Mesoporous TS-1 molecular sieve catalyst synergistically modified by transition metal Fe-Co-Ni ternary system, and preparation method and application thereof

Abstract

The invention provides a transition metal Fe-Co-Ni ternary system synergistically modified mesoporous TS-1 molecular sieve catalyst, and a preparation method and application thereof in the technical field of molecular sieve catalytic materials. The preparation method of the molecular sieve catalyst comprises the following steps: S1, obtaining Fe-Co-Ni ternary magnetic nanoparticles by a coprecipitation method; s2, carrying out surface modification by a silane hydrolysis method to obtain a Fe-Co-Ni-coated SiO2 core-shell structure; and S3, carrying out in-situ hydrothermal crystallization to construct the Fe-Co-Ni / mesoporous TS-1 molecular sieve catalyst. Through cooperation of the core-shell structure and the ternary transition metal, the shape-selective catalysis advantage of TS-1 is perfectly fused with the oxidation-reduction characteristic of the transition metal and the separation convenience of a magnetic material. The prepared molecular sieve catalyst has the performance advantages of efficient catalysis, high selectivity, easiness in separation and long service life, and can be used for ammoximation reaction of acetone under a liquid phase condition.

Description

Technical Field

[0001] This invention belongs to the field of molecular sieve catalytic materials technology, specifically relating to a transition metal Fe-Co-Ni ternary system synergistic modification of mesoporous TS-1 molecular sieve catalyst that can be used for acetone ammonoxime reaction, its preparation method and application. Background Technology

[0002] TS-1 molecular sieves, represented by ZSM-5, have a three-dimensional channel structure composed of Z-shaped channels and elliptical straight channels. The four-coordinated Ti in its framework serves as the active center for selective oxidation reactions, and the formed Si-O-Ti bonds endow it with catalytic oxidation activity and shape-selective catalysis. Because it does not contain strongly acidic Al ions, TS-1 exhibits strong hydrophobicity, making it suitable for organic reactions using H₂O₂ as the oxidant.

[0003] The catalytic system composed of TS-1 and H2O2 exhibits high selectivity and environmental friendliness in reactions such as olefin epoxidation, ketone ammoniation, and aromatic hydroxylation, which aligns with the development direction of green chemistry.

[0004] Acetone oxime is a high-performance antioxidant, low in toxicity, environmentally friendly, and with strong reducing properties, making it an excellent protective agent for feedwater boilers. Traditional production processes for acetone oxime include the hydroxylamine hydrochloride method and the hydroxylamine sulfate method, both of which suffer from drawbacks such as complex processes, numerous byproducts, and large emissions of waste. Research indicates that the catalytic ammoniation of acetone to acetone oxime using titanium-silicon molecular sieves (TS-1) is an environmentally friendly catalytic process with advantages such as high raw material utilization, high catalytic efficiency, mild reaction conditions, low energy consumption, and environmental friendliness. Examples of such applications include CN1556096A, CN103172534A, CN103288675B, and CN110981749B. Although titanium-silicon molecular sieve TS-1 is a highly efficient catalytic material, particularly excelling in the ammoniation of acetone, it still has inherent limitations, such as mass transfer constraints, loss and deactivation of titanium activity, low H2O2 utilization efficiency, and difficulties in separation and recovery.

[0005] Therefore, further improving the activity of titanium-silicon molecular sieve catalysts in the catalytic synthesis process has become one of the key focuses of synthetic oxime technology research and development. Summary of the Invention

[0006] The purpose of this invention is to provide a transition metal Fe-Co-Ni ternary system synergistic modification mesoporous TS-1 molecular sieve catalyst, its preparation method and application. The obtained molecular sieve catalyst can overcome the technical difficulties of existing TS-1 molecular sieve catalysts, such as mass transfer limitation, loss and deactivation of titanium activity, low H2O2 utilization efficiency and difficulty in separation and recovery, so that it can be used in the acetone ammoniation reaction.

[0007] In view of this, the technical solution of the present invention is implemented as follows: a method for preparing a transition metal Fe-Co-Ni ternary system synergistically modified mesoporous TS-1 molecular sieve catalyst, comprising the following steps: S1, Fe-Co-Ni ternary magnetic nanoparticles were obtained by coprecipitation method. Weigh Fe(NO3)3, Co(NO3)2, and Ni(NO3)2 according to the molar ratio of Fe:Co:Ni (2.2~3.8):(0.8~1.6):1, add them to water to prepare a mixed solution, add the mixed solution dropwise to water containing a precipitant, wash, dry, and calcine the obtained precipitate to obtain Fe-Co-Ni ternary magnetic nanoparticles; S2, obtaining a core-shell structured Fe-Co-Ni@SiO2 by coating SiO2 onto ternary magnetic nanoparticles. Fe-Co-Ni ternary magnetic nanoparticles were uniformly dispersed in a mixed solution of ethanol-water-ammonia, and tetraethyl orthosilicate was added dropwise to form a SiO2 shell on the surface of the metal magnetic core. The product was then collected by magnetic separation, washed, dried, and ground to obtain core-shell structured Fe-Co-Ni@SiO2 nanospheres. The amount of tetraethyl orthosilicate used was based on Si element, and the molar ratio of Ni to Si element used was 1:(4.2~6.6). S3, Fe-Co-Ni / mesoporous TS-1 molecular sieve catalyst obtained by in-situ hydrothermal crystallization. The Fe-Co-Ni@SiO2 nanospheres obtained in step S2 were mixed with water, a mesoporous agent, a template agent, a silicon source, and a titanium source in a reactor. The silicon source and titanium source were calculated as SiO2 and TiO2, respectively. The silicon source was selected as tetraethyl orthosilicate, and the titanium source was selected as one of tetraethyl titanate, tetrapropyl titanate, and tetrabutyl titanate. The template agent was tetrapropylammonium hydroxide. The molar ratio of silicon source:titanium source:template agent:water in the raw materials was 1:(0.020~0.025):(0.20~0.30):(30~50). The amount of Ni@SiO2 nanospheres added is 3.6-5.4% of the mass of tetraethyl orthosilicate added in this step. The mesoporous agent is carbon black with a pore size of 10-40 nm, and the amount of mesoporous agent is 0.15-0.35% of the mass of tetraethyl orthosilicate added in this step. After mixing, the mixture is heated to 160-180℃ for isothermal crystallization. After crystallization, the mixture is cooled, filtered, washed, and dried. Then, it is calcined at 540-580℃, ground, and shaped to obtain the target product, Fe-Co-Ni ternary magnetic metal synergistic modified mesoporous TS-1 molecular sieve catalyst.

