Method for preparing indium trifluoride through continuous gas phase

Abstract

The invention provides a method for preparing indium trifluoride in a continuous gas phase, which comprises the following steps of: performing atomization, sublimation or fluidization pretreatment on an indium source in an inert carrier gas atmosphere to form a gaseous or superfine particle indium source material flow; continuously introducing the indium source material flow and fluorine-containing gas into a continuous reactor with a function of mechanically updating a reaction interface, and carrying out gas-phase fluorination reaction at the reaction temperature of 500-900 DEG C to generate a gas-solid mixture containing indium trifluoride solid and tail gas; wherein the feeding molar ratio of an indium element in the indium source to a fluorine element in the fluorine-containing gas is 1: (3.0-6.5); and performing continuous gas-solid separation on the gas-solid mixture obtained in the step S2. Through specific reactor selection and process parameter coupling, the preparation difficulties that the efficiency is low, the energy consumption is high, the product consistency is poor and the metal indium is easy to sinter and coat when the indium trifluoride is prepared by an existing intermittent method are overcome, the safe and continuous production of the indium trifluoride is realized, and the product purity reaches the electronic grade standard.

Description

Technical Field

[0001] This invention relates to the field of inorganic fluoride preparation technology, specifically to a continuous gas-phase preparation method for indium trifluoride. Background Technology

[0002] Indium trifluoride (InF3) is a key precursor material in fields such as optical coating, specialty glasses, organic synthesis catalysis, and semiconductor thin film deposition. Currently, its preparation methods mainly suffer from the following drawbacks: (1) Direct fluorination method: using fluorine gas (F2) or anhydrous hydrogen fluoride (HF), the raw materials are dangerous and highly corrosive, usually carried out in a batch high pressure vessel, the reaction cycle is long (>24 hours), the equipment wear is serious, and the tail gas treatment is complicated.

[0003] (2) Oxide fluorination method: Solid fluorinating agent (such as ammonium bifluoride) is used to react with indium oxide in a solid phase. The mass transfer efficiency is low, the reaction is incomplete, repeated calcination is required, energy consumption is high, and a large amount of ammonium fluoride salts are produced as by-products, which puts great pressure on the environment.

[0004] (3) Dehydration of hydrated salts: Hydrated metal fluorides are precipitated by reacting metal salts with hydrofluoric acid in an aqueous solution. The final dehydration step is prone to hydrolysis, sintering or introduction of impurities into the product, and the purity of the product is difficult to meet the requirements of electronic applications.

[0005] Furthermore, all of the above methods are intermittent operations, resulting in low production efficiency, poor batch-to-batch product consistency, high energy consumption, and low automation. In particular, when using metallic indium as a raw material, liquid indium is prone to agglomeration at high temperatures, and the resulting dense InF3 product layer encapsulates unreacted indium nuclei, severely hindering the reaction and leading to low conversion rates and the inability to operate continuously. Currently, China lacks technology for the large-scale, high-purity preparation of indium trifluoride. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a continuous gas-phase method for preparing indium trifluoride that enables continuous production of indium trifluoride, features a closed reaction process, is environmentally friendly, safe and efficient, and is suitable for electronic-grade purity requirements.

[0007] The technical solution of the present invention is as follows: 1. A method for the continuous gas-phase preparation of indium trifluoride, comprising the following steps: S1. Under an inert carrier gas atmosphere, the indium source is atomized, sublimated or fluidized to form a gaseous or ultrafine particulate indium source material flow; S2. The indium source material stream and fluorine-containing gas are continuously fed into a continuous reactor with a mechanically renewed reaction interface function, and a gas-phase fluorination reaction is carried out at a reaction temperature of 500~900℃ to generate a gas-solid mixture containing indium trifluoride solid and tail gas; wherein, the feed molar ratio of indium element in the indium source to fluorine element in the fluorine-containing gas is 1:3.0~6.5; the gas-phase fluorination reaction is carried out in a rotary drum reactor or a screw propulsion reactor, which can continuously and forcibly renew the surface of the reactants through mechanical rotation (rotary drum tumbling or screw propulsion shearing), effectively break up any product coating layers that may be formed, prevent material adhesion and sintering, and ensure that the reaction is continuous and complete.

