Method for recovering hydrogen in mixed gas of silane and disilane by using membrane separation method

Abstract

The invention relates to the technical field of gas separation and purification, in particular to a method for recycling hydrogen in silane and disilane mixed gas through a membrane separation method. Comprising the following steps: S1, pretreating mixed gas containing 20%-25% of silane, 10%-15% of disilane and 60%-70% of hydrogen to remove solid particles and moisture; s2, the pretreated mixed gas is introduced into a membrane separation device, silane and disilane are collected on the enrichment side of the membrane separation device for further rectification, and hydrogen is collected on the permeation side of the membrane separation device for further purification. According to the method, hydrogen recovery and silane and disilane enrichment can be efficiently achieved, the hydrogen recovery rate is high, and compared with a traditional separation method, the method is low in energy consumption and has remarkable economic benefits and environmental protection benefits.

Description

Technical Field

[0001] This application relates to the field of gas separation and purification technology, specifically to a method for recovering hydrogen from a mixture of silane and disilane using membrane separation. Background Technology

[0002] In cutting-edge technology fields such as semiconductor manufacturing, photovoltaic material production, and specialty gas preparation, silane (SiH4) and disilane (Si2H6), as important silicon source gases, are commonly used in key processes such as chemical vapor deposition (CVD) and epitaxial growth. Their usage is growing exponentially with the rapid development of the new energy and electronics industries. At the same time, the production process inevitably generates a large amount of mixed gas containing silane, disilane, and hydrogen (H2). Hydrogen is not only the core carrier of the hydrogen energy economy but also an indispensable reducing gas in chemical synthesis, metal smelting, and electronic device manufacturing. Silane and disilane can be recycled and reused in production, significantly reducing raw material costs for enterprises. Therefore, the efficient separation and recovery of the components in this type of mixed gas not only conforms to the concept of a circular economy but also effectively alleviates my country's dependence on imported high-purity gases, which is of great strategic significance for promoting the green and high-quality development of related industries.

[0003] Traditional membrane separation technology faces fundamental challenges in processing mixtures containing silanes, disilanes, and hydrogen, primarily due to the high chemical reactivity, easy decomposition, and sensitivity to impurities of these gases. These challenges include membrane material fouling, reduced separation efficiency, and safety risks. This is because both silanes (SiH4) and disilanes (Si2H6) exhibit extremely high chemical reactivity, with low silicon-hydrogen bond energies in their molecules, leading to easy decomposition, hydrolysis, or oxidation at room temperature. Furthermore, disilane slowly decomposes into silanes and hydrogen at room temperature, with decomposition accelerating under high temperatures or light exposure, further increasing the complexity of the gas mixture. Membrane separation technology relies on the selective permeability of membrane materials for gas separation, but its efficiency is highly dependent on the size and polarity of gas molecules and the compatibility with the membrane material. The small molecular diameters of silanes and disilanes, similar to those of hydrogen molecules, make high-precision sieving difficult with traditional polymer membranes (such as polyimide and polysulfone). Trace amounts of moisture, oxygen, or metal ion impurities that are not completely removed from the gas mixture can trigger chemical reactions between silane and silyl ether. For example, silica particles produced by the hydrolysis of silane can clog membrane pores, and silyl ether can react with organic components in the membrane material to form deposits, leading to irreversible fouling of the membrane pore structure.

[0004] Semiconductor processes require high hydrogen purity, but membrane fouling can cause silane decomposition products to be trapped in the hydrogen, making it difficult to meet the high purity requirements. Therefore, developing an efficient, energy-saving, stable, and reliable hydrogen recovery technology for such mixed gases has become a critical issue that the industry urgently needs to address. Summary of the Invention

[0005] To address the issue of high hydrogen purity requirements in semiconductor processes, but the membrane fouling problem inherent in traditional membrane separation methods, this application provides a method for recovering hydrogen from a mixture of silane and disilane using membrane separation. The technical solution of this application is as follows:

[0006] Includes the following steps:

[0007] Step S1. Pre-treat the mixed gas containing 20%–25% silane, 10%–15% silane, and 60%–70% hydrogen to remove solid particles and moisture;

[0008] Step S2. The pretreated mixed gas is introduced into the membrane separation unit. Silane and silane are collected on the enrichment side of the membrane separation unit for further distillation, and hydrogen is collected on the permeate side of the membrane separation unit for further purification.

