CN110980738B - System and method for preparing disilane and trisilane by silane pyrolysis method - Google Patents
System and method for preparing disilane and trisilane by silane pyrolysis method Download PDFInfo
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Abstract
The invention discloses a system and a method for preparing disilane and trisilane by a silane pyrolysis method, which are characterized by comprising a raw material heater, a silane pyrolysis reactor, a heat exchange and compression system, a hydrogen separator, a crude silane separator, a silane separation tower, a crude disilane separator and a disilane separation tower which are sequentially connected, wherein a gas phase outlet of the hydrogen separator, a gas phase outlet of the crude silane separator and a gas phase outlet of the silane separation tower are respectively connected with a shell pass inlet of the heat exchange and compression system, a shell pass outlet of the heat exchange and compression system is connected with an inlet of the raw material heater, a top gas phase outlet of the crude disilane separator and a top gas phase outlet of the crude disilane separation tower are respectively connected with an external disilane storage tank, and a bottom liquid phase outlet of the disilane separation tower is connected with the external trisilane storage tank.
Description
Technical Field
The invention relates to a system and a method for preparing disilane and trisilane by a silane pyrolysis method.
Background
In recent years, the silane industry has been greatly developed in China, and silane has been widely used in the microelectronics and optoelectronics industries as a gas source for providing silicon components. Disilane and trisilane are chemically more reactive than silane. Disilane and trisilane play an extremely important role in thin film transistor liquid crystal display, chip manufacturing and amorphous silicon solar cell production, and when being used as a deposition source, compared with silane with the same role, the disilane and trisilane have the advantages of high deposition speed, low deposition temperature and the like. In terms of price, disilane and trisilane are more than several hundred times more expensive than silane. With the development of society, the application of electronic products is more and more extensive, the demand of solar cells is more and more, and amorphous silicon is used in the production of the electronic products. With the increasing demand for amorphous silicon, disilane and trisilane have incomparable advantages over silane, and the market demand for disilane and trisilane is also increasing.
At present, the methods for producing disilane and trisilane mainly comprise: 1. magnesium silicide is reacted with ammonium chloride. The main product of the reaction is silane, and a small amount of higher-order silane such as disilane and trisilane is also associated with the reaction. 2. A halodisilane reduction method. With lithium aluminium hydride (LiAlH)4) Or sodium aluminum hydride (NaAlH)4) Reduction of hexachlorodisilane (Si)2Cl6) Preparing disilane. Although the method has high disilane yield, the raw materials are expensive, and the silicide separation is difficult, so that the industrial application of the method is limited. 3. The magnesium silicide reacts with the mineral acid. In addition to disilane, trisilane, and higher order silanes, the process uses a concomitant large amount of silane. 4. Preparing disilane by using silane as an initial raw material. Silane is used as an initial raw material, and can be converted into disilane and trisilane by methods such as thermal decomposition, photolysis, atom excitation, electrostatic field, glow discharge and the like. Photolysis, atomic excitation, electrostatic field and glow discharge are all carried out under the condition of very low silane pressure, and the device is difficult to develop and has low practical value.
Disclosure of Invention
The invention aims to solve the technical problem of providing a system and a method for preparing disilane and trisilane by a silane pyrolysis method with good conversion efficiency and high product purity
The technical scheme adopted by the invention for solving the technical problems is as follows: the system for preparing disilane and trisilane by a silane pyrolysis method comprises a raw material heater, a silane pyrolysis reactor, a heat exchange and compression system, a hydrogen separator, a silane crude separator, a silane separation tower, a disilane crude separator and a disilane separation tower which are sequentially connected, wherein a gas phase outlet of the hydrogen separator, a gas phase outlet of the silane crude separator and a gas phase outlet of the silane separation tower are respectively connected with a shell pass inlet of the heat exchange and compression system, a shell pass outlet of the heat exchange and compression system is connected with a raw material heater inlet, a top gas phase outlet of the disilane crude separator and a top gas phase outlet of the disilane separation tower are respectively connected with an external disilane storage tank, and a bottom liquid phase outlet of the disilane separation tower is connected with the external trisilane storage tank.
A first pressure reducing valve and a first heater are sequentially arranged at a material inlet of the silane rough separator; and a second pressure reducing valve and a second heater are sequentially arranged at a material inlet of the crude disilane separator.
