CN101632943B - Porous material externally loaded TiO2-X/Csurf. composite and preparation process - Google Patents

Abstract

The present invention relates to a porous material externally loaded TiO2-X/Csurf. composite and a preparation process. The supercritical fluid precipitation technology and the sol-gel method are adopted to prepare the composite nanomaterial TiO2-X/Csurf. (X: transition metal; Csurf.: carbon surface) with an external load structure. The preparation process is characterized in that the composite externally loaded TiO2-X/Csurf. prepared by the supercritical pretreatment and the sol-gel method has novel structure and good chemical and physical properties. The preparation process provides a new method for the applied research of porous material externally loaded and doped TiO2 type photocatalytic material. Meanwhile, the process is simple and is applicable to industrialized production and makes a positive contribution to developing the studying theory, technology and method system of the material externally loaded nanomaterial.

Description

TiO₂-X/C_surf. composite loaded on porous material and its preparation process

technical field

The invention relates to a TiO ₂ -X/C _surf. composite loaded on a porous material and a preparation process thereof, belonging to the field of functional materials.

Background technique

TiO ₂ has been proved to be the most widely used photocatalyst because of its biological and chemical inertness, no photocorrosion and chemical corrosion, and low price. Since the electronic distribution of _TiO2 is characterized by the existence of a band gap between its conduction band and valence band. When illuminated, as long as the energy of the photon is equal to or exceeds the band gap energy of the semiconductor (hv≥E _g ), electrons can transition from the valence band to the conduction band, thereby generating conduction band electrons and valence band holes. Under the action of the electric field of the space charge layer, the free electrons in the conduction band quickly migrate to the surface of the semiconductor particles and transfer to the oxidized components in the solution, so that the photogenerated electrons and holes undergo a series of reactions to form hydroxyl radicals OH, which can oxidize Almost all organic matter. Therefore, it has a strong application prospect in the field of environmental protection (such as waste water and waste gas treatment). The reaction process is as follows:

TiO ₂ +hv→h ⁺ +e ^-

H ₂ O+h ⁺ →·OH+H ⁺

e ⁻ +O ₂ →O ₂ ⁻ ·

H ⁺ +O ₂ ⁻ →HO ₂ ·

2HO ₂ →H ₂ O ₂ +O ₂

H ₂ O ₂ +O ₂ ^- → OH+OH ^- +O ₂

h ⁺ +OH ^- → OH

h ⁺ +org → intermediate → CO ₂ +H ₂ O

·OH+org→intermediate→CO ₂ +H ₂ O

However, due to the wide band gap of TiO ₂ (about 3.2eV), the threshold wavelength of its absorption is less than 400nm, and the utilization rate of sunlight is not high; it affects the practical and industrialization process of TiO ₂ heterogeneous photocatalytic reaction. It is found that the photocatalytic activity and visible light utilization rate of _TiO2 can be improved by transition metal doping or semiconductor oxide recombination. Therefore, nano-TiO ₂ -X (X: transition metal) doped photocatalytic materials have become one of the research hotspots in the field of photocatalysis. However, the prepared TiO ₂ -X nanopowders and nanofibers are easy to agglomerate and difficult to settle in aqueous solution due to their fine particles, and the catalyst is difficult to separate and recover, resulting in a large loss of active components of the catalyst, which is not conducive to the regeneration and reuse of the catalyst; Due to its relatively small specific surface area, the photocatalytic activity and photocatalytic efficiency are not high, which also affects and limits its practical application. For this reason, in recent years, the preparation and photocatalytic performance of doped titanium oxide photocatalysts with supported structures have received great attention. Porous carbon has become an ideal carrier material in the study of titanium oxide loading due to its stable chemical properties, low price, and moderate adsorption force. But so far, a lot of work has mainly focused on the preparation of titanium oxide deposited on porous materials. We know that _TiO2 has photocatalytic activity only after it is activated by light, and the penetration ability of ultraviolet light is weak. Therefore, TiO ₂ in the pores of carbon does not have photocatalytic activity; in addition, TiO ₂ is deposited in the pores, which reduces the specific surface area of the carrier and weakens the effect of using loading to increase the specific surface area to enhance the catalytic activity, affecting and Restricted its industrial production and practical application. However, it is worth noting that so far there is no effective method for preparing porous materials (charcoal) to support TiO ₂ -X composite nano-photocatalytic materials.

