Process and equipment for preparing silane by coupling reactive distillation and fixed bed

Abstract

The invention relates to a process and equipment for preparing silane by coupling reactive distillation and a fixed bed, which comprises the following steps: arranging a reactive distillation tower which is internally filled with a separation internal part and a catalysis internal part to realize a reactive distillation process; a fixed bed reactor is arranged and is filled with a catalyst and a filtering internal part; the bottom of the reactive distillation tower is connected with a reactive distillation tower reboiler, a liquid phase at the bottom of the reactive distillation tower enters the reactive distillation tower reboiler, and a gas-liquid mixed phase gasified by the reactive distillation tower reboiler returns to the bottom of the reactive distillation tower; the top of the reactive distillation column is connected with a reactive distillation column water cooler; a gas phase of the reactive distillation tower water cooler is connected with the fixed bed reactor, non-condensed steam of the reactive distillation tower water cooler enters the fixed bed reactor and reacts in the fixed bed reactor to reach component balance, and a reaction product enters a rear-end component separation device. The fixed bed reactor is arranged at the specific position in the reactive distillation system, coupling of reactive distillation and a fixed bed is achieved, the one-way yield of silane can be increased, and the production efficiency of silane is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of silane preparation, and in particular to a process and equipment for preparing silane by coupling reactive distillation with a fixed bed. Background Art

[0002] Silane is primarily produced through the chlorosilane disproportionation process: trichlorosilane is used as the raw material, undergoing a three-step disproportionation reaction. The first step, using trichlorosilane as the reactant, produces dichlorosilane and silicon tetrachloride. The second step, using dichlorosilane as the reactant, produces monochlorotrihydrogensilane and trichlorosilane. The third step, using monochlorotrihydrogensilane as the reactant, produces silane and dichlorosilane. These three-step disproportionation reactions can be achieved primarily through fixed-bed processes and reactive distillation, with reactive distillation being more energy-efficient.

[0003] Patent publication CN103172071A describes using trichlorosilane as a raw material, obtaining silane and dichlorosilane at the top of the tower through reactive distillation, obtaining silicon tetrachloride at the bottom of the tower, and obtaining the silane product after the mixed gas at the top of the tower is absorbed by silicon tetrachloride and adsorbed on a fixed bed; Patent publication CN103241743A describes using high-purity trichlorosilane as a raw material, extracting the reaction product from the gas phase at the top of the disproportionate reaction distillation tower, and using the pressure difference to enter the silane tower, obtaining the liquid silane product after separation, and separating the mixed chlorosilane at the bottom of the tower to obtain trichlorosilane and return it to the reactive distillation tower, while the silicon tetrachloride is discharged; Patent CN103979544A describes a disproportionation reaction catalyzed by a liquid catalyst mixed with aliphatic amines and aromatic amines, which is carried out in a reactive distillation tower. Patent CN106241813A describes a reaction tower in which the upper outlet enters a multi-stage condenser, and the non-condensable gas is compressed and separated to obtain a silane product, and a silicon tetrachloride product is obtained at the bottom. Patent CN115321540A describes a process in which trichlorosilane is used as a raw material and reactive distillation technology is utilized to prepare high-purity silane through disproportionation reaction distillation, multi-stage condensation separation, pressure increase of a crude silane pump, and distillation separation and purification.

[0004] Although the reactive distillation process for preparing silanes has been put into industrial application, some problems remain. The original process used separate fixed-bed and distillation towers, lacking a combination of innovative technologies. Trichlorosilane reacts in fixed-bed one to produce dichlorosilane and tetrachlorosilane, which then enter distillation tower one for separation. Dichlorosilane is produced from the top of the tower, and tetrachlorosilane is produced from the bottom. Dichlorosilane, produced from the top of distillation tower one, is then fed into fixed-bed two for a reaction, producing silane, monochlorosilane, dichlorosilane, trichlorosilane, and silicon tetrachloride. These react in distillation tower two for separation, with the light component silane produced from the top and the heavy components (monochlorosilane, dichlorosilane, trichlorosilane, and silicon tetrachloride) produced from the bottom. These reactants are then returned to distillation tower one for separation, continuing the reaction cycle.