[0008] Further, step S1 includes the following sub-steps: S1-1, according to the required molar ratio of transition metals Fe:Co:Ni, accurately weigh three nitrates and add them to water, stir to dissolve, prepare a mixed solution, and transfer it to addition funnel I; then weigh the precipitant and add it to water, stir to dissolve, prepare a precipitant buffer solution, and transfer it to addition funnel II; first add an appropriate amount of water to the reactor as the bottom liquid, heat to 85-95℃, then start vigorous stirring, and simultaneously open addition funnels I and II at a controllable rate, synchronously adjusting the rate of addition funnel II to maintain the pH of the solution in the reactor; the precipitant is at least one of sodium hydroxide and sodium carbonate, used to maintain the pH of the solution in the reactor at 10-14; S1-2, After the addition of liquid is completed, continue stirring for 2-3 hours under constant temperature conditions to promote the maturation of precipitated crystals; after the precipitate settles naturally or is attracted with the help of a magnet, pour off the supernatant, wash repeatedly with water and centrifuge until the supernatant is neutral when tested with pH paper. S1-3, the washed precipitate is dried in an oven at 110-120℃ for 10-12 hours to obtain a metal precursor; the dried metal precursor is placed in a high-temperature calcination furnace and calcined at a constant temperature of 650-750℃ for 3-5 hours under the protection of inert nitrogen gas to obtain Fe-Co-Ni ternary magnetic nanoparticles.

[0009] Furthermore, step S2 includes the following sub-steps: S2-1, The Fe-Co-Ni ternary magnetic nanoparticles obtained in step S1 are added to a solution of anhydrous ethanol, water, and ammonia, sealed, and ultrasonically treated for 40-60 minutes to obtain a uniform dispersion; the volume ratio of anhydrous ethanol:water:ammonia is 100:20:1, and the mass concentration of ammonia is 25%. S2-2, Under stirring conditions, the dispersion is heated to 40-45℃, and tetraethyl orthosilicate is slowly and dropwise added to the dispersion using a microburette. The reaction is carried out under constant temperature and stirring for 3-4 hours. The tetraethyl orthosilicate gradually hydrolyzes and condenses, forming a SiO2 shell on the surface of the metal magnetic core. After the reaction is complete (S2-3), the product is collected by magnetic separation and washed repeatedly with ethanol and water 3-5 times. It is then dried in an oven at 130-140℃ for 20-24 hours and ground to obtain core-shell structured Fe-Co-Ni@SiO2 nanospheres.

[0010] Furthermore, step S3 includes the following sub-steps: S3-1, first dissolve the template agent in water, stir and mix, then slowly add the silicon source, stir until uniformly dispersed, to obtain a silicon source solution; take the titanium source and mix with water, add an appropriate amount of solid oxalic acid and adjust the pH to 2-4, continue stirring until completely dissolved, to obtain a titanium source solution; S3-2, Add an appropriate amount of water as a base liquid to the crystallization reactor. First, add the Fe-Co-Ni@SiO2 nanospheres obtained in step S2 into the reactor and stir. Then, add the mesoporous agent and continue stirring. Next, add the silicon source liquid and titanium source liquid described in step S3-1 in sequence. Stir at room temperature for 2-3 hours to obtain a uniform mixture. Raise the temperature to 160-180℃ and crystallize at a constant temperature for 48-60 hours. S3-3, after crystallization, cool down, filter, wash, dry at 120-130℃ for 20-24 hours, then calcine at 540-580℃ for 8-10 hours, grind, and shape to obtain the target product.

[0011] A further improvement of the present invention is that the molar ratio of Fe:Co:Ni:Si elements in the Fe-Co-Ni@SiO2 nanospheres is (2.5~3.5):(1.0~1.4):1:(4.7~6.1). That is, the molar ratio of Fe:Co:Ni:Si elements in the raw materials used in steps S1 and S2 is (2.5~3.5):(1.0~1.4):1:(4.7~6.1).

