A method for directly preparing germanium tetrachloride from tannic acid germanium

Abstract

The application discloses a method for directly preparing germanium tetrachloride from tannin germanium, which comprises the following steps: under the protection of an inert gas atmosphere, directly chlorinating dry tannin germanium with a chlorinating agent at a reaction temperature of 200-350 DEG C, capturing a gas phase product and separating and purifying the gas phase product to obtain germanium tetrachloride. The application omits a traditional calcination step, greatly shortens a reaction period, simplifies a preparation process, reduces equipment investment and operation cost, improves the yield and purity of germanium tetrachloride, realizes the goals of energy saving and consumption reduction, pollution reduction, process shortening and improved germanium recovery rate, and has the advantages of simple process, high efficiency and economy and easy industrial application.

Description

Technical Field

[0001] This invention belongs to the fields of rare and dispersed metal recovery, germanium chemistry and hydrometallurgy, and specifically relates to a method for directly preparing germanium tetrachloride from germanium tannic acid. Background Technology

[0002] In today's digital information age, optical fiber communication, as a key supporting technology for information transmission, has become the core architecture of modern communication networks due to its superior transmission speed, ultra-large transmission capacity, and extremely low signal loss. Optical fiber preforms, as the core raw material for manufacturing optical fibers, have seen their production scale continuously expand with the rapid development of the optical fiber communication market.

[0003] Germanium is an important strategic rare metal that plays an indispensable role in the production of optical fiber preforms and is widely used in infrared optics, optical fiber communication, semiconductors, solar cells, and catalysts. Currently, the classic industrial process for extracting germanium from germanium-containing raw materials (such as zinc leaching residue and fly ash) is as follows: enrichment → leaching → precipitation (commonly using tannic acid to precipitate germanium tannate) → calcination (calcination temperature is approximately 500-550℃, converting germanium tannate to germanium dioxide) → chlorination roasting with chlorinating agent (to obtain GeCl4) → distillation purification → hydrolysis (to obtain GeO2) → hydrogen reduction (to obtain metallic germanium).

[0004] This traditional process has the following obvious drawbacks: (1) High energy consumption: The high-temperature calcination of germanium tannin and the chlorination distillation process involve multiple high-temperature operations (calcination furnace, chlorination distillation furnace, reduction furnace), and require a large amount of energy; the subsequent distillation purification process is also an energy-intensive operation.

[0005] (2) Heavy environmental pollution: A large amount of "three wastes" will be generated during the calcination process, which are difficult to treat and are not environmentally friendly.

[0006] (3) The germanium recovery rate is relatively low: After undergoing multiple independent unit operations such as calcination and chlorination, germanium tannin contains a large number of organic groups. Its calcination residue and chlorinating agent preferentially undergo side reactions, resulting in low purity of the target product germanium tetrachloride and difficulty in separation, thus reducing the direct recovery rate of germanium.

[0007] (4) Highly corrosive to equipment and high maintenance costs: The entire process uses a large amount of highly corrosive media such as concentrated sulfuric acid, chlorine, and hydrochloric acid, and is carried out in a high temperature and high pressure environment, resulting in rapid equipment depreciation and high maintenance and replacement frequency.

[0008] Therefore, there is an urgent need in this field to develop an innovative method for the direct preparation of germanium products from germanium tannic acid that is short in process, low in energy consumption, environmentally friendly, and has a high recovery rate. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a method for directly preparing germanium tetrachloride from germanium tannic acid that has a short process, low energy consumption, environmental friendliness and high recovery rate.

[0010] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows: A method for directly preparing germanium tetrachloride from germanium tannin comprises the following steps: Under an inert gas atmosphere, dried germanium tannin was reacted directly with a chlorinating agent at a reaction temperature of 200-350°C. The gaseous products were collected, separated, and purified to obtain germanium tetrachloride. The chlorinating agent is one or more of phosphorus pentachloride, phosphorus trichloride, and phosphorus oxychloride.

[0011] As a further improvement, the germanium tannic acid is obtained from a germanium-containing solution by tannic acid precipitation.

[0012] As a further improvement, the molar ratio of germanium tannate to chlorinating agent is 1:(4~6).

