A method for separating hydrogen / silane at high temperature using a molecular sieve membrane

Abstract

The application relates to a method for separating hydrogen / silane, in particular to a method for separating hydrogen / silane at high temperature by using a molecular sieve membrane. The application uses a molecular sieve membrane as a key membrane material, realizes the separation of hydrogen and silane at high temperature, and the high-temperature environment of a specific temperature can also modify the membrane defects of the molecular sieve membrane, so that the separation performance of the membrane for hydrogen and silane is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for separating hydrogen / silane, in particular to a method for separating hydrogen / silane at high temperature by using a molecular sieve membrane. BACKGROUND

[0002] Silane (SiH4), also known as silane, as a gas source for carrying silicon components, is widely used in microelectronics, optoelectronics industry and other industries due to its high purity and fine control. Monosilane is converted into crystalline silicon by pyrolysis reaction, which is one of the methods for large-scale production of granular monocrystalline silicon and polycrystalline silicon in the world. However, the purity of silane gas in the pyrolysis reaction process will affect the purity of silicon-based crystals, and the purity of silicon-based crystals will greatly affect the performance of products in the downstream industry. Therefore, the separation and preparation of high-purity (6N) silane has become one of the industry problems.

[0003] In industry, silane is produced by chlorosilane method, using silicon, silicon tetrachloride, hydrogen and other substances as raw materials, which are converted into trichlorosilane and part of chlorosilane through catalytic reaction, and the unreacted hydrogen is recycled in the system. Then the chlorosilane mixture is separated by rectification to remove a small amount of impurities, and finally a high-purity trichlorosilane is obtained for use in the disproportionation reaction system, and the separated silicon tetrachloride is returned to the system for recycling. In the disproportionation reaction system, trichlorosilane is reacted to generate silane gas under the conditions of high temperature, pressure and catalyst. In the whole process, in order to reduce the production cost, the excess hydrogen can be recycled, but since hydrogen is easy to form a mixture with silane product, further purification is needed.

[0004] For the separation of hydrogen and silane, the existing technology often uses rectification and adsorption, but the high energy consumption and low separation efficiency greatly increase the production cost. Membrane separation technology is a new separation technology, which is expected to play an important role in the separation of hydrogen and silane. However, the mixed gas flowing out from the disproportionation reaction system is a high-temperature gas, which needs to be cooled to room temperature before membrane separation. This additional cooling step not only increases the complexity of the production process, but also leads to waste of heat energy. Molecular sieve membrane is a kind of high-temperature resistant membrane material, but there is no case of using molecular sieve membrane for the separation of hydrogen and silane in the existing technology. Therefore, the inventors attempt to use molecular sieve membrane as a key membrane material for the separation of hydrogen and silane, but the molecular sieve membrane needs to be calcined to remove the template agent during the preparation process, which is easy to produce membrane defects during the removal of the template agent, resulting in low separation selectivity of hydrogen and silane at room temperature. Therefore, how to realize the separation of hydrogen and silane at high temperature is a problem to be solved. SUMMARY

[0005] In view of the above problems, the application uses a molecular sieve membrane as a key membrane material to separate hydrogen and silane at high temperature, and silane modifies the membrane defects of the molecular sieve membrane at a specific high temperature environment, thereby improving the separation performance of the membrane for hydrogen and silane.

[0006] Specifically, the application provides a method for separating hydrogen / silane at high temperature by using a molecular sieve membrane, which comprises continuously feeding a high-temperature mixed gas containing hydrogen and silane into a membrane separation device to retain silane on the retentate side, the temperature of the high-temperature mixed gas is 100-400 ℃, and the membrane material used in the membrane separation device is a molecular sieve membrane.

[0007] Preferably, the molecular sieve membrane is an SSZ-13 molecular sieve membrane.

[0008] Preferably, the separation selectivity of the SSZ-13 molecular sieve membrane for hydrogen / silane at a temperature of 100-400 ℃ reaches 20-100.

[0009] Preferably, the hydrogen on the permeate side is further fed into an adsorption device for purification.

[0010] Preferably, the concentration of hydrogen in the high-temperature mixed gas is > 99%.