[0005] The current problem is that a large amount of chlorosilane generated in a single pass during the reaction does not participate in the reaction, the single-pass conversion rate is low, the separation effect is poor, and continuous separation and repeated reactions are required. The circulation flow is large and the equipment reaction energy consumption is high. This is a technical problem that needs to be urgently solved in reactive distillation. Summary of the Invention

[0006] To address the technical problems existing in the above-mentioned background technology, the present invention provides a process and apparatus for preparing silane by coupling reactive distillation with a fixed bed. By disposing a fixed bed reactor at a location in the reactive distillation system where the content of monochlorotrihydrogen silicon and dichlorodihydrogen silicon is relatively high and the content of trichlorosilane and silicon tetrachloride is relatively low, i.e., after the water cooler of the reactive distillation tower, the reactive distillation and fixed bed are coupled to achieve the effect of increasing the single-pass yield of silane by 5-10%, reducing the amount of chlorosilane separation and circulation, and improving the efficiency of silane production.

[0007] The technical solutions of the present invention are as follows: A process for preparing silane by coupling reactive distillation with a fixed bed comprises: A reactive distillation column is provided, wherein separation internals and catalytic internals are loaded inside the column to realize the reactive distillation process; A fixed bed reactor is provided, wherein the catalyst and filter internals are filled therein to realize the fixed bed reaction process; The bottom of the reaction distillation tower is connected to the reaction distillation tower reboiler, the liquid phase at the bottom of the reaction distillation tower enters the reaction distillation tower reboiler, and the gas-liquid mixed phase vaporized in the reaction distillation tower reboiler returns to the bottom of the reaction distillation tower; the top of the reaction distillation tower is connected to the reaction distillation tower water cooler, the gas phase at the top of the reaction distillation tower enters the reaction distillation tower water cooler, and the condensate of the reaction distillation tower water cooler returns to the top of the reaction distillation tower; The gas phase of the reaction distillation tower water cooler is connected to the fixed bed reactor. The non-condensable steam of the reaction distillation tower water cooler enters the fixed bed reactor. The reaction reaches component equilibrium in the fixed bed reactor, and the reaction products enter the back-end component separation device.

[0008] Preferably, the catalytic internals filled in the reactive distillation tower are catalysts, and the catalysts are molecular sieves, alumina, resin particles or activated carbon.

[0009] Preferably, the separation internals of the reactive distillation tower are structured packing, random packing or trays.

[0010] Furthermore, the catalyst inside the fixed bed reactor is molecular sieve, alumina, resin particles or activated carbon.

[0011] Furthermore, the filtering internals of the fixed bed reactor are water caps, wire meshes or grids.

[0012] Furthermore, the feed rate of the reactive distillation column feed stream is 100 kg / h-10 t / h.

[0013] Furthermore, the operating pressure of the reactive distillation tower is 2.5 barg-3.5 barg, and the water cooling temperature is 35°C-45°C.

[0014] A device for preparing silane by coupling reactive distillation and fixed bed, used for implementing a process for preparing silane by coupling reactive distillation and fixed bed, comprising: A reactive distillation tower, the interior of which is filled with separation internals and catalytic internals; A fixed bed reactor, which is filled with catalyst and filter internals; The reaction distillation tower has a feed inlet, a first return inlet, a second return inlet, and a second outlet and a first outlet arranged at the upper and lower ends thereof, the first outlet being connected to a reaction distillation tower reboiler, the gas-liquid mixed phase outlet of the reaction distillation tower reboiler being connected to the first return inlet; the second outlet being connected to a reaction distillation tower water cooler, the condensate outlet of the reaction distillation tower water cooler being connected to the second return inlet via a pipeline; The gas phase outlet of the water cooler of the reaction distillation tower is connected to the inlet of the fixed bed reactor, and the outlet of the fixed bed reactor is connected to the rear-end component separation device.

[0015] Preferably, the reactive distillation tower is provided with a plurality of packing separation layers spaced apart from each other from top to bottom, and a corresponding reaction section is installed above each separation packing layer.

