CN104549193B - A kind of low-density TiO2/SiO2Complex microsphere and preparation method thereof - Google Patents

Abstract

The invention belongs to technical field prepared by inorganic functional material, particularly to a kind of low-density TiO₂/SiO₂Microsphere and synthetic technology thereof. With tetra-n-butyl titanate and tetraethyl orthosilicate for raw material, prepare O/W type emulsion system, by emulsion system is carried out hydrothermal treatment consists, synthesized the SiO with nucleocapsid structure₂/TiO₂Complex microsphere, the shell of this microsphere is SiO₂With TiO₂Complex, kernel is TiO₂. In water-heat process, tetraethyl orthosilicate adsorbs and quickly occurs hydrolysis in the outer layer of dispersed oil droplets, form the spherical shell layer of some strength, and the formation of this shell inhibits the volume contraction that internal tetra-n-butyl titanate produces because of hydrolysis and polycondensation reaction. By control tetraethyl orthosilicate addition, the shell control ability to microspheres shrink can be regulated and controled continuously, thus the inner structural features of complex microsphere include specific surface area, hole diameter, pore volume etc. all can obtain tuning control.

Description

A kind of low-density TiO2/SiO2 composite microsphere and its preparation method

technical field

The invention belongs to the technical field of preparation of inorganic functional materials, and in particular relates to a low-density TiO ₂ /SiO ₂ microsphere and its synthesis technology.

Background technique

TiO ₂ semiconductor has the advantages of stable physical and chemical properties, abundant raw material sources, non-toxicity and high photocatalytic activity, which make it widely studied as a photocatalyst in the field of environmental purification. The existing forms of TiO ₂ are amorphous, anatase, brookite and rutile. Among them, the amorphous form is generally considered to have no catalytic activity, and the brookite form is seldom used due to the difficulty in preparing pure single crystal products. According to research, anatase is a crystalline state with higher photocatalytic activity. In addition to crystal form, particle size also affects the activity of _TiO2 . TiO ₂ particles with a large size have high photocatalytic activity, but there are problems such as difficulty in separation and recovery, and easy loss during use. Preparation of TiO ₂ microspheres with low density and random network structure with holes in size can solve this problem well. The specific surface area, pore diameter and pore volume of the porous TiO ₂ microspheres directly affect the photocatalytic efficiency of the product. High specific surface area and pore volume have relatively abundant reactive sites, and are conducive to the adsorption and enrichment of low-concentration organic molecules to be degraded in the environment, thereby improving the photocatalytic efficiency of the product.

The sol-gel process utilizing titanium alkoxide hydrolysis and polycondensation reactions is a common method for preparing _TiO2 photocatalysts. In order to obtain an ideal microstructure, the specific surface area and porosity of the product can be improved by adding surfactants or polymers to the raw materials, and then removing the additives by high-temperature calcination. The present invention proposes a novel synthesis idea, adopts a one-step hydrothermal process, utilizes the compound shell layer formed in advance to control the shrinkage of the internal gel, and realizes the self-intelligent regulation of the internal structure of the TiO ₂ microsphere.

Contents of the invention

The object of the present invention is to: provide a kind of low density, high specific surface area TiO ₂ /SiO ₂ composite microspheres and its synthesis method,

The low-density TiO ₂ /SiO ₂ composite microspheres provided by the present invention are synthesized by:

Firstly, the complex of tetra-n-butyl titanate is prepared. Since tetra-n-butyl titanate has high hydrolysis activity, it can be rapidly hydrolyzed to form TiO ₂ when it encounters water, so acetylacetone is used for complexation to ease its hydrolysis rate; secondly, Prepare an O/W emulsion system, use tetra-n-butyl titanate complex as the oil dispersed phase, deionized water as the continuous phase, and dodecylbenzenesulfonic acid as the interface stabilizer to prepare the O/W emulsion system , thirdly, the intervention of Si source, adding a certain amount of ethyl orthosilicate and ethanol to the dispersion system, the addition of ethyl orthosilicate, on the one hand, aims to obtain TiO ₂ /SiO ₂ composite microspheres, on the other hand The purpose is to use the adsorption and hydrolysis reaction of ethyl orthosilicate on the surface of oil droplets to form a spherical shell with a certain strength, so as to inhibit the volume shrinkage caused by the hydrolysis of tetra-n-butyl titanate inside, and finally obtain low-density TiO ₂ composite microspheres , the use of ethanol aims to improve the compatibility of tetraethyl orthosilicate with water; fourth, hydrothermal treatment, the prepared O/W dispersion system is transferred to a high-pressure reactor, and the hydrothermal reaction is carried out at 150°C TiO ₂ /SiO ₂ composite microspheres can be obtained in 10 hours.