Contents of the invention

The technical problem to be solved by the present invention is: to solve the problems of the above-mentioned prior art, and to provide a porous antimicrobial property, non-toxicity, large specific surface area, high strength, good processing technology, simple preparation process, and easy industrial production. TiO ₂ -X/C _surf. composite loaded on the outside of the material and its preparation process.

The technical scheme adopted in the present invention is: through the supersolubility, strong diffusibility and unique mass transfer property of the fluid, the solute is dissolved to form a supersaturated solution, and the critical condition is resolved to cause its crystallization and _{precipitation} ; As a solvent, the porous material is used as a template to infiltrate the low-molecular-weight organic solution into the pores, and then through coagulation and precipitation, the pores of the porous material are blocked to prepare a porous material—a low-molecular-weight blocking carrier; and then use this as a double template, The TiO ₂ -X sol was prepared by the sol-gel method and loaded on the surface of the plugging carrier, and then the TiO ₂ -X/Csurf complex loaded on the porous material was synthesized by low temperature heat treatment and high temperature calcination.

In the above technical scheme, the specific preparation process is:

(1) Through the supercritical fluid precipitation process, the low-molecular organic solution penetrates into the pores of the porous material, and the critical state is released to make it precipitate, and the porous material-low-molecular plugging carrier is prepared;

(2) Using butyl titanate as a starting material, using absolute ethanol as a solvent, and diethanolamine as a chelating agent, under the interaction of distilled water and concentrated hydrochloric acid, synthesize TiO ₂ -X colloid;

(3) Coating the precursor sol of TiO ₂ or TiO ₂ -X on the porous material-low molecular plugging carrier through the sol-gel process to prepare the TiO ₂ -X precursor/C _{surf.composite} material;

(4) TiO ₂ -X precursor/C _surf. composite materials were calcined at high temperature to obtain TiO ₂ /C _surf. , TiO ₂ -Fe/C _surf. , TiO ₂ -Ag/C _surf. , TiO ₂ -Mn/ C _surf. , TiO ₂ -Cu/C _surf. , TiO ₂ -Cr/C _surf. and other TiO ₂ -X/Csurf. composite nanomaterials;

In the above formula, X is a transition metal, and Csurf is a carbon surface.

In the above technical scheme, the weight percentages of reagents used are: butyl titanate, purity>99.0, 50-65%; diethanolamine, purity>99.9, 1-5%; absolute ethanol, purity>99.9, 25-35%; Polyethylene glycol, purity >99.9, 2-8%.

In the above technical solution, the porous material is activated carbon, aluminum oxide, silicon oxide, and zeolite.

In the above technical scheme, the low-molecular compound is isobutanol, stearic acid, paraffin, cyclohexane.

In the above technical solution, under supercritical conditions, the heating rate is 2-4°C, the temperature is 34.1-300°C, and the pressure is 7.1-50MPa.

In the above technical scheme, to remove the critical condition, the heating is first stopped, and the supercritical tank is allowed to cool until the temperature reaches a temperature below the freezing point of the low-molecular compound.

In the above technical solution, the inorganic precursors of X are iron nitrate, silver nitrate, cerium nitrate, copper nitrate, zirconium nitrate, zinc nitrate, manganese nitrate and the like.

In the above technical scheme, the precursor sol of TiO ₂ or TiO ₂ -X is coated on the porous material-low molecular plugging carrier: put the porous material-low molecular plugging carrier into the TiO ₂ or TiO ₂ -X sol , and then through ultrasonic vibration, the sol is coated on the surface of the blocking carrier, the number of times of coating is 1-8 times, and the ultrasonic time is 10-300min.

In the above technical solution, before calcination, the TiO ₂ -X precursor/C _surf. is heat-treated at a temperature of 100-300° C. for 1-3 hours, and a heating rate of 0.5-3° C./min.

In the above technical solution, the calcination temperature is 300-1000° C., the time is 1-3 hours, and the heating rate is 0.5-3° C./min.

In the above technical solution, the template is composed of a substance with the same composition, and the double template is composed of two substances with different compositions combined through physical methods.

