Preparation method of MOFs-derived layered porous titanium dioxide-based monolithic photocatalyst, product and application

Abstract

The invention relates to a preparation method and application of an MOFs-derived layered porous titanium dioxide-based monolithic photocatalyst, a layered porous nano TiO2 / NC catalyst is constructed by utilizing the structural advantages of an MOFs material, and the visible light catalytic reaction activity and stability are greatly improved; furthermore, controllable continuous production of the monolithic TiO2-based catalyst is realized through a high-pressure airless spraying immobilization technology, the problems of difficulty in recycling and activity loss in actual working conditions of a powder catalyst are solved, and the monolithic TiO2-based catalyst is successfully applied to deep treatment of industrial sewage.

Description

Technical Field

[0001] This invention relates to a method for preparing a MOFs-derived layered porous titanium dioxide-based monolithic photocatalyst, as well as its products and applications. Utilizing the structural characteristics of the MOFs framework, it promotes strong interactions between NC and TiO2, thereby facilitating the transport of photogenerated electrons, and is applicable to the field of wastewater treatment. Background Art

[0002] Industrial pollution of water bodies severely impacts urban sustainable development, making efficient pollution control imperative with strong urging from environmental protection departments. Photocatalytic oxidation technology is an important advanced oxidation technology in water treatment, offering advantages over conventional technologies such as milder reaction conditions, more thorough treatment, fewer toxic intermediate products, and simpler operation. The key factor determining the activity of photocatalytic oxidation is the photocatalyst. Among numerous photocatalytic materials, semiconductor TiO2 is inexpensive, non-toxic, and possesses good chemical stability, making it widely used in the field of photocatalysis. However, for wide-bandgap semiconductors, the optical response range is limited to the ultraviolet region, and the rapid recombination rate of photogenerated electron-hole pairs are major issues restricting their practical application.

[0003] Modifying or compositing with non-metallic elements to form heterojunctions can effectively improve the separation efficiency of photogenerated carriers and expand the optical response range. In recent years, MOFs, due to their highly ordered pore structure and ultra-high specific surface area, have been used as precursors for porous metal oxides. Studies have found that derived TiO2 catalysts prepared using MIL-125 as a precursor possess the structural characteristics of MOF materials and exhibit excellent photocatalytic activity.

[0004] However, in practical photocatalytic applications, the direct recovery of porous materials is limited by solid-liquid separation after pollutant degradation. Recovering powdered catalysts from wastewater typically involves laborious filtration or centrifugation, which is not only time-consuming but also results in partial loss of the photocatalyst, hindering its reusability. Based on this problem, catalyst immobilization is currently the most effective solution. However, the choice of immobilization method and support directly affects the catalytic performance and stability of the supported catalyst. However, common supports such as silica particles, activated carbon, biomass, and mesoporous molecular sieves, due to their small size, low mechanical strength, or easy loss of active components, cannot completely solve the problems of low recovery rate and poor activation performance of powdered catalysts after immobilization.

[0005] Activated alumina and copper foam are porous functional materials that, as catalyst supports, not only improve the contact surface between active components and pollutants, accelerating catalytic reactions, but also promote the rapid separation of photocatalysts from wastewater, reducing water treatment costs. The activity of photocatalysts is closely related to their preparation method. Compared to traditional impregnation and co-precipitation methods, spraying not only promotes the uniform distribution of active components but also offers good controllability and time savings, making it suitable for industrial-scale production. Summary of the Invention

[0006] To address the issues of insufficient catalytic activity and powder recycling in current TiO2-based photocatalysts, this invention utilizes MOFs framework structures to construct layered porous TiO2 / NC catalysts, which are then further gas-free sprayed onto porous supports to promote catalyst recycling. The purpose of this invention is to provide a method for preparing MOFs-derived layered porous titanium dioxide-based monolithic photocatalysts.

[0007] Another object of the present invention is to provide a MOFs-derived layered porous titanium dioxide-based monolithic photocatalyst product prepared by the above method.

[0008] Another object of the present invention is to provide an application of the above-mentioned product.

