Preparation method of mixed crystal titanium dioxide
By adding mixed crystal titanium dioxide as seeds at low temperature, performing alkali precipitation and hydrothermal treatment, the problem of preparing large pore size, high specific surface area anatase and rutile mixed crystal titanium dioxide in the prior art is solved, and efficient preparation of catalyst support materials is achieved.
Patent Information
- Application Number
- CN202410101514.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-01-24
- Publication Date
- 2025-07-29
AI Technical Summary
The prior art is difficult to prepare anatase and rutile mixed crystal titanium dioxide with large pore sizes and high specific surface area at low temperatures, and the high temperature hydrolysis process is not easy to control, resulting in a decrease in specific surface area.
Mixed crystal titanium dioxide is prepared by adding mixed crystal titanium dioxide as seeds at low temperature, precipitation, and then hydrothermal treatment, washing, drying and calcining.
Anatase and rutile mixed crystal titanium dioxide with specific contents are prepared, with large pore sizes and high specific surface area. It is suitable for use as a catalyst support, reducing production costs and suitable for industrial production.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to the field of catalysts, and particularly to a preparation method of mixed-crystalline titanium dioxide. Background Art
[0002] Nano-titanium dioxide is widely used as a photocatalyst and a catalyst support. Titanium dioxide has three crystal forms, namely anatase, rutile and brookite. The commonly seen ones are generally the anatase and rutile crystal forms. Mixed-crystalline titanium dioxide, due to the mixing of the two structures, increases the defect density in the titanium dioxide lattice, increases the carrier concentration, and increases the number of electrons and holes, and is widely used as a catalyst support, such as Fischer-Tropsch iron-based and cobalt-based catalysts.
[0003] From the perspective of the preparation methods of titanium dioxide, the commonly seen ones in industry are the sulfuric acid method and the chlorination method. The titanium dioxide prepared by the sulfuric acid method generally has a high sulfur content and is not suitable as a support for Fischer-Tropsch iron and cobalt catalysts. The chlorination method uses titanium tetrachloride obtained by a chlorination process as a raw material, and obtains nano-titanium dioxide powder through a high-temperature oxidation process and post-treatment. This preparation method can obtain mixed-crystalline titanium dioxide, and the impurity content, especially the sulfur content, is low, and it is suitable as a support for Fischer-Tropsch iron and cobalt catalysts. However, the chlorination method has complex processes and devices, high danger, and high operation requirements. And using titanium tetrachloride as a raw material, through common hydrolysis and / or precipitation methods, it can also be used to prepare a titanium dioxide support.
[0004] Literature 1 (Zhou Zhongcheng, et al. Direct preparation of rutile-type nano-titanium dioxide by low-temperature hydrolysis of titanium tetrachloride, Rare Metals, 30(5), 653-656) reports that using titanium tetrachloride as a raw material, rutile-type nano-titanium dioxide powder is directly obtained by hydrolysis under low-temperature conditions.
[0005] Literature 2 (Sun Guoyu, et al. Preparation of nano-titanium dioxide powder by alkali precipitation method, Inorganic Chemicals Industry, 38(5), 18-22) uses the titanium tetrachloride alkali precipitation method (60-70 °C) to prepare nano-titanium dioxide powder. Anatase-type titanium dioxide can be obtained by calcination at 600 °C, and the specific surface area is 33.0 m 2 / g. If calcined at 800 °C, rutile-type titanium dioxide can be obtained, and the specific surface area is 9.0 m 2 / g at this time.
[0006] Literature 3 (Jin Xin, et al. Preparation, characterization and photocatalytic performance study of nano-titanium dioxide mixed crystals, Proceedings of the Tenth National Conference on Colloid and Interface Chemistry) heats the titanium tetrachloride aqueous solution to a certain temperature, keeps it warm for 60 min, and then drops ammonia water into the solution to precipitate and prepare nano-titanium dioxide mixed crystals (rutile phase ratio 0.3-70%).