[0011] Preferably, the concentration of hydrogen on the permeate side of the membrane separation device is > 99.9%, the flow rate of the permeate hydrogen is > 1 m 3 h -1 m -2 , and the concentration of silane on the permeate side is < 0.04%.

[0012] Preferably, the preparation method of the SSZ-13 molecular sieve membrane comprises:

[0013] (a) converting a USY molecular sieve into a high-silicon CHA molecular sieve under the action of a structure directing agent, and obtaining a crystal seed after calcination;

[0014] (b) preparing the crystal seed into a crystal seed suspension, applying the crystal seed suspension to the surface of a carrier, and then placing the carrier in a synthesis solution for hydrothermal synthesis, and obtaining an SSZ-13 molecular sieve membrane after calcination to remove the template agent.

[0015] Preferably, the calcination of the template agent in step (b) is carried out under an ozone atmosphere, the calcination temperature is 180-250 ℃, the calcination time is 24-144 h, and the heating and cooling rate is 0.5-2 ℃ / min.

[0016] Compared with the prior art, the application has the following advantages:

[0017] First, this invention utilizes molecular sieve membranes as the key membrane material, achieving direct separation of silanes and hydrogen at high temperatures. This innovative technology avoids the additional step of cooling the mixed gas required by traditional organic membranes, thus simplifying the production process and significantly saving energy. Molecular sieve membranes possess excellent high-temperature resistance, maintaining stable separation efficiency even at high temperatures, thereby improving the continuity and reliability of the production process.

[0018] Secondly, regarding the potential membrane defects that may exist during the preparation of molecular sieve membranes, this invention utilizes the reaction between silane and the silanol groups at the membrane defects at high temperatures, thereby achieving self-modification of the membrane. This self-modification not only improves the separation performance of the molecular sieve membrane for silane and hydrogen, but also enhances the membrane's durability and stability. Attached Figure Description

[0019] Figure 1 Example 1: Separation process flow diagram;

[0020] Figure 2 Example 2: Separation process flow diagram;

[0021] Figure 3 XRD pattern of the SSZ-13 molecular sieve membrane prepared in Example 3;

[0022] Figure 4 SEM image of the SSZ-13 molecular sieve membrane prepared in Example 3. Detailed Implementation

[0023] Example 1

[0024] Figure 1 This is a flowchart of this embodiment, wherein, as Figure 1 As shown, the membrane separation unit uses an SSZ-13 molecular sieve membrane. At a temperature of 120℃, the feed composition is 99.5% H2 / 0.5% SiH4. At a feed pressure of 0.2 MPa, when the feed flow rate is 1.3 m³ / min... 3 ·h -1 ·m -2 Increased to 13.4 m 3 ·h -1 ·m -2 H2 permeability decreased from 7.59 × 10⁻⁶ -8 mol·m -2 ·s -1 ·Pa -1 Increased to 7.90 × 10 -8 mol·m -2 ·s -1 ·Pa -1The SiH4permeance decreases with the increase of feed flow rate and the decrease of feed pressure, and when the feed pressure is 0.2 MPa and the feed flow rate is 1.3 m 3 ·h -1 ·m -2 The H2permeance is 7.90 × 10 - 8 mol·m -2 ·s -1 ·Pa -1 The SiH4permeance is 9.53 × 10 -10 mol·m -2 ·s -1 ·Pa -1 , and the separation selectivity of H2 / SiH4is 83.

[0025] The SSZ-13 molecular sieve membrane before and after the test is subjected to equimolar hydrogen / silane separation, and it is found that the hydrogen / silane separation performance is still good after high-temperature test, which shows that the membrane has good high-temperature stability, and the hydrogen / silane separation selectivity is improved, which proves that silane will react with the silicon hydroxyl at the defect of the membrane at high temperature, so as to realize the self-modification of the membrane.

