Method and system for purifying thionyl fluoride by multi-stage rectification and adsorption combination

Abstract

The present application relates to fluorinated fine separation technical field, specifically to a kind of multistage rectification and adsorption combined purification of thionyl fluoride method and system.The method includes: by raw gas heat exchange into first rectification column and is preliminarily separated, after eliminating low-boiling impurities, it is sent into second rectification column and is further purified, after rectification, high-purity gas is converted into liquid crude product by condensation, then it is carried out by mixed adsorbent fixed bed and is deeply removed impurity, and finally the purity of thionyl fluoride product is higher than 99.999%.The system includes raw gas feeding unit, two-stage rectification column, condenser, adsorption device and product tank, module is sequentially connected and has temperature and pressure control and anticorrosion structure, suitable for continuous high-purity thionyl fluoride industrialized purification production.

Description

Technical Field

[0001] This invention relates to the field of fine separation technology in fluorochemicals, specifically to a method and system for purifying thionyl fluoride through a combination of multi-stage distillation and adsorption. Background Technology

[0002] With the continuous development of the semiconductor industry and breakthroughs in high-end chip technology, dry etching technology has been widely used. As a result, the key etching and cleaning electronic gases have also been put forward with higher requirements, and fluorine-based electronic gases have ushered in rapid development.

[0003] Fluorine-based electronic gases typically include sulfur hexafluoride (SF6), carbon tetrafluoride (CF4), and fluorocarbon gases (such as CH3F, CH2F2, CHF3, C2F6, C3F8, etc.), all of which have high GWP values ​​and pose significant potential environmental impacts. Developing etching and cleaning gases with low GWP values ​​has become crucial for the semiconductor industry. Thionyl fluoride (SOF2) ensures effective etching and cleaning while being easier to handle and more environmentally friendly.

[0004] In actual industrial production, due to incomplete reaction of raw materials, impurities in by-products, backmixing of tail gas, and limitations in the separation efficiency of towers, the synthesized thionyl fluoride often contains impurities such as hydrogen chloride, moisture, unreacted raw materials, or low-boiling by-products, which cannot directly meet the requirements for high-purity use. Especially in the field of electronic grade where the purity requirements are extremely high, high-quality separation must be achieved through further purification methods.

[0005] In existing technologies, the main methods for purifying thionyl fluoride include single distillation or adsorption. Single distillation separates impurities with different boiling points through multiple distillations. Although it can remove some volatile impurities, it is not effective for removing highly polar impurities, impurities with similar boiling points, or non-volatile impurities, and it is particularly difficult to completely remove moisture and hydrogen chloride simultaneously. Adsorption relies on the selective adsorption of impurities by solid adsorbents and is suitable for removing trace amounts of moisture or acidic gases. However, when used alone, its processing capacity is limited, its adsorption efficiency decreases with operating time, and its regeneration process is complex, making it unsuitable for long-term continuous operation.

[0006] To achieve efficient purification of thionyl fluoride, some studies have attempted to employ multi-effect distillation or membrane separation, but these methods involve large equipment investments and complex operations, and a mature, widely applicable industrial solution has yet to be developed. Therefore, how to combine the high-efficiency separation capabilities of multi-stage distillation with the selective removal advantages of adsorption technology for specific impurities to construct a deep purification method and system for thionyl fluoride that balances purification efficiency, operational stability, and industrial feasibility is a pressing issue in the current technological field. Summary of the Invention

