Silane separation process

Abstract

The invention discloses a silane separation process, and relates to the technical field of chemical processing. Comprising the following steps: introducing a mixture to be separated into a condenser; collecting the high boiling point condensate in a condensate buffer; condensate rich in high-boiling-point chlorosilane in the condensate buffer is fed into a subcooler; the monosilane containing the low-boiling-point chlorosilane is distilled to separate the monosilane; extracting gas rich in silane from the upper part of the chlorosilane absorption tower; extracting pure monosilane gas from a distillation column downstream of the chlorosilane absorber; and extracting the chlorosilane condensate at the bottom of the chlorosilane absorption tower and recycling the chlorosilane condensate. Due to the fact that the liquid-phase condensate can be supercooled by the liquid-phase refrigerant, the phenomenon of heat transfer inhibition cannot occur, compared with the prior art, the size of the heat exchanger is smaller, the production and purchase cost is saved, meanwhile, the reflux condenser with the absorber is used for replacing a traditional condenser, refrigeration power consumption is reduced by 10%-60%, and the environment-friendly development concept is met.

Description

Technical Field

[0001] The present invention relates to the field of chemical processing technology, in particular to a silane separation process. Background Art

[0002] A known method for separating silane involves high-speed, continuous production of silane using trichlorosilane and dichlorosilane as raw materials. The production apparatus comprises a reaction tower and multiple upper condensers, each of which has a reflux feed line connected in series to the top of the tower, a reboiler at the bottom of the tower, and an evaporator connected to the bottom of the tower. The method involves supplying at least one of trichlorosilane and dichlorosilane to the middle stage of the tower, supplying at least one of an aliphatic hydrocarbon-substituted tertiary amine and an aliphatic hydrocarbon-substituted tertiary amine hydrochloride as a catalyst to the upper section of the tower, and introducing the resulting mixture containing silane. Monochlorosilane, dichlorosilane, and trichlorosilane are then transferred from the top of the tower to the multiple upper condensers, where the silane is separated from the condensate containing monochlorosilane, dichlorosilane, and trichlorosilane at a temperature between -50°C and 50°C. The upper condensers recover the condensate after the silane separation and feed it through a reflux feed line to the upper section of the tower, where it comes into contact with the catalyst within the tower. A tower bottom recovery liquid containing tetrachlorosilane and catalyst is extracted from the bottom of the reaction tower, introduced into an evaporation tank, and the catalyst recovered from the bottom of the evaporation tank is circulated to the reaction tower.

[0003] According to this document, the condensate at a temperature of -50°C to 50°C is refluxed to the reaction column via an upper condenser. Each condenser is connected in series to the top of the reaction column by a reflux feed line, and there are at least two upper condensers with reflux feed lines. Silane production (hourly production based on the amount of substance) depends on the number of condensers, but using too many condensers can also result in reduced silane production. Therefore, this can be a major problem in this production process.

[0004] Additionally, the temperature difference between the condensates from adjacent condensers should be adjusted based on the number of condensers. The condensate temperature of the (i+1)th upper condenser (i is an integer greater than or equal to 1) at the top of the reaction tower is T, and the condensate temperature of the (i+1)th condenser is T(i+1). The upper condenser is T1. When there are 2 to 5 upper condensers, the temperature difference should be controlled within the range of Ti - T(i+1) ≥ 10°C, with the optimal range being 15°C to 100°C, depending on the number of upper condensers.

[0005] Furthermore, when there are three or four condensers, the temperature difference should be controlled within the range of Ti - T (i+1) ≥ 15°C, with the optimal range being 20°C to 60°C. This depends on the specific number of condensers. If the temperature difference between the upper condensers is too small, the efficiency or yield of separating silane from the mixture may be reduced, or the recovery efficiency of monochlorosilane, dichlorosilane, and trichlorosilane may be reduced. Consequently, the production process parameters are very difficult to adjust, and even slight changes in conditions can easily lead to a decrease in production efficiency. In light of this, a silane separation process has been proposed. Summary of the Invention

[0006] In view of the deficiencies in the prior art, the present invention provides a silane separation process that solves the problems mentioned in the above background technology.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions: a silane separation process, the separation process comprising the following steps: Step S1, introducing the mixture to be separated into a condenser to separate the low-boiling-point chlorosilane-containing silane gas from the high-boiling-point chlorosilane-rich condensate; Step S2, collecting the high-boiling-point condensate in a condensate buffer, which is connected to the condenser described in step S1 through a condensate supply pipe; Step S3: feeding the condensate rich in high-boiling-point chlorosilanes from the condensate buffer into a subcooler, which is installed in a reflux feed line connected to the upper portion of the chlorosilane absorber. The condensate rich in high-boiling-point chlorosilanes is subcooled by a refrigerant and used as reflux for the upper portion of the chlorosilane absorber. Step S4, adding the monosilane containing the low-boiling-point chlorosilane into the chlorosilane absorption tower to separate the monosilane by distillation; Step S5, extracting silane-rich gas from the upper part of the chlorosilane absorption tower; Step S6, extracting pure monosilane gas from the distillation tower downstream of the chlorosilane absorber; Step S7: The chlorosilane condensate at the bottom of the chlorosilane absorption tower is extracted and recycled, reacting with the catalyst in the reaction tower. A bottom recovery liquid containing tetrachlorosilane and catalyst is discharged from the bottom of the reaction tower. The bottom recovery liquid is introduced into an evaporation tank, and the catalyst is recovered from the bottom of the evaporation tank and recycled to the reaction tower.