[0008] S3. The gas-solid mixture obtained in step S2 is subjected to continuous gas-solid separation to collect the solid indium trifluoride product and the tail gas separately. The gas-solid mixture generated by the reaction is continuously separated by a high-temperature gas-solid separator (such as a cyclone separator) to obtain a high-purity solid InF3 product.

[0009] Furthermore, the indium source of the present invention is one of metallic indium, indium trichloride, indium trioxide, or indium trinitrate; the fluorine-containing gas is one of nitrogen trifluoride, sulfur hexafluoride, tetrafluoromethane, or trifluoromethane; and the inert carrier gas is nitrogen or argon.

[0010] Furthermore, the continuous reactor described in this invention is a rotary drum reactor or a helical propulsion reactor.

[0011] Furthermore, when the continuous reactor is a rotary drum reactor, the rotation speed of the rotary drum reactor is controlled at 1~10 rpm, the feed flow rate of the fluorine-containing gas is 1.0~4.0 L / min (at 273.15 K and 101.325 kPa), and the average residence time of the material is 20~80 minutes.

[0012] Furthermore, when the continuous reactor is a screw propulsion reactor, the screw shaft speed of the screw propulsion reactor is controlled at 0.5~5 rpm, the feed flow rate of the fluorine-containing gas is 0.5~2.5 L / min (at 273.15 K and 101.325 kPa), and the average residence time of the material is 40~100 minutes.

[0013] Furthermore, the present invention further includes the following after step S3: Furthermore, the present invention purifies the separated exhaust gas, the purification process including alkaline washing and / or treatment targeting chlorine- or fluorocarbon compounds.

[0014] Compared with the prior art, the present invention has the following advantages: 1. This invention enables continuous production from raw material input to product collection, improving production efficiency and equipment utilization, and ensuring excellent batch consistency of products.

[0015] 2. The rotary drum reactor or helical propulsion reactor used in this invention actively and forcibly renews the reaction surface through mechanical tumbling or shearing action, solving the problems of reaction termination caused by the coalescence and sintering of indium droplets and the coating of solid products, thereby realizing a continuous and stable reaction process.

[0016] 3. The gas-phase reaction process of this invention is pure, avoiding impurities introduced by solvents and wet processes. The product purity is stable at over 99%, and can reach up to 99.98%, meeting the requirements of electronic-grade applications.

[0017] 4. This invention uses safe fluorine-containing gases (such as NF3 and SF6) to replace highly toxic F2. The reaction process is closed, the reaction time is significantly shortened, and the exhaust gas is centrally treated, making it environmentally friendly. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the process flow of the present invention. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the embodiments.

[0020] Example 1: Using indium metal and NF3 as raw materials, a rotary drum reactor was used.

[0021] A continuous gas-phase preparation method for indium trifluoride includes the following steps: S1. 500g of high-purity metallic indium (purity 99.99%) is heated to 300℃ in an argon-protected melting furnace to melt it. The molten indium is atomized by an ultrasonic atomizer under 0.3 MPa argon gas to produce droplets with a particle size D50≈50 µm, which are transported by argon gas carrier (flow rate 1.5 L / min). S2. High-purity NF3 (99.995%) is preheated to 500℃ and then introduced at a flow rate of 1.2 L / min into a rotary reactor made of Inconel alloy (cylinder diameter 20 cm, effective length 1.5 m, reactor inclination angle set to 2). The reaction temperature is controlled at 800℃ and the rotary drum speed is 5 rpm. In the feed, the molar ratio of indium to NF3 is 1:3.02 according to F. S3. The gas-solid mixture obtained after the reaction in step S2 is fed into a cyclone separator operating at 600 °C. The solid indium trifluoride product falls into a sealed tank filled with high-purity argon gas, and the tail gas is discharged after being washed with 5% NaOH solution.

[0022] Results: The separated solid indium trifluoride product was a white, free-flowing powder with a purity of 99.98% and an indium conversion rate of 99.8%.

