Process for the production of ammonia from air and water

Patent metadata

Field	Value
Publication number	US-10982339-B2
Application number	US-201515305604-A
Country	US
Kind code	B2
Filing date	Apr 24, 2015
Priority date	Apr 25, 2014
Publication date	Apr 20, 2021
Grant date	Apr 20, 2021

Abstract

The present disclosure relates to a simple one-pot process for the production of ammonia. The process involves electrolysis of air and water using a molten or concentrated aqueous hydroxide electrolyte in the presence of an iron catalyst. The process exhibits one or more of the following benefits: (i) it is an efficient, cost-effective low-energy process, (ii) it eliminates carbon dioxide (CO2) evolution, (iii) it eliminates the need for a separator, and (iv) it bypasses the need for a preliminary hydrogenation step.

First claim

What is claimed is:

1. A process for the production of ammonia comprising
electrolysis of air and water between an anode and a cathode in a molten hydroxide electrolyte or an aqueous hydroxide electrolyte, the electrolyte comprising iron or an iron oxide, wherein the iron or iron oxide has (i) a Brunauer-Emmett-Teller surface area greater than about 10 m 2 /g and/or (ii) an average particle size of less than about 5000 nm, wherein the process is conducted above the supercritical point of water, and
wherein the molten hydroxide electrolyte or the aqueous hydroxide electrolyte further comprises one or more alkali metal carbonates, alkali earth metal carbonates, alkali metal oxides, alkali earth metal oxides, alkali metal halides, alkali earth metal halides, alkali metal sulfates, alkali earth metal sulfates, alkali metal nitrates, alkali earth metal nitrates, alkali metal halates, alkali earth metal halates, or any combination thereof.

2. The process of claim 1 , wherein carbon dioxide is not formed during the process.

3. The process according to claim 1 , wherein the molten hydroxide electrolyte or the aqueous hydroxide electrolyte is selected from alkali metal hydroxides, alkali earth metal hydroxides, and any combination thereof.

4. The process according to claim 1 , wherein the molten hydroxide electrolyte or the aqueous hydroxide electrolyte is selected from lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, and any combination thereof.

5. The process according to claim 1 , wherein the molten hydroxide electrolyte or the aqueous hydroxide electrolyte comprises sodium hydroxide and potassium hydroxide.

6. The process according to claim 5 , wherein the molar ratio of sodium hydroxide to potassium hydroxide is about 1:1.

7. The process according to claim 1 , wherein the melting point of the molten hydroxide electrolyte or the aqueous hydroxide electrolyte is between about 25° C. and about 300° C.

8. The process according to claim 1 , wherein the electrolysis is conducted at an applied current density of between about 0.5 mA cm −2 and about 2000 mA cm −2 .

9. The process according to claim 1 , wherein the anode and cathode each, independently comprises iron, zinc, aluminum, magnesium, bismuth, vanadium, manganese, nickel, silver, barium, calcium, strontium, lead, mercury, cadmium, chromium, tin, titanium, or any combination thereof.

10. The process according to claim 1 , wherein the anode and cathode both comprise nickel.

11. The process according to claim 1 , wherein the process is conducted at a nitrogen gas partial pressure of between about 1 bar and about 100 bar.

12. The process according to claim 1 , wherein the chemistry of the process can be expressed by equations (i), (ii), (iii) and (iv):
cathode: Fe 2 O 3 +3H 2 O+6 e −→2 Fe+6OH −   (i)

chemical: 2Fe+3H 2 O+N 2 →2NH 3 +Fe 2 O 3   (ii)

anode: 6OH −→3/2 O 2 (g)+3H 2 O+6 e −   (iii)

net: N 2 +3H 2 O→2NH 3 +3/2O 2   (iv).

13. The process according to claim 1 , wherein the melting point of the molten hydroxide electrolyte is between about 100° C. and about 300° C.

14. The process according to claim 1 , wherein the melting point of the molten hydroxide electrolyte is between about 150° C. and about 250° C.

15. The process according to claim 1 , wherein the electrolysis is conducted at an applied current density of between about 0.5 mA cm −2 and about 200 mA cm −2 .