[0007] Titanium tetrachloride is strongly acidic. Its direct hydrolysis can obtain rutile-phase titanium dioxide. If the method of dropping and precipitating with alkali is used, generally the obtained titanium dioxide is anatase-phase, with small pore size. To induce its phase transformation requires high-temperature calcination, which will inevitably cause a decrease in specific surface area. First, high-temperature hydrolysis is carried out to produce part of rutile-phase titanium dioxide, and then the alkali precipitation method can obtain titanium dioxide containing both rutile and anatase crystal phases. However, the high-temperature hydrolysis process is not easy to control, and its pore structure has a low specific surface area and small pore size. How to obtain titanium dioxide containing anatase and rutile mixed crystals, with large pore size and high specific surface area, is a challenge. Summary of the Invention
[0008] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a preparation method of mixed-crystal titanium dioxide. By adding mixed-crystal titanium dioxide as a seed crystal, alkali precipitation is carried out at low temperature, and then hydrothermal treatment, washing, drying, and calcination are carried out. The prepared titanium dioxide contains anatase and rutile mixed crystals, has a large pore size and a high specific surface area, and is suitable for use as a catalyst carrier.
[0009] To achieve the above purpose and technical effects, the present invention adopts the following technical solutions:
[0010] A preparation method of mixed-crystal titanium dioxide, comprising the following steps:
[0011] Step 1: Prepare an aqueous solution of titanium tetrachloride;
[0012] Step 2: Add an alkaline aqueous solution to the aqueous solution of titanium tetrachloride for coprecipitation;
[0013] Step 3: Carry out hydrothermal treatment on the slurry after coprecipitation;
[0014] Step 4: Wash, dry, and calcine the slurry after hydrothermal treatment to obtain mixed-crystal titanium dioxide.
[0015] According to the preparation method of the present invention, in Step 1, the aqueous solution of titanium tetrachloride is prepared in a cold water bath.
[0016] According to the preparation method of the present invention, in Step 1, the concentration of the aqueous solution of titanium tetrachloride is 1-2 mol / L.
[0017] According to the preparation method of the present invention, in Step 1, mixed-crystal titanium dioxide is added as a seed crystal to the prepared aqueous solution of titanium tetrachloride. Among them, the molar ratio of mixed-crystal titanium dioxide to titanium tetrachloride is 0.05:1-0.25:1. The mixed-crystal titanium dioxide is a mixed crystal of anatase crystal form and rutile crystal form, the anatase crystal form content is 75.0-85.0 wt%, and the rutile crystal form content is 15.0-25.0 wt%.
[0018] The preparation method according to the present invention, wherein in step 2, the alkaline aqueous solution is ammonia water.
[0019] The preparation method according to the present invention, wherein in step 2, the molar concentration ratio of the alkaline aqueous solution to the titanium tetrachloride aqueous solution is 0.5:1 - 2:1.
[0020] The preparation method according to the present invention, wherein in step 2, the coprecipitation temperature is 30 - 50 °C, and the pH of the slurry after coprecipitation is 6 - 8.5.
[0021] The preparation method according to the present invention, wherein in step 3, the hydrothermal treatment temperature is 120 - 180 °C, and the hydrothermal treatment time is 4 - 24 h.
[0022] The preparation method according to the present invention, wherein in step 4, the drying temperature is 80 - 150 °C, and the drying time is 1 - 24 h; the calcination temperature is 550 - 650 °C, and the calcination time is 2 - 12 h.
[0023] The preparation method according to the present invention, wherein in step 4, the prepared mixed crystal titanium dioxide is a mixed crystal of anatase crystal form and rutile crystal form, wherein the anatase crystal form content is 70.0 - 85.0 wt%, and the rutile crystal form content is 15.0 - 30.0 wt%.
[0024] The preparation method according to the present invention, wherein in step 4, the solvent used for washing is water and / or ethanol.
[0025] Beneficial effects
[0026] In the present invention, by adding mixed crystal titanium dioxide as a seed crystal, alkali precipitation is carried out at a low temperature, and then through hydrothermal treatment, washing, drying, and calcination, the prepared mixed crystal titanium dioxide contains a specific content of anatase and rutile mixed crystals, has a large pore size and a high specific surface area, and is suitable for use as a catalyst support. In addition, the reaction raw materials titanium tetrachloride and ammonia water for the preparation method of the mixed crystal titanium dioxide in the present invention are cheap and easily available, the operation is simple, and only a very small amount of mixed crystal titanium dioxide is used as a seed crystal in the reaction to prepare a high-yield mixed crystal titanium dioxide product with a specific content of anatase and rutile, so the production cost of the mixed crystal carbon dioxide is reduced, and it is suitable for industrial production. Description of the drawings
[0027] Figure 1 Shows the XRD pattern of the mixed crystal titanium dioxide product prepared in Example 1 of the present invention.