The heat exchange and compression system comprises a compressor and a heat exchange system, the heat exchange system comprises a first heat exchanger, a second heat exchanger, a third heat exchanger, a fourth heat exchanger, a fifth heat exchanger, a sixth heat exchanger and a seventh heat exchanger which are sequentially connected, a gas phase outlet of the hydrogen separator is connected with a shell pass inlet of the sixth heat exchanger, a shell pass outlet of the sixth heat exchanger, a gas phase outlet of the silane rough separator and a gas phase outlet of the silane separation tower are respectively connected with a shell pass inlet of the fourth heat exchanger, a shell pass of the third heat exchanger, a shell pass of the second heat exchanger and a shell pass of the first heat exchanger are sequentially connected, and a refrigerant of the fifth heat exchanger and a refrigerant of the seventh heat exchanger are introduced. Since the hydrogen, silane, disilane and trisilane have very different boiling points in the process system and the reaction is carried out at high temperature, it is necessary to perform reasonable energy recovery in order to save heat and cold.
The compressor is arranged on a connecting pipeline between the shell side of the third heat exchanger and the shell side of the second heat exchanger.
A method for preparing disilane and trisilane by performing a silane pyrolysis method by using the system comprises the following steps:
(1) will be composed of H2And SiH4The raw materials are sent into a raw material heater for preheating, then sent into a silane pyrolysis reactor, the reaction temperature in the silane pyrolysis reactor is controlled to be 470-550 ℃, the pressure is controlled to be 0.6-1.3MPaG, and after the reaction is carried out for 5-30s, the mixed gas obtained by the pyrolysis of silane is sent into a reactorCooling in heat exchange and compression system, and feeding into hydrogen separator with H2And SiH4The concentration of silane in the raw materials is 20-35% mol;
(2) controlling the temperature in the hydrogen separator to be-130 to-110 ℃, controlling the pressure to be 0.3 to 1.3MPaG, separating the mixed gas to obtain hydrogen and mixed liquid, sending the hydrogen back to a heat exchange and compression system through a top outlet of the hydrogen separator, returning the hydrogen to a raw material heater inlet for recycling as a raw material after cold recovery and compression, sending the mixed liquid out through a bottom outlet of the hydrogen separator, and sending the mixed liquid into a silane crude separator after pressure reduction, heating and temperature rise in sequence;
(3) controlling the temperature in a silane coarse separator to be-100 to-20 ℃, controlling the pressure to be 0.2 to 0.8MPaG, roughly separating mixed liquid to obtain silane gas containing a small amount of disilane and disilane mixed liquid containing a small amount of silane and trisilane, sending the silane gas containing a small amount of disilane back to a heat exchange and compression system through a top outlet of the silane coarse separator, recovering cold energy, compressing, returning the silane gas to an inlet of a raw material heater for recycling as a raw material, and sending the disilane mixed liquid containing a small amount of silane and trisilane to a silane separation tower through a bottom outlet of the silane coarse separator;
(4) controlling the pressure in a silane separation tower to be 0.2-0.8MPaG, separating disilane mixed liquor containing a small amount of silane and trisilane to obtain silane gas and disilane liquid containing a small amount of trisilane, sending the silane gas back to a heat exchange and compression system through a top outlet of the silane separation tower, recovering cold energy, compressing, returning the silane gas to a raw material heater inlet for recycling, sending the disilane liquid containing a small amount of trisilane out through a bottom outlet of the silane separation tower, and sending the disilane liquid into a crude disilane separator after pressure reduction, heating and temperature rise in sequence;
(5) controlling the temperature in the crude disilane separator to be-10-50 ℃, controlling the pressure to be 0.01MPaG-0.8MPaG, carrying out crude separation on disilane liquid containing a small amount of disilane to obtain a disilane product with the purity of 99.9 percent and disilane liquid containing a small amount of disilane, and sending the disilane liquid containing a small amount of disilane into a disilane separation tower;
(6) controlling the pressure in the disilane separation tower to be 0.01MPaG-0.8MPaG, separating trisilane liquid containing a small amount of disilane to obtain a gas phase and a liquid phase, wherein the gas phase obtained at the tower top is disilane products with the purity of 99.9 percent, and the liquid phase obtained at the tower bottom is trisilane products with the purity of 99.9 percent.
