A PROCESS FOR THE PREPARATION OF A SUPPORTED CARBON MEMBRANES (CMS)

Abstract

The present invention relates to a process for the preparation of a supported Carbon Membranes (CMS). The present invention also relates to a process for the separation of a gas from a gas mixture and to the use of use of a supported CMs as a membrane reactor or in a membrane reactor.

Claims

1-16. (canceled)

17. A process for the preparation of a supported carbon membrane (CM), the process comprising the steps of: providing a porous support; providing a coating solution containing a polymeric carbon precursor; providing a non-solvent in which the polymeric carbon precursor has a low solubility; contacting the porous support with the non-solvent and removing the excess non-solvent from the surface of the porous support to form a solvent treated support; coating the solvent treated support with the coating solution; drying the coated support; and carbonizing the dried coated support to obtain a supported carbon membrane (CM).

18. The process according to claim 17, wherein the porous support is an inorganic support.

19. The process according to claim 17, wherein the porous support is ceramic based on a metal oxide, nitride, boride, carbon, or carbide.

20. The process according to claim 17, wherein the porous support is selected from the group including alpha alumina, titanium oxide, zirconium oxide, ceria, and gamma alumina silicon carbide.

21. The process according to claim 17, wherein the porous support is metallic selected from the group including steel, stainless steel, and Inconel.

22. The process according to claim 17, wherein the coating solution is prepared by a thermosetting polymer carbon precursor, and wherein the thermosetting polymer precursor is dissolved in an organic solvent.

23. The process according to claim 22, wherein the thermosetting polymer carbon precursor is a Novolac oligomer, and the organic solvent is N-methyl pyrrolidone.

24. The process according to claim 17, wherein the step of contacting the porous support with the non-solvent and removing the excess non-solvent from the surface of the porous support to form the solvent treated support includes filling pores of the porous support with the non-solvent.

25. The process according to claim 17, wherein the step of contacting the porous support with the non-solvent and removing the excess non-solvent from the surface of the porous support to form the solvent treated support includes immersing the porous support in the non-solvent.

26. The process according to claim 17, wherein the step of contacting the porous support with the non-solvent and removing the excess non-solvent from the surface of the porous support to form the solvent treated support includes removing the excess non-solvent with an adsorbent cloth.

27. The process according to claim 17, wherein the step of carbonizing the dried coated support to obtain the supported carbon membrane (CM) s is performed under an inert atmosphere or vacuum.

28. The process according to claim 17, wherein the step of carbonizing the dried coated support to obtain the supported carbon membrane (CM) is performed at a carbonization temperature from 350 C. to 1100 C.

29. The process according to claim 17, wherein the step of carbonizing the dried coated support to obtain the supported carbon membrane (CM) is performed at a carbonization temperature from 500 C. to 850 C.

30. The process according to claim 17, wherein the step of carbonizing the dried coated support to obtain the supported carbon membrane (CM) is performed at a carbonization pressure in a range from 2 mbar to 6 bar and with gas including at least one of N.sub.2, He, Ar, and air.

31. The process according to claim 17, wherein the obtained supported carbon membrane (CM) is used as a membrane reactor or in a membrane reactor.

32. The process according to claim 17, wherein the obtained supported carbon membrane (CM) is used in at least one of industrial gas separation to separate H.sub.2, produce olefines from paraffins by dehydrogenation, transport and store H.sub.2 in gas grids, separate CO.sub.2 in biogas upgrading, post combustion, removal of water gas in CO.sub.2 reduction with H.sub.2 for the production of methanol, DME, CH.sub.4, solvent dehydration, and separate olefines from paraffins.

33. A process for separating a gas from a gas mixture, the process comprising the steps of: providing a supported carbon membrane (CM) obtained according to claim 17; providing a gas mixture comprising at least two gases; and feeding the gas mixture to the supported carbon membrane (CM) at a temperature from 5 C. to 600 C. to obtain a retentate and a permeate.

34. The process according to claim 33, wherein the at least two gases are selected from the group including He, H.sub.2O, Ne, H.sub.2, NO, Ar, NH.sub.3, N.sub.2, O.sub.2, CO, CO.sub.2, CH.sub.4, C.sub.2H.sub.4, C.sub.2H.sub.6, propene, propane, H.sub.2S, methanol, ethanol, DME, 1-2 propanol and 1-2 butanol.

35. The process according to claim 33, wherein the gas mixture is selected from the group including He/CH.sub.4, H.sub.2S/CH.sub.4, H.sub.2/CH.sub.4, H.sub.2/N.sub.2, H.sub.2/CO.sub.2, CO.sub.2/CH.sub.4, CO.sub.2/N.sub.2, and O.sub.2/N.sub.2.