Technical principle:

Supercritical fluid has a two-phase (gas phase, liquid phase) property. Therefore, the solute with high solubility is evenly distributed in the liquid phase and the gas phase, and the gas phase has strong fluidity, which makes the solute distribution more uniform. Under certain conditions, the supercritical fluid makes the solution reach a very high degree of supersaturation and supersaturation rate, so that particles with a smaller particle size than those obtained by conventional methods can be quickly precipitated. In addition, by adjusting operating parameters, the technology can be more efficient. Accurately control the crystallization process, control the particle size distribution of the product, and form a small average particle size and a particle size distribution.

Features of supercritical fluid precipitation technology: With the successful application of ultrafine particles, especially nanoparticles, in the high-tech field, the preparation of ultrafine particles has become a hot spot of concern. Several conventional techniques have been developed in the past for the preparation of ultrafine particles. These methods restrict their application due to their respective shortcomings. Such as spray drying, the main disadvantage of ultrafine milling is that the size distribution of the formed particles is wide (0.5-25um) and only a small part of the particles belong to the nanometer range. _CO2 supercritical temperature: 34.1, pressure: 7.1MPa

Sol-gel process: the metal alkoxide solution is decomposed with water at normal temperature or near normal temperature, and the polycondensation reaction occurs at the same time to form a sol, which is further reacted to form a gel and then solidified, and then undergoes low-temperature heat treatment to obtain an inorganic material.

advantage:

①The operating temperature is much lower than the glass melting temperature, which saves energy and makes the material preparation process easy to control;

②The components of the prepared material are highly uniform, with a wide range of composition and can be greatly changed;

③Simple process, easy industrialization, low cost, flexible application;

④ It can improve production efficiency;

⑤ Can guarantee the purity of the final product;

⑥ The prepared airgel is a new type of lightweight nanoporous amorphous solid material with controllable structure, which has many special properties, so it has broad application prospects.

Therefore, the external loading of TiO ₂ on the surface of porous materials is the most effective method to solve the problem of photocatalytic technology applied to sewage degradation treatment. Utilizing the nano-microporous properties, high specific surface area properties, and synergistic catalytic properties of TiO ₂ -X/C _surf. Domain effect, external loading structure, and obtain a new type of photocatalytic TiO ₂ -X/C _surf. composite material with high activity, easy separation and reuse. At the same time, the process is simple and easy for industrial production.

The invention adopts a supercritical pretreatment technology and a sol-gel method, and synthesizes a TiO ₂ -X complex supported on a porous material through heat treatment and high-temperature roasting. At present, we use this process to prepare TiO ₂ /C _surf. , TiO ₂ -Fe/C _surf. , TiO ₂ -Ag/C _surf. , TiO ₂ -Mn/C _surf. , TiO ₂ -Cu/C _{surf .} , TiO ₂ -Cr/C _surf. and other composite nanomaterials. Loading TiO ₂ -X composites on the porous material has the following significant advantages and effects: (a) has high antibacterial properties without any toxicity; (b) has a large specific surface area, and the pore structure can be adjusted and can be quantitatively designed; (c) High strength, strong adhesion, good processing technology; (d) low baking temperature, simple preparation process, low production cost, easy industrial production; (e) wide application, it is the most suitable solution for the application of photocatalytic technology in sewage degradation treatment The effective method saves the cost of sewage degradation treatment.

Physical and chemical properties of TiO ₂ -X/C _surf. complex

After the TiO ₂ -X composite loaded on the porous material is heat-treated at 500°C, its crystal structure is anatase, and the grain size is between 20-60nm. Under the low-power electron microscope, the surface morphology of the TiO ₂ -X/C _surf. complex is relatively uniform, with holes; under the high-power electron microscope, the TiO ₂ -X/C _surf. has few surface defects and only contains a small amount of impurities; At the same time, there is an obvious ultraviolet absorption corner near 380nm. The optical absorption band edge of TiO ₂ fiber is about 380nm, and there is a strong absorption band in the ultraviolet region between 200nm and 380nm. Compared with TiO ₂ raw material powder, the optical absorption band edge of TiO ₂ nanofiber has no obvious change.

TiO ₂ -X/C _surf. complex has certain strength and high specific surface area. After heat treatment at 500℃, the organic matter is almost completely decomposed, and the OH bond content is relatively high, which is mainly due to the moisture absorbed on the surface of the external load composite.