[0012] The transition metal Fe-Co-Ni ternary system synergistic modification of mesoporous TS-1 molecular sieve catalyst obtained according to the above method can be used for the ammonium oxime reaction of acetone under liquid phase conditions. Tert-butanol and water are used as reaction solvents, and acetone, ammonia, and hydrogen peroxide (molar ratio 1:3:1.2) are used as reactants. The oxidative synthesis of acetone oxime is carried out in a continuous flow reactor, with the catalyst dosage being 2.4–5.2% of the mass of the acetone feedstock. Through investigation of the catalytic ammonium oxime process, under optimized reaction conditions, with a catalyst dosage of 3.8% of the acetone feedstock and a reaction temperature of 70–75 °C, an acetone conversion rate of 98.36% and an acetone oxime selectivity of 99.75% were achieved. This demonstrates higher acetone conversion rate, higher acetone oxime selectivity, higher H2O2 utilization rate, and rapid, low-cost, near-zero-loss magnetic recovery, while maintaining excellent cycle stability.

[0013] Compared with the prior art, the beneficial technical effects of the present invention are as follows: This invention achieves a perfect fusion of the shape-selective catalytic advantages of TS-1 with the redox properties of transition metals and the separation convenience of magnetic materials through a core-shell structure, synergistic use of Fe-Co-Ni ternary transition metals, and optimized mesoporous TS-1 molecular sieves. The final product is an Fe-Co-Ni / mesoporous TS-1 molecular sieve catalyst. The mesoporous TS-1 molecular sieve serves as the main catalyst and shape-selective framework, providing titanium active centers and regular micropores to ensure intrinsic activity of the ammonium oxime reaction and selectivity for acetone oxime. The use of metallic Fe as a magnetic substrate endows the molecular sieve catalyst with magnetic separation capabilities. Co, a strong redox metal, significantly enhances the activation efficiency of H2O2, exhibiting high catalytic efficiency and enhanced stability. The introduction of metallic Ni optimizes the electronic environment of Fe and Co, making the reactive substances more inclined towards the target product and facilitating the formation of finer, more stable ternary magnetic metal nanoparticles, preventing excessive aggregation of Co or Fe. The ternary synergistic activation of H2O2 by transition metals Fe, Co, and Ni complements the reaction pathway of the Ti centers in the mesoporous TS-1 molecular sieve, jointly promoting the reaction and thus improving the overall reaction rate and H2O2 utilization, suppressing side reactions, and enhancing the selectivity of acetone oxime. Leveraging the strong magnetism of the Fe-Co-Ni group, second-level magnetic separation and recovery are achieved, and the catalyst can be recycled multiple times while maintaining high activity and strong magnetism.

[0014] Therefore, the Fe-Co-Ni / mesoporous TS-1 molecular sieve catalyst prepared in this invention has the advantages of high efficiency catalysis, high selectivity, easy separation and long life, and has broad market application prospects. Detailed Implementation

[0015] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way. Example 1

[0016] A method for preparing a transition metal Fe-Co-Ni ternary system synergistically modified mesoporous TS-1 molecular sieve catalyst includes the following steps: S1, Fe-Co-Ni ternary magnetic nanoparticles were obtained by coprecipitation method. S1-1, according to the required Fe:Co:Ni molar ratio, accurately weigh 725.58g of ferric nitrate (Fe(NO3)3, Mr=241.86), 219.5316g of cobalt nitrate (Co(NO3)2, Mr=182.943), and 182.70g of nickel nitrate (Ni(NO3)2, Mr=182.70), add them to 5.2-10.4L of water, stir to dissolve, and prepare a 0.5-1mol / L mixed metal salt solution, transfer it to addition funnel I; then weigh 60g of precipitant sodium hydroxide (NaOH, Mr=40.00) and sodium carbonate (Na2CO3, Mr=105.99). Add 158.99g to 1.5-2L of water, stir to dissolve, and prepare a 1.5-2.0mol / L precipitant buffer solution. Transfer the solution to funnel II. First, add 2-3L of water to the reactor as a base solution, heat to 85-95℃, and then start vigorous stirring. Simultaneously open funnels I and II at a controllable rate, and adjust the rate of funnel II synchronously to maintain the pH stability of the solution in the reactor. The precipitants sodium hydroxide and sodium carbonate are used to maintain the pH of the solution in the reactor at 10-14, preferably 12-13.

[0017] S1-2, after the liquid addition is completed, continue stirring for 2-3 hours under constant temperature conditions to promote the maturation of the precipitated crystals; after the precipitate settles naturally or is attracted with the help of a magnet, pour off the supernatant, wash repeatedly with water and centrifuge until the supernatant is neutral when tested with pH paper.

[0018] S1-3, the washed precipitate is dried in an oven at 110-120℃ for 10-12h to obtain a metal precursor; the dried metal precursor is placed in a high-temperature calcination furnace and calcined at a constant temperature of 650-750℃ for 3-5h under inert nitrogen gas protection to obtain Fe-Co-Ni ternary magnetic nanoparticles. 2. Obtaining core-shell structured Fe-Co-Ni@SiO2

[0019] S2-1, The Fe-Co-Ni ternary magnetic nanoparticles obtained in step S1 are added to a solution containing 1000ml of anhydrous ethanol, 200ml of water and 10ml of ammonia (the corresponding volume ratio is 100:20:1 and the mass concentration of ammonia is 25%), sealed, and ultrasonically treated for 40-60 minutes to obtain a uniform dispersion.

