JPH0475846B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing high-purity tellurium dioxide, which is used as a material for optical single crystals and the like. [Prior art] Tellurium dioxide is generally used as a chemical, but single crystals made from high-purity tellurium dioxide of 99.999% by weight or more can be used with ultrasonic light from laser printers, color scanners, spectrum analyzers, etc. It is effective for special applications such as modulators and polarizers. Conventionally, this high-purity tellurium dioxide has been produced by heating a basic nitrate obtained by reacting concentrated nitric acid with metallic tellurium. The tellurium dioxide produced by this method has low purity, and in order to increase the purity of the product, it is not only necessary to sufficiently purify the tellurium metal used as a raw material in advance, but also to use a reagent to dissolve the tellurium metal. However, it is necessary to use highly purified products, and there is also the problem of in-process contamination due to wet treatment as a reaction step, so that the purity of the raw reagent cannot be higher than that of the raw reagent. Furthermore, in order to use it as a raw material for manufacturing optical single crystals,
The amount of adsorbed gas on tellurium dioxide must be suppressed as much as possible, and from this point of view, particles with large and stable particle sizes are desired. [Problems to be Solved by the Invention] In order to solve the above-mentioned problems, the present invention uses tellurium metal as a raw material with a purity of about 99.9% by weight, which is a normal grade, and has a particle size that guarantees a purity of 99.999% by weight or more. The object of the present invention is to provide a manufacturing method that can obtain high-purity tellurium dioxide with a large amount of tellurium dioxide. [Means for Solving the Problems] The present invention provides tellurium tetrachloride by passing dry chlorine gas into metallic tellurium of about 99.9% by weight, which is a normal grade, and distilling and refining the tellurium tetrachloride in a distiller. First, the initial distillation of tellurium tetrachloride, which accounts for 5 to 15% by weight of the treated amount, is separated and removed, and then the distillation process is carried out again, and the distillation obtained at this time is used as the main distillation to recover purified tellurium tetrachloride. The purpose is to add pure water to purified tellurium tetrachloride and hydrolyze it to produce tellurium dioxide. [Function] When distilling and refining tellurium tetrachloride in the present invention, the initial distillate, which accounts for 5 to 15% by weight of the processed amount, is separated and removed. This is because selenium, phosphorus, sulfur, arsenic, antimony, tin, gallium, etc. get mixed into the main distillation tank, and as a result, the purity of tellurium dioxide is lowered, which is contrary to the purpose of the main distillation. This is because if the proportion exceeds 15% by weight, not only the yield of the available product decreases, but also the improvement in product purity becomes less noticeable. When producing tellurium tetrachloride by passing dry chlorine gas through tellurium metal, if the supply of dry chlorine gas is insufficient, black tellurium dichloride will mix into the system, so the supply of dry chlorine gas in this process is It is necessary that the amount be sufficient for continuous production of tellurium chloride. Regarding the particle size of tellurium dioxide, the higher the temperature of the pure water used to hydrolyze purified tellurium tetrachloride and the larger the amount of liquid, the more likely it will be a coarse particle product. At room temperature, even if the amount of pure water is increased, a particle size of only a few μm can be obtained. On the other hand, when the temperature of pure water is about 60℃, the amount of pure water used to hydrolyze purified tellurium tetrachloride is increased, and if pure water is used that is about 500 times stronger than tellurium tetrachloride, the particle diameter is 7 to 12 μm.
tellurium dioxide with a particle size of approximately When the temperature of pure water is raised to 90℃, tellurium dioxide with a particle size of about 10 to 20 μm can be obtained by simply maintaining the amount of pure water for hydrolyzing purified tellurium tetrachloride at about 50 times that of tellurium tetrachloride. . If the temperature of pure water can be maintained at 95°C or higher, tellurium dioxide with a particle size of 30 to 50 μm can be obtained. Table 1 shows the relationship between the hydrolysis conditions and the particle size μm of tellurium dioxide.

