CN1686821A - Method for preparing medium pore molecular sieve of titanium dioxide - Google Patents

Abstract

The invention relates to a preparation method of nano titanium dioxide mesoporous material. It is characterized in that it includes the following steps: mixing the titanium source and triethanolamine at room temperature, stirring evenly, and then dropwise adding one of water, glycerol, ethylene glycol, and ethanol as a solvent, wherein the molar ratio of Ti in the titanium source to triethanolamine is Between 1:0.2 and 1:5, the ratio of Ti and solvent in the titanium source is between 1:4 and 1:100; adjust the pH value between 7 and 9; dry at 25°C to 180°C for 2 to 48 hours After solidification, a homogeneous gel is formed, and then the gel is moved into a closed pressure-resistant reactor and crystallized at a temperature of 25°C to 180°C for 12 to 96 hours; the temperature is raised to 300 to 300 at a speed of 1°C to 10°C/min 800°C, heat preservation for 10-20 hours, or extract with alcohol solution for 24-72 hours, and grind to obtain titanium dioxide mesoporous molecular sieves. The invention reduces the cost and has simple process; the crystal form of the titanium dioxide mesoporous molecular sieve is controllable, the pore size can be controlled to be 5-25nm in diameter, the crystal grain size is about 20nm, and the photocatalytic activity is improved.

Description

Preparation method of titanium dioxide mesoporous molecular sieve

technical field

The invention relates to a preparation method of titanium dioxide material, in particular to a preparation method of nanometer titanium dioxide mesoporous material.

Background technique

Porous materials have a wide range of applications in catalytic separation and other fields. Compared with classical microporous molecular sieves, mesoporous molecular sieves have larger pore size and specific surface area. As catalysts or catalyst supports, mesoporous molecular sieve materials provide favorable spatial configuration and type-selective active centers for organic macromolecules to participate in reactions, and have potential application advantages in petroleum processing or fine chemical industry.

Transition metal oxides have special properties, and transition metal oxides with various mesoporous structures have received unprecedented attention in recent years. Titanium dioxide is a non-toxic and harmless semiconductor. It can generate photogenerated holes and photogenerated electrons under the irradiation of ultraviolet and visible wavelengths, and has good corrosion resistance. It has broad applications in photocatalysis, photodegradation and environmental protection. prospect. There are many preparation methods for titanium dioxide mesoporous molecular sieves. The templates used include polymer block copolymers, cationic surfactants such as dodecyltrimethylammonium bromide, long-chain alkylamine surfactants, etc. It is synthesized in alcohol solution or aqueous solution by precipitation method, hydrothermal synthesis method, sol-gel method, etc. Generally speaking, in the synthesis process, most of the mesoporous molecular sieves are prepared by changing different surfactants as templates or changing the synthesis method. The common problems of these methods are as follows:

1. Surfactant or small organic molecule itself is expensive.

2. Most surfactants or small organic molecules are highly toxic.

3. The preparation process is complicated, the conditions affecting the reaction are increased, and the difficulty of controlling the synthesis process is increased.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for synthesizing nano-titanium dioxide mesoporous molecular sieve, which has the advantages of simple synthesis process and low cost, and the prepared titanium dioxide mesoporous molecular sieve has controllable crystal form, controllable pore size, and crystal particle size in the range of About 20nm, high photocatalytic activity.

Embodiments of the present invention are described in detail below:

Titanium dioxide mesoporous molecular sieves were synthesized in aqueous solution or organic solution by sol-gel method with triethanolamine as template and titanium source as tetrabutyl titanate, isopropyl titanate or titanium tetrachloride.

The invention provides a method for preparing titanium dioxide mesoporous molecular sieve, which is characterized in that it comprises the following steps:

(1) Mix the titanium source, i.e. tetrabutyl titanate, isopropyl titanate or titanium tetrachloride, with triethanolamine at room temperature, stir well and add water, glycerol, ethylene glycol, One of ethanol as a solvent, wherein the molar ratio of Ti in the titanium source to triethanolamine is between 1:0.2 and 1:5, and Ti in the titanium source and one of water, glycerol, ethylene glycol, and ethanol The molar ratio is between 1:4 and 1:100;

(2) adjust the pH value between 7 and 9, and continue to stir to obtain a homogeneous mixture;

(3) Dry the above-mentioned homogeneous mixture at 25°C to 180°C for 2 to 48 hours and solidify to form a homogeneous gel, then transfer the gel into a closed pressure-resistant reactor and crystallize at 25°C to 180°C for 12 hours ~96 hours, block gel was obtained;

(4) Heat the above-mentioned block gel to 300-800°C at a speed of 1°C-10°C/min, and keep it warm for 10-20 hours to form a powder, namely titanium dioxide mesoporous molecular sieve or extract the above-mentioned block with alcohol solution for 24-72 hours Gel, titanium dioxide mesoporous molecular sieves are also obtained after grinding.

