Catalyst for preparing methacrylonitrile by isobutylene ammoxidation and preparation method and application thereof

Abstract

This invention discloses a catalyst for the preparation of methacrylonitrile via isobutylene ammoxidation, its preparation method, and its application. The catalyst for the preparation of methacrylonitrile via isobutylene ammoxidation comprises an active component and a support; the active component is Mo. a Bi b Fe c Ni d K e Mg f Ti g Ce h Sb i O z Wherein, a is 10-13, b is 0.1-3, c is 0.1-3, d is 3-10, e is 0.1-3, f is 0.1-3, g is 0.1-2, h is 0.1-3, i is 0.1-5, and the atomic ratio of b to h is 0.3-1.5, the atomic ratio of h to c is 0.5-6, the atomic ratio of b+h to d is 0.2-1.2, and the atomic ratio of h to b+h is 0.2-1.0; z is the total number of oxygen atoms required to satisfy the valence. The support is a porous medium. The catalyst is prepared by co-precipitation, and ultrasonic and ultraviolet enhancement are introduced during the catalyst preparation process to improve the catalytic activity of the catalyst. When the catalyst of the present invention is used in the isobutylene ammoxidation method to prepare methacrylonitrile, the isobutylene conversion rate reaches more than 93%, and the methacrylonitrile selectivity reaches more than 80%.

Description

Technical Field

[0001] This invention relates to the field of methacrylonitrile preparation technology, specifically to a catalyst for the preparation of methacrylonitrile by isobutylene ammoxidation, its preparation method, and its application. Background Technology

[0002] Methacrylonitrile is the monomer for synthesizing polymethacrylamide (PMI). PMI foam is a typical high-performance material for both military and civilian applications, indispensable in key fields such as aerospace and military. It possesses high strength, high heat resistance, and good mechanical properties, making it the foam material with the best overall performance currently available. Compared to the traditional acetone-nitrogen alcohol method, the isobutylene ammoxidation method for producing methacrylonitrile monomers offers advantages such as high production efficiency, low product impurities, good atom economy, and significantly reduced environmental emissions. Most catalysts used in the traditional isobutylene ammoxidation to methacrylonitrile production are derived from catalysts used in the propylene ammoxidation to acrylonitrile production, as their reaction mechanisms are similar. The main active material in these catalysts is a molybdenum-bismuth composite oxide, but their catalytic efficiency for isobutylene to methacrylonitrile production is very low, necessitating catalyst improvement. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a catalyst for the preparation of methacrylonitrile via isobutylene ammoxidation, its preparation method, and its application.

[0004] The technical solution adopted in this invention is as follows: In a first aspect, the present invention provides a catalyst for the preparation of methacrylonitrile by isobutylene ammoxidation, the catalyst comprising an active component and a support; The active component is Mo. a Bi b Fe c Ni d K e Mg f Ti g Ce h Sb i O z Where a is 10~13, b is 0.1~3, c is 0.1~3, d is 3~10, e is 0.1~3, f is 0.1~3, g is 0.1~2, h is 0.1~3, i is 0.1~5, and the atomic ratio of b to h is 0.3~1.5, the atomic ratio of h to c is 0.5~6, the atomic ratio of b+h to d is 0.2~1.2, the atomic ratio of h to b+h is 0.2~1.0, and z is the total number of oxygen atoms required to satisfy the valence. The carrier is a porous medium.

[0005] Furthermore, the carrier is an oxide carrier, specifically including one or more of silicon dioxide, aluminum oxide, titanium dioxide, and zirconium dioxide.

[0006] Furthermore, the loading of the active component in the catalyst is 10~90wt%.

[0007] Furthermore, the active components of the catalyst are obtained through screening using machine learning methods. The screening steps are as follows: Data on the chemical elements of active components and synthesis reaction parameters of the catalyst for the preparation of methacrylonitrile metal oxide by isobutylene ammoxidation were collected. The atomic percentage of each active component chemical element and the catalytic reaction temperature in the synthesis reaction parameters were used as input values, and the conversion rate and selectivity of the catalyst for the preparation of methacrylonitrile metal oxide by isobutylene ammoxidation were used as output values. The dataset was constructed, normalized, and divided into training set and test set. Build a machine learning model, train the machine learning model using a training set to obtain a mature machine learning model, and evaluate the predictive ability of the model using a test set. Determine the target active components for screening the desired metal oxide catalyst for the isobutylene ammoxidation process to prepare methacrylonitrile; A well-trained machine learning model is used to predict the conversion rate and selectivity of the identified active components, obtain the combination of active components with high conversion rate and high selectivity and the atomic percentage of each element in the combination, and use them as the active components of the optimal metal oxide catalyst.