[0020] S2-2, Under stirring conditions, the dispersion is heated to 40-45℃, and 1083.3004g of tetraethyl orthosilicate (C8H2O) is slowly and dropwise added to the dispersion using a microburette. 20 O4Si (Mr=208.327) reacts under constant temperature and continuous stirring for 3-4 hours, gradually hydrolyzing and condensing to form a SiO2 shell on the surface of the metal magnetic core.

[0021] After the reaction is complete (S2-3), the product is collected by magnetic separation and washed repeatedly with ethanol and water 3-5 times. It is then dried in an oven at 130-140℃ for 20-24 hours and ground to obtain core-shell structured Fe-Co-Ni@SiO2 nanospheres.

[0022] S3, Fe-Co-Ni / mesoporous TS-1 molecular sieve catalyst obtained by in-situ hydrothermal crystallization. S3-1, first take 50.84g of tetrapropylammonium hydroxide (C 12 H 29 Dissolve NO, Mr=203.36) in 200ml of water, stir to mix, and then slowly add 208.327g of tetraethyl orthosilicate (C8H2O). 20 O4Si, Mr=208.327), stirred until uniformly dispersed to obtain a silicon source solution; 228.109g of tetraethyl titanate (C8H) was taken. 20 O4Ti (Mr=228.109) is mixed with 200ml of water, an appropriate amount of solid oxalic acid is added and the pH is adjusted to 2-4, and stirring is continued until completely dissolved to obtain a titanium source solution.

[0023] S3-2, add the remaining 320ml of water to the crystallization reactor as the base liquid. First, weigh 9.3747g of Fe-Co-Ni@SiO2 obtained in step S2 and add it to the reactor. Stir, then add 0.5208g of carbon black (C, Mr=12) as a mesoporous agent with a pore size of 10-40nm. Continue stirring, then add the silicon source liquid and titanium source liquid described in step S3-1 in sequence. Stir at room temperature for 2-3 hours to obtain a uniform mixture. Raise the temperature to 160-180℃ and crystallize at a constant temperature for 48-60 hours.

[0024] In steps S3-1 and S3-2, the total amount of water used is 720 ml.

[0025] After crystallization, S3-3 is cooled, filtered, washed, dried at 120-130℃ for 20-24 hours, calcined at 540-580℃ for 8-10 hours, ground, and shaped to obtain the target product, the Fe-Co-Ni ternary system synergistic modification mesoporous TS-1 molecular sieve catalyst, namely the Fe-Co-Ni / mesoporous TS-1 molecular sieve catalyst.

[0026] In step S3-1, the amount of Fe-Co-Ni@SiO2 added is 4.5% of the mass of the silicon source tetraethyl orthosilicate in step S3. The proportion of the mesoporous agent used is 0.25% of the mass of the silicon source tetraethyl orthosilicate in step S3.

[0027] In step S1, co-precipitation is used to obtain uniform and high-performance Fe-Co-Ni ternary magnetic nanoparticles. This method involves the simultaneous precipitation of transition metal ions in solution, is relatively simple to operate, and is easy to scale up. The magnetic strength and redox properties are further determined by adjusting the ratio of Fe, Co, and Ni. To obtain a high-purity product, nitrates are preferred because nitrate ions completely decompose during subsequent calcination, leaving no residual anions to interfere. Sodium hydroxide and sodium carbonate, as precipitation buffers, can simultaneously provide OH-. - and CO3 2- This allows for the formation of an ideal co-precipitation structure with metal ions, enabling more precise control and stable maintenance of the pH of the solution within the reactor at 12-13. Finally, the obtained precipitated metal precursor is calcined at high temperature, which crystallizes the amorphous precursor into the target product, Fe-Co-Ni ternary magnetic nanoparticles, while removing residual volatile impurities. Furthermore, the metal structure provides support, and high-temperature calcination also contributes to the high mechanical strength and thermal stability of the composite material.

[0028] In step S2, ethanol, as a common polar solvent, can effectively reduce the surface tension of the metallic magnetic particles and reduce particle aggregation. The main reason for ultrasonic dispersion of the metallic magnetic particles in ethanol is to utilize the cavitation and mechanical effects generated by ultrasound to effectively break particle aggregation and promote uniform dispersion. Considering that the subsequent synthesis environment of TS-1 molecular sieve is a strongly alkaline high-temperature hydrothermal system, the Fe-Co-Ni ternary magnetic nanoparticles obtained in this environment are extremely unstable and will be strongly corroded and dissolved, leading to magnetic failure or even destruction of the entire structure. Therefore, in order to provide the most reliable protection and create the most ideal surface chemical environment for the successful growth of TS-1, the solution of this invention is the classic Stober method, that is, using a mixed solvent of ethanol and water, under the action of 25% concentrated ammonia water as an alkaline catalyst, tetraethyl orthosilicate undergoes hydrolysis and condensation. During the process, the dropping rate of tetraethyl orthosilicate is controlled, added drop by drop, slowly and uniformly, to ensure sufficient reaction, and finally uniformly deposited on the surface of Fe-Co-Ni ternary magnetic nanoparticles to form a complete and dense SiO2 inert protective layer. This not only prevents magnetic core corrosion but also inhibits the aggregation of magnetic nanoparticles. More importantly, the SiO2 layer and the TS-1 shell are made of the same chemical substance, providing perfect chemical compatibility.

