Preparation method of high-purity metal cesium

Abstract

The invention belongs to the field of non-ferrous metal preparation, and particularly relates to a preparation method of high-purity cesium. According to the method, a specific type of inhibitor is added in the process of preparing the metal cesium through the calcium thermal reduction method, an isolating layer is formed on the metal surface, reaction alloying of rubidium and cesium generated in the reduction reaction process is prevented, in the later separation process, original fractionation equipment can be used for separating the metal rubidium, the metal cesium and the inhibitor, and the separation efficiency is improved. And the equipment cost of the existing process does not need to be increased. Particularly, phosphite esters of different sizes are matched to react with metal, molecules of different sizes are matched, the surface of the metal can be better covered, and alloying of rubidium and cesium is prevented.

Description

Technical Field

[0001] The invention belongs to the field of nonferrous metal preparation, and in particular relates to a method for preparing high-purity cesium. Background Art

[0002] With technological advancements, the application areas of high-purity cesium continue to expand, and the requirements for its purity are also increasing. Currently, the industrial production of cesium metal in China has reached a purity of 99.99% (total impurity content does not exceed 0.01%). However, in some high-end application areas, this purity standard still cannot meet the needs, and the purity needs to be increased to above 99.999%.

[0003] Metallothermic reduction is the primary method for the industrial production of cesium metal. This method uses cesium compounds (such as hydroxides, carbonates, halides, sulfates, chromates, or nitrates) as raw materials and a strongly reducing metal (including lithium, sodium, calcium, magnesium, zirconium, aluminum, or silicon) as a reducing agent. The reduction reaction proceeds at high temperatures. The entire process is carried out under an inert atmosphere, followed by vacuum distillation to separate the gaseous cesium metal from the reaction system. Under the influence of a vacuum system, the cesium vapor is transported to a condensation area, where it is condensed and collected as a liquid in a dedicated container.

[0004] The main technical route used in existing invention patents is to prepare high-purity cesium through metal thermal reduction. The boiling point of metallic calcium is much higher than that of metallic cesium. According to the principle of reaction equilibrium, after cesium vaporizes under high temperature conditions, metallic calcium will react with cesium compounds to reduce the cesium. The thermal reduction method is simple and feasible, but rubidium and cesium are both alkali metals with active chemical properties. At room temperature, the two interact slowly. At high temperatures, the two vaporize and fully mix, which also increases the speed of their interaction and forms a stable, uniform alloy phase, which is not conducive to the separation and use of rubidium and cesium metals. Summary of the Invention

[0005] Based on the technical problems existing in the background technology, the present invention proposes a method for preparing high-purity metallic cesium.

[0006] 1. A method for preparing high-purity metallic cesium, comprising the following steps: (1) Prepare raw materials: Select high-purity cesium compound powder, reducing agent, and inhibitor, and prepare them in a mass ratio of 2: (1-4): (1-2).

[0007] (2) Replace oxygen: Control the vacuum degree in the vertical vacuum furnace at 0.1 Pa, fill it with inert gas to normal pressure, then evacuate the furnace, and then fill it with inert gas. Repeat this process for more than 3 times to replace the oxygen in the vertical vacuum furnace.

[0008] (3) Mixing and heating: Place the evenly mixed cesium compound powder and metallic calcium particles into a treated vertical vacuum furnace, heat to 550-1000°C under an inert atmosphere and normal pressure, and keep warm for 30-90 minutes.

[0009] (4) Collecting products: After the pressure gauge in the vertical vacuum furnace shows an increase, turn on the vacuum pump and guide the metallic cesium vapor to the condensation part through the heated pipe connected to the inner chamber of the vertical vacuum furnace. After condensing into droplets, the droplets flow into the collector to obtain a liquid mixture, wherein the liquid mixture is liquid metallic rubidium, liquid metallic cesium and phosphite.