[0016] Furthermore, the number of packing separation layers is 5-9. Accurate calculations are performed based on reaction principles, energy conservation, material balance and other data to design the specifications of the tower body (height, diameter, etc.), and at the same time calculate the required reaction sections and separation layer specifications.

[0017] The beneficial effects of the present invention are: The existing process is that the fixed bed and the distillation tower exist separately. This technical invention is to install the fixed bed inside the distillation tower, making technical innovation, integrating reaction and distillation, and performing them simultaneously; By setting a fixed-bed reactor at a specific location in the reactive distillation system to achieve coupling between reactive distillation and the fixed bed, the single-pass yield of silane can be increased by 5-10%, the amount of chlorosilane separation circulation can be reduced, and the silane production efficiency can be improved; The reaction distillation tower is a combination of multiple stages of reaction distillation, which reacts and distills at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In the attached figure: Figure 1 Schematic diagram of the process flow; The components represented by the reference numerals in the figure are: T01, reaction distillation tower; E01, reaction distillation tower reboiler; E02, reaction distillation tower water cooler; R01, fixed bed reactor; s01, reaction distillation tower feed logistics; s02, reaction distillation tower overhead gas logistics; s03, reaction distillation tower bottom liquid logistics; s04, fixed bed reactor outlet logistics. DETAILED DESCRIPTION

[0019] Example 1 See also Figure 1 As shown, a process for preparing silane by coupling reactive distillation with a fixed bed comprises: A reactive distillation tower T01 is provided, which is filled with separation internals and catalytic internals for implementing a reactive distillation process; the catalytic internals in this embodiment are catalysts, which are molecular sieves, alumina, resin particles, or activated carbon, and the separation internals in the reactive distillation tower T01 are structured packing, random packing, or trays; A fixed bed reactor R01 is provided, and a catalyst and filter internals are loaded therein to realize a fixed bed reaction process; the catalyst inside the fixed bed reactor R01 is a molecular sieve, alumina, resin particles or activated carbon; and the filter internals are a water cap, a wire mesh or a grid.

[0020] The bottom of the reaction distillation tower T01 is connected to the reaction distillation tower reboiler E01, the liquid phase at the bottom of the reaction distillation tower T01 enters the reaction distillation tower reboiler E01, the reaction distillation tower feed flow enters from the feed port, and the gas-liquid mixed phase vaporized in the reaction distillation tower reboiler E01 returns to the bottom of the reaction distillation tower T01; the top of the reaction distillation tower T01 is connected to the reaction distillation tower water cooler E02, the gas phase at the top of the reaction distillation tower T01 enters the reaction distillation tower water cooler E02, and the condensate of the reaction distillation tower water cooler E02 returns to the top of the reaction distillation tower T01.

[0021] The gas phase of the reaction distillation tower water cooler E02 is connected to the fixed bed reactor R01. The non-condensable steam (or the non-condensable steam and reaction adjustment mixed flow) of the reaction distillation tower water cooler E02 enters the fixed bed reactor R01. The reaction reaches component equilibrium in the fixed bed reactor R01, and the reaction products enter the back-end component separation device.

[0022] Preferably, in this embodiment, the feed rate of the reactive distillation tower feed stream s01 is 100 kg / h-10 t / h, the operating pressure of the reactive distillation tower T01 is 2.5 barg-3.5 barg, and the water cooling temperature is 35°C-45°C.

[0023] Example 2 A device for producing silane by coupled reactive distillation and fixed-bed reactors, used to implement the process for producing silane by coupled reactive distillation and fixed-bed reactors described in Example 1, comprises a reactive distillation column T01, a fixed-bed reactor R01, a reactive distillation column reboiler E01, and a reactive distillation column water cooler E02. Reactive distillation column T01 is equipped with separation and catalytic internals; fixed-bed reactor R01 is equipped with catalysts and filtration internals.