[0008] Secondly, the present invention provides a method for preparing a catalyst for the preparation of methacrylonitrile via isobutylene ammoxidation, comprising the steps of: (1) Dissolve the molybdenum soluble salt in deionized water and stir until clear, then add a carrier to obtain solution A; (2) Dissolve bismuth soluble salt, iron soluble salt, magnesium soluble salt, nickel soluble salt, cerium soluble salt and 2~4 mol / L nitric acid in deionized water and stir until clear to obtain solution B; (3) Dissolve tetrabutyl titanate in anhydrous ethanol and stir until homogeneous to obtain solution C; (4) Dissolve antimony trioxide in an aqueous solution of tartaric acid or citric acid and stir until homogeneous to obtain solution D; (5) Slowly add solutions B, C, and D to solution A under water bath conditions and stir until homogeneous to obtain a composite solution. Then adjust the pH to 5-6 with ammonia water to obtain solution E. (6) Let solution E stand for 2-10 hours, then filter it, and wash it with deionized water to remove nitrate ions. Pulverize the cleaned filter cake and add potassium nitrate solution. Stir for 30-60 minutes to obtain a mixed slurry. (7) The mixed slurry is dried and calcined to obtain a catalyst for the preparation of methacrylonitrile by the isobutylene ammoxidation method.

[0009] Furthermore, the water bath temperature in step (5) is 50~100℃.

[0010] Furthermore, in step (5), ultrasonic enhancement and / or ultraviolet enhancement are introduced during the mixing of solutions B, C, and D with solution A and the adjustment of pH. The power of the ultrasonic enhancement is 800~1500W, and the time is 10~30min; The UV-enhanced irradiation intensity is 200~800W / m. 2 The time is 1 to 6 hours.

[0011] In the aforementioned technical solutions, ultrasonic enhancement is primarily a physical enhancement method. The rapid, intense growth of bubbles, accompanied by high-speed microjets and shock waves, can quickly enhance mass transfer, eliminate the concentration boundary layer, and generate numerous active sites on the catalyst surface, all within a short timeframe. However, prolonged ultrasonic enhancement can severely damage the catalyst structure, and the accumulated heat can cause irreversible damage. Ultraviolet enhancement, on the other hand, involves a continuous photochemical reaction. Photons are absorbed by the photocatalyst, exciting electron transitions and generating ·OH2. - Active species undergo a gradual accumulation of light energy, requiring prolonged illumination for complete reaction. This invention combines both approaches: short-duration ultrasonic enhancement exposes catalyst surface sites while simultaneously strengthening internal mass transfer, followed by prolonged ultraviolet light enhancement to modify and activate these surface sites, thereby improving the catalyst's catalytic activity.

[0012] Furthermore, in step (7), the drying temperature is 100~200℃, the drying time is 2~5h, the calcination temperature is 400~600℃, the calcination time is 3~6h, and the calcination atmosphere is air.

[0013] Thirdly, the present invention also provides the application of a catalyst in the preparation of methacrylonitrile by the isobutylene ammoxidation method.

[0014] Furthermore, in the application process, the catalyst is added to the fluidized bed reactor, the inlet pressure is set to 0.1~0.3MPa, the reaction temperature is set to 380~430℃, the feed volume ratio of isobutylene, ammonia, and air is 1:1.0~1.6:9~15, and the total weight hourly space velocity of the reactants is 0.5~4h⁻¹. -1 Methacrylonitrile is obtained by ammonia oxidation.

[0015] The beneficial effects of this invention are as follows: (1) This invention proposes a catalyst for the preparation of methacrylonitrile by isobutylene ammoxidation. The catalyst is obtained by screening through machine learning. Compared with traditional experimental methods, this invention can establish the correlation between the active components of the catalyst and the conversion rate of isobutylene and the selectivity of methacrylonitrile through machine learning, thereby quickly obtaining the active components of the catalyst with high conversion rate and selectivity. (2) In the process of preparing the catalyst for the preparation of methacrylonitrile by the isobutylene ammoxidation method, the present invention also introduces ultrasonic enhancement and ultraviolet enhancement to further improve the catalytic activity of the catalyst; when the catalyst of the present invention is used to prepare methacrylonitrile by the isobutylene ammoxidation method, the isobutylene conversion rate reaches more than 93% and the methacrylonitrile selectivity reaches more than 80%. Detailed Implementation

[0016] This invention provides a catalyst for the preparation of methacrylonitrile via the ammoxidation of isobutylene, its preparation method, and its application. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0017] Example 1 Currently, the active components of metal oxide catalysts for the isobutylene ammoxidation process to prepare methacrylonitrile are typically multi-metal element compositions. However, the specific metal element composition and their atomic numbers are not standardized, leading to varying catalytic activities in catalysts prepared with different metal element combinations. It is impossible to determine whether both high conversion and high selectivity are simultaneously achieved. Therefore, this embodiment first uses machine learning methods to screen for active components in the isobutylene ammoxidation process to prepare methacrylonitrile metal oxide catalysts, and then uses these active components to prepare a catalyst for the isobutylene ammoxidation process to prepare methacrylonitrile.

