CN102350330A - Mixed-phase titania photocatalyst and its preparation method - Google Patents

Abstract

The invention provides a mixed crystal titanium dioxide photocatalyst. It includes titanium dioxide powder particles, and the titanium dioxide powder particles are a mixture of two or more different crystal forms of titanium dioxide. Through the above technical proposal, the photocatalytic effect of the present invention is significantly improved. The present invention also provides a preparation method for the above mixed crystal titanium dioxide photocatalyst, which includes the following steps: 1) Mixing different titanium dioxide (crystal form A and crystal form B) in a dispersant solvent at room temperature, crystal form A and crystal form The mass ratio of type B is 1-100; 2) Ultrasonic dispersion for 10-60 minutes; 3) Continue stirring for 0.5-2 hours; 4) After removing the solvent, calcining at 200-600°C for 0.5-4 hours to obtain mixed crystal titanium dioxide catalyst of light. The raw materials used in the method are low in cost, simple in equipment and easy to operate; compared with single crystal titanium dioxide, the obtained photocatalyst has significantly improved ultraviolet photocatalytic activity.

Description

A kind of mixed crystal titanium dioxide photocatalyst and preparation method thereof

technical field

The invention relates to a nano-titanium dioxide catalyst and a preparation method thereof, belonging to the field of catalytic technology, and more specifically, the invention provides a method for preparing a mixed-crystal titanium dioxide nano-powder photocatalyst with high catalytic activity and improving the activity of the mixed-crystal catalyst Methods.

Background technique

With the prevalence of "low carbon" today, energy shortage and environmental pollution have become the main problems facing the world today, and my country has included "energy saving and emission reduction" as a goal in the 12th Five-Year Plan. Among the many initiatives, semiconductor photocatalysis technology is particularly eye-catching. By directly using ultraviolet light from various sources including sunlight, it can completely degrade and mineralize various organic or inorganic pollutants at room temperature. , this technology has the characteristics of low energy consumption, easy operation, and high cleanliness, especially in the treatment of some special pollutants, photocatalytic technology has advantages that other technologies cannot match; as a cutting-edge technology, it has broader application prospects . In 2001, this technology was first applied to the air purification of the U.S. space station. Recently, the building surface of the China Aviation Pavilion at the Shanghai World Expo also provided a display space for it.

In the 1970s, Fujishima and Honda discovered that the rutile-phase titanium dioxide single crystal electrode excited by ultraviolet light could decompose water at room temperature; then it was discovered that titanium dioxide excited by ultraviolet light could decompose toxic substances such as biphenyl and cyanide in water. degradation, and put forward the suggestion of using photocatalytic technology for environmental purification. Since then, the control of environmental pollution has become the most active research direction in the field of semiconductor photocatalysis. Among many semiconductor photocatalysts, titanium dioxide is by far the best, and research on it has always been at the core. Titanium dioxide not only has high catalytic activity and strong oxidation ability, but also has the advantages of non-toxicity, low cost and good stability.

Studies have found that the photocatalytic activity of titanium dioxide is determined by many factors, such as crystallinity, defects, specific surface, surface acidity, etc., but it is generally believed that the most important determinant is the crystal form. Commonly used TiO ₂ has two crystal forms, namely anatase type and rutile type. In photocatalytic reactions, anatase type titanium oxide usually has better performance. Among the current commercial titanium dioxide, the photocatalytic effect of Degussa P25 is particularly outstanding, and it is often used as a measure to evaluate a certain photocatalyst. In the produced titanium dioxide, the ratio of the anatase phase to the rutile phase is about 4:1. In terms of photocatalysis, the activity of the mixed crystal is often higher than that of the pure phase of titanium dioxide, that is, there is a so-called "mixed crystal effect". In recent years, a large number of studies have started from simulating the composition of P25, and have prepared mixed crystal titanium dioxide with different compositions and structures in various ways, which has improved the photocatalytic activity to a certain extent. effect” but no consistent conclusions have been reached. Therefore, the preparation of highly active mixed-crystal catalysts by facile methods is still a problem to be solved.

