Method for preparing superfine high-purity germanium dioxide from germanium tetrachloride

Abstract

The invention discloses a method for preparing superfine high-purity germanium dioxide from germanium tetrachloride. The method comprises the following steps: step 1, preparing a reactor; step 2, preparing hydrolysis mother liquor; step 3, hydrolysis; step 4, suction filtration and washing; step 5, drying; and step 6, screening. According to the method for preparing the superfine high-purity germanium dioxide, the production efficiency of the superfine high-purity germanium dioxide can be effectively improved, and the superfine high-purity germanium dioxide is efficiently prepared by controlling the hydrolysis ratio, the acidity of hydrolysate, the germanium content, the temperature of the whole hydrolysis process, the hydrolysis rate and the stirring power.

Description

Technical Field

[0001] The invention belongs to the technical field of high-purity germanium material production technology, and in particular relates to a method for preparing ultrafine high-purity germanium dioxide by using germanium tetrachloride. Background Art

[0002] Ultrafine germanium dioxide is widely used in the production of germanium compounds, chemical catalysts and pharmaceutical industries, and as raw materials for PET resins.

[0003] Germanium tetrachloride: colorless, transparent liquid, boiling point 83.1°C, highly volatile, density 1.88 g / mL, insoluble in concentrated hydrochloric acid, soluble in dilute hydrochloric acid and most organic solvents such as benzene, low toxicity, hazard mark 20 (acidic corrosive), health hazards include irritation to the upper respiratory tract and skin, and can cause bronchitis and pneumonia.

[0004] Germanium tetrachloride will undergo hydrolysis reaction when it comes into contact with water, releasing a large amount of heat and generating germanium dioxide and hydrochloric acid. The chemical reaction equation is as follows: GeCl4+2H20= GeO2+4HCl Summary of the Invention

[0005] The present invention provides a method for preparing ultrafine high-purity germanium dioxide using germanium tetrachloride as a raw material, comprising the following steps: Step 1: Add a large amount of ice-water mixture around the reactor to control the initial temperature of the hydrolysis reaction below 5°C; Step 2: Prepare a hydrolysis mother liquor by performing normal hydrolysis of germanium tetrachloride. Take the filtered liquid as the hydrolysis mother liquor, and ensure that the acidity of the hydrolysis mother liquor is below 2 mol / L. This hydrolysis mother liquor can be recycled repeatedly, and the specific number of uses depends on the acidity of the mother liquor and the germanium content. Step 3: hydrolysis. Germanium tetrachloride is pumped into a hydrolysis mother liquor. The hydrolysis volume ratio of germanium tetrachloride to the hydrolysis mother liquor is adjusted. The hydrolysis ratio is determined according to the particle size requirement of the prepared germanium dioxide. The hydrolysis volume ratio is set at 1:7-1:42, i.e., 1 volume of germanium tetrachloride is hydrolyzed with at least 7 volumes to 42 volumes of hydrolysis mother liquor, and the stirring speed is 200 r / min-400 r / min; Step 4: filtration and washing: the germanium dioxide obtained by hydrolysis is vacuum filtered and washed; Step 5: drying, using a microwave oven to dry the germanium dioxide; Step six: screening. The obtained germanium dioxide is screened on an ultrasonic screening machine using a screen with corresponding aperture according to different particle size requirements.

[0006] Furthermore, when preparing the hydrolysis mother liquor, normal hydrolysis of germanium tetrachloride is performed using ultrapure water with a resistivity greater than or equal to 18 MΩcm. The acidity of the hydrolysis mother liquor is less than 2 mol / L, and the germanium content is less than 3.5 g / L. This hydrolysis mother liquor can be recycled repeatedly, with the specific number of uses depending on the acidity and germanium content of the mother liquor. The solubility of germanium tetrachloride in pure water is different from that in an acidic solution containing germanium, which in turn affects the direct yield and particle size of germanium dioxide.

[0007] Furthermore, during the hydrolysis process, the temperature is controlled not to exceed 5°C.

[0008] Furthermore, germanium tetrachloride was pumped into the hydrolysis mother liquor at a rate of 50 mL / h.

[0009] Furthermore, during washing, 200 mL of pure water was used each time, and the number of washing times was 3 times.

[0010] Furthermore, during screening, the obtained germanium dioxide is screened on an ultrasonic screening machine using a screen with corresponding aperture according to different particle size requirements, the undersize fraction is taken as the product, and the oversize fraction is returned to the production section.

[0011] The above-mentioned technical solution of the present invention has the following beneficial technical effects: the ultrafine high-purity germanium dioxide prepared by this method can effectively improve the production efficiency of ultrafine high-purity germanium dioxide, and by regulating the hydrolysis ratio, acidity and germanium content of the hydrolysis mother liquor, the temperature of the entire hydrolysis process, the hydrolysis rate and the stirring power, ultrafine high-purity germanium dioxide can be efficiently prepared. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a process flow chart for preparing ultrafine high-purity germanium dioxide using germanium tetrachloride. DETAILED DESCRIPTION

[0013] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present invention.