[0028] Figure 2 Shows the XRD pattern of the titanium dioxide product prepared in Comparative Example 3. Detailed implementation manners
[0029] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein.
[0030] The described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention belong to the scope of protection of the present invention.
[0031] Unless otherwise specified, the raw materials used in the following examples are all purchased commercially. The mixed crystal titanium dioxide seed used in the following examples was purchased from Evonik Industries AG.
[0032] BET test method and conditions: The specific surface area and pore structure of the sample were measured using a TriStarⅡ3020 (Micromeritics Inc.) fully automatic physical and chemical adsorption instrument at liquid nitrogen temperature (-196 °C). Before the test, 0.25 g of the sample was pretreated under high vacuum (<10-5 Torr) at 200 °C for 5 h. The specific surface area was calculated using the Barrett-Emmett-Teller (BET) formula, and the pore volume and pore size distribution were calculated according to the Barrett-Joyner-Halenda (BJH) model.
[0033] XRD test method and conditions: The phase structure of the sample was determined by X-ray diffraction (XRD). The experiment was carried out using a RIGAKU D / MAX 2550 / PC powder diffractometer (Rigaku, Japan), using Cu Kα radiation, with a tube current of 30 mA, a tube voltage of 40 kV, a scanning step of 0.02°, and a scanning range of 2θ = 10 - 80°. The ratio of anatase (2θ = 25.4) and rutile (2θ = 27.5) was calculated based on the peak areas.
[0034] Example 1
[0035] Prepare 1 L of 1 mol / L titanium tetrachloride solution in a cold water bath, add 4 g of mixed crystal titanium dioxide (81% anatase and 19% rutile phase), stir to form a slurry (the molar ratio of mixed crystal titanium dioxide to titanium tetrachloride is 0.05:1), precipitate it with 2 mol / L ammonia water, the precipitation temperature is 30 °C, the pH after precipitation is 8.5, then hydrothermally treat the precipitated slurry at 120 °C for 24 h, filter and wash the hydrothermally treated slurry, dry it at 80 °C for 24 h, and then calcine it at 550 °C for 12 h to obtain 83.5 g of titanium dioxide product. The XRD pattern is shown in Figure 1 .
[0036] Example 2
[0037] Prepare a 1.5 mol / L titanium tetrachloride solution of 1 L in a cold water bath. Add 18 g of mixed crystal titanium dioxide (81% anatase and 19% rutile phase), and stir to form a slurry (the molar ratio of mixed crystal titanium dioxide to titanium tetrachloride is 0.15:1). Precipitate it with 1.5 mol / L ammonia water. The precipitation temperature is 40 °C, and the pH after precipitation is 7.5. Then, hydrothermally treat the precipitated slurry at 150 °C for 12 h. Filter and wash the hydrothermally treated slurry, dry it at 120 °C for 10 h, and then calcine it at 600 °C for 8 h to obtain 137.4 g of titanium dioxide product. Its XRD pattern is the same as that of Figure 1 that of the basic one.
[0038] Example 3
[0039] Prepare a 2 mol / L titanium tetrachloride solution of 1 L in a cold water bath. Add 40 g of mixed crystal titanium dioxide (81% anatase and 19% rutile phase), and stir to form a slurry (the molar ratio of mixed crystal titanium dioxide to titanium tetrachloride is 0.25:1). Precipitate it with 1 mol / L ammonia water. The precipitation temperature is 50 °C, and the pH after precipitation is 6.0. Then, hydrothermally treat the precipitated slurry at 180 °C for 4 h. Filter and wash the hydrothermally treated slurry, dry it at 150 °C for 1 h, and then calcine it at 650 °C for 2 h to obtain 199.3 g of titanium dioxide product. Its XRD pattern is the same as that of Figure 1 that of the basic one.