[0009] Preferably, the particulate filter element in the pretreatment has a gradient pore size of 0.05 to 0.15 μm.

[0010] Preferably, the membrane separation device includes a separation membrane, which is a modified polyimide-ceramic composite membrane.

[0011] Preferably, the modification method of the modified polyimide-ceramic composite film is to coat it with a fluorinated silane coupling agent with a coating thickness of 0.1-0.5 μm.

[0012] Preferably, the thickness of the separation membrane is 10–50 μm.

[0013] Preferably, the porosity of the separation membrane is 30% to 60%.

[0014] Preferably, the pressure difference for membrane separation is 0.3 to 0.8 MPa.

[0015] Preferably, the hydrogen is further purified by palladium membrane diffusion and molecular sieve adsorption. After molecular sieve adsorption, the regeneration temperature of the molecular sieve is 200-300°C and the regeneration time is 2-4 hours.

[0016] Preferably, the conditions for further distillation of silane and silane are: operating pressure of 0.1 to 0.3 MPa, operating temperature of -100°C to -50°C, and reflux ratio controlled between 2 and 5.

[0017] The beneficial effects of this application are as follows:

[0018] (1) This application adopts membrane separation combined with optimized pretreatment and posttreatment processes, which can efficiently realize the recovery of hydrogen and the enrichment of silane and silane. The hydrogen recovery rate is high and the purity of hydrogen after separation can reach more than 99.99%.

[0019] (2) Through the optimized design of process parameters, this application can operate stably under extreme conditions such as high pressure, low pressure, high temperature and low temperature, and has a wide range of applications.

[0020] (3) Compared with traditional membrane separation methods, this application has low energy consumption and significant economic and environmental benefits. Attached Figure Description

[0021] Appendix Figure 1 This is a process flow diagram of the membrane separation method for recovering hydrogen from a mixture of silane and ethylsilane in this application. Detailed Implementation

[0022] To further illustrate the technical means and effects adopted by this application in order to achieve the intended purpose of the invention, the following detailed description of the specific implementation methods, structures, features and effects of this application is provided in conjunction with the accompanying drawings and preferred embodiments.

[0023] Example 1

[0024] This embodiment provides a method for recovering hydrogen from a mixture of silane and ethylsilane using membrane separation. (See [link to relevant documentation]). Figure 1 The specific steps are as follows:

[0025] Step S1. 100L of a mixed gas containing 20% ​​silane, 15% silane, and 65% hydrogen is introduced into the pretreatment device. The mixed gas first passes through a filter element with a gradient pore size structure, with an inlet pore size of 0.15μm and an outlet pore size of 0.1μm, to remove impurity particles larger than 0.1μm. Then, it passes through a molecular sieve dryer to reduce the moisture content in the mixed gas to below 10ppm, obtaining a preliminarily purified mixed gas.

[0026] Step S2. The preliminarily purified mixed gas is introduced into a membrane separation device at a pressure of 0.5 MPa. The separation membrane in the membrane separation device is a modified polyimide-ceramic composite membrane (the modified layer is coated with perfluorodecyltriethoxysilane, with a coating thickness of 0.3 μm), with a thickness of 20 μm and a porosity of 50%. Under the action of pressure difference, hydrogen permeates through the separation membrane, and hydrogen is collected on the permeate side. Its purity is tested to be above 99%, and the recovery rate is 92%. The silane content in the mixed gas obtained on the retentate side is increased to 30%, and the disilane content is increased to 20%. The hydrogen on the permeate side is introduced into a hydrogen purification unit, further dried by molecular sieve adsorption, and then purified by palladium membrane diffusion to obtain high-purity hydrogen with a purity of 99.999%. The mixed gas on the retentate side enters a distillation column, where it is purified by distillation under the conditions of operating pressure of 0.25 MPa, operating temperature of -60℃, and reflux ratio of 2.8 to obtain a mixed gas of silane and disilane with even higher purity.