The ratio of titanium source to triethanolamine is 1:0.2 to 1:5, preferably 1:1 to 1:3; the ratio of titanium source to water or glycerol or ethylene glycol or ethanol is 1:4 ~1:100, preferably 1:10~1:40.

The calcination of the above step (4) can control the crystal form of the titanium dioxide skeleton by controlling the calcination temperature so that the crystal forms of the titanium dioxide mesoporous molecular sieve are anatase, rutile, or mixed crystals of anatase and rutile. The anatase phase is obtained by roasting at a temperature below 450°C, the mixed crystal is obtained by roasting at a temperature of 450°C to 700°C, and the rutile phase is formed at a temperature above 700°C.

The extraction method in the above step (4) removes the template agent to obtain mesoporous molecular sieves, and the XRD results show that it is titanium dioxide nanocrystals, and its photocatalytic effect is significantly improved in the visible light range, and its ultraviolet absorption rate is compared with ordinary titanium dioxide powder. The results are shown in Figure 5 , and the results for photocatalytic degradation of formaldehyde are shown in Fig. 6. The following table is a list of samples used in photocatalytic experiments:

serial number name origin level Remark 1 Titanium dioxide Tianjin Fuchen Chemical Reagent Factory Analytical pure 2 Titanium dioxide German GESSUGA company Analytical pure Model: P25 3 Titanium dioxide mesoporous molecular sieve self made

The salient features of the titanium dioxide mesoporous molecular sieve provided by the present invention:

1. Using triethanolamine as a template to synthesize titanium dioxide mesoporous molecular sieves greatly reduces the cost of preparation and makes the preparation process simple.

2. The crystal form of the obtained titanium dioxide mesoporous molecular sieve is controllable, the pore size is controllable so that the pore diameter is between 5 and 25 nm, and the crystal particle size is about 20 nm.

3. The photocatalytic activity of the obtained titanium dioxide material is improved.

Description of drawings

Fig. 1 is an XRD diffraction pattern of a titanium dioxide mesoporous molecular sieve.

Fig. 2 is a pore size distribution diagram of titanium dioxide mesoporous molecular sieves. Among them, figure a is a pore size distribution diagram with an average pore diameter of 23.03741nm, and figure b is a pore size distribution diagram with an average pore diameter of 8.41103nm.

Figure 3 is the XRD diffraction pattern of different crystal forms of titanium dioxide mesoporous molecular sieves, in which Figure a is the anatase phase, Figure b is the mixed crystal anatase phase content of 58.3% and the rutile phase content is 41.7%, and Figure c is the rutile phase.

Fig. 4 is a scanning electron microscope image of a titanium dioxide mesoporous molecular sieve.

Fig. 5 is a comparison chart of ultraviolet absorption rates between different titanium dioxide and titanium dioxide mesoporous molecular sieves.

Fig. 6 is a comparison chart of the results of photocatalytic degradation of formaldehyde between different titanium dioxide and titanium dioxide mesoporous molecular sieves.

Detailed ways

The following examples further illustrate the implementation and effect

Example 1

Mix 12ml tetrabutyl titanate and 4.7ml triethanolamine at room temperature, stir evenly, add 16ml water dropwise and measure the pH value to 8, continue stirring to obtain a homogeneous mixture, dry the above homogeneous mixture at 100°C for 12 hours and then solidify A homogeneous gel is formed, and then the gel is moved into a reaction kettle and crystallized at 150°C for 12 hours to obtain a block gel, and then the above product is calcined at a rate of 1°C/min to 600°C, After heat preservation for 10 hours, a white powder was obtained by grinding, the XRD diffraction pattern of which is shown in Figure 1, and the pore size distribution is shown in Figure 2a.

Example 2

Mix 12ml tetrabutyl titanate and 4.7ml triethanolamine at room temperature, stir evenly, add 16ml water dropwise and measure the pH value to 8, continue stirring to obtain a homogeneous mixture, dry the above homogeneous mixture at 100°C for 12 hours and then solidify A homogeneous gel was formed, and then the gel was transferred into a reaction kettle for crystallization at a temperature of 150° C. for 48 hours to obtain a block gel that was equally divided into three parts. The extracts were extracted with a Soxhlet extractor for 24 hours, 48 hours, and 72 hours, respectively, and the extracts were ethanol solutions. The obtained massive gel was ground into powder, and the pore size distribution of the products obtained by extraction for 24 hours was shown in Figure 2b.

