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EP-4739425-A1 - TAILORED HYDROPHOBIC CARBON MOLECULAR SIEVE MEMBRANE

EP4739425A1EP 4739425 A1EP4739425 A1EP 4739425A1EP-4739425-A1

Abstract

It is provided a hydrophobic carbon molecular sieve membrane (CMSM) characterized by comprising pores with a pore size distribution in which at least 20 % of the pores have a pore size from 0.5 to 0.6 nm, measured by perm-porosimetry; and having a C/O ratio higher than 8 and a C/H ratio higher than 20; the membrane being obtainable by dip- coating a support with a dipping solution comprising a carbon precursor, a non-aqueous solvent, a curing agent, and a pore forming agent, wherein the pore forming agent is in an amount from 0.5 wt% to 8 wt% related to the weight of carbon precursor; followed by carbonization at a temperature higher than 700 ºC and lower than 1000 ºC; and wherein the carbon molecular sieve membrane has a higher hydrophobicity than a membrane prepared by the same process but without the addition of the pore forming agent. It is also provided a method for the preparation of the CMSM, and its use for the selective separation of propionic acid from a mixture with water and acetic acid and as a membrane reactor or part of a membrane reactor.

Inventors

  • PACHECO TANAKA, DAVID ALFREDO
  • LLOSA TANCO, Margot Anabell
  • RAHIMALIMAMAGHANI, Arash
  • GALLUCCI, FAUSTO

Assignees

  • Fundación Tecnalia Research & Innovation
  • Eindhoven University Of Technology

Dates

Publication Date
20260513
Application Date
20240705

Claims (15)

