A secondary calcined tungsten oxide, a preparation method and application thereof
By employing a two-stage calcination process and a chimney-effect exhaust method, the problems of water vapor and ammonia in the preparation of solid-phase tungsten oxide were solved, enabling the preparation of high-quality tungsten oxide suitable for ultrafine crystal rods and photocatalyst materials.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-10-28
- Publication Date
- 2026-03-31
AI Technical Summary
In the existing solid-state method for preparing tungsten oxide, the water vapor and ammonia generated during APT calcination affect the yield and quality, and traditional methods are difficult to effectively control the particle size and purity of tungsten oxide.
The process employs a two-stage calcination process, using industrial rotary kilns with different tilt angles and rotation speeds. By combining the feed rate and temperature differences, a chimney effect is created to exhaust waste gas, controlling the particle size and purity of tungsten oxide. Moisture is initially removed at low temperatures, followed by further reaction at high temperatures.
This method yields tungsten oxide with fine particle size, narrow bulk density, and stable sieving performance, suitable for ultrafine crystal rods and photocatalyst materials, simplifying the process and reducing costs.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of inorganic material preparation technology, specifically relating to a secondary calcined tungsten oxide, its preparation method, and its application. Background Technology
[0002] Tungsten oxide is a tungstate anhydride, a tungstate product. Due to its highly tunable structure and unique photocatalytic, photochromic, and electrochromic properties, it is widely used in photocatalytic degradation, field emission equipment, and electrochromic devices. Meanwhile, because the particle size and bulk density of tungsten oxide directly affect the performance of subsequent products, the performance requirements for tungsten oxide products are becoming increasingly stringent with the development of the cemented carbide industry.
[0003] Currently, there are three methods for preparing tungsten oxide: gas-phase, liquid-phase, and solid-phase methods. The gas-phase method is rarely used due to its difficult synthesis and high equipment costs. While the liquid-phase method is low-cost, the sol-gel transition process is difficult, and the post-processing is cumbersome and time-consuming, making it unsuitable for widespread application. The solid-phase method is simple, involves virtually no phase change, and offers better product control. However, it typically uses ammonium paratungstate (APT) as a raw material for calcination. During calcination, APT generates water vapor and ammonia, directly affecting tungsten oxide formation. Although some researchers have implemented reverse ventilation to remove these gases, it still easily extracts fine tungsten oxide and APT particles, impacting yield, wasting raw materials, and compromising quality. Therefore, improving the solid-phase method to obtain high-quality tungsten oxide without affecting yield is a worthy research topic. Summary of the Invention
[0004] The purpose of this invention is to provide a secondary calcined tungsten oxide, its preparation method, and its application. The preparation method is simple and feasible, and the obtained tungsten oxide has the characteristics of fine particle size, narrow bulk density, and stable sieving performance. It has broad potential application value in ultrafine crystal rods, petroleum catalysts, and photocatalyst materials.
[0005] This invention provides a method for preparing tungsten oxide by secondary calcination, the method comprising:
[0006] Primary calcination: APT raw material is fed into an industrial rotary kiln with an inclination angle of 5-6° at a feeding rate of 100-500 g / min to obtain primary calcined tungsten oxide;
[0007] Secondary calcination: The calcined tungsten oxide is fed into an industrial rotary kiln with an inclination angle of 2-3° at a feeding rate of 800-1000 g / min to obtain secondary calcined tungsten oxide.
[0008] This technical solution involves two calcinations using rotary kilns with different inclination angles. In the first calcination, a rotary kiln with a larger inclination is used. The water vapor and ammonia generated by ammonium paratungstate can be discharged from the feed end of the rotary kiln due to a certain chimney effect, eliminating the need for additional discharge equipment. This not only prevents the discharge of small-diameter tungsten oxide particles but also does not affect tungsten oxide formation, saving on process time and costs. Simultaneously, the quality of tungsten oxide is controlled by adjusting the feed rate and the rotation speed of the rotary kiln. The first calcination primarily uses low temperature and low speed feeding and rotation to ensure the removal of water vapor and other gases from the raw material, resulting in uniformly sized and highly permeable calcined tungsten oxide. In the second calcination, increasing the calcination temperature, feed rate, and rotation speed increases the impact velocity of the material particles, effectively controlling the purity and particle size of the tungsten oxide.
