A device and process for the purification of trisilane

Abstract

The application discloses a device and a process for purifying propylsilane, and relates to the technical field of propylsilane purification, which comprises a crude propylsilane feeding pipeline, through which crude propylsilane after synthesis is fed; a rectifying tower kettle for receiving and evaporating the crude propylsilane raw material; a rectifying tower for realizing preliminary separation of light components and propylsilane; a first-stage condenser, the gas inlet of which is communicated with the tower top gas outlet of the rectifying tower, for condensing propylsilane and making most of the gas phase rise to a second-stage condenser; the second-stage condenser, the gas inlet of which is communicated with the outlet of the first-stage condenser, for further condensing propylsilane in the remaining gas phase; and a first-stage condensate reflux pipeline for receiving the condensate of the first-stage condenser, part of which is returned to the tower top of the rectifying tower through the reflux pipeline. The application can realize the separation effect close to that of a multi-tower series under the premise of single-tower lower energy consumption, and further divides the two stages of high-purity extraction and recovery extraction by cooperating with intermittent rectification, so that high extraction rate and high purity are realized in the single tower.

Description

Technical Field

[0001] This invention relates to the field of propane purification technology, specifically to an apparatus and process for purifying propane. Background Technology

[0002] Propylene silane, as a new generation of silicon-based thin film deposition precursor, has wide applications in semiconductors, flat panel displays, and photovoltaic cells. Industrially, propylene silane is often prepared using the Komatsu process. Propylene silane has a boiling point of 52.9℃, but the product often contains impurities such as silane, disilane (boiling point -14.3℃), and light components like hydrogen and nitrogen. These impurities severely affect the purity of propylene silane, thus impacting the quality of the thin films in downstream deposition processes. The semiconductor industry requires propylene silane purity of 99.99% (4N grade) or higher, and the content of key impurities must be strictly controlled at the ppm or even ppb level.

[0003] Currently, all publicly available propane purification technologies employ multi-tower series distillation processes. A representative technology, such as the silane production process disclosed in Chinese patent CN114436264A, uses a four-tower series structure consisting of a hydrogen removal tower, a silane removal tower, an ethyl silane tower, and a propane tower. These technologies generally suffer from high equipment investment, complex process flow, large amounts of propane silane being emitted with the non-condensable gas at the top of the multiple towers, and significant raw material loss.

[0004] Two prevalent technical biases have long existed in this field: First, the boiling points of silane (boiling point -112℃), disilane (boiling point -14.3℃), propane (boiling point 53℃), and hydrogen and nitrogen in crude propane are considered to differ significantly, leading to a preference for using multiple towers in series to remove these lighter components separately. Second, existing processes are less likely to use the secondary condensate return operation due to concerns about the enrichment of lighter components during circulation and temperature fluctuations in the tower bottom. These biases severely hinder the advancement of propane purification technology, and the industry urgently needs a purification technology that is simple, energy-efficient, has a high yield, and can stably produce 4N-grade propane. Summary of the Invention

[0005] The purpose of this invention is to provide an apparatus and process for purifying propane, so as to overcome the shortcomings of the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: an apparatus for purifying propane, comprising:

[0007] The crude propane feed line is where the synthesized crude propane enters;

[0008] The distillation column reboiler is used to receive and evaporate crude propane feedstock;

[0009] A distillation column is used to achieve the initial separation of light components from propanesilane;

[0010] The first-stage condenser has its inlet connected to the outlet at the top of the distillation column, and is used to condense propane and allow most of the gas phase to rise to the second-stage condenser.

[0011] The second-stage condenser has its inlet connected to the outlet of the first-stage condenser and is used to further condense the propane silane in the remaining gas phase.

[0012] The primary condensate return line and product collection line receive the condensate from the primary condenser. Part of the condensate is returned to the top of the distillation column through the primary condensate return line, and the other part is collected into the silane finished product tank through the product collection line.

[0013] The secondary condenser reflux line receives the condensate from the second-stage condenser and returns it to the distillation column bottoms via the reflux line;

[0014] The non-condensable gas discharge pipeline is connected to the outlet of the second-stage condenser to discharge non-condensable gases.