[0008] Optionally, the mixture in step S1 includes: mixtures containing monochlorosilane, dichlorosilane, trichlorosilane and tetrachlorosilane in a concentration exceeding 50 mol %; Silane with a concentration of 0.1 to 40 mol%.

[0009] Optionally, the upper portion of the absorbent body in step S3 refers to a region whose height from the bottom is higher than half of the total height of the absorbent body.

[0010] Optionally, the pure monosilane gas in step S6 is a gas having a monosilane concentration exceeding 80 mol %.

[0011] Optionally, the raw material used in the reaction in step S7 is at least one of trichlorosilane and dichlorosilane.

[0012] Optionally, the catalyst is one or more of aliphatic hydrocarbon-substituted tertiary amine and aliphatic hydrocarbon-substituted tertiary amine hydrochloride.

[0013] Optionally, the aliphatic hydrocarbon-substituted tertiary amine and the aliphatic hydrocarbon-substituted tertiary amine hydrochloride are R1R2R3N (A) and R1R2R3NH+Cl- (B), respectively.

[0014] Optionally, in R1R2R3N (A) and R1R2R3NH+Cl- (B), R1, R2 and R3 are each an aliphatic hydrocarbon group, each of which has at least 2 carbon atoms, and R1, R2 and R3 may be the same or different structures.

[0015] Optionally, in the catalyst, the content of aliphatic hydrocarbon-substituted tertiary amine should be 50 to 98 mol%, and the content of aliphatic hydrocarbon-substituted tertiary amine hydrochloride should be 2 to 50 mol%.

[0016] The present invention provides a silane separation process. It has the following beneficial effects: In this silane separation process, because the liquid condensate is supercooled by the liquid refrigerant, heat transfer inhibition does not occur. Therefore, compared with the existing technology, the size of the heat exchanger is smaller, saving production and procurement costs. At the same time, the use of a reflux condenser with an absorber instead of a traditional condenser reduces the refrigeration power consumption by 10%-60%, which is in line with the development concept of green environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the process structure of the present invention; Figure 2 Schematic diagram of the structure of the silane separation system of the present invention; DETAILED DESCRIPTION

[0018] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0019] See also Figure 1-Figure 2 The present invention provides a technical solution: a silane separation process, the process comprising the following steps: Step S1: introducing the mixture to be separated into a condenser to separate the low-boiling-point chlorosilane-containing silane gas from the high-boiling-point chlorosilane-rich condensate.

[0020] Step S2: collecting the high-boiling-point condensate in a condensate buffer, which is connected to the condenser in step S1 through a condensate supply pipe.

[0021] Step S3: The condensate rich in high-boiling-point chlorosilanes from the condensate buffer is fed into a subcooler. The subcooler is installed in a reflux feed line connected to the upper portion of the chlorosilane absorber. The condensate rich in high-boiling-point chlorosilanes is subcooled by a refrigerant and used as reflux for the upper portion of the chlorosilane absorber. The upper portion of the absorber refers to the area whose height from the bottom is higher than half of the total height of the absorber.

[0022] Step S4: adding the monosilane containing the low-boiling-point chlorosilane into the chlorosilane absorption tower to separate the monosilane by distillation.

[0023] Step S5: extracting silane-rich gas from the upper part of the chlorosilane absorption tower.

[0024] Step S6: extracting pure monosilane gas from the distillation tower downstream of the chlorosilane absorber. The pure monosilane gas is a gas with a monosilane concentration exceeding 80 mol %.

[0025] Step S7: The chlorosilane condensate at the bottom of the chlorosilane absorption tower is withdrawn and recycled. It is then contacted with the catalyst in the reaction tower for a reaction, and a bottom recovery liquid containing tetrachlorosilane and catalyst is discharged from the bottom of the reaction tower. The bottom recovery liquid is introduced into an evaporator, and the catalyst is recovered from the bottom of the evaporator and recycled to the reaction tower. The raw materials used in the reaction are at least one of trichlorosilane and dichlorosilane. The optimal molar content of dichlorosilane relative to the total amount of trichlorosilane and dichlorosilane is in the range of 5% to 55%. If the content is less than 2 mol%, the productivity of monosilane will not be improved. From an economic perspective, the amount of dichlorosilane should be no greater than 55 mol%.

