Search

US-12624371-B2 - Process to treat a carbon dioxide comprising gas

US12624371B2US 12624371 B2US12624371 B2US 12624371B2US-12624371-B2

Abstract

The invention is directed to a process to convert carbon dioxide to methane by contacting an aqueous solution comprising dissolved carbon dioxide with an electron charged packed bed comprising of a carrier, suitably activated carbon granules, and a biofilm of microorganisms under anaerobic conditions, wherein more than 90 mol % of the dissolved carbon dioxide in the aqueous solution is present as a bicarbonate ion and/or as a carbonate ion.

Inventors

  • Dandan Liu
  • Frederikus DE RINK
  • Johannes Bernardus Maria KLOK

Assignees

  • PAQELL B.V.

Dates

Publication Date
20260512
Application Date
20211013
Priority Date
20201013

Claims (19)

  1. 1 . A process to convert carbon dioxide to methane by contacting an aqueous solution comprising dissolved carbon dioxide with an electron charged packed bed comprising of a carrier and a biofilm of microorganisms under anaerobic conditions, wherein the aqueous solution comprises: a) between 0.3 and 4 M sodium cations, or b) between 0.3 and 4 M sodium and potassium cations, such that more than 90 mol % of the dissolved carbon dioxide in the aqueous solution is present as a bicarbonate ion and/or as a carbonate ion.
  2. 2 . The process according to claim 1 , wherein the carrier is activated carbon granules or activated biochar granules.
  3. 3 . The process according to claim 1 , wherein no power is supplied to the electron charged packed bed.
  4. 4 . The process according to claim 3 , wherein the electron charged packed bed is part of a biocathode in a bioelectrochemical system further comprising an anode, an ion exchange membrane, and a cathode; wherein the packed bed is charged by applying a potential to the bioelectrochemical system resulting in a current between biocathode and anode for a certain time.
  5. 5 . The process according to claim 4 , wherein the aqueous solution as present at the anode is referred to as the anolyte and the aqueous solution as present at the cathode is referred to as the catholyte and wherein a recirculation is performed where part of the catholyte is fed to the anode to become part of the anolyte and part of the anolyte is fed to the cathode to become part of the catholyte.
  6. 6 . The process according to claim 4 , wherein the process is performed in more than one bioelectrochemical systems, each system comprising of the biocathode and an anode; and wherein in one or more bioelectrochemical systems the process is performed while no power is supplied to the electron charged packed bed of these one or more bioelectrochemical systems; and wherein power is supplied to the packed bed of one or more other bioelectrochemical system of the more than one bioelectrochemical systems such that these packed beds are charged with electrons while the process is not performed.
  7. 7 . The process according to claim 4 , wherein the packed bed is charged by applying a cathode potential to the cathode electrode of between −0.50 and −0.60V vs. Ag/AgCl (3M KCl) or by applying a current density to the cathode electrode of between 5 and 200 A/m 2 .
  8. 8 . The process according to claim 4 , wherein the anode is a titanium mesh coated with iridium and/or tantalum.
  9. 9 . The process according to claim 4 , wherein the power supply is generated by a chemical reaction at the anode.
  10. 10 . The process according to claim 4 , wherein the carrier and a biofilm of microorganisms is obtained in an activation step which activation step is performed at a pH greater than 8 and under anaerobic conditions and by supplying an amount of current at a cathode potential which is more positive than the theoretical hydrogen evolution potential at −0.61 V vs Ag/AgCl (3M KCl) at a pH of 7 to the packed bed comprising of carrier and biofilm of microorganisms; and wherein the microorganisms are a mixed culture microorganisms from a sludge of an anaerobic wastewater treatment plant.
  11. 11 . The process according to claim 1 , wherein the electron charged packed bed is part of a biocathode in a bioelectrochemical system further comprising an anode; and wherein at one moment in time the process is performed when the packed bed is charged by applying a potential to the bioelectrochemical system resulting in a current between biocathode and anode; and wherein at another moment in time the process is performed when no power is supplied to the electron charged packed bed.
  12. 12 . The process according to claim 11 , wherein the process is performed for between 0.03 and 12 hours when no power is supplied to the electron charged packed.
  13. 13 . The process according to claim 11 , wherein the power supply is electricity generated by solar and/or wind.
  14. 14 . The process according to claim 1 , wherein the packed bed is a packed bed of activated carbon granules having an activated surface area of between 500 and 1500 m 2 /g; and wherein the microorganisms are present as a biofilm on the surface of the activated surface area.
  15. 15 . The process according to claim 1 , wherein the pH of the aqueous solution is above 7.7.
  16. 16 . The process according to claim 15 , wherein the pH of the aqueous solution is above 8.
  17. 17 . The process according to claim 1 , wherein the aqueous solution comprises between 0.5 and 1.5 M sodium cations or between 0.5 and 1.5 M sodium and potassium cations.
  18. 18 . The process according to claim 1 , wherein the aqueous solution comprising dissolved carbon dioxide is obtained by contacting a gas comprising carbon dioxide with an aqueous solution having a pH of above 8 to obtain an aqueous solution wherein a major part of the dissolved carbon dioxide is present as a bicarbonate ion and/or as a carbonate ion.