[0015] Preferably, the distillation column reboiler is equipped with a buffer evaporator for temporarily storing the condensate from the second-stage condenser. This buffer evaporator has an inlet and an outlet; the outlet is connected to the vapor phase space of the distillation column reboiler via a valve, and the inlet is connected to the secondary condensate reflux pipeline. The buffer evaporator is a double-layered container, with a volume of 10% to 20% of the effective volume of the distillation column reboiler. The inlet is connected to the secondary condensate reflux pipeline, and a liquid spray distributor is used to ensure uniform distribution of the secondary condensate within the tank. The outlet is connected to the vapor phase space of the distillation column reboiler via a pneumatic diaphragm regulating valve. The buffer evaporator is equipped with a differential pressure level gauge and a temperature sensor to monitor the liquid level and material temperature within the tank, respectively.

[0016] A process for purifying propane includes the following steps:

[0017] S1. Add crude propane feedstock to the distillation column reboiler, heat the distillation column reboiler to 50~65℃, and establish the total reflux operation of the distillation column;

[0018] S2, under the conditions of a first-stage condenser temperature of 30~50℃ and a second-stage condenser temperature of -20~10℃, close the exhaust valve of the buffer evaporator, receive and temporarily store the condensate from the second-stage condenser, and carry out the high-purity extraction stage; extract silane product from the condensate of the first-stage condenser.

[0019] S3, when the temperature at the top of the distillation column rises by ≥1℃ and the pressure at the top of the column drops by ≥15%, open the exhaust valve of the buffer evaporator to release the preheated gaseous material in the tank into the distillation column kettle;

[0020] S4, maintain the cooling temperature of the second-stage condenser at -5°C. As the cycle is established, a small amount of tail gas enriched with silane is discharged through the non-condensable gas discharge line in each cycle, and the product is collected from the first-stage condenser.

[0021] S5, wherein the reflux ratio in S2 is the mass ratio of the reflux flow rate in the primary condensate reflux pipeline to the product output flow rate in the product output pipeline, which is 5:1 to 20:1.

[0022] Preferably, the distillation column has 30 to 60 theoretical plates and an operating pressure of 0.1 to 0.5 MPa absolute pressure.

[0023] Preferably, the top operating temperature of the distillation column (2) in S1 is -20°C to 10°C, and the bottom operating temperature of the distillation column is 50°C to 65°C.

[0024] Preferably, the condensate temperature of the first-stage condenser is controlled at 40°C. 40°C is a preferred value; however, those skilled in the art will understand that other temperature values ​​within the range of 30°C to 50°C can also achieve the technical effects of this invention.

[0025] Preferably, in step S2, the condensate temperature of the second-stage condenser is controlled at -10°C. -10°C is a preferred value, but those skilled in the art will understand that other temperature values ​​within the range of -20°C to -10°C can also achieve the technical effects of the present invention.

[0026] Preferably, the release rate of gaseous material in the buffer evaporator is controlled so that the gaseous material preheated to 48~62℃ in the tank is slowly released within 15~30 minutes; during the release process, the newly added condensate from the second-stage condenser enters the buffer evaporator at the same time.

[0027] Preferably, the tail gas emission ratio of ethyl silane is 0.5%-5% of the total mass of ethyl silane in the crude propane feedstock.

[0028] In the above technical solution, the apparatus and process for purifying propane provided by the present invention have the following beneficial effects:

[0029] 1. By combining a single tower with a two-stage condensation temperature gradient and differentiated reflux, a separation effect close to that of multiple towers in series can be achieved within a single tower;

[0030] 2. Furthermore, by installing a buffer evaporator inside the distillation column, the second-stage condensate rich in light components is temporarily stored and preheated, eliminating the temperature shock in the column bottom caused by direct reflux of low-temperature liquid and stabilizing the heating system.

