CN104923199A - Preparation method for anatase TiO2 photocatalytic material with 1,100 DEG C high temperature stability - Google Patents

Abstract

The invention relates to a preparation method for an anatase TiO2 photocatalytic material with 1,100 DEG C high temperature stability. The preparation method comprises the following specific steps: mixing tetraethoxysilane (TEOS), ethanol and water at a certain proportion, uniformly stirring, adding tetrabutyl titanate (TBOT), continuing stirring for 20 min, adding a certain amount of hydrofluoric acid as a catalyst, stirring uniformly, then allowing the mixture to stand still, waiting for gelating, and placing the gelated mixture in an ethanol supercritical kettle for supercritical drying after 3-day ageing and replacing, wherein the drying temperature is 300 DEG C, and the intensity of pressure is as high as 12 MPa. Titanium oxide obtained after drying is in the anatase phase, and after being thermally treated at the temperature of 1,100 DEG C, titanium oxide still keeps the anatase phase and relatively high photocatalytic activity.

Description

A kind of Anatase TiO with 1100 DEG C of high-temperature stabilities 2the preparation method of catalysis material

Technical field

The present invention relates to the preparation method of the titanium dioxide with high-temperature stability, it still keeps Anatase and good photocatalysis performance after 1100 DEG C of high-temperature heat treatment.

Background technology

Along with the development of industrial technology, pollution problem becomes more and more serious, becomes one of world today's problem demanding prompt solution.Conductor photocatalysis material has the potential ability solving environmental pollution, receives the extensive concern of more and more Chinese scholars.Wherein, titanic oxide material, owing to having high, the clean feature such as nontoxic, anticorrosive, inexpensive of catalytic activity, has good application prospect.

In general, titanium dioxide exists with three kinds of crystalline phase forms usually at occurring in nature: brookite, Anatase and Rutile Type.Wherein, Rutile Type is the most stable, and after high-temperature heat treatment, brookite and Anatase all can change to Rutile Type.Because of it, to have refractive index high, and high/low temperature good stability, the features such as coloring is good, are often used to dyestuff, radioresistance coating and cosmetic industry.And anatase phase titanium dioxide has high catalytic activity and lower electron-hole recombination rate due to it, thus obtain in the field such as photocatalysis, solar cell and study widely.Except the crystal structure characteristic of anatase titania self, its crystallite dimension, particle configuration, surface characteristic, specific area etc. all can produce considerable influence to its catalytic performance.Wherein, introduce defect by doping, thus reduction electron-hole recombination rate is a kind of effective method improving catalytic performance.

In addition, anatase titania then can change to Rutile Type after 600-800 DEG C of heat treatment, causes its photocatalysis performance greatly to reduce, thus limits it and preparing the application in photocatalysis ceramics etc.Therefore, prepare the highly efficient titania catalysis material with high-temperature stability and there is its necessity.

Summary of the invention

The object of the present invention is to provide a kind of Anatase TiO with high-temperature stability ₂the preparation method of catalysis material.

The present invention proposes the Anatase TiO of high-temperature stable ₂the preparation method of catalysis material, is characterized in that concrete steps are as follows:

(1) 6ml tetraethyl orthosilicate is dissolved in absolute ethyl alcohol, adds deionized water and stirring evenly, obtain clarifying mixed solution;

(2) slowly add in above-mentioned solution by 1-36ml tetra-n-butyl titanate, adularescent floccule produces at once, this product be hydrolyzed rapidly for butyl titanate chance water.Wherein, reagent volume ratio is butyl titanate: ethyl orthosilicate: water: hydrofluoric acid=(1-36) ml:6ml:1.5ml:1.25ml, etoh solvent volume be ethyl orthosilicate and butyl titanate volume and twice;

(3) Keep agitation 20 min, floccule dissolves, and adds hydrofluoric acid solution as catalyst, obtains clear sol after stirring;

(4) by clear sol sealing and standing, its gel is treated; Silica is formed coated to titanium oxide, hinder the grain growth of titanium oxide in drying and heat treatment process, serves important function to suppression crystal transition;

(5) continue after gel-forming to leave standstill aging 18-24 hour, then carry out solvent replacement with ethanol, removing excessive moisture and impurity;

(6) carry out HTHP ethanol supercritical drying after having replaced, temperature is 300 DEG C, and the most promotion of pressure is to 12MPa, and high-temperature supercritical improves titania meterial crystallinity, to suppress crystal transition under its high temperature further.