[0014] like Figure 1 As shown, a method for preparing ultrafine high-purity germanium dioxide from germanium tetrachloride is provided, comprising the following steps: Step 1: Add a large amount of ice-water mixture around the reactor to control the initial temperature of the hydrolysis reaction below 5°C; Step 2: preparing a hydrolysis mother liquor, performing normal hydrolysis of germanium tetrachloride, taking the filtered liquid as the hydrolysis mother liquor, and ensuring that the acidity of the hydrolysis mother liquor is below 2 mol / L; Step 3: hydrolysis, pumping germanium tetrachloride into the hydrolysis mother liquor for hydrolysis, adjusting the hydrolysis volume ratio of germanium tetrachloride to the hydrolysis mother liquor, and determining the hydrolysis ratio according to the particle size requirement of the prepared germanium dioxide. The hydrolysis ratio is set to 1:7-1:42, and the stirring rate is 200 r / min-400 r / min for hydrolysis; Step 4: filtration, washing, and vacuum filtration and washing of the hydrolyzed germanium dioxide; Step 5: Drying: using a microwave oven to dry the high-purity germanium dioxide; Step six: screening. The obtained high-purity germanium dioxide is screened on an ultrasonic screening machine using a screen with corresponding aperture according to different particle size requirements.

[0015] The ratio of germanium tetrachloride to hydrolysis mother liquor is set at 1:7-1:42. Theoretically, the larger the hydrolysis ratio, the lower the direct yield of germanium dioxide, which increases the subsequent germanium recovery cost. The smaller the hydrolysis ratio, the higher the direct yield of germanium dioxide, but it affects the size of germanium dioxide particles, which is not conducive to particle size control. Therefore, the larger or smaller the hydrolysis ratio is, the better. There is a certain ratio requirement. Table 1 shows the effect of different hydrolysis mother liquor ratios on particle size.

[0016] Table 1 Effect of different hydrolysis mother liquor ratios on particle size Hydrolysis ratio (germanium tetrachloride: hydrolysis mother liquor) Output germanium dioxide particle size um (D90) 1:7 52.93 1:9 45.76 1:14 38.57 1:21 30.25 1:28 24.60 1：28 19.61 1：35 11.65 1:42 8.13 The entire hydrolysis process requires continuous stirring of the liquid. The stirring frequency should not be too high or too low. If it is too low, the germanium dioxide cannot be evenly dispersed. If the stirring frequency is too high, the germanium dioxide crystals will not have the opportunity to grow again, which will affect the particle size of the germanium dioxide. From the current experimental data, it can be roughly concluded that the stirring frequency of a 50 Hz electric stirrer is more suitable for 200r / min-400r / min. Table 2 shows the effect of different stirring frequencies on particle size.

[0017] Table 2 Effect of different stirring frequencies on particle size Stirring frequency Output germanium dioxide particle size um (D90) Magnetic stirring 35.62 100 r / min (propeller stirring) 34.23 150r / min (propeller stirring) 30.51 200r / min (propeller stirring) 25.90 250r / min (propeller stirring) 20.46 320r / min (propeller stirring) 15.76 380r / min (propeller stirring) 13.65 420r / min (propeller stirring) 12.46 490r / min or above (propeller stirring) Liquid splashes out of the reactor during stirring To prepare the mother hydrolysis solution, normal germanium tetrachloride hydrolysis is performed using water with a resistivity greater than or equal to 18 MΩcm. The acidity of the mother hydrolysis solution is below 2 mol / L, and the germanium content is less than 3.5 g / L. This is due to the difference in solubility of germanium tetrachloride in pure water and in acidic solutions containing germanium, which directly affects the direct yield and particle size of germanium dioxide.

[0018] During the hydrolysis process, the temperature should be kept below 5°C. The hydrolysis reaction of germanium tetrachloride is essentially a chemical reaction between germanium tetrachloride and water, releasing heat and forming a dilute acid solution containing germanium dioxide. This is referred to as the hydrolysis reaction. The chemical reaction equation is as follows: GeCl₄ + 2H₂O = GeO₂ + 4HCl. This reaction is exothermic, releasing heat as the hydrolysis proceeds. The temperature of the germanium dioxide solution increases as the hydrolysis progresses. This temperature increase significantly affects the particle size of the germanium dioxide, so strict temperature control is required throughout the process. Temperature control requires two key aspects. First, the temperature of the hydrolysis mother liquor must be strictly controlled, ideally at 0°C. Second, although the temperature of the hydrolysis mother liquor is controlled, the hydrolysis process is a continuously exothermic process, which inevitably releases heat and raises the temperature of the entire hydrolysis solution. Therefore, cooling measures must be employed to control the temperature throughout the hydrolysis process, ideally keeping the temperature below 5°C throughout the entire process. Table 3 shows the effects of different hydrolysis water temperatures and temperature control throughout the hydrolysis process on particle size.

