Carbon films prepared from hydroquinone and their manufacturing method

Abstract

The present invention relates to a method for producing carbon membranes supported on ceramic supports. The present invention also relates to carbon membranes prepared from hydroquinone on ceramic tubular supports and the use of such membranes. The present invention focuses on the preparation of carbon membranes for gas separation from hydroquinone oligomers as thermosetting precursors. In one example, chemical post-treatment of the membranes is used to increase H2 / CO2, H2 / N2 and CO2 / N2 selectivities.

Description

[Technical field]

[0001] The present invention relates to a method for producing carbon membranes supported on a ceramic support and used in the separation of gases. [Background technology]

[0002] In recent years, researchers have been trying to develop membrane separation technology that can provide higher purity and less energy consumption compared to traditional methods such as cryogenic distillation and pressure swing absorption. With membrane technology, high purity H2 can be achieved, while CO2 is available at high purity for CCS or CCU. Incorporation of membranes into the reactor can shift the equilibrium limiting reaction so as to increase the efficiency of the process.

[0003] The need for CO2 emission mitigation in the coming decades is inevitable for the control of global warming caused by greenhouse gases. A shift from fossil fuels to green energy sources is essential for a sustainable future. Hydrogen, as an energy storage carrier and a possible solution for consumption in chemical synthesis such as fertilizers, is mainly produced by steam reforming. H2 separation from CO2 and purification are considered as energy intensive processes.

[0004] Capturing H2 from waste streams, such as gases emitted by the metal industry, can reduce the demand for fresh H2 and, therefore, the carbon dioxide emissions of the metal industry. Currently, conventional technologies for separating H2 from waste streams are limited, so these gases are only combusted to recover energy or sent to flare systems. CO2 separation and purification from industrial exhaust gases, such as those from power plants and refineries, is considered one of the major challenges in recent years.

[0005] Polymeric membranes are considered a mature technology in areas such as water purification by reverse osmosis, but are still in their infancy in gas separation processes. Polymeric membranes for H2 / CO2 and CO2 / N2 separations experience swelling (the polymer structure swells) due to the sorption of CO2. The swelling phenomenon reduces the selectivity and final performance of the polymeric membrane. Inorganic membranes do not swell and are therefore considered as a potential technology for H2 / CO2 and CO2 / N2 separation.

[0006] Conventional methods such as absorption have drawbacks, such as energy use and solvent losses, that prevent their widespread adoption in industry. Therefore, new methods are needed to remove these obstacles and enable CO2 separation and purification to be widely implemented in industrial processes.

[0007] Furthermore, in high-temperature, high-pressure applications such as membrane reactors for H2 production, polymer membranes are limited in their usable temperature and pressure ranges due to CO2 sorption in the structure and swelling of the polymer.

[0008] Due to the chemical limitations of polymer membranes, such as swelling and instability at high temperatures, H2 / CO2 and CO2 / N2 separations are carried out at lower temperatures and pressures. Cross-linking of the polymer is a common method to reduce swelling, but it has drawbacks such as reduced water permeability and increases the membrane surface area required for the process.

[0009] Currently, limitations of membranes in gas separation processes call for new high performance membranes.

[0010] Palladium membranes have been actively studied in recent years due to their unique H2 permeation mechanism. Palladium membranes can achieve almost infinite selectivity and high permeability in the H2 separation and purification process. Palladium, a precious metal, has even surpassed gold prices in recent years due to supply shortages and high market demand. Palladium membranes can undergo a phenomenon called embrittlement at a certain temperature, which can lead to the membrane being destroyed. In addition, the hydrogen transport mechanism of palladium membranes follows the square root of the hydrogen concentration. For this reason, it is limited to increase the hydrogen flow rate by increasing the operating pressure difference between the filtration product and the distillate in order to reduce the membrane surface area required for the separation process.

[0011] Carbon membranes, which are inorganic membranes, are produced by carbonizing thermosetting polymers in an inert atmosphere or vacuum. Carbon membranes, with their molecular sieving and surface adsorption transport mechanisms, are considered potential industrial gas separation solutions. Due to their carbon structure and chemical stability, carbon membranes can function at temperatures up to 500°C and operating pressure differentials as high as 140 bar depending on the support.