[0023] Example 2: Using indium metal and SF6 as raw materials, a helical propulsion reactor was employed. A continuous gas-phase preparation method for indium trifluoride includes the following steps: S1. Same as Example 1; S2. High-purity SF6 (99.9%) is preheated to 600℃ and then introduced at a flow rate of 2.0 L / min into a closed spiral propulsion reactor made of high-temperature alloy (reaction tube diameter 10 cm, effective length 2 m, gap between spiral blades and tube wall < 1 mm). The reaction temperature is controlled at 850℃ to promote SF6 cracking, and the spiral shaft speed is 1.5 rpm. In the feed, the molar ratio of indium to SF6 is 1:3.05 (calculated as F). S3. Same as Example 1; Results: The obtained solid indium trifluoride product had a purity of 99.3% and an indium conversion rate of 99.5%.

[0024] Example 3: Using In2O3 and NF3 as raw materials, a rotary drum reactor was used. A continuous gas-phase preparation method for indium trifluoride includes the following steps: S1. Place high-purity In2O3 powder (99.9%, D50≈5 µm) in the silo, and use nitrogen as the carrier gas to uniformly blow the In2O3 powder into the rotary reactor made of Inconel alloy through a precision screw feeder. S2. High-purity NF3 (99.995%) is preheated to 500℃ and then introduced at a flow rate of 1.2 L / min into a rotary reactor made of Inconel alloy (cylinder diameter 20 cm, effective length 1.5 m, reactor inclination angle set to 2). The reaction temperature is controlled at 750℃ and the rotary drum speed is 8 rpm. In the feed, the feed molar ratio of In2O3 to NF3 is 1:6.1 according to F. S3. Same as Example 1; Results: The purity of the separated solid indium trifluoride product was 99.5%, and the indium conversion rate was 99% (based on the In2O3 content in the residue after reaction).

[0025] Example 4: Using InCl3 and NF3 as raw materials, a screw-propelled reactor was employed. A continuous gas-phase preparation method for indium trifluoride includes the following steps: S1. Place solid InCl3 in a sublimation apparatus, heat it to 350 °C to sublimate it, and use argon gas to carry the InCl3 vapor (approximately 0.5 L / min carrier gas flow rate) to the screw propulsion reactor; S2. NF3 feed is the same as in Example 1; the material reacts in a screw propulsion reactor, the temperature is set at 500 ℃, the screw speed is 2 rpm, wherein, in the feed, the feed molar ratio of InCl3 to NF3 is 1:3.1 according to F; S3. Same as Example 1, but with the addition of existing dechlorination treatment for the exhaust gas.

[0026] Results: The purity of the separated indium trifluoride product was 99.9%, and the indium conversion rate was 99.5%.

[0027] Example 5: Using indium metal and CF4 as raw materials, a rotary drum reactor was used. A continuous gas-phase preparation method for indium trifluoride includes the following steps: S1. The indium metal treatment and feeding are the same as in Example 1; S2. CF4 (99.9%) is used as the fluorine source, preheated to 700℃, and then fed into a rotary reactor at a flow rate of 3.5 L / min. The reaction temperature is 900℃ and the rotary drum speed is 4 rpm. In the feed, the molar ratio of indium to CF4 is 1:3.2 (calculated as F).

[0028] S3. Same as in Example 1, the exhaust gas is introduced into a high-temperature incinerator (1100℃ ~1300℃), oxygen is added as a combustion aid, and the deeply oxidized gas enters a quench tower, is washed with 5% NaOH solution and then discharged.

[0029] Results: The separated indium trifluoride product was grayish in color, with a purity of 98.8% and an indium conversion rate of 95%.

[0030] Example 6: Using In2O3 and SF6 as raw materials, a screw-propelled reactor was employed. A continuous gas-phase preparation method for indium trifluoride includes the following steps: S1. In2O3 powder and feed are the same as in Example 3; S2. SF6 and feed are the same as in Example 2 (preheated to 600°C, flow rate 2.2 L / min). The material is reacted in a screw-driven reactor at a temperature of 880°C and a screw speed of 1 rpm. In the feed, the molar ratio of In2O3 to SF6 is 1:6.5 (calculated as F).

[0031] S3. Same as Example 1.

[0032] Results: The obtained indium trifluoride product was 98.5%, and the indium conversion rate was 97%.

[0033] Comparative Example

[0034] A fluidized bed reactor was used, with the same raw materials and temperature as in Example 1. The specific process is as follows: The raw materials and feed were the same as in Example 1. A fluidized bed reactor was used, and the temperature of the fluidized bed reaction zone was set to 800°C (the same temperature as in Example 1). By adjusting the flow rate of NF3, the indium droplets in the reactor were brought into a normal fluidized state (the initial apparent gas velocity was controlled at about 0.4 m / s). The plan was to discharge the gas-solid mixture after the reaction from the top of the reactor and enter the same high-temperature cyclone separator as in Example 1 for product collection.