[0007] To address the above problems, the present invention aims to provide a method for purifying thionyl fluoride through a combination of multi-stage distillation and adsorption, comprising the following steps: S1. Feed gas: A mixed gas containing thionyl fluoride, hydrogen chloride, water vapor, unreacted raw materials and by-products is introduced into the bottom of the first-stage distillation column as feed after heat exchange. S2, First-stage distillation: In the first-stage distillation column, by setting the bottom temperature to 80-120℃ and the top temperature to 30-60℃, multi-stage thermal separation is carried out in the column, so that low-boiling impurity components escape with the top gas and the bottom is enriched with thionyl fluoride and high-boiling impurities. S3. Extraction and separation: Extract the distillation intermediate at the outlet of the first-stage distillation column, controlling the extraction temperature range to be 40-70℃, in which the concentration of thionyl fluoride accounts for more than 80% of the total gas. S4. Second-stage distillation: The intermediate product is introduced into the second-stage distillation column, and the top temperature of the column is adjusted to 20-40°C and the bottom temperature is adjusted to 70-100°C. The mass transfer efficiency is enhanced by the precision packing in the column, and impurities with close boiling points are further removed to obtain thionyl fluoride top gas with a purity of not less than 99.95%. S5. Gas condensation: The gas from the top of the second-stage distillation column is introduced into a shell-and-tube condenser and subjected to phase change condensation at -5℃ to +5℃ to obtain crude liquid thionyl fluoride. S6. Adsorption and purification: The condensed crude thionyl fluoride is sent to an adsorption device equipped with a fixed bed adsorption material via a metering pump. The adsorption device is filled with a 1:1 mass ratio of molecular sieve and silica gel particles to remove residual hydrogen chloride and trace moisture. The operating temperature is controlled at 20-35℃ and the tower pressure is maintained at atmospheric pressure to 0.2 MPa. S7. Product Collection: The adsorption-treated thionyl fluoride is introduced into a nitrogen-sealed stainless steel storage tank. The storage tank is equipped with high and low liquid level alarms and an exhaust circuit. The purity of the collected product is higher than 99.999%.

[0008] In a preferred embodiment, the first-stage distillation column packing is structured metal packing made of 304 or 316L stainless steel. The packing unit structure is a corrugated perforated plate shape with a specific surface area of ​​200–350 m² / m³, a bulk density of 150–300 kg / m³, a column packing section height of 4–6 meters, and is equipped with a liquid distributor, a redistributor, and a support device. The theoretical number of trays is not less than 90, and the column is equipped with a temperature detection point and a top reflux ratio adjustment mechanism.

[0009] In a preferred embodiment, the second-stage distillation column is internally configured with a bulk packing structure. The packing material is Pall rings or stepped rings made of polytetrafluoroethylene. The height of the packing section is 9 to 12 meters. An insulation layer and a temperature-controlled electric heating belt are installed on the outside of the column wall. A condensate reflux tank is installed at the top of the column, and the reflux ratio is controlled by an automatic regulating valve. A high-precision level gauge and a heating jacket are installed at the bottom of the column.

[0010] In a preferred embodiment, the shell-and-tube condenser adopts a multi-tube bundle design, the cooling medium is an ethanol-salt water mixture coolant at -5℃ to 5℃, the shell side is made of stainless steel, the fluid velocity inside the tubes is 0.5~1.5 m / s, and is equipped with an inlet and outlet temperature difference detection device and a condensation efficiency feedback device. A buffer collection tank and a liquid level sensor are installed at the condenser outlet to control the subsequent delivery rhythm.

[0011] In a preferred embodiment, the adsorption device includes two adsorption units arranged in parallel. Each adsorption unit includes three adsorption towers (T4, T5, and T6) arranged in series. The filling height of each adsorption tower is 1.0 to 1.5 meters. The internal packing material is modified molecular sieve and medium-pore spherical silica gel particles with a particle size range of 1.5 to 3.0 mm. Inlet and outlet temperature monitoring points and differential pressure monitoring devices are provided. The adsorption bed operation cycle is 100 to 200 hours. Switching is performed online via a three-way valve without interrupting the purification process.

[0012] The present invention also provides a system for the multi-stage distillation and adsorption combined purification of thionyl fluoride for implementing the method, comprising a raw material gas feeding unit, a first distillation column unit, a second distillation column unit, a condensation unit, an adsorption unit, and a product storage tank unit, which are connected in sequence to form the main process of thionyl fluoride purification. Each unit is equipped with pressure monitoring, temperature regulation, and anti-corrosion lining material. The connecting pipelines are connected by stainless steel welding and are equipped with online sampling ports and detection interfaces.

[0013] In a preferred embodiment, the raw material feeding unit includes a vaporizer, a heat exchanger, a mass flow controller, a raw material buffer tank, and a pressure regulating valve. The vaporizer is equipped with a steam jacket, the heat exchanger is a high-efficiency plate heat exchanger, the temperature of the feed gas is controlled between 50 and 80°C, and the pressure is controlled between 0.1 and 0.3 MPa. The buffer tank is equipped with an anti-backflow check valve and a back pressure suppression device. After heat exchange, the feed gas enters the bottom of the first distillation column.