[0012] Supported carbon membranes are used because self-supporting carbon membranes have physical limitations, such as mechanical fragility. The membrane's physical stability is improved and the membrane thickness can be thinned to the range of a few microns, improving the membrane's permeability performance. The thickness of the supported carbon membrane can be thinned to around 1 μm to increase the flow rate through the carbon membrane. Summary of the Invention

[0013] It is an object of the present invention to provide a membrane that exhibits high selectivity for H2 / CO2 and H2 permeability, or that exhibits high selectivity for H2 / N2 and H2 permeability, and / or that exhibits high selectivity for CO2 / N2 and CO2 permeability.

[0014] Another object of the present invention is to provide a high temperature resistant film with performance testing up to 470°C.

[0015] Another object of the present invention is to provide a tubular supported membrane capable of high operating pressures with a pressure difference between the retentate and the filtered product of up to 70 bar. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 shows the permeability of membranes at multiple temperatures. [Diagram 2] FIG. 1 shows membrane performance compared to literature upper limits for H2 / N2 separation membranes. [Diagram 3] FIG. 13 depicts H2 permeability at different operating pressures and temperatures. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The present invention therefore provides in a first aspect a method for producing a carbon membrane supported on a ceramic support from hydroquinone, the method comprising the steps of: a) synthesizing a precursor oligomer by condensation of hydroquinone with formaldehyde in an aqueous acidic medium and heating; b) preparing an immersion solution in an organic solvent; c) coating a ceramic support with the dip-coating solution prepared in step b); d) drying and polymerizing the top layer of the coated support of step c); e) carbonizing the polymerized structure of step d); f) post-treating the carbonized structure of step e); Optionally, g) repeating steps c) to f) for a multi-layer carbon film; and Includes.

[0018] The present invention relates to the separation of H2 and CO2 from gas mixtures by carbon membranes synthesized from thermoset polyhydroquinone precursors. The membranes are supported on ceramic porous materials by coating methods. The membranes can operate at very high temperatures and pressures. The ideal selectivities and permeabilities for H2 / CO2, CO2 / N2 and H2 / N2 well exceed the performance of current organic membranes, such as the Robson upper limit of polymeric membranes. The high selectivity and permeability combined with lower cost and high chemical and mechanical stability compared to palladium membranes reduces the cost of H2 separation and purification in capital and operating costs.

[0019] In one example, the soaking solution includes precursor oligomers, formaldehyde, and other permeation enhancing components capable of initiating polymerization and adding functional groups to the polymer.

[0020] In one example, step b) further comprises synthesizing a copolymer with ethylenediamine or a conjugated polymer with aluminum acetylacetonate.

[0021] In one example of the method, post-treatment step f) comprises humidifying and oxidizing the upper layer of the membrane with a stream of diluted oxygen concentration, which is used to open the pores by oxidation and increase the permeability of the carbon membrane.

[0022] In one embodiment of the method, the carbonization temperature according to step e) is in the range of 500-1200°C.

[0023] In one example of the method, several coating layers are applied onto the ceramic support, the number of layers preferably being in the range of 1-8, and the thickness of each layer preferably being in the range of 300 nm-20 μm.

[0024] In one example of this method, hydroquinone copolymers are prepared from hydroquinone oligomers in an organic solvent by the addition of reagents such as ethylenediamine, aluminum acetylacetonate and formaldehyde, or combinations thereof.

[0025] In one example of the method, for the step of preparing the immersion solution, hydroquinone oligomer is used as the main precursor and is mixed with at least one component selected from the group of polyvinyl butyral (PVB), aluminum acetylacetonate, and ethylenediamine, or a combination thereof.

[0026] In one example of the method, the porous ceramic support is selected from the group of Al2O3, ZrO2, MgO, zeolites, TiO2, SiO2, CeO2, YSZ, porous transition metal oxide tubes, or combinations thereof.

[0027] In a second aspect, the present invention also relates to a membrane on a ceramic tubular support, said membrane comprising at least one layer of a hydroquinone carbon membrane.

[0028] In a third aspect, the present invention also relates to the use of a membrane as defined above or a membrane obtained according to the method as defined above for the separation of H2 and / or CO2 from a gas mixture.