[0009] The objective of this invention is achieved through the following scheme: a method for preparing a MOFs-derived layered porous titanium dioxide-based monolithic photocatalyst, characterized by utilizing a reduction-passivation process to achieve non-metallic C and N doping, promoting electron trapping, suppressing the recombination of photogenerated electrons and holes, and solving the practical problem of powder catalyst recovery based on the construction of a monolithic catalyst, specifically including the following steps: (1) Under magnetic stirring, tetrabutyl titanate was dissolved in N,N-dimethylformamide (DMF). Terephthalic acid was weighed and dissolved in DMF according to a certain molar ratio of Ti source to amino terephthalic acid ligand of 1:(4~8). Then, the tetrabutyl titanate solution was added dropwise to the ligand solvent. After the addition was complete, it was transferred to a polytetrafluoroethylene reaction vessel. (2) Adjust the reaction temperature and ultrasonic frequency to carry out ultrasonic-hydrothermal synergistic reaction of the mixed solution in (1) for 20 h; after the reaction is completed and cooled to room temperature, centrifuge to collect the precipitate, wash and dry to obtain MIL-125(Ti); (3) The product in (2) is placed in a tube furnace for in-situ reduction-passivation treatment, that is, the reduction atmosphere is controlled to 5%~10% H2 / Ar2, calcined at 500~700 ℃, and passivated at 25~300 ℃; (4) Disperse the product in (4) into anhydrous ethanol and stir continuously; use high pressure airless spraying immobilization technology to fix the active component onto the porous support, control the atomization pressure, and place it in a muffle furnace for calcination treatment to obtain MOFs-derived layered porous TiO2-based monolithic photocatalyst TiO2 / NC.

[0010] This invention enables simultaneous control of porous and non-metallic doping by in-situ reduction and passivation treatment of NH2-MIL-125, effectively simplifying the preparation process.

[0011] In step (2), the reaction temperature is 150~180℃ and the ultrasonic frequency is 300~600 Hz.

[0012] In step (3), the mixture is calcined in a reducing atmosphere for 2-6 hours and then passivated for 2 hours. In step (4), the porous carrier is either an activated alumina carrier or a foam metal, and the atomization pressure is 5~15 MPa.

[0013] This invention provides a MOFs-derived layered porous titanium dioxide-based monolithic photocatalyst, characterized in that it is prepared according to any of the methods described above.

[0014] This invention provides an application of a MOF-derived layered porous titanium dioxide-based monolithic photocatalyst in the mineralization treatment of leveling liquid wastewater.

[0015] The catalytic degradation experiment of MOF-derived monolithic photocatalyst TiO2 / NC was carried out in a beaker. A certain amount of monolithic photocatalyst was added to 100 mL of leveling liquid wastewater (COD=110 mg / L). After adsorption equilibrium was reached, the xenon lamp was turned on to carry out the photocatalytic degradation reaction. After 120 min of illumination, a sample was taken, filtered, and the mineralization rate of the leveling liquid wastewater was determined.

[0016] The present invention has the following advantages: (1) This invention utilizes the framework structure characteristics of MOFs. Calcination in a reducing atmosphere preserves the polyhedral framework structure, and the porous structure with a large specific surface area is beneficial for mass transfer and diffusion. On one hand, the preparation method of this invention can promote the formation of a porous layered structure, obtaining more electron-hole pairs and promoting the catalytic reaction. On the other hand, the layered porous structure can effectively alleviate the agglomeration of particulate matter during the catalytic process and improve the structural stability of TiO2 / NC.

[0017] (2) The MOFs-derived layered porous TiO2-based catalyst proposed in this invention can enhance its specific photocatalytic performance through the strong metal-support interaction between the NC framework and the metal catalyst, and the content of active components can be controlled by the calcination temperature to improve the surface catalytic reaction rate.

[0018] (3) The TiO2-based monolithic catalyst proposed in this invention adopts a porous support and high-pressure airless spraying process, which not only promotes the uniform distribution of active components, but also solves the problem of catalyst recovery, and has potential application prospects in the field of environmental governance. Detailed Implementation

[0019] The present invention will be further illustrated by the examples.