[0014] In a preferred embodiment, the first distillation column unit adopts a vertical column structure with a height of 8-12 m. The column body is made of 304 stainless steel and filled with stainless steel structured packing. It is equipped with a liquid redistribution plate and a spray reflux device. The bottom of the column is equipped with an electric heating tube bundle jacket, and the top of the column is equipped with a shell-side condenser and a reflux tank. It is also equipped with an automatic temperature control module for the top and bottom of the column and a reflux ratio adjustment actuator.

[0015] In a preferred embodiment, the second distillation column unit adopts a double-layer structure, with an inner layer of corrosion-resistant PTFE lining and an outer layer of 316 stainless steel. The column is equipped with a multi-segment temperature sensor array for multi-point temperature monitoring. The gas outlet at the top of the column is connected to the condenser. An automatic liquid level control buffer tank is installed after the condenser. The bottom of the column is equipped with a heat transfer oil jacket and a heat medium temperature control valve. Fine heating regulation can be achieved through PID control algorithm.

[0016] Beneficial effects This invention provides a method and system for the combined purification of thionyl fluoride through multi-stage distillation and adsorption, which effectively solves the problems of low separation efficiency, difficulty in completely removing impurities, and unstable product purity in existing purification processes. By combining two or more stages of distillation with adsorption, multi-stage distillation is used to perform gradient separation of components with different boiling points. Volatile impurities such as hydrogen chloride and low-boiling byproducts are first removed, and then organic impurities with similar boiling points are further stripped through a precision column section, thus achieving efficient preliminary purification of thionyl fluoride.

[0017] By introducing an adsorption unit and employing a composite adsorbent to synergistically adsorb moisture and polar impurities, the purity and stability of the final product are significantly improved. The system adopts a continuous process design, allowing for precise adjustment of parameters at each stage, making it suitable for different raw material ratios and production capacity requirements. The overall system has a compact structure, reasonable equipment configuration, and good industrial scalability. Through the aforementioned combined purification route, the purity of the obtained thionyl fluoride remains consistently above 99.999%, making it particularly suitable for the electronic chemicals field, which has extremely high requirements for gas purity. This significantly improves product added value and resource utilization efficiency, demonstrating high practical value and promising prospects for widespread application. Attached Figure Description

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

[0019] To enhance understanding of the present invention, the present invention will be further described in detail below with reference to embodiments. These embodiments are only used to explain the present invention and do not constitute a limitation on the scope of protection of the present invention.

[0020] Example 1 Please see Figure 1 As shown, this embodiment provides a method for purifying thionyl fluoride using a combination of multi-stage distillation and adsorption. This method is suitable for high-purity fine separation of raw material gases containing impurities of thionyl fluoride. The entire process is based on multi-stage distillation combined with adsorption purification, significantly improving product purity and separation efficiency. Specifically, it includes the following steps: S1, Raw material gas feed: Gas from the thionyl fluoride synthesis reaction is used as feedstock. This feedstock gas contains the main component, thionyl fluoride (SOF2), along with hydrogen chloride (HCl), water vapor, unreacted feedstock gases (such as SOCl2 and HF), and some by-products. The gas is first preheated using a heat exchanger, with the heat exchange medium temperature controlled between 60 and 80°C to reduce energy consumption in subsequent distillation columns. The preheated feedstock gas enters the bottom of the first-stage distillation column at a controlled mass flow rate, with the feed pressure stabilized between 0.15 and 0.25 MPa and the feed temperature maintained between 60 and 75°C to facilitate a reasonable vapor-liquid equilibrium within the column.

[0021] S2, First-stage distillation: The first-stage distillation column adopts a structured packed column structure with a column diameter of Φ250 mm and a height of 10 meters. It is filled with 304 stainless steel corrugated perforated sheet-like structured packing with a specific surface area of ​​[missing information]. The bulk density is approximately 220 kg / m³, and the total height of the packing section is 5 meters. The tower is equipped with a liquid distributor, redistribution plate, and stainless steel support plates. Multi-point thermocouple arrays are installed at both the top and bottom of the tower for real-time monitoring of the temperature gradient. The bottom heater is a tubular electric heater, with the temperature controlled between 80 and 120°C. The top temperature is maintained between 30 and 60°C. A suitable liquid concentration within the tower is maintained by adjusting the reflux ratio of the top condenser (typically set at 3:1).

[0022] In this distillation process, low-boiling-point components such as hydrogen chloride, water vapor, and some unreacted HF are carried out with the overhead gas, partially liquefied by the overhead condenser, and then discharged from the system; while high-boiling-point components and the main product thionyl fluoride are gradually concentrated downwards and enriched in the middle to lower part of the column.