Preferably, step (1) is performed by using H2And SiH4The raw material of (1) is heated to 500 ℃ by a raw material heater and then sent into a silane pyrolysis reactor, wherein H is used as a raw material2And SiH4The concentration of silane in the raw material of the composition was 25% mol.
Preferably, the reaction temperature in the silane pyrolysis reactor in the step (1) is controlled to be 500 ℃, the pressure is controlled to be 0.9MPaG, and the reaction time is controlled to be 10 s.
Preferably, the wall of the silane pyrolysis reactor in the step (1) adopts a jacket structure containing heat conducting oil, and the wall temperature is controlled to be 50-150 ℃. Surface reactions are avoided.
Preferably, the temperature in the hydrogen separator in the step (2) is controlled to-120 ℃ and the pressure is controlled to 0.9 MPaG.
The heat exchange and compression system comprises a compressor and a heat exchange system, the heat exchange system comprises a first heat exchanger, a second heat exchanger, a third heat exchanger, a fourth heat exchanger, a fifth heat exchanger, a sixth heat exchanger and a seventh heat exchanger which are sequentially connected, and the compressor is arranged between a shell side outlet of the third heat exchanger and a shell side inlet of the second heat exchanger; the heat exchange process comprises the following steps: the method comprises the following steps of (1) sequentially feeding materials from an outlet of a silane pyrolysis reactor into a first heat exchanger, a second heat exchanger, a third heat exchanger, a fourth heat exchanger, a fifth heat exchanger, a sixth heat exchanger and a seventh heat exchanger, sequentially carrying out heat exchange and cooling, and then feeding the materials into a hydrogen separator for separation; after the gas phase from the hydrogen separator is sent to a sixth heat exchanger for heat exchange, the gas phase is mixed with the gas phase from the silane crude separator and the silane separation tower at the shell pass outlet of the sixth heat exchanger, then the mixture is sent to a fourth heat exchanger and a third heat exchanger for heat exchange and temperature rise in sequence, then the mixture is pressurized and compressed to 0.9MpaG by a compressor, then the mixture is sent to a second heat exchanger and a first heat exchanger for heat exchange and temperature rise in sequence, then the mixture is sent to a raw material heater for heating, and then the mixture is sent to a silane pyrolysis reactor for recycling; and introducing the refrigerant into the fifth heat exchanger and the seventh heat exchanger to cool the material. The compressor is used for pressurizing and compressing hydrogen and a small amount of silane from the hydrogen separator and silane from the silane crude separator and the silane separation tower to 0.9MpaG to be mixed with fresh gas to enter the silane cracking reactor. The heat exchange system is used for saving heat and cold, and because the difference between the boiling points of hydrogen and silane is very large, the temperature needs to be reduced and condensed during separation, and the temperature needs to be increased during reaction, a plurality of shell-and-tube heat exchangers are arranged to facilitate energy recovery and reduce the consumption of heat and cold.
Compared with the prior art, the invention has the advantages that:
1. starting material H2、SiH4The gas mixture is heated by a raw material heater and then fed into a silane pyrolysis reactor, and 2SiH is generated in the pyrolysis reactor4→Si2H6＋H2 ，2Si2H6→Si3H8＋SiH4Reaction, Si formed by the reaction2H6，Si3H8And unreacted H2、SiH4Enters a compression and heat exchange system for heat exchange and then is cooled to SiH4Below the boiling point of (A), entering a hydrogen separator to utilize H2、SiH4、Si2H6,Si3H8The separation of silane and hydrogen is realized by the difference of boiling points;
2. the silane crude separator is used for primarily separating materials from the bottom of the hydrogen separator, the load of a silane separation tower required later is reduced by utilizing the principle of equilibrium distillation (flash evaporation), the molar ratio of silane to disilane is adjusted, if the silane crude separator is not arranged, the molar weight of a gas phase at the top of the silane separation tower is far greater than that of a liquid phase, and the silane separation tower cannot be operated;
3. the silane separation tower is a rectifying tower, the interior of the rectifying tower consists of a plurality of tower plates, and the separation is realized by utilizing the difference of relative volatility of silane and disilane, so that the silane and disilane are separated;
4. due to the fact thatDuring the pyrolysis of silane, a small amount of trisilane, 2Si, is produced2H6→Si3H8＋ SiH4The molar ratio of disilane to trisilane produced was 6.6:1, so a crude disilane separator was required to perform a preliminary separation of disilane and trisilane. The crude disilane separator is used for reducing the load of a disilane separation tower which is needed later, adjusting the molar ratio of disilane and trisilane and facilitating the operation of the subsequent disilane separation tower;
5. the disilane separation tower is a rectifying tower, the interior of the rectifying tower consists of a plurality of tower plates, and the separation is realized by utilizing the difference of the relative volatility of disilane and trisilane;
6. the heat exchange system adopts the heat of the material flow at the outlet of the reactor to fully exchange heat with the cold quantity at the gas phase outlet of the hydrogen separator, thereby saving energy consumption. And gas phases of the silane crude separator and the silane separation tower enter a heat exchanger matched with the temperature of the gas phases for full heat exchange. The range of the heat exchangers adopted by the heat exchange system is 5-10, and the optimal selection is 7. The extra cold energy of the heat exchange system is provided by liquid nitrogen, but is not limited to liquid nitrogen, and other refrigerants can be used.