Description of drawings

Fig. 1 is a schematic diagram of the preparation process of the present invention

Figure 2 is the scanning electron microscope photo of TiO ₂ /C _surf. complex

Figure 3 is the X-ray diffraction pattern of the TiO ₂ /C _{surf.composite} treated at different temperatures

Figure 4 is the infrared spectrum of TiO ₂ /C _surf. complex

Detailed ways:

1) The preparation method of TiO ₂ sol is as follows: using butyl titanate as the starting material, using absolute ethanol as the solvent and diethanolamine as the chelating agent, under the interaction of distilled water and concentrated hydrochloric acid, synthesize TiO by hydrolysis and polycondensation reaction ₂ Sol. Diethanolamine chelating agent, butyl titanate and diluent absolute ethanol are first added into the three-necked flask together, while distilled water, hydrochloric acid and absolute ethanol are added through the funnel at the same time, and the dropping rate of the two is generally controlled at 0.7-1.0ml·min ^- between ¹ .

2) According to the above formula, the inorganic precursor of X is also added into the three-neck flask, and the TiO ₂ -X sol is prepared by the sol-gel method;

3) Put the porous material into a two-layer frame with holes, and then put it into a supercritical kettle, which contains low molecular weight organic matter such as isobutanol, stearic acid, paraffin, cyclohexane, etc., and the heating rate is 2- 4°C, rise to the appropriate temperature range (34.1-300°C) and reach the appropriate pressure range (7.1-50MPa), keep for 2-4h, so that the low molecular weight organic matter is completely deposited in the pores of the porous material;

4) After the low-molecular-weight organic matter is completely deposited in the pores of the porous material, stop heating, let the supercritical reactor cool down, and reach a temperature below the freezing point of the low-molecular-weight compound. If the room temperature is relatively high, an ice bath can be used for cooling. Then take out the porous material-low molecular blocking carrier;

5) Put the porous material-low molecular plugging carrier into the titanium sol body, and then apply the sol body on the surface of the plugging carrier through ultrasonic vibration, the number of coating times is 1-8 times, and the ultrasonic time is 10-300min.

6) Before calcination, TiO ₂ -X precursor/C _surf. is subjected to heat treatment at a temperature of 100-300°C for 1-3 hours and a heating rate of 0.5-3°C/min;

7) Calcining the TiO ₂ -X complex supported on the porous material at a high temperature at a temperature of 300-1000°C for 1-3 hours and a heating rate of 0.5-3°C/min;

8) Test and analyze the specific surface area, pore size, crystal form, surface morphology, chemical form of elements, etc. of the TiO ₂ -X composite loaded on the porous material;

The prepared porous material supports the TiO ₂ -X complex on the outside, and after heat treatment at 500° C. for 1-2 hours in the air, it becomes pure anatase crystal form.

Example 1: First, put 15g of coconut shell activated carbon into the shelf in the supercritical kettle. There is 20ml of isobutanol in the autoclave, and the temperature is raised to 300℃ according to the heating rate of 2℃/min. After the pressure is 7.1MPa, keep it for 2h; then Cool the supercritical kettle to room temperature to obtain a porous material-low molecular plugging carrier. In addition, using the sol-gel method, mix 60g of butyl titanate with a purity of 99.0%, 3g of diethanolamine and 10g of absolute ethanol, add them into a three-necked flask, and use a GS122 electronic constant speed stirrer to stir evenly. Mix 20 g of absolute ethanol with 4 g of distilled water, and then slowly drop them into the three-necked flask through a separatory funnel. Butyl titanate forms TiO ₂ sol through hydrolysis and condensation reactions. Secondly, put the obtained porous material-low molecular plugging carrier into the TiO ₂ sol body, and coat it on the surface of the plugging carrier during the ultrasonic vibration process. The coating times are 1 time, and the ultrasonic time is 10 minutes. Finally, the TiO ₂ precursor/C _surf. was heat-treated at a temperature of 100°C for 3 hours at a heating rate of 0.5°C/min; then roasted under nitrogen protection at a temperature of 300°C for 3 hours. Its crystal form is anatase, the size of the nanoparticles is 30-50nm, the specific surface area is 884m ² /g, and the TiO ₂ nanoparticles are loaded on the surface of the porous material.

