An apparatus and method for preparing electronic-grade silanes by catalytic reactive distillation.

Abstract

This invention relates to an apparatus and method for preparing electronic-grade silane by catalytic reactive distillation. Chlorosilane is used as the raw material, which is removed by an adsorber (1) and then enters a silane reactive distillation column (2). The crude silane at the top of the column enters a primary cryogenic reactor (3) and a secondary cryogenic reactor (4) for coarse separation. The crude silane then enters a silane separation column (4) where electronic-grade silane is collected via a side stream. The adsorbent in the adsorber (1) controls the content of boron, phosphorus, total metals, and hydrogen chloride impurities in the chlorosilane raw material. The silane reactive distillation column (2) has multiple feed inlets, optimizing the concentration distribution of the material in the reaction section, which is beneficial for the disproportionation reaction. The silane separation column (4) uses a side-collection method from the upper liquid phase and the part in contact with the material is polished, allowing direct acquisition of electronic-grade products. This invention features high catalytic distillation efficiency, a short process flow, and a long service life of the catalytic packing.

Description

Technical Field

[0001] This invention belongs to the field of chemical synthesis technology, and specifically relates to an apparatus and method for producing electronic-grade silanes from trichlorosilane via catalytic reactive distillation. Background Technology

[0002] Silane, also known as silane, has the molecular formula SiH4. It is a colorless gas that reacts violently with oxygen across a wide temperature range and is unstable, rapidly decomposing into silicon and hydrogen at 600℃. Despite its reactive chemical properties, silane is one of the most widely used and influential electronic specialty gases. Silane can be used to prepare polycrystalline silicon. Polycrystalline silicon prepared by the silane method has advantages such as high purity, low boron and phosphorus content, and the process is simple, produces no corrosive gases, results in minimal equipment corrosion, and has low production costs. In the semiconductor microelectronics industry, silane can be used to prepare various microelectronic thin films, such as microcrystals, silicon oxide, single-crystal films, and metal silicides. It can also be used in the fabrication of semiconductor devices (silicon carbide, gallium arsenide, etc.) and quantum well materials. Due to the high purity and finely tunable nature of silane-based metal silicides, it has become an important electronic specialty gas that cannot be replaced by many other silicon sources.

[0003] There are many methods for preparing SiH4, such as the silicon alloy method, the hydride reduction method, the direct hydrogenation synthesis of silicon, and the chlorosilane disproportionation method. The chlorosilane disproportionation method uses trichlorosilane (SiCl3) as a raw material to obtain SiH4 through disproportionation, while simultaneously producing silicon tetrachloride (SiCl4) as a byproduct. Because SiCl4 can be converted back to SiCl3 after hydrogenation and used as a raw material, the entire process is simple, generates no waste, and is considered a green process, making it the mainstream process for silane preparation.

[0004] The trichlorosilane disproportionation reaction is a cascade reversible reaction, producing dichlorosilane (SiH2Cl2) and monochlorotrichlorosilane (SiH3Cl) intermediates in addition to SiH4 and SiCl4. Patent US4340574 describes a process for continuous silane production using chlorosilanes as raw materials and a fixed-bed adsorption process, separating and purifying the disproportionation products through distillation to obtain the silane product. To overcome the limitations of reversible reaction equilibrium and improve the conversion rate of the disproportionation reaction, patent US6905576 first proposed a process for continuous silane production using reactive distillation technology. The material collected from the reactive distillation column is then purified by a silane separation column to obtain the silane product. Patent CN103172071, based on the characteristics of the components in the disproportionation reactants, uses SiCl4 as the absorbent solvent, supplemented by a fixed-bed adsorption process, to purify the material collected from the top of the reactive distillation column to obtain the silane product. Patent CN103241743 discloses a process for the continuous production of silanes via reactive distillation. This process involves adding raw material purification and product separation equipment before and after the silane reactive distillation column to ensure the purity of the silane product and the silicon tetrachloride byproduct. Because SiH4, SiH2Cl2, and SiH3Cl have low boiling points, their liquefaction requires high-quality refrigerant and consumes a lot of energy. Patents CN106241813 and CN115321540 utilize the significant boiling point difference between silane and other components in the reaction system. They employ multi-stage condensers and use refrigerants of different temperatures and grades to achieve multi-stage partial condensation of the vapor phase at the top of the reactive distillation column, reducing the cryogenic load and effectively decreasing operating costs and energy consumption.