The specific operation is:

(1) dodecylbenzenesulfonic acid is dissolved in deionized water, is mixed with dodecylbenzenesulfonic acid solution,

Wherein, the concentration of the prepared dodecylbenzenesulfonic acid solution is 90mg/L;

(2) complexing tetra-n-butyl titanate with acetylacetone to obtain a tetra-n-butyl titanate complex;

(3) adding the tetra-n-butyl titanate complex obtained in step (2) to the dodecylbenzenesulfonic acid solution obtained in step (1), and stirring evenly to obtain an aqueous dispersion system;

(4) In the aqueous dispersion system obtained in step (3), add a certain proportion of ethyl orthosilicate and ethanol, and stir evenly to obtain a reaction system, which is the "O/W" mentioned in the following examples. type dispersed system";

(5) The reaction system obtained in step (4) was hydrothermally reacted at 150° C. for 10 h, and the reaction product was centrifuged, washed, and dried to obtain low-density TiO ₂ /SiO ₂ composite microspheres,

Wherein, the reaction product was washed in the order of "washing with deionized water and washing with ethanol", and the operation of "drying" was drying at 60° C. for 6 hours.

In the present invention, the low-density TiO ₂ /SiO ₂ composite microspheres prepared by the above scheme have a core-shell structure, the spherical shell layer is TiO ₂ /SiO ₂ composite, and the inner core is TiO ₂ . The TiO ₂ /SiO ₂ composite microspheres The pore volume of the ball is 0.33-0.63cm ³ ·g ^-1 , the specific surface area of the microsphere is 214-293m ² ·g ^-1 , and the average pore diameter is 5.7-12nm.

The above-mentioned composite microspheres are synthesized through a one-step hydrothermal reaction to the aqueous dispersion system, and the substantial increase in the volume of the internal pores of the microspheres is achieved based on the inhibition of the spherical shell on the internal volume shrinkage of the sphere during the hydrothermal reaction process; The change of pore diameter and pore volume inside the composite microspheres is regulated by the compounding amount of SiO ₂ .

The synthesis method and the synthesized TiO ₂ /SiO ₂ composite microspheres have the following characteristics:

(1) O/W type emulsion system is adopted: water is used as the continuous phase, the preparation cost of microspheres is low, and the load on the environment is small;

(2) Through a one-step hydrothermal process, composite microspheres with a core-shell structure are obtained: using the difference in surface tension between tetra-n-butyl titanate complex and tetra-n-titanate Adsorption on the surface of butyl ester complex oil droplets, through the hydrothermal process, to obtain composite microspheres with core-shell structure;

(3) The composite microsphere has an extremely low apparent density. Due to the difference in hydrolysis activity between tetra-n-butyl titanate complex and ethyl orthosilicate, ethyl orthosilicate is first formed in the outer layer by hydrolysis and has a certain strength. The spherical shell gel formed by the spherical shell inhibits the volume shrinkage of the internal tetra-n-butyl titanate due to hydrolysis, so that a large number of size voids are formed inside the microspheres;

(4) The shell of the microsphere is not pure SiO ₂ , but a composite of SiO ₂ and TiO ₂ . Under hydrothermal conditions, not only tetra-n-butyl titanate undergoes hydrolysis reaction, but the The complex also produces hydrolysis and polycondensation reactions, but the hydrolysis reaction activity of ethyl orthosilicate is higher, so the formed spherical shell is a compound of SiO ₂ and TiO ₂ ;