[0029] In step 3, to successfully prepare the high-performance Fe-Co-Ni / mesoporous TS-1 molecular sieve catalyst, the modified Fe-Co-Ni@SiO2 was uniformly dispersed in the TS-1 molecular sieve synthesis raw material, and then hydrothermal crystallization was carried out in a crystallization reactor to promote uniform embedding or bonding with the TS-1 molecular sieve. To optimize the pore structure and promote the dispersion of active components, carbon black with a suitable pore size was selected as the mesoporous agent, which resulted in abundant and interconnected mesoporous TS-1 molecular sieves. Furthermore, the mesoporous agent is burned off during the molecular sieve calcination, without affecting the intrinsic catalytic performance of the TS-1 molecular sieve.

[0030] The Fe-Co-Ni / mesoporous TS-1 molecular sieve catalyst prepared in this invention is used for the ammoniation of acetone under liquid-phase conditions. Tert-butanol and water are used as reaction solvents, and acetone, ammonia, and hydrogen peroxide (molar ratio 1:3:1.2) are used as reactants. The oxidative synthesis of acetone oxime is carried out in a continuous flow reactor. The reaction temperature was observed to be 70–75 °C, and the catalyst dosage was 3.8% of the mass of the acetone reactant. After the reaction, the reactants and products were collected separately, and the conversion rate of acetone and the selectivity of acetone oxime were determined using high-performance liquid chromatography (HPLC, Agilent 1260), thereby obtaining the yield of acetone oxime.

[0031] Through the investigation of the catalytic ammonium oxime process, Example 1, under the optimized reaction conditions and with a catalyst dosage of 3.8% of the mass of the raw material acetone, achieved an acetone conversion rate of 98.36% and an acetone oxime selectivity of 99.75%. This resulted in higher acetone conversion rate, higher acetone oxime selectivity, higher H2O2 utilization rate, and rapid, low-cost, and near-zero-loss magnetic recovery, while still maintaining excellent cycle stability. Example 2

[0032] Based on Example 1, by analyzing the SiO content of each raw material in step S3 of the Fe-Co-Ni / mesoporous TS-1 molecular sieve catalyst prepared in this invention... 2、 The molar ratio of TiO2, template agent and water was investigated, and other steps and conditions were the same as in Example 1.

[0033] (1) Only the molar ratio of TiO2 in the raw materials was changed, while the molar ratio of other raw materials remained unchanged. All other steps and conditions were the same as in Example 1. The crystallization results are shown in the table below.

[0034]

[0035] (2) Only the molar ratio of the template agent in the raw materials was changed, while the molar ratio of other raw materials remained unchanged. All other steps and conditions were the same as in Example 1. The crystallization results are shown in the table below.

[0036]

[0037] (3) Only the molar ratio of water in the raw materials was changed, while the molar ratio of other raw materials remained unchanged. All other steps and conditions were the same as in Example 1. The crystallization results are shown in the table below.

[0038]

[0039] The crystallization results from Examples 2-1 to 2-12 and Comparative Examples 2a to 2l show that when the molar ratio of SiO2:TiO2:template:water in each raw material is 1:(0.020-0.025):(0.20-0.30):(30-50) in step S3, the TS-1 molecular sieve prepared by crystallization has an MFI-type topology and a relative crystallinity ≥98%. Silicon in the raw materials serves as the main framework, providing the three-dimensional pore structure of the TS-1 molecular sieve and forming Si-O-Ti bonds with titanium, enhancing catalytic activity and shape selectivity. The template agent regulates the pore structure and crystallization process of the molecular sieve, determining the morphology and properties of the final crystallized product. Water, as a solvent and reaction medium, participates in the hydrolysis and crystallization process, adjusting the alkalinity and ion concentration of the reaction system and promoting the formation of the molecular sieve.

[0040] As a further optimization, when the molar ratio of SiO2:TiO2:templator:water in each raw material is 1:0.023:0.25:40, the corresponding maximum relative crystallinity is 99.72%. This indicates that the optimal molar ratio in the raw materials can yield TS-1 molecular sieves with high crystallinity, high purity, and high regularity. Example 3

[0041] Based on Example 2, the crystallization results of different titanium sources in the raw materials were further investigated. All other steps and conditions were the same as in Example 1. The crystallization results are shown in the table below.

[0042]

[0043] The results show that tetraethyl titanate, tetrapropyl titanate, and tetrabutyl titanate can all be used as titanium sources, and the TS-1 molecular sieves obtained from each source have relatively high crystallinity, indicating that there is essentially no significant difference in their technical effects. In practice, tetrabutyl titanate has a slower hydrolysis rate, resulting in a slightly lower crystallinity, while tetrapropyl titanate is more expensive. Therefore, tetraethyl titanate is the preferred titanium source, as its hydrolysis rate is very well matched with that of silicon sources, making it easier to obtain TS-1 molecular sieves with high crystallinity. Example 4

[0044] Based on Example 1, the technical effect of Fe-Co-Ni@SiO2 on the catalytic performance of molecular sieve catalysts was studied. The effect of different molar ratios of elements in Fe-Co-Ni@SiO2 on the catalytic performance of acetone ammoniation reaction was screened.

[0045] (1) Only the molar ratio of Fe was changed, while the molar ratios of other elements remained unchanged. All other steps and conditions were the same as in Example 1. The results are shown in the table below.

[0046]

[0047] (2) Only the molar ratio of Co was changed, while the molar ratios of other elements remained unchanged. All other steps and conditions were the same as in Example 1. The results are shown in the table below.

