CN106978652A - A kind of preparation method of the sour oxygen titanium precursors colloidal sol spinning solution of poly-vinegar and TiOx nano fiber photocatalyst - Google Patents

Abstract

The invention relates to a preparation method of a polyacetate titanyl precursor sol spinning solution and a titanium oxide nanofiber photocatalyst. Including the preparation of sol-spinning solution of poly(titania) acetate precursor, electrospinning, and heat treatment; , and the solvent are mixed evenly to obtain a spinning solution; the spinning solution is obtained by electrospinning technology to obtain poly(titanate) acetate precursor fibers; the precursor fibers are placed in a muffle furnace for heat treatment to obtain solid titanium oxide nanofibers or mesoporous oxidation Titanium nanofibers. The method has the characteristics of simple process flow, optimized fiber quality, and environmental protection, and is conducive to industrial production. The obtained titanium oxide nanofibers have excellent catalytic properties and can be used as photocatalytic materials for degrading organic pollutants.

Description

Photocatalysis of a poly-titania acetate precursor sol-spinning solution and titanium oxide nanofibers The preparation method of the agent

technical field

The invention relates to a method for preparing titanium oxide nanofibers in combination with an electrospinning technology, in particular to a method for preparing a poly-titanyl acetate precursor sol spinning solution, and belongs to the technical field of nano functional materials.

Background technique

With the rapid development of industry, the pollution of the environment by harmful gases, solid waste and sewage has become one of the great challenges facing the world. Water resources are one of the indispensable material bases for human to maintain life and develop economy. At present, the amount of sewage discharged from industries such as textiles and dyes is increasing, and water pollution is becoming more and more serious. Due to the high stubbornness and complex molecular structure of dyes, it is extremely difficult to degrade and mineralize, which seriously affects human survival and development. The effective treatment of pollutants has become an urgent problem to be solved. Among them, semiconductor photocatalytic oxidation technology can use clean solar energy to degrade organic pollutants, and does not need to consume a large amount of other substances except light, which can reduce the consumption of energy and raw materials, so it shows good development prospects in the field of environmental purification. .

In the field of photocatalytic decomposition, due to its high photocatalytic activity and oxidation ability, good chemical stability and thermal stability, no secondary pollution, non-irritating, safe and non-toxic, and convenient and easy to obtain, titanium oxide materials It has been widely used in environmental governance fields such as the decomposition of pollutants and air purification, and has become one of the most promising green catalysts. Titanium oxide with catalytic activity mainly has two crystal phases: anatase type and rutile type. Due to the difference in crystal structure, the difference in crystal mass density and electronic energy band structure, that is, there is a certain difference in the catalytic activity of the two crystal forms. The mass density of anatase type is slightly smaller than that of rutile type, and the band gap is slightly larger than that of rutile type. Rutile-type titanium oxide has poor oxygen adsorption capacity and small specific surface area, so photogenerated electrons and holes are easy to recombine, and the catalytic activity is affected to a certain extent. Therefore, anatase titanium oxide has higher catalytic activity. CN101314482A provides a method for synthesizing anatase-type titanium dioxide. The prepared anatase-type titanium dioxide fine powder has high catalytic activity; a degradation experiment is carried out under the irradiation of a 365-degree ultraviolet lamp, and the methyl orange solution is completely degraded within 15 minutes. However, it is difficult to recover titanium oxide fine powder after use, and it is easy to cause secondary pollution, which seriously limits its popularization and application.

Titanium oxide nanofibers are characterized by their unique one-dimensional shape, large specific surface area, high adsorption capacity, fast photoelectron transmission speed, and anisotropy, which are conducive to separation, recycling and reuse, and will not cause environmental pollution due to easy loss , can solve the limitation that nano-titanium oxide powder is difficult to recycle, easily causes secondary pollution, and is difficult to popularize and apply. CN1584156A has proposed a kind of preparation method of titanium dioxide fiber, with titanium tetrachloride as titanium source, with acetic acid or acetylacetone as ligand, need to select suitable precipitating separation agent, prepare precursor and then go through centrifuge spinning or dry spinning Precursor fibers were prepared by silk method, and titanium oxide fibers were obtained through steam pretreatment and high temperature sintering. Although the applicant obtained titanium oxide fibers with a minimum diameter > 2 μm in the previous research of the applicant, it was found through subsequent research that using titanium tetrachloride as the titanium source, the hydrolysis and polycondensation process is difficult to control, and there will inevitably be unremoved in the precursor. Impurities affect the degree of polymerization and purity. The aspect ratio of the obtained micron-scale fibers is not as large as that of nanofibers, and the efficiency of electron transport is relatively reduced. The catalytic activity needs to be further optimized. Choosing titanium alkoxide as the titanium source can avoid the incorporation of other impurity ions. However, titanium alkoxide is also easy to hydrolyze, and sometimes it is necessary to adjust the pH value of the solution to inhibit hydrolysis. CN100581648A discloses a preparation method of titanium dioxide fiber membrane prepared by electrospinning technology, wherein the preparation of spinning solution is to dissolve tetrabutyl titanate in absolute ethanol, and suppress the growth of tetrabutyl titanate with ethanol Hydrolysis, and then use hydrochloric acid to adjust the pH value of the ethanol solution of tetrabutyl titanate to control the hydrolysis and polycondensation process of the solution after adding water. However, the solution undergoes a series of hydrolysis and polycondensation to form a spinnable solution. The process is relatively slow, and the solution is adjusted with hydrochloric acid pH value, the Cl ^- in the prepared fiber membrane is difficult to remove in the post-treatment process, which will inevitably have a certain impact on the performance of the fiber. In the published articles on the preparation of titanium oxide nanofibers by electrospinning technology, titanium alkoxide is generally used for the preparation of spinning solution, and a solution with better spinnability is often obtained by adding a large amount of spinning aids. , due to the large amount of spinning aid, the solid content of the active component titanium oxide in the precursor fiber will be too low, which will adversely affect the properties of the obtained titanium oxide nanofibers.