[0027] Example 2

[0028] This embodiment provides a method for recovering hydrogen from a mixture of silane and ethylsilane using membrane separation. (See [link to relevant documentation]). Figure 1 The specific steps are as follows:

[0029] Step S1. A 200L mixture containing 22% silane, 12% silane, and 66% hydrogen is introduced into the pretreatment device. The mixture first passes through a filter element with a gradient pore size structure, with an inlet pore size of 0.08μm and an outlet pore size of 0.05μm. A dryer is used to reduce the moisture content to below 5ppm, thus completing the pretreatment.

[0030] Step S2. The pretreated mixed gas is introduced into a membrane separation unit at a pressure of 0.6 MPa. The separation membrane in the membrane separation unit is a modified polyimide-ceramic composite membrane (coated with perfluorodecyltriethoxysilane, coating thickness 0.3 μm), with a thickness of 10 μm and a porosity of 60%. Hydrogen with a purity of 99.1% is obtained on the permeate side, with a recovery rate of 93%. The silane content in the retentate side mixed gas is 32%, and the silane content is 18%. The hydrogen on the permeate side enters the hydrogen purification unit, is first dried in a molecular sieve drying tower, and then diffused and purified by a palladium membrane diffuser to finally obtain high-purity hydrogen with a purity of 99.995%. The retentate side mixed gas enters the distillation column and is purified by distillation under the conditions of operating pressure 0.25 MPa, operating temperature -60℃, and reflux ratio 2.8 to obtain a mixed gas of silane and silane with even higher purity.

[0031] Example 3

[0032] This embodiment provides a method for recovering hydrogen from a mixture of silane and ethylsilane using membrane separation. (See [link to relevant documentation]). Figure 1 The specific steps are as follows:

[0033] Step S1. A 150L mixture containing 23% silane, 13% silane, and 64% hydrogen is introduced into a pretreatment device. In the pretreatment device, the mixture first passes through a filter element with a gradient pore size structure. The filter element has an inlet pore size of 0.15μm and an outlet pore size of 0.05μm, effectively intercepting impurity particles. Subsequently, it enters a molecular sieve dryer to reduce the moisture content to 8ppm.

[0034] Step S2. Next, the pre-purified mixed gas is introduced into a membrane separation device at a pressure of 0.4 MPa. The separation membrane in the device is a modified polyimide-ceramic composite membrane (coated with a modified layer of perfluorodecyltriethoxysilane, with a coating thickness of 0.2 μm). The membrane in this device has a thickness of 30 μm and a porosity of 45%. Driven by the pressure difference, hydrogen permeates through the separation membrane, and hydrogen with a purity of 99.2% is collected on the permeate side, with a recovery rate of 92%. The silane content in the retentate side mixed gas is increased to 35%, and the disilane content is increased to 18%. The hydrogen on the permeate side enters the hydrogen purification unit, is first dried in a molecular sieve drying tower, and then diffused and purified by a palladium membrane diffuser to finally obtain high-purity hydrogen with a purity of 99.995%. The retentate side mixed gas enters a distillation column and is purified by distillation under the conditions of an operating pressure of 0.2 MPa, an operating temperature of -70℃, and a reflux ratio of 3 to obtain a high-purity silane and disilane mixed gas.

[0035] Example 4

[0036] This embodiment provides a method for recovering hydrogen from a mixture of silane and ethylsilane using membrane separation. (See [link to relevant documentation]). Figure 1 The specific steps are as follows:

[0037] Step S1. Select 200L of a mixed gas containing 21% silane, 14% silane, and 65% hydrogen. During the pretreatment process, the mixed gas first passes through a filter element with a gradient pore size structure. The pore size at the inlet end of the filter element is 0.15μm, and the pore size at the outlet end is 0.1μm. Then, it is dried by molecular sieve to reduce the moisture content to 6ppm.