[0019] Table 3 Effects of different hydrolysis water temperatures and temperature control during the entire hydrolysis process on particle size Hydrolysis water temperature (℃) Hydrolysis process temperature (℃) Output germanium dioxide particle size um (D90) 20 Normal temperature water bath 55.65 15 Normal temperature water bath 50.26 5 Normal temperature water bath 39.66 0-2 Normal temperature water bath 20.86 20 ice water bath 35.65 15 ice water bath 25.55 5 ice water bath 14.14 2 ice water bath 13.96 Ice-water mixture (0°C or close to 0°C) ice water bath 10.86 Liquid germanium tetrachloride is pumped into the hydrolysis mother liquor at a rate of 50 mL / h. Conventional hydrolysis processes for preparing germanium dioxide do not require a high hydrolysis rate. However, for the preparation of nano-scale germanium dioxide, the hydrolysis rate must be strictly controlled. A high rate results in larger germanium dioxide particle size, but a lower rate is not necessarily better. The entire hydrolysis process is accompanied by stirring with an electric stirrer. Hydrolysis is the process by which germanium tetrachloride is converted into germanium dioxide, and it is also the process by which the already formed germanium dioxide crystals continue to grow. A too low hydrolysis rate gives the already formed germanium dioxide crystals too much time to grow and develop, thereby affecting the particle size of the germanium dioxide. Therefore, the hydrolysis rate is also a key control point in the entire hydrolysis process.

[0020] During washing, 200 mL of pure water was used for every 25 mL of germanium tetrachloride raw material. Germanium tetrachloride is hydrolyzed to produce a dilute acid solution of germanium dioxide. This acidic solution contains a high chloride ion content, and washing is required to remove some of the chloride ions to meet the usage requirements. From the perspective of the washing process, the washing water is pure water, and the control indicator is: resistivity ≥18 MΩ.cm. The number of washes and water consumption are basically inversely proportional to the final chloride ion content of the germanium dioxide. The specific water consumption and number of washes need to be controlled based on the chloride ion index requirements of the output germanium dioxide product. If the chloride ion content requirement is low, the water consumption and number of washes can be increased. It should be noted that increasing the number of washes and water consumption will affect the direct yield of germanium dioxide. Germanium is also lost along with the washing liquid, increasing the subsequent recovery cost. Table 4 shows the effect of the wash water amount on chloride ions and product direct yield.

[0021] Table 4 shows the effect of washing water volume on chloride ion and product direct yield Germanium tetrachloride raw material Pure water washing volume (ml) <![CDATA[Output germanium dioxide Cl - %]]> Output germanium dioxide direct yield% Output germanium dioxide particle size um (D90) 25ml Unwashed 0.098 92.56 32.55 25ml 200 0.041 85.56 14.15 25ml 400 0.023 74.23 12.35 25ml 500 0.017 61.44 10.25 When drying in a microwave oven or conventional electric blast drying oven, it is important to ensure that the equipment is kept clean to prevent the introduction of other contaminants into the germanium dioxide during the drying process. You can also cover the dried product with filter paper. Since the entire hydrolysis process takes place at low temperatures, the filtered germanium dioxide is still at a low temperature. Initial drying should be performed at a low temperature to avoid excessive temperature differences between the germanium dioxide surface and the drying equipment, which could cause sample splashing.

[0022] During screening, the obtained germanium dioxide is screened on an ultrasonic screening machine using corresponding sieves according to different particle size requirements. The part under the sieve is taken as the product, and the part above the sieve is returned to the production section. Before screening, the particle size can also be tested using a particle size analyzer using a wet analysis method.