[0020] Example 1: A MOF-derived layered porous titanium dioxide-based monolithic photocatalyst is prepared by using a reduction-passivation process to achieve non-metallic C and N doping, promoting electron trapping and suppressing the recombination of photogenerated electrons and holes. Furthermore, the monolithic catalyst construction addresses the practical problem of recovering powdered catalysts. The preparation process includes the following steps: (1) Under magnetic stirring, Ti-source tetrabutyl titanate was dissolved in N,N-dimethylformamide (DMF) to obtain a tetrabutyl titanate solution; terephthalic acid was weighed and dissolved in DMF according to the molar ratio of Ti source to amino terephthalic acid ligand 1:4 to obtain a ligand solvent; then the tetrabutyl titanate solution was added dropwise to the ligand solvent, and the resulting mixed solution was transferred to a polytetrafluoroethylene reaction vessel after the addition was complete; (2) Adjust the reaction temperature to 150℃ and the ultrasonic frequency to 300Hz, and carry out ultrasonic-hydrothermal synergistic reaction of the mixed solution in step (1) for 20 h; after the reaction is completed and cooled to room temperature, centrifuge to collect the precipitate, and wash and dry it to obtain MIL-125(Ti); (3) The MIL-125(Ti) obtained in (2) was placed in a tube furnace for in-situ reduction-passivation treatment, that is, the reduction atmosphere was adjusted to 5%~10% H2 / Ar2, calcined at 500℃ for 2h, and passivated at 25℃ for 2h to obtain the active product. (4) Disperse the active product obtained in (3) into anhydrous ethanol and stir continuously; use high pressure airless spraying immobilization technology to fix the active component onto the porous support, control the atomization pressure to 10 MPa, and place it in a muffle furnace for calcination treatment to obtain MOFs-derived layered porous TiO2-based monolithic photocatalyst TiO2 / NC.

[0021] The prepared catalyst achieved a mineralization rate of 45.8% for the leveling liquid wastewater.

[0022] Example 2: A MOF-derived layered porous titanium dioxide-based monolithic photocatalyst, prepared according to steps similar to those in Example 1, is as follows: (1) Under magnetic stirring, Ti-source tetrabutyl titanate was dissolved in N,N-dimethylformamide (DMF) to obtain a tetrabutyl titanate solution; terephthalic acid was weighed and dissolved in DMF according to the molar ratio of Ti source to amino terephthalic acid ligand 1:8 to obtain a ligand solvent; then the tetrabutyl titanate solution was added dropwise to the ligand solvent, and after the addition was complete, the resulting mixed solution was transferred to a polytetrafluoroethylene reaction vessel; (2) Adjust the reaction temperature to 180℃ and the ultrasonic frequency to 600Hz, and carry out ultrasonic-hydrothermal synergistic reaction of the mixed solution in step (1) for 20 h; after the reaction is completed and cooled to room temperature, centrifuge to collect the precipitate, and wash and dry to obtain the product MIL-125(Ti); (3) Place the MIL-125(Ti) in (2) in a tube furnace for in-situ reduction-passivation treatment, that is, adjust the reduction atmosphere to 5%~10% H2 / Ar2, calcine at 600 ℃ for 4h, and passivate at 100 ℃ for 2h to obtain the active product; (4) Disperse the active product of (3) into anhydrous ethanol and stir continuously; use high pressure airless spraying immobilization technology to fix the active component onto the porous carrier, control the atomization pressure to 10MPa, and place it in a muffle furnace for calcination treatment to obtain MOFs-derived layered porous TiO2-based monolithic photocatalyst TiO2 / NC.

[0023] The prepared catalyst achieved a mineralization rate of 41.6% for the leveling liquid wastewater.