[0024] The reaction distillation tower T01 has a feed port, a first return port, a second return port, and a second outlet and a first outlet at its upper and lower ends. The first outlet is connected to the reaction distillation tower reboiler E01, and the reaction distillation tower bottom liquid flow s03 transported by the first outlet is transported to the rear-end component separation device. The gas-liquid mixed phase outlet of the reaction distillation tower reboiler E01 is connected to the first return port; the second outlet is connected to the reaction distillation tower water cooler E02, and the condensate outlet of the reaction distillation tower water cooler E02 is connected to the second return port through a pipeline.

[0025] The gas phase outlet of the reaction distillation tower water cooler E02 is connected to the inlet of the fixed bed reactor R01, the outlet of the fixed bed reactor R01 is connected to the rear-end component separation device, and the outlet of the fixed bed reactor R01 transports the fixed bed reactor outlet logistics s04.

[0026] The reactive distillation tower T01 is provided with a plurality of packing separation layers spaced apart from each other from top to bottom. A corresponding reaction section is installed above each separation packing layer. The number of packing separation layers is 5-9.

[0027] In this embodiment, the reaction distillation tower feed stream s01 enters the middle part of the reaction distillation tower T01, the bottom of the reaction distillation tower T01 is connected to the reaction distillation tower reboiler E01 to provide heat, the top of the reaction distillation tower T01 is connected to the reaction distillation tower water cooler E02 to provide cooling, the top of the reaction distillation tower overhead gas stream s02 (or the overhead gas and reaction adjustment mixed stream) enters the fixed bed reactor R01 to continue the reaction, the reaction product fixed bed reactor outlet stream s04 is separated, and the reaction distillation tower bottom liquid stream s03 is returned to the front-end system as a by-product.

[0028] Process description: The feed stream s01 of the reactive distillation tower is trichlorosilane. The feed stream s01 of the reactive distillation tower enters the tower from the middle of the reactive distillation tower T01 and reacts under the action of the catalyst. The reaction equation is as follows: 1. 2SiHCl3 = SiH2Cl2 + SiCl4 2. 2SiH2Cl2 = SiHCl3 + SiH3Cl 3. 2SiH3Cl = SiH2Cl2 + SiH4 After the reaction, the column contains a mixture of five components: SiCl₄, SiHCl₃, SiH₂Cl₂, SiH₃Cl, and SiH₄. The composition of these five components varies at different locations within the column, depending on their boiling points. The top of the reactive distillation column feed stream S01 primarily contains light components (primarily SiHCl₃, SiH₂Cl₂, SiH₃Cl, SiH₄, and a small amount of SiCl₄), while the bottom of the reactive distillation column feed stream S01 contains heavy components (primarily SiCl₄, with a small amount of SiHCl₃).

[0029] The reactive distillation column reboiler E01 at the bottom of the tower heats the material with steam, continuously heating and evaporating the heavy components at the bottom, causing the liquid material to heat and vaporize, rising from the bottom of the tower. The reboiler material circulation ensures that the bottom material is free of SiH2Cl2, SiH3Cl, and SiH4, and that the SiHCl3 content is kept to an extremely low level. The majority of the material is SiCl4.

[0030] The water-cooled E02 at the top of the reactive distillation tower cools and condenses the material, continuously condensing the light components at the top, cooling and liquefying the vapor phase, which then falls downward. This ensures that the composition of the material in the overhead gas stream S02 (the discharge from the reactive distillation tower) is kept to extremely low levels of SiHCl3 and SiCl4, while also ensuring the content of SiH2Cl2, SiH3Cl, and SiH4.

[0031] The reactive distillation tower overhead gas stream s02 enters the fixed-bed reactor R01 for further reaction, repeating the above reaction process to further increase the silane content. The fixed-bed reactor outlet stream s04 enters a separation tower for further separation of its components, ultimately yielding the silane product. The reactive distillation tower bottoms liquid stream s03 is discharged from the bottom of the tower as a reaction byproduct and stored in a tank area for future use.