[0038] Step S2. The treated mixed gas is introduced into a membrane separation unit at a pressure of 0.6 MPa. The separation membrane in the membrane separation unit is a modified polyimide-ceramic composite membrane (coated with perfluorodecyltriethoxysilane, coating thickness 0.4 μm). The membrane thickness is 20 μm and the porosity is 50%. Hydrogen is enriched on the permeate side with a purity of 99.1% and a recovery rate of 93%. The silane content on the retentate side is 33%, and the disilane content is 20%. The hydrogen on the permeate side is purified to 99.993% by passing it through a molecular sieve drying tower (regeneration temperature 250℃, regeneration time 3 hours) and a palladium membrane diffuser. The hydrogen purity on the retentate side is 99.993% after purification. The mixed gas on the retentate side is distilled in a distillation column at a pressure of 0.15 MPa, a temperature of -80℃, and a reflux ratio of 4 to obtain high-purity silane and disilane products.

[0039] Example 5

[0040] This embodiment provides a method for recovering hydrogen from a mixture of silane and ethylsilane using membrane separation. (See [link to relevant documentation]). Figure 1 The specific steps are as follows:

[0041] Step S1. For a 180L mixed gas containing 24% silane, 12% silane and 64% hydrogen, in the pretreatment stage, the mixed gas first passes through a filter element with a gradient pore size structure. The pore size at the inlet end of the filter element is 0.15μm and the pore size at the outlet end is 0.05μm. After being dried by molecular sieve, the moisture content is controlled at 7ppm.

[0042] Step S2. The mixed gas is introduced into a membrane separation unit at a pressure of 0.5 MPa. The separation membrane in the membrane separation unit is a modified polyimide-ceramic composite membrane (coated with perfluorodecyltriethoxysilane as the modified layer, with a coating thickness of 0.4 μm), with a membrane thickness of 40 μm and a porosity of 35%. The hydrogen purity on the permeate side reaches 99.3%, and the recovery rate is 92%. The silane content on the cut-off side is increased to 36%, and the disilane content is increased to 16%. The hydrogen on the permeate side is dried in a molecular sieve drying tower and purified by a palladium membrane diffuser to obtain hydrogen with a purity of 99.996%. The mixed gas on the cut-off side is purified by distillation in a distillation column under operating conditions of 0.25 MPa pressure, -60℃ temperature, and reflux ratio of 2.5, achieving efficient purification of silane and disilane.

[0043] Example 6 (High-voltage extreme operating conditions)

[0044] This embodiment provides a method for recovering hydrogen from a mixture of silane and ethylsilane using membrane separation. (See [link to relevant documentation]). Figure 1 The specific steps are as follows:

[0045] Step S1. Take 200L of a mixed gas containing 22% silane, 13% silane, and 65% hydrogen. In the pretreatment stage, the mixed gas first passes through a filter element with a gradient pore size structure. The pore size at the inlet end of the filter element is 0.15μm, and the pore size at the outlet end is 0.05μm to filter impurities. Then, it is dried by molecular sieve to reduce the moisture content to 7ppm.

[0046] Step S2. The treated mixed gas is introduced into a membrane separation device under an ultimate high pressure of 0.8 MPa. The separation membrane in the device is a modified polyimide-ceramic composite membrane (with a modified layer coated with perfluorodecyltriethoxysilane, coating thickness 0.5 μm), with a membrane thickness of 50 μm and a porosity of 40%. Under high pressure differential, hydrogen gas rapidly permeates through the separation membrane, and hydrogen gas with a purity of 99% is collected on the permeate side, with a recovery rate of 90%; the silane content in the mixed gas on the retrieval side increases to 38%, and the diethylsilane content increases to 17%. The permeate-side hydrogen enters the hydrogen purification unit, where it is first dried in a molecular sieve drying tower and then purified by diffusion through a palladium membrane diffuser, ultimately yielding high-purity hydrogen with a purity of 99.992%. The retentate-side mixed gas enters the distillation tower and is purified by distillation under extreme conditions of operating pressure 0.3 MPa, operating temperature -50 °C, and reflux ratio 5. High-purity silane and ethylsilane mixed gas can still be obtained, verifying the reliability of this method under high-pressure conditions.