At present, there are at least two problems in the preparation of titanium oxide nanofibers by electrospinning technology: one is that the specific surface area of titanium oxide nanofibers obtained by electrospinning is not high, and the application performance is limited to a certain extent. The porosity and specific surface area inside titanium nanofibers should become a major problem to be solved. Second, the mechanical properties of the electrospun titania nanofibers prepared after high temperature treatment are very poor, easy to break, and often exist in the form of short fibers or nanowires, which cannot fully utilize the advantages of nanofibers to obtain continuous and better mechanical properties. The titania nanofibers should also be a big problem to be solved.

Contents of the invention

Aiming at the deficiencies of the prior art, the present invention provides a method for preparing poly-titania acetate precursor fiber by electrospinning with poly-titania acetate precursor sol-spinning liquid, and then preparing titanium oxide nanofiber photocatalyst through heat treatment.

The technical problem to be solved in the present invention is to increase the solid content of titanium oxide in the precursor fiber, avoid the existence of excessive impurity ions, and improve the solution hydrolysis and polycondensation process time as much as possible without affecting the material performance, and the preparation strength and catalytic performance Excellent titanium oxide nanofibers.

Terminology Explanation:

Polyoxytitanium acetate (PET), the monomer name is dihydroxy diacetate titanium, and the monomer molecular formula is (CH ₃ COO) ₂ Ti(OH) ₂ . The molecular weight of the monomer is 199.97. Titanium oxide (TiO ₂ , molecular weight 79.87). The effective solid content of TiO ₂ refers to the ratio of conversion of (CH ₃ COO) ₂ Ti(OH) ₂ to TiO ₂ after heat treatment.

Titanium oxide nanofibers: the titanium oxide nanofibers described in the present invention include solid titanium oxide nanofibers and mesoporous titanium oxide nanofibers. The mesoporous titanium oxide nanofiber is a nanofiber with a pore structure.

P25: The code name of nano-titanium oxide powder photocatalyst, which refers to the white powder of titanium dioxide in the mixed phase of anatase crystal and rutile crystal (the weight ratio is about 71/29) with an average particle size of 25nm. Can be purchased in the market.

Technical scheme of the present invention is as follows:

A kind of preparation method of polyoxy titanyl acetate precursor sol spinning liquid, comprises steps:

(1) According to the molar ratio of tetrabutyl titanate:glacial acetic acid=1:1～4, take tetrabutyl titanate and slowly add glacial acetic acid, stir and react for 2～4h, obtain the solution containing polyoxytitanyl acetate; Then, concentrating the solution containing polyoxytitanyl acetate under reduced pressure at a temperature of 40 to 80°C to make a powder to obtain a polyoxytitanyl acetate precursor;

(2) According to the mass ratio of poly(titanate) acetate precursor: auxiliary agent: alcohol solvent=100:(0.4～4):(100～400), the poly(titanate) acetate precursor is first dissolved in the alcohol solvent, Then add additives, stir and dissolve at a temperature of 10-60°C to obtain a uniform sol-spinning solution of the precursor of polyoxytitanium acetate;

Described auxiliary agent is selected from polyethylene oxide, polyacrylic acid, polyvinyl alcohol, polyvinylpyrrolidone, polyethyleneimine, polyacrylamide, polyethylene glycol, polyethylene terephthalate, polyurethane, One of polyglycolic acid, polylactic acid or a combination thereof.

Preferably according to the present invention, the alcohol solvent is selected from one of absolute methanol, absolute ethanol or a combination thereof.

The method of the present invention is to prepare the precursor of polyoxytitanyl acetate, and make the precursor dissolve in anhydrous methanol or absolute ethanol solvent, so that a very small amount of auxiliary agent can be added, and the spinnable Better spinning solution. A small amount of additives can prevent a large amount of additives from reducing the solid content of the active component titanium oxide in the precursor fiber, which is of great significance for improving the performance of the obtained titanium oxide nanofibers.