(5) By changing the compounding amount of SiO ₂ , that is, adjusting the addition amount of tetraethyl orthosilicate, the thickness of the shell layer of the microsphere can be changed, and the ability of the shell layer to control the shape and volume of the microsphere can be adjusted, thereby obtaining a series of different Microspheres with apparent density, the void volume of the microspheres can reach up to 71% (calculated based on the theoretical density of pure anatase TiO ₂ of 3.89g cm ^-3 );

(6) Adopt SiO ₂ composite, improve the specific surface area of product while improving microsphere porosity, increase to 293m ² /g from 193m ² /g of pure TiO ₂ (SiO ₂ composite amount is 30% (when feeding , Si accounts for the molar percentage of Ti, Si total amount));

(7) The compounding of SiO ₂ can increase the acidic site of TiO ₂ photocatalyst, thereby enhancing the photocatalytic performance of the product. The isoelectric points of TiO ₂ and SiO ₂ are about pH=6.3 and pH=3.0, respectively, so composite microspheres are particularly Suitable for the adsorption of a large number of positively charged organic positive ions in a neutral solution environment;

(8) The agglomeration of the grains is weak, and the agglomeration of the grains will seriously affect the performance of the product, including photocatalytic activity, high surface area and pore volume fraction of the composite microspheres, indicating that the agglomeration of the TiO ₂ grains is compounded by SiO ₂ Significantly weakened.

Description of drawings

Fig. 1 is prepared by embodiment 1～4, and SiO ₂ composite amounts are respectively 0, 10%, 20% and 30% (here " 0, 10%, 20%, 30% " refers to feeding intake, Si accounts for The mole percent of Ti, Si total amount, the same below) of TiO ₂ /SiO The FESEM or SEM photo of the composite microspheres, with pure _{TiO 2 microspheres} (the corresponding product of embodiment 1) compared, the surface of the composite microspheres is comparatively rough;

Fig. 2 is prepared in embodiment 3, SiO ₂ composite amount is 20% _{TiO 2} /SiO TEM photo of composite microspheres (before TEM analysis, the sample is processed 2h through the hydrochloric acid of solute mass fraction 18%.), the The analysis results showed that the composite microspheres had a core-shell structure;

Fig. 3 is prepared by embodiment 1～4, and SiO ₂ composite amounts are respectively 0, 10%, 20% and 30% TiO ₂ /SiO ₂ composite microspheres N ₂ isothermal adsorption results, the analysis results show that when When the SiO ₂ composite content is 20%, the composite microspheres have the largest N ₂ adsorption volume;

Fig. 4 is the preparation of embodiment 1～4, and SiO ₂ composite amounts are respectively 0, 10%, 20% and 30% _{TiO 2} /SiO The comparison of pore volume, average pore diameter and specific surface area of microspheres, the The analysis results show that compared with the pure TiO ₂ microspheres, the specific surface area of the composite microspheres with SiO ₂ compounding content of 20% increases slightly, but the pore volume and average pore diameter increase by about 100% respectively;

Fig. 5 is the sample prepared in embodiment 1 and embodiment 3, i.e. pure _TiO Microsphere and SiO The XPS elemental analysis (O1s and Si2p) of the composite microsphere of ₂₀ % composite amount, this analytical result shows, by this method The process route adopted by the invention, SiO ₂ has been successfully compounded on TiO ₂ microspheres,

When preparing the sample of Example 3, tetra-n-butyl titanate and tetraethyl orthosilicate were added according to the atomic number ratio of Ti and Si at 4:1, and by electron probe (EPMA) and X-ray photoelectron spectroscopy (XPS) The detected atomic ratios of Ti to Si are 5.6:1 and 1.1:1, respectively. Among them, the signal response volume of EPMA is about 1 μm ³ , while XPS is a surface analysis technique, and its analysis depth is only a few atomic layers thick. Therefore, the above analysis results show that Si elements are mainly concentrated in the shell of the microsphere.

detailed description

Example 1:

1. Complexation of tetra-n-butyl titanate

Add 2.0 mL of acetylacetone to 5.0 mL of tetra-n-butyl titanate, and stir for 0.5 h to obtain a complex of tetra-n-butyl titanate.