[0026] Table 1 Stability test of separation membrane

[0027]

[0028] Example 2

[0029] Example 2 adopts the process flow as shown in Figure 2 , and the H2 / SiH4separation experiment is carried out at 120℃ under the condition that the feed side pressure is 0.8 MPa and the permeation side pressure is 0.6 MPa. When the feed flow rate is 7.2 m 3 ·h -1 ·m -2 , the H2permeation side flow rate of the membrane is 1.4 m 3 ·h -1 ·m -2 , the SiH4concentration is reduced to 192 ppm, the H2is purified to 99.98%, and the silane concentration in the retentate gas is 0.61%. In order to further reduce the silane concentration, the mixed gas is further purified by adsorption. The use of molecular sieve adsorbent can further improve the H2purity, and the SiH4concentration is reduced to 9 ppm.

[0030] Example 3

[0031] The SSZ-13 molecular sieve membrane used in Examples 1 and 2 is prepared as follows:

[0032] (1) According to the raw material molar ratio 100SiO2: 1.25Al2O3: 40TMAdaOH: 500H2O, USY molecular sieve, N, N, N-trimethyl-1-adamantane ammonium hydroxide and water were sequentially mixed and stirred until a stable solution was formed;

[0033] (2) The synthesis solution was poured into a stainless steel reactor with a polytetrafluoroethylene lining, and hydrothermal synthesis was carried out in an oven at 175°C for 14 days; after the reaction was completed, the product was centrifuged and calcined at 600°C for 12h;

[0034] (3) The molecular sieve obtained in step (2) was used as a seed crystal, deionized water was used as a dispersant, a 0.5wt.% seed crystal solution was prepared, and a seed crystal layer was coated on the hollow fiber carrier by a pull-dip impregnation method, with a coating time of 15s;

[0035] (4) According to the raw material molar ratio 105SiO2: 0.525Al2O3: 20TMAdaOH: 12Na2O: 4400H2O, USY molecular sieve, N, N, N-trimethyl-1-adamantane ammonium hydroxide, sodium hydroxide and water were sequentially mixed and stirred until a stable solution was formed;

[0036] (5) The carrier treated in step (3) was placed in a stainless steel reactor with a polytetrafluoroethylene lining, and the solution of step (4) was poured into the reactor, and synthesis was carried out at 180°C for 96h; the molecular sieve membrane was calcined at 220°C in an ozone atmosphere for 96h to remove the template, and the heating and cooling rate was 1°C / min, to obtain a SSZ-13 molecular sieve membrane (its XRD characterization chart is shown in Figure 3 , and its SEM characterization is shown in Figure 4 ).

[0037] Finally, it should be pointed out that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for separating hydrogen / SiH4 at high temperature using a molecular sieve membrane, characterized by, A high-temperature mixed gas containing hydrogen and SiH4 is continuously introduced into a membrane separation device to retain silane on the retentate side, the temperature of the high-temperature mixed gas is 100-400℃, the membrane material used in the membrane separation device is a molecular sieve membrane, and self-modification of the membrane is achieved by the reaction of SiH4 with silicon hydroxyl groups at defects in the membrane at high temperature; the molecular sieve membrane is an SSZ-13 molecular sieve membrane; and the hydrogen concentration in the high-temperature mixed gas is >99%.

2. The method of claim 1, wherein, The hydrogen on the permeate side is further introduced into an adsorption device for purification.

3. The method of claim 1, wherein, The membrane separation device has a permeation side hydrogen concentration > 99.9%, a permeation hydrogen flow > 1m 3 h -1 m -2 , and a permeation side SiH4 concentration < 0.04%.

4. The method of claim 1, wherein, The separation selectivity of the SSZ-13 molecular sieve membrane for hydrogen / SiH4 at a temperature of 100-400℃ reaches 20-100.

5. The method of claim 1, wherein, The preparation method of the SSZ-13 molecular sieve membrane comprises: (a) converting USY molecular sieve into high-silicon CHA molecular sieve under the action of a structure directing agent to obtain seed crystals after calcination; (b) preparing a seed crystal suspension from the seed crystals, applying the seed crystal suspension to the surface of a carrier, placing the carrier in a synthesis solution for hydrothermal synthesis, and obtaining the SSZ-13 molecular sieve membrane after calcination to remove the template agent.

6. The method of claim 5, wherein, The calcination to remove the template agent in step (b) is performed in an ozone atmosphere, the calcination temperature is 180-250℃, the calcination time is 24-144h, and the heating and cooling rates are 0.5-2℃ / min.

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