[0029] In one example, the gas separation process is selected from the group: H2 / CO2, CO2 / N2, and H2 / N2.

[0030] In one example, the membrane is used for H2 separation and purification in an H2 production reactor.

[0031] In one example, the membranes are used for H2 recovery from waste streams such as metal industry blast furnace off-gas processing and fertilizer manufacturing purge gas streams.

[0032] In one example, the membranes are used in CO2 separation and / or carbon capture and utilization (CCU) processes for carbon capture and storage (CCS), such as CO2 separation from post-combustion gas streams or biosyngas purification.

[0033] The present invention focuses on supported carbon membranes for H2 / CO2, H2 / N2 and CO2 / N2 separation processes. Hydroquinone membranes on ceramic tubular supports with a thickness of several micrometers are fabricated and permselective tests are carried out at temperatures between 45°C and 470°C with a pressure difference of up to 30 bar between the retentate and the filtrate product. The fabrication parameters are adjusted to reach high performance in terms of permselective properties for the respective gas separation process. Hydroquinone oligomers are used as the main precursor for the carbon membranes and are copolymerized with ethylenediamine for CO2 / N2 and mixed with polyvinyl butyral (PVB) for the H2 / CO2 separation process. Carbon membranes are also synthesized with aluminum acetylacetonate and hydroquinone oligomers to obtain composite structure carbon membranes for H2 / N2 separation. All three membranes are supported on tubular ceramic supports with average pore sizes of 100 nm for α-alumina supports and 120 nm for zirconia supports.

[0034] The invention is illustrated by the following non-limiting examples. EXAMPLES

[0035] Table 1 summarizes the fabrication parameters of the three developed membranes. Table 1: Preparation parameters of hydroquinone tubular supported carbon membrane [Table 1]

[0036] Elemental analysis of the films was performed and the results are summarized in Table 2. Table 2: Elemental analysis of hydroquinone carbon film wt% [Table 2]

[0037] Example 1: H2 / CO2 selective membrane In steam reforming reactors, high H2 / CO2 selectivity is required, firstly to shift the equilibrium towards the product side by removing one of the products according to Le Chatelier's principle, and secondly to produce high purity H2 in the filtered product. Hydroquinone oligomers are used as the main precursor for the synthesis of H2 / CO2 selective membranes. The membranes consist of three ultrathin layers, each layer stacked on top of the other, optimized with manufacturing parameters to have high selectivity and maintain high permeability.

[0038] The results of the permselectivity tests for H2 / CO2 membranes are compared with the upper limits of polymeric membranes. The most cited upper limits (Robeson, 2008) and three upper limits according to the operating temperatures from the 2020 literature (35, 100, 150 and 200 °C) show that the performance of H2 / CO2 selective hydroquinone membranes is superior to organic membranes in both ideal selectivity and H2 permeability at operating temperatures between 45 °C and 470 °C and operating pressures between 1 and 6 barg.

[0039] The hydroquinone membrane achieved a maximum ideal H2 / CO2 selectivity of 43 and H2 permeability of 12455 Barrer at 1 bar and 350℃. The chemical and physical stability of the membrane was tested at 350℃ and 1 bar working pressure for 380 hours.

[0040] Example 2: CO2 / N2 selective membrane Industrial-scale separation of CO2 from flue gas can be commercially viable with a minimum CO2 / N2 selectivity of 70 and a CO2 / N2 selectivity of 3.3×10 -7 mol / (m 2 For a CO2 / N2 selective hydroquinone carbon membrane, the requirements are valid and the application of this membrane may have an important role in industries for CO2 separation from flue gas streams such as metal production, power plants, and bio-refineries.

[0041] The membrane is fabricated on a tubular porous zirconia support with an average pore size of 120 nm. Two ultra-thin selective carbon layers are used to reach the desired permselective performance. The carbon membrane is composed of two selective layers: the top layer with a larger pore size acts as the absorption site, while the second layer with a smaller average pore size prevents the diffusion of N2 molecules.

[0042] The transport mechanism of the membrane mainly follows surface diffusion for CO2. The membrane fabrication is based on condensation polymerization of oligomers and carbonization in an inert atmosphere. Figure 1 shows the permeability of the membrane at several temperatures.