[0023] S3, Extraction and Separation: The outlet, located in the middle of the first-stage distillation column, is used to capture thionyl fluoride-enriched gas as an intermediate product. This outlet is situated at approximately 55% of the column height, and the extraction temperature is maintained between 50 and 65°C to ensure that the thionyl fluoride content in the extracted component is greater than 80%. The extracted gas is then introduced into a buffer tank via a separate pipeline and directly into the second-stage distillation column, avoiding the introduction of contaminants such as moisture during intermediate storage and maintaining the continuity and airtightness of the entire process.

[0024] S4, Second-stage distillation: The second-stage distillation column is designed as a high-resolution separation column with a diameter of Φ200 mm and a height of 8 meters. It is filled with stepped ring packing made of polytetrafluoroethylene (PTFE), with a particle size of φ25–φ38 mm and a packing section height of 6.5 meters. This packing exhibits high corrosion resistance and surface wettability, which is beneficial for the separation of high-purity gases. A reflux condenser and reflux regulating valve are located at the top of the column, while a heat transfer oil heating jacket is installed at the bottom, with a temperature control range of 70–100℃. The top temperature is controlled at 20–40℃, and the overall reflux ratio is set at 5:1.

[0025] The secondary distillation process in this column effectively removes intermediate impurities with boiling points close to thionyl fluoride, such as sulfur trifluoride or residual SOCl2. The overhead gas output from this step has a purity of over 99.95%, making it a near-final product of high-purity thionyl fluoride with a solid foundation for industrial applications.

[0026] S5, Gas condensation: The high-purity thionyl fluoride gas exiting from the top of the second-stage distillation column is introduced into a shell-and-tube condenser for liquefaction and condensation. The condenser employs a multi-tube bundle design, with the shell side made of 316 stainless steel. The cooling medium is an ethanol-salt water mixture at -5℃ to +5℃, operating in a closed-loop refrigeration system. The gas velocity inside the tubes is 1.0 m / s to ensure sufficient heat exchange efficiency. Temperature difference detectors installed at the condenser inlet and outlet provide real-time feedback on the heat exchange effect and adjust the refrigerant flow rate to maintain condensation efficiency.

[0027] The condensate flows by gravity into a buffer collection tank equipped with a level sensor and nitrogen sealing protection to prevent outside air from entering the system and to prevent the introduction of water vapor and oxygen from causing the decomposition of thionyl fluoride or moisture absorption.

[0028] S6. Adsorption and purification: The liquefied crude thionyl fluoride is pumped into an adsorption unit for fine purification. The adsorption unit consists of three adsorption towers (T4, T5, and T6) arranged in series. Each tower is a stainless steel cylinder with an inner diameter of Φ200 mm and an adsorption bed height of 1.2 meters. The adsorbent is modified molecular sieve and spherical silica gel particles with a particle size range of 2.0–3.0 mm. The operating temperature of the adsorption bed is controlled between 20 and 30°C, and the pressure inside the tower is maintained between atmospheric pressure and 0.2 MPa. Specifically, the upper layer of each adsorption tower is filled with silica gel, the middle layer with a mixture of modified molecular sieve and silica gel, and the lower layer with modified molecular sieve. The modified molecular sieve is formed by passivating the surface of the molecular sieve at high temperature under an NF3 atmosphere to form silanol groups, thereby reducing irreversible adsorption loss of SOF2.

[0029] As a further improvement, the upper, middle, and lower layers are configured in a gradient-descending manner. The upper layer of silica gel primarily adsorbs large molecular impurities and some water vapor. Due to its large adsorption capacity, it can quickly remove most impurities from the raw gas, reducing the burden on subsequent adsorption layers. The middle layer mixture, a mixture of modified molecular sieve and silica gel, can simultaneously adsorb medium-molecular-weight impurities and some water vapor, acting as a transition adsorption layer to further purify the gas. The lower layer of modified molecular sieve focuses on adsorbing small molecular impurities, particularly optimizing the irreversible adsorption loss of thionyl fluoride (SOF2). Since the upper and middle layers have already removed most impurities, the lower layer can perform fine adsorption more efficiently. Specifically, in one embodiment, the upper, middle, and lower layers are configured in a weight ratio of 6:3:1.

