Method for separating hydrogen / silane at high temperature by using molecular sieve membrane

Abstract

The invention 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. According to the invention, the molecular sieve membrane is used as a key membrane material, the separation of hydrogen and silane at a high temperature is realized, and the membrane defect of the molecular sieve membrane is modified in a high-temperature environment with a specific temperature, so that the separation performance of the membrane on hydrogen and silane is improved.

Description

Technical Field

[0001] The invention relates to a method for separating hydrogen / silane, and in particular to a method for separating hydrogen / silane at high temperature by using a molecular sieve membrane. Background Art

[0002] Silane (SiH 4 ), also known as silane, is a gas source for carrying silicon components. It is widely used in microelectronics, optoelectronics and other industries due to its high purity and ability to achieve fine control. Monosilane generates crystalline silicon through 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 during the pyrolysis reaction will affect the purity of silicon-based crystals, and the purity of silicon-based crystals will greatly affect the performance of downstream industry products. Therefore, the separation and preparation of high-purity (6N) silane has become one of the industry's problems.

[0003] The chlorosilane method is used in industry to produce silane, with silicon, silicon tetrachloride, hydrogen and other materials as raw materials, which are converted into trichlorosilane and part of chlorosilane through catalytic reaction, and the unreacted hydrogen is recycled in the system. The chlorosilane mixture is then distilled and separated to remove a small amount of impurity components, and finally a higher purity trichlorosilane is obtained for use in the disproportionation reaction system, while the separated silicon tetrachloride is returned to the system for recycling. In the disproportionation reaction system, trichlorosilane reacts to generate silane gas under high temperature, pressure and catalyst conditions. In the whole process, in order to reduce production costs, excess hydrogen can be recycled, but because hydrogen easily forms a mixture with the silane product, it needs to be further purified.

[0004] For the separation of hydrogen and silane, the prior art often uses distillation and adsorption, but the high energy consumption and low separation efficiency greatly increase the production cost. Membrane separation technology is an emerging separation technology, which is expected to play an important role in the separation of hydrogen and silane. However, the mixed gas flowing out of 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 a waste of heat energy. The molecular sieve membrane is a high-temperature resistant membrane material, but there is no case in the prior art that uses molecular sieve membranes for the separation of hydrogen and silane. Therefore, the inventor tried to use molecular sieve membranes as key membrane materials for the separation of hydrogen and silane, but the molecular sieve membrane needs to be calcined to remove the template during the preparation process, and membrane defects are easily generated during the process of removing the template, resulting in low separation selectivity when applied to the separation of hydrogen and silane at room temperature. Therefore, how to achieve the separation of hydrogen and silane at high temperature is a problem to be solved. Summary of the invention

[0005] In view of the above problems, the present invention uses molecular sieve membrane as the key membrane material to achieve the separation of hydrogen and silane at high temperature. Moreover, silane modifies the membrane defects of the molecular sieve membrane itself under a high temperature environment at a specific temperature, thereby improving the membrane's separation performance for hydrogen and silane.

[0006] Specifically, the present invention provides a method for separating hydrogen / silane at high temperature using a molecular sieve membrane, which includes continuously passing 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°C, and the membrane material used in the membrane separation device is a molecular sieve membrane.

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

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

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

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

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

[0012] Preferably, 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, and obtaining seed crystals after calcination; (b) The above seed crystals are prepared into a seed crystal suspension, applied to the surface of the carrier, and then the carrier is placed in a synthesis solution for hydrothermal synthesis. After calcination to remove the template agent, the SSZ-13 molecular sieve membrane is obtained.

[0013] Preferably, the template is calcined in step (b) under an ozone atmosphere, the calcination temperature is 180-250° C., the calcination time is 24-144 h, and the heating and cooling rates are 0.5-2° C. / min.

[0014] Compared with the prior art, the present invention has the following advantages: First, the present invention uses molecular sieve membrane as the key membrane material to achieve direct separation of silane and hydrogen at high temperature. This innovative technology avoids the additional step of cooling the mixed gas required by traditional organic membranes, thereby simplifying the production process and significantly saving energy. Molecular sieve membranes have excellent high temperature resistance and can maintain stable separation efficiency in high temperature environments, improving the continuity and reliability of the production process.

[0015] Secondly, for the problem of membrane defects that may exist in the preparation process of the molecular sieve membrane, the present invention uses silane to react with the silanol groups at the membrane defects at high temperature, thereby realizing self-modification of the membrane. This self-modification effect not only improves the separation performance of the molecular sieve membrane for silane and hydrogen, but also improves the durability and stability of the membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 : Separation process flow chart of embodiment 1; Figure 2 : Example 2 separation process flow chart; Figure 3 : XRD pattern of the SSZ-13 molecular sieve membrane prepared in Example 3; Figure 4 : SEM photograph of the SSZ-13 molecular sieve membrane prepared in Example 3. DETAILED DESCRIPTION

