Nano ammonium paratungstate and preparation method thereof
By controlling the dropping rate and pH value of ammonium tungstate in acidic solution and combining it with low-temperature heating crystallization, nano-sized ammonium paratungstate was prepared, solving the problem that the particle size is difficult to reach the nanoscale in the existing technology and realizing the preparation of high-performance tungsten products.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-17
- Publication Date
- 2026-03-31
AI Technical Summary
Existing technologies are insufficient to prepare ammonium paratungstate with nanoscale particle size, making it difficult to meet the demand for high-performance tungsten products.
Nanoscale ammonium paratungstate was prepared by controlling the dropping rate and pH value of ammonium tungstate solution in acidic solution and combining it with low-temperature heating crystallization. This controlled the formation and growth process of crystal nuclei and prevented excessive particle size and agglomeration.
The preparation of nanoscale ammonium paratungstate has been achieved, which has high specific surface area and excellent catalytic activity, and is suitable for applications in cemented carbide, catalysts and other fields.
Smart Images
Figure CN121757918A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of tungsten materials and relates to ammonium paratungstate, specifically to a nano-ammonium paratungstate and its preparation method. Background Technology
[0002] Ammonium paratungstate [(NH4)] 10 H2W 12 O 42 ]· x H2O is an important intermediate product in the tungsten smelting process. Due to its heritability, the physicochemical properties of ammonium paratungstate directly affect the properties of downstream products, such as tungsten carbide, tungsten oxide, and tungsten powder.
[0003] Ammonium paratungstate, as a precursor, can significantly improve the hardness and wear resistance of cemented carbide by reducing sintering to prepare tungsten carbide particles. By controlling the sintering process, ammonium paratungstate can achieve a gradient structure between the surface and core of cemented carbide, such as high surface hardness and high core toughness. Tungsten-copper composite materials prepared by ammonium paratungstate have both high thermal conductivity and low coefficient of thermal expansion. As a catalyst, ammonium paratungstate can improve catalytic efficiency in denitration catalysis, photocatalytic degradation, and hydrogen production catalysis.
[0004] However, the mainstream method for preparing ammonium paratungstate by evaporation and crystallization yields a product with a particle size of about 50 μm. In recent years, although there has been a lot of research on the preparation method of ultrafine ammonium paratungstate, its particle size is still at the micrometer level. As a precursor for downstream products, it is difficult to meet the needs of developing various high-performance tungsten products. Summary of the Invention
[0005] In view of the defects and deficiencies of the existing technology, the present invention provides, firstly, a nano-ammonium paratungstate; and secondly, a method for preparing nano-ammonium paratungstate.
[0006] In a first aspect, the present invention provides a nano-ammonium paratungstate, wherein the nano-ammonium paratungstate has a spherical or near-spherical morphology and a particle size of 20-100 nm.
[0007] Preferably, the nano-ammonium paratungstate has 4 or 10 water molecules of crystallization.
[0008] Secondly, the present invention provides a method for preparing nano-ammonium paratungstate, comprising the following steps: Step 1: Add ammonium tungstate solution dropwise to the acid solution to obtain a mixed slurry. Stop adding ammonium tungstate solution when the pH of the mixed slurry reaches 5-8. Step 2: Heat and keep the mixed slurry warm, then centrifuge and filter to obtain solid particles, which are nano-ammonium paratungstate.
[0009] Preferably, the dropping rate of the ammonium tungstate solution is 2~50 mL / min.
[0010] Preferably, the acid solution is any one or more of hydrochloric acid solution, nitric acid solution, and sulfuric acid solution.
[0011] Preferably, when hydrochloric acid solution is used as the acid solution, the concentration of the acid solution is 10-38 wt%; when sulfuric acid solution is used as the acid solution, the concentration of the acid solution is 10-98 wt%; and when nitric acid solution is used as the acid solution, the concentration of the acid solution is 10-68 wt%.
[0012] Preferably, the concentration of ammonium tungstate is 50~300 g / L.
[0013] Preferably, the ammonium tungstate solution contains ammonium tungstate and the acid solution contains H+. + The molar ratio is 1:1~2.
[0014] Preferably, in step 2, the heating temperature is 25~100℃ and the holding time is 15min~20h.
[0015] Compared with the prior art, the present invention has the following significant advantages: (1) The present invention provides a nano-sized ammonium paratungstate product with high specific surface area, excellent catalytic activity and thermal stability.