[0048]

[0049] (3) Only the molar ratio of Si was changed, while the molar ratios of other elements remained unchanged. All other steps and conditions were the same as in Example 1. The results are shown in the table below.

[0050]

[0051] The results of Examples 4-1 to 4-12 and Comparative Examples 4a to 4l above show that when the molar ratio of Fe:Co:Ni:Si in Fe-Co-Ni@SiO2 is (2.2–3.8):(0.8–1.6):1:(4.2–6.6), the catalytic results of the Fe-Co-Ni / mesoporous TS-1 molecular sieve catalyst obtained in this invention are that the conversion rate of acetone is greater than 98% and the selectivity of acetone oxime is greater than 99%. Preferably, when the molar ratio of Fe:Co:Ni:Si in Fe-Co-Ni@SiO2 is (2.5–3.5):(1.0–1.4):1:(4.7–6.1), the yield of acetone oxime is higher than 97%. This indicates that the ternary synergistic activation of H2O2 by the transition metals Fe, Co, and Ni can complement the reaction pathway of the Ti center in the mesoporous TS-1 molecular sieve, jointly promoting the reaction, thereby improving the overall reaction rate and H2O2 utilization rate, and suppressing side reactions. Among them, the mesoporous TS-1 molecular sieve serves as the main catalyst and shape-selective framework, providing titanium active centers and regular micropores to ensure the intrinsic activity of the ammonium oxime reaction and the selectivity of acetone oxime; the use of metallic Fe as a magnetic substrate endows the molecular sieve catalyst with magnetic separation capability; while Co is a strong redox metal that can significantly improve the activation efficiency of H2O2, exhibiting the characteristics of high-efficiency catalysis and enhanced stability; the introduction of metallic Ni can optimize the electronic environment of Fe and Co, making the reactive substances more inclined to the target product, and further facilitating the formation of finer and more stable ternary magnetic metal nanoparticles, preventing excessive aggregation of Co or Fe. Example 5

[0052] Based on Example 1, the effect of the addition ratio of Fe-Co-Ni@SiO2 on the synthesis of Fe-Co-Ni / mesoporous TS-1 molecular sieve catalyst was further screened. All other steps and conditions were the same as in Example 1. The results are shown in the table below.

[0054] Comparative Example 5a in the table represents the Fe-Co-Ni / mesoporous TS-1 molecular sieve catalyst without the addition of Fe-Co-Ni@SiO2, indicating that the catalytic performance of using mesoporous TS-1 molecular sieve alone is poor, with low conversion and selectivity. As the proportion of Fe-Co-Ni@SiO2 added increases, the conversion and selectivity first increase and then decrease, indicating that the synergistic modification of the mesoporous TS-1 molecular sieve by the Fe-Co-Ni ternary transition metal helps to improve catalytic performance. Therefore, the amount of Fe-Co-Ni@SiO2 added is 3.6–5.4% of the mass of the silicon source tetraethyl orthosilicate in step S3, with a preferred value of 4.5%. Example 6

[0055] Based on Example 1, the effect of the addition ratio of mesoporous agent on the catalytic effect of Fe-Co-Ni / mesoporous TS-1 molecular sieve catalyst was further screened. All other steps and conditions were the same as in Example 1. The results are shown in the table below.

[0057] Comparative Example 6a in the table represents the catalyst without the addition of a mesoporous agent, exhibiting poor catalytic performance. The conversion rate and selectivity of the Fe-Co-Ni / mesoporous TS-1 molecular sieve catalyst initially increased and then decreased with the addition of a mesoporous agent, indicating that the introduction of a mesoporous agent with a pore size of 10–40 nm promotes shape selectivity in the micropores of TS-1, preferentially generating and diffusing size-matched acetone oxime molecules. Therefore, the optimal addition ratio of the mesoporous agent is 0.15–0.35% of the mass of the silicon source tetraethyl orthosilicate in step S3, with a preferred value of 0.25%. Example 7

[0058] Based on Example 1, the effect of the addition ratio of Fe-Co-Ni / mesoporous TS-1 molecular sieve catalyst on the acetone ammonium oxime reaction was further screened. All other steps and conditions were the same as in Example 1. The results are shown in the table below.

[0060] Comparative Example 7a in the table represents the catalyst without Fe-Co-Ni / mesoporous TS-1 molecular sieve catalyst, exhibiting extremely poor catalytic performance. As the amount of molecular sieve catalyst increases, the conversion rate and selectivity of the catalyst first increase and then decrease. This indicates that the catalyst dosage is 2.4–5.2% of the mass of the raw material acetone.

[0061] Under optimized reaction conditions, with a catalyst dosage of 3.8% of the mass of the raw material acetone, an acetone conversion rate of 98.36% and an acetone oxime selectivity of 99.75% were achieved. This resulted in higher acetone conversion, higher acetone oxime selectivity, and higher H2O2 utilization.