[0009] Preferably, in the above technical solution, the temperature of the primary calcination is 200-400℃, wherein the temperature at the feed inlet of the industrial rotary kiln is 20-40℃ higher than the temperature at the discharge outlet; the temperature of the secondary calcination is 600-1000℃. In this technical solution, low-temperature calcination is first used to remove the main water vapor and other gases, increasing the specific surface area and permeability. By setting a temperature difference between the feed inlet and discharge outlet, the water vapor removal efficiency is further improved. Then, high-temperature secondary calcination is used to improve the reaction rate and product purity. The process is simple and feasible.
[0010] Preferably, in the above technical solution, the industrial rotary kiln rotates at a speed of 1-3 r / min during the primary calcination. In this technical solution, the low-speed rotation can prolong the residence time of the material, resulting in more thorough removal of gases such as water vapor during calcination and a more complete reaction.
[0011] Preferably, in the above technical solution, the industrial rotary kiln rotates at a speed of 2-6 r / min during the secondary calcination. This technical solution employs a faster rotation speed, increasing the impact velocity of material particles within the rotary kiln, which prevents sintering and agglomeration during high-temperature calcination, resulting in more uniform particle size.
[0012] Preferably, in the above technical solution, the APT is one or more of fine-grained APT, single-crystal APT, coarse-grained APT, and ordinary APT.
[0013] Preferably, in the above technical solution, the Fisher particle size of the secondary calcined tungsten oxide is ≤15μm.
[0014] Preferably, in the above technical solution, the loose packing density of the secondary calcined tungsten oxide is 2.3-2.6 m³. 3 / g.
[0015] Preferably, in the above technical solution, the industrial rotary kiln has a diameter of 400mm and a length of 8-10m. Specifically, the length-to-diameter ratio of the rotary kiln during the two calcination processes is 20:1-25:1. In this technical solution, by using rotary kilns of different lengths, combined with feeding speed and rotation speed, the calcination time for the two processes can be effectively controlled, improving both product quality and production efficiency.
[0016] The present invention also provides a secondary calcined tungsten oxide prepared by the above method.
[0017] The present invention also provides an application of the above-mentioned secondary calcined tungsten oxide in ultrafine crystalline rods, petroleum catalysts, and photocatalyst materials.
[0018] Advantages compared to existing technologies:
[0019] This invention employs a two-stage calcination method to prepare tungsten oxide. Calcination is carried out using rotary kilns with different tilt angles, rotation speeds, and aspect ratios. Based on the principle of gas rising upon heating, the tilt angle of the rotary kiln used in the primary calcination is set slightly larger, and the temperature difference between the feed inlet and outlet is controlled to create a chimney effect, effectively expelling waste gas from the feed inlet without the need for additional wind power or other assistance, thus simplifying the process. By controlling the feed rate, rotary kiln rotation speed, and calcination temperature, the resulting tungsten oxide particles are fine, have a narrow bulk density, and exhibit stable sieving performance. The solid-phase method for preparing tungsten oxide eliminates the need for organic solvents, making it safe and environmentally friendly. Attached Figure Description
[0020] Figure 1 This is a SEM image of calcined tungsten oxide from Example 1 of the present invention;
[0021] Figure 2 This is a SEM image of tungsten oxide subjected to secondary calcination in Example 2 of the present invention;
[0022] Figure 3 This is a SEM image of calcined tungsten oxide from Example 3 of the present invention;
[0023] Figure 4 This is a SEM image of tungsten oxide, Comparative Example 1 of the present invention. Detailed Implementation
[0024] The above-described technical features of the present invention and the technical features specifically described below (such as in the embodiments) can be combined with each other to form new or preferred technical solutions. However, the present invention is not limited to these embodiments, nor are these embodiments limited in any way.
