Extraction of carbon dioxide and hydrogen from seawater and hydrocarbon production therefrom

Patent metadata

Field	Value
Publication number	US-9303323-B2
Application number	US-201313838074-A
Country	US
Kind code	B2
Filing date	Mar 15, 2013
Priority date	May 11, 2010
Publication date	Apr 5, 2016
Grant date	Apr 5, 2016

Abstract

Apparatus for seawater acidification including an ion exchange, cathode and anode electrode compartments and cation-permeable membranes that separate the electrode compartments from the ion exchange compartment. Means is provided for feeding seawater through the ion exchange compartment and for feeding a dissociable liquid media through the anode and cathode electrode compartments. A cathode is located in the cathode electrode compartment and an anode is located in the anode electrode compartment and a means for application of current to the cathode and anode is provided. A method for the acidification of seawater by subjecting the seawater to an ion exchange reaction to exchange H + ions for Na + ions. Carbon dioxide may be extracted from the acidified seawater. Optionally, the ion exchange reaction can be conducted under conditions which produce hydrogen as well as carbon dioxide. The carbon dioxide and hydrogen may be used to produce hydrocarbons.

First claim

What is claimed is:

1. A method for treating seawater, comprising:
feeding water into an anode compartment to generate hydrogen ions, wherein the water fed into the anode compartment has a conductivity less than 300 μS/cm;
feeding water into a cathode compartment;
electrically generating dihydrogen gas in the cathode compartment from water;
feeding seawater comprising bicarbonate and carbonate ions into a central compartment, wherein the central compartment contains either no material or only inert media, and wherein the central compartment is between the anode and cathode compartments and separated from the anode and cathode compartments by cation exchange membranes; and
subjecting the seawater to an ion exchange substitution reaction in the central compartment to exchange the hydrogen ions produced from water in the anode compartment for sodium ions in the seawater, wherein the sodium ions transfer from the central compartment to the cathode compartment;
lowering a pH of the seawater in the central compartment to less than about 6.5 using an electrically driven membrane process wherein seawater pH is inversely proportional to an applied current and independent of any media in the central compartment; and
converting bicarbonate and carbonate to carbonic acid in the central compartment, wherein the dihydrogen gas generated in the cathode compartment and carbon dioxide formed in the central compartment are simultaneously extracted in a controllable molar ratio, wherein the molar ratio of dihydrogen gas to carbon dioxide is controlled in part by varying the applied current density.

2. The method as claimed in claim 1 , wherein the operating conditions are sufficient to lower the pH of the seawater to less than about 4.5.

3. The method as claimed in claim 1 , wherein a current density resulting from the applied current is from about 5 to about 200 mA/cm 2 .

4. The method as claimed in claim 1 , wherein the seawater is fed to the central compartment at a velocity between about 20 to about 500 cm/min.

5. The method as claimed in claim 1 , further comprising the step of reversing the polarity of an anode within the anode compartment and a cathode within the cathode compartment.

6. The method as claimed in claim 1 , wherein the ion exchange substitution reaction produces carbonic acid, and wherein the carbonic acid is decomposed to carbon dioxide gas that is separated from the seawater at a pH of less than about 6.5.

7. The method of claim 6 , further comprising the step of separating dihydrogen gas from water fed to the cathode compartment.

8. The method of claim 6 , further comprising the step of producing hydrocarbons from the carbon dioxide obtained in the carbon dioxide separation step.

9. The method of claim 7 , further comprising the step of producing hydrocarbons from the carbon dioxide obtained in the carbon dioxide separation step and the dihydrogen gas obtained from the water fed to the cathode compartment.

10. The method of claim 6 , wherein the carbon dioxide is separated from the seawater at a pH of less than about 6.5 by vacuum degassing.

11. The method of claim 7 , wherein the dihydrogen gas is separated from the water fed to the cathode compartment by vacuum degassing.