[0024] Example 3: A MOF-derived layered porous titanium dioxide-based monolithic photocatalyst, prepared according to steps similar to those in Example 1, is as follows: (1) Under magnetic stirring, Ti-source tetrabutyl titanate was dissolved in N,N-dimethylformamide (DMF) to obtain a tetrabutyl titanate solution; terephthalic acid was weighed and dissolved in DMF according to the molar ratio of Ti source to amino terephthalic acid ligand 1:4 to obtain a ligand solvent; then the tetrabutyl titanate solution was added dropwise to the ligand solvent, and the resulting mixed solution was transferred to a polytetrafluoroethylene reaction vessel after the addition was complete; (2) Adjust the reaction temperature to 150℃ and the ultrasonic frequency to 600Hz, and carry out ultrasonic-hydrothermal synergistic reaction of the mixed solution in step (1) for 20 h; after the reaction is completed and cooled to room temperature, centrifuge to collect the precipitate, and wash and dry to obtain the product MIL-125(Ti); (3) Place the MIL-125(Ti) in (2) in a tube furnace for in-situ reduction-passivation treatment, that is, adjust the reduction atmosphere to 5%~10% H2 / Ar2, calcine at 700 ℃ for 2h, and passivate at 300 ℃ for 4h to obtain the active product; (4) Disperse the active product of (3) into anhydrous ethanol and stir continuously; use high pressure airless spraying immobilization technology to fix the active component onto the porous carrier, control the atomization pressure to 5MPa, and place it in a muffle furnace for calcination treatment to obtain MOFs-derived layered porous TiO2-based monolithic photocatalyst TiO2 / NC.

[0025] The prepared catalyst achieved a mineralization rate of 32.9% for the leveling liquid wastewater.

[0026] Example 4: A MOF-derived layered porous titanium dioxide-based monolithic photocatalyst, prepared according to steps similar to those in Example 1, is as follows: (1) Under magnetic stirring, Ti-source tetrabutyl titanate was dissolved in N,N-dimethylformamide (DMF) to obtain a tetrabutyl titanate solution; terephthalic acid was weighed and dissolved in DMF according to the molar ratio of Ti source to amino terephthalic acid ligand 1:6 to obtain a ligand solvent; then the tetrabutyl titanate solution was added dropwise to the ligand solvent, and the resulting mixed solution was transferred to a polytetrafluoroethylene reaction vessel after the addition was complete; (2) Adjust the reaction temperature to 180℃ and the ultrasonic frequency to 300Hz, and carry out ultrasonic-hydrothermal synergistic reaction of the mixed solution in step (1) for 20 h; after the reaction is completed and cooled to room temperature, centrifuge to collect the precipitate, and wash and dry to obtain the product MIL-125(Ti); (3) Place the MIL-125(Ti) in (2) in a tube furnace for in-situ reduction-passivation treatment, that is, adjust the reduction atmosphere to 5%~10% H2 / Ar2, calcine at 600 ℃ for 2h, and passivate at 60 ℃ for 2h to obtain the active product; (4) Disperse the active product of (3) into anhydrous ethanol and stir continuously; use high pressure airless spraying immobilization technology to fix the active component onto the porous carrier, control the atomization pressure to 10MPa, and place it in a muffle furnace for calcination treatment to obtain MOFs-derived layered porous TiO2-based monolithic photocatalyst TiO2 / NC.

[0027] The prepared catalyst achieved a mineralization rate of 53.2% for leveling liquid wastewater.

Claims

1. A method for preparing a MOFs-derived hierarchical porous titanium dioxide-based monolithic photocatalyst, characterized in that: The reduction-passivation process is used to achieve doping of non-metallic C and N, promote electron trapping, inhibit the recombination of photogenerated electrons and holes, and solve the practical problem of powder catalyst recovery based on the construction of a monolithic catalyst, including the following steps: (1) Under magnetic stirring, tetrabutyl titanate, a Ti source, is dissolved in N,N-dimethylformamide (DMF) to obtain a tetrabutyl titanate solution; terephthalic acid is weighed and dissolved in DMF according to a molar ratio of the Ti source to the aminoterephthalic acid ligand of 1:(4-8) to obtain a ligand solvent; then the tetrabutyl titanate solution is added dropwise to the ligand solvent, and after the addition is complete, the obtained mixed solution is transferred to a polytetrafluoroethylene reaction container; (2) adjusting the reaction temperature and ultrasonic frequency, and subjecting the mixed solution in step (1) to an ultrasonic-hydrothermal synergistic reaction for 12 to 20 hours; after the reaction is completed and the temperature is cooled to room temperature, the precipitate is collected by centrifugation, and then washed and dried to obtain the product MIL-125(Ti); (3) placing the MIL-125(Ti) in (2) in a tube furnace for in-situ reduction-passivation treatment, i.e., adjusting the reducing atmosphere to 5%-10% H2 / Ar2, calcining at 500-700°C, and then passivating at 25-300°C to obtain an active product; (4) Dispersing the active product of (3) in anhydrous ethanol and stirring continuously; using high-pressure airless spraying solidification technology to fix the active components onto the porous carrier, controlling the atomization pressure, and placing it in a muffle furnace for calcination to obtain a MOFs-derived hierarchical porous TiO2-based integral photocatalyst TiO2 / NC.