Preferably according to the present invention, the tetrabutyl titanate:glacial acetic acid=1:2.5-3.5 molar ratio.

Preferably according to the present invention, the mass ratio of the poly(titania) acetate precursor:auxiliary:solvent=100:(0.7-2):(100-300).

According to the present invention, the condition for dissolving the poly(titania) acetate precursor in the alcohol solvent is: stirring and dissolving at a temperature of 0-60° C. to form a solution.

A kind of preparation method of titanium oxide nanofiber photocatalyst, comprise the preparation of above-mentioned polyoxy titanyl acetate precursor sol spinning liquid, also comprise the following steps:

(3) Electrospinning: Place the sol spinning solution of the precursor of polyoxytitanium acetate in a syringe with a stainless steel needle in the spinning device, and perform electrospinning by high-voltage electrospinning method at an ambient temperature of 20-35°C, relative Under the condition of humidity 30-70%, the applied voltage is between 8-28kV, the flow rate of spinning solution is 0.5-3.5mL/h, the inner diameter of the positive stainless steel needle is 0.19-0.60mm (type 4-9#), the needle and the collection fiber The distance between the rotating cylinder of the device is 8-35 cm, and the precursor fiber of polyoxytitanyl acetate is obtained;

(4) Heat treatment: place the poly-titania acetate precursor fiber in a muffle furnace for heat treatment, and raise the temperature to 300-1000°C at a heating rate of 0.4-5°C/min under air conditions and keep it warm for 1-3h. Poly titanyl acetate precursor fibers undergo sufficient decomposition and crystallization to obtain solid titanium oxide nanofibers, or,

Put the poly-titanyl acetate precursor fiber in a sintering furnace for heat treatment, raise the temperature to 100-200°C at a heating rate of 3-6°C/min, start feeding steam, and then raise the temperature at a heating rate of 0.5-2.5°C/min To 300-900°C, preferably 500-750°C, more preferably 600-700°C, stop feeding steam and keep warm, so that the poly-titania acetate precursor fibers are fully decomposed and crystallized into mesoporous titanium oxide nanofibers; or,

Put the poly-titanyl acetate precursor fiber in a sintering furnace for heat treatment, raise the temperature to 100-200°C at a heating rate of 3-6°C/min, start feeding steam, and then raise the temperature at a heating rate of 0.5-1°C/min When the temperature reaches 350-550° C., stop feeding steam, and then raise the temperature to 600-700° C. at a rate of 1.5-2° C./min and keep it warm for 2 hours to obtain mesoporous titanium oxide nanofibers.

Preferably according to the present invention, in step (3), the electrospinning conditions are: ambient temperature 20-30°C, relative humidity 35-60%, applied voltage 10-24kV, spinning solution flow rate 0.5-2.5mL /h, the inner diameter of the stainless steel needle is 0.26-0.51 mm (type 5-8#), and the distance between the positive stainless steel needle and the drum of the fiber collecting device is 10-30 cm. In the electrospinning step of the present invention, the flow rate of the spinning solution should be strictly controlled. The flow rate of the spinning solution has an important influence on the quality of the titanium oxide nanofiber product. When the flow rate is high, there are a large number of beads in the electrospun fiber. The obtained titanium oxide fibers are pulverized in large quantities and have poor catalytic performance. In the present invention, it is further preferred that the flow rate of the spinning solution is 1-2 mL/h.

Preferably according to the present invention, in step (3), the fiber collecting device is laid with aluminum foil.

Preferably according to the present invention, in step (4), the preferred temperature for placing the poly-titania acetate precursor fiber in a muffle furnace for heat treatment is 600-900°C.

Preferably according to the present invention, in step (4), when preparing solid titanium oxide nanofibers, when the final treatment temperature is 700-800°C, a two-stage heating method is adopted: first, the temperature is raised to 600-600°C at a heating rate of 0.5°C/min. 700°C, then raise the temperature to 750-800°C at a heating rate of 1°C/min and keep for 2 hours.

Preferably according to the present invention, in step (4), when preparing solid titanium oxide nanofibers, when the final treatment temperature is 900°C to 1000°C, a three-stage heating method is adopted: first, the temperature is raised to 600°C at a heating rate of 0.5°C/min. ~700°C, then raise the temperature to 750-800°C at a heating rate of 1°C/min, then raise the temperature to 900-1000°C at a heating rate of 2°C/min, and keep for 2 hours. Compared with directly raising the temperature to 900-1000°C for 2 hours at a constant heating rate, the titanium oxide nanofiber product obtained by the three-stage heating method has good fiber crystallization and uniform grain growth, and has good catalytic degradation activity.