[0018] The specific process for screening the active components of the isobutylene ammoxidation catalyst for preparing methacrylonitrile metal oxide using the above-mentioned machine learning method is as follows: S1. Based on literature data, a database of metal oxide catalysts for the ammoxidation of isobutylene to methacrylonitrile and metal oxide catalysts for the ammoxidation of propylene to acrylonitrile (a total of 218 samples) was collected. The chemical elemental composition of their active components (a total of 25 chemical elements, including Mo, Bi, Fe, Ce, Sm, La, Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Ni, Co, Zn, Mn, W, Sb, Cu, Ag, Cr) and the atomic fraction of each element were analyzed. Synthesis reaction parameter data, including catalyst... The reaction temperature, isobutylene conversion rate, propylene conversion rate, methacrylonitrile and acrylonitrile selectivity were used as input values, and the conversion rate and selectivity of the metal oxide catalyst for the preparation of methacrylonitrile by isobutylene ammoxidation were used as output values. A dataset was constructed, preprocessed, and divided into training and testing sets in an 8:2 ratio. Since the preparation of methacrylonitrile by isobutylene ammoxidation is similar to that by propylene ammoxidation, the propylene ammoxidation method for acrylonitrile preparation was also considered in this step. S2. Establish various types of machine learning models, train the machine learning models using the training set to obtain mature machine learning models, and use the test set to evaluate the predictive ability of each model, and select the machine learning model with the highest prediction accuracy as the optimal model. S3. Determine the target active components for screening the metal oxide catalysts used in the isobutylene ammoxidation method to prepare methacrylonitrile; S4. Using a well-trained optimal machine learning model, the conversion rate and selectivity of the selected active component screening targets are predicted to obtain a combination of active components with high conversion rate and high selectivity, as well as the atomic percentage of each element in the combination, which is then used as the active component of the optimal metal oxide catalyst.

[0019] The preprocessing of the dataset in step S1 above includes: first, using the Pearson correlation coefficient to preprocess the data in the dataset and removing variables with high correlation between variables; then, using the RobustScaler method to normalize the remaining elements.

[0020] In step S2 above, the machine learning models used are decision trees, random forests, support vector machines, gradient boosting machines, and XGBoost.

[0021] The parameters used in step S2 above to evaluate the predictive ability of the machine learning model include: MSE and / or R. 2 And / or MAE. The evaluation parameters for each model were calculated as follows: Decision tree: MSE=19.792, MAE=11.6983, R 2 =0.48; Random Forest: MSE=12.761, MAE=8.727, R 2 =0.78; Support Vector Machine: MSE=25.998, MAE=19.76, R 2 =0.103; Gradient boosting: MSE=17.316, MAE=10.402, R 2 =0.513; XGBoost: MSE=5.472, MAE=3.316, R 2 =0.939; By comparison, the XGBoost model has the highest prediction accuracy (its MSE and MAE are both the lowest, and R0 is the lowest). 2 (Maximum), and then the XGBoost model was used to screen the active components of the catalyst.

[0022] In step S3 above, the active component of the metal oxide catalyst used in the isobutylene ammoxidation method to prepare methacrylonitrile is set to Mo. A Bi B Fe C X D Y E Z F O G Wherein, X is a rare earth element, selected from one or more of Ce, Sm, and La; Y is an alkali metal or alkaline earth metal element, selected from one or more of Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, and Ba; and Z is a transition metal or group VA metal element, selected from one or more of Ni, Co, Zn, Mn, W, and Sb.

[0023] Through the above machine learning screening, the active component of the catalyst for the preparation of methacrylonitrile via the isobutylene ammoxidation method was determined to be Mo. a Bi b Fe c Ni d K e Mg f Ti g Ce h Sb i O z The catalyst prepared from the active component is a supported catalyst, that is, it includes a support and an active component supported on the support. The support is a porous medium and is an oxide support, specifically including one or more of silica, alumina, titanium dioxide, and zirconium dioxide. The loading of the active component in the catalyst is 10~90wt%, preferably 30~60wt%.

[0024] The number of atoms of each metal element in the active component of the above catalyst is as follows: a is 10 to 13, preferably 11 to 12; b is 0.1~3, preferably 0.6~1.5; c can be 0.1~3, preferably 1~2; d can be 3~10, preferably 5~8; e is 0.1~3, preferably 0.1~0.5; f takes values ​​from 0.1 to 3, preferably from 0.8 to 1.8; g is 0.1~2, preferably 0.3~0.8; h is taken as 0.1~3, preferably 0.8~1.5; i can be 0.1~5, preferably 0.8~1.5.

[0025] More preferably, the atomic ratio of b to h is 0.3 to 1.5, the atomic ratio of h to c is 0.5 to 6, the atomic ratio of b+h to d is 0.2 to 1.2, the atomic ratio of h to b+h is 0.2 to 1.0, and z is the total number of oxygen atoms required to satisfy the valence.

