Membrane separation method for recovery of purge gas from organic alcohol synthesis

Abstract

The present invention discloses a membrane separation method for recovering purge gas from organic alcohol synthesis, relating to the technical field of hydrogen recovery in hydrogen-rich gas systems. The method comprises: using a gas separation composite membrane comprising a porous support and a hybrid membrane layer formed on the surface of the porous support, formed by mixing a polymer phase with gas separation properties with a functional inorganic oxide phase; the gas separation composite membrane exhibits an H2 / N2 separation factor greater than 28 and an H2 / CO2 separation factor greater than 5.5. The membrane separation method for recovering purge gas from organic alcohol synthesis provided by the present invention has superior gas separation performance, higher hydrogen recovery efficiency, better economic benefits, and broad application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrogen recovery in hydrogen-rich systems, and particularly relates to a membrane separation method for recovering purge gas from organic alcohol synthesis. Background Art

[0002] The theoretical carbon ratio (H2 / C) of synthetic methanol is 2. The high hydrogen content and low carbon content are the inherent defects of the conversion method of coke oven gas to methanol. 3 Coke oven gas produces about 0.28m 3 The composition of relaxation gas contains H2, CO, CO2, CH4, and N2. In industrial production, relaxation gas is mostly released or burned with a torch, which causes environmental pollution. Relaxation gas is also used as boiler fuel gas, but because of the low calorific value of relaxation gas, the operation is unsafe.

[0003] Currently, the commonly used purge gas recovery technologies include pressure swing adsorption separation and membrane separation. Pressure swing adsorption separation is a gas separation technology that utilizes the different adsorption capacities of different components in the gas medium on the adsorbent. The adsorbent selectively adsorbs when the pressure increases and is desorbed and regenerated when the pressure decreases. Each set of pressure swing adsorption equipment consists of at least two towers. Each tower completes an adsorption-regeneration cycle through the steps of adsorption, equalization of pressure drop, flushing / vacuuming, equalization of pressure rise, and final rise. At any given time, one or more towers are in an adsorption state. When the gas passes through the adsorption bed, the adsorbed gas is adsorbed in the bed, while other non-adsorbed gases pass through the bed and are enriched and purified from the top of the tower; in the regeneration stage, the adsorbed gas is obtained from the bottom of the tower as desorbed gas.

[0004] Membrane separation is another effective method for gas separation. Its operating principle is to use a polymer membrane to selectively "filter" the feed gas to achieve separation. When a mixture of two or more gases passes through the polymer membrane, the differences in the solubility and diffusion coefficients of the gas components in the polymer result in different permeation rates through the membrane wall. Characteristics of membrane separation of methanol purge gas include: high permeate gas pressure loss, with a minimum pressure drop of 2 MPa; low recovery rates for single-stage membranes, reaching only around 80% at most; the use of multi-stage membranes can improve recovery rates; the permeate gas contains active gas components such as H₂, CO, and CO₂; and a water scrubber is required to recover CH₃OH before entering the membrane separation system. Due to the high permeate gas pressure loss, a compressor is required to increase the pressure of the permeate gas to return it to the synthesis system. This method wastes 5-15 MPa of head pressure energy of the non-permeate gas and increases electrical energy consumption. Therefore, traditional membrane separation processes for separating methanol purge gas are not optimal from an energy utilization perspective. Summary of the Invention

[0005] The present invention aims to provide a membrane separation method for recovering purge gas from organic alcohol synthesis, which has a more excellent gas separation effect, a higher hydrogen recovery efficiency, better economic benefits and broad application prospects.

[0006] The technical solutions adopted by the present invention to achieve the above-mentioned purpose are:

[0007] A gas separation composite membrane comprising a porous support and a hybrid membrane layer formed on the surface of the porous support and formed by mixing a polymer phase having gas separation properties with a functional inorganic oxide phase; the gas separation composite membrane has an H2 / N2 separation factor greater than 28 and an H2 / CO2 separation factor greater than 5.5;

[0008] The polymer phase comprises an imide structure formed by the reaction of an aromatic anhydride and an aromatic diamine; the functional inorganic oxide phase comprises inorganic silicon. The present invention utilizes polyimide as an organic matrix, introduces an inorganic silicon phase, and synthesizes a coating solution using a sol-gel method, which is then coated onto a supporting substrate to form a membrane. The membrane is then thermally imidized to form an organic-inorganic hybrid membrane. The resulting composite gas separation membrane exhibits excellent gas separation performance and can be applied to organic alcohol synthesis purge gas recovery systems, effectively improving hydrogen recovery efficiency and offering superior economic benefits. It holds broad application prospects.