[0025] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the formulations involved in the following examples are all commercially available products and can be purchased from the market.
[0026] This invention discloses a method for preparing tungsten oxide by secondary calcination, specifically including the following steps:
[0027] Primary calcination: APT raw material is fed into an industrial rotary kiln with an inclination angle of 5-6°, a diameter of 400 mm, and a length of 8-10 m at a feeding rate of 100-500 g / min to obtain primary calcined tungsten oxide;
[0028] The raw material used in this step is readily available APT, which can be one or more of fine-grained APT, single-crystal APT, coarse-grained APT, and ordinary APT. If the tilt angle of the rotary kiln is too small, although the calcination is more complete, it is not conducive to the discharge of gases such as water vapor, which affects the formation of tungsten oxide. If the tilt angle is too large, the material moves too fast, which can easily lead to incomplete calcination. In addition to controlling the feeding speed and the tilt angle of the rotary kiln, the calcination temperature and rotation speed are also very important. Calcination is carried out at a relatively low temperature of 200-400℃ (the feed temperature of an industrial rotary kiln is 20-40℃ higher than the discharge temperature), and the rotation speed of the rotary kiln is controlled at 1-3 r / min. This ensures uniform calcination, effectively removes and discharges gases such as water vapor and ammonia, and results in a large specific surface area and good permeability of the calcined tungsten oxide.
[0029] Secondary calcination: The calcined tungsten oxide is fed into an industrial rotary kiln with an inclination angle of 2-3°, a diameter of 400 mm, and a length of 8-10 m at a feeding rate of 800-1000 g / min to obtain secondary calcined tungsten oxide.
[0030] In this step, calcined tungsten oxide is used as raw material. By increasing the feed rate and reducing the tilt angle of the rotary kiln, while further controlling the kiln temperature at 600-1000℃ and the rotation speed at 2-6 r / min, the reaction rate of the tungsten oxide and the material impact velocity are improved. This prevents agglomeration due to increased feed rate and higher temperature, resulting in a more complete and uniform reaction. The final calcined tungsten oxide has a Fisher particle size ≤15μm, between 8-12μm, and a loose packing density of 2.3-2.6m³. 3 The particle size distribution is between / g, with a narrow packing ratio. After passing through a 325-mesh sieve, the sieve yield is over 90%, demonstrating stable sieving performance and uniform particle size, which meets the requirements for producing ultrafine crystal rods, petroleum catalysts, and photocatalyst materials.
[0031] The present invention will be further described in detail below with reference to specific embodiments:
[0032] Example 1
[0033] A method for preparing tungsten oxide by secondary calcination specifically includes the following steps:
[0034] Primary calcination: Fine-grained APT raw material is fed into an industrial rotary kiln with an inclination angle of 5.5°, a temperature of 250° (the temperature at the feed port is 20° higher than that at the discharge port), a diameter of 400mm, and a length of 10m at a feed rate of 300g / min. The kiln is rotated at a speed of 2r / min. After calcination, the material is discharged to obtain primary calcined tungsten oxide.
[0035] Secondary calcination: The calcined tungsten oxide from the first calcination is fed into an industrial rotary kiln with an inclination angle of 2.5°, a temperature of 700℃, a diameter of 400mm, and a length of 9m at a feed rate of 900g / min. The kiln is rotated at a speed of 4r / min. The calcined material is then discharged to obtain the secondary calcined tungsten oxide.
[0036] The obtained calcined tungsten oxide was observed under a 2000x electron microscope, and its SEM image is shown below. Figure 1 As shown.
[0037] Example 2
[0038] A method for preparing tungsten oxide by secondary calcination specifically includes the following steps:
[0039] First calcination: Single crystal APT raw material is fed into an industrial rotary kiln with an inclination angle of 6°, a temperature of 400℃ (the temperature at the feed port is 40℃ higher than that at the discharge port), a diameter of 400mm, and a length of 9.5m at a feed rate of 100g / min. At the same time, the kiln is rotated at a speed of 3r / min. After calcination, the material is discharged to obtain first calcined tungsten oxide.