[0047] Example 7 (Low-pressure extreme operating conditions)

[0048] This embodiment provides a method for recovering hydrogen from a mixture of silane and ethylsilane using membrane separation. (See [link to relevant documentation]). Figure 1 The specific steps are as follows:

[0049] Step S1. Treat 180L of a mixed gas containing 24% silane, 12% silane, and 64% hydrogen. During pretreatment, the mixed gas first passes through a filter element with a gradient pore size structure. The pore size at the inlet end of the filter element is 0.15μm, and the pore size at the outlet end is 0.05μm. After drying with a molecular sieve, the moisture content is controlled at 8ppm.

[0050] Step S2. The mixed gas is introduced into a membrane separation device at a low pressure of 0.3 MPa. The separation membrane in the device is a modified polyimide-ceramic composite membrane (coated with perfluorodecyltriethoxysilane, with a coating thickness of 0.1 μm), and the membrane thickness is 15 μm with a porosity of 60%. Despite the low pressure, hydrogen gas still effectively permeates through the separation membrane, achieving a purity of 99.1% on the permeate side and a recovery rate of 91%; the silane content on the retentate side increases to 37%, and the disilane content increases to 16%. The hydrogen gas on the permeate side is dried in a molecular sieve drying tower and purified by a palladium membrane diffuser to obtain hydrogen gas with a purity of 99.99%; the mixed gas on the retentate side is purified by distillation in a distillation column at a low pressure of 0.1 MPa, a temperature of -100℃, and a reflux ratio of 2, successfully achieving efficient separation and purification of silane and disilane, indicating that this technology still has good applicability under extreme low-pressure conditions.

[0051] Example 8 (High Temperature Extreme Conditions)

[0052] This embodiment provides a method for recovering hydrogen from a mixture of silane and ethylsilane using membrane separation. (See [link to relevant documentation]). Figure 1 The specific steps are as follows:

[0053] Step S1. Select 150L of a mixed gas containing 23% silane, 14% silane, and 63% hydrogen. The initial temperature of the mixed gas is relatively high, close to 80℃. In the pretreatment stage, impurities are first filtered through a filter with a cooling function. The filter element has an inlet pore size of 0.15μm and an outlet pore size of 0.05μm. Then, the gas enters a high-temperature resistant molecular sieve dryer to reduce the moisture content to 6ppm, while simultaneously reducing the gas temperature to a suitable range.

[0054] Step S2. The treated mixed gas is introduced into a membrane separation device at a pressure of 0.5 MPa. The separation membrane in the device is a modified polyimide-ceramic composite membrane (with a modified layer coated with perfluorodecyltriethoxysilane, coating thickness 0.3 μm), with a membrane thickness of 35 μm and a porosity of 30%, capable of maintaining stable performance at high temperatures. Under the action of pressure difference, the purity of hydrogen on the permeate side reaches 99.1%, and the recovery rate is 91%; the silane content on the cut-off side increases to 36%, and the ethylsilane content increases to 18%. The permeate-side hydrogen is processed by a specially designed high-temperature resistant hydrogen purification unit, including a high-temperature resistant molecular sieve drying tower and a palladium membrane diffuser, ultimately yielding high-purity hydrogen with a purity of 99.994%. The retentate-side mixed gas enters a distillation column equipped with special heat-insulating materials and high-temperature resistant components, where it undergoes distillation purification under operating conditions of 0.25 MPa, -60℃ (the internal temperature of the distillation column needs special control due to the influence of external high temperatures), and a reflux ratio of 2.8. This achieves hydrogen recovery and effective separation of silane and diethylsilane under extreme high-temperature conditions.