[0013] As a further improvement, the temperature was increased to 200-350℃ at a heating rate of 8-15℃ / min.

[0014] As a further improvement, the reaction temperature is 280~320℃.

[0015] As a further improvement, the reaction time is 2-3 hours.

[0016] As a further improvement, the separation and purification process includes sequential condensation collection and distillation.

[0017] As a further improvement, the temperature of the condensate collection is controlled between -10 and 10°C.

[0018] As a further improvement, the distillation process is carried out at a temperature of 80~100℃ and a vacuum degree of 0.05~0.09MPa.

[0019] As a further improvement, it also includes: hydrolyzing purified germanium tetrachloride and then reducing it to obtain metallic germanium.

[0020] This invention provides a highly efficient and environmentally friendly method for extracting and refining germanium from germanium-containing materials. Using dehydrated and dried germanium tannin as raw material, it directly reacts with a specific chlorinating agent under inert gas protection. Combined with condensation collection and distillation purification, high-purity germanium tetrachloride is obtained. This method eliminates the traditional calcination step and avoids the need to convert germanium tannin into intermediate products such as germanium dioxide, significantly shortening the reaction cycle, simplifying the preparation process, and reducing equipment investment and operating costs. Furthermore, by optimizing key parameters such as reaction temperature, reaction time, and the chlorinating agent ratio, precise reaction control is achieved, improving the yield and purity of germanium tetrachloride. By combining the direct chlorination of germanium tannin with the efficient separation and purification of the product, the method achieves the goals of energy saving, pollution reduction, process shortening, and improved germanium recovery. It boasts advantages such as simple process, high efficiency and economy, and ease of industrial application.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. Breakthrough in process approach, significant advantages in environmental protection and energy consumption: This technology omits the calcination step, directly avoiding the high-temperature calcination process and significantly shortening the reaction cycle; the energy-saving effect is extremely significant, reducing energy consumption by more than 40%, and the gas generated in the reaction can be treated by condensation and alkaline absorption, greatly reducing environmental pressure.

[0022] 2. Different core reaction design: This technology achieves the direct chlorination decomposition of germanium tannate under mild conditions of 200~350℃ by optimizing the molar ratio of germanium tannate to chlorinating agent and using inert gas protection, which reduces the requirements for equipment materials and reduces equipment maintenance costs.

[0023] 3. Product flexibility: This technology directly yields the core intermediate product germanium tetrachloride, reducing material transfer and loss, improving the direct recovery rate of germanium, and easily generating a variety of high value-added products such as germanium dioxide and metallic germanium, making it highly adaptable.

[0024] 4. Innovative selection and application of chlorinating agents: This technology can use solid chlorinating agents such as phosphorus pentachloride and phosphorus trichloride, and the compatibility conditions of different chlorinating agents have been clarified, which improves the adaptability and industrial feasibility of the process. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a process flow diagram of a specific embodiment of the present invention. Detailed Implementation

[0027] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0028] 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.

[0029] 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.

[0030] In some specific implementations, such as Figure 1 The method for directly preparing germanium tetrachloride from germanium tannin of the present invention includes the following steps: Under an inert gas atmosphere, dried germanium tannate was directly chlorinated with a chlorinating agent at a reaction temperature of 200-350°C. The gaseous products were collected, separated, and purified to obtain germanium tetrachloride.

[0031] In some embodiments, the inert gas is nitrogen or argon.

[0032] In some embodiments, the germanium tannate is obtained from a germanium-containing solution by tannic acid precipitation. The aqueous germanium tannate precipitate is pretreated (dehydrated and dried) to obtain dried germanium tannate. Preferably, its water content is controlled at 5% to 15%, and the drying temperature is preferably 80 to 110°C.

[0033] In some embodiments, the chlorinating agent is a solid chlorinating agent. The solid chlorinating agent is one or more of phosphorus pentachloride (PCl5), phosphorus trichloride (PCl3), and phosphorus oxychloride (POCl3), which are more effective than chlorinating agents such as ammonium chloride, hydrochloric acid, or calcium chloride. Preferably, the molar ratio of germanium tannate to the solid chlorinating agent is 1:(4~6).