[0031] 3. By utilizing phased operation, the batch distillation is further divided into two stages: high-purity extraction and recovery extraction. Under the premise of a single tower and ensuring a high extraction rate, silane products with a purity of ≥99.995% (4N grade) and ≥99.991% (4N grade) can be obtained respectively. In step S4, silane can be extracted from the non-condensable gas discharge pipeline, so as to achieve low energy consumption, single tower, high extraction of 4N grade silane and high-purity silane. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0033] Figure 1 This is a schematic diagram of an apparatus for purifying propane according to the present invention;

[0034] Figure 2 A schematic diagram of a buffer evaporator and a distillation column reboiler;

[0035] Figure 3 This is a chromatogram of Example 1 of the present invention.

[0036] Explanation of reference numerals in the attached diagram: 1. Distillation column reboiler; 2. Distillation column; 3. First-stage condenser; 4. Second-stage condenser; 5. First-stage condensate reflux line; 6. Non-condensable gas discharge line; 7. Product collection line; 8. Propylene silane finished product tank; 9. Second-stage condensate reflux line; 10. Crude propyne silane feed line; 11. Buffer evaporator; 111. Liquid inlet; 112. Exhaust port. Detailed Implementation

[0037] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0038] This embodiment of the invention is a basic implementation of the invention, and the apparatus and process parameters are as follows:

[0039] This Example 1 is a basic implementation of the present invention, and the apparatus and process parameters are as follows:

[0040] Theoretical trays of distillation column 2: 40

[0041] Operating pressure of distillation column 2: 0.3 MPa absolute pressure;

[0042] First-stage condenser 3: Cooling medium temperature: 40℃

[0043] Second-stage condenser 4: Cooling medium temperature: S2-10℃, S4-5℃

[0044] Heating temperature of distillation column reboiler 1: 58℃

[0045] The ratio of return flow to produced flow is 10:1.

[0046] Composition of crude propane raw material: 85wt% propane, 10wt% ethyl silane, 4wt% silane, and 1wt% total content of hydrogen, nitrogen, and heavy silane.

[0047] The purification process steps are as follows:

[0048] S1, add the above-mentioned crude propane raw material to the distillation column 1, heat the distillation column 1 to 58°C, establish the total reflux operation of the distillation column 2, and the operating temperature of the top of the column is 0°C;

[0049] S2, under the two-stage condensation conditions of the first-stage condenser 3 at 40℃ and the second-stage condenser 4 at -10℃, the exhaust valve of the buffer evaporator is closed, the condensate from the second-stage condenser 4 is received and temporarily stored, and the high-purity extraction stage is entered. The product is extracted from the first-stage condenser 3 at a reflux ratio of 10:1, which lasts for about 4 hours.

[0050] S3, when the temperature at the top of the distillation column 2 rises by 1°C, the high-purity extraction stage is considered to be over; open the exhaust valve of the buffer evaporator 11 and slowly release the gaseous material preheated to above 53°C in the reboiler into the distillation column 1. The release process lasts for about 20 minutes.

[0051] S4, the cooling temperature of the second-stage condenser 4 is raised from -10℃ to -5℃, and the tail gas enriched with silane is continuously discharged through the non-condensable gas discharge pipeline 6 for 30 minutes. The first-stage condenser 3 collects the product and obtains 4N grade propane silane. This process lasts for about 1 hour. During this stage, the temperature of the second-stage condenser 4 is raised to -5℃, which promotes the discharge of silane.

[0052] S5 maintains a reflux ratio of 10:1 throughout the entire extraction phase.

[0053] Testing revealed that the purity of the 4N-grade propane product obtained in stage S2 of this embodiment was 99.996%, and the purity of the 4N-grade propane product obtained in stage S4 was 99.993%. The overall product yield was 96.8%, the energy consumption per unit product was 0.75 kWh / kg, the temperature fluctuation in the reboiler was ±0.05℃, and the power fluctuation of the heating system was <1%.

[0054] Example 2:

[0055] This embodiment optimizes parameters for low-purity crude propane feedstock. The equipment and process parameters are as follows:

[0056] Theoretical tray number of distillation column 2: 60;

[0057] Operating pressure of distillation column 2: 0.5 MPa absolute pressure

[0058] First-stage condenser 3: Cooling medium temperature: 50℃

[0059] Second-stage condenser 4 cooling medium temperature: -5℃ (S2 stage) / -2℃ (S4 stage)

[0060] Heating temperature of distillation column reboiler 1: 65℃

[0061] The ratio of return flow to produced flow is 20:1.