2. The method for preparing the MOFs-derived hierarchical porous titanium dioxide-based monolithic photocatalyst according to claim 1, characterized in that: In step (2), the reaction temperature is 150-180° C. and the ultrasonic frequency is 300-600 Hz.

3. The method for preparing the MOFs-derived hierarchical porous titanium dioxide-based monolithic photocatalyst according to claim 1, characterized in that: In step (3), the reducing atmosphere is calcined for 2 to 6 hours and passivated for 2 hours.

4. The method for preparing the MOFs-derived hierarchical porous titanium dioxide-based monolithic photocatalyst according to claim 1, characterized in that: In step (4), the porous carrier is any one of an activated alumina carrier or a foamed metal, and the atomization pressure is 5-15 MPa.

5. The method for preparing the MOFs-derived hierarchical porous titanium dioxide-based monolithic photocatalyst according to any one of claims 1 to 4, characterized in that: Prepare as follows: (1) Under magnetic stirring, tetrabutyl titanate, a Ti source, is dissolved in N,N-dimethylformamide (DMF) to obtain a tetrabutyl titanate solution; terephthalic acid is weighed and dissolved in DMF according to a molar ratio of the Ti source to the aminoterephthalic acid ligand of 1:4 to obtain a ligand solvent; then the tetrabutyl titanate solution is dripped into the ligand solvent, and after the dripping is complete, the obtained mixed solution is transferred to a polytetrafluoroethylene reaction container; (2) adjusting the reaction temperature to 150°C and the ultrasonic frequency to 300 Hz, and subjecting the mixed solution in step (1) to an ultrasonic-hydrothermal synergistic reaction for 20 h; after the reaction is completed and the mixture cools to room temperature, centrifuging and collecting the precipitate, washing and drying the precipitate to obtain MIL-125(Ti); (3) placing the MIL-125(Ti) obtained in (2) in a tube furnace for in-situ reduction-passivation treatment, i.e., adjusting the reducing atmosphere to 5%-10% H2 / Ar2, calcining at 500°C for 2h, and passivating at 25°C for 2h to obtain an active product; (4) Dispersing the active product obtained in (3) into anhydrous ethanol and stirring continuously; fixing the active components onto the porous carrier by high-pressure airless spraying solidification technology, controlling the atomization pressure to 10 MPa, and placing it in a muffle furnace for calcination to obtain a MOFs-derived hierarchical porous TiO2-based integral photocatalyst TiO2 / NC.

6. The method for preparing the MOFs-derived hierarchical porous titanium dioxide-based monolithic photocatalyst according to any one of claims 1 to 4, characterized in that: Prepare as follows: (1) Under magnetic stirring, tetrabutyl titanate, a Ti source, is dissolved in N,N-dimethylformamide (DMF) to obtain a tetrabutyl titanate solution; terephthalic acid is weighed and dissolved in DMF according to a molar ratio of the Ti source to the aminoterephthalic acid ligand of 1:8 to obtain a ligand solvent; then the tetrabutyl titanate solution is dripped into the ligand solvent, and after the dripping is complete, the obtained mixed solution is transferred to a polytetrafluoroethylene reaction container; (2) adjusting the reaction temperature to 180°C and the ultrasonic frequency to 600 Hz, and subjecting the mixed solution in step (1) to an ultrasonic-hydrothermal synergistic reaction for 20 h; after the reaction is completed and the mixture cools to room temperature, centrifuging and collecting the precipitate, washing and drying the precipitate to obtain the product MIL-125(Ti); (3) The MIL-125(Ti) prepared in (2) was placed in a tube furnace for in-situ reduction-passivation treatment, i.e., the reducing atmosphere was adjusted to 5%-10% H2 / Ar2, calcined at 600°C for 4h, and passivated at 100°C for 2h to obtain an active product; (4) Disperse the active product of (3) in anhydrous ethanol and stir continuously; fix the active components onto the porous carrier using high-pressure airless spraying solidification technology, control the atomization pressure to 10 MPa, and place it in a muffle furnace for calcination to obtain a MOFs-derived hierarchical porous TiO2-based integral photocatalyst TiO2 / NC.