12. An electrolytic process for producing carbon dioxide and dihydrogen gas from seawater comprising:
feeding water into an anode compartment to generate hydrogen ions, wherein the water fed into the anode compartment has a conductivity less than 300 μS/cm;
feeding water substantially free of hardness ions into a cathode compartment;
feeding seawater comprising bicarbonate and carbonate ions into a central compartment, wherein the central compartment contains either no material or only inert media, and wherein the central compartment is between the anode and cathode compartments and separated from the anode and cathode compartments by cation exchange membranes;
exchanging the hydrogen ions produced from water in the anode compartment for sodium ions in the seawater to produce a seawater effluent from the central compartment, wherein the sodium ions transfer from the central compartment to the cathode compartment;
lowering a pH of the seawater entering the central compartment to less than about 6.5 using an electrically driven membrane process wherein seawater pH is inversely proportional to an applied current and independent of any media in the central compartment, wherein the pH is lowered in the central compartment;
reacting the sodium ions with hydroxyl ions in the cathode compartment to produce an effluent comprising sodium hydroxide and dihydrogen gas;
reacting the carbonate and bicarbonate ions in the seawater at a pH of less than about 6.5 with the hydrogen ions to produce carbon dioxide;
removing the carbon dioxide from the seawater at a pH of less than about 6.5 and removing dihydrogen gas from the cathode compartment effluent, wherein there is a controllable molar ratio of carbon dioxide to dihydrogen gas; and
controlling the molar ratio of carbon dioxide to dihydrogen gas in part by varying the applied current density.

13. The process of claim 12 , wherein the seawater fed to the central compartment has a pH greater than or equal to 7.5.

14. The process of claim 12 , further comprising combining the seawater effluent from the central compartment with the effluent from the cathode compartment to increase the pH of the effluent from the central compartment.

15. The process of claim 12 , wherein feeding the seawater into the central compartment is at a velocity of 20 to about 500 cm/min.

16. The process of claim 12 , wherein the electrolytic process is at a current density ranging between about 5 to about 200 mA/cm 2 .

17. The process of claim 12 , further comprising providing an ion exchange resin in the anode compartment, the cathode compartment, or any combination thereof.

18. The process of claim 12 , wherein the seawater fed to the central compartment is filtered to less than 20 microns.

19. The process of claim 12 , further comprising periodically reversing flow of current to a cathode within the cathode compartment and an anode within the anode compartment.

20. The process of claim 19 , wherein periodically reversing flow of current to the cathode and anode comprises discontinuing current prior to reversing the flow of current.

21. The process of claim 19 , wherein the flow of current to the cathode and anode is reversed about every 20 to 120 minutes of operation.

22. The process of claim 19 , wherein periodically reversing flow of current to the cathode and anode comprises discontinuing current for about 10 seconds to about 5 minutes prior to reversing the flow of current.

23. The process of claim 12 , wherein the water fed into the anode compartment, the water fed into the cathode compartment, or both has a conductivity of less than 300 μS/cm.

24. The process of claim 12 , wherein removing the carbon dioxide from the seawater effluent from the central compartment, removing dihydrogen gas from the cathode compartment effluent, or both comprises applying a vacuum.

25. The process of claim 24 , wherein the vacuum applied is −30 in Hg.

26. The process of claim 12 , further comprising producing hydrocarbons from the carbon dioxide and dihydrogen gas.

27. The process of claim 12 , further comprising extracting carbon dioxide and dihydrogen gas at a molar ratio of 1 to 2.

Assignees

• Dimascio Felice
• Hardy Dennis R
• Lewis M Kathleen
• Willauer Heather D
• Williams Frederick
• Us Navy

Inventors

• Dimascio Felice
• Hardy Dennis R
• Lewis M Kathleen
• Willauer Heather D
• Williams Frederick

Classifications

• C10G2300/42

  Hydrogen of special source or of special composition · CPC title

• C25B15/08

  Supplying or removing reactants or electrolytes; Regeneration of electrolytes · CPC title

• C25B15/02

  Process control or regulation · CPC title

• C10G2400/08

  Jet fuel · CPC title

• Y02W10/37

  using solar energy · CPC title