[0026] Example 2 Based on the active components of the catalyst for the preparation of methacrylonitrile via isobutylene ammoxidation screened in Example 1 above, this example synthesizes a catalyst for the preparation of methacrylonitrile via isobutylene ammoxidation using the following method, the active component of which is Mo. 12 Bi 0.9 Fe 1.5 Ni6K 0.2 Mg 1.5 Ti 0.5 Ce 1.1 Sb1O 53.65 The carrier is SiO2, and the specific process is as follows: (1) Dissolve 49.95g of ammonium heptamolybdate in deionized water and stir until clear, then add 50g of silicon dioxide to obtain solution A; (2) Dissolve 10.3g bismuth nitrate pentahydrate, 14.3g ferric nitrate nonahydrate, 9.08g magnesium nitrate hexahydrate, 41.15g nickel nitrate hexahydrate, and 11.27g cerium nitrate hexahydrate in 150mL of 3mol / L nitric acid in deionized water and stir until clear to obtain solution B; nitric acid is added in this step to maintain a strongly acidic environment (pH < 1) in the mixed solution to prevent Bi 3+ Hydrolysis; (3) Dissolve 4.02g of tetrabutyl titanate in anhydrous ethanol and stir until homogeneous to obtain solution C; (4) Dissolve 3.44g of antimony trioxide in an aqueous solution of citric acid and stir until homogeneous to obtain solution D; (5) Add solutions B, C and D slowly to solution A in a water bath at 90°C and stir magnetically at 500 r / min to obtain a composite solution. Then, continue to add ammonia water under magnetic stirring to adjust the pH to 6 to obtain solution E. (6) Let solution E stand for 6 hours, then filter it, and wash it with deionized water to remove nitrate ions (using nitrate test paper). Pulverize the washed filter cake and add 0.477g potassium nitrate solution (the amount of potassium nitrate added is very small, and trace amounts of nitrate ions can be removed in the subsequent drying process). Stir for 45 minutes to obtain a mixed slurry. (7) The mixed slurry was dried in air at 120°C for 2 hours, and then heated to 500°C at a rate of 10°C / h. It was then calcined in air at 500°C for 6 hours to obtain the catalyst for the preparation of methacrylonitrile by the isobutylene ammoxidation method.

[0027] The active component of the catalyst prepared in this embodiment is Mo. 12 Bi 0.9 Fe 1.5 Ni6K 0.2 Mg 1.5 Ti 0.5 Ce 1.1 Sb1O 53.65 The support is SiO2, and the loading of the active component is 50 wt% of the total mass of the catalyst.

[0028] Example 3 This embodiment synthesizes a catalyst for the preparation of methacrylonitrile via the isobutylene ammoxidation method as follows, the active component of which is Mo. 12 Bi 1.2 Fe 1.2 Ni 5.5 K 0.2 Mg 1.5 Ti 0.5 Ce 1.3 Sb1O 53.3 The carrier is SiO2, and the specific process is as follows: (1) Dissolve 48.94g of ammonium heptamolybdate in deionized water and stir until clear, then add 50g of silicon dioxide to obtain solution A; (2) Dissolve 13.44g bismuth nitrate pentahydrate, 11.2g ferric nitrate nonahydrate, 8.88g magnesium nitrate hexahydrate, 36.94g nickel nitrate hexahydrate, and 13.04g cerium nitrate hexahydrate in 150mL of 3mol / L nitric acid in deionized water and stir until clear to obtain solution B; (3) Dissolve 3.93g of tetrabutyl titanate in anhydrous ethanol and stir until homogeneous to obtain solution C; (4) Dissolve 3.37g of antimony trioxide in an aqueous solution of citric acid and stir until homogeneous to obtain solution D; (5) Add solutions B, C and D slowly to solution A in a water bath at 90°C and stir magnetically at 500 r / min to obtain a composite solution. Then, continue to add ammonia water under magnetic stirring to adjust the pH to 6 to obtain solution E. (6) Let solution E stand for 6 hours, then filter it, and wash it with deionized water to remove nitrate ions. Pulverize the cleaned filter cake and add 0.47g potassium nitrate solution. Stir for 45 minutes to obtain a mixed slurry. (7) The mixed slurry was dried in air at 120°C for 2 hours, and then heated to 500°C at a rate of 10°C / h. It was then calcined in air at 500°C for 6 hours to obtain the catalyst for the preparation of methacrylonitrile by the isobutylene ammoxidation method.

[0029] The active component of the catalyst prepared in this embodiment is Mo. 12 Bi 1.2 Fe 1.2 Ni 5.5 K 0.2 Mg 1.5 Ti 0.5 Ce 1.3 Sb1O 53.3 The support is SiO2, and the loading of the active component is 50 wt% of the total mass of the catalyst.

