air were mixed through a mass flow controller according to a molar ratio of 1:7:35 and then fed into the reactor. The reaction temperature was controlled at 380 °C, the reaction pressure was maintained at 0.12 MPa, and the space velocity of the raw material mixed gas was set at 1800 h -1 . After the reaction products were cooled and separated by gas-liquid separation, a gas chromatograph (GC-2010, equipped with a flame ionization detector (FID) and a thermal conductivity detector (TCD)) was used for analysis. After analysis, the conversion rate of o-xylene reached 96.0%, and the selectivity of phthalonitrile was 89.0%. After the catalyst was continuously operated for 600 h, the conversion rate of o-xylene was 99.5%, and the selectivity of phthalonitrile was 88.0%.

[0093] Example 2

[0094] 40.0 g of vanadium pentoxide (V2O5), 30.0 g of titanium dioxide (TiO2) powder, and 20.0 g of molybdenum trioxide (MoO3) were weighed and mixed with 800 ml of oxalic acid solution with a concentration of 1.2 mol / L. The mixture was stirred and heated at 70 °C for 3 h until the solids were completely dissolved to form a mixed metal salt impregnation solution.

[0095] 1200 g of γ-Al2O3 support (specific surface area of 200 m 2 / g, pore volume of 0.5 cm 3 / g, average pore diameter of 10 nm) calcined at 550 °C for 3 h was taken and impregnated in the above mixed metal salt impregnation solution at 65 °C for 5 h. After impregnation, the obtained sample was dried at 130 °C for 10 h, then calcined in an air atmosphere at a heating rate of 8 °C / min to 580 °C for 5 h, and finally the calcined catalyst was activated in an air atmosphere at 450 °C for 2 h to obtain V3Ti3MoO 13.5 , denoted as catalyst sample 2.

[0096] Performance test results:

[0097] The same fixed-bed reactor as in Example 1 was used. The raw material o-xylene, ammonia, and air were mixed according to a molar ratio of 1:8:38, the reaction temperature was 390 °C, the pressure was 0.1 MPa, and the space velocity of the mixed gas was 2200 h -1The analysis results of the reaction products showed that the conversion rate of o-xylene was 99.2%, and the selectivity of phthalonitrile was 90.5%. After continuous operation for 800 h, the conversion rate of o-xylene was 99.0%, and the selectivity of phthalonitrile was 89.8%.

[0098] Example 3

[0099] 25 g of vanadyl acetylacetonate (C 10 H 14 O5V) was mixed with 400 ml of isopropanol and stirred at room temperature for 1 h to obtain a vanadium sol; 35 g of titanium isopropoxide (C 12 H 28 O4Ti), 200 ml of isopropanol and 100 ml of deionized water were mixed, 5 ml of concentrated hydrochloric acid was added as a catalyst, and the mixture was stirred at room temperature for 2 h to form a titanium sol; 18 g of ammonium heptamolybdate ((NH4)6Mo7O 24 ) was dissolved in 300 ml of deionized water, heated to 40 °C and stirred until dissolved to obtain a molybdenum salt solution.

[0100] The titanium sol solution was slowly added dropwise to the vanadium sol solution, and the mixture was continuously stirred at a speed of 300 r / min during the addition. After the addition was completed, stirring was continued for 1 h. Then, the molybdenum salt solution was added dropwise to the above-mentioned mixed sol, and after stirring for 2 h, a uniform mixed sol was obtained. The mixed sol was placed at 60 °C for 12 h for a gelation reaction to obtain a gel-like substance. The gel was dried at 100 °C for 20 h, and then calcined at 480 °C for 6 h. The calcination atmosphere was air, and the heating rate was 6 °C / min. The calcined catalyst precursor was activated at 430 °C for 4 h in a nitrogen atmosphere to obtain VTiMoO 7.5 , denoted as catalyst sample 3.

[0101] Performance test results:

[0102] Using the same fixed-bed reactor as in Example 1, the molar ratio of the raw materials was o-xylene: ammonia: air = 1:9:40, the reaction temperature was 370 °C, the pressure was 0.15 MPa, and the space velocity of the mixed gas was 1500 h -1 . After analysis, the conversion rate of o-xylene was 99.5%, and the selectivity of phthalonitrile was 91.0%. After continuous operation for 700 h, the conversion rate of o-xylene was 95.0%, and the selectivity of phthalonitrile was 90.0%.

[0103] Example 4

[0104] Take 140 mL of 0.6 mol / L sodium vanadate (NaVO3) solution, 157.5 mL of 0.4 mol / L titanium sulfate (Ti(SO4)2) solution, and 20 mL of 0.3 mol / L ammonium molybdate solution. Under the stirring condition with a rotation speed of 400 r / min, slowly drop the above three solutions into 2.5 mol / L ammonium carbonate solution, and simultaneously introduce nitrogen into the reaction system to exclude oxygen interference. Control the dropping speed to maintain the system temperature at 40 °C for coprecipitation reaction.

[0105] After the precipitation is complete, age at 70 °C for 7 h. After the aged precipitate is filtered and washed to neutral, dry at 140 °C for 12 h to obtain the catalyst precursor powder. Press the catalyst precursor powder into tablets, then calcine at 620 °C for 4 h, and then activate at 460 °C for 3 h in an air atmosphere to obtain V2TiMo7O 27 , denoted as catalyst sample 4.