The obtained solid titanium oxide nanofiber has a diameter of 200-800 nm and a length of 2-8 cm. The specific surface area is 1-12m ² /g.

Preferably according to the present invention, in step (4), when preparing mesoporous titanium oxide nanofibers, when the final treatment temperature is 600-700°C, after the steam is introduced, a two-stage heating method is adopted: first, the temperature is increased at 1-1.5°C/ After heating up to 300-350°C at a heating rate of 1-2.5°C/min, raise the temperature to 600-700°C at a heating rate of 1-2.5°C/min, stop feeding steam, and keep warm for 2 hours. The mesoporous titania nanofiber product obtained by the two-stage heating method has high catalytic degradation activity.

Preferably according to the present invention, the steam is ammonia, ethanol, water vapor, mixed steam of water and ethanol or mixed steam of water and hydrogen peroxide. Further preferably, the steam flow rate is 2.0-3.4 L/h.

The mesoporous titanium oxide nanofiber prepared by the invention is a nanofiber with an irregular pore structure. Pores exist both on the surface and inside of the fiber. See attached drawing 7. The mesoporous titanium oxide fiber obtained by the invention has a diameter of 300-600 nm, a length of 2-8 cm, a specific surface area of 20-130 m ² /g, and a pore size of 1-50 nm. The pore volume is 0.08-0.14 cm ³ /g.

The titanium oxide nanofiber prepared by the invention is anatase titanium dioxide.

Technical characteristics and excellent effects of the present invention:

1. The method of the present invention is to prepare the poly-titanyl acetate precursor first, and then dissolve it in an alcohol solvent, so that a small amount of auxiliary agent can be added to obtain a spinning solution with better spinnability. The quality of the additive used in the present invention is far less than that of the titanium source, and the loss on ignition is greatly reduced, avoiding a large amount of additives from reducing the solid content of the active ingredient titanium oxide in the precursor fiber; The effective solid content is 50-55%. It is beneficial to the performance improvement of titanium oxide nanofibers prepared in subsequent steps.

2. The titanium oxide nanofiber prepared by the method of the present invention has excellent mechanical properties, single composition, no impurities, and high purity after high-temperature treatment, and is a titanium oxide nanofiber that can be used for photocatalysis at relatively high temperature for a long time. The titanium oxide nanofiber prepared by the method of the invention can still maintain the anatase crystal phase with high catalytic activity at relatively high temperature. At the same time, the prepared titanium oxide nanofibers have good mechanical properties.

3. The titanium oxide precursor fiber obtained by the method of the present invention is treated with steam, and most of the organic ligands in the precursor fiber can be removed at a lower temperature to promote fiber crystallization to obtain mesoporous titanium oxide nanofibers, and the specific surface area can be increased. Large, further improving the catalytic performance of titanium oxide nanofiber materials. In the prior art, template-induced self-assembly is generally used to prepare mesoporous oxide fibers. For example, block copolymer polyoxyethylene-polyoxypropylene-polyoxyethylene polyether is used as a template to induce self-assembly to form worm-like channels. Structural fibers. The disadvantage is that the hydrolysis and polycondensation process is not easy to control. The method of the invention successfully prepares mesoporous titanium oxide nanofibers with excellent catalytic performance without using soft templates and hard templates.

4. The titanium oxide nanofiber of the present invention is used as a photocatalytic material and is easy to recycle, which overcomes the existing problem that P25 is difficult to recycle and easily produces secondary pollution.

5, in the method of the present invention, do not use pH regulators containing chloride ions such as hydrochloric acid, there is no Cl in the fibrous membrane ^- aftertreatment difficult problem, avoid the adverse effect on the performance of titanium oxide nanofibers; The present invention uses cheap and easy-to-obtain Glacial acetic acid is used as the ligand of polyoxy titanyl acetate, and at the same time, it also serves as a pH value regulator. It is easier to control the hydrolysis and polycondensation process. The process is simple, and the production cost is reduced while increasing the yield. , purity and stability.

6. The method of the present invention has the characteristics of simple process flow, easy adjustment and control of operating conditions, quality optimization of titanium oxide nanofibers, and environmental protection, which is beneficial to industrial production.

Description of drawings

Fig. 1 is the optical picture of the poly(titanic acetate) precursor fiber that embodiment 1 step (3) makes.

Fig. 2 is a SEM photo of titanium oxide nanofibers heat-treated at 900° C. for 2 hours by the method of Example 4.

Fig. 3 is a SEM photo of a single titanium oxide nanofiber heat-treated at 900° C. for 2 hours by the method of Example 4.

Fig. 4 is the SEM photograph of the cross-section of titanium oxide nanofibers heat-treated at 900° C. for 2 hours by the method of Example 4.

FIG. 5 is the XRD spectrum of titanium oxide nanofibers prepared according to the method of Example 4 under different heat treatment temperature conditions.