[0009] For purposes of the present invention, aromatic anhydrides include pyromellitic dianhydride.

[0010] For the purposes of the present invention, the aromatic diamine includes at least one of 2,2'-diaminoethylene glycol diphenyl ether and 2,4-diamino-5-hydroxymethyl pyrimidine. In the preparation process of the gas separation composite membrane of the present invention, 2,2'-diaminoethylene glycol diphenyl ether and / or 2,4-diamino-5-hydroxymethyl pyrimidine are used as one of the polymerization monomers and compounded with other components. The resulting composite membrane has superior gas separation performance, with significantly improved H2 / N2 and H2 / CO2 separation factors. Furthermore, the mechanical properties of the prepared hybrid membrane are significantly improved, with significantly increased tensile strength and elongation at break. This may be because the addition of 2,2'-diaminoethylene glycol diphenyl ether and / or 2,4-diamino-5-hydroxymethyl pyrimidine has a beneficial effect on the polymer structure, further increasing the rigidity of the hybridized molecular chain and significantly improving gas selectivity. At the same time, a more regular pore structure is formed, which is more conducive to the permeation of hydrogen. Furthermore, the resulting polymer network structure is more stable, with improved mechanical properties. The prepared gas separation composite membrane was applied to the organic alcohol synthesis relaxation gas recovery system, which significantly improved the hydrogen recovery rate.

[0011] More preferably, the H2 / N2 separation factor of the gas separation composite membrane is greater than 30, and the H2 / CO2 separation factor is greater than or equal to 7.2.

[0012] For the purposes of the present invention, the porous support includes an alumina ceramic support.

[0013] Another object of the present invention is to disclose the use of the above-mentioned gas separation composite membrane as a separation membrane for recovering purge gas from organic alcohol synthesis.

[0014] The present invention also discloses a method for preparing the gas separation composite membrane, which comprises the steps of: heating a hybrid membrane composed of a polyimide polymer and inorganic silicon in a non-oxidizing atmosphere to obtain the membrane.

[0015] In the present invention, the polyimide polymer is obtained by polymerizing an aromatic acid anhydride and an aromatic diamine.

[0016] Furthermore, a method for preparing a gas separation composite membrane comprises:

[0017] Under nitrogen protection, 2,2'-diaminoethylene glycol diphenyl ether was dissolved in DMAc, and 2,4-diamino-5-hydroxymethylpyrimidine and PMDA were added in sequence. The mixture was reacted in an ice-water bath for 4 to 8 hours to obtain solution A. Ethyl orthosilicate and deionized water were mixed and stirred in a molar ratio of 1:3.5 to 4.5, and then added to solution A. The mixture was stirred at room temperature overnight to obtain a coating solution.

[0018] The prepared coating liquid was coated on the zirconium sol-modified α-Al2O3 ceramic support by the immersion pulling method, dried at room temperature for 24 hours, and then thermally imidized at 300-400°C in a nitrogen atmosphere to obtain a gas separation composite membrane.

[0019] In the present invention, the molar ratio of 2,2'-diaminoethylene glycol diphenyl ether, 2,4-diamino-5-hydroxymethylpyrimidine, and PMDA is 1:0.2-0.4:1.2-1.4; the solid-liquid ratio of 2,2'-diaminoethylene glycol diphenyl ether to DMAc is 0.04-0.06 g:1 mL.

[0020] For the present invention, the amount of inorganic silicon (SiO2) introduced into solution A is 12 to 16 wt%.

[0021] In the present invention, the molecular weight of the polyimide polymer is 200,000 to 500,000.

[0022] In the present invention, the coating liquid is applied 2 to 4 times; and the thickness of the obtained coating film is 0.5 to 8 μm.