Example 2: First, put 15g of coconut shell activated carbon into the shelf in the supercritical kettle. There is 20ml of isobutanol in the autoclave, and the temperature is raised to 300℃ according to the heating rate of 4℃/min. After the pressure is 12MPa, keep it for 2h; then put The supercritical kettle is cooled to room temperature to obtain a porous material-low molecular plugging carrier. Using the sol-gel method, mix 60g of butyl titanate with a purity of 99.0%, 3g of diethanolamine, 10g of absolute ethanol and 2g of ferric nitrate, add them into a three-necked bottle, and stir well with a GS122 electronic constant speed stirrer . Mix 20 g of absolute ethanol with 4 g of distilled water, and then slowly drop them into the three-necked flask through a separatory funnel. Butyl titanate forms TiO ₂ -Fe sol through hydrolysis and condensation reactions. Secondly, the obtained porous material-low molecular plugging carrier is put into the TiO ₂ -Fe sol body, and it is coated on the plugging surface during ultrasonic vibration. On the surface of the carrier, the number of times of coating is 3 times, and the ultrasonic time is 10 minutes. Finally, the TiO ₂ -X precursor/C _surf. is heat-treated at a temperature of 300°C for 1 hour at a heating rate of 3°C/min; then roasted under nitrogen protection at a temperature of 1000°C for 1 hour. Its crystal form is anatase, the size of the nanoparticles is 30-50nm, the specific surface area reaches 568m ² /g, and the TiO ₂ -Fe nanoparticles are loaded on the surface of the porous material.

Example 3: First, put 15g of coconut shell activated carbon into the shelf in the supercritical kettle. There is 20ml of isobutanol in the autoclave, and the temperature is raised to 180℃ according to the heating rate of 2℃/min. After the pressure is 15MPa, it is kept for 2h; then the The supercritical kettle is cooled to room temperature to obtain a porous material-low molecular plugging carrier. Using the sol-gel method, mix 60g of butyl titanate with a purity of 99.0%, 3g of diethanolamine and 10g of absolute ethanol, add it into a three-necked flask, and stir evenly with a GS122 electronic constant speed stirrer. Take 20g of absolute ethanol, mix with 10g of distilled water and 2g of copper nitrate, and then slowly drop them into the three-neck flask through the separatory funnel. Butyl titanate forms TiO ₂ -Cu sol through hydrolysis and condensation reactions. Secondly, put the obtained "porous material-low molecular" plugging carrier into the TiO ₂ -Cu sol, and coat it on the The surface of the carrier is blocked, the number of coatings is 1, and the ultrasonic time is 10 minutes. Finally, the TiO ₂ -X precursor/C _surf. was heat-treated at a temperature of 150°C for 1 hour at a heating rate of 1°C/min; then roasted under nitrogen protection at a temperature of 500°C for 2 hours. Its crystal form is anatase, the size of the nanoparticles is 30-50nm, the specific surface area reaches 1128m ² /g, and the TiO ₂ -Cu nanoparticles are loaded on the surface of the porous material.

Example 4: First, put 15g of coconut shell activated carbon into the shelf in the supercritical kettle. There is 20ml of isobutanol in the autoclave, and the temperature is raised to 34.1℃ according to the heating rate of 2℃/min. After the pressure is 50MPa, keep it for 2h; then put The supercritical kettle is cooled to room temperature to obtain a porous material-low molecular plugging carrier. Using the sol-gel method, mix 60g of butyl titanate with a purity of 99.0%, 3g of diethanolamine and 10g of absolute ethanol, add it into a three-necked flask, and stir evenly with a GS122 electronic constant speed stirrer. Take 20g of absolute ethanol, mix it with 10g of distilled water and zinc nitrate, and then slowly drop it into the three-necked flask through a separatory funnel. Butyl titanate forms TiO ₂ -Zn sol through hydrolysis and condensation reactions. Secondly, the obtained porous material-low molecular plugging carrier is placed in the TiO ₂ -Zn sol body, and it is coated on the plugging surface during ultrasonic vibration. On the surface of the carrier, the number of coating times is 1, and the ultrasonic time is 10 minutes. Finally, the TiO ₂ -X precursor/C _surf. was heat-treated at a temperature of 150°C for 2 hours at a heating rate of 1°C/min; then roasted under nitrogen protection at a temperature of 800°C for 2 hours. Its crystal form is anatase, the size of the nanoparticles is 30-50nm, the specific surface area reaches 938m ² /g, and the TiO ₂ -Zn nanoparticles are loaded on the surface of the porous material.