16. The process according to claim 1 , wherein the iron or iron oxide has an average particle size less than about 200 nm.

17. The process according to claim 1 , wherein the melting point of the molten hydroxide electrolyte is about 170° C., about 195° C., about 200° C., about 215° C. or about 225° C.

18. The process according to claim 1 , wherein the aqueous hydroxide electrolyte has a molality between about 8 m and about 18 m.

19. A process for the production of ammonia comprising
electrolysis of air and water between an anode and a cathode in a molten hydroxide electrolyte comprising iron or an iron oxide, wherein the iron or iron oxide has (i) a Brunauer-Emmett-Teller surface area greater than about 10 m 2 /g and/or (ii) an average particle size of less than about 5000 nm, wherein the process is conducted above the supercritical point of water.

20. The process of claim 19 , wherein carbon dioxide is not formed during the process.

21. The process according to claim 19 , wherein the molten hydroxide electrolyte is selected from alkali metal hydroxides, alkali earth metal hydroxides, and any combination thereof.

22. The process according to claim 19 , wherein the molten hydroxide electrolyte is selected from lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, and any combination thereof.

23. The process according to claim 19 , wherein the molten hydroxide electrolyte comprises sodium hydroxide and potassium hydroxide.

24. The process according to claim 23 , wherein the molar ratio of sodium hydroxide to potassium hydroxide is about 1:1.

25. The process according to claim 19 , wherein the molten hydroxide electrolyte further comprises one or more alkali metal carbonates, alkali earth metal carbonates, alkali metal oxides, alkali earth metal oxides, alkali metal halides, alkali earth metal halides, alkali metal sulfates, alkali earth metal sulfates, alkali metal nitrates, alkali earth metal nitrates, alkali metal halates, alkali earth metal halates, or any combination thereof.

26. The process according to claim 19 , wherein the melting point of the molten hydroxide electrolyte is between about 25° C. and about 300° C.

27. The process according to claim 19 , wherein the electrolysis is conducted at an applied current density of between about 0.5 mA cm −2 and about 2000 mA cm −2 .

28. The process according to claim 19 , wherein the anode and cathode each, independently comprises iron, zinc, aluminum, magnesium, bismuth, vanadium, manganese, nickel, silver, barium, calcium, strontium, lead, mercury, cadmium, chromium, tin, titanium, or any combination thereof.

29. The process according to claim 19 , wherein the anode and cathode both comprise nickel.

30. The process according to claim 19 , wherein the process is conducted at a nitrogen gas partial pressure of between about 1 bar and about 100 bar.

31. The process according to claim 19 , wherein the chemistry of the process can be expressed by equations (i), (ii), (iii) and (iv):
cathode: Fe 2 O 3 +3H 2 O+6 e −→2 Fe+6OH −   (i)

chemical: 2Fe+3H 2 O+N 2 →2NH 3 +Fe 2 O 3   (ii)

anode: 6OH −→3/2 O 2 (g)+3H 2 O+6 e −   (iii)

net: N 2 +3H 2 O→2NH 3 +3/2O 2   (iv).

32. The process according to claim 19 , wherein the process is conducted at a pressure of between about 50 bar and about 221 bar pressure water vapor.

33. The process according to claim 19 , wherein the process is conducted at a pressure of between about 100 bar and about 10,000 bar pressure of nitrogen gas.

34. The process according to claim 19 , wherein the melting point of the molten hydroxide electrolyte is between about 100° C. and about 300° C.

35. The process according to claim 19 , wherein the melting point of the molten hydroxide electrolyte is between about 150° C. and about 250° C.

3

Assignees

• C2Cnt Llc

Inventors

• Licht Stuart
• Cui Baochen
• Wang Baohui

Classifications

• C25B15/00

  Operating or servicing cells · CPC title

• C25B9/17

  Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof · CPC title

• C25B1/00 Primary

  Electrolytic production of inorganic compounds or non-metals · CPC title

• C01C1/02

  Preparation, {purification} or separation of ammonia · CPC title

• Y02P20/50

  Improvements relating to the production of bulk chemicals · CPC title