[0023] More preferably, during the preparation process of the gas separation composite membrane, an epoxy-containing silane coupling agent is further added, which is mixed evenly with tetraethyl orthosilicate and deionized water and then added to solution A. The present invention adds an epoxy-containing silane coupling agent modified by 4-(oxiranyl methoxy) benzene acetamide during the preparation process of the gas separation composite membrane, further enhancing the performance of the composite membrane, further improving its gas separation performance, and significantly enhancing the thermal stability of the hybrid membrane, and further improving the mechanical properties. The reason may be that the addition of the epoxy-containing silane coupling agent modified by 4-(oxiranyl methoxy) benzene acetamide can further improve the polyimide and silicon dioxide interface effect in the composite membrane structure, making the two more closely combined, and significantly increasing the mechanical properties of the composite membrane obtained; while playing the role of strengthening the material structure, further improving the heat resistance stability of the hybrid membrane, and the composite membrane is also significantly improved in terms of gas separation ability. The obtained gas separation composite membrane is applied to an organic alcohol synthesis purge gas recovery system, significantly improving the recovery rate of hydrogen.

[0024] In the present invention, the molar ratio of the epoxy-containing silane coupling agent to the inorganic silicon in solution A is 1 to 1.2:1.

[0025] Furthermore, the chemical structure of the epoxy-containing silane coupling agent is shown in Formula I:

[0026]

[0027] In the present invention, the preparation method of the chemical structure shown in Formula I comprises:

[0028] Mix chloromethyltrimethoxysilane and triethylamine, slowly add 4-(oxiranylmethoxy)phenylacetamide, heat under reflux for 4-6 hours, filter and purify by vacuum distillation to obtain the compound; pay attention to nitrogen protection and strict waterproofing during the entire reaction process.

[0029] Preferably, the molar ratio of chloromethyltrimethoxysilane to triethylamine is 1:0.95-1.05; the molar ratio of 4-(oxiranylmethoxy)phenylacetamide to chloromethyltrimethoxysilane is 0.9-1.1:1.

[0030] A membrane separation method for recovering organic alcohol purge gas uses the above-mentioned gas separation composite membrane.

[0031] Specifically, the membrane separation method for recovering the organic alcohol purge gas comprises:

[0032] Step S1: Pretreatment: The organic alcohol relaxation gas at 4.5-5.5 MPa is first passed into a water scrubber and washed with high-pressure desalted water to remove methanol; then passed into a gas-liquid separator to remove liquid entrained in the gas, and then passed into a heater to be heated to 50-55°C;

[0033] Step S2: membrane separation, the heated gas is passed through 3 to 5 parallel membrane separator groups for separation, and the non-permeate gas is decompressed to 0.4 to 0.5 MPa and merged into the fuel gas network;

[0034] Step S3: Hydrogen compression: The hydrogen-rich permeate gas passing through the membrane separator group is passed into a hydrogen compressor for compression as needed. When the pressure of the gas at the hydrogen compressor outlet exceeds the pressure of the synthesis system, the hydrogen-rich gas is incorporated into the synthesis system, i.e., the methanol unit. The membrane separation method for recovering organic alcohol purge gas provided by the present invention has superior hydrogen recovery performance, effectively utilizes the purge gas, avoids environmental pollution caused by the release or combustion of the purge gas, and increases enterprise profitability.

[0035] In the present invention, during the pretreatment process, the heater heating method includes: heating the gas with 1.2-1.4 MPa steam.

[0036] In the present invention, during the membrane separation process, an appropriate pressure difference is selected on both sides of the membrane. Driven by the partial pressure difference, the "fast gas" selectively and preferentially permeates the membrane separator and is guided out of the membrane separation system as permeate gas.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The present invention utilizes 2,2'-diaminoethylene glycol diphenyl ether and / or 2,4-diamino-5-hydroxymethylpyrimidine as one of the polymerization monomers during the preparation of a gas separation composite membrane. The resulting composite membrane exhibits superior gas separation performance. Furthermore, the mechanical properties of the resulting hybrid membrane are significantly improved, with significant increases in tensile strength and elongation at break. The resulting gas separation composite membrane is applied to an organic alcohol synthesis purge gas recovery system, significantly improving the hydrogen recovery rate. Furthermore, the present invention incorporates an epoxy-containing silane coupling agent modified with 4-(oxiranylmethoxy)phenylacetamide during the preparation of the gas separation composite membrane, further enhancing the performance of the composite membrane. The hybrid membrane also exhibits significantly enhanced thermal stability and improved mechanical properties. The gas separation composite membrane prepared using the present invention is used to recover and process organic alcohol synthesis purge gas, resulting in superior hydrogen recovery rates, effective purge gas utilization, and the avoidance of environmental pollution caused by purge gas release or combustion, while also increasing business profitability.