In summary, according to the system and the method for preparing disilane and trisilane by the silane pyrolysis method, the conversion per pass of silane is not high, but unreacted silane is recycled, the total conversion rate of silane reaches more than 95%, and the purity of the final products disilane and trisilane reaches 99.9%.
Drawings
FIG. 1 is a schematic flow diagram of a system for preparing disilane and trisilane by the pyrolysis method of silane;
FIG. 2 is a schematic flow chart of a heat exchange and compression system apparatus in example 1;
FIG. 3 is a schematic flow chart of a heat exchange and compression system apparatus in example 2.
Detailed Description
The invention is described in further detail below with reference to the accompanying examples.
Detailed description of the preferred embodiment
A system for preparing disilane and trisilane by a silane pyrolysis method comprises a raw material heater 1, a silane pyrolysis reactor 2, a heat exchange and compression system 3, a hydrogen separator 4, a silane crude separator 5, a silane separation tower 6, a disilane crude separator 7 and a disilane separation tower 8 which are sequentially connected, wherein a gas phase outlet of the hydrogen separator 4, a gas phase outlet of the silane crude separator 5 and a gas phase outlet of the silane separation tower 6 are respectively connected with a shell pass inlet of the heat exchange and compression system 3, a shell pass outlet of the heat exchange and compression system 3 is connected with an inlet of the raw material heater 1, a top gas phase outlet of the disilane crude separator 7 and a top gas phase outlet of the disilane separation tower 8 are respectively connected with an external disilane storage tank 9, and a bottom liquid phase outlet of the disilane separation tower 8 is connected with an external trisilane storage tank 10.
In the specific embodiment, a first pressure reducing valve 11 and a first heater 12 are sequentially arranged at the material inlet of the silane rough separator 5; a second pressure reducing valve 13 and a second heater 14 are sequentially arranged at the material inlet of the crude disilane separator 7.
In this specific embodiment, as shown in fig. 2, the heat exchange and compression system 3 includes a compressor 15 and a heat exchange system, the heat exchange system includes a first heat exchanger 16, a second heat exchanger 17, a third heat exchanger 18, a fourth heat exchanger 19, a fifth heat exchanger 20, a sixth heat exchanger 21 and a seventh heat exchanger 22 which are connected in sequence, a gas phase outlet of the hydrogen separator 4 is connected to a shell side inlet of the sixth heat exchanger 21, a shell side outlet of the sixth heat exchanger 21, a gas phase outlet of the silane rough separator 5 and a gas phase outlet of the silane separation tower 6 are respectively connected to a shell side inlet of the fourth heat exchanger 19, a shell side of the third heat exchanger 18, a shell side of the second heat exchanger 17 and a shell side of the first heat exchanger 16 are connected in sequence, and a shell side of the fifth heat exchanger 20 and a shell side of the seventh heat exchanger 22 are both introduced into a refrigerant. The compressor 15 is arranged on a connecting pipeline between the shell side of the third heat exchanger 18 and the shell side of the second heat exchanger 17.