The reference material that the present invention adopts:

M. R. Hoffmann, S. T. Martin, W. Choi, D. W. Bahnemann, Chem. Rev. 1995, 95, 69-96;

R. J. Bickley, T. Gonzalez-Carreno, J. S. Lees, L. Palmisano, R. D. Tilley, J. Solid State Chem. 1991, 92, 178-190;

Z. Liu, X. Zhang, S. Nishimoto, M. Jin, D. A. Tryk, T. Murakami, A. Fujishima, Langmuir 2007, 23, 10916-10919;

M. Yan, F. Chen, J. Zhang, M. Anpo, J. Phys. Chem. B 2005, 109, 8673-8678;

A. Zachariah, K. V. Baiju, S. Shukla, K. S. Deepa, J. James, K. G. K. Warrier, J. Phys. Chem. C 2008, 112, 11345-11356.

Contents of the invention

The object of the present invention is to provide a mixed crystal titanium dioxide photocatalyst with high catalytic activity. The object of the present invention is achieved through the following technical measures:

It includes titanium dioxide powder particles, and the titanium dioxide powder particles are a mixture of two or more different crystal forms of titanium dioxide.

Through the above technical solutions, the photocatalytic effect of the present invention is significantly improved.

The object of the present invention is also to provide the preparation method of above mixed crystal titanium dioxide photocatalyst, and the object of the present invention is realized by the following technical measures:

It includes the following steps:

1) At room temperature, mix different titanium dioxide (crystal form A and crystal form B) in the dispersant solvent, the mass ratio of crystal form A to crystal form B is 1-100;

2) Ultrasonic dispersion for 10-60 minutes;

3) Continue stirring for 0.5-2 hours;

4) After removing the solvent, calcinate at 200-600°C for 0.5-4 hours to obtain the mixed crystal titanium dioxide photocatalyst.

Through the above technical scheme, the cost of raw materials used in the present invention is low, the equipment is simple, and it is easy to operate; compared with the single-crystal titanium dioxide, the obtained photocatalyst has significantly improved ultraviolet photocatalytic activity.

Description of drawings

Fig. 1 is a structural schematic diagram of the mixed crystal titanium dioxide photocatalyst of the present invention, wherein A and B respectively represent titanium dioxide powder particles of different crystal forms.

Fig. 2 is a graph showing the change trend of photocatalytic activity (evaluated by phenol degradation) with the content of rutile phase in the mixed crystal titanium dioxide catalyst.

Fig. 3 X-ray diffraction pattern of rutile titanium dioxide after heat treatment at different temperatures.

Fig. 4 is the ultraviolet-visible diffuse reflectance spectrum of rutile titanium dioxide after heat treatment at different temperatures.

Figure 5 is a trend diagram of the photocatalytic activity of the precursor rutile titanium dioxide (evaluated by phenol degradation) with the calcination temperature.

Figure 6 is a schematic diagram of the improvement of the photocatalytic activity of the mixed crystal catalyst by pre-calcination of the precursor rutile titanium dioxide (600, 700, 800, 900 ° C), where D, E, and F represent the anatase and rutile in the mixed sample, respectively The ratio is 1:10, 1:4, 1:2.

Fig. 7 is a flow chart of the preparation method of the mixed crystal titanium dioxide photocatalyst of the present invention (wherein A and B respectively represent two crystal forms of titanium dioxide).

Figure 8 is a flow chart of the preparation method shown in Figure 7 after adding the step of calcining one of the crystal forms of titanium dioxide at 500-1000°C for 1-5 hours (wherein A and B respectively represent two crystal forms of titanium dioxide ).

the

Detailed ways

Refer to accompanying drawing 1. The invention is a mixed crystal titanium dioxide photocatalyst containing two or more crystal forms, which includes titanium dioxide powder particles, and the titanium dioxide powder particles are a mixture of two or more different crystal forms of titanium dioxide. The titanium dioxides of different crystal forms are uniformly dispersed.