[0030] As a further improvement, in one embodiment, the modified molecular sieve is obtained by the following method: Molecular sieves are heated to 270-330°C in an NF3 atmosphere and held for 20-60 minutes. After cooling, surface-passivated molecular sieves are obtained. Preferably, the molecular sieves are heated to 310-325°C in an NF3 atmosphere. In one embodiment, 5A molecular sieves are heated to 320°C in an NF3 atmosphere and held for 30 minutes. After cooling, surface-passivated molecular sieves are obtained. As a further improvement, in one embodiment, the NF3 atmosphere is diluted with an inert gas such as nitrogen and used as a gas source (the volume ratio of NF3 in the gas source is controlled between 40-60%). This is because HF is generated during the reaction, and this HF can be diluted and discharged with nitrogen. As a further improvement, in one embodiment, after the reaction is completed and before cooling, the modified molecular sieve is purged with an inert gas such as nitrogen at a high temperature (320°C) for 5-10 minutes, and then cooled to obtain surface-passivated molecular sieves.

[0031] As a further improvement, in another embodiment, the modified molecular sieve is obtained by the following method: An NF3 atmosphere is introduced into the molecular sieve during the calcination process, and the sieve is then cooled to obtain a surface-passivated molecular sieve. The preparation of molecular sieves generally includes steps such as synthesis, ion exchange, washing, granulation, and calcination. This invention innovatively introduces an NF3 atmosphere during the calcination process of the molecular sieve, thereby reducing the number of preparation steps and improving production efficiency. Specifically, since the calcination process of molecular sieves is generally long (more than 3 hours), it is preferable to introduce an NF3 atmosphere in the later stages of the calcination process, which can greatly reduce the interference of the NF3 atmosphere on the molecular sieve preparation process.

[0032] As a further improvement, in one embodiment, the molecular sieve may be a type A molecular sieve, such as a 3A molecular sieve, a 4A molecular sieve, and a 5A molecular sieve.

[0033] By passivating some of the silanol groups (Si-OH) on the surface of the molecular sieve with NF3 at high temperature to form (Si-OF), the number of active sites on the surface is reduced, preventing irreversible adsorption loss of silanol groups and SOF2. Small-scale tests show that the modified molecular sieve of this invention can increase the yield of SOF2 by 3-5%. Furthermore, it can also extend the service life of the modified molecular sieve.

[0034] Molecular sieves are primarily used to remove trace amounts of moisture, while silica gel possesses excellent polar adsorption properties, capable of adsorbing residual trace amounts of hydrogen chloride, heterocyclic gases, and other polar impurities. To ensure stable adsorption efficiency, each adsorption bed is equipped with inlet and outlet thermocouples and differential pressure sensors to enable online monitoring of adsorption dynamics. When an increase in differential pressure or a decrease in discharge purity is detected, a three-way switching valve can be used to switch to a standby adsorption bed, allowing for replacement or desorption without shutting down the system.

[0035] S7. Product Collection: The thionyl fluoride product, after adsorption and purification, enters the final storage unit. The storage tank is made of stainless steel and has an internal nitrogen-sealing interface to maintain positive pressure and prevent air backflow. It is equipped with a pressure relief device and vent pipe at the top, and a level gauge and drain port at the bottom. To avoid safety hazards caused by overpressure or overfilling, the tank is equipped with high and low level alarms, and the upstream pumping rate can be adjusted in conjunction with the automatic control system. The final collected product has a stable purity exceeding 99.999% and can be directly used in electronic-grade fluorochemical processes or as a raw material for downstream fine synthesis.

[0036] Example 2 This embodiment provides a system for the combined purification of thionyl fluoride through multi-stage distillation and adsorption. Based on the principle of gas distillation separation combined with fixed-bed adsorption purification technology, this system can achieve deep removal of various impurities from the thionyl fluoride feed gas and recovery of high-purity products. The entire system has a reasonable structure and stable module coordination, making it suitable for continuous industrial-scale preparation processes of high-purity thionyl fluoride.

[0037] The system mainly comprises six functional modules: a raw material gas feeding unit, a first distillation column unit, a second distillation column unit, a condensation unit, an adsorption unit, and a product storage tank unit. These units are connected by stainless steel welded pipelines, forming a closed and continuous purification main process. All pipe fittings and equipment components in contact with corrosive media are equipped with anti-corrosion linings or made of corrosion-resistant alloy materials. Key nodes are equipped with pressure monitoring devices, temperature control units, and online detection and sampling ports, facilitating real-time operation monitoring and quality traceability.