Detailed description of the invention
A method for preparing disilane and trisilane by performing a silane pyrolysis method by using the system of the first embodiment comprises the following steps:
(1) will be composed of H2And SiH4The raw materials are sent into a raw material heater 1 for preheating, then sent into a silane pyrolysis reactor 2, the reaction temperature in the silane pyrolysis reactor 2 is controlled to be 470-550 ℃, the pressure is controlled to be 0.6-1.3MPaG, after the reaction is carried out for 5-30s, the mixed gas obtained by the silane pyrolysis is sent into a heat exchange and compression system 3 for cooling, and then sent into a hydrogen separator 4, wherein H is used as a raw material2And SiH4The concentration of silane in the raw materials is 20-35% mol, the wall of the silane pyrolysis reactor 2 adopts a jacket structure containing heat conducting oil, and the temperature of the wall of the silane pyrolysis reactor is controlled to be 50-150 ℃;
(2) controlling the temperature in the hydrogen separator 4 to be-130 to-110 ℃, controlling the pressure to be 0.3 to 1.3MPaG, separating the mixed gas to obtain hydrogen and mixed liquid, sending the hydrogen back to the heat exchange and compression system 3 through a top outlet of the hydrogen separator 4, returning the hydrogen to an inlet of the raw material heater 1 for recycling as a raw material after recovering cold energy and compressing, sending the mixed liquid out through a bottom outlet of the hydrogen separator 4, and sending the mixed liquid into the silane crude separator 5 after pressure reduction and heating temperature rise in sequence;
(3) controlling the temperature in a silane crude separator 5 to be-100 to-20 ℃ and the pressure to be 0.2 to 0.8MPaG, roughly separating mixed liquid to obtain silane gas containing a small amount of disilane and disilane mixed liquid containing a small amount of silane and trisilane, sending the silane gas containing a small amount of disilane back to a heat exchange and compression system 3 through a top outlet of the silane crude separator 5, recovering cold energy and compressing the silane gas, returning the silane gas to an inlet of a raw material heater 1 to be used as a raw material for recycling, controlling the pressure in a silane separation tower 6 to be 0.2 to 0.8MPaG by the disilane mixed liquid (4) containing a small amount of silane and trisilane to be separated to obtain silane gas and disilane liquid containing a small amount of trisilane, sending the silane gas back to the heat exchange and compression system 3 through a top outlet of the silane separation tower 6, the cold energy is recovered and compressed, and then the cold energy is returned to the inlet of the raw material heater 1 to be used as the raw material for recycling, the disilane liquid containing a small amount of trisilane is sent out through the outlet at the bottom of the silane separation tower 6, and is sent into a crude disilane separator 7 after being subjected to pressure reduction and heating temperature rise in sequence;
(5) controlling the temperature in the crude disilane separator 7 to be-10-50 ℃ and the pressure to be 0.01-0.8MPaG, carrying out crude separation on disilane liquid containing a small amount of trisilane to obtain a disilane product with the purity of 99.9 percent and trisilane liquid containing a small amount of disilane, and sending the trisilane liquid containing a small amount of trisilane to a trisilane separation tower 8;
(6) the pressure in the disilane separation tower 8 is controlled to be 0.01-0.8MPaG, the trisilane liquid containing a small amount of disilane is separated to obtain a gas phase and a liquid phase, the gas phase obtained at the tower top is the disilane product with the purity of 99.9 percent, and the liquid phase obtained at the tower bottom is the trisilane product with the purity of 99.9 percent.
The heat exchange process of the heat exchange and compression system 3 specifically comprises the following steps: the method comprises the following steps of (1) sequentially feeding materials from an outlet of a silane pyrolysis reactor 2 into a first heat exchanger 16, a second heat exchanger 17, a third heat exchanger 18, a fourth heat exchanger 19, a fifth heat exchanger 20, a sixth heat exchanger 21 and a seventh heat exchanger 22, and sequentially carrying out heat exchange and cooling and then feeding the materials into a hydrogen separator 4 for separation; after the gas phase from the hydrogen separator 4 is sent to a sixth heat exchanger 21 for heat exchange, the gas phase from the silane crude separator 5 and the gas phase from the silane separation tower 6 are mixed at the shell pass outlet of the sixth heat exchanger 21, then the mixture is sent to a fourth heat exchanger 19 and a third heat exchanger 18 for heat exchange and temperature rise in sequence, then the mixture is pressurized and compressed to 0.9MpaG by a compressor 15, then the mixture is sent to a second heat exchanger 17 and a first heat exchanger 16 for heat exchange and temperature rise in sequence, then the mixture is sent to a raw material heater 1 for heating, and then the mixture is sent to a silane pyrolysis reactor 2 for recycling; and introducing the refrigerant into a fifth heat exchanger 20 and a seventh heat exchanger 22 to cool the materials.