[0040] Secondary calcination: The calcined tungsten oxide from the first calcination is fed into an industrial rotary kiln with an inclination angle of 3°, a temperature of 800℃, a diameter of 400mm, and a length of 8m at a feed rate of 800g / min. The kiln is rotated at a speed of 6r / min. The calcined material is then discharged to obtain the secondary calcined tungsten oxide.
[0041] The obtained calcined tungsten oxide was observed under a 2000x electron microscope, and its SEM image is shown below. Figure 2 As shown.
[0042] Example 3
[0043] A method for preparing tungsten oxide by secondary calcination specifically includes the following steps:
[0044] Primary calcination: Coarse-grained APT raw material is fed into an industrial rotary kiln with an inclination angle of 5°, a temperature of 300℃ (the temperature at the feed port is 30℃ higher than that at the discharge port), a diameter of 400mm, and a length of 9m at a feed rate of 500g / min. The kiln is rotated at a speed of 1r / min. After calcination, the material is discharged to obtain primary calcined tungsten oxide.
[0045] Secondary calcination: The calcined tungsten oxide is fed into an industrial rotary kiln with an inclination angle of 2°, a temperature of 600℃, a diameter of 400mm, and a length of 8m at a feed rate of 1000g / min. The kiln is rotated at a speed of 2r / min. The calcined material is then discharged to obtain the secondary calcined tungsten oxide.
[0046] The obtained calcined tungsten oxide was observed under a 2000x electron microscope, and its SEM image is shown below. Figure 3 As shown.
[0047] Comparative Example 1
[0048] A method for preparing tungsten oxide specifically includes the following steps:
[0049] Fine-grained APT raw material is fed at a rate of 300 g / min into an industrial rotary kiln with an inclination angle of 5.5°, a temperature of 250° (the temperature at the inlet is 20° higher than that at the outlet), a diameter of 400 mm, and a length of 10 m. The kiln is rotated at a speed of 2 r / min. After calcination, calcined tungsten oxide is discharged.
[0050] The obtained calcined tungsten oxide was observed under a 2000x electron microscope, and its SEM image is shown below. Figure 4 As shown.
[0051] Comparative Example 2
[0052] A method for preparing tungsten oxide by secondary calcination specifically includes the following steps:
[0053] Primary calcination: Fine-grained APT raw material is fed into an industrial rotary kiln with an inclination angle of 2°, a temperature of 250℃ (the temperature at the feed port is 20℃ higher than that at the discharge port), a diameter of 400mm, and a length of 10m at a feed rate of 300g / min. The kiln is rotated at a speed of 2r / min. After calcination, the material is discharged to obtain primary calcined tungsten oxide.
[0054] Secondary calcination: The calcined tungsten oxide from the first calcination is fed into an industrial rotary kiln with an inclination angle of 2.5°, a temperature of 700℃, a diameter of 400mm, and a length of 9m at a feed rate of 900g / min. The kiln is rotated at a speed of 4r / min. The calcined material is then discharged to obtain the secondary calcined tungsten oxide.
[0055] Comparative Example 3
[0056] A method for preparing tungsten oxide by secondary calcination specifically includes the following steps:
[0057] Primary calcination: Fine-grained APT raw material is fed into an industrial rotary kiln with an inclination angle of 7°, a temperature of 250℃ (the temperature at the feed port is 20℃ higher than that at the discharge port), a diameter of 400mm, and a length of 10m at a feed rate of 300g / min. The kiln is rotated at a speed of 2r / min. After calcination, the material is discharged to obtain primary calcined tungsten oxide.
[0058] Secondary calcination: The calcined tungsten oxide from the first calcination is fed into an industrial rotary kiln with an inclination angle of 2.5°, a temperature of 700℃, a diameter of 400mm, and a length of 9m at a feed rate of 900g / min. The kiln is rotated at a speed of 4r / min. The calcined material is then discharged to obtain the secondary calcined tungsten oxide.