Example 5: First, put 15g of coconut shell activated carbon into the shelf in the supercritical kettle. There is 20ml of isobutanol in the autoclave, and the temperature is raised to 34.1℃ according to the heating rate of 3℃/min. After the pressure is 8MPa, keep it for 2h; then put The supercritical kettle is cooled to room temperature to obtain a porous material-low molecular plugging carrier. Using the sol-gel method, mix 60g of butyl titanate with a purity of 99.0%, 3g of diethanolamine and 10g of absolute ethanol, add it into a three-necked flask, and stir evenly with a GS122 electronic constant speed stirrer. Take 20g of absolute ethanol, mix with 10g of distilled water and chromium nitrate, and then slowly drop them into the three-necked flask through a separatory funnel. Butyl titanate forms TiO ₂ -Cr sol through hydrolysis and condensation reactions. Secondly, the obtained porous material-low molecular plugging carrier is put into the TiO ₂ -Cr sol body, and it is coated on the plugging surface during ultrasonic vibration. On the surface of the carrier, the number of coating times is 1, and the ultrasonic time is 10 minutes. Finally, the TiO ₂ -X precursor/C _surf. is heat-treated at a temperature of 300°C for 1 hour at a heating rate of 0.5°C/min; then roasted under nitrogen protection at a temperature of 300°C for 3 hours. Its crystal form is anatase, the size of the nanoparticles is 30-50nm, the specific surface area reaches 834m ² /g, and the TiO ₂ -Cr nanoparticles are loaded on the surface of the porous material.

Example 6: First, put 15g of coconut shell activated carbon into the shelf in the supercritical kettle. There is 20ml of isobutanol in the autoclave, and the temperature is raised to 300℃ according to the heating rate of 2℃/min. After the pressure is 7.1MPa, keep it for 2h; then Cool the supercritical kettle to room temperature to obtain a porous material-low molecular plugging carrier. Using the sol-gel method, mix 60g of butyl titanate with a purity of 99.0%, 3g of diethanolamine and 10g of absolute ethanol, add it into a three-necked flask, and stir evenly with a GS122 electronic constant speed stirrer. Take 20g of absolute ethanol, mix with 4g of distilled water and cerium nitrate, and then slowly drop them into the three-necked flask through a separatory funnel. Butyl titanate forms TiO ₂ sol through hydrolysis and condensation reactions. Secondly, the obtained porous material-low molecular plugging carrier is put into the TiO ₂ -Fe sol body, and it is coated on the surface of the plugging carrier during ultrasonic vibration. , the number of coatings is 1 time, and the ultrasonic time is 10 minutes. Finally, the TiO ₂ -X precursor/C _surf. is heat-treated at a temperature of 300°C for 1 hour at a heating rate of 1°C/min; then roasted under nitrogen protection at a temperature of 1000°C for 1 hour. Its crystal form is anatase, the size of the nanoparticles is 30-50nm, the specific surface area reaches 162m ² /g, and the TiO ₂ -Ce nanoparticles are loaded on the surface of the porous material.

Example 7: First, put 15g of coconut shell activated carbon into the shelf in the supercritical kettle. There is 20ml of isobutanol in the autoclave, and the temperature is raised to 160℃ according to the heating rate of 2℃/min. After the pressure is 13MPa, keep it for 2h; then put The supercritical kettle is cooled to room temperature to obtain a porous material-low molecular plugging carrier. Using the sol-gel method, mix 60g of butyl titanate with a purity of 99.0%, 3g of diethanolamine and 10g of absolute ethanol, add it into a three-necked flask, and stir evenly with a GS122 electronic constant speed stirrer. Take 20g of absolute ethanol, mix with 12g of distilled water and manganese nitrate, and then slowly drop them into the three-necked flask through a separatory funnel. Butyl titanate forms TiO ₂ -Mn sol through hydrolysis and condensation reactions. Secondly, put the obtained porous material-low molecular plugging carrier into the TiO ₂ -Mn sol, and coat it on the plugging surface during ultrasonic vibration. On the surface of the carrier, the number of times of coating is 5 times, and the ultrasonic time is 10 minutes. Finally, the TiO ₂ -X precursor/C _surf. was heat-treated at a temperature of 150°C for 1 hour at a heating rate of 1°C/min; then roasted under nitrogen protection at a temperature of 500°C for 2 hours. Its crystal form is anatase, the size of the nanoparticles is 30-50nm, the specific surface area reaches 781m ² /g, and the TiO ₂ -Mn nanoparticles are loaded on the surface of the porous material.