The invention also discloses a preparation method of the mixed crystal titanium dioxide photocatalyst. It includes the following steps:

1) At room temperature, mix different titanium dioxide (crystal form A and crystal form B) in the dispersant solvent, the mass ratio of crystal form A to crystal form B is 1-100;

2) Ultrasonic dispersion for 10-60 minutes;

3) Continue stirring for 0.5-2 hours;

4) After removing the solvent, calcinate at 200-600°C for 0.5-4 hours to obtain the mixed crystal titanium dioxide photocatalyst.

The step 1) also includes: calcining one of the crystal forms of titanium dioxide at 500-1000° C. for 1-5 hours.

In the present invention, after calcining one of the crystal forms of titanium dioxide at 500-1000°C for 1-5 hours, the steps become:

1) Calcinate a certain crystal form of titanium dioxide (B) as a precursor at 500-1000°C for 1-5 hours;

2) At room temperature, mix the above-mentioned calcined titanium dioxide (B) and another crystal form of titanium dioxide (A) in a solvent as a dispersant, the mass ratio of A to B is 1-100;

3) Ultrasonic dispersion for 10-60 minutes;

4) Continue to stir for 0.5 to 2 hours;

5) After removing the solvent, calcining at 200-600°C for 0.5-4 hours to obtain the mixed crystal titanium dioxide photocatalyst.

the

The crystal form is anatase type, rutile type, brookite type or a mixture of any two thereof.

The solvent used as the dispersant is any one or a mixture of two or three of water and ethanol, methanol, isopropanol, n-butanol, and tert-butanol.

the

In summary, the present invention uses commercial or self-prepared titanium dioxide as a precursor, uniformly mixes titanium dioxide with different crystal forms by solvent dispersion method, and the obtained mixed crystal catalyst has higher In addition, a method for further improving the activity of the mixed crystal photocatalyst is disclosed, that is, one of the crystal forms of titanium dioxide is calcined at 500-1000° C. for 1-5 hours.

The method of the invention can use readily available commercial products or self-prepared titanium dioxide powder particles as raw materials to further improve the photocatalytic activity of the titanium dioxide, and has great application potential in the fields of organic catalysis and environmental science and engineering. The invention has simple process, low requirements on equipment, less energy consumption, cheap and easy-to-obtain raw materials, and is suitable for large-scale production.

the

In the above preparation process, the selected precursor is commercial titanium dioxide or self-prepared titanium dioxide.

the

The evaluation method of photocatalytic activity is as follows: use a high-pressure mercury lamp (375W) as the external light source, the main wavelength of radiation is 365nm, the dosage of the catalyst is 50mg, mix it with 50ml of phenol solution (C ₀ ) with a concentration of 40ppm before the reaction, and shake overnight in the dark . The light reaction was carried out in a Pyrex glass container equipped with a cooling water jacket, and the reaction temperature was maintained at 25±2°C. Take 1.5ml of the reaction solution at regular intervals, filter it through a microporous membrane (0.45μm), and measure the phenol concentration C _t in the filtrate by HPLC. According to the first-order reaction kinetic equation ln(C _t /C ₀ )=-k _obs t, the apparent rate constant (k _obs ) was calculated and used as a measure of the relative photocatalytic activity of different catalysts.

the

Embodiment one

Take 0.6g of commercial anatase phase titanium oxide (AT) and 0.3g of commercial rutile phase titanium oxide (RT) and disperse them in 50ml of isopropanol, mix ultrasonically for 30 minutes, continue magnetic stirring for 1 hour, and remove at 80°C solvent. The obtained solid was ground and then calcined at 450° C. for 3 hours to obtain mixed crystal titanium dioxide catalyst A. The ratio of anatase phase to rutile phase is 2:1. Using the photocatalytic activity evaluation method described above, the photocatalytic activity of catalyst A was 1.83 and 1.31 times that of AT and RT used as raw materials, respectively. Obviously, under the same conditions, the mixed crystal catalyst A has stronger UV photocatalytic activity than the single crystal form of titanium dioxide (AT or RT).