2. Preparation of O/W dispersion system

While stirring, disperse the tetra-n-butyl titanate complex obtained in Step 1 into 40 mL, 90 mg/L aqueous solution of dodecylbenzenesulfonic acid, and after stirring for 1 h, a uniform milky yellow dispersion system was obtained.

3. Hydrothermal treatment

Transfer the O/W dispersion system obtained in step 2 into a high-pressure reactor with a polytetrafluoroethylene inner cup, and conduct a hydrothermal reaction at 150° C. for 10 h.

4. Separation, washing and drying

The product obtained from the reaction in Step 3 was centrifuged, washed with deionized water and ethanol in sequence, and the washed sample was dried at 60° C. for 6 hours.

The pore volume of the TiO ₂ microspheres prepared in this example is 0.29 cm ³ ·g ^-1 , the specific surface area of the microspheres is 193 m ² ·g ^-1 , the average pore diameter is 5.6 nm, and the relative density is 47% (based on pure The theoretical density of anatase TiO ₂ is 3.89g·cm ^-3 as a benchmark).

Example 2:

1. Complexation of tetra-n-butyl titanate

Add 2.0 mL of acetylacetone to 5.0 mL of tetra-n-butyl titanate, and stir for 0.5 h to obtain a complex of tetra-n-butyl titanate.

2. Preparation of O/W dispersion system

While stirring, disperse the tetra-n-butyl titanate complex obtained in Step 1 into 40 mL, 90 mg/L aqueous solution of dodecylbenzenesulfonic acid, and after stirring for 1 hour, a uniform milky yellow dispersion system is obtained. Then, 0.34 mL of ethyl orthosilicate and 1.7 mL of ethanol were added to the system, and the stirring was continued for 30 min.

3. Hydrothermal treatment

Transfer the O/W dispersion system obtained in step 2 into a high-pressure reactor with a polytetrafluoroethylene inner cup, and conduct a hydrothermal reaction at 150° C. for 10 h.

4. Separation, washing and drying

The product obtained from the reaction in Step 3 was centrifuged, washed with deionized water and ethanol in sequence, and the washed sample was dried at 60° C. for 6 hours.

The pore volume of the TiO ₂ /SiO ₂ composite microspheres prepared in this example is 0.33 cm ³ ·g ^-1 , the specific surface area of the microspheres is 216 m ² ·g ^-1 , the average pore diameter is 5.7 nm, and the relative density is 44% (based on the theoretical density of 3.89g·cm ^-3 of pure anatase TiO ₂ ).

Example 3:

1. Complexation of tetra-n-butyl titanate

Add 2.0 mL of acetylacetone to 5.0 mL of tetra-n-butyl titanate, and stir for 0.5 h to obtain a complex of tetra-n-butyl titanate.

2. Preparation of O/W dispersion system

While stirring, disperse the tetra-n-butyl titanate complex obtained in Step 1 into 40 mL, 90 mg/L aqueous solution of dodecylbenzenesulfonic acid, and after stirring for 1 hour, a uniform milky yellow dispersion system is obtained. Add 0.76 mL of ethyl orthosilicate and 1.7 mL of ethanol to the system, and continue stirring for 30 min.

3. Hydrothermal treatment

Transfer the O/W dispersion system obtained in step 2 into a high-pressure reactor with a polytetrafluoroethylene inner cup, and conduct a hydrothermal reaction at 150° C. for 10 h.

4. Separation, washing and drying

The product obtained from the reaction in Step 3 was centrifuged, washed with deionized water and ethanol in sequence, and the washed sample was dried at 60° C. for 6 hours.

The pore volume of the TiO ₂ /SiO ₂ composite microspheres prepared in this example is 0.63 cm ³ ·g ^-1 , the specific surface area of the microspheres is 214 m ² ·g ^-1 , the average pore diameter is 12 nm, and the relative density is 29 % (Based on the theoretical density of pure anatase TiO ₂ of 3.89 g·cm ^-3 ).