[0059] Comparative Example 4
[0060] A method for preparing tungsten oxide by secondary calcination specifically includes the following steps:
[0061] Primary calcination: Fine-grained APT raw material is fed into an industrial rotary kiln with an inclination angle of 5.5°, a temperature of 250° (the temperature at the feed port is 20° higher than that at the discharge port), a diameter of 400 mm, and a length of 10 m at a feed rate of 300 g / min. The kiln is rotated at a speed of 5 r / min. After calcination, the material discharged is primary calcined tungsten oxide.
[0062] Secondary calcination: The calcined tungsten oxide from the first calcination is fed into an industrial rotary kiln with an inclination angle of 2.5°, a temperature of 700℃, a diameter of 400mm, and a length of 9m at a feed rate of 900g / min. The kiln is rotated at a speed of 4r / min. The calcined material is then discharged to obtain the secondary calcined tungsten oxide.
[0063] Comparative Example 5
[0064] Primary calcination: Fine-grained APT raw material is fed into an industrial rotary kiln with an inclination angle of 5.5°, a temperature of 250° (the temperature at the feed port is 20° higher than that at the discharge port), a diameter of 400mm, and a length of 10m at a feed rate of 300g / min. The kiln is rotated at a speed of 2r / min. After calcination, the material is discharged to obtain primary calcined tungsten oxide.
[0065] Secondary calcination: The calcined tungsten oxide from the first calcination is fed into an industrial rotary kiln with an inclination angle of 5°, a temperature of 700℃, a diameter of 400mm, and a length of 9m at a feed rate of 900g / min. The kiln is rotated at a speed of 4r / min. The calcined material is then discharged to obtain the secondary calcined tungsten oxide.
[0066] Comparative Example 6
[0067] A method for preparing tungsten oxide by secondary calcination specifically includes the following steps:
[0068] Primary calcination: Fine-grained APT raw material is fed into an industrial rotary kiln with an inclination angle of 5.5°, a temperature of 250° (the temperature at the feed port is 20° higher than that at the discharge port), a diameter of 400 mm, and a length of 10 m at a feed rate of 300 g / min. The kiln is rotated at a speed of 2 r / min. After calcination, the material is discharged to obtain primary calcined tungsten oxide.
[0069] Secondary calcination: The calcined tungsten oxide from the first calcination is fed into an industrial rotary kiln with an inclination angle of 2.5°, a temperature of 700℃, a diameter of 400mm, and a length of 9m at a feed rate of 900g / min. The kiln is rotated at a speed of 2r / min. The calcined material is then discharged to obtain the secondary calcined tungsten oxide.
[0070] Combination Figure 1-4 It can be seen that the tungsten oxide obtained by the secondary calcination method of the present invention has a uniform particle size. Under 2000x electron microscopy, the tungsten oxide obtained by the primary low-temperature calcination in Comparative Example 1 has a smaller and more uniform particle size. This indicates that the tungsten oxide obtained by primary calcination does not meet the requirements for ultrafine crystal rods, petroleum catalysts, and photocatalyst materials in terms of particle size and loose packing density.
[0071] The Fisher particle size, bulk density, and -325 mesh sieve performance of the tungsten oxide prepared in Examples 1-3 and Comparative Examples 1-6 of this invention were tested, and the test results are shown in Table 1. The Fisher particle size was determined using a Fisher particle size analyzer, the bulk density was determined using GB / T1479.2 or GB / T5061, and the sieve performance was determined using the direct sieve method.