[0039] Therefore, the present invention provides a membrane separation method for recovering organic alcohol synthesis purge gas, which has a more excellent gas separation effect, a higher hydrogen recovery efficiency, better economic benefits, and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 IR spectrum of the gas separation composite membrane prepared in Example 1 of the present invention;

[0041] Figure 2 IR spectrum of the gas separation composite membrane prepared in Example 5 of the present invention;

[0042] Figure 3 These are the thermogravimetric analysis curves of the gas separation composite membranes prepared in Example 5 and Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0043] The technical solution of the present invention is further described in detail below with reference to the specific embodiments and the accompanying drawings:

[0044] The α-Al 2 O 3 ceramic support used in the embodiment of the present invention is commercially available and has a porosity of 48.6%.

[0045] Example 1:

[0046] Preparation of a gas separation composite membrane:

[0047] Under nitrogen protection, 2,2'-diaminoethylene glycol diphenyl ether was dissolved in DMAc at a solid-liquid ratio of 0.05 g:1 mL, and 2,4-diamino-5-hydroxymethylpyrimidine and PMDA (the molar ratio of 2,2'-diaminoethylene glycol diphenyl ether, 2,4-diamino-5-hydroxymethylpyrimidine, and PMDA was 1:0.28:1.3) were added in sequence. The mixture was reacted in an ice-water bath for 6 hours to obtain solution A; ethyl orthosilicate and deionized water were mixed and stirred at a molar ratio of 1:4, and then added to solution A, wherein the amount of inorganic silicon (SiO2) introduced was 13.6 wt%, and stirred at room temperature overnight to obtain a coating solution;

[0048] The prepared coating liquid was coated on the zirconium sol-modified α-Al2O3 ceramic support by the immersion pulling method, dried at room temperature for 24 hours, and then thermally imidized at 360°C in a nitrogen atmosphere to obtain a gas separation composite membrane (wherein the coating thickness is 4 μm).

[0049] Example 2:

[0050] A method for preparing a gas separation composite membrane is different from that of Example 1:

[0051] The molar ratio of 2,2'-diaminoethylene glycol diphenyl ether, 2,4-diamino-5-hydroxymethylpyrimidine, and PMDA is 1:0.2:1.2; and the amount of inorganic silicon (SiO2) introduced into solution A is 12.2 wt%.

[0052] Example 3:

[0053] A method for preparing a gas separation composite membrane is different from that of Example 1:

[0054] The molar ratio of 2,2'-diaminoethylene glycol diphenyl ether, 2,4-diamino-5-hydroxymethylpyrimidine, and PMDA is 1:0.4:1.38; the amount of inorganic silicon (SiO2) introduced into solution A is 16 wt%.

[0055] Example 4:

[0056] A method for preparing a gas separation composite membrane is different from that of Example 1:

[0057] The molar ratio of 2,2'-diaminoethylene glycol diphenyl ether, 2,4-diamino-5-hydroxymethylpyrimidine, and PMDA is 1:0.32:1.36; and the amount of inorganic silicon (SiO2) introduced into solution A is 15 wt%.

[0058] Example 5:

[0059] A method for preparing a gas separation composite membrane is different from that of Example 1:

[0060] During the preparation process, an epoxy-containing silane coupling agent is also added, which is mixed evenly with ethyl orthosilicate and deionized water before being added to solution A. The molar ratio of the epoxy-containing silane coupling agent to the inorganic silicon in solution A is 1.1:1.

[0061] Preparation of the above-mentioned epoxy-containing silane coupling agent:

[0062] Mix chloromethyltrimethoxysilane and triethylamine (the molar ratio of the two is 1:1.05), slowly add 4-(oxiranylmethoxy)phenylacetamide (the molar ratio of chloromethyltrimethoxysilane is 0.95:1), heat and reflux for 6 hours, filter and purify by vacuum distillation to obtain the compound; pay attention to nitrogen protection and strict waterproofing during the entire reaction process.