[0062] The crude propane feedstock composition is as follows: propane 65wt%, ethyl silane 20wt%, silane 10wt%, hydrogen, nitrogen and heavy silane total content 5wt%, and the tower top operating temperature is 10℃.

[0063] The purification process was the same as in Example 1. Testing showed that the purity of the 4N-grade product in stage S2 was 99.996%, and the purity of the 4N-grade product in stage S4 was 99.991%. The overall product yield was 95.0%, and the energy consumption per unit product was 0.85 kWh / kg.

[0064] Example 3:

[0065] Based on Example 1, this embodiment further optimizes the structure and stage switching logic of the buffer evaporator 11 to demonstrate the best effect.

[0066] The buffer evaporator 11 is a double-layered container tank. The volume of the buffer evaporator is 10% to 20% of the effective volume of the distillation column reboiler 1. The liquid inlet 111 is connected to the secondary condenser reflux line 9. A liquid spray distributor is used to ensure that the secondary condensate is evenly distributed in the tank. The exhaust port 112 is connected to the gas phase space of the distillation column reboiler 1 through a pneumatic diaphragm regulating valve. The buffer evaporator is equipped with a differential pressure level gauge and a temperature sensor, which are used to monitor the liquid level and material temperature in the tank, respectively. In stage S2, the exhaust port 112 valve is closed, and the low-temperature condensate generated by the second-stage condenser 4 continues to enter the buffer evaporator 11. The liquid level in the tank gradually rises and is preheated to near the temperature in the column reboiler through heat conduction. Since the exhaust port is closed, the pressure in the tank increases, and the liquid remains in a liquid state and does not boil.

[0067] The temperature at the top of the column rises by 1.0°C from the steady-state value, triggering step S3. The valve at the exhaust port 112 opens, the pressure inside the tank drops, the preheated liquid flashes, and the light components enter the gas phase space at the bottom of the column from the exhaust port 112. They then enter the distillation column 2 with the rising gas flow and are finally discharged from the top of the column.

[0068] The exhaust valve 112 remains open, allowing secondary condensate to continue entering, but the material evaporates as it enters, with light components continuously being discharged from the top of the tower;

[0069] Testing revealed that the purity of the 4N-grade product in stage S2 reached 99.998%, and the purity of the 4N-grade product in stage S4 reached 99.993%. The overall product yield increased to 97.2%, and the energy consumption per unit product decreased to 0.72 kWh / kg. After establishing a complete cycle, the temperature fluctuation in the reboiler was only ±0.03℃.

[0070] Example 4:

[0071] This embodiment optimizes and verifies the release rate of gaseous materials in the buffer evaporator based on Embodiment 1. The device structure and process steps are the same as in Embodiment 1, except for the release parameters of the gaseous materials in the buffer evaporator in stage S3: the preheating temperature of the buffer evaporator is 55°C and the release time is 25 minutes; during the release process, the newly added condensate from the second-stage condenser is simultaneously pumped into the buffer evaporator 11, and the remaining process parameters are consistent with those in Embodiment 1.

[0072] Testing revealed that the purity of the silane product extracted in stage S2 of this embodiment was 99.997%, and the purity of the silane product extracted in stage S4 was 99.994%. The overall product yield was 97.0%, and the energy consumption per unit product was 0.73 kWh / kg. During the release process, the temperature fluctuation in the bottom of the tower was ±0.04℃. By controlling the release rate, the thermal stability of the bottom of the tower was ensured while effectively transferring the gaseous material enriched with light components in the buffer tank to the bottom of the tower.

[0073] Comparative Example 1:

[0074] By employing the same single-tower distillation apparatus as in Example 1, but with only a single-stage condenser, all condensate is refluxed to the top of the column, and non-condensable gases are directly discharged. Process parameters: 80 theoretical plates, reflux ratio 30:1, reboiler heating temperature 58°C, condenser temperature -10°C;

[0075] The same crude raw material as in Example 1 was used for purification. Testing revealed that only one product could be obtained, with a purity of 99.87%, a product yield of 76.5%, and an energy consumption of 1.42 kWh / kg per unit product.