Beneficial effect of the present invention is:

1) method that the titania-silica colloidal sol adopted coagulates altogether, obtains titanium oxide gel by simple mode on the one hand, on the other hand doped silicon oxide in titanium oxide, is conducive to the photocatalytic activity and the high-temperature stability that improve titanium oxide.

2) sol-gel method will be adopted titanium oxide and silica In-situ reaction, and improve two-phase distributing homogeneity, in prepared composite, the oxidized silicon of titanium oxide is evenly coated.

3) adopt the drying means of Ethanol supercritical, prepared material has larger specific area, is conducive to reinforcing material catalytic performance.

4) improve supercritical temperature and pressure, be conducive to titanium oxide grain and formed, improve material heat resistance.

Accompanying drawing explanation

Fig. 1 is embodiment 2 sample photo.

Fig. 2 is embodiment 3 sample photo.

Fig. 3 is the TEM photo in embodiment 3 after heat treatments at different.

Fig. 4 is the XRD figure in embodiment 3 after heat treatments at different.

Fig. 5 is the sample photocatalysis characterization test result in embodiment 3 after heat treatments at different.

Fig. 6 is embodiment 4 sample photo.

Detailed description of the invention

The invention will be further described by the following examples, but these embodiments must not be used for explaining limiting the scope of the invention.

embodiment 1:be dissolved in 14ml ethanol by 6ml ethyl orthosilicate, it is even to add 1.5ml deionized water and stirring.Add 1ml butyl titanate in this solution, Keep agitation is even.Add catalyst hydrofluoric acid 1.25ml again, obtain clear sol.After leaving standstill gel, through overaging, solvent replacement, supercritical drying process, obtain silica-titania composite aerogel.

embodiment 2:as embodiment 1 process, be dissolved in 32ml ethanol by 6ml ethyl orthosilicate, it is even to add 1.5ml deionized water and stirring.Add 9.8ml butyl titanate in this solution, Keep agitation is even.Add catalyst hydrofluoric acid 1.25ml again, obtain clear sol.After leaving standstill gel, through overaging, solvent replacement, supercritical drying process, obtain aeroge.

Fig. 1 is the sample photo obtained.Gained sample is translucent shape, and specific area is 327m ²/ g, average pore size is about 22nm.

embodiment 3: as embodiment 1 process, continue to reduce silica content, be dissolved in 42 ml ethanol by 6 ml tetraethyl orthosilicates, it is even to add 1.5 ml deionized water and stirring.Slowly add 15ml butyl titanate in this solution, now adularescent floccule produces, Keep agitation about 20 min, and floccule dissolves.Add 1.25ml hydrofluoric acid solution again, after stirring, obtain clear sol, then above-mentioned colloidal sol is left standstill and treat its gel.After gel, aging one day, then carry out solvent with ethanol and replace 2 times, 1 times/day, removing excessive moisture and impurity.Carry out high temperature ethanol supercritical drying after replacement completes, temperature 300 DEG C, the most promotion of pressure is to 12MPa.

Fig. 2 is the sample photo obtained.

Gained sample is heat-treated and is characterized:

Sample embodiment 1 prepared carries out 450 DEG C respectively, 800 DEG C, 1000 DEG C, 1100 DEG C of heat treatments, carries out TEM sign to the sample after process.Fig. 3 is the TEM figure of sample.Sample interior particle has good crystallinity, and particle size is less, is evenly distributed on disordered state silica inner.Along with temperature raises, crystallite dimension has small size increase, and when temperature is elevated to 1000 DEG C, crystallite dimension is still less than 10nm.When temperature is increased to 1100 DEG C, portion crystal increases, and has the defect having obvious silica to cause between portion crystal to exist simultaneously.