In addition to the above examples, the reaction temperature in the silane pyrolysis reactor 2 may be any value within 470 ℃, 550 ℃, or 470 ℃ to 550 ℃, the pressure may be any value within 0.6MPaG, 1.3MPaG, or 0.6 to 1.3MPaG, the reaction may be any value within 5s, 30s, or 5 to 30s, from H2And SiH4The concentration of silane in the raw material of the composition can be any value within 20% mol, 35% mol or 20-35% mol; the temperature in the hydrogen separator 4 may be any value from-130 ℃ to-110 ℃ or from-130 ℃ to-110 ℃, and the pressure may be any value from 0.3MPaG, 1.3MPaG or 0.3MPaG to 1.3 MPaG; coarse separation of silaneThe temperature in the separator 5 can be any value within-100 ℃, 20 ℃ or-100 to-20 ℃, and the pressure can be any value within 0.2MPaG, 0.8MPaG or 0.2 to 0.8 MPaG; the pressure in the silane separation column 6 is controlled to be any of 0.2MPaG, 0.8MPaG or 0.2-0.8 MPaG; the temperature in the crude disilane separator 7 can be any value within-10 ℃, 50 ℃ or-10 ℃ to 50 ℃, and the pressure can be any value within 0.01MPaG, 0.8MPaG or 0.01MPaG to 0.8 MPaG; the pressure in the disilane separation column 8 may be any value from 0.01MPaG, 0.8MPaG, or 0.01MPaG to 0.8 MPaG.
Application example three
Example 1
According to the disilane product design scale of 72t/a (product is calculated by disilane, annual operation time is 7200 h), the reaction temperature in the silane pyrolysis reactor 2 is 500 ℃, and the reaction pressure is 0.9 MPaG. Silane conversion per pass of 5%, residence time of 10s, from H2And SiH4The concentration of silane in the raw material of the composition was 25% mol. The pressure in the hydrogen separator 4 was controlled to 0.9MPaG and the temperature was controlled to-120 ℃. The pressure of the crude silane separator 5 was 0.2MPaG at-80 ℃. The crude disilane separator 7 had a temperature of-40 ℃ and a pressure of 0.15 MPaG. After equilibration of the system, the fresh silane feed was 0.4054kmol/H per hour, the disilane production was 0.161kmol/H (about 10 kg/H), the trisilane production was 0.0278kmol/H (about 2.5kg/H), and venting H was required per hour20.21 Kmol/h. The reaction equation is: 2SiH4--Si2H6＋H22，Si2H6--Si3H8＋SiH4。
The number of the designed heat exchangers is 7, the total flow of the discharged reactor is 34.626kmol/h, the gas phase flow of the hydrogen separator 4 is 27.87kmol/h, and most of the components in the two flows are hydrogen, so the rough calculation of the heat exchange system can assume that the unit heat carrying capacity of the two flows is equal, and the proper heat loss is considered, the temperature of the gas phase outlet of the hydrogen separator 4 entering the No. six heat exchanger 21 is-110 ℃, the temperature of the gas phase mixture of the silane rough separator 5 and the silane separation tower 6 entering the No. four heat exchanger 19 is-80 ℃, and the design process flow is shown in FIG. 2.
Example 2
According to the designed scale of disilane of 30t/a, (the annual operation time of the product is 7200H based on disilane), the reaction temperature in the silane pyrolysis reactor 2 is 480 ℃, the reaction pressure is 1.1MpaG, the conversion per pass of the silane is 4 percent, the retention time is 15s, and the reaction is carried out on the basis of H2And SiH4The concentration of silane in the raw material is 22 mol%, the pressure in the hydrogen separator 4 is 1.1MPaG, and the temperature is-130 ℃. The pressure of the crude silane separator 5 was 0.3MPaG at-70 ℃. The crude disilane separator 7 had a temperature of-30 ℃ and a pressure of 0.2 MPaG. After equilibration of the system, the fresh silane feed per hour was 0.1745kmol/H, the disilane production was 0.067kmol/H (about 4.17kg/H), the trisilane production was 0.0135kmol/H (1.25kg/H), and venting H was required per hour20.094 Kmol/h. The reaction equation is: 2SiH4--Si2H6＋H22，Si2H6--Si3H8＋SiH4。
The number of the designed heat exchangers is 7, the total amount of the material flow out of the reactor is 18.719kmol/h, the gas phase material flow of the hydrogen separator 4 is 15.086kmol/h, and most of the components in the two material flows are hydrogen, so the rough calculation of the heat exchange system can assume that the unit heat carrying capacity of the two material flows is equal, the temperature of the gas phase outlet of the hydrogen separator 4 entering the No. six heat exchanger 21 is-120 ℃, the temperature of the gas phase mixture of the silane rough separator 5 and the silane separation tower 6 entering the No. four heat exchanger 19 is-70 ℃, and the design process flow is shown in FIG. 3.