Fig. 6 is a graph showing the degradation of titanium oxide nanofibers (20 mg) prepared under different heat treatment temperatures according to the method of Example 4-6 to 50 mL of a methyl orange solution with a concentration of 20 mg/L under the irradiation of ultraviolet light. The heat treatment temperatures corresponding to the shown curves from top to bottom are 1000°C, 400°C, 500°C, 600°C, 950°C, 700°C, 800°C, and 900°C.

FIG. 7 is a TEM photo of the mesoporous titanium oxide nanofibers heat-treated to 650° C. and kept for 2 hours in Example 8. FIG. The irregular pore structure runs through the whole fiber.

Fig. 8 is the XRD spectrum of the mesoporous titanium oxide nanofibers prepared according to the method of Example 8 under different heat treatment temperature conditions.

9 is a diagram showing the degradation of 50 mL of methyl orange solution with a concentration of 20 mg/L under the irradiation of ultraviolet light by mesoporous titanium oxide nanofibers (20 mg) prepared under different heat treatment temperatures according to the method of Example 8.

Fig. 10 is the isothermal adsorption-desorption curve and pore size distribution curve (inset) of mesoporous titanium oxide nanofibers prepared according to the method of Example 8 under different heat treatment temperature conditions.

Fig. 11 is a degradation curve of mesoporous titanium oxide nanofibers (20 mg) prepared by the method of Examples 9-11 degrading 50 mL of a methyl orange solution with a concentration of 20 mg/L under the irradiation of ultraviolet light.

detailed description

The present invention will be further described below in conjunction with embodiment, but not limited thereto.

The inner diameters of electrospinning stainless steel needles 5# and 7# used in the examples are 0.26 and 0.41 mm, respectively.

Embodiment 1: Preparation of titanium oxide nanofibers

(1) Preparation of poly(titania) acetate precursor

Weigh 100g of tetrabutyl titanate and 52.94g of glacial acetic acid, fully stir and react for 3 hours to obtain a golden yellow solution, that is, poly-titanyl acetate solution; place it in a flask, and concentrate under reduced pressure at a temperature of 65°C for 6 hours until obtaining The dry solid, namely the poly(titalyl acetate) precursor; the stability test of the obtained precursor: the sol formed by dissolving the just prepared poly(titalyl acetate) precursor powder in anhydrous methanol solvent can be placed continuously for more than 6 weeks, Still clear and transparent. The obtained precursor powder was placed for 4 weeks and then dissolved in anhydrous methanol solvent to form a sol, which could be placed continuously for more than 6 weeks and remained clear and transparent. It shows that the stability of the precursor is very good.

(2), preparation of spinning solution

Dissolve 10g of poly(titania) acetate precursor in 23g of anhydrous methanol at 40°C and fully stir to form a solution, then add 0.35g of polyvinylpyrrolidone into the solution, and continue stirring at 40°C to obtain a uniform transparent spinning solution .

(3), Electrospinning

Put the precursor spinning solution into a syringe with a stainless steel needle spinning device, under the conditions of temperature 25°C and relative humidity 55%, apply a voltage value of 20kV, stainless steel needle type 7#, gravity propel the spinning solution in the syringe, The flow rate is 2mL/h, the distance between the stainless steel needle of the positive electrode and the drum of the fiber collecting device covered with aluminum foil on the negative electrode is 20cm, and the spun fibers are drawn and collected on the drum to obtain the precursor fiber of titanyl acetate , with a diameter of 0.8-1 μm, as shown in Figure 1.

(4), heat treatment

Put the poly(titalyl acetate) precursor fibers in a muffle furnace for heat treatment. Under air conditions, raise the temperature to 900°C at a rate of 1°C/min and hold for 2 hours to fully decompose and crystallize the poly(titalyl acetate) precursor Converted into titanium oxide nanofibers, maintaining the anatase phase, with a diameter of 400-600nm, a length of 2-8cm, a specific surface area of 11m ² /g, and high tensile strength.

After testing, the effective solid content of the transformation from the poly-titania acetate precursor fiber to the titanium oxide fiber is 50-55%.

Comparative example 1:

As described in Example 1, the difference is that step (1) weighs 100 g of tetrabutyl titanate and 15 g of glacial acetic acid (molar ratio is about 1:0.85), fully stirs and reacts for 3 hours to obtain a golden yellow solution (polyacetate oxygen Titanium solution); it was placed in a flask and concentrated under reduced pressure at a temperature of 65° C., but the light yellow solid as described in Example 1 could not be obtained.

Comparative example 2:

As described in Example 1, the difference is that 0.5 g of polyvinylpyrrolidone is added in step (2), and the diameter of the precursor fiber electrospun in step (3) is 1.5-2 μm, with a lot of fiber adhesion.

Comparative example 3:

As described in Example 1, the difference is that the flow rate of the spinning solution in the gravity propulsion syringe in step (3) is 4mL/h, and there are a large number of beads in the fibers produced by electrospinning, and a large amount of titanium oxide fibers obtained after heat treatment pulverization and poor catalytic performance.