[0030] Example 4 This embodiment synthesizes a catalyst for the preparation of methacrylonitrile via the isobutylene ammoxidation method as follows, the active component of which is Mo. 12 Bi 0.8 Fe 1.5 Ni 7.5 K 0.2 Mg1Ti 0.5 Ce1Sb1O 54.15 The carrier is SiO2, and the specific process is as follows: (1) Dissolve 49g of ammonium heptamolybdate in deionized water and stir until clear, then add 50g of silicon dioxide to obtain solution A; (2) Dissolve 8.98g bismuth nitrate pentahydrate, 14.02g ferric nitrate nonahydrate, 5.94g magnesium nitrate hexahydrate, 50.48g nickel nitrate hexahydrate, 10.05g cerium nitrate hexahydrate, and 150mL nitric acid with a concentration of 3mol / L in deionized water and stir until clear to obtain solution B; (3) Dissolve 3.94g of tetrabutyl titanate in anhydrous ethanol and stir until homogeneous to obtain solution C; (4) Dissolve 3.37g of antimony trioxide in an aqueous solution of citric acid and stir until homogeneous to obtain solution D; (5) Add solutions B, C and D slowly to solution A in a water bath at 90°C and stir magnetically at 500 r / min to obtain a composite solution. Then, continue to add ammonia water under magnetic stirring to adjust the pH to 6 to obtain solution E. (6) Let solution E stand for 6 hours, then filter it, and wash it with deionized water to remove nitrate ions. Pulverize the cleaned filter cake and add 0.468g potassium nitrate solution. Stir for 45 minutes to obtain a mixed slurry. (7) The mixed slurry was dried in air at 120°C for 2 hours, and then heated to 500°C at a rate of 10°C / h. It was then calcined in air at 500°C for 6 hours to obtain the catalyst for the preparation of methacrylonitrile by the isobutylene ammoxidation method.

[0031] The active component of the catalyst prepared in this embodiment is Mo. 12 Bi 0.8 Fe 1.5 Ni 7.5 K 0.2 Mg1Ti 0.5 Ce1Sb1O 54. 15 The support is SiO2, and the loading of the active component is 50% of the total mass of the catalyst.

[0032] Example 5 This embodiment provides a catalyst for the preparation of methacrylonitrile via the isobutylene ammoxidation method, the active component of which is Mo. 12 Bi 0.9 Fe 1.5 Ni6K 0.2 Mg 1.5 Ti 0.5 Ce 1.1 Sb1O 53.65 The support is SiO2, and the loading of the active component is 50% of the total mass of the catalyst. The difference between this embodiment and Example 2 is that in step (5), ultrasonic enhancement is introduced in the process of mixing solutions B, C, D and A and adjusting the pH. That is, ultrasonic dispersion is performed first in the process of mixing solutions B, C, D and A, and then magnetic stirring is continued at a speed of 500 r / min to obtain a composite solution. Similarly, ultrasonic dispersion is performed first in the process of adding ammonia to adjust the pH, and then magnetic stirring is continued to be performed to obtain a composite solution. In this embodiment, the ultrasonic treatment power is 1200 W, and the total time for the two ultrasonic treatments is 20 min.

[0033] Example 6 This embodiment provides a catalyst for the preparation of methacrylonitrile via the isobutylene ammoxidation method, the active component of which is Mo. 12 Bi1.2 Fe 1.2 Ni 5.5 K 0.2 Mg 1.5 Ti 0.5 Ce 1.3 Sb1O 53.3 The support is SiO2, and the loading of the active component is 50% of the total mass of the catalyst. The difference between this embodiment and Example 3 is that in step (5), ultrasonic enhancement is introduced in the process of mixing solutions B, C, D and A and adjusting the pH. That is, ultrasonic dispersion is performed first in the process of mixing solutions B, C, D and A, and then magnetic stirring is continued at a speed of 500 r / min to obtain a composite solution. Similarly, ultrasonic dispersion is performed first in the process of adding ammonia to adjust the pH, and then magnetic stirring is continued to be performed to obtain a composite solution. In this embodiment, the ultrasonic power is 1200 W, and the total time for the two ultrasonic treatments is 20 min.

[0034] Example 7 This embodiment provides a catalyst for the preparation of methacrylonitrile via the isobutylene ammoxidation method, the active component of which is Mo. 12 Bi 0.8 Fe 1.5 Ni 7.5 K 0.2 Mg1Ti 0.5 Ce1Sb1O 54.15 The support is SiO2, and the loading of the active component is 50% of the total mass of the catalyst. The difference between this embodiment and Example 4 is that in step (5), ultrasonic enhancement is introduced in the process of mixing solutions B, C, D and A and adjusting the pH. That is, ultrasonic dispersion is performed first in the process of mixing solutions B, C, D and A, and then magnetic stirring is continued at a speed of 500 r / min to obtain a composite solution. Similarly, ultrasonic dispersion is performed first in the process of adding ammonia to adjust the pH, and then magnetic stirring is continued to be performed to obtain a composite solution. In this embodiment, the ultrasonic power is 1200 W, and the total time for the two ultrasonic treatments is 20 min.