[0032] In addition, in order to reduce the overall downtime of the coupled equipment, an online catalyst replacement system can be added to the reaction distillation tower. A catalyst inlet is set at the upper part of the filling chamber between the cover plate and the bottom plate of the catalytic section. The catalyst inlet is connected to the lower discharge port of the new catalyst storage tank through a switch valve. A catalyst outlet is set at the lower part of the filling chamber. The catalyst outlet is also connected to the discharge port of the old catalyst storage tank through a switch valve. Through the control system, the catalyst outlet switch valve is opened and the catalyst inlet switch valve is closed, so that the catalyst in the catalytic section is carried into the old catalyst storage tank by the liquid material. After all the old catalyst flows out, the catalyst outlet switch valve is closed, and the old catalyst is removed after solid-liquid separation in the old catalyst storage tank. Next, the two switch valves are closed, and the new catalyst storage tank is filled with new catalyst. Then the catalyst inlet switch valve is opened to load the new catalyst into the catalytic section. Using this system, the catalyst can be replaced online for multiple catalytic sections in sequence, reducing the overall downtime of the coupled equipment.

[0033] In the above embodiment, if a mixed flow of non-condensable steam (tower overhead gas) and reaction regulation is used, while adding a SiHCl3 feed pipeline at the inlet of the fixed-bed reactor R01, it is necessary to use an MFC flow controller to dynamically adjust the mixing ratio of SiHCl3 and non-condensable steam, and the adjustment is based on the SiH4 / SiHCl3 ratio at the fixed-bed outlet.

[0034] Example 3 Based on Examples 1 and 2, in this example, the feed rate of the reactive distillation column feed stream s01 is 100 kg / h, the operating pressure of the reactive distillation column T01 is 3 barg, and the water cooling temperature is 35° C. The material balance is as follows: From the above material balance, it can be seen that the top gas stream s02 of the reactive distillation tower is the fixed bed inlet stream, and its silane yield is calculated to be 4.48 / 100*100%=4.48%; The fixed bed reactor outlet stream s04 is the fixed bed outlet stream, and its silane yield is calculated to be 4.72 / 10000*100%=4.72%; The relative value of yield increase is (4.72-4.48) / 4.48*100%=5.4%.

[0035] Example 4 Based on Examples 1 and 2, in this example, the feed rate of the reactive distillation column feed stream s01 is 1 t / h, the operating pressure of the reactive distillation column T01 is 3.5 barg, and the water cooling temperature is 45°C. The material balance is as follows: From the above material balance, it can be seen that the top gas stream s02 of the reactive distillation tower is the fixed bed inlet stream, and its silane yield is calculated to be 41.99 / 1000*100%=4.2%; The fixed bed reactor outlet stream s04 is the fixed bed outlet stream, and its silane yield is calculated to be 44.67 / 1000*100%=4.47%; The relative value of yield increase is (4.47-4.2) / 4.2*100%=6.4%.

[0036] Example 5 Based on Examples 1 and 2, in this example, the feed rate of the reactive distillation column feed stream s01 is 10 t / h, the operating pressure of the reactive distillation column T01 is 2.5 barg, and the water cooling temperature is 40° C. The material balance is as follows: From the above material balance, it can be seen that the top gas stream s02 of the reactive distillation tower is the fixed bed inlet stream, and its silane yield is calculated to be 397.06 / 10000*100%=3.97%; The fixed bed reactor outlet stream s04 is the fixed bed outlet stream, and its silane yield is calculated to be 426.18 / 10000*100%=4.26%; The relative value of yield increase is (4.26-3.97) / 3.97*100%=7.3%.

[0037] In summary, the present invention installs a fixed bed inside a distillation tower, and the reaction + distillation are integrated and carried out simultaneously. By arranging a fixed bed reactor at a specific position in the reactive distillation system, the coupling of reactive distillation and the fixed bed is realized. Without the need for reaction adjustment, the single-pass yield of silane can be increased by 5-8%, thereby reducing the separation circulation amount of chlorosilane and improving the silane production efficiency.

[0038] Under the same feed rate and operating conditions, if the reaction-regulated mixed flow is enabled, the MFC flow controller dynamically adjusts the mixing ratio of SiHCl3 and non-condensable steam to ensure that the SiH4 / SiHCl3 molar ratio at the fixed bed outlet, as detected in real time, does not exceed the range of 0.8 to 1.2. The outlet yield can be relatively increased by approximately 8.9-11.3%, and the single-pass silane yield can be further increased to over 10%.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be based on the claims.