Description

[0043] Schematic 1 illustrates a SEM schematic from the ultra-selective CM with a top selective layer.

[0044] FIG. 1 illustrates the H.sub.2 permeances for membranes fabricated with ultra-selective CM and Pore filled CM at multiple temperatures.

[0045] FIG. 2 illustrates the N.sub.2 permeances for membranes fabricated with ultra-selective CM and Pore filled CM at multiple temperatures.

[0046] FIG. 3 illustrates the H.sub.2 permeabilities for membranes fabricated with ultra-selective CM and Pore filled CM at multiple temperatures.

[0047] FIG. 4 illustrates the N.sub.2 permeabilities for membranes fabricated with ultra-selective CM and Pore filled CM at multiple temperatures.

[0048] FIG. 5 illustrates the N.sub.2 permeances for membranes fabricated with ultra-selective CM and Pore filled CM at multiple pressure differences at 200 C.

[0049] FIG. 6 illustrates the H.sub.2 permeances for membranes fabricated with ultra-selective CM and Pore filled CM at multiple pressure differences at 200 C.

[0050] FIG. 7 illustrates the comparison in H.sub.2/N.sub.2 ideal selectivity for membranes fabricated with ultra-selective CM and Pore filled CM.

[0051] FIG. 8 indicates the comparison between CMSMs and Robeson's upper bound limit for the H.sub.2/N.sub.2 selectivity vs, H.sub.2 permeability for polymeric membranes.

[0052] FIG. 9 indicates the comparison of CO.sub.2 permeance in pore filled CM to ultra-selective CM.

[0053] FIG. 10 indicates the comparison of H.sub.2O permeance in pore filled CM to ultra-selective CM as a function of temperature.

[0054] FIG. 11 indicates the comparison of He permeance in pore filled CM to ultra-selective CM as a function of temperature.

EXAMPLES

[0055] The precursor is synthesized from polycondensation of formaldehyde with phenol in acidic media to form Novolac oligomers. The process starts with melting 32 g of phenol at 50 C. in a round bottom three neck glass vessel. In the next step 0.5 g of oxalic acid is added to the solution. In the final step the temperature increased to 85 C. and the 23 g of formaldehyde (37 wt. %) is added to the solution and reacted for 3 hr. The dipping solution is made by dissolving Novolac oligomer in an organic solvent such as N-Methyl-2-pyrrolidone. In the next step, the tubular alpha alumina supports (10 mm 7 mm external internal diameter). One end was closed and both end surfaces were sealed with glass to glass leaving xx cm of effective membrane length. The porous support was immersed in a non-solvent to fill the pores with the solution. The excess non-solvent present on the surface is removed by adsorbent paper. Then, the supports are dip coated with a custom-made dipping machine with the prepared polymeric solution. After the dip coating, the coated supports are moved to the rotary drying oven and are dried for 24 hr at 80 C. In the final step, the coated supports are moved to carbonization oven and carbonized under inert atmosphere at 600 C.

[0056] After carbonization, the membrane is used in a permeation device for testing. Due to the existing of water-based solution in the pores of the support, it will prevent the polymer to diffuse inside of the support, as the polymer is not soluble in the non-solvent, the polymer will precipitate on the mouth of the pores. This phenomenon results in a thin top selective layer CM in a single dip-dry-carbonization step. If the non-solvent is not clogging the pores, the dipping solution containing the polymer will diffuse into the pores, and after carbonization, the pore size will be reduced producing high resistance to the passage of the permeated gases. In addition, several dip carbonization steps will be required to form a continuous defect free selective layer.

[0057] After carbonization, the membrane is used in permeation cell for testing. Due to the existing of water-based solution in the pores of the support, it will prevent from the dipping solution to diffuse inside of the support. This phenomenon results in a top selective layer CM.

[0058] The single gas permeation tests are carried out in range of 1-6 pressure difference between permeate and retentate in temperature range of 45-200 C. The ideal gas selectivity was calculated based on the permeances of H.sub.2 and N.sub.2 through the membrane and the ratio of them is considered as the ideal selectivity. FIG. 7 illustrates the comparison in H.sub.2/N.sub.2 ideal selectivity for membranes fabricated with ultra-selective CM and Pore filled CM.

[0059] The permeance measurements of H.sub.2 at temperatures between 45-200 C. were performed in pressures differences of 1-6 bar between permeate and retentate streams. FIGS. 3 and 4 shows the effect of the present method in the performance of CMs in terms of H.sub.2 and N.sub.2 permeabilities vs. temperature.