[0043] Figure 1 shows that at operating pressures of 1-6 barg and operating temperatures of 45°C-470°C, the performance of the CO2 / N2 selective hydroquinone carbon membrane is higher than that of the polymer membrane.

[0044] The CO2 / N2 selective hydroquinone carbon membrane reached a maximum ideal selectivity of 680 and a CO2 permeability of 1471 Barrer at 150°C and a pressure difference of 2 bar between the filtrate and the retentate.

[0045] Example 3: H2 / N2 selective membrane Hydrogen recovery from waste streams in industries such as metals, bio-refineries, and fertilizer production can increase process efficiency and reduce consumption of fresh hydrogen, which is primarily produced from fossil fuels and contributes to greenhouse gas emissions.

[0046] A bilayer H2 / N2 selective hydroquinone carbon membrane is fabricated on a zirconia porous support with an average pore size of 120 nm. The membrane performance is tested at temperatures between 45°C and 470°C and pressures between 1 bar and 6 bar. The membrane is carbonized at 600°C in N2 atmosphere.

[0047] FIG. 2 shows the performance of the membrane compared to the upper limit of the literature for H2 / N2 separation membranes.

[0048] The H2 / N2 selective membrane reached a maximum ideal selectivity of 302 at 2 bar and 150°C, with a hydrogen permeability of 1314 Barrer. Figure 3 shows the H2 permeability at different operating pressures and temperatures.

Claims

1. a) synthesizing a precursor oligomer by condensation of hydroquinone with formaldehyde in an aqueous acidic medium and heating; b) preparing an immersion solution in an organic solvent; c) coating a ceramic substrate with the dip-coating solution prepared in step b); d) drying and polymerizing the top layer of the coated substrate of step c); e) carbonizing the polymerized structure of step d); f) post-processing the carbonized structure of step e); Optionally, g) repeating steps c) through f) for a multi-layer carbon film; and 1. A method for producing a carbon membrane supported on a ceramic support from hydroquinone comprising:

2. 10. The method of claim 1, wherein the soaking solution comprises the precursor oligomer, formaldehyde, and other permeation-enhancing components capable of initiating polymerization and adding functional groups to the polymer.

3. 10. The method of claim 1, wherein step b) further comprises synthesizing a copolymer with ethylenediamine or a conjugated polymer with aluminum acetylacetonate.

4. 10. The method of claim 1, wherein the post-treatment of step f) comprises humidifying and oxidizing the carbon film with a diluted oxygen stream.

5. The method of claim 1, wherein in step e) the carbonization temperature is in the range of 500 to 1200°C.

6. The method of claim 1, wherein several layers of coating are applied onto the ceramic support, the number of layers being in the range of 1 to 8, and the thickness of each layer being in the range of 300 nm to 20 μm.

7. 10. The method of claim 1, wherein the soaking solution in the organic solvent is prepared with reagents such as ethylenediamine, aluminum acetylacetonate and formaldehyde, or a combination thereof.

8. 8. The method of claim 7, wherein hydroquinone oligomer is used as the main precursor and is mixed or copolymerized with at least one component selected from the group of polyvinyl butyral (PVB), aluminum acetylacetonate, and ethylenediamine, or a combination thereof.

9. The ceramic support is Al ２ O ３ , ZrO ２ , TiO ２ , MgO, zeolite, SiO ２ , CeO ２ , YSZ porous transition metal oxide tubes, or combinations thereof.

10. A membrane on a ceramic tubular support comprising at least one layer of a hydroquinone carbon membrane.

11. H from the gas mixture ２ and / or CO ２ Use of a membrane according to claim 10 or obtained according to the method according to any one of claims 1 to 9 in the separation of

12. The gas separation process involves ２ / CO ２ , CO ２ / N ２ and H ２ / N ２ 12. Use of the membrane according to claim 11, selected from the group

13. H ２ H in the production reactor ２ Use of the membrane of claim 11 in separation and purification.

14. H from waste streams such as metal industry blast furnace off-gas treatment and fertilizer manufacturing purge gas streams ２ Use of the membrane of claim 11 in recovery.

15. CO from post-combustion gas stream ２ CO separation or biosyngas purification for carbon capture and storage (CCS) ２ 12. Use of the membrane of claim 11 in a separation and / or carbon capture and utilization (CCU) process.

Images