[0063]

[0064] 1 H NMR (400MHz, DMSO): 7.93 (1H, NH), 7.51, 6.94 (d, 4H, Ph-H), 4.29, 4.08 (m, 2H, -CH2), 3.92 (s, 2H, Ph-CH2), 3.45 (s, 9H, Si-O-CH3), 2.97 (m, 1H, -CH), 2.52 (s, 2H, Si-CH2), 2.64, 2.32 (m, 2H, -CH2).

[0065] Example 6:

[0066] A method for preparing a gas separation composite membrane is different from that of Example 1:

[0067] 2,2'-Diaminoethylene glycol diphenyl ether was used instead of 2,4-diamino-5-hydroxymethylpyrimidine.

[0068] Example 7:

[0069] A method for preparing a gas separation composite membrane is different from that of Example 1:

[0070] 2,4-Diamino-5-hydroxymethylpyrimidine was used instead of 2,2'-diaminoethylene glycol diphenyl ether.

[0071] Example 8:

[0072] A membrane separation method for recovering organic alcohol purge gas comprises:

[0073] Step S1: Pretreatment: The 4.8MPa organic alcohol relaxation gas is first passed into a water scrubber and washed with high-pressure desalted water to remove methanol; then passed into a gas-liquid separator to remove liquid entrained in the gas, and then passed into a heater to heat the gas to 55°C with 1.3MPa steam;

[0074] Step S2: Membrane separation, the heated gas is introduced (flow rate is 9860m 3 / h) 4 membrane separator groups connected in parallel (separation membranes are prepared as in Example 1), with an appropriate pressure difference (0.8 MPa) selected across the membranes for separation, and the non-permeate gas is decompressed to 0.48 MPa and incorporated into the fuel gas network;

[0075] Step S3: hydrogen compression, the hydrogen-rich permeate gas passing through the membrane separator group is passed into the hydrogen compressor for compression as needed. When the pressure of the gas at the outlet of the hydrogen compressor is greater than the pressure of the synthesis system, the hydrogen-rich gas is introduced into the synthesis system, i.e., the methanol unit.

[0076] Example 9:

[0077] The membrane separation method for recovering the organic alcohol purge gas is different from that in Example 8:

[0078] The separation membrane was prepared in Example 5.

[0079] Example 10:

[0080] The membrane separation method for recovering the organic alcohol purge gas is different from that in Example 8:

[0081] The separation membrane was prepared in Example 6.

[0082] Example 11:

[0083] The membrane separation method for recovering the organic alcohol purge gas is different from that in Example 8:

[0084] The separation membrane was prepared in Example 7.

[0085] Comparative Example 1:

[0086] A method for preparing a gas separation composite membrane is different from that of Example 6:

[0087] 4,4'-diaminodiphenyl ether was used instead of 2,2'-diaminoethylene glycol diphenyl ether.

[0088] Comparative Example 2:

[0089] A method for preparing a gas separation composite membrane is different from that of Example 5:

[0090] Silane coupling agent KH560 is used to replace epoxy-containing silane coupling agents.

[0091] Comparative Example 3:

[0092] The membrane separation method for recovering the organic alcohol purge gas is different from that in Example 8:

[0093] The separation membrane was prepared in Comparative Example 1.

[0094] Comparative Example 4:

[0095] The membrane separation method for recovering the organic alcohol purge gas is different from that in Example 8:

[0096] The separation membrane was prepared in Comparative Example 2.

[0097] Test Example 1:

[0098] Infrared characterization

[0099] The samples were tested using the potassium bromide pellet method and Fourier transform infrared spectrometer. The test conditions were as follows: scanning wavelength 400-4000cm -1 .

[0100] The film samples prepared in Example 1 were tested as above, and the results were as follows: Figure 1 As shown in the figure, we can see that at 1719cm -1 The characteristic absorption peak of the C=O bond in the carboxyl group appears near 1678 cm -1 The characteristic absorption peak of amide I band appears near 1537cm -1 The characteristic absorption peak of amide II band appears near 1245cm -1 The characteristic absorption peak of amide III band appears near 1090cm -1 、951cm -1 The characteristic absorption peaks of silanol and silanol appeared near the surface, indicating the presence of silica particles; at 1500 cm -1 The characteristic absorption peak of benzene ring appears near 1146cm -1 The characteristic absorption peak of ether bond appears near 1572cm-1 、988cm -1 、787cm -1 The above results indicate that the gas separation composite membrane in Example 1 was successfully prepared.