[0016] (2) The present invention realizes a process for preparing nano-ammonium paratungstate products through a simple crystallization process. The process is simple and the operation is controllable. Attached Figure Description
[0017] Figure 1 These are the XRD and SEM images of the nano-ammonium paratungstate product obtained in Example 1; Figure 2 These are the XRD and SEM images of the nano-ammonium paratungstate product obtained in Example 2; Figure 3 These are the XRD and SEM images of the nano-ammonium paratungstate product obtained in Example 3; Figure 4 These are the XRD and SEM images of the nano-ammonium paratungstate product obtained in Example 4; Figure 5 These are the XRD and SEM images of the nano-ammonium paratungstate product obtained in Example 5; Figure 6 The image shows the SEM image of ammonium tungstate prepared in Comparative Example 1. Figure 7 The image shows the SEM image of ammonium tungstate prepared in Comparative Example 2. Detailed Implementation
[0018] The present invention provides the following specific technical solutions.
[0019] In a first aspect, the present invention provides a nano-ammonium paratungstate, wherein the nano-ammonium paratungstate has a spherical or near-spherical morphology and a particle size of 20-100 nm.
[0020] The inventors provided nanoscale ammonium paratungstate products with high specific surface area, excellent catalytic activity, and thermal stability.
[0021] Preferably, the nano-ammonium paratungstate has 4 or 10 water molecules of crystallization.
[0022] During the preparation process, the number of water molecules in ammonium paratungstate can be controlled by adjusting the crystallization temperature. The number of water molecules (decahydrate or tetrahydrate) is related to the crystallization temperature. When the crystallization temperature is below 55℃, ammonium paratungstate has ten water molecules, while when the crystallization temperature is above 60℃, it has four water molecules.
[0023] Secondly, the present invention provides a method for preparing nano-ammonium paratungstate, comprising the following steps: Step 1: Add ammonium tungstate solution dropwise to the acid solution to obtain a mixed slurry. Stop adding ammonium tungstate solution when the pH of the mixed slurry reaches 5-8. Step 2: Heat and keep the mixed slurry warm, then centrifuge and filter to obtain solid particles, which are nano-ammonium paratungstate.
[0024] The inventors have developed a simple and easily controllable method for preparing nano-ammonium paratungstate. Compared to existing technologies, this process employs a neutralization crystallization method and controls the mixing process. Ammonium tungstate is gradually added dropwise to an acid solution, causing the pH of the system to gradually increase. The transformation of polytungstate ions is as follows: when tungstate ions in the ammonium tungstate solution are added to the acid solution, the system is initially acid-excessive, resulting in a very low pH (<1). This leads to the rapid and direct formation of solid tungstate. Due to the rapid acid-base neutralization rate and high supersaturation of tungstate, the nucleation rate is very fast, resulting in very fine tungstate particles, reaching the nanoscale. As the ammonium tungstate solution is further added, the pH increases, and the tungstate gradually transforms into the ammonium paratungstate product. This direct solid-phase transformation has minimal impact on particle size, thus the particle size of the ammonium paratungstate product can also reach the nanoscale. The nucleation rate of ammonium paratungstate is significantly increased. Combined with uniform nucleation under low supersaturation and precise control of crystal nucleus size, pH range and low heating crystallization temperature, the entire process from crystal nucleus formation to crystal growth suppresses excessive growth and agglomeration of particles, and finally obtains nano-sized ammonium paratungstate.
[0025] Preferably, the acid solution is any one or more of hydrochloric acid solution, nitric acid solution, and sulfuric acid solution.
[0026] Preferably, when hydrochloric acid solution is used as the acid solution, the concentration of the acid solution is 10-38 wt%; when sulfuric acid solution is used as the acid solution, the concentration of the acid solution is 10-98 wt%; and when nitric acid solution is used as the acid solution, the concentration of the acid solution is 10-68 wt%.
[0027] In practical applications, when the acid solution is hydrochloric acid, the concentration can be 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, or 38wt%; when the acid solution is sulfuric acid, the concentration can be 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, 90wt%, 95wt%, or 98wt%; and when the acid solution is nitric acid, the concentration can be 10wt%, 20wt%, 30wt%, 40wt%, 50wt%, 60wt%, or 68wt%.
[0028] Preferably, the concentration of ammonium tungstate is 50~300 g / L.
[0029] Preferably, the ammonium tungstate solution contains ammonium tungstate and the acid solution contains H+. + The molar ratio is 1:1~2.
[0030] Preferably, the crystallization temperature is 25~100℃ and the crystallization time is 15min~20h.