[0010] (5) The liquid mixture is vacuum distilled to obtain high-purity metallic rubidium, high-purity metallic cesium and inhibitor respectively.

[0011] Furthermore, preferably, the reducing agent is one or both of calcium and magnesium.

[0012] Thermal reduction methods for preparing metallic cesium (Cs) typically use oxide reduction or chloride reduction methods. The core principle is to use highly active reducing agents (such as calcium, magnesium, or carbon) to reduce rubidium compounds at high temperatures to obtain metallic cesium. The following are the principles of the main methods: Furthermore, preferably, the inhibitor is phosphite.

[0013] During the thermal reduction reaction, the phosphite evaporates into a gaseous phase. The phosphite gas thoroughly mixes with the gaseous rubidium and cesium metals before condensing to form a uniformly mixed condensate. During this process, because the phosphite molecule contains a phosphorus-oxygen double bond (P=O) and a phosphorus-oxygen single bond (P-O), the oxygen atom has a strong electronegativity and can form chemical bonds, such as coordination bonds, with atoms on the metal surface. Metal atoms have empty orbitals, and the oxygen atoms in the phosphite molecule can donate lone pairs of electrons to enter the empty orbitals of the metal atoms, forming coordination bonds and allowing the phosphite to adsorb on the metal surface. At the same time, due to the large molecular volume of the phosphite and the large steric hindrance, the rubidium and cesium metals are difficult to approach, preventing the alloying process between the rubidium and cesium.

[0014] Furthermore, preferably, the inhibitor is a mixture of different types of phosphites.

[0015] Different types of phosphites have different molecular sizes. Using phosphites of different sizes to adsorb metals is more conducive to reducing the exposed surface area of the metal than using a single type of phosphite, and is more effective than using only one type of phosphite.

[0016] Furthermore, preferably, the phosphite is trimethyl phosphite and tricresyl phosphite, and the ratio of the two is 4:6 to 6:4; or the phosphite is triethyl phosphite and tricresyl phosphite, and the ratio of the two is 4:6 to 6:4; Furthermore, preferably, the cesium compound is one or more of cesium chloride, cesium carbonate, cesium acetate, and cesium sulfate compounds extracted from lepidolite, and the compound contains both cesium and rubidium.

[0017] Furthermore, preferably, the content of cesium in the rubidium compound is higher than that of rubidium.

[0018] During the thermal reduction reaction, the phosphite evaporates into a gaseous phase. The phosphite gas thoroughly mixes with the gaseous rubidium and cesium metals before condensing to form a uniformly mixed condensate. During this process, because the phosphite molecule contains a phosphorus-oxygen double bond (P=O) and a phosphorus-oxygen single bond (P-O), the oxygen atom has a strong electronegativity and can form chemical bonds, such as coordination bonds, with atoms on the metal surface. Metal atoms have empty orbitals, and the oxygen atoms in the phosphite molecule can donate lone pairs of electrons to enter the empty orbitals of the metal atoms, forming coordination bonds and allowing the phosphite to adsorb on the metal surface. At the same time, due to the large molecular volume of the phosphite and the large steric hindrance, the rubidium and cesium metals are difficult to approach, preventing the alloying process between the rubidium and cesium.

[0019] Beneficial effects The present invention adds a specific type of inhibitor during the calcium thermal reduction process to prepare cesium metal, forming a barrier layer on the metal surface to prevent the rubidium and cesium generated during the reduction reaction from reacting and alloying. In the subsequent separation process, existing fractionation equipment can be used to separate the rubidium metal, cesium metal, and inhibitor, without increasing the equipment cost of existing processes. In particular, the use of different phosphites in combination with the metal and the different sized molecules can better cover the metal surface and prevent the rubidium and cesium from alloying. DETAILED DESCRIPTION

[0020] The present invention will be further explained below with reference to specific embodiments.

[0021] Example 1 The present invention provides a method for preparing high-purity metallic cesium, comprising the following steps: (1) Select high-purity cesium chloride powder, calcium, and trimethyl phosphite and prepare them in a mass ratio of 1:1:1.