[0005] The core of catalytic reactive distillation design is ensuring the matching of the reaction and distillation processes. If the catalytic reaction efficiency decreases, the single-pass conversion rate decreases, the amount of unreacted products increases, the circulation flow rate within the reactive distillation system increases, and the system's energy consumption increases accordingly. The catalytic reaction efficiency in the reaction section is related to the concentration distribution and catalyst activity within the reaction section. However, in the process research for catalytic reactive distillation to prepare silanes, these core issues have not yet received sufficient attention, resulting in short catalyst lifespan and low single-pass conversion rates in the reactive distillation column. Furthermore, in the wet processes of the electronics industry, electronic chemicals are key materials, and controlling their metal ion content is crucial to ensuring product yield. Current silane preparation technologies fail to control metal ion content at the source, requiring subsequent purification units to obtain electronic-grade products. This undoubtedly prolongs the process and increases production costs. Summary of the Invention

[0006] This invention addresses the problems existing in the prior art. Specifically, the technical problem to be solved by this invention is an apparatus and method for preparing electronic-grade silanes by catalytic reactive distillation. By optimizing the process and equipment, the service life of the catalytic packing is extended, the efficiency of catalytic distillation is improved, the metal ion content is controlled from the source, and the preparation process of electronic-grade silanes is shortened.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] Trichlorosilane, as a raw material, first enters a fixed-bed adsorption column (1) for adsorption and impurity removal, removing boron, phosphorus, metals, and hydrogen chloride impurities from the raw material. Then, it is fed into the lower part of the reaction section A feed port of the silane reactive distillation column (2). The bottom of the silane reactive distillation column (2) is equipped with a reboiler, and the top is equipped with a condenser. The reactive distillation column is equipped with a rectification section, a reaction section, and a stripping section from top to bottom. The reaction section is filled with catalytic packing. SiHCl3 undergoes the following three-step disproportionation reaction in the reaction section:

[0009] 2SiHCl3=SiH2Cl2+SiCl4

[0010] 2SiH2Cl2=SiH3Cl+SiHCl3

[0011] 2SiH3Cl=SiH4+SiH2Cl2

[0012] The vapor at the top of the reactive distillation column is partially condensed in the condenser. Part of the condensate is returned to the column as reflux, and part is sent to feed inlet A in the middle and lower part of the reaction section. The mixed gas of SiH4, SiH3Cl, SiH2Cl2, and SiHCl3 from the top condenser is sequentially sent to the primary cryocooler (3) and the secondary cryocooler (4), and SiCl4 is collected from the bottom of the column. The condensate collected from the primary cryocooler (3) has a temperature range of -15 to 25°C, and the condensate collected from the secondary cryocooler (4) has a temperature range of -40 to -15°C. These condensates are returned to different feed inlets in the upper part of the reaction section of the silane reactive distillation column (2), respectively. The gaseous material collected from the secondary cryogenic reactor (4) is pressurized by the compression system (5) and sent to the silane separation tower (6). The silane separation tower (6) is equipped with a reboiler and a condenser. After the vapor-liquid mass transfer in the distillation tower, the low-boiling-point light component is collected from the top of the tower, the electronic-grade silane product is collected from the upper side stream, and the chlorosilane component is collected from the bottom of the tower and returned to the upper B feed port in the reaction section of the silane reactive distillation tower (2).

[0013] Furthermore, the fixed-bed adsorption column (1) is filled with one or more of the following adsorbents: resin, activated carbon, molecular sieve, and activated alumina;

[0014] Furthermore, after passing through the fixed-bed adsorption column (1), the content of boron impurities in trichlorosilane is no higher than 100 ppb, the content of phosphorus impurities is no higher than 50 ppb, the content of total metal impurities is no higher than 100 ppb, and the content of hydrogen chloride impurities is no higher than 10 ppm. Reducing the content of these impurities in the raw material significantly reduces the occupancy rate of impurities on the active groups of the catalytic packing, effectively extending the service life of the catalytic packing.