[0031] To make the technical problems, technical solutions and technical advantages of the present invention clearer, a detailed description will be given below with reference to specific examples. However, the scope of protection of the present invention is not limited to the following specific embodiments.
[0032] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.
[0033] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.
[0034] It should be noted that the ammonium tungstate solution used in the actual experiment of this invention contains additional ammonia. The amount of additional ammonia depends on the preparation process, purification level and storage conditions of the ammonium tungstate, and varies in different scenarios. The endpoint of the titration in this invention is determined by the pH value of the mixed solution.
[0035] Example 1: A method for preparing nano-ammonium paratungstate involves slowly adding 50 mL of a 200 g / L ammonium tungstate solution dropwise to 5 mL of a 38 wt% hydrochloric acid solution at a dropping rate of 10 mL / min to obtain a mixed solution. The pH value of the mixed solution is monitored simultaneously during the addition process, and the final pH value is 5.88. The mixed solution is then crystallized at 25°C for 5 hours, followed by centrifugation and filtration. The resulting solid particles are the nano-ammonium paratungstate product.
[0036] Figure 1 These are the XRD and SEM images of the nano-ammonium paratungstate product obtained in Example 1. Figure 1 The left side shows the XRD pattern, which indicates that the nano-ammonium paratungstate product is ammonium paratungstate decahydrate. Figure 1 The right side of the image shows an SEM image, which reveals that the nano-ammonium paratungstate product has a spherical or near-spherical morphology with a particle size of <100nm.
[0037] Example 2: A method for preparing nano-ammonium paratungstate involves slowly adding 35 mL of a 300 g / L ammonium tungstate solution dropwise to 8 mL of a 34 wt% nitric acid solution at a dropping rate of 50 mL / min to obtain a mixed solution. The pH value of the mixed solution is monitored simultaneously during the addition process, and the final pH value is 7.76. The mixed solution is then crystallized at 40°C for 15 min, followed by centrifugation and filtration. The resulting solid particles are the nano-ammonium paratungstate product.
[0038] Figure 2 These are the XRD and SEM images of the nano-ammonium paratungstate product obtained in Example 2. Figure 2 The left side shows the XRD pattern, which indicates that the nano-ammonium paratungstate product is ammonium paratungstate decahydrate. Figure 2 The right side of the image shows an SEM image, which reveals that the nano-ammonium paratungstate product has a spherical or near-spherical morphology with a particle size of <100nm.
[0039] Example 3: A method for preparing nano-ammonium paratungstate involves slowly adding 300 mL of a 100 g / L ammonium tungstate solution dropwise to 5 mL of a 98 wt% sulfuric acid solution at a dropping rate of 25 mL / min to obtain a mixed solution. The pH value of the mixed solution is monitored simultaneously during the addition process, and the final pH value of the mixed solution is 6.54. The mixed solution is then crystallized at 55°C for 1 hour, followed by centrifugation and filtration. The resulting solid particles are the nano-ammonium paratungstate product.
[0040] Figure 3 These are the XRD and SEM images of the nano-ammonium paratungstate product obtained in Example 3. Figure 3The left side shows the XRD pattern, which indicates that the nano-ammonium paratungstate product is ammonium paratungstate decahydrate. Figure 3 The right side of the image shows an SEM image, which reveals that the nano-ammonium paratungstate product has a spherical or near-spherical morphology with a particle size of <100nm.
[0041] Example 4: A method for preparing nano-ammonium paratungstate involves slowly adding 210 mL of a 50 g / L ammonium tungstate solution dropwise to 10 mL of a 19 wt% hydrochloric acid solution at a dropping rate of 40 mL / min to obtain a mixed solution. The pH value of the mixed solution is monitored simultaneously during the addition process, and the final pH value is 7.35. The mixed solution is then crystallized at 75°C for 10 hours, followed by centrifugation and filtration. The resulting solid particles are the nano-ammonium paratungstate product.
[0042] Figure 4 These are the XRD and SEM images of the nano-ammonium paratungstate product obtained in Example 4. Figure 4 The left side shows the XRD pattern, which indicates that the nano-ammonium paratungstate product is ammonium paratungstate tetrahydrate. Figure 4 The right side of the image shows an SEM image, which reveals that the nano-ammonium paratungstate product has a spherical or near-spherical morphology with a particle size of <100nm.