[0035] Example 8 This embodiment provides a catalyst for the preparation of methacrylonitrile via the isobutylene ammoxidation method, the active component of which is Mo. 12 Bi 0.9 Fe 1.5 Ni6K 0.2 Mg 1.5 Ti 0.5 Ce 1.1 Sb1O 53.65The carrier is SiO2, and the loading of the active component is 50% of the total mass of the catalyst. The difference between this example and Example 2 is that in step (5), when mixing solutions B, C, D and A and adjusting the pH, ultraviolet enhancement is introduced. Specifically, during the magnetic stirring process of mixing solutions B, C, D and A and adding ammonia water, a 1000W high-pressure mercury lamp (main wavelength of 365nm) is used as an ultraviolet light source to irradiate the mixed solution. The lamp tube is 20cm away from the reaction liquid surface, and the total ultraviolet irradiation time is 4h. Under this ultraviolet irradiation condition, the intensity is about 600W / m. 2 .

[0036] Example 9 This embodiment provides a catalyst for the preparation of methacrylonitrile via the isobutylene ammoxidation method, the active component of which is Mo. 12 Bi 1.2 Fe 1.2 Ni 5.5 K 0.2 Mg 1.5 Ti 0.5 Ce 1.3 Sb1O 53.3 The carrier is SiO2, and the loading of the active component is 50% of the total mass of the catalyst. The difference between this example and Example 3 is that in step (5), when mixing solutions B, C, D and A and adjusting the pH, ultraviolet enhancement is introduced. Specifically, during the magnetic stirring process of mixing solutions B, C, D and A and adding ammonia water, a 1000W high-pressure mercury lamp (main wavelength of 365nm) is used as an ultraviolet light source to irradiate the mixed solution. The lamp tube is 20cm away from the reaction liquid surface, and the total ultraviolet irradiation time is 4h. Under this ultraviolet irradiation condition, the intensity is about 600W / m. 2 .

[0037] Example 10 This embodiment provides a catalyst for the preparation of methacrylonitrile via the isobutylene ammoxidation method, the active component of which is Mo. 12 Bi 0.8 Fe 1.5 Ni 7.5 K 0.2 Mg1Ti 0.5 Ce1Sb1O 54.15The carrier is SiO2, and the loading of the active component is 50% of the total mass of the catalyst. The difference between this example and Example 4 is that in step (5), when mixing solutions B, C, D and A and adjusting the pH, ultraviolet enhancement is introduced. Specifically, during the magnetic stirring process of mixing solutions B, C, D and A and adding ammonia water, a 1000W high-pressure mercury lamp (main wavelength of 365nm) is used as an ultraviolet light source to irradiate the mixed solution. The lamp tube is 20cm away from the reaction liquid surface, and the total ultraviolet irradiation time is 4h. Under this ultraviolet irradiation condition, the intensity is about 600W / m. 2 .

[0038] Example 11 This embodiment provides a catalyst for the preparation of methacrylonitrile via the isobutylene ammoxidation method, the active component of which is Mo. 12 Bi 0.9 Fe 1.5 Ni6K 0.2 Mg 1.5 Ti 0.5 Ce 1.1 Sb1O 53.65 The carrier is SiO2, and the loading of the active component is 50% of the total mass of the catalyst. The difference between this embodiment and Example 2 is that in step (5), when mixing solutions B, C, D and A and adjusting the pH, ultrasonic enhancement and ultraviolet enhancement are introduced. That is, ultrasonic dispersion is performed first when mixing solutions B, C, D and A, and then magnetic stirring is continued at 500 r / min to obtain a composite solution. Similarly, ultrasonic dispersion is performed first when adding ammonia to adjust the pH, and then magnetic stirring is continued to be performed. At the same time, during the ultrasonic dispersion and magnetic stirring, a 1000W high-pressure mercury lamp (main wavelength of 365nm) is used as an ultraviolet light source to irradiate the mixed solution, and the lamp tube is 20cm away from the reaction liquid surface. In this embodiment, the ultrasonic treatment power is 1200W, the ultrasonic treatment time is 20min, and the ultraviolet irradiation time is 4h. The intensity under the ultraviolet irradiation conditions is about 600W / m 2 .