[0022] (2) Control the vacuum degree in the vertical vacuum furnace below 0.01 Pa, fill it with inert gas to normal pressure, then evacuate the furnace, and then fill it with inert gas. Repeat this process for more than 3 times to replace the oxygen in the vertical vacuum furnace.

[0023] (3) Place the evenly mixed cesium chloride powder, metallic calcium particles and trimethyl phosphite into a treated vertical vacuum furnace, heat to 900°C under an inert atmosphere and normal pressure, and keep warm for 30 minutes.

[0024] (4) Collecting products: After the pressure gauge in the vertical vacuum furnace shows an increase, the vacuum pump is turned on, and the steam mixture is guided to the collecting device through a heated pipe connected to the inner chamber of the vertical vacuum furnace for condensation treatment to obtain a liquid mixture, wherein the liquid mixture is liquid metallic cesium, liquid metallic cesium and organic phosphate.

[0025] (5) The liquid mixture is distilled in sections to obtain high-purity metallic cesium, high-purity metallic cesium, and trimethyl phosphite, respectively. The purity of cesium is 99.999%.

[0026] Example 2 The present invention provides a method for preparing high-purity metallic cesium, comprising the following steps: (1) Select high-purity cesium chloride powder, calcium, and tritolyl phosphite and prepare them in a mass ratio of 1:1:1.

[0027] (2) Control the vacuum degree in the vertical vacuum furnace below 0.01 Pa, fill it with inert gas to normal pressure, then evacuate the furnace, and then fill it with inert gas. Repeat this process for more than 3 times to replace the oxygen in the vertical vacuum furnace.

[0028] (3) Place the evenly mixed cesium chloride powder, metallic calcium particles and tritolyl phosphite into a treated vertical vacuum furnace, heat to 900°C under an inert atmosphere and normal pressure, and keep warm for 30 minutes.

[0029] (4) Collecting products: After the pressure gauge in the vertical vacuum furnace shows an increase, the vacuum pump is turned on, and the steam mixture is guided to the collecting device through a heated pipe connected to the inner chamber of the vertical vacuum furnace for condensation treatment to obtain a liquid mixture, wherein the liquid mixture is liquid metallic cesium, liquid metallic cesium and organic phosphate.

[0030] (5) The liquid mixture is distilled in sections to obtain high-purity metallic cesium, high-purity metallic cesium, and tritolyl phosphite, respectively. The purity of cesium is 99.9991%.

[0031] Example 3 The present invention provides a method for preparing high-purity metallic cesium, comprising the following steps: (1) Select high-purity cesium chloride powder, calcium, trimethyl phosphite and tritolyl phosphite and prepare them in a mass ratio of 1:1:0.1:0.9.

[0032] (2) Control the vacuum degree in the vertical vacuum furnace below 0.01 Pa, fill it with inert gas to normal pressure, then evacuate the furnace, and then fill it with inert gas. Repeat this process for more than 3 times to replace the oxygen in the vertical vacuum furnace.

[0033] (3) Place the evenly mixed cesium chloride powder, metallic calcium particles, trimethyl phosphite and tritolyl phosphite into a treated vertical vacuum furnace, heat to 900°C under an inert atmosphere and normal pressure, and keep warm for 30 minutes.

[0034] (4) Collecting products: After the pressure gauge in the vertical vacuum furnace shows an increase, the vacuum pump is turned on, and the steam mixture is guided to the collecting device through a heated pipe connected to the inner chamber of the vertical vacuum furnace for condensation treatment to obtain a liquid mixture, wherein the liquid mixture is liquid metal cesium, liquid metal cesium and phosphite.

[0035] (5) The liquid mixture is distilled in sections to obtain high-purity metallic cesium, high-purity metallic cesium, and phosphite, respectively. The purity of cesium is 99.9992%.