[0072] Table 1 Performance Test Results
[0073] Group Tungsten oxide Fsss particle size / μm <![CDATA[Bulk density / (m 3 / g)]]> -325 mesh / % Example 1 9.8 2.35 96.5 Example 2 12.0 2.52 93.8 Example 3 11.2 2.45 95.3 Comparative Example 1 43.3 4.96 21.2 Comparative Example 2 16.7 2.78 86.5 Comparative Example 3 18.2 2.88 74.5 Comparative Example 4 16.1 2.66 89.3 Comparative Example 5 17.6 2.85 76.8 Comparative Example 6 18.5 2.93 72.1
[0074] As can be seen from the test results in Table 1, the Fisher particle size of the calcined tungsten oxide prepared by the method of this invention is between 9.8 and 12.0 μm, the sieve residue after passing through a 325-mesh sieve is between 93.8% and 96.5%, and the loose packing density is between 2.35 and 2.52 m³. 3 The particle size is between / g, the particle size is fine and uniform, the loose packing ratio is narrow, the screening performance is stable, and the quality is good.
[0075] In Comparative Example 1, the tungsten oxide obtained after only one low-temperature calcination had a large Fisher particle size, high bulk density, and uneven particle size, indicating that the calcination reaction was not sufficient. In Comparative Examples 2, 3, and 4, the performance of the tungsten oxide decreased compared to Example 1. This indicates that the tilt angle of the rotary kiln during the first calcination was too small, which was not conducive to the discharge of waste gas. If the tilt angle was too large, the chimney effect was too fast, and some fine tungsten oxide particles were also carried out while the waste gas was discharged. The rotation speed was too fast, which was not conducive to uniform calcination, thus affecting the particle size, bulk density, screening performance, and yield of the tungsten oxide. In Comparative Examples 5 and 6, compared to Example 1, the tilt angle of the rotary kiln during the second calcination was larger, the material moved quickly, the reaction was not sufficient, the rotation speed was slower, the material impact speed was insufficient, and it was easy to agglomerate during the calcination process, thus affecting the particle size of the tungsten oxide.
[0076] In summary, the preparation method of this invention is simple, uses readily available raw materials, and is easy to industrialize. By controlling the process conditions during calcination, the obtained tungsten oxide particles are fine, have a narrow packing ratio, and exhibit stable sieving performance, making it applicable to ultrafine crystal rods, petroleum catalysts, and photocatalyst materials.
[0077] Finally, it should be emphasized that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for producing a twice calcined tungsten oxide, characterized by, The preparation method comprises: primary calcination: the APT raw material is added into an industrial rotary kiln with an inclination angle of 5-6° at a feeding speed of 100-500 g / min for calcination to obtain primary calcined tungsten oxide; the industrial rotary kiln rotates at a speed of 1-3 r / min in the primary calcination; secondary calcination: the primary calcined tungsten oxide is added into an industrial rotary kiln with an inclination angle of 2-3° at a feeding speed of 800-1000 g / min for calcination to obtain secondary calcined tungsten oxide; the industrial rotary kiln rotates at a speed of 2-6 r / min in the secondary calcination; the temperature of the primary calcination is 200-400℃, wherein the temperature at the feeding port of the industrial rotary kiln is 20-40℃ higher than the temperature at the discharging port; the temperature of the secondary calcination is 600-1000℃.
2. The method for preparing tungsten oxide by secondary calcination according to claim 1, characterized in that, The APT is one or several of fine-crystal APT, single-crystal APT, coarse-crystal APT, and common APT.
3. The method for preparing tungsten oxide by secondary calcination according to claim 1, characterized in that, The secondary calcined tungsten oxide has a Fisher particle size of ≤15 μm.
4. The method for preparing tungsten oxide by secondary calcination according to claim 1, characterized in that, The bulk density of the twice calcined tungsten oxide is 2.3-2.6 m 3 / g.
5. The method for preparing tungsten oxide by secondary calcination according to claim 1, characterized in that, The diameter of the industrial rotary kiln is 400 mm, and the length is 8-10 m.
6. Secondary calcined tungsten oxide prepared by the preparation method in any one of claims 1-5.
7. Application of the secondary calcined tungsten oxide in claim 6 in ultra-fine crystal rods, petroleum catalysts, and photocatalyst materials.
Citation Information
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