[0062] After the reaction, the used Fe-Co-Ni / mesoporous TS-1 molecular sieve catalyst can be completely separated from the liquid phase within seconds using only a permanent magnet, resulting in an extremely simple process with very low loss. The catalyst was repeatedly recycled 10 times without any catalytic performance degradation; its acetone conversion rate remained above 98%, and the selectivity for acetone oxime remained above 99%. This indicates that the classic Stober method effectively achieves uniform deposition on the surface of Fe-Co-Ni ternary magnetic nanoparticles, forming a complete and dense inert SiO2 protective layer. This layer prevents magnetic core corrosion and inhibits the aggregation of magnetic nanoparticles. More importantly, the SiO2 layer and the TS-1 shell are made of the same chemical substance, providing perfect chemical compatibility. Therefore, the stable Fe-Co-Ni@SiO2 structure itself has strong resistance to leaching. Furthermore, thanks to the strong magnetism of the Fe-Co-Ni group, second-level magnetic separation and recovery are achieved, allowing the catalyst to be recycled while maintaining high activity and strong magnetism.

[0063] In summary, this invention achieves a perfect fusion of the shape-selective catalytic advantages of TS-1 with the redox properties of transition metals and the separation convenience of magnetic materials through a core-shell structure, synergistic use of Fe-Co-Ni ternary transition metals, and optimized mesoporous TS-1 molecular sieves. This results in an Fe-Co-Ni / mesoporous TS-1 molecular sieve catalyst. The mesoporous TS-1 molecular sieve serves as the main catalyst and shape-selective framework, providing titanium active centers and well-defined micropores to ensure intrinsic activity in the ammonium oxime reaction and selectivity for acetone oxime. The use of metallic Fe as a magnetic substrate endows the molecular sieve catalyst with magnetic separation capabilities. Co, a strong redox metal, significantly enhances the activation efficiency of H2O2, exhibiting both high catalytic efficiency and enhanced stability. The introduction of metallic Ni optimizes the electronic environment of Fe and Co, making the reactive substances more inclined towards the target product and facilitating the formation of finer, more stable ternary magnetic metal nanoparticles, preventing excessive aggregation of Co or Fe. The ternary synergistic activation of H2O2 by transition metals Fe, Co, and Ni complements the reaction pathway of the Ti centers in the mesoporous TS-1 molecular sieve, jointly promoting the reaction and thus improving the overall reaction rate and H2O2 utilization, suppressing side reactions, and enhancing the selectivity of acetone oxime. Leveraging the strong magnetism of the Fe-Co-Ni group, second-level magnetic separation and recovery are achieved, and the catalyst can be recycled multiple times while maintaining high activity and strong magnetism.

[0064] Therefore, the Fe-Co-Ni / mesoporous TS-1 molecular sieve catalyst prepared in this invention has the advantages of high efficiency catalysis, high selectivity, easy separation and long life, and has broad market application prospects.

[0065] This invention is not limited to the above embodiments. Based on the technical solutions disclosed in this invention, those skilled in the art can make some substitutions and modifications to some of the technical features without creative effort, and all such substitutions and modifications are within the protection scope of this invention.

Claims

1. A preparation method of a mesoporous TS-1 molecular sieve catalyst synergistically modified by a transition metal Fe-Co-Ni ternary system, characterized in that, Includes the following steps: S1, Fe-Co-Ni ternary magnetic nanoparticles were obtained by coprecipitation method. Weigh Fe(NO3)3, Co(NO3)2, and Ni(NO3)2 according to the molar ratio of Fe:Co:Ni (2.2~3.8):(0.8~1.6):1, add them to water to prepare a mixed solution, add the mixed solution dropwise to water containing a precipitant, wash, dry, and calcine the obtained precipitate to obtain Fe-Co-Ni ternary magnetic nanoparticles; S2, obtaining a core-shell structured Fe-Co-Ni@SiO2 by coating SiO2 onto ternary magnetic nanoparticles. Fe-Co-Ni ternary magnetic nanoparticles were uniformly dispersed in a mixed solution of ethanol-water-ammonia, and tetraethyl orthosilicate was added dropwise to form a SiO2 shell on the surface of the metal magnetic core. The product was then collected by magnetic separation, washed, dried, and ground to obtain core-shell structured Fe-Co-Ni@SiO2 nanospheres. The amount of tetraethyl orthosilicate used was based on Si element, and the molar ratio of Ni to Si element used was 1:(4.2~6.6). S3, Fe-Co-Ni / mesoporous TS-1 molecular sieve catalyst obtained by in-situ hydrothermal crystallization. The Fe-Co-Ni@SiO2 nanospheres obtained in step S2 were mixed with water, a mesoporous agent, a template agent, a silicon source, and a titanium source in a reactor. The silicon source and titanium source were calculated as SiO2 and TiO2, respectively. The silicon source was selected as tetraethyl orthosilicate, and the titanium source was selected as one of tetraethyl titanate, tetrapropyl titanate, and tetrabutyl titanate. The template agent was tetrapropylammonium hydroxide. The molar ratio of silicon source:titanium source:template agent:water in the raw materials was 1:(0.020~0.025):(0.20~0.30):(30~50). The amount of Ni@SiO2 nanospheres added is 3.6-5.4% of the mass of tetraethyl orthosilicate added in this step. The mesoporous agent is carbon black with a pore size of 10-40 nm, and the amount of mesoporous agent is 0.15-0.35% of the mass of tetraethyl orthosilicate added in this step. After mixing, the mixture is heated to 160-180℃ for isothermal crystallization. After crystallization, the mixture is cooled, filtered, washed, and dried. Then, it is calcined at 540-580℃, ground, and shaped to obtain the target product, Fe-Co-Ni ternary magnetic metal synergistic modified mesoporous TS-1 molecular sieve catalyst.