Example 2:

As described in Example 1, the difference is that 100g tetrabutyl titanate and 23.49g glacial acetic acid are weighed in step (1), fully stirred and reacted for 3h to obtain a golden yellow solution, i.e. poly-titanyl acetate solution; Concentrate under reduced pressure in a flask for 9 hours at a temperature of 65° C. to obtain a dry light yellow solid, which is the precursor of poly(titanate) titanyl acetate. The sol formed by dissolving the obtained precursor powder in an alcoholic solvent can be placed stably for 5 weeks.

Example 3:

As described in Example 1, the difference is that step (1) weighs 100g tetrabutyl titanate and 70.5g glacial acetic acid, fully stirs and reacts for 3 hours, and obtains a golden yellow solution, that is, polyoxytitanyl acetate solution; Place in a flask, concentrate under reduced pressure at a temperature of 65° C., and obtain a dry light yellow solid, which is a poly(titanate) acetate precursor. After the obtained precursor powder is placed for 4 weeks, the sol formed by dissolving it in an alcoholic solvent can be placed stably for 3 weeks, and precipitation will gradually begin to form after more than 3 weeks.

Comparative example 4:

As described in Example 1, the difference is that step (1) weighs 100g of tetrabutyl titanate and 75.5g of glacial acetic acid (molar ratio is about 1:4.247), fully stirred and reacted for 3 hours to obtain a golden yellow solution, That is, poly-titanyl acetate solution; it is placed in a flask and concentrated under reduced pressure at a temperature of 65° C. to obtain a dry light yellow solid, namely the precursor of poly-titanyl acetate. Compared with the poly(titania) acetate precursor prepared in Example 1, the stability is poor, and the obtained precursor powder is dissolved in an alcohol solvent after being placed for 4 weeks, and the sol formed after being placed for 4 days will gradually begin to form a precipitate.

Example 4:

As described in Example 1, the difference is that in step (4), the poly(titanate) acetate precursor fiber is placed in a muffle furnace for heat treatment, and after heating up to 600°C at a heating rate of 0.5°C/min, The temperature was raised to 800°C at a heating rate of ℃/min, and then raised to 900°C, 950°C or 1000°C at a heating rate of 2°C/min, kept for 2 hours, and cooled naturally to obtain titanium oxide nanofibers with a diameter of 400-600nm. The obtained fiber diameter distribution difference is small, and the fiber crystallization is good.

Among them, the SEM photo of titanium oxide nanofibers heat-treated at 900°C for 2 h is shown in Figure 2, the SEM photo of a single titanium oxide nanofiber is shown in Figure 3, and the SEM photo of the cross-section of titanium oxide nanofibers is shown in Figure 4 .

The XRD patterns of titanium oxide nanofibers prepared under different heat treatment temperature conditions are shown in FIG. 5 .

This three-stage heating method has higher catalytic degradation activity than the product directly heated to 900°C, 950°C or 1000°C for 2 hours. See Figure 6 for the degradation curve.

Example 5:

As described in Example 1, the difference is that in step (4), the poly(titania) acetate precursor fiber is placed in a muffle furnace for heat treatment, and the temperature is raised to 400°C, 500°C or 400°C at a heating rate of 0.5°C/min. 600°C, heat preservation for 2 hours, and natural cooling to obtain titanium oxide nanofibers. The resulting fiber degradation curve is shown in Figure 6.

Embodiment 6:

As described in Example 1, the difference is that in step (4), the poly(titanate) acetate precursor fiber is placed in a muffle furnace for heat treatment, and after heating up to 600°C at a heating rate of 0.5°C/min, then Raise the temperature to 700°C or 800°C at a heating rate of 1°C/min, keep it warm for 2 hours, and cool down naturally to obtain titanium oxide nanofibers. The resulting fiber degradation curve is shown in Figure 6.

Accompanying drawing 6 is the degradation curve of the fiber under different heat treatment temperatures of this embodiment 4-6. The degradation test conditions are: 20 mg of titanium oxide nanofibers are degraded to 50 mL of methyl orange solution with a concentration of 20 mg/L under the irradiation of ultraviolet light. 400°C, 500°C, 600°C, 950°C, 700°C, 800°C or 900°C.

Embodiment 7:

As described in Example 4, the difference is that the rutile phase appears in the obtained titanium oxide nanofibers after being kept at 900° C. for 5 hours, and the catalytic activity is reduced.

Example 8: Preparation of mesoporous titanium oxide nanofibers, heat treatment temperatures were 350°C, 450°C, 550°C, 650°C, and 700°C.