[0015] Furthermore, the boron impurities are a general term for boron hydrides, boron chlorides and other boron-containing compounds, and the boron impurity content after adsorption is not higher than 100 ppb, preferably not higher than 10 ppb;

[0016] Furthermore, the phosphorus impurities are a general term for phosphate compounds, phosphorus chloride compounds and other phosphorus-containing compounds, and the phosphorus impurity content after adsorption is not higher than 50 ppb, preferably not higher than 5 ppb.

[0017] Furthermore, the total metal impurities are a collective term for iron, aluminum, calcium, magnesium, manganese, etc., and the total metal impurity content after adsorption is not higher than 100 ppb, preferably not higher than 10 ppb.

[0018] Furthermore, the hydrogen chloride impurity refers to the hydrogen chloride component, and the content of hydrogen chloride impurity after adsorption is not higher than 10 ppm, preferably not higher than 1 ppm.

[0019] Furthermore, the silane reactive distillation column is provided from bottom to top with a stripping section of 10 to 50 theoretical plates, a reaction section of 4 sections packed with catalytic packing, and a rectification section of 4 to 20 theoretical plates. Each section of catalytic packing is 2 to 6 meters high, and there are three feed inlets, A, B, and C, between the catalytic packing sections from bottom to top.

[0020] Furthermore, a portion of the condensate from the top condenser of the silane reactive distillation column is returned to the column via the reflux port, with the ratio of reflux to total condensate being 0.5–0.95. The remaining portion is sent to feed inlet A in the upper part of the reaction section.

[0021] Furthermore, the gaseous material exiting the top condenser of the silane reactive distillation column first passes through a primary cryocooler and then is sent to a secondary cryocooler. The liquid condensate from the primary cryocooler returns to the reactive distillation column from port C, and the liquid condensate from the secondary cryocooler returns to the reactive distillation column from port B to continue the disproportionation reaction, thereby improving the conversion rate of the reaction.

[0022] Furthermore, the silane separation tower is equipped with a side sampling port above the feed inlet, employing a liquid-phase side sampling method to achieve the separation of light and heavy components. The light components are collected from the top of the tower and discharged, while the heavy components are collected from the bottom of the tower and sent to the B feed inlet of the reactive distillation tower.

[0023] Furthermore, the parts above the side inlet of the silane separation tower that come into contact with the material (including the inner wall of the tower, the internal components of the tower, the inner wall of the gas phase pipe at the top of the tower, the material side of the condenser at the top of the tower, the inner wall of the reflux tank, the inner wall of the reflux pipe and corresponding accessories) are all polished.

[0024] Furthermore, the polishing process includes manual polishing, mechanical polishing, chemical polishing, electrolytic polishing, and plasma polishing. The surface roughness after polishing is required to be no greater than 1 μm, preferably no greater than 0.4 μm.

[0025] Compared with the prior art, the present invention has the following effects:

[0026] (1) The raw material trichlorosilane is purified by fixed bed adsorption, which reduces the impurity content in the raw material, reduces the occupancy rate of active groups in the catalytic packing, and significantly extends the service life of the catalytic packing.

[0027] (2) The condensate from the top condenser, the first-stage cryocooler and the second-stage cryocooler of the reactive distillation column, as well as the bottom liquid of the silane separation column, are returned to different feed inlets of the silane reactive distillation column. This optimizes the concentration distribution of the material in the reaction section, which is beneficial to the disproportionation reaction and can increase the single-pass conversion rate by 8-15%.

[0028] (3) The raw material trichlorosilane is pretreated by fixed bed adsorption to control the metal content from the source. Electronic grade silane products can be obtained without subsequent purification units, which shortens the process flow.