[0036] Example 4 The present invention provides a method for preparing high-purity metallic cesium, comprising the following steps: (1) Select high-purity cesium chloride powder, calcium, trimethyl phosphite and tritolyl phosphite and prepare them in a mass ratio of 1:1:0.4:0.6.

[0037] (2) Control the vacuum degree in the vertical vacuum furnace below 0.01 Pa, fill it with inert gas to normal pressure, then evacuate the furnace, and then fill it with inert gas. Repeat this process for more than 3 times to replace the oxygen in the vertical vacuum furnace.

[0038] (3) Place the evenly mixed cesium chloride powder, metallic calcium particles, trimethyl phosphite and tritolyl phosphite into a treated vertical vacuum furnace, heat to 900°C under an inert atmosphere and normal pressure, and keep warm for 30 minutes.

[0039] (4) Collecting products: After the pressure gauge in the vertical vacuum furnace shows an increase, the vacuum pump is turned on, and the steam mixture is guided to the collecting device through a heated pipe connected to the inner chamber of the vertical vacuum furnace for condensation treatment to obtain a liquid mixture, wherein the liquid mixture is liquid metal cesium, liquid metal cesium and phosphite.

[0040] (5) The liquid mixture is distilled in sections to obtain high-purity metallic cesium, high-purity metallic cesium, and phosphite, respectively. The purity of cesium is 99.9998%.

[0041] Example 5 The present invention provides a method for preparing high-purity metallic cesium, comprising the following steps: (1) Select high-purity cesium chloride powder, calcium, trimethyl phosphite and tritolyl phosphite and prepare them in a mass ratio of 1:1:0.6:0.4.

[0042] (2) Control the vacuum degree in the vertical vacuum furnace below 0.01 Pa, fill it with inert gas to normal pressure, then evacuate the furnace, and then fill it with inert gas. Repeat this process for more than 3 times to replace the oxygen in the vertical vacuum furnace.

[0043] (3) Place the evenly mixed cesium chloride powder, metallic calcium particles, trimethyl phosphite and tritolyl phosphite into a treated vertical vacuum furnace, heat to 900°C under an inert atmosphere and normal pressure, and keep warm for 30 minutes.

[0044] (4) Collecting products: After the pressure gauge in the vertical vacuum furnace shows an increase, the vacuum pump is turned on, and the steam mixture is guided to the collecting device through a heated pipe connected to the inner chamber of the vertical vacuum furnace for condensation treatment to obtain a liquid mixture, wherein the liquid mixture is liquid metal cesium, liquid metal cesium and phosphite.

[0045] (5) The liquid mixture is distilled in sections to obtain high-purity metallic cesium, high-purity metallic cesium, and phosphite, respectively. The purity of cesium is 99.9998%.

[0046] Example 6 The present invention provides a method for preparing high-purity metallic cesium, comprising the following steps: (1) Select high-purity cesium chloride powder, calcium, trimethyl phosphite and tritolyl phosphite and prepare them in a mass ratio of 1:1:0.9:0.1.

[0047] (2) Control the vacuum degree in the vertical vacuum furnace below 0.01 Pa, fill it with inert gas to normal pressure, then evacuate the furnace, and then fill it with inert gas. Repeat this process for more than 3 times to replace the oxygen in the vertical vacuum furnace.

[0048] (3) Place the evenly mixed cesium chloride powder, metallic calcium particles, trimethyl phosphite and tritolyl phosphite into a treated vertical vacuum furnace, heat to 900°C under an inert atmosphere and normal pressure, and keep warm for 30 minutes.

[0049] (4) Collecting products: After the pressure gauge in the vertical vacuum furnace shows an increase, the vacuum pump is turned on, and the steam mixture is guided to the collecting device through a heated pipe connected to the inner chamber of the vertical vacuum furnace for condensation treatment to obtain a liquid mixture, wherein the liquid mixture is liquid metal cesium, liquid metal cesium and phosphite.