[0026] The catalyst is one or more of an aliphatic hydrocarbon-substituted tertiary amine and an aliphatic hydrocarbon-substituted tertiary amine hydrochloride. The aliphatic hydrocarbon-substituted tertiary amine and the aliphatic hydrocarbon-substituted tertiary amine hydrochloride are R1R2R3N (A) and R1R2R3NH+Cl- (B), respectively. In R1R2R3N (A) and R1R2R3NH+Cl- (B), R1, R2, and R3 are each aliphatic hydrocarbon groups, and each of R1, R2, and R3 has at least 2 carbon atoms. In structural formulas (A) and (B), the aliphatic hydrocarbon group may have a carbon number ranging from 6 to 15. When the aliphatic hydrocarbon group has fewer than 2 carbon atoms, the catalyst may become solid upon contact with trichlorosilane. When the catalyst becomes solid, it may clog the reaction tower plates, packing, etc., resulting in a failure in smooth and continuous operation.

[0027] In the catalyst, the content of aliphatic hydrocarbon-substituted tertiary amine should be 50-98 mol%, and the content of aliphatic hydrocarbon-substituted tertiary amine hydrochloride should be 2-50 mol%. If the latter ratio is lower than 2 mol%, the catalytic activity is reduced; if the ratio exceeds 40 mol%, hydrochloric acid is easily released during the reaction.

[0028] The mixture in step S1 comprises: A mixture containing monochlorosilane (MCS), dichlorosilane (DCS), trichlorosilane (TCS), and tetrachlorosilane (STC) at a concentration exceeding 50 mol%. Monosilane at a concentration of 0.1 to 40 mol%.

[0029] It is worth noting that the lower-boiling-point mixed gas is a gas that does not condense at the cooling water temperature, while the higher-boiling-point mixed gas is a gas that condenses at the cooling water temperature. The refrigerant in the cooler needs to cool the condensate rich in high-boiling-point chlorosilanes to a temperature between -100°C and 20°C. This refrigerant can be lithium bromide, calcium chloride, sodium chloride, magnesium chloride, chlorofluorocarbons, ammonia, hydrocarbons, or ethylene glycol aqueous solutions. Temperatures above 20°C will reduce the efficiency of the absorption process in the chlorosilane absorption tower, while temperatures below -100°C may cause the risk of solidification of the hydrochlorosilanes.

[0030] like Figure 2 As shown, this embodiment also proposes a separation system for a silane separation process, comprising a feed pipe 4 and a reaction tower 1, wherein a mixture of trichlorosilane and dichlorosilane is supplied to the reaction tower 1 through the raw material feed pipe 4. The reaction tower 1 is a distillation tower made of stainless steel, and each tower plate is a sieve plate. A unique upper condenser 3 is provided above the reaction tower 1, which can be cooled by supplying cooling water. A bottom reboiler 2 is provided at the bottom of the reaction tower 1; and the reaction tower is used in the silane separation process to prepare silane, and the reaction tower is one of a plate tower separated by sieve plate trays, bubble cap trays, etc., or a packed tower filled with a packing material such as Raschig rings or Pall rings.

[0031] Due to the uneven temperature distribution within the reaction tower, the reaction temperature is not constant, but it is maintained within the range of 10-150°C. If the reaction temperature is below 10°C, it may be too low to fully proceed with the disproportionation reaction; if the temperature exceeds 150°C, the catalyst may thermally decompose, affecting production efficiency and production rate. Since the reaction is best carried out under boiling conditions, the gauge pressure should be controlled between 100 and 1000 kPaG to maintain the reaction temperature within this range.

[0032] The temperature at the bottom of the reaction tower is controlled by the bottom reboiler, and tetrachlorosilane that does not need to be returned to the reaction tower is selectively recovered at the bottom. Therefore, the temperature of the bottom reboiler should be maintained between 90°C and 120°C.

[0033] Furthermore, disproportionation reaction and distillation separation occur simultaneously in reaction column 1, with gases containing low-boiling-point components such as monosilane produced in the disproportionation reaction migrating upward. The resulting mixture, containing monosilane, monochlorosilane, dichlorosilane, and trichlorosilane, discharged from the top of the reaction column is supplied to an upper condenser 3 for cooling to approximately 40°C. Chlorosilane-rich silane is then separated from the chlorosilane condensate. Chlorosilane-rich monosilane is then fed via line 6 to the bottom of chlorosilane absorber 20, installed between activation distillation column 1 and pure silane distillation column 22. Silane is separated in absorber 20. Silane is separated from the chlorosilane-rich monosilane and then distilled downstream in column 22 to obtain pure silane, i.e., silane containing more than 80 mol% silane.