7. The method for preparing the MOFs-derived hierarchical porous titanium dioxide-based monolithic photocatalyst according to any one of claims 1 to 4, characterized in that: Prepare as follows: (1) Under magnetic stirring, tetrabutyl titanate, a Ti source, is dissolved in N,N-dimethylformamide (DMF) to obtain a tetrabutyl titanate solution; terephthalic acid is weighed and dissolved in DMF according to a molar ratio of the Ti source to the aminoterephthalic acid ligand of 1:4 to obtain a ligand solvent; then the tetrabutyl titanate solution is dripped into the ligand solvent, and after the dripping is complete, the obtained mixed solution is transferred to a polytetrafluoroethylene reaction container; (2) adjusting the reaction temperature to 150°C and the ultrasonic frequency to 600 Hz, and subjecting the mixed solution in step (1) to an ultrasonic-hydrothermal synergistic reaction for 20 h; after the reaction is completed and the mixture cools to room temperature, centrifuging and collecting the precipitate, washing and drying the precipitate to obtain the product MIL-125(Ti); (3) The MIL-125(Ti) prepared in (2) was placed in a tube furnace for in-situ reduction-passivation treatment, i.e., the reducing atmosphere was adjusted to 5%-10% H2 / Ar2, calcined at 700°C for 2h, and passivated at 300°C for 4h to obtain an active product; (4) Disperse the active product of (3) in anhydrous ethanol and stir continuously; fix the active components onto the porous carrier using high-pressure airless spraying solidification technology, control the atomization pressure to 5 MPa, and place it in a muffle furnace for calcination to obtain a MOFs-derived hierarchical porous TiO2-based integral photocatalyst TiO2 / NC.

8. The method for preparing the MOFs-derived hierarchical porous titanium dioxide-based monolithic photocatalyst according to any one of claims 1 to 4, characterized in that: Prepare as follows: (1) Under magnetic stirring, tetrabutyl titanate as a Ti source is dissolved in N,N-dimethylformamide (DMF) to obtain a tetrabutyl titanate solution; terephthalic acid is weighed and dissolved in DMF according to a molar ratio of the Ti source to the aminoterephthalic acid ligand of 1:6 to obtain a ligand solvent; then the tetrabutyl titanate solution is added dropwise to the ligand solvent, and after the addition is complete, the obtained mixed solution is transferred to a polytetrafluoroethylene reaction container; (2) adjusting the reaction temperature to 180°C and the ultrasonic frequency to 300 Hz, and subjecting the mixed solution in step (1) to an ultrasonic-hydrothermal synergistic reaction for 20 h; after the reaction is completed and the mixture cools to room temperature, centrifuging and collecting the precipitate, washing and drying the precipitate to obtain the product MIL-125(Ti); (3) The MIL-125(Ti) prepared in (2) was placed in a tube furnace for in-situ reduction-passivation treatment, i.e., the reducing atmosphere was adjusted to 5%-10% H2 / Ar2, calcined at 600°C for 2h, and passivated at 60°C for 2h to obtain an active product; (4) Disperse the active product of (3) in anhydrous ethanol and stir continuously; fix the active components onto the porous carrier using high-pressure airless spraying solidification technology, control the atomization pressure to 10 MPa, and place it in a muffle furnace for calcination to obtain a MOFs-derived hierarchical porous TiO2-based integral photocatalyst TiO2 / NC.

9. A MOFs-derived hierarchical porous titanium dioxide-based monolithic photocatalyst, characterized in that Prepared according to any one of claims 1 to 8.

10. Use of the MOFs-derived hierarchical porous titanium dioxide-based monolithic photocatalyst according to claim 9 in the mineralization treatment of leveling liquid wastewater.