〔Example〕

Example 1 450 g of sand granular metal tellurium with a purity of 99.9% by weight was placed in a heat-resistant glass boat and charged into a heat-resistant glass furnace tube having a diameter of 90 mm and a length of 2 m. After the air in the tube was replaced with nitrogen gas, the metal tellurium charging section was heated to 420° C. in a tube furnace surrounding the core tube while introducing chlorine gas into the core tube at a flow rate of 2/min. Tellurium metal is chlorinated by chlorine gas,
It evaporated as tellurium tetrachloride gas, and eventually became a yellowish-white solid that adhered to the low-temperature parts at both ends of the core tube of the tube furnace. After continuing to heat the charging portion of metallic tellurium for 3 hours, the reaction was terminated with about 60 g of residual metallic tellurium remaining in the heat-resistant glass boat. In order to collect tellurium tetrachloride, which is highly hygroscopic, work was carried out in a nitrogen atmosphere, and approximately 800 g of tellurium tetrachloride was recovered. This tellurium tetrachloride was transferred to a heat-resistant glass flask with a capacity of 1, and the distiller, which had been purged with nitrogen gas, was heated to 430°C, and distillation proceeded while keeping part of the condenser at 270°C with a ribbon heater. After distillation of tellurium tetrachloride started, heating was stopped once 75 g had been distilled, and after separating the distillate at this point as the first distillation, the distillation operation was continued again. 603g of the subsequent distillate was obtained as the main distillate. By adding 600 g of pure water to 603 g of this main fraction, a purified tellurium tetrachloride aqueous solution was obtained. Further, 100 g of the purified tellurium tetrachloride aqueous solution obtained in this manner was dropped into pure water filled in a beaker with a capacity of 5 to cause hydrolysis and to obtain tellurium dioxide. In this case, the temperature of the pure water was 90°C, and the process was continued while stirring the pure water at about 200 rpm using a Teflon rotor. The white precipitate of tellurium dioxide produced in this way is separated from the supernatant liquid by decantation, and then repulped and washed with pure water in a 5-capacity beaker until the pH reaches about 7.
The analysis results of tellurium dioxide, which was obtained by washing the repulp three times with hot water at temperatures above ℃ to ensure sufficient dechlorination and then filtering and drying, showed that copper, nickel, and magnesium were each less than 0.1 ppm. , iron is 0.1ppm, chlorine is less than 10ppm, so 99.99
It was possible to obtain tellurium dioxide of sufficiently high purity, which had a purity of at least 1% by weight. The particle size of the tellurium dioxide thus obtained was 20 to 30 μm. Example 2 1,000 g of metallic tellurium with a purity of 99.9% by weight was placed in a three-necked heat-resistant glass flask, a capillary was inserted into the side port, the mantle heater was heated to 250°C, and chlorine gas was supplied at a rate of 1.3/min. Injected in proportion. In this case, the metallic tellurium first liquefied as black tellurium dichloride. As the chlorine injection was continued, the tellurium dioxide gradually changed to tellurium tetrachloride, and eventually tellurium tetrachloride, a orange-colored liquid, was obtained. In this case, the tellurium tetrachloride still contains some tellurium dichloride, so the mantle heater should be
℃ and distilled into another flask with a chlorine stream to completely convert it into tellurium tetrachloride. The weight of the tellurium tetrachloride thus obtained was 1950 g. This tellurium tetrachloride was transferred to a distillation tower, and the inside of the distillation tower was replaced with nitrogen gas, and then the mantle heater was heated to 420°C and the condenser section was heated to about 270°C. Distillation of tellurium tetrachloride begins, 290g
When tellurium tetrachloride had been distilled out, the distillation inlet pipe was switched to separate the first distillation and the main fraction, and the subsequent distillate was used as the main distillation to recover 1450 g of tellurium tetrachloride. An equal weight of 1,450 g of pure water was added to 1,450 g of this main reservoir, and the two were thoroughly mixed to form an aqueous solution of tellurium tetrachloride. Collect 200g of this tellurium tetrachloride aqueous solution,
Tellurium dioxide was produced by hydrolyzing tellurium tetrachloride by adding it to pure water 5 at 95°C in a beaker. The analysis results of tellurium dioxide obtained in this way show that copper, nickel, and magnesium are respectively
Less than 0.1ppm, chlorine less than 10ppm, iron
At 0.1 ppm, we were able to obtain tellurium dioxide with a sufficiently high purity of over 99.999% by weight. The particle size of the tellurium dioxide thus obtained was 30 to 50 μm. [Effects of the Invention] As described above, according to the present invention, tellurium dioxide having a large particle size and a purity exceeding 99.999% by weight, which is used as a material for optical single crystals, etc., can be easily and stably obtained.

Claims (1)

[Claims] 1. Dry chlorine gas is passed through ordinary grade metal tellurium to produce tellurium tetrachloride, and when the tellurium tetrachloride is purified by distillation in a distiller, first the initial distillation of tellurium tetrachloride, which accounts for 5 to 15% by weight of the processed amount, is separated. After removing
The distillation process is carried out again, the obtained fraction is used as the main fraction, purified tellurium tetrachloride is recovered, and the purified tellurium tetrachloride is hydrolyzed with pure water to obtain tellurium dioxide. Method for producing pure tellurium dioxide.