The above description is not intended to limit the present invention, and the present invention is not limited to the above examples. Those skilled in the art should also realize that changes, modifications, additions and substitutions can be made without departing from the true spirit and scope of the invention.
Claims (9)
1. A system for preparing disilane and trisilane by a silane pyrolysis method is characterized in that: the device comprises a raw material heater, a silane pyrolysis reactor, a heat exchange and compression system, a hydrogen separator, a silane crude separator, a silane separation tower, a disilane crude separator and a disilane separation tower which are sequentially connected, wherein a gas phase outlet of the hydrogen separator, a gas phase outlet of the silane crude separator and a gas phase outlet of the silane separation tower are respectively connected with a shell pass inlet of the heat exchange and compression system, a shell pass outlet of the heat exchange and compression system is connected with an inlet of the raw material heater, a top gas phase outlet of the disilane crude separator and a top gas phase outlet of the disilane separation tower are respectively connected with an external disilane storage tank, a bottom liquid phase outlet of the disilane separation tower is connected with the external trisilane storage tank, the heat exchange and compression system comprises a compressor and a heat exchange system, and the heat exchange system comprises a first heat exchanger, a second heat exchanger and a disilane separation tower which are sequentially connected with one another, The shell side of the fourth heat exchanger, the shell side of the third heat exchanger, the shell side of the second heat exchanger and the shell side of the first heat exchanger are sequentially connected, and the shell side of the fifth heat exchanger and the shell side of the seventh heat exchanger are filled with refrigerants.
2. The system for preparing disilane and trisilane by pyrolysis of silane according to claim 1, wherein: a first pressure reducing valve and a first heater are sequentially arranged at a material inlet of the silane rough separator; and a second pressure reducing valve and a second heater are sequentially arranged at a material inlet of the crude disilane separator.
3. The system for preparing disilane and trisilane by pyrolysis of silane according to claim 2, wherein: the compressor is arranged on a connecting pipeline between the shell side of the third heat exchanger and the shell side of the second heat exchanger.
4. A method for producing disilane and trisilane by a silane pyrolysis process using the system of claim 1, comprising the steps of:
(1) will be composed of H2And SiH4The raw materials are sent into a raw material heater for preheating, then sent into a silane pyrolysis reactor, the reaction temperature in the silane pyrolysis reactor is controlled to be 470-550 ℃, the pressure is controlled to be 0.6-1.3MPaG, after the reaction is carried out for 5-30s, the mixed gas obtained by the silane pyrolysis is sent into a heat exchange and compression system for cooling, and then sent into a hydrogen separator, wherein H is used for removing hydrogen2And SiH4The concentration of silane in the raw materials is 20-35 mol%;
(2) controlling the temperature in the hydrogen separator to be-130 to-110 ℃, controlling the pressure to be 0.3 to 1.3MPaG, separating the mixed gas to obtain hydrogen and mixed liquid, sending the hydrogen back to a heat exchange and compression system through a top outlet of the hydrogen separator, returning the hydrogen to a raw material heater inlet for recycling as a raw material after cold recovery and compression, sending the mixed liquid out through a bottom outlet of the hydrogen separator, and sending the mixed liquid into a silane crude separator after pressure reduction, heating and temperature rise in sequence;
(3) controlling the temperature in a silane coarse separator to be-100 to-20 ℃, controlling the pressure to be 0.2 to 0.8MPaG, roughly separating mixed liquid to obtain silane gas containing a small amount of disilane and disilane mixed liquid containing a small amount of silane and trisilane, sending the silane gas containing a small amount of disilane back to a heat exchange and compression system through a top outlet of the silane coarse separator, recovering cold energy, compressing, returning the silane gas to an inlet of a raw material heater for recycling as a raw material, and sending the disilane mixed liquid containing a small amount of silane and trisilane to a silane separation tower through a bottom outlet of the silane coarse separator;