As described in Example 1, the difference is:

In step (4), the poly-titanium acetate precursor fiber is placed in a sintering furnace for heat treatment, and the temperature is first raised to 100°C at a heating rate of 3-6°C/min, and water vapor is passed in at a rate of 3.1L/h ; Heat up to the heat treatment temperature of 350°C, 450°C or 550°C at a rate of 1°C/min, stop feeding steam and keep it warm for 2 hours; or,

Adopt two-stage heating method: firstly raise the temperature to 350°C at a heating rate of 1°C/min, then raise the temperature to 650°C or 700°C at a heating rate of 2°C/min, stop feeding steam, and keep warm for 2 hours.

The obtained mesoporous titanium oxide nanofiber has a diameter of 300-600 nm, a specific surface area of 20-130 m ² /g, and a pore size of 2-50 nm. The irregular pore structure runs through the whole fiber. As shown in Figure 7.

The XRD patterns of the mesoporous titania nanofibers prepared according to the above different heat treatment temperatures are shown in FIG. 8 .

Degradation experiments of the mesoporous titanium oxide nanofibers prepared at the above different heat treatment temperatures: the prepared mesoporous titanium oxide nanofibers (20 mg) degrade 50 mL of methyl orange solution with a concentration of 20 mg/L under the irradiation of ultraviolet light, and the obtained The graph is shown in Figure 9. Among them, the catalytic activity of mesoporous titania nanofibers obtained at 650°C and 700°C for 2 hours is comparable to that of P25 and slightly better than that of P25.

The isothermal adsorption-desorption curves and pore size distribution curves (inset) of the mesoporous titanium oxide nanofibers prepared under the above different heat treatment temperature conditions are shown in Fig. 10 .

Embodiment 9:

As described in Example 1, the difference is that in step (4), the poly-titanyl acetate precursor fiber is placed in a sintering furnace for heat treatment. Water steam was introduced, the steam flow rate was 3.1L/h, the temperature was raised to 350°C at a heating rate of 1°C/min, the steam was stopped, and then the temperature was raised to 650°C at a heating rate of 1.5°C/min and kept for 2 hours. The catalytic activity of the porous titanium oxide nanofibers is slightly lower than that of the mesoporous titanium oxide nanofibers obtained by directly passing steam to 650° C. in Example 8, as shown in FIG. 11 .

Example 10:

As described in Example 1, the difference is that in step (4), the poly-titanyl acetate precursor fiber is placed in a sintering furnace for heat treatment, and the temperature is first raised to 100 °C at a heating rate of 3-6 °C/min, and water Steam, the steam flow rate is 3.1L/h, the temperature is raised to 450°C at a heating rate of 1°C/min, the steam is stopped, and then the temperature is raised to 650°C at a heating rate of 1.5°C/min and kept for 2h, the obtained mesoporous oxidation The catalytic activity of the titanium nanofibers is slightly lower than that of the mesoporous titanium oxide nanofibers obtained by direct steaming to 650° C. in Example 8, as shown in FIG. 11 .

Example 11:

As described in Example 1, the difference is that in step (4), the poly-titanyl acetate precursor fiber is placed in a sintering furnace for heat treatment, and the temperature is first raised to 100 °C at a heating rate of 3-6 °C/min, and water Steam, the steam flow rate is 3.1L/h, the temperature is raised to 550°C at a heating rate of 1°C/min, the steam is stopped, and then the temperature is raised to 650°C at a heating rate of 1.5°C/min and kept for 2 hours, and the obtained mesoporous The catalytic activity of titania nanofibers is comparable to that of P25, as shown in Figure 11.

Examples 9-11 above illustrate that the fiber is treated in a steam atmosphere to 350°C and then raised to 650°C, or the fiber is treated in a steam atmosphere to 450°C and then raised to 650°C, or the fiber is treated in a steam atmosphere to 550°C Then raise it to 650°C and treat it in air atmosphere, which is beneficial to the crystallization of fibers. The grain growth rate of the fiber in the air atmosphere is higher than that in the water vapor atmosphere, the specific surface area of the fiber is reduced, but the crystallinity of the fiber material is improved.

Claims (10)

1. A preparation method of a titanium oxyacetate precursor sol spinning solution comprises the following steps:

(1) according to the weight ratio of tetrabutyl titanate: weighing tetrabutyl titanate and slowly adding the tetrabutyl titanate into glacial acetic acid at a molar ratio of 1: 1-4, and stirring for reacting for 2-4 h to obtain a solution containing the poly (oxytitanium acetate); then, concentrating the solution containing the poly-titanium-oxy-acetate under reduced pressure at the temperature of 40-80 ℃ to prepare powder, thus obtaining a poly-titanium-oxy-acetate precursor;

(2) according to a precursor of the poly (titanium oxyacetate): auxiliary agent: dissolving a titanium oxyacetate precursor in an alcohol solvent according to the mass ratio of (0.4-4) to (100-400), adding an auxiliary agent, and stirring and dissolving at the temperature of 10-60 ℃ to obtain a uniform titanium oxyacetate precursor sol spinning solution;

the auxiliary agent is selected from one or the combination of polyethylene oxide, polyacrylic acid, polyvinyl alcohol, polyvinylpyrrolidone, polyethyleneimine, polyacrylamide, polyethylene glycol terephthalate, polyurethane, polyglycolic acid and polylactic acid.