[0029] (4) All equipment surfaces that come into contact with silane are polished, which can greatly reduce the impact of external equipment factors on electronic grade silane products and ensure that the metal impurity content of silane products does not exceed the standard. Attached Figure Description

[0030] Figure 1 A process flow diagram for the preparation of electronic-grade silanes by catalytic reactive distillation;

[0031] Among them, 1 is a fixed-bed adsorption column, 2 is a silane reactive distillation column, 3 is a primary cryogenic reactor, 4 is a secondary cryogenic reactor, 5 is a compression system, and 6 is a silane separation column. Detailed Implementation

[0032] To make the above features and advantages of the present invention more apparent and understandable, specific embodiments are described below in conjunction with the accompanying drawings. Figure 1 The following is a detailed explanation.

[0033] like Figure 1 The process flow for preparing electronic-grade silane by catalytic reactive distillation includes a fixed-bed adsorption column 1, a silane reactive distillation column 2, a primary cryogenic cooler 3, a secondary cryogenic cooler 4, a compression system 5, a silane separation column 6, and auxiliary equipment for the distillation column (reboiler and condenser). The specific process flow is as follows.

[0034] Trichlorosilane feedstock first enters a fixed-bed adsorption column 1 for adsorption and impurity removal, eliminating impurities such as boron, phosphorus, metals, and hydrogen chloride. It is then fed into the feed inlet A of a silane reactive distillation column 2. The silane reactive distillation column 2 is equipped with a reboiler at the bottom and a condenser at the top. From top to bottom, the column consists of a rectification section, a reaction section, and a stripping section. The reaction section is packed with catalytic packing. Trichlorosilane undergoes a three-step disproportionation reaction within the silane reactive distillation column 2.

[0035] The overhead vapor in the reactive distillation column is partially condensed in the condenser. Part of the condensate is returned to the column as reflux, and the remainder is sent to feed inlet A in the lower middle section of the reaction section. The mixture of SiH4, SiH3Cl, SiH2Cl2, and SiHCl3 from the overhead condenser is sequentially fed into the primary cryocooler 3 and the secondary cryocooler 4. Silicon tetrachloride is collected from the bottom of the column. The condensate from the primary cryocooler 3 is returned to feed inlet C of the silane reactive distillation column, and the condensate from the secondary cryocooler 4 is returned to feed inlet B of the silane reactive distillation column.

[0036] The gaseous material collected from the secondary cryogenic reactor 4 is pressurized by the compression system 5 and sent to the silane separation tower 6. The silane separation tower 6 is equipped with a reboiler and a condenser. After vapor-liquid mass transfer in the distillation tower, the low-boiling-point light component is collected from the top of the tower, the electronic-grade silane product is collected from the upper side stream, and the chlorosilane component is collected from the bottom of the tower and returned to the B feed port of the silane reactive distillation tower 2.

[0037] Example 1:

[0038] The trichlorosilane raw material came from the trichlorosilane synthesis unit. ICP-MS analysis showed that the boron impurity content was 315 ppb, the phosphorus impurity content was 193 ppb, and the total metal impurity content was 1398 ppb. GC analysis showed that the hydrogen chloride content was 83 ppm.

[0039] A 500 kg / h trichlorosilane flow rate was continuously fed into a fixed-bed adsorption column (Ф400 mm × 4000 mm), with an effective volume of 525 L. The column consisted of four adsorption beds: the first stage was packed with 80 L of chelating resin; the second stage with 100 L of modified activated carbon; the third stage with 80 L of ion exchange resin; and the fourth stage with 100 L of activated carbon. After stabilization, samples were analyzed using ICP-MS. The results showed boron impurities at 48 ppb, phosphorus impurities at 17 ppb, and total metal impurities at 87 ppb. GC analysis showed that hydrogen chloride was not detected.

[0040] The silane reactive distillation column has a diameter of 500 mm, with 15 theoretical plates in the rectification section and 20 theoretical plates in the stripping section. It is filled with 22m thick catalytic packing in bundles, with each section of packing having a height of 5m, 5m, 6m, and 6m from top to bottom, totaling 4.32m. 3 Inlet A is located between the third and fourth sections of the catalytic packing from top to bottom, inlet B is located between the second and third sections of the catalytic packing from top to bottom, and inlet C is located between the first and second sections of the catalytic packing from top to bottom.