[0034] The chlorosilane condensate from the absorber 20 is recycled to the top of the reaction column 1 due to the line 5 at the bottom of the absorber 20 .

[0035] Absorber 20 is a device that dissolves the soluble components of a gas mixture in a liquid by bringing the gas and liquid phases into intimate contact. Absorption is typically performed in a vertical cylindrical tower or column, within which devices such as plates or packing elements are positioned. The gas and liquid typically flow in countercurrent, and these devices are used to provide contact and an interfacial surface through which mass transfer occurs.

[0036] High-boiling-point components, such as tetrachlorosilane, generated by the reaction at the top of reaction tower 1 migrate to the bottom of reaction tower 1 and are discharged from reaction tower 1 along with the catalyst. The bottom reboiler 2 leads to evaporator 12, where its liquid level is controlled. Evaporator 12 can be a stainless steel vessel equipped with a stirrer and fitted with a jacket. A heating medium circulates within the jacket, heating evaporator 12. The operating temperature of evaporator 12 is above the boiling point of tetrachlorosilane generated by the disproportionation reaction but below that of the catalyst. Tetrachlorosilane and other components evaporate and are collected in lower condenser 13, cooled with cooling water, and recovered in collection tank 14. Residual catalyst in evaporator 12 is pumped out by pump 11 and circulated to the upper section of the reaction tower. Hydrogen chloride is supplied via piping 24. At this time, if the concentration of the aliphatic tertiary-substituted amine hydrochloride in the catalyst falls below a specified concentration, hydrogen chloride is supplied from supply pipe 15 as needed.

[0037] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A silane separation process, characterized in that: The separation process comprises the following steps: Step S1, introducing the mixture to be separated into a condenser to separate the low-boiling-point chlorosilane-containing silane gas from the high-boiling-point chlorosilane-rich condensate; Step S2, collecting the high-boiling-point condensate in a condensate buffer, which is connected to the condenser described in step S1 through a condensate supply pipe; Step S3: feeding the condensate rich in high-boiling-point chlorosilanes from the condensate buffer into a subcooler, which is installed in a reflux feed line connected to the upper portion of the chlorosilane absorber. The condensate rich in high-boiling-point chlorosilanes is subcooled by a refrigerant and used as reflux for the upper portion of the chlorosilane absorber. Step S4, adding the monosilane containing the low-boiling-point chlorosilane into the chlorosilane absorption tower to separate the monosilane by distillation; Step S5, extracting silane-rich gas from the upper part of the chlorosilane absorption tower; Step S6, extracting pure monosilane gas from the distillation tower downstream of the chlorosilane absorber; Step S7: extracting and recycling the chlorosilane condensate at the bottom of the chlorosilane absorption tower, contacting the condensate with the catalyst in the reaction tower for reaction, and discharging a bottom recovery liquid containing tetrachlorosilane and the catalyst from the bottom of the reaction tower. After the bottom recovery liquid is introduced into an evaporation tank, the catalyst is recovered from the bottom of the evaporation tank and recycled to the reaction tower.

2. A silane separation process according to claim 1, characterized in that: The mixture in step S1 comprises: mixtures containing monochlorosilane, dichlorosilane, trichlorosilane and tetrachlorosilane in a concentration exceeding 50 mol %; Silane with a concentration of 0.1 to 40 mol%.

3. A silane separation process according to claim 1, characterized in that: In step S3, the upper portion of the absorbent body refers to a region whose height from the bottom is higher than half of the total height of the absorbent body.

4. A silane separation process according to claim 1, characterized in that: The pure monosilane gas in step S6 is a gas having a monosilane concentration exceeding 80 mol %.

5. A silane separation process according to claim 1, characterized in that: The raw material used in the reaction in step S7 is at least one of trichlorosilane and dichlorosilane.

6. A silane separation process according to claim 5, characterized in that: The catalyst is one or more of aliphatic hydrocarbon-substituted tertiary amine and aliphatic hydrocarbon-substituted tertiary amine hydrochloride.

7. A silane separation process according to claim 6, characterized in that: The aliphatic hydrocarbon-substituted tertiary amine and the aliphatic hydrocarbon-substituted tertiary amine hydrochloride are R1R2R3N (A) and R1R2R3NH+Cl- (B), respectively.

8. A silane separation process according to claim 7, characterized in that: In the R1R2R3N (A) and R1R2R3NH+Cl- (B), R1, R2 and R3 are each an aliphatic hydrocarbon group, and each of R1, R2 and R3 has at least 2 carbon atoms.

9. A silane separation process according to claim 8, characterized in that: In the catalyst, the content of aliphatic hydrocarbon-substituted tertiary amine should be 50-98 mol%, and the content of aliphatic hydrocarbon-substituted tertiary amine hydrochloride should be 2-50 mol%.

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