[0060] To analyse the existing defect in the CMs, the multiple pressure difference tests are performed on the CMs and as it could be seen in FIGS. 5 and 6, both ultra-selective and pore filled CMs, do not contain any defects due to the zero slope in H.sub.2 and N.sub.2 permeances vs pressure.

[0061] In this method both selectivity and permeability of the CMs were enhanced, and the membrane separation technology will be competitive to separate and purify gases such as H.sub.2 in an industrial scale in ammonia production, power generation and metal refineries. FIG. 8 indicates the comparison between CMs and Robeson's upper bound limit for the H.sub.2/N.sub.2 selectivity vs, H.sub.2 permeability for polymeric membranes.

[0062] In benchmarking CMs performance with the performance of polymeric membranes upper bound limit, both pore filled and ultra-selective CMs perform higher than polymeric membranes in terms of H.sub.2/N.sub.2 selectivity and H.sub.2 permeability. Ultra-selective CMs, further exhibit higher performance at the same operational conditions such as pressure and temperature against the pore filled CMSMs. Characteristics of the present ultra-selective CMs include i) ultra-thin and defect free selective layer, ii) extremely high permeability with high selectivity, iii) blocking support pores to prevent diffusion, and iv) top selective layer membrane instead of pore filled membrane.

[0063] The present method of fabrication (ultra-selective) of Carbon Membranes (CMs) was investigated and compared to pore filled CMSMs in multiple separation processes.

[0064] The method was tested for separation of CO.sub.2 from CH.sub.4 as an application for natural gas purification and steam reforming. The permeance of CMs, fabricated with the present method, was compared to pore filled membranes as shown in FIG. 9:

[0065] As seen in FIG. 9, the ultra-selective CM which was fabricated with the present method, represented higher CO.sub.2 permeance at operational temperatures ranging from 20 to 350 C. Higher CO.sub.2 permeance in new membranes offers the potential of this innovation in adapting the CM to industrial applications such as CO.sub.2 removal from post combustion with lowering the separation required surface area.

[0066] In another study of superior performance of ultra-selective CMs, separation of water in reaction conditions was investigated and H.sub.2O permeance in pore filled CMs was compared to novel CMs. Water is produced as a by-product in numerous reactions such as methanol synthesis in industries. In-situ separation of water from reaction environment can increase the production of desired product such as methanol due to shifting the equilibrium based on Le Chatelier's effect. Increasing the H.sub.2O permeance in the membranes which are developed to operate at temperatures up to 400 C., enables integration of separation and reaction in one unit, resulting enhancing the yield of process. Present ultra-selective CMs fabrication was performed on enhancing the H.sub.2O permeance at high operational temperatures. The results of this study was summarized in FIG. 10. As it is indicated by FIG. 10, present CMs performed at all operating temperatures (120-400 C.) higher than pore filled CMs in terms of H.sub.2O permeance.

[0067] Due to superior control of pore size distribution and selective layer thickness in novel method compared to pore filled CMs, the improvement of CMs performance in terms of permselectivity was carried out for helium gas separation from natural gas. Helium is the noble gas which is only produced from separation and purification process of natural gas. The USA is the main producer of helium in the world and due to the scarcity of this element and its crucial role in industries such as pharma, aerospace and health care, its price tripled in the past 6 years. Efficient separation of helium from methane could significantly reduce the final cost of pure helium and increase its production from lean gas wells with diluted concentrations of helium. CMs with narrow pore size distribution were produced with the present method and were tested for He permeation at low temperatures. FIG. 11 represents the performance of CMs in terms of helium permeance as a function of temperature. Ultra-selective CMs reached 398 mol.Math.m2.Math.s1.Math.Pa1.Math.e8 helium permeance at 20 C. operational temperature while the pore filled membrane represented only 232 mol.Math.m2.Math.s1.Math.Pa1.Math.e8 helium permeance. Higher helium permeance will reduce the required surface area resulting in lower CAPEX and OPEX for separation units.

[0068] The present invention could be used in industries that require pure gas production and purification such as CO.sub.2 separation and utilization, hydrogen recovery from waste streams, hydrogen production, hydrogen purification, hydrogenation chemical reactions, dehydrogenation chemical reactions. Companies that my use the present invention include but not limited to ammonia production to purify and separate hydrogen from off gas, metal refineries to recover the hydrogen and CO from blast furnace, power plants for precombustion operation, petroleum refineries for hydrogenation of heavy oil, petrochemical plants for dehydrogenation in production of polymers, biorefineries for hydrogenation, and bio syngas production to purify and recover hydrogen and CO. Separation of He from natural gas, natural gas sweetening, biogas upgrading, H.sub.2S separation from biogas, and N.sub.2 separation from natural gas.