[0039] Example 12 This embodiment provides a catalyst for the preparation of methacrylonitrile via the isobutylene ammoxidation method, the active component of which is Mo. 12 Bi 1.2 Fe 1.2 Ni 5.5 K 0.2 Mg 1.5 Ti 0.5 Ce 1.3 Sb1O 53.3The carrier is SiO2, and the loading of the active component is 50% of the total mass of the catalyst. The difference between this embodiment and Example 3 is that in step (5), when mixing solutions B, C, D and A and adjusting the pH, ultrasonic enhancement and ultraviolet enhancement are introduced. That is, ultrasonic dispersion is performed first when mixing solutions B, C, D and A, and then magnetic stirring is continued at 500 r / min to obtain a composite solution. Similarly, ultrasonic dispersion is performed first when adding ammonia to adjust the pH, and then magnetic stirring is continued to be performed. At the same time, during the ultrasonic dispersion and magnetic stirring, a 1000W high-pressure mercury lamp (main wavelength of 365nm) is used as an ultraviolet light source to irradiate the mixed solution, and the lamp tube is 20cm away from the reaction liquid surface. In this embodiment, the ultrasonic treatment power is 1200W, the ultrasonic treatment time is 20min, and the ultraviolet irradiation time is 4h. The intensity under the ultraviolet irradiation conditions is about 600W / m 2 .

[0040] Example 13 This embodiment provides a catalyst for the preparation of methacrylonitrile via the isobutylene ammoxidation method, the active component of which is Mo. 12 Bi 0.8 Fe 1.5 Ni 7.5 K 0.2 Mg1Ti 0.5 Ce1Sb1O 54.15 The carrier is SiO2, and the loading of the active component is 50% of the total mass of the catalyst. The difference between this embodiment and Example 4 is that in step (5), when mixing solutions B, C, D and A and adjusting the pH, ultrasonic enhancement and ultraviolet enhancement are introduced. That is, ultrasonic dispersion is performed first when mixing solutions B, C, D and A, and then magnetic stirring is continued at 500 r / min to obtain a composite solution. Similarly, ultrasonic dispersion is performed first when adding ammonia to adjust the pH, and then magnetic stirring is continued to be performed. At the same time, during the ultrasonic dispersion and magnetic stirring, a 1000W high-pressure mercury lamp (main wavelength of 365nm) is used as an ultraviolet light source to irradiate the mixed solution, and the lamp tube is 20cm away from the reaction liquid surface. In this embodiment, the ultrasonic treatment power is 1200W, the ultrasonic treatment time is 20min, and the ultraviolet irradiation time is 4h. The intensity under the ultraviolet irradiation conditions is about 600W / m 2 .

[0041] The catalysts prepared in Examples 1-13 above were used in the reaction process of isobutylene ammoxidation to prepare methacrylonitrile, and the reaction conditions were the same: 10g of catalyst was added to a fluidized bed reactor, the inlet pressure was set to 0.1MPa, the reaction temperature was 410℃, the feed volume ratio of isobutylene, ammonia, and air was 1:1.2:13, and the weight hourly space velocity was 1.5h⁻¹. -1 .

[0042] The products obtained from the above isobutylene ammoxidation method for preparing methacrylonitrile were subjected to chromatographic analysis, and the isobutylene conversion rate and methacrylonitrile selectivity were calculated. The detection results of each example are shown in Table 1 below.

[0043] Table 1. Results of isobutylene conversion and methacrylonitrile selectivity in Examples 1-13 Analysis of the test results in Table 1 above shows that the catalysts prepared in Examples 1-13 all exhibit good catalytic activity for the ammoxidation of isobutylene to methacrylonitrile. Furthermore, the introduction of ultrasonic and / or ultraviolet (UV) enhancement further improves the catalytic activity. In particular, the simultaneous introduction of ultrasonic and UV enhancement significantly enhances the catalytic activity, achieving a maximum isobutylene conversion of 96.6% and a maximum methacrylonitrile conversion of 84.3%. This is because: ultrasonic enhancement strengthens the uniform distribution of active components in the catalyst preparation process, enhances particle dispersion, eliminates the concentration boundary layer, and generates numerous active sites on the catalyst surface, thus improving catalytic activity by regulating the catalyst configuration; simultaneously, the introduction of UV light has a certain photocatalytic effect, reducing the Ce content in the metal catalyst. 4+ Converted to Ce 3+ Mo 6+ Reduced to Mo 5+ This enhances the fluidity of surface oxygen, creating oxygen vacancies in the surface lattice and providing more reactive sites, thereby increasing the reaction rate; simultaneously, O2 forms reactive oxygen species ·O2 under ultraviolet light irradiation. - This makes it easier for it to participate in oxidation reactions; Bi generates electron-hole pairs under ultraviolet light, and the holes generated have strong oxidizing properties and can directly participate in activating ammonia molecules into amino radicals (-NH2); Fe is a co-catalyst, forming Fe under ultraviolet conditions. 3+ / Fe 2+ Highly efficient electron transfer chain, optimized electron transfer path to prolong hole activity.

[0044] It should be noted that any parts not mentioned in this invention can be achieved by using or referencing existing technologies.