[0038] Raw material gas feeding unit: This unit is used to vaporize, temperature-regulate, and pressure-stabilize the feed gas from the upstream thionyl fluoride reaction system or storage tank, and then feed it into the first distillation column in a stable state. Its main equipment consists of: Raw material buffer tank: Adopting a vertical-horizontal composite structure, the tank body is made of stainless steel and equipped with a level sensor, anti-backflow check valve, and outlet backpressure suppression device. Its function is to buffer fluctuating feed and ensure stable gas intake for the distillation system.

[0039] Vaporizer: A shell-and-tube steam jacketed vaporization device that uses saturated steam to provide heat, ensuring that the liquid raw material is completely converted into superheated gas at the vaporizer outlet, with the outlet temperature controlled at 60-70℃.

[0040] High-efficiency heat exchanger: It adopts a plate structure to further exchange heat on the gasified raw material gas, ensuring that its temperature is maintained between 50 and 80°C, while regulating temperature fluctuations through bypass cooling water.

[0041] Mass flow controller (MFC): Used for precise control of feed flow rate, equipped with automatic closing valve, fault alarm module, and linkage adjustment with upper control system.

[0042] Pressure regulating valve group: stabilizes the system pressure within the range of 0.1 to 0.3 MPa to ensure the stability of the operating pressure of the downstream distillation column.

[0043] First distillation column unit: This unit is the main coarse separation tower section, used to remove low-boiling-point impurities such as hydrogen chloride and water vapor. Its structural parameters and configuration are as follows: Tower structure: It adopts a vertical cylindrical tower body with a diameter of Φ300 mm and a height of 10 m. The material is 304 stainless steel, and it is wrapped with thermal insulation cotton and covered with a corrosion-resistant polytetrafluoroethylene protective layer.

[0044] Internal packing: Filled with structured corrugated stainless steel packing, with a packing section height of 5 m and a specific surface area of ​​approximately... The tower is equipped with one liquid redistribution plate and two layers of redistributors to ensure that the liquid is evenly distributed on the surface of the packing.

[0045] Tower bottom heating system: Equipped with an electric heating tube bundle jacket, it can output stable heat to maintain the tower bottom temperature within the range of 80-120℃.

[0046] Top-of-tower condenser: It is a shell-side cooling structure with circulating water as the cooling medium. The reflux ratio is adjustable (default setting is 3:1). The condensate is returned to the top of the tower through a liquid seal tank.

[0047] Control and monitoring devices: Thermocouples and pressure sensors are installed at the top and bottom of the tower, respectively. Sight glasses and sampling ports are installed on the side walls of the tower. All data is centrally connected to the DCS system for unified monitoring.

[0048] Second distillation column unit: This unit is responsible for the efficient removal of near-boiling-point impurities from the intermediate product, and is a key step in improving the final purity of thionyl fluoride. The configuration is as follows: Double-layer tower structure: the inner layer is lined with polytetrafluoroethylene (PTFE) and the outer layer is made of 316L stainless steel. The tower diameter is Φ200mm and the height is 8m. It has extremely strong resistance to fluorine corrosion.

[0049] Packing system: The internal filling is a stepped ring bulk packing material made of PTFE. The packing section height is 6 m, which is suitable for high-precision mass transfer separation.

[0050] Multi-point temperature sensor array: Six sets of thermocouple nodes are distributed along the height of the tower to realize real-time dynamic acquisition of temperature gradient inside the tower.

[0051] Heat transfer oil heating system: The bottom of the tower is equipped with a jacketed heating structure, and the temperature control range of the heat transfer oil is 70~100℃. The heat load is dynamically adjusted by the PID control module.

[0052] Top product outlet: The top pressure of the column is stabilized by an automatic back pressure valve and connected to the inlet of the condensation unit to ensure continuous and stable feed.

[0053] Condensation unit: This unit is used to rapidly condense the high-purity thionyl fluoride gas output from the top of the distillation column into a liquid, providing a stable feedstock for the subsequent adsorption module. The configuration is as follows: Shell-and-tube condenser: adopts a multi-tube bundle parallel structure, with ethanol-salt water mixed refrigerant on the shell side, and the cooling medium temperature is set between -5 and +5℃.