  1. 1 . An hydrophobic carbon molecular sieve membrane characterized by comprising pores with a pore size distribution in which at least 20 % of the pores have a pore size from 0.5 to 0.6 nm, measured by perm-porosimetry; and having a C/O ratio higher than 8 and a C/H ratio higher than 20; the membrane being obtainable by dip-coating a support with a dipping solution comprising a carbon precursor, a non-aqueous solvent, a curing agent, and a pore forming agent, followed by carbonization at a temperature higher than 700 °C and lower than 1000 °C; wherein the pore forming agent is in an amount from 0.5 wt% to 8 wt% related to the weight of carbon precursor; and wherein the carbon molecular sieve membrane has a higher hydrophobicity than a membrane prepared by the same process but without the addition of the pore forming agent; optionally, wherein the membrane comprises a pore size distribution in which less than 20 % of the pores have a pore size from 0.3 to 0.4 nm.
  2. 2. The hydrophobic carbon molecular sieve membrane according to claim 1 , wherein at least 30 % of the pores have a pore size from 0.5 to 0.6 nm and at least 35 % of the pores have a pore size from 0.4 to 0.6 nm, measured by perm-porosimetry; the C/O ratio is higher than 15 and the C/H ratio is higher than 30; the pore forming agent is in an amount from 0.5 wt% to lower than 1 wt% related to the weight of carbon precursor; and the carbonization at a temperature is from 750 °C to lower than 850 °C; or, alternatively, wherein at least 65 % of the pores have a pore size from 0.5 to 0.6 nm and at least 80 % of the pores have a pore size from 0.4 to 0.6 nm, measured by perm-porosimetry; and having a C/O ratio higher than 25 and a C/H ratio higher than 150; the membrane being obtainable by dip-coating a support with a dipping solution comprising a phenolformaldehyde resin or a benzoxazine resin as a carbon precursor, a non-aqueous solvent, a curing agent, and a pore forming agent, wherein the pore forming agent is in an amount from 0.5 wt% to lower than 1 wt% related to the weight of carbon precursor; followed by carbonization at a temperature from 850 °C to lower than 900 °C; or, alternatively, wherein at least 40 % of the pores have a pore size from 0.5 to 0.6 nm and at least 55 % of the pores have a pore size from 0.4 to 0.6 nm, measured by perm-porosimetry; the C/O ratio is higher than 18 and the C/H ratio higher than 50; the pore forming agent is in an amount from 1 wt% to 5 wt% related to the weight of carbon precursor; and the carbonization temperature is from 750 °C to lower than 850 °C; or, alternatively, wherein at least 75 % of the pores have a pore size from 0.5 to 0.6 nm and at least 82 % of the pores have a pore size from 0.4 to 0.6 nm, measured by perm-porosimetry; the C/O ratio higher than 35 and the C/H ratio higher than 200; the pore forming agent is in an amount from 0.7 wt% to lower than 1 wt% related to the weight of carbon precursor; and the carbonization temperature is from 850 °C to lower than 900 °C; or, alternatively, wherein at least 80 % of the pores have a pore size from 0.5 to 0.6 nm and at least 85 % of the pores have a pore size from 0.4 to 0.6 nm, measured by perm-porosimetry; the C/O ratio higher than 40 and the C/H ratio higher than 300; the pore forming agent is in an amount from 1 wt% to 5 wt% related to the weight of carbon precursor; and the carbonization temperature is from 850 °C to lower than 900 °C.
  3. 3. The hydrophobic carbon molecular sieve membrane according to claims 1 or 2, wherein the pore forming agent is selected from the group consisting polyvinyl butyral, cellulose ethers such as methylcellulose, cellulose esters such as cellulose acetate, poly(vinyl alcohol), polyvinylpyrrolidone, polylactic acid; and poloxamers, particularly polyvinyl butyral; optionally, wherein the a carbon precursor is a phenol-formaldehyde resin or a benzoxazine resin.
  4. 4. A process for the preparation of a hydrophobic carbon molecular sieve membrane as defined in claim 1, the process comprising: a) providing a porous support; b) providing a dipping solution comprising a carbon precursor such as a phenolformaldehyde resin or a benzoxazine resin, a non-aqueous solvent, a curing agent, and the pore forming agent, wherein the pore forming agent is in an amount from 0.5 wt% to 8 wt%, particularly, higher than 0.5 wt% to 8 wt%, related to the weight of carbon precursor; c) dipping the porous support at least once in the dipping solution of step b) to obtain a coated support; d) optionally, drying the coated support of step c); e) carbonizing the coated support of step c) or of step d) at a temperature higher than 700 °C and lower than 1000 °C in a non-oxidizing atmosphere or vacuum to obtain a supported carbon molecular sieve membrane; and f) cooling the supported carbon molecular sieve membrane of step e) to room temperature; or, alternatively, a) providing a solution comprising a phenol-formaldehyde resin or a benzoxazine resin as carbon precursor, a non-aqueous solvent, a curing agent, and the pore forming agent, wherein the pore forming agent is in an amount from 0.5 wt% to 8 wt%, particularly, higher than 0.5 wt% to 8 wt%, related to the weight of carbon precursor; b) casting the solution of step a) on a substrate to obtain a membrane precursor; c) carbonizing the membrane precursor of step c) at a temperature higher than 700 °C and lower than 1000 °C in a non-oxidizing atmosphere or vacuum to obtain a selfsupported carbon molecular sieve membrane; and d) cooling the self-supported carbon molecular sieve membrane of step e) to room temperature.
  5. 5. The process according to claim 4, wherein the carbon precursor is in an amount from 2 wt% to 30 wt% of the dipping solution.
  6. 6. The process according to claims 4 or 5, wherein the carbon precursor is a phenol formaldehyde resin, in particular, a resorcinol-formaldehyde resin.
  7. 7. The process according to claims 4 to 6, wherein the pore forming agent is selected from the group consisting polyvinyl butyral, cellulose ethers such as methylcellulose, cellulose esters such as cellulose acetate, poly(vinyl alcohol), polyvinylpyrrolidone, polylactic acid; and poloxamers.
  8. 8. The process according to any one of claims 4 to 7, wherein the pore forming agent is in an amount from 0.5 wt% to 10 wt% related to the weight of carbon precursor.
  9. 9. The process according to any one of claims 4 to 8, wherein the pore forming agent is polyvinyl butyral.
  10. 10. The process according to claim 9, wherein polyvinyl butyral is in an amount from 0.8 wt% to 1.2 wt% related to the weight of carbon precursor.
  11. 11. The process according to any one of claims 4 to 10, wherein the carbonizing temperature is from 750 °C to 950 °C or from 800 °C to 900 °C.
  12. 12. The process according to any one of claims 4 to 11 , wherein the carbonization is carried out at a heating rate of from 0.2 °C/min to 10 °C/min and a dwell time from 1 to 40 h.
  13. 13. A method for the selective separation of propionic acid from an aqueous mixture comprising propionic acid, in particular, from an aqueous mixture comprising propionic acid and acetic acid, the process comprising: a) providing a hydrophobic carbon molecular sieve membrane as defined in any one of claims 1 to 3; and b) contacting an aqueous mixture comprising propionic acid, in particular, the aqueous mixture comprising propionic acid and acetic acid, with one side of the membrane while vacuum is applied in the other side of the membrane to produce a permeate gas stream in order to separate propionic acid by pervaporation.
  14. 14. Use of a hydrophobic CMSM as defined in any one of claims 1 to 3 for the selective separation of propionic acid, in particular, from a mixture containing propionic acid, water and acetic acid.
  15. 15. Use of a hydrophobic CMSM as defined in any one of claims 1 to 3, as a membrane reactor or part of a membrane reactor.