2. The preparation method of the transition metal Fe-Co-Ni ternary system synergistically modified mesoporous TS-1 molecular sieve catalyst according to claim 1, characterized in that, Step S1 includes the following sub-steps: S1-1, according to the required molar ratio of transition metals Fe:Co:Ni, accurately weigh three nitrates and add them to water, stir to dissolve, prepare a mixed solution, and transfer it to addition funnel I; then weigh the precipitant and add it to water, stir to dissolve, prepare a precipitant buffer solution, and transfer it to addition funnel II; first add an appropriate amount of water to the reactor as the bottom liquid, heat to 85-95℃, then start vigorous stirring, and simultaneously open addition funnels I and II at a controllable rate, synchronously adjusting the rate of addition funnel II to maintain the pH of the solution in the reactor; the precipitant is at least one of sodium hydroxide and sodium carbonate, used to maintain the pH of the solution in the reactor at 10-14; S1-2, after the liquid addition is completed, continue stirring for 2-3 hours under constant temperature conditions to promote the maturation of the precipitated crystals; after the precipitate settles naturally or is attracted with the help of a magnet, pour off the supernatant, wash repeatedly with water and centrifuge until the supernatant is neutral when tested with pH paper. S1-3, the washed precipitate is dried in an oven at 110-120℃ for 10-12 hours to obtain a metal precursor; the dried metal precursor is placed in a high-temperature calcination furnace and calcined at a constant temperature of 650-750℃ for 3-5 hours under the protection of inert nitrogen gas to obtain Fe-Co-Ni ternary magnetic nanoparticles.

3. The preparation method of the transition metal Fe-Co-Ni ternary system synergistically modified mesoporous TS-1 molecular sieve catalyst according to claim 1, characterized in that, Step S2 includes the following sub-steps: S2-1, The Fe-Co-Ni ternary magnetic nanoparticles obtained in step S1 are added to a solution of anhydrous ethanol, water, and ammonia, sealed, and ultrasonically treated for 40-60 minutes to obtain a uniform dispersion; the volume ratio of anhydrous ethanol:water:ammonia is 100:20:1, and the mass concentration of ammonia is 25%. S2-2, Under stirring conditions, the dispersion is heated to 40-45℃, and tetraethyl orthosilicate is slowly and dropwise added to the dispersion using a microburette. The reaction is carried out under constant temperature and stirring for 3-4 hours. The tetraethyl orthosilicate gradually hydrolyzes and condenses, forming a SiO2 shell on the surface of the metal magnetic core. After the reaction is complete (S2-3), the product is collected by magnetic separation and washed repeatedly with ethanol and water 3-5 times. It is then dried in an oven at 130-140℃ for 20-24 hours and ground to obtain core-shell structured Fe-Co-Ni@SiO2 nanospheres.

4. The preparation method of the transition metal Fe-Co-Ni ternary system synergistically modified mesoporous TS-1 molecular sieve catalyst according to claim 1, characterized in that, Step S3 includes the following sub-steps: S3-1, first dissolve the template agent in water, stir and mix, then slowly add the silicon source, stir until uniformly dispersed, to obtain a silicon source solution; take the titanium source and mix with water, add an appropriate amount of solid oxalic acid and adjust the pH to 2-4, continue stirring until completely dissolved, to obtain a titanium source solution; S3-2, Add an appropriate amount of water as a base liquid to the crystallization reactor. First, add the Fe-Co-Ni@SiO2 nanospheres obtained in step S2 into the reactor and stir. Then, add the mesoporous agent and continue stirring. Next, add the silicon source liquid and titanium source liquid described in step S3-1 in sequence. Stir at room temperature for 2-3 hours to obtain a uniform mixture. Raise the temperature to 160-180℃ and crystallize at a constant temperature for 48-60 hours. S3-3, after crystallization, is cooled, filtered, washed, dried at 120-130℃ for 20-24 hours, then calcined at 540-580℃ for 8-10 hours, ground, and shaped to obtain the target product.

5. The preparation method of the transition metal Fe-Co-Ni ternary system synergistically modified mesoporous TS-1 molecular sieve catalyst according to claim 1, characterized in that, Its features are: The molar ratio of Fe:Co:Ni:Si elements in the Fe-Co-Ni@SiO2 nanospheres is (2.5~3.5):(1.0~1.4):1:(4.7~6.1).

6. A transition metal Fe-Co-Ni ternary system synergistic modification of mesoporous TS-1 molecular sieve catalyst, characterized in that: Prepared according to the method of any one of claims 1-6.

7. The use of the transition metal Fe-Co-Ni ternary system synergistic modification mesoporous TS-1 molecular sieve catalyst according to claim 6, characterized in that: The Fe-Co-Ni / mesoporous TS-1 molecular sieve catalyst is used for the ammonification reaction of acetone under liquid phase conditions. Tert-butanol and water are used as reaction solvents, and acetone, ammonia and hydrogen peroxide are used as reaction raw materials. The oxidative synthesis of acetone oxime is carried out in a continuous flow reactor. The amount of catalyst used is 2.4 to 5.2% of the mass of the raw material acetone.

8. The use of the transition metal Fe-Co-Ni ternary system synergistic modification mesoporous TS-1 molecular sieve catalyst according to claim 7, characterized in that: The amount of catalyst used is 3.8% of the mass of the raw material acetone.

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