[0017] Example 1 Figure 1 is a flow chart of this embodiment, wherein, Figure 1 As shown in the figure, the membrane separation device uses SSZ-13 molecular sieve membrane, the feed composition is 99.5% H at a temperature of 120°C 2 / 0.5% SiH 4 When the feed pressure is 0.2 MPa, the feed flow rate is increased from 1.3 m 3 ·h -1 ·m -2 Increased to 13.4 m 3 ·h -1 ·m -2 , H 2 The permeability ranged from 7.59 × 10 -8 mol·m -2 ·s -1 ·Pa -1 Increased to 7.90 × 10 -8 mol·m -2 ·s -1 ·Pa -1 .SiH 4The permeability decreases with the increase of feed flow rate and the decrease of feed pressure. 3 ·h -1 ·m -2 When H 2 The permeability is 7.90 × 10 - 8 mol·m -2 ·s -1 ·Pa -1 , SiH 4 The permeability is 9.53 × 10 -10 mol·m -2 ·s -1 ·Pa -1 , at this time H 2 / SiH 4 The separation selectivity is 83.

[0018] The SSZ-13 molecular sieve membrane was subjected to equimolar hydrogen / silane separation before and after the test, and it was found that it still had good hydrogen / silane separation performance after high-temperature testing, indicating that the membrane has good high-temperature stability. At the same time, the hydrogen / silane separation selectivity is improved, proving that silane will react with the silicon hydroxyl groups at the membrane defects at high temperature, thereby achieving self-modification of the membrane.

[0019] Table 1 Separation membrane stability test Example 2 Example 2 uses Figure 2 The process flow shown in the figure is to carry out H2O2 at 120°C with a feed side pressure of 0.8 MPa and a permeate side pressure of 0.6 MPa. 2 / SiH 4 Separation experiment. When the feed flow rate is 7.2 m 3 ·h -1 ·m -2 , the H of the membrane 2 The permeate flow rate is 1.4 m 3 ·h -1 ·m -2 , SiH 4 The concentration dropped to 192 ppm, H 2 Purified to 99.98%, 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 increase H 2 Purity, SiH 4 The concentration dropped to 9 ppm.

[0020] Example 3 The specific preparation method of the SSZ-13 molecular sieve membrane used in Examples 1 and 2 is as follows: (1) According to the raw material molar ratio 100SiO 2 :1.25Al 2 O 3 :40TMAdaOH:500H 2 O, sequentially mix USY molecular sieves, N,N,N-trimethyl-1-adamantanammonium hydroxide and water, and stir until a stable solution is formed; (2) pouring the synthesis liquid into a stainless steel reactor lined with polytetrafluoroethylene, and hydrothermally synthesizing it in an oven at 175°C for 14 days; after the reaction, centrifuging the product and calcining it at 600°C for 12 hours; (3) The molecular sieve obtained in step (2) was used as a seed crystal, deionized water was used as a dispersant, a 0.5 wt.% seed crystal solution was prepared, and a seed crystal layer was coated on the hollow fiber carrier by a pull-up impregnation method, and the coating time was 15 s; (4) According to the raw material molar ratio 105SiO 2 :0.525Al 2 O 3 :20TMAdaOH:12Na 2 O:4400H 2 O prepares a synthetic solution, sequentially mixes USY molecular sieve, N,N,N-trimethyl-1-adamantanammonium hydroxide, sodium hydroxide and water, and stirs until a stable solution is formed; (5) The carrier obtained in step (3) was placed in a stainless steel reactor lined with polytetrafluoroethylene, and the solution of step (4) was poured into it. The reaction was performed at 180°C for 96 hours. The molecular sieve membrane was calcined at 220°C in an ozone atmosphere for 96 hours to remove the template agent. The heating and cooling rates were 1°C / min, and the SSZ-13 molecular sieve membrane (its XRD characterization diagram is shown in Figure 3 , its SEM characterization is shown in Figure 4 ).

[0021] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for separating hydrogen / silane at high temperature using a molecular sieve membrane, characterized in that: A high-temperature mixed gas containing hydrogen and silane 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° C. The membrane material used in the membrane separation device is a molecular sieve membrane.

2. The method according to claim 1, characterized in that The molecular sieve membrane is a SSZ-13 molecular sieve membrane.

3. The method according to claim 1, characterized in that The SSZ-13 molecular sieve membrane has a separation selectivity of 20-100 for hydrogen / silane at a temperature of 100-400°C.

4. The method according to claim 1, characterized in that: The hydrogen on the permeate side is further introduced into the adsorption device for purification.

5. The method according to claim 1, characterized in that The hydrogen concentration in the high-temperature mixed gas is greater than 99%.

6. The method according to claim 1, characterized in that The hydrogen concentration on the permeate side of the membrane separation device is >99.9%, and the permeate hydrogen flow rate is >1 m 3 h -1 m -2 , silane concentration on the permeate side < 0.04%.

7. The method according to claim 1, characterized in that 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, and obtaining seed crystals after calcination; (b) The above seed crystals are prepared into a seed crystal suspension, applied to the surface of the carrier, and the carrier is placed in a synthesis solution for hydrothermal synthesis. After calcination to remove the template agent, the SSZ-13 molecular sieve membrane is obtained.

8. The method according to claim 7, characterized in that In step (b), the calcination to remove the template is carried out in an ozone atmosphere, the calcination temperature is 180-250° C., the calcination time is 24-144 hours, and the heating and cooling rates are 0.5-2° C. / min.

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