[0076] Comparative analysis: Even with higher tray numbers and reflux ratios, conventional single-tower single-stage condensation processes still cannot achieve 4N-level purity, and have low yields and high energy consumption.

[0077] Comparative Example 2-1:

[0078] The design incorporates a bufferless evaporator and staged operation, employing the same two-stage condenser structure as in Example 1. The crude silane feedstock consists of 85 wt% silane, 10 wt% ethyl silane, 4 wt% silane, and 1 wt% total content of hydrogen, nitrogen, and heavy silane. However, the design does not include a bufferless evaporator 11, and the second-stage condensate is directly and continuously refluxed to the bottom of the tower. Furthermore, no staged operation or heating and discharge are performed throughout the entire process.

[0079] Comparative Example 2-2:

[0080] The design incorporates a bufferless evaporator and staged operation, employing the same two-stage condenser structure as in Example 2. The crude propane feedstock consists of 65wt% propane, 20wt% ethane, 10wt% silane, and 5wt% total content of hydrogen, nitrogen, and heavy silane. The top operating temperature is 10°C, but without a buffer evaporator 11, the second-stage condensate is directly and continuously refluxed to the bottom of the column, and no staged operation or temperature rise discharge is performed throughout the process.

[0081] Comparative analysis:

[0082] The process parameters of Comparative Example 2-1 are exactly the same as those of Example 1. In this comparative example, 10 wt% silane has a small temperature impact after reflux in the reboiler, and the product purity is 99.992%, which meets the standard.

[0083] The process parameters of Comparative Example 2-2 are exactly the same as those of Example 2. In this comparative example, 20wt% of silane is used, which is a high proportion and causes a large temperature impact after reflux. The product purity is only 95.91%, and the impurities are seriously excessive. The product yield is 88.7%, the energy consumption per unit product is 1.15kWh / kg, and the temperature fluctuation of the tower bottom is as high as ±1.5℃ during operation.

[0084] Comparative Example 2-2 directly demonstrates that without the temporary storage and preheating of a buffer evaporator, the large amount of low-temperature reflux generated when dealing with low-purity crude propane feedstock will impact the stability of the reboiler. More importantly, a large amount of silane will continuously circulate and accumulate within the system, ultimately leading to a serious deficiency in product purity. This conversely proves the necessity of adding a buffer evaporator when dealing with low-purity crude propane feedstock in this invention.

[0085] The comparison between the above embodiments and comparative examples shows that the present invention achieves deep removal of multiple light components through a single tower; the overall product yield is significantly increased to over 95%, and with the temperature control and buffer settings of the two-stage condenser, the production of 4N grade propane silane products can be realized in a single-tower distillation process, reaching 97.2% in the optimized embodiment. This significantly reduces raw material loss, and the energy consumption per unit product is reduced from 1.2-1.4 kWh / kg in the prior art to 0.72-0.85 kWh / kg, demonstrating significant energy-saving effects.

[0086] Comparative Example 3:

[0087] The same apparatus, crude raw materials and process steps as in Example 3 were used, the only difference being that the release time of the gaseous material in the buffer evaporator in stage S3 was less than one minute.

[0088] The following problems occurred during operation: a large amount of gaseous material rushed into the bottom of the column in a short period of time, causing the temperature of the bottom of the column to fluctuate by as much as ±2.0℃. As the temperature fluctuation of the bottom of the column disrupted the balance in the distillation column, a large amount of silane was released into distillation column 2 in a short period of time. The silane was extracted in the S3 stage, resulting in the product purity dropping to 99.2% and the product yield being only 82.3%. A large amount of propane was lost with the non-condensable gas and the operation fluctuations.

[0089] Comparative analysis: Comparative example 3 directly proves that when the release rate is too high, even if the preheating temperature is controlled within a reasonable range, a large amount of gaseous material entering the tower in a short period of time will still cause serious operational fluctuations, resulting in unqualified product purity, decreased yield, and increased energy consumption.