[0034] In some embodiments, the dried germanium tannate material is uniformly mixed with a solid chlorinating agent in the above proportion, and the mixture is fed into a reactor. Under the protection of an inert gas, the temperature is programmed to rise (at a heating rate of 8~15℃ / min) to 200~350℃ (preferably 280~320℃) and held at that temperature, so that the organic groups in the germanium tannate slowly decompose and undergo a direct chlorination decomposition reaction with the chlorinating agent to generate gaseous germanium tetrachloride (GeCl4), carbon monoxide (CO), carbon dioxide (CO2), and hydrogen chloride (HCl) gas.

[0035] With programmed heating and inert gas protection, at the low temperature stage, germanium tannin is pyrolyzed in an inert atmosphere to generate small molecule gas and highly dispersed active carbon. At the same time, the germanium in germanium tannin is transformed into an amorphous germanium-oxygen-carbon (Ge-OC) intermediate support that is tightly complexed with carbon. Subsequently, at the high temperature stage, this intermediate support can undergo a synergistic redox chlorination reaction with a phosphorus-containing chlorinating agent to efficiently generate germanium tetrachloride through a reduction chlorination reaction.

[0036] This invention combines the two separate steps of "thermal decomposition followed by chlorination" in traditional processes into a single, highly efficient, continuous "in-situ pyrolysis-coupled chlorination" reaction by using a specific, highly active chlorinating agent. The reaction can proceed directly at low temperatures. Crucially, the specific phosphorus-containing chlorinating agent can directly attack and break the chemical bonds surrounding germanium, lowering the activation energy and allowing the decomposition of germanium tannin and the chlorination of germanium to proceed in a coupled manner at low temperatures, without the need for prior GeO2 formation.

[0037] In some embodiments, the chlorination reaction takes 2 to 3 hours.

[0038] In some embodiments, the separation and purification include sequential condensation and collection followed by distillation. The distillation process is carried out at a temperature of 80-100°C and a vacuum of 0.05-0.09 MPa.

[0039] In some embodiments, the mixed gas produced by the reaction is discharged and first condensed and recovered in a cryogenic condenser at a temperature controlled between -10 and 10°C, so that the high-boiling-point GeCl4 is condensed into a liquid and collected. The uncondensed gases (mainly CO, CO2, HCl, and decomposition products of the chlorinating agent) enter an absorption unit (such as an alkaline absorption tower using NaOH or Ca(OH)2 solution) to absorb acidic gases (HCl, etc.), and are discharged after meeting standards. CO and CO2 can be collected or treated by combustion. The collected crude germanium tetrachloride liquid can be further purified by distillation to obtain a high-purity germanium tetrachloride product.

[0040] In some embodiments, the final germanium tetrachloride product has a purity of ≥99.99% and a yield of ≥85%.

[0041] In some embodiments, purified germanium tetrachloride is hydrolyzed with high-purity water to generate high-purity germanium dioxide (GeO2) precipitate; the germanium dioxide is then subjected to a hydrogen reduction step to obtain high-purity metallic germanium.

[0042] Example 1 A method for directly preparing germanium tetrachloride from germanium tannin, the key steps of which are as follows: (1) Raw material processing: After the germanium tannin is dehydrated and dried at 80℃, 20.0g of germanium tannin powder (germanium content analysis is 4.09%) is weighed and evenly spread in a quartz boat, and then the quartz boat is pushed into the constant temperature zone of the quartz tube furnace.

[0043] (2) Reaction conditions: Germanium tannate to phosphorus trichloride is in a molar ratio of 1:6. High-purity N2 is introduced to remove air from the pipeline and reaction tube to prevent the germanium tannate from being oxidized during the heating process. The tube furnace is heated to 300°C at a heating rate of 10°C / min to carry out a full chlorination reaction for 2 hours.

[0044] (3) Product collection: The GeCl4 vapor and by-product gas generated in the reaction are carried out of the heating zone by the carrier gas and enter the condensation device, where GeCl4 is condensed into liquid and collected.

[0045] (4) Analysis results: A pale yellow transparent liquid was obtained in the condensation and collection device. After simple distillation, the purity of the germanium tetrachloride product was 99.99%. Based on the germanium content in the raw material, the yield (conversion and recovery rate of germanium) was 85%.