[0041] The silane separation column has a diameter of 200 mm and is equipped with 30 theoretical plates in the rectification section and 30 theoretical plates in the stripping section. The side feed port is located in the middle of the rectification section. A vertical fixed tube sheet condenser is directly connected to the top of the column, using -45℃ Freon as the cold source. The inner walls of the rectification column above the feed port, the cross-flow sieve trays, the inner walls of the tubes in contact with the material in the condenser, the side feed line, and the inner walls of the silane product receiving tank are polished to a roughness of 0.4 μm.

[0042] After the silane reactive distillation column and the silane separation column were operating stably, the non-condensable steam flow rate of the condenser at the top of the silane reactive distillation column was 123.3 kg / h, of which the trichlorosilane content was 23.3 wt%. Based on this, the single-pass conversion rate of the silane reactive distillation column was calculated to be 94.5%.

[0043] Table 1. Material Information for Main Streams in Example 1 (Part 1)

[0044]

[0045] Table 2. Material information for the main flow streams in Example 1 (Part 2)

[0046]

[0047]

[0048] The upper side stream of the silane separation tower yielded 29.31 kg / h of electronic-grade silane product. After 360 hours of stable operation, samples were taken and analyzed using ICP-MS. The total metal impurity content in the silane product was 0.163 ppb.

[0049] After 100 days of continuous operation, the average output of electronic-grade silane decreased from the initial 29.31 kg / h to 28.82 kg / h, a decrease of 0.49 kg / h in absolute terms. When the output dropped to 70% of the design value, the catalyst packing was considered to need replacement, and the catalyst's lifespan was calculated to be 4.9 years.

[0050] Example 2:

[0051] The trichlorosilane feedstock was obtained from the trichlorosilane crude distillation unit. ICP-MS analysis showed that the boron impurity content was 43 ppb, the phosphorus impurity content was 38 ppb, and the total metal impurity content was 219 ppb. GC analysis showed that the hydrogen chloride content was 0.0036%.

[0052] 400 kg / h of trichlorosilane was continuously fed into a fixed-bed adsorption column (400 mm × 4000 mm, effective volume 525 L). The fixed-bed adsorption column used a mixed packing scheme, consisting of 200 L of resin, 100 L of activated carbon, and 160 L of activated alumina. After stabilization, samples were taken and analyzed using ICP-MS. The effluent contained 22 ppb of boron impurities, 35 ppb of phosphorus impurities, and 69 ppb of total metal impurities. GC analysis showed that the hydrogen chloride content was 0.0005%.

[0053] The silane reactive distillation column has a diameter of 500 mm and is filled with 18 m of structured catalytic packing. The heights of each section of the catalytic packing from top to bottom are 3 m, 5 m, 5 m, and 5 m, respectively, totaling 3.54 m. 3 The feed inlets ABC are configured the same as in Example 1.

[0054] The silane separation column has a diameter of 200 mm and is equipped with 30 theoretical plates in the rectification section and 30 theoretical plates in the stripping section. The side sampling port is located in the middle of the rectification section. A vertical fixed tube sheet condenser is directly connected to the top of the column, using -45℃ Freon as the cold source. The inner wall of the rectification column above the feed port, the cross-flow sieve trays, the inner wall of the tubes in contact with the material in the condenser, the side sampling pipeline, and the inner wall of the silane product receiving tank are polished to a roughness of 0.25 μm.

[0055] After the silane reactive distillation column and the silane separation column were operating stably, the non-condensable steam flow rate of the condenser at the top of the silane reactive distillation column was 123.9 kg / h, of which the trichlorosilane content was 13.7 wt%. Based on this, the single-pass conversion rate of the silane reactive distillation column was calculated to be 95.8%.

[0056] Table 3. Material Information for Main Streams in Example 2 (Part 1)

[0057]

[0058] Table 4. Material Information for Main Flow Streams in Example 2 (Part Two)

[0059]

[0060] The upper side stream of the silane separation tower yielded 23.45 kg / h of electronic-grade silane product. After 360 hours of stable operation, samples were taken and analyzed using ICP-MS. The total metal impurity content in the silane product was 0.135 ppb.