[0040] Comparative Example 1
[0041] Prepare a 1 mol / L titanium tetrachloride solution of 1 L in a cold water bath. Precipitate it with 2 mol / L ammonia water. The precipitation temperature is 30 °C, and the pH after precipitation is 8.5. Filter and wash the slurry, dry it at 80 °C for 24 h, and then calcine it at 550 °C for 12 h to obtain 79.1 g of titanium dioxide product.
[0042] Comparative Example 2
[0043] Prepare a 1 mol / L titanium tetrachloride solution of 1 L in a cold water bath. Precipitate it with 2 mol / L ammonia water. The precipitation temperature is 30 °C, and the pH after precipitation is 8.5. Filter and wash the slurry, dry it at 80 °C for 24 h, and then calcine it at 800 °C for 4 h to obtain 79.1 g of titanium dioxide product.
[0044] Comparative Example 3
[0045] Prepare 1 L of 1 mol / L titanium tetrachloride solution with cold water bath, precipitate it with 2 mol / L ammonia water, the precipitation temperature is 30 °C, the pH is 8.5 after precipitation, then hydrothermally treat the precipitated slurry at 180 °C for 4 h, filter and wash the hydrothermally treated slurry, dry it at 80 °C for 24 h, and then calcine it at 550 °C for 12 h to obtain 79.2 g of titanium dioxide product.
[0046] Test Example 1
[0047] Perform BET test to determine its specific surface area and pore size; perform XRD test to determine the ratio of anatase and rutile. The test results are shown in Table 1 below.
[0048] Table 1
[0049]
[0050]
[0051] It can be seen from the test results in Table 1 that compared with the titanium dioxide product prepared in the comparative example, the titanium dioxide product prepared in the example of the present invention has a significantly higher specific surface area and a significantly larger pore size, and is more suitable as a catalyst support.
Claims
1. A preparation method of mixed crystal titanium dioxide, comprising the following steps: Step 1: Prepare an aqueous solution of titanium tetrachloride; Step 2: Add an alkaline aqueous solution to the aqueous solution of titanium tetrachloride for coprecipitation; Step 3: Perform hydrothermal treatment on the slurry after coprecipitation; Step 4: Wash, dry, and calcine the slurry after hydrothermal treatment to obtain mixed crystal titanium dioxide.
2. The preparation method according to claim 1, wherein, In Step 1, the aqueous solution of titanium tetrachloride is prepared in a cold water bath.
3. The preparation method according to claim 1, wherein, In Step 1, the concentration of the aqueous solution of titanium tetrachloride is 1 - 2 mol / L.
4. The preparation method according to claim 1, wherein, In step 1, anatase-rutile mixed crystal titanium dioxide is added as a seed crystal to the prepared titanium tetrachloride aqueous solution, wherein the molar ratio of the anatase-rutile mixed crystal titanium dioxide to titanium tetrachloride is 0.05:1 - 0.25:1, and the anatase-rutile mixed crystal titanium dioxide is a mixed crystal of anatase crystal form and rutile crystal form ， The content of anatase crystal form is 75.0 - 85.0 wt%, and the content of rutile crystal form is 15.0 - 25.0 wt%.
5. The preparation method according to any one of claims 1-4, wherein, In Step 2, the alkaline aqueous solution is ammonia water.
6. The preparation method according to claim 5, wherein In Step 2, the molar concentration ratio of the alkaline aqueous solution to the aqueous solution of titanium tetrachloride is 0.5:1 - 2:
1.
7. The preparation method according to claim 5, wherein, In Step 2, the coprecipitation temperature is 30 - 50 °C, and the pH of the slurry after coprecipitation is 6 - 8.
5.
8. The preparation method according to any one of claims 1-4, wherein In Step 3, the hydrothermal treatment temperature is 120 - 180 °C, and the hydrothermal treatment time is 4 - 24 h.
9. The preparation method according to any one of claims 1-4, wherein, In Step 4, the drying temperature is 80 - 150 °C, and the drying time is 1 - 24 h; the calcination temperature is 550 - 650 °C, and the calcination time is 2 - 12 h.
10. The preparation method according to claim 9, wherein, In Step 4, the obtained mixed crystal titanium dioxide is a mixed crystal of anatase crystal form and rutile crystal form, wherein the anatase crystal form content is 70.0 - 85.0 wt%, and the rutile crystal form content is 15.0 - 30.0 wt%.