[0090] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. An apparatus for purifying propane, comprising: Crude propane feed line (10); The distillation column reboiler (1) is used to receive the crude propane feedstock transported in the crude propane feed line (10) for evaporation; Distillation column (2) is used to achieve the initial separation of light components from propanesilane; Its characteristic is that it further includes: The first-stage condenser (3) has its inlet connected to the top outlet of the distillation column (2) and is used to condense propane and make most of the gas phase rise to the second-stage condenser (4). The second-stage condenser (4) has its inlet connected to the gas phase outlet of the first-stage condenser (3) for further condensing the silane in the remaining gas phase. The first-stage condensate return line (5) and the product collection line (7) are used to return part of the condensate from the first-stage condenser (3) to the top of the distillation column (2) through the first-stage condensate return line (5) and the other part is collected through the product collection line (7). The secondary condensate reflux line (9) receives the condensate from the second-stage condenser (4) and sends the condensate back to the distillation column bottom (1). The non-condensable gas discharge line (6) is connected to the outlet of the second-stage condenser (4) for non-condensable gas discharge.

2. The apparatus for purifying propane according to claim 1, characterized in that, The distillation column reboiler (1) is equipped with a buffer evaporator (11) for temporarily storing the condensate of the second-stage condenser (4). The buffer evaporator is equipped with an inlet (111) and an outlet (112). The outlet (112) is connected to the gas phase space of the distillation column reboiler (1) through a valve. The inlet (111) is connected to the secondary condenser reflux pipeline (9).

3. A process for purifying propane, using the apparatus for purifying propane as described in claim 2, characterized in that, Includes the following steps: S1, add crude propane raw material to the distillation column (1), heat the distillation column (1) to 50~65℃, and establish the total reflux operation of the distillation column (2); S2, under the conditions of 30~50℃ for the first stage condenser (3) and -20~-10℃ for the second stage condenser (4), close the exhaust valve of the buffer evaporator, receive and temporarily store the condensate from the second stage condenser (4), and carry out the high-purity extraction stage; extract silane product from the condensate of the first stage condenser (3); S3, when the stage switching conditions are met, the buffer release stage is entered; the stage switching conditions include at least one of the following: change in tower top temperature, change in tower top pressure, change in tower top light component content, change in purity of extracted product, cumulative extraction amount or running time; when entering the buffer release stage, the exhaust port (112) valve of the buffer evaporator is opened, and the preheated gaseous material in the tank is released into the distillation column bottom (1). S4, maintain the cooling temperature of the second-stage condenser (4) at -5°C, and discharge a small amount of tail gas enriched with silane through the non-condensable gas discharge line (6) during each reflux, and extract the product from the first-stage condenser (3). S5, wherein the reflux ratio in S2 is the mass ratio of the reflux flow rate in the primary condensate reflux pipeline (5) to the output flow rate in the product output pipeline (7) of 5:1 to 20:

1.

4. The propylene silane purification process according to claim 3, characterized in that, The theoretical number of plates in the distillation column (2) is 30 to 60, and the operating pressure is 0.1 to 0.5 MPa absolute pressure.

5. The propylene silane purification process according to claim 3, characterized in that, The operating temperature of the top of the distillation column (2) in S1 is -20℃ to 10℃, and the operating temperature of the distillation column bottom (1) is 50℃ to 65℃.

6. The silane purification process according to claim 3, characterized in that, In step S2, the condensate temperature of the first-stage condenser (3) is controlled at 40°C.

7. The silane purification process according to claim 3, characterized in that, In step S2, the condensate temperature of the second-stage condenser (4) is controlled at -10℃.

8. The silane purification process according to claim 3, characterized in that, In step S3, the release rate of gaseous material in the buffer evaporator (11) is controlled so that the gaseous material preheated to 48~62℃ in the tank is slowly released within 15~30 minutes; during the release process, the newly added condensate from the second stage condenser (4) enters the buffer evaporator (11) at the same time.

9. The propylene silane purification process according to claim 3, characterized in that, In step S4, the tail gas emission of silane accounts for 0.5% to 5% of the total mass of silane in the crude propane feedstock.

10. The silane purification process according to claim 3, characterized in that, In step S3, the stage switching adjustment is that the top temperature rises by ≥1°C and / or the top pressure drops by ≥15%.

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