[0035] In the initial stage of the reaction (about the first 5 minutes), the system pressure drop fluctuated violently, then rose rapidly with periodic pulsations, showing typical throttling and channeling phenomena, indicating that the fluidization state was extremely unstable. Fifteen minutes later, an abnormal hot spot appeared in the reactor bed temperature, followed by a continuous abnormal increase in system pressure, which eventually led to blockage of the feed pipeline and forced the experiment to be stopped.

[0036] After the reactor cooled and was disassembled for inspection, it was found that a large, hard mixture of metallic indium and the reaction product InF3 had formed in the area above the gas distribution plate at the bottom of the reactor. This mixture was the direct cause of the pressure increase. Due to the high surface tension of metallic indium at high temperatures, the indium droplets generated by atomization easily coalesced after collisions during fluidization, forming larger droplets. These large droplets could not be fluidized normally by the gas flow and instead sank and adhered to the distribution plate or the reactor wall. Even if InF3 was generated on the surface of the indium droplets that were not completely adhered, in the absence of mechanical shear force in the fluidized bed, this solid product layer could not be effectively peeled off. It quickly enveloped the internal indium, preventing the reaction from proceeding further and causing the reaction to actually terminate.

[0037] Comparative examples demonstrate that fluidized bed reactors are unsuitable for the gas-phase fluorination reaction using metallic indium as a raw material in this invention. The reasons are: ① The tendency of metallic indium droplets to adhere and coalesce at high temperatures contradicts the conditions required to maintain a stable fluidized state. ② The fluid shear force in the fluidized state is insufficient to effectively break down and remove the dense InF3 product layer coating the indium surface. ③ A stable fluidized state cannot be established and maintained, making continuous process impossible.

[0038] The present application has been described above with reference to embodiments and comparative examples. However, these embodiments are merely exemplary and serve only as illustrations. Various substitutions and modifications can be made to the present application based on these embodiments, all of which fall within the protection scope of the present application.

Claims

1. A method for continuous gas-phase preparation of indium trifluoride, characterized in that, Includes the following steps: S1. Under an inert carrier gas atmosphere, the indium source is atomized, sublimated or fluidized to form a gaseous or ultrafine particulate indium source material flow; S2. The indium source material stream and fluorine-containing gas are continuously fed into a continuous reactor with a mechanically renewed reaction interface function, and a gas-phase fluorination reaction is carried out at a reaction temperature of 500~900℃ to generate a gas-solid mixture containing indium trifluoride solid and tail gas; wherein, the feed molar ratio of indium element in the indium source to fluorine element in the fluorine-containing gas is 1:3.0~6.5; S3. Perform continuous gas-solid separation on the gas-solid mixture obtained in step S2, and collect the solid indium trifluoride product and the tail gas respectively.

2. The method according to claim 1, characterized in that, In step S1, the indium source is one of metallic indium, indium trichloride, indium trioxide, or indium trinitrate; the fluorine-containing gas is one of nitrogen trifluoride, sulfur hexafluoride, tetrafluoromethane, or trifluoromethane; and the inert carrier gas is nitrogen or argon.

3. The method according to claim 1, characterized in that, In step S2, the continuous reactor is a rotary drum reactor or a helical propulsion reactor.

4. The method according to claim 3, characterized in that, When the continuous reactor is a rotary reactor, the rotation speed of the rotary reactor is controlled at 1~10 rpm, the feed flow rate of the fluorine-containing gas is 1.0~4.0 L / min, and the average residence time of the material is 20~80 minutes.

5. The method according to claim 3, characterized in that, When the continuous reactor is a screw propulsion reactor, the screw shaft speed of the screw propulsion reactor is controlled at 0.5~5 rpm, the feed flow rate of the fluorine-containing gas is 0.5~2.5 L / min (standard state), and the average residence time of the material is 40~100 minutes.

6. The method according to claim 1, characterized in that, Step S3 is followed by: S4. The separated exhaust gas is purified, the purification process including alkaline washing and / or treatment of chlorine- or fluorocarbon-containing compounds.

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