2. The method of preparing a titanyl acetate precursor sol spinning dope according to claim 1, wherein the alcohol solvent is selected from one of absolute methanol, absolute ethanol or a combination thereof.

3. The method for preparing the titanyl acetate precursor sol spinning solution according to claim 1, wherein the molar ratio of tetrabutyl titanate to glacial acetic acid is 1: 2.5-3.5; preferably, the precursor of the poly (titanyl acetate): the mass ratio of the auxiliary agent to the solvent is 100 (0.7-2) to 100-300.

4. A method for preparing a titania nanofiber photocatalyst, comprising the preparation of the titanyl acetate precursor sol spinning solution according to any one of claims 1 to 3, further comprising the steps of:

(3) electrostatic spinning: placing the titanium poly-acetate precursor sol spinning solution into an injector with a stainless steel needle head of a spinning device, performing electrostatic spinning by adopting a high-voltage electrostatic spinning method, applying a voltage of 8-28 kV under the conditions of an ambient temperature of 20-35 ℃ and a relative humidity of 30-70%, wherein the flow speed of the spinning solution is 0.5-3.5 mL/h, the inner diameter of the positive stainless steel needle head is 0.19-0.60 mm, and the distance between the needle head and a rotary drum of a fiber collecting device is 8-35 cm, so as to prepare the titanium poly-acetate precursor fiber;

(4) and (3) heat treatment: placing a titanium oxide precursor fiber in a muffle furnace for heat treatment, heating to 300-1000 ℃ at a heating rate of 0.4-5 ℃/min under the air condition, and preserving heat for 1-3 hours to fully decompose and crystallize the titanium oxide precursor fiber to prepare a solid titanium oxide nanofiber, placing the titanium oxide precursor fiber in a sintering furnace for heat treatment, heating to 100-200 ℃ at a heating rate of 3-6 ℃/min, starting to introduce steam, heating to 300-900 ℃, preferably 500-750 ℃, further preferably 600-700 ℃ at a heating rate of 0.5-2.5 ℃/min, stopping introducing the steam, and preserving heat to fully decompose and crystallize the titanium oxide precursor fiber to convert the titanium oxide nanofiber into mesoporous titanium oxide nanofibers; or,

and (2) placing the titanium oxide precursor fiber in a sintering furnace for heat treatment, heating to 100-200 ℃ at a heating rate of 3-6 ℃/min, starting to introduce steam, heating to 350-550 ℃ at a heating rate of 0.5-1 ℃/min, stopping introducing the steam, heating to 600-700 ℃ at a heating rate of 1.5-2 ℃/min, and preserving heat for 2 hours to obtain the mesoporous titanium oxide nanofiber.

5. The method for preparing the titanium oxide nanofiber photocatalyst according to claim 4, wherein in the step (3), the electrospinning conditions are as follows: the environment temperature is 20-30 ℃, the relative humidity is 35-60%, the applied voltage is 10-24 kV, the flow rate of the spinning solution is 0.5-2.5 mL/h, the inner diameter of the stainless steel needle is 0.26-0.51 mm, and the distance between the positive stainless steel needle and the rotary drum of the fiber collecting device is 10-30 cm; wherein the flow rate of the spinning solution is preferably 1-2 mL/h.

6. The method for preparing the titanium oxide nanofiber photocatalyst according to claim 4, wherein in the step (4), when the maximum treatment temperature is 900 to 1000 ℃ in preparing the solid titanium oxide nanofiber, a three-stage temperature raising mode is adopted: heating to 600-700 ℃ at a heating rate of 0.5 ℃/min, heating to 750-800 ℃ at a heating rate of 1 ℃/min, heating to 900-1000 ℃ at a heating rate of 2 ℃/min, and keeping the temperature for 2 h.

7. The method for preparing the titanium oxide nanofiber photocatalyst according to claim 4, wherein the diameter of the solid titanium oxide nanofiber obtained in the step (4) is 200-800 nm, and the length is 2-8 cm.

8. The method for preparing the titanium oxide nanofiber photocatalyst according to claim 4, wherein the steam in the step (4) is ammonia gas, ethanol, water vapor, mixed steam of water and ethanol, or mixed steam of water and hydrogen peroxide.

9. The method for preparing the titanium oxide nanofiber photocatalyst according to claim 4 or 8, wherein the steam aeration amount is 2.0 to 3.4L/h.

10. The method for preparing the titanium oxide nanofiber photocatalyst according to claim 4, wherein the mesoporous titanium oxide nanofiber prepared in the step (4) has a diameter of 300 to 600nm, a length of 2 to 8cm, and a specific surface area of 20 to 130m²The pore size is 1-50 nm.