[0106] Use the same fixed-bed reactor as in Example 1. The raw materials o-xylene, ammonia, and air are mixed according to a molar ratio of 1:7.5:36. The reaction temperature is 385 °C, the pressure is 0.11 MPa, and the gas hourly space velocity of the mixed gas is 2000 h -1 . The analysis results show that the conversion rate of o-xylene is 99.4%, and the selectivity of phthalonitrile is 90.2%. After the catalyst runs continuously for 900 h, the conversion rate of o-xylene is 99.2%, and the selectivity of phthalonitrile is 89.5%.

[0107] As can be seen from the above examples, the present invention provides a phthalonitrile catalyst and its preparation method. The catalyst prepared by the present invention shows good catalytic performance in the fixed-bed ammoxidation of o-xylene to phthalonitrile, has a high conversion rate of o-xylene, selectivity of phthalonitrile, and excellent catalyst stability, and can effectively overcome many problems in the prior art, providing reliable technical support for the industrial production of phthalonitrile.

[0108] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A phthalonitrile catalyst, characterized in that The chemical formula of the phthalonitrile catalyst is V a Ti b Mo c O d , among which, 3≤a≤5, 2≤b≤4, 1≤c≤7, 5≤d≤27.

2. The method for preparing a phthalonitrile catalyst according to claim 1, characterized in that: The following steps are involved: Step 1), mixing the vanadium salt solution, the titanium dispersion system, the molybdenum salt solution and the alkaline solution, and then performing a coprecipitation reaction to obtain a precipitate; Step 2), the obtained precipitate is aged, filtered, washed, dried, calcined and activated in sequence to obtain a phthalonitrile catalyst.

3. The method for preparing a phthalonitrile catalyst according to claim 2, wherein: In step 1), the concentration of the vanadium salt solution is 0.1-3 mol / L, the concentration of the titanium dispersion system is 0.05-3 mol / L, the concentration of the molybdenum salt solution is 0.01-5 mol / L, and the concentration of the alkaline solution is 0.2-3 mol / L; In step 1), the temperature of the coprecipitation reaction is 32-45°C; In step 2), the aging temperature is 65-85°C and the aging time is 6-8h; The drying temperature is 110-150°C and the drying time is 10-15h; The calcination temperature is 450-650°C, the calcination time is 3-5h, and the heating rate is 3-7°C / min; In step 2), the activation is carried out under a nitrogen atmosphere, the activation temperature is 400-480° C., and the activation time is 2-5 hours.

4. The method for preparing a phthalonitrile catalyst according to claim 1, characterized in that: The following steps are involved: Step a), mixing vanadium pentoxide, titanium dioxide, molybdenum trioxide and oxalic acid solution to obtain a mixed metal salt impregnation solution; Step b), impregnating the pretreated support in a mixed metal salt impregnation solution, and then drying, calcining and activating the obtained material in sequence to obtain a phthalonitrile catalyst.

5. The method for preparing a phthalonitrile catalyst according to claim 4, wherein: In step a), the concentration of the oxalic acid solution is 1-1.5 mol / L, and the usage ratio of vanadium pentoxide to oxalic acid solution is 30-50 g:800 mL.

6. The method for preparing a phthalonitrile catalyst according to claim 4 or 5, wherein: In step b), the pretreatment is to calcine the carrier at 500-600° C. for 2.5-4 hours, the carrier comprises alumina and / or silica, and the ratio of the mixed metal salt impregnation solution to the carrier is 800-1000 mL: 1000-1400 g; The specific surface area of ​​the carrier is 180 to 220 m 2 / g, pore volume is 0.3~0.7cm 3 / g, average pore size is 8-12nm; The drying temperature is 110-150°C and the drying time is 8-12h; The calcination temperature is 550-600°C, the calcination time is 3-7h, and the heating rate is 5-10°C / min; The activation temperature is 400-500° C., and the activation time is 1.5-4 hours.

7. The method for preparing a phthalonitrile catalyst according to claim 1, characterized in that: The following steps are involved: Step 1), mixing vanadium acetylacetonate and isopropanol to obtain vanadium sol; Step 2), mixing isopropyl titanate, isopropyl alcohol and water, and obtaining titanium sol under the catalysis of concentrated hydrochloric acid; Step 3), the titanium sol and the ammonium heptamolybdate solution are sequentially mixed with the vanadium sol to carry out a gelation reaction, and then the obtained gel is sequentially dried, calcined and activated to obtain a phthalonitrile catalyst.

8. The method for preparing a phthalonitrile catalyst according to claim 7, wherein: In step 1), the usage ratio of vanadium acetylacetonate and isopropanol is 20-50 g:400 mL; In step 1), the mixing is carried out under stirring at a temperature of 23 to 32° C. and a stirring time of 0.5 to 2 h.

9. A method for preparing a phthalonitrile catalyst according to claim 7 or 8, characterized in that: In step 2), the usage ratio of isopropyl titanate, isopropyl alcohol and water is 30-50 g: 180-220 mL: 80-120 mL, and the usage ratio of isopropyl titanate and concentrated hydrochloric acid is 30-50 g: 4-7 mL; In step 2), the mixing is carried out under stirring, the stirring temperature is 23 to 32° C., and the stirring time is 1 to 3 hours.

10. The method for preparing a phthalonitrile catalyst according to claim 9, characterized in that: In step 3), the mixing is carried out under stirring, the temperature of the gelation reaction is 55 to 65° C., and the time is 1.5 to 3 hours; In step 3), the drying temperature is 90-120°C and the drying time is 18-25h; In step 3), the calcination temperature is 450-500°C, the calcination time is 5-8h, and the heating rate is 5-8°C / min; In step 3), the activation temperature is 400-450° C., and the activation time is 3-6 hours.