[0043] Example 5: A method for preparing nano-ammonium paratungstate involves slowly adding 200 mL of a 150 g / L ammonium tungstate solution dropwise to 10 mL of a 49 wt% sulfuric acid solution at a dropping rate of 15 mL / min to obtain a mixed solution. The pH value of the mixed solution is monitored simultaneously during the addition process, and the final pH value is 6.94. The mixed solution is then crystallized at 100℃ for 20 hours, followed by centrifugation and filtration. The resulting solid particles are the nano-ammonium paratungstate product.
[0044] Figure 5 These are the XRD and SEM images of the nano-ammonium paratungstate product obtained in Example 5. Figure 5 The left side shows the XRD pattern, which indicates that the nano-ammonium paratungstate product is ammonium paratungstate tetrahydrate. Figure 5 The right side of the image shows an SEM image, which reveals that the nano-ammonium paratungstate product has a spherical or near-spherical morphology with a particle size of <100nm.
[0045] Comparative Example 1: A method for preparing nano-ammonium paratungstate involves directly pouring a 38wt% hydrochloric acid solution into 50mL of a 200g / L ammonium tungstate solution and mixing them thoroughly to obtain a mixed solution with a pH of 5.88. The mixed solution is then crystallized at 25℃ for 5 hours, followed by centrifugation and filtration. The resulting solid particles are the ammonium paratungstate product.
[0046] Figure 6 The image shows a SEM image of ammonium tungstate prepared in Comparative Example 1. Figure 6 It can be seen that the ammonium paratungstate particles prepared in Comparative Example 1 are rod-shaped or needle-shaped, with a particle size in the micrometer range.
[0047] contrast Figure 1 and Figure 6 This confirms that the preparation process provided by the present invention can produce nanoscale ammonium paratungstate products.
[0048] Comparative Example 2: A method for preparing nano-ammonium paratungstate involves slowly adding a 38 wt% hydrochloric acid solution dropwise to a 200 g / L ammonium tungstate solution at a drop rate of 10 mL / min to obtain a mixed solution. The pH value of the mixed solution is monitored simultaneously during the addition process, and the final pH value is 5.88. The mixed solution is then crystallized at 25°C for 5 hours, followed by centrifugation and filtration. The resulting solid particles are the nano-ammonium paratungstate product.
[0049] Figure 7 The image shows a SEM image of ammonium tungstate prepared in Comparative Example 2. Figure 7 It can be seen that most of the ammonium paratungstate particles prepared in Comparative Example 2 are rod-shaped, with a particle size in the micrometer range.
[0050] The above-described embodiments are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope of the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. An ammonium paratungstate nanomaterial, characterized in that, The nano-ammonium paratungstate has a spherical or spherical-like shape, and a particle size of 20-100 nm.
2. The nano-ammonium paratungstate according to claim 1, wherein, The nano-ammonium paratungstate has a number of crystal water of 4 or 10.
3. A method for preparing nano-ammonium paratungstate, characterized in that, The method comprises the following steps: Step 1, drop the ammonium tungstate solution into the acid solution to obtain a mixed slurry, and stop adding the ammonium tungstate solution when the pH value of the mixed slurry reaches 5-8; Step 2, heat and incubate the mixed slurry, then centrifuge and filter, and the obtained solid particles are the nano-ammonium paratungstate.
4. The method for preparing nano-ammonium paratungstate as described in claim 3, characterized in that, The drop rate of the ammonium tungstate solution is 2-50 mL / min.
5. The method for preparing nano-ammonium paratungstate as described in claim 3, characterized in that, The acid solution is any one or two or more of a hydrochloric acid solution, a nitric acid solution and a sulfuric acid solution.
6. The method for preparing nano-ammonium paratungstate as described in claim 5, characterized in that, When the acid solution is the hydrochloric acid solution, the concentration of the acid solution is 10-38 wt%; when the acid is the sulfuric acid solution, the concentration of the acid solution is 10-98 wt%; and when the acid solution is the nitric acid solution, the concentration of the acid solution is 10-68 wt%.
7. The method for preparing nano-ammonium paratungstate as described in claim 3, characterized in that, The concentration of the ammonium tungstate solution is 50-300 g / L.
8. The method for preparing nano-ammonium paratungstate as described in claim 3, characterized in that, Ammonium tungstate in the ammonium tungstate solution and H + at a molar ratio of 1 : 1 ~ 2.
9. The method for preparing nano-ammonium paratungstate as described in claim 3, characterized in that, In step 2, the heating temperature is 25-100℃, and the incubation time is 15 min-20 h.