[0061] After 100 days of continuous operation, the average output of electronic-grade silane decreased from the initial 23.45 kg / h to 23.08 kg / h, a decrease of 0.37 kg / h in absolute terms. When the output dropped to 70% of the design value, the catalyst packing was considered to need replacement, and the catalyst's lifespan was calculated to be 5.2 years.

[0062] The apparatus and method for preparing electronic-grade silanes by catalytic reactive distillation proposed in this invention have been described through examples. Those skilled in the art will readily be able to modify or appropriately alter and combine the systems and methods described herein without departing from the content, spirit, and scope of this invention to achieve the technical requirements of this invention. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the spirit, scope, and content of this invention.

Claims

1. A method for preparing electronic-grade silane by catalytic reactive distillation, characterized in that, Includes the following steps: (1) The raw material trichlorosilane is fed from the bottom of the fixed bed adsorption column and then discharged from the top; the fixed bed adsorption column is filled with adsorbent to remove impurities such as boron, phosphorus, metal and hydrogen chloride from the raw material; (2) The material from the outlet of the fixed bed adsorption column is sent to the middle feed port of the silane reactive distillation column. Trichlorosilane undergoes a series of disproportionation reactions under the action of the catalyst to generate dichlorosilane, monochlorotrichlorosilane, silicon tetrachloride and silane. The material collected from the top of the reactive distillation column is sent to the top reflux port as reflux liquid after passing through the top part of the condenser, and part of it is sent to the middle feed port. The gaseous material from the top condenser is sent to the subsequent first-stage cryocooler, and silicon tetrachloride is extracted from the bottom of the column. (3) The uncondensed gaseous material at the top of the silane reactive distillation column is further condensed in the first-stage cryocooler, and the gaseous material from the first-stage cryocooler is sent to the second-stage cryocooler for further condensation; the liquid material from the first-stage cryocooler and the second-stage cryocooler is returned to the corresponding feed inlet of the silane reactive distillation column respectively. (4) The gaseous material from the secondary cryogenic reactor is first compressed and pressurized before being sent to the silane separation tower; the light component is collected from the top of the silane separation tower, the electronic grade silane product is collected from the middle and upper side of the tower, and the material collected from the bottom of the tower is returned to the silane reactive distillation tower. The catalytic packing section of the silane reactive distillation column has three feed ports from bottom to top: feed port A, feed port B, and feed port C. Material from the fixed bed adsorption column is fed through feed port A. In step (2), a portion of the liquid material in the top condenser of the reactive distillation column is returned to the column from the reflux port, with the ratio of reflux liquid to total condensate being 0.5 to 0.95, and a portion is returned to the column from feed port A. The liquid material in the first-stage cryogenic reactor is fed through inlet C, and the liquid material in the second-stage cryogenic reactor is fed through inlet B; the material collected from the bottom of the silane separation tower is returned to inlet B of the reactive distillation tower.

2. The method according to claim 1, characterized in that, The adsorbent in step (1) is one or a combination of resin, activated carbon, molecular sieve, and activated alumina.

3. The method according to claim 1, characterized in that, The silane reactive distillation column in step (2) is provided with a stripping section of 10 to 50 theoretical plates, a reaction section of 4 sections filled with catalytic packing, and a rectification section of 4 to 20 theoretical plates from bottom to top. Each section of catalytic packing is 2 to 6 meters high.

4. The method according to claim 1, characterized in that, The silane separation tower has a side inlet above the feed inlet, and the part above the side inlet that comes into contact with the material is polished. The part above the side inlet that comes into contact with the material includes the inner wall of the tower, the internal components of the tower, the inner wall of the gas phase pipe at the top of the tower, the material side of the condenser at the top of the tower, the reflux tank, the inner wall of the reflux pipe, and corresponding accessories.

5. The method according to claim 4, characterized in that, The polishing process includes one or more of the following: manual polishing, mechanical polishing, chemical polishing, electrolytic polishing, and plasma polishing. The roughness of the polishing process is required to be no greater than 1 μm.

Images