CONVERSION OF CARBON DIOXIDE TO ORGANIC PRODUCTS

• US 20100187123A1
• Filed: 01/29/2010
• Published: 07/29/2010
• Est. Priority Date: 01/29/2009
• Status: Active Grant

• Current Assignee: Princeton University
• Original Assignee: Princeton University
• Inventors: Bocarsly, Andrew B., Cole, Emily Barton
• Granted Patent: US 8,313,634 B2
• Time in Patent Office: Days
• US Class Current: 205/340
• CPC Class Codes: C25B 1/55 Photoelectrolysis
• CPC Class Codes: C25B 3/25 Reduction
• CPC Class Codes: C25B 9/19 with diaphragms
• CPC Class Codes: Y02P 20/133 Renewable energy sources, e.g. sunlight

Abstract

The invention relates to various embodiments of an environmentally beneficial method for reducing carbon dioxide. The methods in accordance with the invention include electrochemically or photoelectrochemically reducing the carbon dioxide in a divided electrochemical cell that includes an anode, e.g., an inert metal counterelectrode, in one cell compartment and a metal or p-type semiconductor cathode electrode in another cell compartment that also contains an aqueous solution of an electrolyte and a catalyst of one or more substituted or unsubstituted aromatic amines to produce therein a reduced organic product.

Claims

1. A method of converting of carbon dioxide to provide at least one product, comprising reducing the carbon dioxide in a divided electrochemical cell comprising an anode in one cell compartment and a cathode electrode in another cell compartment and one or more substituted or unsubstituted aromatic heterocyclic amines, each compartment containing an aqueous solution of an electrolyte.

2. The method of claim 1, wherein the reducing is electrochemical or photoelectrochemical.

3. The method of claim 2 wherein the reducing is electrochemical and the cathode is a metal.

4. The method of claim 3, wherein the metal is Au, Ag, Zn, Ga, Hg, In, Cd, Ti, Pd or Pt.

5. The method of claim 4, wherein the cathode is Pt or hydrogenated Pd.

6. The method of claim 2, wherein the reducing is photoelectrochemical and the cathode is a p-type semiconductor responsive to illumination.

7. The method of claim 6, wherein the semiconductor is p-GaP, p-GaAs, p-InP, p-InN, p-WSe₂, p-CdTe, p-GaInP₂ or p-Si.

8. The method of claim 6, wherein energy is provided to the cell by illuminating the cathode with light energy.

9. The method of claim 1, wherein aromatic heterocyclic amine catalyst is represented by formula 1:

wherein the ring structure W is an aromatic 5- or 6-member heterocylic ring with at least one ring nitrogen and is optionally substituted at one or more ring positions other than nitrogen with R, and

wherein L is C or N, R¹ is H, R² is H if L is N or R² is R if L is C, and R is an optional substitutent on any ring carbon and is independently selected from H, straight chain or branched chain lower alkyl, hydroxyl, amino, pyridyl, or two R'"'"'s taken together with the ring carbons to which they are bonded are a fused six-member aryl ring, and n=0 to 4.

10. The method of claim 9, wherein the aromatic heterocyclic amine catalyst is represented by formula 2:

wherein R³ is H;

R⁴, R⁵, R⁷ and R⁸ are independently H, straight chain or branched chain lower alkyl, hydroxyl, amino, or taken together are a fused six-member aryl ring, and R⁶ is H, straight chain or branched chain lower alkyl, hydroxyl, amino or pyridyl.

11. The method of claim 5, wherein the amine of formula 1 is a lower alkyl substituted pyridine, a lower alkyl amino substituted pyridine, an unsubstituted bipyridine, a lower alkyl substituted bipyridine, hydroxy-pyridine, hydroxy-bipyridine, or lower alkyl amino substituted bipyridine.

12. The method of claim 7, wherein the amine is tertbutyl-pyridine, dimethyl-pyridine, 2,6-lutidine, 2-methylpyridine, 4-methylpyridine, dimethylamino-pyridine, 4-hydroxypyridine, or 4,4′

-bipyridine.

13. The method of claim 9, wherein the aromatic heterocyclic amine is represented by formula 3:

wherein one of L¹, L² or L³ is N and the other L'"'"'s are C, R⁹ is H, if L¹ is N, then R¹⁹ is H, if L² is N, then R¹¹ is H, and if L³ is N, then R¹² is H; and

if L⁴, L² or L³ is C, then R¹⁰, R¹¹, R¹², R¹³ and R¹⁴ are independently selected from straight chain or branched chain lower alkyl, hydroxyl, amino, or pyridyl.