Embodiment two

Take 0.2g commercial anatase phase titanium oxide (AT) and 0.8g commercial rutile phase titanium oxide (RT) and disperse in 50ml of isopropanol, mix ultrasonically for 30 minutes, continue magnetic stirring for 1 hour, and remove at 80°C solvent. The obtained solid was ground and calcined at 450° C. for 3 hours to obtain mixed crystal titanium dioxide catalyst B. The ratio of anatase phase to rutile phase is 1:4. Using the photocatalytic activity evaluation method described above, the photocatalytic activity of Catalyst B was 1.63 and 1.17 times that of AT and RT used as raw materials, respectively. The ultraviolet photocatalytic activity of the mixed crystal catalyst B is higher than that of the single crystal form of titanium dioxide (AT or RT).

Embodiment three

Take 0.5g commercial anatase phase titanium oxide (AT) and 0.5g commercial rutile phase titanium oxide (RT) and disperse in 50ml of isopropanol, mix ultrasonically for 30 minutes, continue magnetic stirring for 1 hour, and remove at 80°C solvent. The obtained solid was ground and then calcined at 600° C. for 3 hours to obtain mixed crystal titanium dioxide catalyst C. The ratio of anatase phase to rutile phase is 1:1. Using the photocatalytic activity evaluation method described above, the photocatalytic activity of Catalyst C was 1.95 and 1.39 times that of AT and RT used as raw materials, respectively. The ultraviolet photocatalytic activity of the mixed crystal catalyst C is higher than that of the single crystal form of titanium dioxide (AT or RT).

Embodiment Four

Take 1g of self-prepared rutile titanium dioxide, calcined at 600°C and 900°C for 3 hours respectively (referred to as RT600, RT900), and then mix it with 0.1g of commercial anatase phase titanium dioxide. The preparation conditions and photocatalytic evaluation methods are the same as in Example 1 , The resulting catalyst is recorded as D600, D900. The differences between the apparent rate constants of phenol degradation between D600 and RT600, and between D900 and RT900 were calculated to reflect the influence of precursor RT calcination temperature on the activity of mixed crystal samples. The results showed that the photocatalytic activity of D900 was 9.13 times higher than that of D600. It can be seen that high temperature pretreatment of the precursor is an effective method to improve the photocatalytic effect of mixed crystal titanium dioxide.

Embodiment five

Take 1g of self-prepared rutile titanium dioxide, calcined at 600°C and 900°C for 3 hours, respectively, and mix it with 0.25g of commercial anatase phase titanium dioxide. The preparation conditions and photocatalytic evaluation method are the same as in Example 4. The obtained catalysts are recorded as E600 and E900 . The photocatalytic activity of E900 is 3.96 times higher than that of E600. Calcination of RT, one of the precursors, at high temperature (900 °C) can effectively improve the activity of the mixed crystal catalyst.

Embodiment six

Take 1g of self-prepared rutile titanium dioxide, calcined at 600°C and 900°C for 3 hours, respectively, and mix it with 0.5g of commercial anatase phase titanium dioxide. The preparation conditions and photocatalytic evaluation method are the same as in Example 4. The obtained catalysts are recorded as F600 and F900 . The photocatalytic activity of F900 is 1.64 times higher than that of F600.

Embodiment seven

Take 1g of self-prepared rutile titanium dioxide, calcined at 600°C and 800°C for 3 hours, respectively, and mix it with 0.1g of commercial anatase phase titanium dioxide. The preparation conditions and photocatalytic evaluation method are the same as in Example 4. The obtained catalysts are recorded as D600 and D800 . The photocatalytic activity of D800 is 7.17 times higher than that of D600.