Example 8: First, put 15g of coconut shell activated carbon into the shelf in the supercritical kettle. There is 20ml of isobutanol in the autoclave, and the temperature is raised to 130℃ according to the heating rate of 2℃/min. After the pressure is 11MPa, keep it for 2h; then put The supercritical kettle is cooled to room temperature to obtain a porous material-low molecular plugging carrier. Using the sol-gel method, mix 60g of butyl titanate with a purity of 99.0%, 3g of diethanolamine and 10g of absolute ethanol, add it into a three-necked flask, and stir evenly with a GS122 electronic constant speed stirrer. Take 20g of absolute ethanol, mix with 4g of distilled water and 3g of silver nitrate, and then slowly drop them into the three-necked flask through a separatory funnel. Butyl titanate forms TiO ₂ -Ag sol through hydrolysis and condensation reactions. Secondly, put the obtained porous material-low molecular plugging carrier into the TiO ₂ -Ag sol, and coat it on the plugging surface during ultrasonic vibration. On the surface of the carrier, the number of coating times is 1, and the ultrasonic time is 10 minutes. Finally, the TiO ₂ -X precursor/C _surf. is heat-treated at a temperature of 200°C for 1 hour, and the heating rate is 1°C/min; and then roasted under nitrogen protection at a temperature of 600°C for 2 hours. Its crystal form is anatase, the size of the nanoparticles is 30-50nm, the specific surface area reaches 1268m ² /g, and the TiO ₂ -Ag nanoparticles are loaded on the surface of the porous material.

Claims (1)

1. A preparation process for loading TiO ₂ -X/C _surf.complex on the outside of the porous material, through the supersolubility, strong diffusivity and unique mass transfer properties of the fluid, the solute is dissolved to form a supersaturated solution, and the critical condition is resolved It leads to its crystallization and precipitation; using this method, the supercritical CO ₂ fluid is used as a solvent, and the porous material is used as a template to infiltrate the low-molecular-weight organic solution into the pores, and then through coagulation and precipitation, the pores of the porous material are blocked to prepare the porous material— —Low molecular plugging carrier; then use this as a double template, use the sol-gel method to prepare TiO ₂ -X sol and load it on the surface of the plugging carrier, and then synthesize a porous material with TiO ₂ on the outside by low-temperature heat treatment and high-temperature calcination -X/Csurf complex; It is characterized in that the specific preparation process is: (1) Through the supercritical fluid precipitation process, the low-molecular organic solution penetrates into the pores of the porous material, and the critical state is released to make it precipitate, and the porous material-low-molecular plugging carrier is prepared; (2) Using butyl titanate as a starting material, using absolute ethanol as a solvent, and diethanolamine as a chelating agent, under the interaction of distilled water and concentrated hydrochloric acid, synthesize TiO ₂ -X colloid; (3) Coating the TiO ₂ -X precursor sol on the porous material-low molecular plugging carrier through the sol-gel process to prepare the TiO ₂ -X precursor/C _surf. composite material; (4) TiO ₂ -X precursor/C _surf. composites were calcined at high temperature to obtain TiO ₂ -Fe/C _surf. , TiO ₂ -Ag/C _surf. , TiO ₂ -Mn/C _surf. , TiO ₂ - Cu/C _surf. is TiO ₂ -X/C _surf. composite nanomaterial; in the above formula, C _surf. is the carbon surface; The above-mentioned porous material is activated carbon; the low-molecular compound is isobutanol, stearic acid, paraffin, solid alcohol; The supercritical conditions: heating rate 2-4°C, temperature 34.1-300°C, pressure 7.1-50MPa; decritical conditions: first stop heating, let the supercritical tank cool down, and reach a temperature below the freezing point of the low-molecular compound; The inorganic precursors of X are iron nitrate, silver nitrate, copper nitrate, manganese nitrate; The above TiO ₂ -X precursor sol is coated on the porous material-low molecular plugging carrier: put the porous material-low molecular plugging carrier into the TiO ₂ -X sol, and then make the sol body Coated on the surface of the plugging carrier, the number of coatings is 1-8 times, and the ultrasonic time is 10-300min; Before the above-mentioned calcination, the TiO ₂ -X precursor/C _surf. is heat-treated at a temperature of 100-300°C for 1-3 hours, and a heating rate of 0.5-3°C/min; The above-mentioned calcination temperature is 300-1000°C, the time is 1-3h, and the heating rate is between 0.5-3°C/min.

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