14. The method of claim 13, wherein the aromatic heterocyclic amine is a pyrazine, a pyridazine or a pyrimidine.

15. The method of claim 9, wherein the aromatic heterocyclic amine is represented by formula 4:

wherein L⁵ is N or C, R¹⁵ is H, R¹⁶ is H if L⁵ is N, or if L⁵ is C, R¹⁶, R¹⁷, R¹⁸, R¹⁹ are independently selected from straight chain or branched chain lower alkyl, hydroxyl, amino, or pyridyl, or R¹⁷ and R¹⁸ taken together with the ring carbons to which they are bonded are a fused 6-member aryl ring.

16. The method of claim 15, wherein the aromatic heterocyclic amine is an imidazole or a pyrole.

24. The system of claim 1, wherein the substituted or unsubstituted aromatic heterocyclic amines are represented by formula 1:

wherein the ring structure W is an aromatic 5- or 6-member heterocyclic ring with at least one ring nitrogen and is optionally substituted at one or more ring positions other than nitrogen with R, and

wherein L is C or N, R¹ is H, R² is H if L is N or R² is R if L is C, and R is an optional substitutent on any ring carbon and is independently selected from H, straight chain or branched chain lower alkyl, hydroxyl, amino, pyridyl, or two R'"'"'s taken together with the ring carbons to which they are bonded are a fused six-member aryl ring, and n=0 to 4.

27. The method of claim 1, which further comprises obtaining the carbon dioxide from an exhaust stream from a fossil fuel burning power or industrial plants, from a source accompanying natural gas or from geothermal wells.

28. The method of claim 1, wherein electrical energy for the electrochemical reduction of carbon dioxide is provided from a conventional energy source based on nuclear, hydroelectric, wind, geothermal or solar power.

17. A system for electrochemical or photoelectrochemical reduction of carbon dioxide to produce at least one product, comprising:

an electrochemical cell including a first compartment containing an anode, and a second compartment having a cathode which is a metal or p-type semiconductor, and a catalyst which is a substituted or unsubstituted aromatic heterocyclic amine;

both compartments containing an aqueous electrolyte

a source for providing carbon dioxide to the cathode; and

an energy source supplied to the cell to reduce the carbon dioxide

18. The system of claim 17, wherein the metal is Au, Ag, Zn, Ga, Hg, In, Cd, Ti, Pd or Pt.

19. The system of claim 18, wherein the cathode is Pt or hydrogenated Pd.

20. The system of claim 17, wherein the reduction is photoelectrochemical and the cathode is a p-type semiconductor responsive to illumination.

21. The system of claim 20, wherein the semiconductor is p-GaP, p-GaAs, p-InP, p-InN, p-WSe2, p-CdTe, p-GaInP₂ or p-Si.

22. The system of claim 17, wherein energy is provided to the cell by illuminating the cathode with light energy.

23. The system of claim 17, wherein the light energy is converted to electrical energy.

25. The system of claim 17, wherein the amine of formula 1 is a lower alkyl substituted pyridine, a lower alkyl amino substituted pyridine, an unsubstituted bipyridine, a lower alkyl substituted bipyridine, a hydroxy-pyridine, hydroxy-bipyridine, lower alkyl amino substituted bipyridine, an unsubstituted or substituted quinoline or isoquinoline, an unsubstituted or substituted imidazole or benzimidazole, or a substituted or unsubstituted pyrole.

26. The system of claim 17, where the at least one product is methanol, isopropanol, formic acid, formaldehyde, glyoxal or ethanol.

29. An environmentally beneficial method of producing methanol by electrochemical or photoelectrochemical reduction of any available source of carbon dioxide, which comprises:

providing a divided electrochemical cell comprising an anode in a first cell compartment and a cathode electrode in a second cell compartment that also contains a catalyst which is one or more of a substituted or unsubstituted aromatic heterocyclic amine, both compartments containing an aqueous solution of an electrolyte,

providing carbon dioxide from an existing source into the second cell compartment;

electrochemically or photoelectrochemically reducing the carbon dioxide in the second cell compartment to produce methanol to reducing atmospheric carbon dioxide.