[0054] Flow and temperature difference monitoring system: Equipped with flow meters and temperature difference sensors at the inlet and outlet to ensure real-time feedback of condenser efficiency and automatically adjust refrigeration power.

[0055] Condensate buffer tank: Equipped with an automatic liquid level control device and nitrogen sealing protection to prevent gas-liquid fluctuations from interfering with the adsorption pump flow rate.

[0056] Anti-backflow structure: A one-way check valve and a gas-liquid separator are installed between the condenser and the adsorption device to ensure the safety and stability of the system.

[0057] Adsorption unit: To achieve deep removal of polar residual impurities such as hydrogen chloride and water vapor, the following configuration is used: The three-stage adsorption towers T4, T5, and T6 are arranged in series: each adsorption tower has an inner diameter of Φ200 mm, a height of 2 m, and the shell is made of 304 stainless steel with a thickness of not less than 4 mm.

[0058] Adsorbent material: pretreated modified 5A molecular sieve and spherical silica gel with a particle size of 2-3 mm, a filling height of 1.2 m, and a mixing mass ratio of 1:1.

[0059] Structural design: The upper part of the cylinder is equipped with an observation window, a safety pressure relief hole, an N2 backflush port and a quick-release manhole; the lower part is equipped with a flow guide baffle and a flow equalization plate to ensure that the gas passes through the cross section evenly.

[0060] Adsorption-regeneration switching module: Two adsorption units operate alternately. When the main unit is saturated with adsorption, the standby unit automatically takes over. The original unit is regenerated in situ by hot air and nitrogen backflushing. The switching process does not require shutdown.

[0061] Differential pressure monitoring device: installed at the inlet and outlet of the adsorption bed to detect bed blockage or abnormal pressure drop in real time.

[0062] Product storage tank unit: The final product is introduced into a high-purity storage tank after adsorption. Tank structure: made of stainless steel, with a volume of 1 m³, equipped with a nitrogen protection port and a pressure relief valve.

[0063] Liquid level monitoring: High and low liquid level alarms and liquid level gauges are installed, and the output signals can be linked to control the speed of the upstream pump.

[0064] Discharge interface: The bottom is equipped with a discharge valve, sampling port and vacuum extraction pipe for periodic testing or filling operations.

[0065] In summary, this embodiment of the system possesses technical characteristics such as multi-point temperature control, intelligent feedback regulation, efficient condensation, precise separation, and continuous adsorption. It enables stable, efficient, and automated purification of thionyl fluoride raw materials, meeting the stringent requirements for the preparation of high-end electronic chemicals and pharmaceutical-grade fluorine sources. The system's modular design facilitates maintenance, expansion, and industrial-scale replication, demonstrating excellent engineering adaptability and application prospects.