[0046] Comparative Example 1 The chlorinating agent used was 37% concentrated hydrochloric acid, with an excess of 50% hydrochloric acid. The reaction temperature was 300℃, and other conditions were the same as in Example 1. The resulting germanium tetrachloride product had a purity of 73.8% and a yield of 56.3%.

[0047] Comparative Example 2 Anhydrous calcium chloride was used as the chlorinating agent. 10.0 g of germanium tannate (containing 0.025 mol Ge) was dried in an oven at 110°C for 2 hours. After cooling, it was mixed and ground with 15.0 g of anhydrous calcium chloride (containing 0.27 mol Cl, Ge:Cl molar ratio 1:10.8). The reaction temperature was 300°C, and other conditions were the same as in Example 1. The resulting germanium tetrachloride product had a purity of 89.7% and a yield of 70.3%.

[0048] Example 2 A method for directly preparing germanium tetrachloride from germanium tannin, the key steps of which are as follows: (1) Raw material processing: After the germanium tannin is dehydrated and dried at 80℃, 20.0g of germanium tannin powder (germanium content analysis is 4.09%) is weighed and evenly spread in a quartz boat, and then the quartz boat is pushed into the constant temperature zone of the quartz tube furnace.

[0049] (2) Reaction conditions: Germanium tannate to phosphorus pentachloride is in a molar ratio of 1:6. High-purity N2 is introduced to remove air from the pipeline and reaction tube to prevent the germanium tannate from being oxidized during the heating process. The tube furnace is heated to 300°C at a heating rate of 10°C / min to carry out a full chlorination reaction for 2 hours.

[0050] (3) Product collection: The GeCl4 vapor and by-product gas generated in the reaction are carried out of the heating zone by the carrier gas and enter the condensation device, where GeCl4 is condensed into liquid and collected.

[0051] (4) Analysis results: A pale yellow transparent liquid was obtained in the condensation and collection device. After simple distillation, the purity of the germanium tetrachloride product was 99.7%. Based on the germanium content in the raw material, the yield (conversion and recovery rate of germanium) was 93.4%.

[0052] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention should fall within the protection scope of the present invention.

Claims

1. A method for directly preparing germanium tetrachloride from germanium tannin, characterized in that, Includes the following steps: Under an inert gas atmosphere, dried germanium tannin was reacted directly with a chlorinating agent at a reaction temperature of 200-350°C. The gaseous products were collected, separated, and purified to obtain germanium tetrachloride. The chlorinating agent is one or more of phosphorus pentachloride, phosphorus trichloride, and phosphorus oxychloride.

2. The method for directly preparing germanium tetrachloride from germanium tannin as described in claim 1, characterized in that, The germanium tannin was obtained from a germanium-containing solution by tannin precipitation.

3. The method for directly preparing germanium tetrachloride from germanium tannin as described in claim 1, characterized in that, The molar ratio of germanium tannin to chlorinating agent is 1:(4~6).

4. The method for directly preparing germanium tetrachloride from germanium tanninate according to claim 1 or 3, characterized in that, The temperature is increased to 200-350℃ at a heating rate of 8-15℃ / min.

5. The method for directly preparing germanium tetrachloride from germanium tanninate according to claim 1 or 3, characterized in that, The reaction temperature is 280~320℃.

6. The method for directly preparing germanium tetrachloride from germanium tannin according to claim 1 or 3, characterized in that, The reaction time is 2-3 hours.

7. The method for directly preparing germanium tetrachloride from germanium tanninate according to claim 1 or 3, characterized in that, The separation and purification process includes sequential condensation collection and distillation.

8. The method for directly preparing germanium tetrachloride from germanium tannin according to claim 7, characterized in that, The temperature of the condensate collection is controlled between -10 and 10°C.

9. The method for directly preparing germanium tetrachloride from germanium tanninate according to claim 7, characterized in that, The distillation process is carried out at a temperature of 80~100℃ and a vacuum degree of 0.05~0.09MPa.

10. The method for directly preparing germanium tetrachloride from germanium tanninate according to claim 1 or 3, characterized in that, Also includes: The purified germanium tetrachloride was hydrolyzed and then reduced to obtain metallic germanium.

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