XRD test is carried out by after the sample for the treatment of of different temperature respectively pulverize.Fig. 4 is test result.Sample through the drying of HTHP supercritical fluid is Anatase, and crystallite dimension is about 7nm, conforms to TEM test result.450 DEG C of remaining organic processes of heat treatment removing do not cause obvious impact to sample crystallinity.Along with temperature raises, sample crystallinity strengthens, but until after 1100 DEG C of process, titanium dioxide is still Anatase, and can calculate according to Scherrer formula and learn that its average grain size is 11nm, sample does not occur that Rutile Type changes.

Sample through heat treatments at different is carried out nitrogen adsorption desorption specific area and pore-size distribution is tested.Table 1 is test result.By BET method calculation sample specific area, the sample specific area obtained through 450 DEG C of process is 192.3m ²/ g, along with temperature raises, specific area has decline, and after 1100 DEG C of process, sample does not sinter, and specific area is 43.9m ²/ g.By BJH method calculation sample average pore size, show that aperture reduces gradually along with temperature raises, after 1100 DEG C of process, aperture drops to 12.4nm by 18.3nm.

Table 1. nitrogen adsorption desorption specific area/opening size test result

Characterization of Its Photocatalytic Activity is carried out to the sample through heat treatments at different.Concrete grammar is: the aqueous solution of methylene blue of configuration 20mg/L is as light degradation material.10mg sample is put into and gets 40ml methylene blue solution, in the dark state centrifugal survey solution absorption spectra after stirring 30min; To materials after uv-exposure centrifugal survey solution absorption spectra, survey once every 20min.Fig. 5 is test result.800 DEG C of heat treated samples have the highest photocatalytic activity, and after 20 minutes uv-exposures, methylene blue concentration drops to 31%, and after 100 min, catalytic degradation completes substantially.1000 DEG C and 1100 DEG C of degradation rates basically identical, after 20 min, concentration reduces to 40%.Photocatalysis material of titanium dioxide the most conventional on market is P25, and after tested, under identical condition, after 20min uv-exposure, methylene blue concentration is 46%.Therefore, with TiO prepared by the method ₂-SiO ₂composite photocatalyst material catalytic performance after 1100 DEG C of heat treatment, still higher than P25, has good high-temperature stability and photocatalytic activity.

embodiment 4: 6 ml tetraethyl orthosilicates are dissolved in 84 ml ethanol by the content reducing further silica in aeroge, and it is even to add 1.5 ml deionized water and stirring.Slowly add 36ml butyl titanate in this solution, now adularescent floccule produces, Keep agitation 20 min, and floccule dissolves.Add 1.25ml hydrofluoric acid solution again, after stirring, obtain clear sol, then above-mentioned colloidal sol is left standstill and treat its gel.After gel, carry out aging, replace, supercritical drying, obtains aeroge sample.

Fig. 6 is gained aeroge sample photo, in fluffy white powder shape.

Claims (1)

1. one kind has the Anatase TiO of 1100 DEG C of high-temperature stabilities ₂the preparation method of catalysis material, is characterized in that concrete steps are as follows:

(1) 6ml tetraethyl orthosilicate is dissolved in absolute ethyl alcohol, adds deionized water and stirring evenly, obtain clarifying mixed solution;

(2) slowly add in above-mentioned solution by 1-36ml tetra-n-butyl titanate, adularescent floccule produces at once, this product be hydrolyzed rapidly for butyl titanate chance water; Wherein, reagent volume ratio is butyl titanate: ethyl orthosilicate: water: hydrofluoric acid=(1-36) ml:6ml:1.5ml:1.25ml, etoh solvent volume be ethyl orthosilicate and butyl titanate volume and twice;

(3) Keep agitation 20 min, floccule dissolves, and adds hydrofluoric acid solution as catalyst, obtains clear sol after stirring;

(4) by clear sol sealing and standing, its gel is treated; Silica is formed coated to titanium oxide, hinder the grain growth of titanium oxide in drying and heat treatment process, serves important function to suppression crystal transition;

(5) continue after gel-forming to leave standstill aging 18-24 hour, then carry out solvent replacement with ethanol, removing excessive moisture and impurity;

(6) carry out HTHP ethanol supercritical drying after having replaced, temperature is 300 DEG C, and the most promotion of pressure is to 12MPa, and high-temperature supercritical improves titania meterial crystallinity, to suppress crystal transition under its high temperature further.