[0023] The current existing process generally uses the hydrolysis of germanium tetrachloride to prepare germanium dioxide. That is, germanium tetrachloride and water undergo a chemical reaction, releasing heat at the same time to form germanium dioxide and hydrochloric acid. The chemical reaction equation is as follows: GeCl4+2H20=GeO2+4HCl. The main parameters and indicators of this process are germanium tetrachloride raw material, pure water, stirring system, cooling system, filtration system, and drying system. This process is also a common method for preparing germanium dioxide on the market. The particle size of the germanium dioxide prepared by this process is generally D90:46 -50um, purity of Ge: 99.9992%. With the development of science and technology, germanium dioxide of ordinary particle size and purity can no longer meet the demand for ultrafine germanium dioxide in aerospace, specific medical fields and certain chemical fields. The continuous improvement of the application demand for ultrafine high-purity germanium dioxide has prompted the urgent development of nano-level high-purity germanium dioxide production technology. The present invention does not change the process of classic germanium dioxide preparation, but adjusts each hydrolysis parameter and technical index one by one, especially introduces the mother liquor of conventional hydrolysis process as the "hydrolysis water" of this invention. Compared with using conventional laboratory pure water as hydrolysis water, this invention greatly improves the direct yield of germanium dioxide, and effectively solves the contradiction that the greater the proportion of hydrolysis water, the lower the direct yield of the product, which cannot be taken into account at the same time. The entire invention process continuously optimizes and adjusts the ratio of hydrolysis water and germanium tetrachloride, strictly controls the hydrolysis water and hydrolysis process temperature, as well as the stirring rate and hydrolysis rate on the basis of the existing process, and introduces an ultrasonic screening system for targeted screening of the required particle size. The germanium dioxide obtained through the entire invention has a qualitative leap in particle size from the original micron level to the nanometer level (below 10um), and has also made a great step forward in purity, from 99.9992% that can be achieved by conventional processes to 99.9997%. At the same time, it solves the problem of low product direct yield caused by the increase in the hydrolysis ratio when using pure water as hydrolysis water. This invention increases the direct yield of ultrafine germanium dioxide from 35.25% to 78.89%, effectively solving the problem of increased subsequent recovery costs of germanium dioxide due to low product direct yield.

[0024] The following is a comparison of the particle size, purity, and direct yield of germanium dioxide produced by conventional processes and high-purity germanium dioxide produced by this invention process; High-purity metallic germanium produced by processing ultrafine high-purity germanium dioxide has broad and important application prospects in semiconductors, aerospace measurement and control, nuclear physics detection, fiber optic communications, infrared optics, solar cells, chemical catalysts, biomedicine and other fields.

[0025] It should be understood that the above-described specific embodiments of the present invention are merely illustrative or illustrative of the principles of the present invention and do not constitute limitations of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included within the scope of protection of the present invention. In addition, the appended claims are intended to cover all variations and modifications that fall within the scope and metes and bounds of the appended claims, or equivalents thereof.

Claims

1. A method for preparing ultrafine high-purity germanium dioxide from germanium tetrachloride, characterized in that: The following steps are involved: Step 1: Add a large amount of ice-water mixture around the hydrolysis reactor to control the initial temperature of the hydrolysis reaction below 5°C; Step 2: preparing a hydrolysis mother liquor, performing normal hydrolysis of high-purity germanium tetrachloride, taking the filtered liquid as the hydrolysis mother liquor, and ensuring that the acidity of the hydrolysis mother liquor is below 2 mol / L; Step 3: hydrolysis, pumping germanium tetrachloride into the hydrolysis mother liquor, adjusting the hydrolysis volume ratio of germanium tetrachloride to the hydrolysis mother liquor, and determining the hydrolysis volume ratio according to the particle size requirement of the prepared high-purity germanium dioxide. The hydrolysis ratio is set to 1:7-1:42, and the stirring rate is 200 r / min-400 r / min for hydrolysis; Step 4: filtration and washing: vacuum filtration and washing the high-purity germanium dioxide obtained by hydrolysis; Step 5: drying, using a microwave oven to dry the germanium dioxide; Step six: screening. The obtained high-purity germanium dioxide is screened on an ultrasonic screening machine using a screen with corresponding aperture according to different particle size requirements.

2. The method for preparing ultrafine high-purity germanium dioxide from germanium tetrachloride according to claim 1, wherein: When preparing the hydrolysis mother liquor, normal germanium tetrachloride hydrolysis is performed, ultrapure water with a resistivity greater than or equal to 18 MΩcm is used, the acidity of the hydrolysis mother liquor is less than 2 mol / L, and the germanium content is less than 3.5 g / L.

3. The method for preparing ultrafine high-purity germanium dioxide from germanium tetrachloride according to claim 1, wherein: During the hydrolysis process, the temperature of the hydrolysis reaction is controlled not to exceed 5°C.

4. The method for preparing ultrafine high-purity germanium dioxide from germanium tetrachloride according to claim 1, wherein: The speed of pumping germanium tetrachloride into the hydrolysis mother liquor is 50 mL / h.

5. The method for preparing ultrafine high-purity germanium dioxide from germanium tetrachloride according to claim 1, wherein: During the washing, 200 mL of pure water was used to wash the high-purity germanium dioxide each time, and the washing times were 3 times.

6. The method for preparing ultrafine high-purity germanium dioxide from germanium tetrachloride according to claim 1, characterized in that: During the screening, the obtained germanium dioxide is screened on an ultrasonic screening machine using a screen with corresponding aperture according to different particle size requirements, the undersize fraction is taken as the product, and the oversize fraction is returned to the production section.

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