[0101] The film samples prepared in Example 5 were tested as above, and the results were as follows: Figure 2 As shown in the figure, the intensity of the characteristic absorption peak of the amide group changes, and the peak at 910 cm -1 No characteristic absorption peak of epoxy appeared nearby, indicating that a ring-opening reaction occurred. The gas separation composite membrane prepared in Example 5 was successfully prepared.

[0102] TGA characterization

[0103] The analytes were performed using a TA Instrument TGA-2950 from the United States. The temperature was raised from room temperature to 800°C at a heating rate of 20°C / min under a nitrogen atmosphere.

[0104] The hybrid membranes obtained in Comparative Example 2 and Example 5 were tested as above. The results are as follows: Figure 3 As shown in the figure, it can be seen that the thermal decomposition temperature of the gas separation composite membrane prepared in Example 5 is significantly higher than that in Comparative Example 2, indicating that the addition of 4-(oxiranylmethoxy)phenylacetamide-modified silane coupling agent to the membrane system enhances the thermal stability of the gas separation composite membrane.

[0105] Test Example 2:

[0106] Mechanical properties testing

[0107] The test was conducted using an electronic universal tensile testing machine to measure the mechanical properties of the membrane samples at room temperature. During the experiment, the tensile speed was 5 mm / min.

[0108] The above tests were performed on the hybrid membranes prepared in Comparative Examples 1 to 2 and Examples 1 to 7. The results are shown in Table 1:

[0109] Table 1 Mechanical properties test results

[0110]

[0111] From the data analysis in Table 1, it can be seen that the tensile strength of the gas separation composite membrane prepared in Example 1 of the present invention is significantly higher than that of Examples 6 and 7, and the effects of Examples 6 and 7 are better than those of Comparative Example 1. This shows that using 2,2'-diaminoethylene glycol diphenyl ether and / or 2,4-diamino-5-hydroxymethyl pyrimidine as polymerization monomers and compounding with other components can effectively improve the network structure of the gas separation composite membrane and enhance its tensile strength. In addition, under the condition of the simultaneous presence of 2,2'-diaminoethylene glycol diphenyl ether and 2,4-diamino-5-hydroxymethyl pyrimidine, the synergistic compounding has a better effect on enhancing the gas tensile strength of the gas separation composite membrane. The effect of Example 5 is better than that of Example 1 and Comparative Example 2, indicating that the addition of 4-(oxiranylmethoxy)phenylacetamide modified silane coupling agent during the preparation of the gas separation composite membrane can play a role in enhancing the tensile properties of the membrane. The reason may be that the presence of 4-(epoxyethylmethoxy)phenylacetamide modified silane coupling agent has a better improvement effect on the interaction between polyimide and silica in the membrane structure.

[0112] At the same time, the elongation at break of the gas separation composite membrane prepared in Example 1 of the present invention was significantly higher than that in Example 7 and comparable to that in Example 6. Furthermore, Example 6 was superior to Comparative Example 1, and the effect of Example 7 was comparable to that of Comparative Example 1. This indicates that the use of 2,2'-diaminoethylene glycol diphenyl ether as a polymerization monomer, in combination with other components, can effectively improve the network structure of the gas separation composite membrane and enhance its elongation at break, while 2,4-diamino-5-hydroxymethylpyrimidine has no negative effect on the elongation at break performance of the composite membrane. The effect of Example 5 was superior to that of Example 1 and Comparative Example 2, indicating that the addition of a 4-(oxiranylmethoxy)phenylacetamide-modified silane coupling agent during the preparation of the gas separation composite membrane can enhance the membrane's elongation at break.

[0113] Gas permeability test

[0114] The gas separation composite membrane sample was placed in the membrane assembly, and then single component (H2, CO2, N2) gas permeation was performed one by one. Based on the test data, the separation coefficients of H2 / N2 and H2 / CO2 were calculated respectively. The gas permeation rate calculation formula is as follows:

[0115] J=Q / (△P×A×V)

[0116] Where Q represents the volume flow rate, mL / s; △P represents the osmotic pressure difference, Pa; A represents the effective membrane area, m 2 ; V represents the molar volume of the gas, mL / mol.