Description

Tailored hydrophobic carbon molecular sieve membrane This application claims the benefit of European Patent Application EP23382699.9 filed on July 07, 2023. Technical Field The present invention relates to carbon molecular sieve membranes (CMSMs) having hydrophobic pores of a specific size and size distribution and their uses for the selective separation of some compounds such as propionic acid, or as membrane reactors. Background Art Propionic acid (PA), is intensively used as antimicrobial agent, anti-inflammatory substance, herbicides, preservatives in bakery and cheese products. Industrially, PA is mainly produced through a petrochemical route reaching to a global market size of 1.5 billion USD in 2021 and estimated to grow to about 1.8 billion USD by 2028. Due to the global increasing demand for PA and problems such as global warming associated with petrochemical route production of PA, bio-PA is preferred as a sustainable alternative. Production of PA in bioreactors are studied for decades. Unfortunately, petrochemical production still is more economical than microbial production. In the fermentative production of propionic acid, Propionibacterium ssp. is a promising genus. However, the specific growth rate usually drops by more than 50% when there is 1% propionic acid present in the medium. The low productivity and low concentration of the PA produced in the conventional propionic acid fermentations seems to be due to the strongly inhibition produced by PA specially when the pH is below 6. Acetic acid is the most important by-product produced during propionic fermentation and it can impair PA production (due to its toxicity) and recovery in downstream processing. Low acid concentration ensures higher product yield and lower amounts of by-products. One way to increase the yield is by in-situ extraction of PA from the fermentation (extractive fermentation processes). Several techniques have been reported to remove PA such as solvent extraction, electrodialysis, and resin adsorption. Membrane such as carbon molecular sieve membranes (CMSMs) are potential candidates for PA in-situ separation by pervaporation. In a PA pervaporation separation process, key parameters such as high PA permeance, PA perm-selectivity and stable performance require a tailor-made membrane regarding hydrophobicity, pore size distribution (PSD) and porosity. CMSMs are product of the carbonization of thermosetting polymers such as polyimides and phenolic resins, offering the mentioned tunable properties, while being inexpensive (see M.A. Llosa et al., "Composite-alumina-carbon molecular sieve membranes prepared from Novolac resin and boehmite. Part I: Preparation, characterization and gas permeation studies", Int. J. Hydrogen Energy. 2015, vol. 40, pp. 5653-5663; M.A. Llosa et al. "Composite-Alumina-Carbon Molecular Sieve Membranes Prepared from Novolac Resin and Boehmite. Part II: Effect of the Carbonization Temperature on the Gas Permeation Properties". Int J Hydrogen Energy 2015, Vol. 40, pp. 3485-3496; J. A. Hamm, et al., "Recent advances in the development of supported carbon membranes for gas separation", Int J Hydrogen Energy, 2017, Vol. 42, pp. 24830-24845). CMSMs can be tailored made by modifying their precursor, nano additives in their structure, carbonization atmosphere and temperature, polymerization degree (PD), and post treatment (see A. Rahimalimamaghani, et al. "Ultra-Selective CMSMs Derived from Resorcinol-Formaldehyde Resin for CO2 Separation". Membranes 2022, Vol. 12, Page 8472022, 12, 847; A. Rahimalimamaghani, et al. "Effect of aluminium acetyl acetonate on the hydrogen and nitrogen permeation of carbon molecular sieves membranes". Int J Hydrogen Energy, 2022, Vol. 47, pp. 14570-14579). However, enhancing both PA perm-selectivity and permeance faces challenges due to existing problems such as the stability of the membrane, fouling, reproducibility, and tradeoff between perm-selectivity and permeance which hinders from industrial application. Therefore, from what is known in the state of the art, there is still a need for a stable chemically/physically CMSM for long term performance and efficient in-situ separation of PA from low concentration aqueous phases in membrane bio reactors. Summary of Invention The inventors of the present invention have developed a hydrophobic carbon molecular sieve membrane (CMSM) obtained by dip-coating a support with a dipping solution comprising a phenolic resin and a polymer acting as pore forming agent and source of hydrophobic carbon and, then, carrying out a carbonization at a temperature higher than 700 °C and lower than 1000 °C in order to make the membrane hydrophobic. In particular, the inventors have found that the incorporation of a certain amount of a pore forming agent such as polyvinyl butyral (PVB), methylcellulose, poly(vinyl alcohol) (PVOH), and polyvinylpirrolidone (PVP), among others, to the dipping solution allows obtaining a carbon molecular sieve membrane wi