Claims

1. A process for preparing silane by coupling reactive distillation with a fixed bed, characterized in that: include: A reactive distillation tower (T01) is provided, wherein separation internals and catalytic internals are loaded therein to realize the reactive distillation process; A fixed bed reactor (R01) is provided, wherein the catalyst and filter internals are loaded therein to realize a fixed bed reaction process; The bottom of the reaction distillation tower (T01) is connected to the reaction distillation tower reboiler (E01), the liquid phase at the bottom of the reaction distillation tower (T01) enters the reaction distillation tower reboiler (E01), and the gas-liquid mixed phase after vaporization in the reaction distillation tower reboiler (E01) returns to the bottom of the reaction distillation tower (T01); the top of the reaction distillation tower (T01) is connected to the reaction distillation tower water cooler (E02), the gas phase at the top of the reaction distillation tower (T01) enters the reaction distillation tower water cooler (E02), and the condensate of the reaction distillation tower water cooler (E02) returns to the top of the reaction distillation tower (T01); The gas phase of the reaction distillation tower water cooler (E02) is connected to the fixed bed reactor (R01), and the non-condensed steam of the reaction distillation tower water cooler (E02) enters the fixed bed reactor (R01), and the reaction reaches component equilibrium in the fixed bed reactor (R01), and the reaction products enter the rear-end component separation device.

2. The process for preparing silane by coupling reactive distillation with a fixed bed according to claim 1, characterized in that: The catalytic internals filled in the reactive distillation tower (T01) are catalysts, and the catalysts are molecular sieves, alumina, resin particles or activated carbon.

3. The process for preparing silane by coupling reactive distillation with a fixed bed according to claim 1, characterized in that: The separation internals of the reactive distillation tower (T01) are structured packing, random packing or tower trays.

4. The process for preparing silane by coupling reactive distillation with a fixed bed according to claim 1, characterized in that: The catalyst inside the fixed bed reactor (R01) is molecular sieve, alumina, resin particles or activated carbon.

5. The process for preparing silane by coupling reactive distillation with a fixed bed according to claim 1, characterized in that: The filtering internals of the fixed bed reactor (R01) are a water cap, a wire mesh or a grid.

6. The process for preparing silane by coupling reactive distillation with a fixed bed according to claim 1, characterized in that: The feed rate of the reactive distillation tower (T01) is 100 kg / h-10 t / h.

7. The process for preparing silane by coupling reactive distillation with a fixed bed according to claim 1, characterized in that: The operating pressure of the reactive distillation tower (T01) is 2.5 barg -3.5 barg, and the water cooling temperature is 35℃-45℃.

8. An apparatus for preparing silane by coupling reactive distillation with a fixed bed, for implementing the process according to any one of claims 1 to 7, characterized in that: include: A reactive distillation tower (T01) is filled with separation internals and catalytic internals; A fixed bed reactor (R01) filled with catalyst and filter internals; The reaction distillation tower (T01) has a feed inlet, a first return inlet, a second return inlet, and a second outlet and a first outlet provided at its upper and lower ends, the first outlet being connected to a reaction distillation tower reboiler (E01), and the gas-liquid mixed phase outlet of the reaction distillation tower reboiler (E01) being connected to the first return inlet; the second outlet being connected to a reaction distillation tower water cooler (E02), and the condensate outlet of the reaction distillation tower water cooler (E02) being connected to the second return inlet via a pipeline; The gas phase outlet of the reaction distillation tower water cooler (E02) is connected to the inlet of the fixed bed reactor (R01), and the outlet of the fixed bed reactor (R01) is connected to the rear-end component separation device.

9. The process for preparing silane by coupling reactive distillation with a fixed bed according to claim 8, characterized in that: The reactive distillation tower (T01) is provided with a plurality of packing separation layers spaced apart from each other from top to bottom, and a corresponding reaction section is installed above each separation packing layer.

10. The process for preparing silane by coupling reactive distillation with a fixed bed according to claim 9, characterized in that: The number of the filler separation layers is 5-9.

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