Example 3

Mix 3.4ml tetrabutyl titanate and 6.7ml triethanolamine at room temperature, stir evenly, add 18ml water dropwise and measure the pH value to be 8, continue stirring to obtain a homogeneous mixture, dry the above homogeneous mixture at 180°C for 2 hours Solidify to form a homogeneous gel, then move the gel into the reaction kettle and crystallize at 180°C for 48 hours to obtain a block gel; then heat the above product at a rate of 5°C/min to 400°C after calcination , kept warm for 10 hours, and ground to obtain a white powder. Its XRD diffraction pattern is shown in Figure 3a.

Example 4

Mix 15ml of isopropyl titanate and 1.33ml of triethanolamine at room temperature, stir evenly, add 9ml of water dropwise, add 5ml/L ammonia water drop by drop to adjust the pH value to 9, continue stirring, and the mixture is layered to obtain a condensate glue. Dry the above-mentioned homogeneous mixture at 25°C for 48 hours, then transfer it to a reaction kettle and crystallize at 90°C for 96 hours to obtain a block gel; then heat the above-mentioned product at a rate of 10°C/min to 600°C for calcination, and keep it warm for 20 After grinding for 1 hour, a light yellow powder was obtained. Its XRD diffraction pattern is shown in Figure 3b.

Example 5

Mix 4ml tetrabutyl titanate and 1.6ml triethanolamine at room temperature, stir evenly, add 2.2ml ethylene glycol dropwise and measure the pH value to 8, continue stirring to obtain a homogeneous mixture, dry the above homogeneous mixture at 60°C for 10 A gel was formed after 1 hour, and then moved into a reaction kettle for crystallization at 25°C for 24 hours, then the above product was calcined at a rate of 1°C/min to 800°C, kept for 10 hours, and ground to obtain a light yellow powder. Its XRD diffraction pattern is shown in Fig. 3c.

Example 6

Mix 1.1ml titanium tetrachloride and 4ml triethanolamine at room temperature, stir evenly, add 23.3ml ethanol dropwise, add 5ml/L hydrochloric acid dropwise to adjust the pH value to 7, continue stirring, and the mixture is layered to obtain a condensate glue. Dry the above-mentioned homogeneous mixture at 100°C for 12 hours, then transfer it to a reaction kettle and crystallize at 150°C for 12 hours to obtain a block gel; then heat the above-mentioned product at a rate of 1°C/min to 300°C for calcination, and keep it warm for 15 Hours, grinding to obtain white powder, its crystal particle size can be found out at about 20nm by the scanning electron microscope picture of Fig. 4.

Example 7

Mix 4ml tetrabutyl titanate and 1.6ml triethanolamine at room temperature, stir evenly, add 3ml glycerol dropwise and measure the pH value to 8, continue stirring to obtain a homogeneous mixture, and dry the above homogeneous mixture at 100°C for 12 hours After forming a gel, then move it into a reaction kettle and crystallize at 150°C for 48 hours, then heat the above product at a rate of 1°C/min to 600°C for calcination, keep it warm for 10 hours, and grind to obtain a light yellow powder. The comparison results of the catalytic effect with ordinary titanium dioxide powder are shown in Figure 5 and Figure 6.

Claims (3)

1. A method for preparing titanium dioxide mesoporous molecular sieves, comprising the following steps: (1) Mix the titanium source, i.e. tetrabutyl titanate, isopropyl titanate or titanium tetrachloride, with triethanolamine at room temperature, stir well and add water, glycerol, ethylene glycol, One of ethanol as a solvent, wherein the molar ratio of Ti in the titanium source to triethanolamine is between 1:0.2 and 1:5, and Ti in the titanium source and one of water, glycerol, ethylene glycol, and ethanol The molar ratio is between 1:4 and 1:100; (2) adjust the pH value between 7 and 9, and continue to stir to obtain a homogeneous mixture; (3) Dry the above-mentioned homogeneous mixture at 25°C to 180°C for 2 to 48 hours and solidify to form a homogeneous gel, then transfer the gel into a closed pressure-resistant reactor and crystallize at 25°C to 180°C for 12 hours ~96 hours, block gel was obtained; (4) Heat the above-mentioned block gel to 300-800°C at a speed of 1°C-10°C/min, and keep it warm for 10-20 hours to form a powder, namely titanium dioxide mesoporous molecular sieve or extract the above-mentioned block with alcohol solution for 24-72 hours Gel, titanium dioxide mesoporous molecular sieves are also obtained after grinding. 2. The preparation method of titanium dioxide mesoporous molecular sieve according to claim 1, characterized in that the ratio of titanium source to triethanolamine is 1:1-1:3. 3. The preparation method of titanium dioxide mesoporous molecular sieve according to claim 1, characterized in that the ratio of titanium source to water or glycerol or ethylene glycol or ethanol is 1:10-1:40.

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