Example 4:

1. Complexation of tetra-n-butyl titanate

Add 2.0 mL of acetylacetone to 5.0 mL of tetra-n-butyl titanate, and stir for 0.5 h to obtain a complex of tetra-n-butyl titanate.

2. Preparation of O/W dispersion system

While stirring, disperse the tetra-n-butyl titanate complex obtained in Step 1 into 40 mL, 90 mg/L aqueous solution of dodecylbenzenesulfonic acid, and after stirring for 1 hour, a uniform milky yellow dispersion system is obtained. Then, 1.31 mL of ethyl orthosilicate and 1.7 mL of ethanol were added to the system, and the stirring was continued for 30 min.

3. Hydrothermal treatment

Transfer the O/W dispersion system obtained in step 2 into a high-pressure reactor with a polytetrafluoroethylene inner cup, and conduct a hydrothermal reaction at 150° C. for 10 h.

4. Separation, washing and drying

The product obtained from the reaction in Step 3 was centrifuged, washed with deionized water and ethanol in sequence, and the washed sample was dried at 60° C. for 6 hours.

The pore volume of the TiO ₂ /SiO ₂ composite microspheres prepared in this example is 0.45 cm ³ ·g ^-1 , the specific surface area of the microspheres is 293 m ² ·g ^-1 , the average pore diameter is 6.9 nm, and the relative density is 36% (based on the theoretical density of 3.89g·cm ^-3 of pure anatase TiO ₂ ).

Example 5:

In the present invention, complexing tetra-n-butyl titanate with acetylacetone in advance is the basis for forming O/W dispersion system and synthesizing TiO ₂ /SiO ₂ composite microspheres.

For comparison, in Example 5, 5 mL of uncomplexed tetra-n-butyl titanate was directly dispersed into 40 mL of 90 mg/L aqueous solution of dodecylbenzenesulfonic acid while stirring. Due to the rapid hydrolysis of tetra-n-butyl titanate, a large number of TiO ₂ particles are formed in the system immediately, so a stable O/W dispersion system cannot be formed, and TiO ₂ /SiO ₂ composite microspheres cannot be successfully synthesized.

Claims (5)

1. a low-density TiO₂/SiO₂Complex microsphere, it is characterised in that: described microsphere has nucleocapsid structure, and its spherical shell layer is TiO₂/SiO₂Complex, kernel is TiO₂,

Described TiO₂/SiO₂The pore volume of complex microsphere is 0.33 0.63cm³��g^-1, specific surface area is 214 293m²��g^-1, average pore size is 5.7 12nm.

2. low-density TiO as claimed in claim 1₂/SiO₂The preparation method of complex microsphere, it is characterised in that: described preparation method is,

(1) DBSA is dissolved in deionized water, is configured to dodecylbenzenesulfonic acid solution;

(2) tetra-n-butyl titanate and acetylacetone,2,4-pentanedione are carried out complexation, obtain tetra-n-butyl titanate complex;

(3) the tetra-n-butyl titanate complex obtained in step (2) is joined in the dodecylbenzenesulfonic acid solution obtained in step (1), be uniformly mixing to obtain dispersion system;

(4) dispersion system obtained in step (3) adds tetraethyl orthosilicate and ethanol, and stir, obtain reaction system;

(5) by the reaction system that obtains in step (4) under 150 DEG C of conditions, hydro-thermal reaction 10h, by product centrifugation, washing, dry, obtain low-density TiO₂/SiO₂Complex microsphere.

3. low-density TiO as claimed in claim 2₂/SiO₂The preparation method of complex microsphere, it is characterised in that: the concentration of the dodecylbenzenesulfonic acid solution described in step (1) is 90mg/L.

4. low-density TiO as claimed in claim 2₂/SiO₂The preparation method of complex microsphere, it is characterised in that: the washing described in step (5) is, according to the order of " deionized water wash, washing with alcohol ", described product is washed.

5. low-density TiO as claimed in claim 2₂/SiO₂The preparation method of complex microsphere, it is characterised in that: drying described in step (5) is, dry 6h at 60 DEG C.