[0045] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A catalyst for the preparation of methacrylonitrile via isobutylene ammoxidation, characterized in that, The catalyst includes an active component and a support; The active component is Mo. a Bi b Fe c Ni d K e Mg f Ti g Ce h Sb i O z Where a is 10~13, b is 0.1~3, c is 0.1~3, d is 3~10, e is 0.1~3, f is 0.1~3, g is 0.1~2, h is 0.1~3, i is 0.1~5, and the atomic ratio of b to h is 0.3~1.5, the atomic ratio of h to c is 0.5~6, the atomic ratio of b+h to d is 0.2~1.2, the atomic ratio of h to b+h is 0.2~1.0, and z is the total number of oxygen atoms required to satisfy the valence. The carrier is a porous medium.

2. The catalyst for the preparation of methacrylonitrile by the isobutylene ammoxidation method according to claim 1, characterized in that, The carrier is an oxide carrier, specifically including one or more of silicon dioxide, aluminum oxide, titanium dioxide, and zirconium dioxide.

3. The catalyst for the preparation of methacrylonitrile by the isobutylene ammoxidation method according to claim 1, characterized in that, The loading of the active component in the catalyst is 10~90wt%.

4. The catalyst for the preparation of methacrylonitrile by the isobutylene ammoxidation method according to claim 1, characterized in that, The active components of the catalyst were obtained through screening using machine learning methods. The screening steps are as follows: Data on the chemical elements of active components and synthesis reaction parameters of the catalyst for the preparation of methacrylonitrile metal oxide by isobutylene ammoxidation were collected. The atomic percentage of each active component chemical element and the catalytic reaction temperature in the synthesis reaction parameters were used as input values, and the conversion rate and selectivity of the catalyst for the preparation of methacrylonitrile metal oxide by isobutylene ammoxidation were used as output values. The dataset was constructed, normalized, and divided into training set and test set. Build a machine learning model, train the machine learning model using a training set to obtain a mature machine learning model, and evaluate the predictive ability of the model using a test set. Determine the target active components for screening the desired metal oxide catalyst for the isobutylene ammoxidation process to prepare methacrylonitrile; A well-trained machine learning model is used to predict the conversion rate and selectivity of the identified active components, obtain the combination of active components with high conversion rate and high selectivity and the atomic percentage of each element in the combination, and use them as the active components of the optimal metal oxide catalyst.

5. A method for preparing a catalyst for the isobutylene ammoxidation process to prepare methacrylonitrile as described in any one of claims 1-4, characterized in that, Including the following steps: (1) Dissolve the molybdenum soluble salt in deionized water and stir until clear, then add a carrier to obtain solution A; (2) Dissolve bismuth soluble salt, iron soluble salt, magnesium soluble salt, nickel soluble salt, cerium soluble salt and 2~4 mol / L nitric acid in deionized water and stir until clear to obtain solution B; (3) Dissolve tetrabutyl titanate in anhydrous ethanol and stir until homogeneous to obtain solution C; (4) Dissolve antimony trioxide in an aqueous solution of tartaric acid or citric acid and stir until homogeneous to obtain solution D; (5) Slowly add solutions B, C, and D to solution A under water bath conditions and stir until homogeneous to obtain a composite solution. Then adjust the pH to 5-6 with ammonia water to obtain solution E. (6) Let solution E stand for 2-10 hours, then filter it, and wash it with deionized water until neutral. Pulverize the cleaned filter cake and add potassium nitrate solution. Stir for 30-60 minutes to obtain a mixed slurry. (7) The mixed slurry is dried and calcined to obtain a catalyst for the preparation of methacrylonitrile by the isobutylene ammoxidation method.

6. The method for preparing a catalyst for the isobutylene ammoxidation process to prepare methacrylonitrile according to claim 5, characterized in that, The water bath temperature in step (5) is 50~100℃.

7. The method for preparing a catalyst for the isobutylene ammoxidation process to prepare methacrylonitrile according to claim 5, characterized in that, In step (5), ultrasonic enhancement and / or ultraviolet enhancement are introduced during the mixing of solutions B, C, and D with solution A and the adjustment of pH. The power of the ultrasonic enhancement is 800~1500W, and the time is 10~30min; The UV-enhanced irradiation intensity is 200~800W / m. 2 The time is 1 to 6 hours.

8. The method for preparing a catalyst for the isobutylene ammoxidation process to prepare methacrylonitrile according to claim 5, characterized in that, In step (7), the drying temperature is 100~200℃ and the drying time is 2~5h; the calcination temperature is 400~600℃ and the calcination time is 3~6h, and the calcination atmosphere is air.

9. The use of the catalyst according to any one of claims 1-4 in the preparation of methacrylonitrile by the ammoxidation of isobutylene.

10. The application according to claim 9, characterized in that, The catalyst according to any one of claims 1-4 is added to a fluidized bed reactor, with the inlet pressure set at 0.1~0.3MPa, the reaction temperature at 380~430℃, the feed volume ratio of isobutylene, ammonia, and air at 1:1.0~1.6:9~15, and the total weight hourly space velocity of the reactants at 0.5~4h. -1 Methacrylonitrile is obtained by ammonia oxidation.

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