(4) controlling the pressure in a silane separation tower to be 0.2-0.8MPaG, separating disilane mixed liquor containing a small amount of silane and trisilane to obtain silane gas and disilane liquid containing a small amount of trisilane, sending the silane gas back to a heat exchange and compression system through a top outlet of the silane separation tower, recovering cold energy, compressing, returning the silane gas to a raw material heater inlet for recycling, sending the disilane liquid containing a small amount of trisilane out through a bottom outlet of the silane separation tower, and sending the disilane liquid into a crude disilane separator after pressure reduction, heating and temperature rise in sequence;
(5) controlling the temperature in the crude disilane separator to be-10-50 ℃, controlling the pressure to be 0.01MPaG-0.8MPaG, carrying out crude separation on disilane liquid containing a small amount of disilane to obtain a disilane product with the purity of 99.9 percent and disilane liquid containing a small amount of disilane, and sending the disilane liquid containing a small amount of disilane into a disilane separation tower;
(6) controlling the pressure in the disilane separation tower to be 0.01MPaG-0.8MPaG, separating trisilane liquid containing a small amount of disilane to obtain a gas phase and a liquid phase, wherein the gas phase obtained at the tower top is disilane products with the purity of 99.9 percent, and the liquid phase obtained at the tower bottom is trisilane products with the purity of 99.9 percent.
5. The process according to claim 4 for the preparation of disilane and trisilane by pyrolysis of silanes, characterized in that: in step (1), from H2And SiH4The raw material of (1) is heated to 500 ℃ by a raw material heater and then sent into a silane pyrolysis reactor, wherein H is used as a raw material2And SiH4The concentration of silane in the raw material of the composition was 25 mol%.
6. The process according to claim 4 for the preparation of disilane and trisilane by pyrolysis of silanes, characterized in that: in the step (1), the reaction temperature in the silane pyrolysis reactor is controlled to be 500 ℃, the pressure is controlled to be 0.9MPaG, and the reaction time is controlled to be 10 s.
7. The process according to claim 4 for the preparation of disilane and trisilane by pyrolysis of silanes, characterized in that: in the step (1), the wall of the silane pyrolysis reactor adopts a jacket structure containing heat conducting oil, and the temperature of the wall of the silane pyrolysis reactor is controlled to be 50-150 ℃.
8. The process according to claim 4 for the preparation of disilane and trisilane by pyrolysis of silanes, characterized in that: in the step (2), the temperature in the hydrogen separator is controlled to be-120 ℃, and the pressure is controlled to be 0.9 MPaG.
9. The method for preparing disilane and trisilane by the silane pyrolysis method according to any one of claims 4 to 8, wherein the heat exchange and compression system comprises a compressor and a heat exchange system, the heat exchange system comprises a first heat exchanger, a second heat exchanger, a third heat exchanger, a fourth heat exchanger, a fifth heat exchanger, a sixth heat exchanger and a seventh heat exchanger which are sequentially connected, and the compressor is arranged between a shell side outlet of the third heat exchanger and a shell side inlet of the second heat exchanger; the heat exchange process comprises the following steps: the method comprises the following steps of (1) sequentially feeding materials from an outlet of a silane pyrolysis reactor into a first heat exchanger, a second heat exchanger, a third heat exchanger, a fourth heat exchanger, a fifth heat exchanger, a sixth heat exchanger and a seventh heat exchanger, sequentially carrying out heat exchange and cooling, and then feeding the materials into a hydrogen separator for separation; after the gas phase from the hydrogen separator is sent to a sixth heat exchanger for heat exchange, the gas phase is mixed with the gas phase from the silane crude separator and the silane separation tower at the shell pass outlet of the sixth heat exchanger, then the mixture is sent to a fourth heat exchanger and a third heat exchanger for heat exchange and temperature rise in sequence, then the mixture is pressurized and compressed to 0.9MPaG by a compressor, then the mixture is sent to a second heat exchanger and a first heat exchanger for heat exchange and temperature rise in sequence, then the mixture is sent to a raw material heater for heating, and then the mixture is sent to a silane pyrolysis reactor for recycling; and introducing the refrigerant into the fifth heat exchanger and the seventh heat exchanger to cool the material.
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