[0066] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for purifying thionyl fluoride using a combination of multi-stage distillation and adsorption, characterized in that, Includes the following steps: S1. Feed gas: A mixed gas containing thionyl fluoride, hydrogen chloride, water vapor, unreacted raw materials and by-products is introduced into the bottom of the first-stage distillation column as feed after heat exchange. S2, First-stage distillation: In the first-stage distillation column, by setting the bottom temperature to 80-120℃ and the top temperature to 30-60℃, multi-stage thermal separation is carried out in the column, so that low-boiling impurity components escape with the top gas and the bottom is enriched with thionyl fluoride and high-boiling impurities. S3. Extraction and separation: Extract the distillation intermediate at the outlet of the first-stage distillation column, controlling the extraction temperature range to be 40-70℃, in which the concentration of thionyl fluoride accounts for more than 80% of the total gas. S4. Second-stage distillation: The intermediate product is introduced into the second-stage distillation column, and the top temperature of the column is adjusted to 20-40°C and the bottom temperature is adjusted to 70-100°C. The mass transfer efficiency is enhanced by the precision packing in the column, boiling point impurities are removed, and thionyl fluoride top gas with a purity of not less than 99.95% is obtained. S5. Gas condensation: The gas from the top of the second-stage distillation column is introduced into a shell-and-tube condenser and subjected to phase change condensation at -5℃ to +5℃ to obtain crude liquid thionyl fluoride. S6. Adsorption and purification: The condensed crude thionyl fluoride is fed into an adsorption device equipped with fixed-bed adsorption material via a metering pump to remove residual hydrogen chloride and trace amounts of moisture. The operating temperature is controlled at 20-35℃ and the tower pressure is maintained at atmospheric pressure to 0.2 MPa. S7. Product Collection: The adsorption-treated thionyl fluoride is introduced into a nitrogen-sealed stainless steel storage tank. The storage tank is equipped with high and low liquid level alarms and an exhaust circuit. The purity of the collected product is higher than 99.999%. The first-stage distillation column packing is a structured metal packing made of 304 or 316L stainless steel. The packing unit structure is a corrugated perforated plate form with a specific surface area of ​​200-350 m² / m³, a bulk density of 150-300 kg / m³, a column packing section height of 4-6 meters, and is equipped with a liquid distributor, a redistributor, and a support device. The theoretical number of trays is not less than 90. The column is equipped with a temperature detection point and a column top reflux ratio adjustment mechanism. The second-stage distillation column is internally designed with a bulk packing structure. The packing is made of polytetrafluoroethylene Pall rings or stepped rings. The height of the packing section is 9 to 12 meters. The column wall is equipped with an insulation layer and a temperature-controlled electric heating belt. A condensate reflux tank is installed at the top of the column, and the reflux ratio is controlled by an automatic regulating valve. A high-precision level gauge and a heating jacket are installed at the bottom of the column. The shell-and-tube condenser adopts a multi-tube bundle design, and the cooling medium is an ethanol-salt water mixture coolant at -5℃ to 5℃. The shell side is made of stainless steel, and the fluid velocity inside the tube is 0.5~1.5 m / s. It is equipped with an inlet and outlet temperature difference detection device and a condensation efficiency feedback device. A buffer collection tank and a liquid level sensor are installed at the condenser outlet to control the subsequent delivery rhythm. The adsorption device includes two adsorption units arranged in parallel. Each adsorption unit includes three adsorption towers (T4, T5, and T6) arranged in series. The filling height of each adsorption tower is 1.0 to 1.5 meters. The internal packing material is modified molecular sieve and medium-pore spherical silica particles with a particle size range of 1.5 to 3.0 mm. It is equipped with inlet and outlet temperature monitoring points and differential pressure monitoring devices. The adsorption bed operation cycle is 100 to 200 hours. Switching is performed online through a three-way valve without interrupting the purification process.

2. A system for the multi-stage distillation and adsorption combined purification of thionyl fluoride using the method of claim 1, characterized in that, The system includes a raw material gas feeding unit, a first distillation column unit, a second distillation column unit, a condensation unit, an adsorption unit, and a product storage tank unit, which are connected in sequence to form the main process for thionyl fluoride purification. Each unit is equipped with pressure monitoring, temperature regulation, and anti-corrosion lining materials. The connecting pipelines are made of stainless steel welded connections and are equipped with online sampling ports and testing interfaces.

3. The system for the combined purification of thionyl fluoride by multi-stage distillation and adsorption according to claim 2, characterized in that, The feed gas unit includes a vaporizer, a heat exchanger, a mass flow controller, a feed buffer tank, and a pressure regulating valve. The vaporizer is equipped with a steam jacket, and the heat exchanger is a high-efficiency plate heat exchanger. The feed gas temperature is controlled between 50 and 80°C, and the pressure is controlled between 0.1 and 0.3 MPa. The buffer tank is equipped with an anti-backflow check valve and a back pressure suppression device. After heat exchange, the gas enters the bottom of the first distillation column.

4. The system for the combined purification of thionyl fluoride by multi-stage distillation and adsorption according to claim 2, characterized in that, The first distillation column unit adopts a vertical column structure with a height of 8-12 m. The column body is made of 304 stainless steel and filled with stainless steel structured packing. It is equipped with a liquid redistribution plate and a spray reflux device. The bottom of the column is equipped with an electric heating tube bundle jacket, and the top of the column is equipped with a shell-side condenser and a reflux tank. It is equipped with an automatic temperature control module for the top and bottom of the column and a reflux ratio adjustment actuator.

5. The system for the combined purification of thionyl fluoride by multi-stage distillation and adsorption according to claim 2, characterized in that, The second distillation column unit adopts a double-layer structure, with an inner anti-corrosion PTFE lining and an outer 316 stainless steel lining. The column is equipped with a multi-segment temperature sensor array for multi-point temperature monitoring. The gas outlet at the top of the column is connected to the condenser. An automatic liquid level control buffer tank is installed after the condenser. The bottom of the column is equipped with a heat transfer oil jacket and a heat medium temperature control valve, which can achieve fine heating regulation through PID control algorithm.

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