[0055] Example 9 (Extreme Low Temperature Conditions)

[0056] This embodiment provides a method for recovering hydrogen from a mixture of silane and ethylsilane using membrane separation. (See [link to relevant documentation]). Figure 1 The specific steps are as follows:

[0057] Step S1. For a 200L mixture containing 21% silane, 15% disilane, and 64% hydrogen, in an environment with a temperature as low as -30°C, the mixture is pretreated by passing it through a filter with a preheating function. The filter uses a filter element with a gradient pore size structure; the inlet pore size is 0.15μm, and the outlet pore size is 0.05μm. The mixture then passes through a preheated molecular sieve dryer to reduce the moisture content to 7ppm, while simultaneously preventing gas condensation due to the low temperature.

[0058] Step S2. The treated mixed gas is introduced into a membrane separation unit at a pressure of 0.4 MPa. The separation membrane in the membrane separation unit is a modified polyimide-ceramic composite membrane (with a modified layer coated with perfluorodecyltriethoxysilane, coating thickness 0.2 μm), with a thickness of 25 μm and a porosity of 48%, maintaining good flexibility and separation performance at low temperatures. Under pressure differential drive, the hydrogen purity on the permeate side reaches 99.2%, and the recovery rate is 90%; the silane content on the cut-off side increases to 34%, and the diethylsilane content increases to 20%. Hydrogen on the permeate side enters a hydrogen purification unit equipped with a low-temperature protection and heating system. After purification by a molecular sieve drying tower and a palladium membrane diffuser, hydrogen with a purity of 99.995% is obtained. The mixed gas on the retrieval side enters a distillation column with antifreeze protection and a low-temperature high-efficiency separation structure. Distillation and purification are carried out under extreme low-temperature conditions of 0.15 MPa pressure, -100℃ (the distillation column adopts special low-temperature refrigeration and insulation technology), and a reflux ratio of 3.2, achieving effective separation and purification of hydrogen from silane and disilane in a harsh low-temperature environment.

[0059] The above description is merely a preferred embodiment of this application and is not intended to limit this application in any way. Although this application has been disclosed above with reference to preferred embodiments, it is not intended to limit this application. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the technical solution of this application. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. A method for recovering hydrogen from a mixture of silane and disilane by membrane fractionation, characterized in that, The method comprises the following steps: Step S1. Pre-treat the mixed gas containing 20-25% silane, 10-15% disilane and 60-70% hydrogen to remove solid particles and moisture; Step S2. Pass the pre-treated mixed gas into a membrane separation device, collect silane and disilane at the enrichment side of the membrane separation device for further rectification, and collect hydrogen at the permeation side of the membrane separation device for further purification.

2. The method for recovering hydrogen from a mixture of silane and disilane according to claim 1, wherein The pore size of the filter core in the pre-treatment is 0.05-0.15 μm.

3. The method for recovering hydrogen from a mixture of silane and disilane according to claim 1, wherein The membrane separation device is provided with a separation membrane, which is a modified polyimide-ceramic composite membrane.

4. The method for recovering hydrogen from a mixture of silane and disilane according to claim 3, wherein The modification method of the modified polyimide-ceramic composite membrane is to coat a fluorine-containing silane coupling agent with a coating thickness of 0.1-0.5 μm.

5. The method of claim 3, wherein the method is characterized by, The thickness of the separation membrane is 10-50 μm.

6. The method of claim 3, wherein the method is characterized by, The porosity of the separation membrane is 30-60%.

7. The method for recovering hydrogen from a mixture of silane and disilane according to claim 1, wherein The pressure difference of the membrane separation is 0.3-0.8 MPa.

8. The method for recovering hydrogen from a mixture of silane and disilane according to claim 1, wherein The further purification of the hydrogen is performed by palladium membrane diffusion and molecular sieve adsorption, and after the molecular sieve adsorption, the regeneration temperature of the molecular sieve is 200-300 °C and the regeneration time is 2-4 hours.

9. The method for recovering hydrogen from a mixture of silane and disilane according to claim 1, wherein The further rectification of the silane and disilane is performed under the following conditions: the operation pressure is 0.1-0.3 MPa, the operation temperature is -100 °C to -50 °C, and the reflux ratio is controlled between 2 and 5.

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