[0050] (5) The liquid mixture is distilled in sections to obtain high-purity metallic cesium, high-purity metallic cesium, and phosphite, respectively. The purity of cesium is 99.9992%.

[0051] Comparative Example: (1) Select high-purity cesium chloride powder and calcium and prepare them in a mass ratio of 1:1.

[0052] (2) Control the vacuum degree in the vertical vacuum furnace below 0.01 Pa, fill it with inert gas to normal pressure, then evacuate the furnace, and then fill it with inert gas. Repeat this process for more than 3 times to replace the oxygen in the vertical vacuum furnace.

[0053] (3) Place the evenly mixed cesium chloride powder and metallic calcium particles into a treated vertical vacuum furnace, heat to 900°C under an inert atmosphere and normal pressure, and keep warm for 30 minutes.

[0054] (4) Collecting products: After the pressure gauge in the vertical vacuum furnace shows an increase, the vacuum pump is turned on, and the steam mixture is guided to the collecting device through a heated pipe connected to the inner chamber of the vertical vacuum furnace for condensation treatment to obtain a liquid mixture, wherein the liquid mixture is liquid metallic cesium and liquid metallic cesium.

[0055] (5) The liquid mixture is distilled in sections to obtain high-purity metallic cesium and high-purity metallic cesium, respectively. The purity of cesium is 99.991%.

[0056] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing high-purity metallic cesium, characterized in that: The following steps are involved: (1) Prepare raw materials: Select high-purity cesium compound powder, reducing agent, and inhibitor in a mass ratio of 2:(1-4):(1-2); (2) Replace oxygen: Control the vacuum degree in the vertical vacuum furnace at 0.1 Pa, fill it with inert gas to normal pressure, then evacuate the furnace, and then fill it with inert gas. Repeat this process for more than 3 times to replace the oxygen in the vertical vacuum furnace. (3) Mixing and heating: Place the evenly mixed cesium compound powder and metallic calcium particles into a treated vertical vacuum furnace, heat to 550-1000°C under an inert atmosphere and normal pressure, and keep warm for 30-90 minutes; (4) Collecting products: After the pressure gauge in the vertical vacuum furnace shows an increase, the vacuum pump is turned on, and the metallic cesium vapor is guided to the condensation part through the heated pipe connected to the inner chamber of the vertical vacuum furnace. After condensing into droplets, the droplets flow into the collector to obtain a liquid mixture, wherein the liquid mixture is liquid metallic rubidium, liquid metallic cesium and organic phosphate; (5) The liquid mixture is vacuum distilled to obtain high-purity metallic rubidium, high-purity metallic cesium and inhibitor respectively.

2. The method for preparing high-purity metallic cesium according to claim 1, wherein The reducing agent is one or both of calcium and magnesium.

3. The method for preparing high-purity metallic cesium according to claim 1, wherein: The inhibitor is phosphite.

4. The method for preparing high-purity metallic cesium according to claim 1, wherein: The phosphite is one or more of trimethyl phosphite, triethyl phosphite and tricresyl phosphite.

5. The method for preparing high-purity metallic cesium according to claim 1, wherein: The phosphite is trimethyl phosphite and tricresyl phosphite, and the ratio of the two is 4:6 to 6:

4.

6. The method for preparing high-purity metallic cesium according to claim 1, characterized in that: The phosphite is triethyl phosphite and tricresyl phosphite, and the ratio of the two is 4:6 to 6:

4.

7. The method for preparing high-purity metallic cesium according to any one of claims 1 to 6, characterized in that: The cesium compound is one or more of cesium chloride, cesium carbonate, cesium carbonate, cesium acetate, and cesium sulfate compounds extracted from lepidolite ore, and the cesium compound also contains a rubidium compound.

8. The method for preparing high-purity metallic cesium according to claim 7, characterized in that: The content of cesium in the cesium compound is higher than that of rubidium.

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