Embodiment eight

Take 1g of self-prepared rutile titanium dioxide, calcined at 600°C and 700°C for 3 hours, and then mix it with 0.1g of commercial anatase phase titanium dioxide. The preparation conditions and photocatalytic evaluation method are the same as in Example 4. The obtained catalysts are recorded as D600 and D700 . The photocatalytic activity of D700 is 6.00 times higher than that of D600.

Embodiment nine

Take 1g of self-prepared rutile titanium dioxide, calcined at 600°C and 800°C for 3 hours, and then mix it with 0.25g of commercial anatase phase titanium dioxide. The preparation conditions and photocatalytic evaluation method are the same as in Example 4. The obtained catalysts are recorded as E600 and E800 . The photocatalytic activity of E800 is 3.28 times higher than that of E600.

Embodiment ten

Take 1g of self-prepared rutile-type titanium dioxide, calcined at 600°C and 700°C for 3 hours, and mix it with 0.25g of commercial anatase phase titanium dioxide. The preparation conditions and photocatalytic evaluation method are the same as in Example 4. The obtained catalysts are recorded as E600 and E700 . The photocatalytic activity of E700 is 2.00 times higher than that of E600.

Embodiment Eleven

Take 1 g of self-prepared rutile titanium dioxide (RT) and calcinate them at 600°C and 900°C for 3 hours respectively. The obtained catalysts are denoted as RT600 and RT900. The apparent rate constants of the two phenol degradation are 1.21×10 ^-3 min ^-1 respectively and 0.42×10 ^-3 min ^-1 , which are 0.99 and 0.34 times that of the uncalcined RT sample, respectively. It can be seen that the calcination treatment cannot significantly improve the photocatalytic activity of the precursor RT, which indicates that the different degrees of activity improvement of the mixed crystal samples in the above examples (4 to 10) should be the result of the interaction between the two phases.

the

The specific implementation above is used to explain the present invention, and is only a preferred embodiment of the present invention, rather than restricting the present invention. Within the spirit of the present invention and the scope of protection of the claims, any modification, equivalent Replacement, improvement, etc., all fall within the protection scope of the present invention.

Claims (7)

1. mixed crystal titanium dioxide optical catalyst, it is characterized in that: it comprises the titanium dioxide powder particle, said titanium dioxide powder particle is the mixture of two or more different crystal forms titanium dioxide.

2. a kind of mixed crystal titanium dioxide optical catalyst as claimed in claim 1 is characterized in that the titanium dioxide of said different crystal forms evenly disperses.

3. a kind of according to claim 1 preparation method of mixed crystal titanium dioxide optical catalyst is characterized in that it may further comprise the steps:

1) at normal temperatures, different titanium dioxide (crystal form A and crystal form B) is mixed in the solvent as dispersant, the mass ratio of crystal form A and crystal form B is 1～100;

2) ultrasonic dispersion is 10～60 minutes;

3) continue to stir 0.5～2 hour;

4) behind the removal solvent,, promptly get the mixed crystal titanium dioxide optical catalyst in 200～600 ℃ of calcinings 0.5～4 hour.

4. like the preparation method of the said a kind of mixed crystal titanium dioxide optical catalyst of claim 3, it is characterized in that said step 1) also comprises:

With the titanium dioxide of a kind of crystal formation wherein in 500～1000 ℃ of calcinings 1～5 hour.

5. a kind of mixed crystal titanium dioxide optical catalyst as claimed in claim 1 is characterized in that said crystal formation is Detitanium-ore-type, rutile-type, brookite type or wherein any two kinds mixing.

6. a kind of mixed crystal titanium dioxide optical catalyst as claimed in claim 2 is characterized in that said dispersant is any one or two or three mixing of water and ethanol, methyl alcohol, isopropyl alcohol, n-butanol, the tert-butyl alcohol.

7. like the preparation method of claim 3 or 4 described a kind of mixed crystal titanium dioxide optical catalysts, it is characterized in that said crystal formation is Detitanium-ore-type, rutile-type, brookite type or its any two kinds mixing.

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