  19. 19 . The process according to claim 18 , wherein the gas comprising carbon dioxide is counter currently contacted with the aqueous solution having a pH of above 8 and comprising dissolved methane as obtained a process comprising: contacting an aqueous solution comprising dissolved carbon dioxide with an electron charged packed bed comprising of a carrier and a biofilm of microorganisms under anaerobic conditions, wherein more than 90 mol % of the dissolved carbon dioxide in the aqueous solution is present as a bicarbonate ion and/or as a carbonate ion; and wherein the gas strips the methane from the aqueous solution to obtain a gas comprising methane.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a 35 U.S.C. § 371 National Phase Entry Application of International Application No. PCT/EP2021/078266 filed Oct. 13, 2021, which designates the U.S. and claims benefit under 35 U.S.C. § 119(a) of NL Application No. 2026669 filed Oct. 13, 2020, the contents of which are incorporated herein by reference in their entireties. The invention is directed to a process to treat a carbon dioxide comprising gas wherein carbon dioxide is converted to methane in the presence of an electron charged packed bed comprising of a carrier and microorganisms under anaerobic conditions. A journal article titled Granular Carbon-Based Electrodes as Cathodes in Methane-Producing Bioelectrochemical Systems, Dandan Liu, Marta Roca-Puigros, Florian Geppert, Leire Caizán-Juanarena, Susakul P. Na Ayudthaya, Cees Buisman and Annemiek ter Heijne, Frontiers in Bioengineering and Biotechnology, June 2018 |Volume 6, article 78 described a process where carbon dioxide is converted to methane in the presence of an electron charged packed bed comprising of activated carbon granules and a mixed culture microorganisms under anaerobic conditions. The CO2 was supplied as a gas to an aqueous solution having a pH of 7.1. The biocathode consisting of the electron charged packed bed comprising of activated carbon granules and a mixed culture microorganisms was charged for 2 minutes alternating with no charging for 4 minutes. The reported “current to methane” efficiency was 55%. The reported overall energy efficiency was 25%. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a possible process scheme for the process of this invention. FIG. 2 shows the Coulombic efficiency, voltage efficiency and energy efficiency results of Example 1. It is an object of the present invention to improve the energy efficiency to produce methane. This object is achieved by the following process. A process to convert carbon dioxide to methane by contacting an aqueous solution comprising dissolved carbon dioxide with an electron charged packed bed comprising of a carrier and a biofilm of microorganisms under anaerobic conditions, wherein more than 90 mol % of the dissolved carbon dioxide in the aqueous solution is present as a bicarbonate ion and/or as a carbonate ion. Applicants found that when the dissolved carbon dioxide is present as a bicarbonate ion and/or as a carbonate ion a significantly more energy efficient conversion to methane is achieved for the described process. The dissolved carbon dioxide may be present as aqueous carbon dioxide, carbonic, bicarbonate ion and as a carbonate ions. A major part of the dissolved carbon dioxide in the aqueous solution is present as a bicarbonate ion and/or as a carbonate ion. More than 90 mol % and preferably more than 95 mol % of the dissolved carbon dioxide in the aqueous solution is present as a bicarbonate ion and/or as a carbonate ion. The pH conditions at which these compounds are present in an aqueous solution is preferably above 7.5, preferably above 7.7 and more preferably above 8 and even more preferably in the range of from 8 to 10, more preferably of from 8.5 to 9.5. These alkaline conditions may be achieved by a basic salt formed between a weak acid and a strong base, such as sodium bicarbonate and potassium bicarbonate. Such basic salt may be formed by adding sodium cations or sodium and potassium cations. The concentration of sodium cations or the total of sodium and potassium cations is suitably between 0.3 and 4 M, preferably between 0.4 and 2 M and even more preferred between 0.5 and 1.5 M. The resulting aqueous solution is a buffered solution further comprising sodium carbonate and sodium bicarbonate or potassium carbonate and potassium bicarbonate or their mixtures. The aqueous alkaline solution suitably further comprises nutrients for the microorganisms. Examples of suitable nutrients are nutrients such as ammonium, vitamin and mineral elements. It may be desired to add such nutrients to the aqueous alkaline solution in order to maintain active microorganisms. The anaerobic conditions are suitably achieved by performing the process in the absence of molecular oxygen, preferably also in the absence of other oxidants such as for example nitrate. By ‘in the absence of molecular oxygen’ is meant that the concentration of molecular oxygen in the loaded aqueous solution in this process is at most 10 μM molecular oxygen, preferably at most 1 μM, more preferably at most 0.1 μM molecular oxygen. Sulfate, which may be regarded to be an oxidant, may be present at low concentrations of for example 160 μM, as part of a so-called Wolfe's mineral solution. It has been found that the sulfate at these low concentrations does not negatively influence the desired conversion of carbon dioxide. The process is performed by contacting the aqueous solution with an electron charged packed bed comprising of activated carbon granules and microorganisms under anaerobic condition