[0117] The separation factor calculation formula is as follows:

[0118] Separation factor = P A / PB

[0119] Where, P A represents the permeation rate of component A; P B Represents the permeation rate of component B.

[0120] The above test was performed on the gas separation composite membranes prepared in Comparative Examples 1-2 and Examples 1-7. The results are shown in Table 2:

[0121] Table 2 Gas separation performance test results

[0122]

[0123] From the data analysis in Table 2, it can be seen that the H2 / N2 and H2 / CO2 separation factors of the gas separation composite membrane prepared in Example 1 of the present invention are significantly higher than those of Examples 6 and 7, and the effects of Examples 6 and 7 are better than those of Comparative Example 1, indicating that the use of 2,2'-diaminoethylene glycol diphenyl ether and / or 2,4-diamino-5-hydroxymethyl pyrimidine as polymerization monomers and compounding with other components can effectively improve the network structure of the gas separation composite membrane and enhance its separation performance; and under the condition of the simultaneous presence of 2,2'-diaminoethylene glycol diphenyl ether and 2,4-diamino-5-hydroxymethyl pyrimidine, the synergistic compounding has a better effect on enhancing the gas separation capacity of the gas separation composite membrane. The effect of Example 5 is better than that of Example 1 and Comparative Example 2, indicating that the addition of 4-(oxiranylmethoxy)phenylacetamide modified silane coupling agent during the preparation of the gas separation composite membrane can enhance the membrane separation performance.

[0124] Test Example 3:

[0125] The test results of hydrogen content in the permeate gas are shown in Table 3:

[0126] Table 3 Test results of hydrogen content in permeate gas

[0127]

[0128] From the data analysis in Table 3, it can be seen that after treatment with the membrane separation method, the hydrogen content in the permeate of Example 8 is significantly higher than that of Examples 10 and 11, and the effects of Examples 10 and 11 are better than those of Comparative Example 3. This shows that using 2,2'-diaminoethylene glycol diphenyl ether and / or 2,4-diamino-5-hydroxymethyl pyrimidine as polymerization monomers and compounding with other components to prepare a gas separation composite membrane for the recovery of organic alcohol synthesis purge gas can significantly improve the hydrogen recovery rate; and under the condition of the simultaneous presence of 2,2'-diaminoethylene glycol diphenyl ether and 2,4-diamino-5-hydroxymethyl pyrimidine, the synergistic compounding has a better effect on hydrogen recovery. The effect of Example 9 is better than that of Example 8 and Comparative Example 4, indicating that the addition of a 4-(oxiranylmethoxy)phenylacetamide-modified silane coupling agent during the preparation of the gas separation composite membrane can enhance the hydrogen recovery effect of the recovery method.

[0129] The conventional techniques in the above embodiments are prior arts known to those skilled in the art, and thus will not be described in detail here.

[0130] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A gas separation composite membrane comprising a porous support and a hybrid membrane layer formed on the surface of the porous support and comprising a polymer phase having gas separation properties and a functional inorganic oxide phase; the gas separation composite membrane exhibits an H2 / N2 separation factor greater than 28 and an H2 / CO2 separation factor greater than 5.5; The polymer phase comprises an imide structure formed by the reaction of an aromatic anhydride and an aromatic diamine; the functional inorganic oxide phase comprises inorganic silicon; The aromatic anhydride includes pyromellitic dianhydride; The aromatic diamine includes at least one of 2,2'-diaminoethylene glycol diphenyl ether and 2,4-diamino-5-hydroxymethylpyrimidine; The thickness of the gas separation composite membrane is 0.5-8 μm.

2. Use of the gas separation composite membrane according to claim 1 as a separation membrane for recovering purge gas from organic alcohol synthesis.

3. The method for preparing the gas separation composite membrane according to claim 1, comprising: It is obtained by heating a hybrid film composed of a polyimide polymer and inorganic silicon in a non-oxidizing atmosphere.

4. The method for preparing a gas separation composite membrane according to claim 3, wherein: The polyimide polymer is obtained by polymerizing an aromatic acid anhydride and an aromatic diamine.

5. The method for preparing a gas separation composite membrane according to claim 3, wherein: The molecular weight of the polyimide polymer is 200,000 to 500,000.

6. A membrane separation method for recovering organic alcohol purge gas, which uses the gas separation composite membrane according to claim 1.

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