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CA-3241348-C - ELECTROCHEMICAL REDUCTION OF NITROGEN TO AMMONIA CATALYZED BY POLYOXOMETALATES

CA3241348CCA 3241348 CCA3241348 CCA 3241348CCA-3241348-C

Abstract

This invention is directed to a method of electrocatalytic reduction of dinitrogen (N2) to ammonia using a poly oxometalate catalyst, an alkali metal cation and a donor of a proton and/or an electron.

Inventors

  • Ronny Neumann
  • Avra TZAGUY

Assignees

  • YEDA RESEARCH AND DEVELOPMENT CO. LTD

Dates

Publication Date
20260505
Application Date
20221130
Priority Date
20211202

Claims (20)

  1. CLAIMS What is claimed is: 1. A method for the preparation of ammonia (NH3), wherein the method comprising: an electrochemically reducing dinitrogen (N2) in an electrochemical cell in the presence of a polyoxometalate catalyst, an alkali metal cation and a donor of a proton and/or an electron.
  2. 2. The method of claim 1 wherein the polyoxometalate catalyst comprises iron.
  3. 3. The method of claim 1 wherein the polyoxometalate catalyst comprises the general formula (Q)n[XFe2M(L)3W9O37] or solvate thereof wherein: X is a group 13, 14, or 15 atom; M is a metal; L comprises an atom associated with M; Q is a cation; and n is an integer 3 to 17.
  4. 4. The method of claim 3 wherein, X is P, Si, As, Ge, Ga, B, or Al; M is Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, Sc, Mg, Y, Ba, or Ca; L is H2O, carboxylate, oxyanion, a halide, a pseudohalide, null or any combination thereof; Q is a cation; and n is an integer 3 to 17.
  5. 5. The method of claim 3 or claim 4 wherein Q is a proton, an alkali metal cation, an alkaline earth metal cation, a lanthanide cation, a nitrogen centered cation, a phosphorous centered cation and combinations thereof.
  6. 6. The method of claim 3 wherein [XFe2M(L)3W9O37] is [SiFe3(L)3W9O37].
  7. 7. The method of any one of claims 1-6 further comprising an electrolyte.
  8. 8. The method of any one of claims 1-7 further comprising a solvent.
  9. 9. The method of any one of claims 1-7 wherein the reduction of dinitrogen (N2) is conducted with no solvent.
  10. 10. The method of claim 7 wherein the electrolyte comprises a lithium salt, a sodium salt, a potassium salt or a quaternary ammonium salt.
  11. 11. The method of claim 10 wherein the electrolyte comprises a salt of a lithium, a sodium, a potassium or a quaternary ammonium cation; and halide, a pseudohalide, perchlorate, bis( trifluoromethy lsulfony 1 )imide, tetrafluoroborate, hexafluorophosphate or triflate anion, or an oxyanion.
  12. 12. The method of any one of claims 1-11 wherein the alkali metal cation is provided as an alkali metal salt comprising lithium, sodium, potassium, rubidium or cesium cation; and halide, pseudohalide, perchlorate, bis(trifluoromethylsulfonyl)imide, tetrafluoroborate, hexafluorophosphate or triflate anion, or an oxyanion.
  13. 13. The method of any one of claims 1-12 wherein the donor of a proton and/or an electron is water.
  14. 14. The method of any one of claims 1-13 wherein the molar ratio of the alkali metal cation and the polyoxometalate catalyst is at least 3 moles of alkali metal cation per 1 mole ofpolyoxometalate catalyst.
  15. 15. The method of any one of claims 1-14 wherein the electrochemical reduction of dinitrogen (N2) is carried out at a potential being <0 V vs. SHE
  16. 16. The method of any one of claims 1-15 wherein the electrochemical reduction of dinitrogen (N2) is carried out under air or nitrogen enriched air.
  17. 17. The method of any one of claims 1-16 wherein the electrochemical reduction of dinitrogen (N2) is carried out with purified nitrogen.
  18. 18. The method of any one of claims 1-17 wherein the electrochemical reduction of dinitrogen (N2) is carried out at 0.1-50 bar N2.
  19. 19. The method of any one of claims 1-18 wherein the electrochemical reduction of dinitrogen (N2) is carried out at 0.1-10 bar N2.
  20. 20. The method of any one of claims 1-19 wherein the electrochemical reduction of dinitrogen (N2) is carried out at 0.1-5 bar N2.

Description

ELECTROCHEMICAL REDUCTION OF NITROGEN TO AMMONIA CATALYZED BY POLYOXOMETALATES FIELD OF INVENTION [001] This invention is directed to a method of electrocatalytic reduction of nitrogen to ammonia using a polyoxometalate catalyst in the presence of an alkali metal cation and a donor of a proton and/or an electron. BACKGROUND OF THE INVENTION [002] Humankind is dependent on the manufacture of ammonia and its derivatives as fertilizers for food production. The dinitrogen to ammonia Haber-Bosch (H-B) process is therefore said to be the most important invention of the 20th century (Smith, C; Hill, A K.; Torrente-Murciano, L. Current and Future Role of Haber-Bosch Ammonia in a Carbon-Free Energy Landscape. Energy Environ. Sci. 2020, 13, 331-344. The highly optimized heterogeneous catalytic process, N2 + 3H2-----* 2NH3, is only feasible at high temperatures (-700 K) and pressures (-200 bar) using very high purity N2 and H2 (Schlogl, R. in Handbook of Heterogeneous Catalysis 2501-2575 (Wiley-VCR Verlag GmbH & Co. KGaA, 2008). The needed H2 is produced via steam reforming from natural gas and it is estimated that -1 % of the world's energy consumption and 1 .4% of global CO2 emissions are related to the H-B process (MacFarlane, D. R.; Cherepanov, P. V.; Choi, J.; Suryanto, B. H. R.; Hodgetts, R. Y.; Bakker, J. M.; Ferrero Vallana, F. M.; Simonov, AN. A Roadmap to the Ammonia Economy. Joule 2020, 4, 1185-1205). Thus, NH3 is produced at locations where natural gas is plentiful but not necessarily where the end-users are located. Based on the future availability of renewable electricity two options have been put forward to replace the traditional H-B process. The hybrid-H-B approach uses H2 from water electrolysis for H-B NH3 synthesis, which obviates the use of natural gas and reduces the overall carbon footprint leading to decarbonization of the process. [003] The other option, electrocatalytic NH3 synthesis ( e-NH3 ), proceeds via an electrochemical Nitrogen Reduction Reaction (e-N2RR) obtaining the needed protons and electrons from water oxidation. In contrast to the hybrid-H-B, e-N2RR is thermodynamically favourable at ambient conditions and a catalytic reaction can be feasible under much more benign conditions. In fact, 1 the nitrogenase enzyme complex reduces N2 to NH3 albeit quite inefficiently using 16 equivalents of ATP (Adenosine triphosphate) per N2 molecule (Hoffman, B. M.; Lukoyanov, D.; Yang, Z.Y.; Dean, D.R.; Seefeldt, L. C. Mechanism of Nitrogen Fixation by Nitrogenase: The Next Stage. Chem. Rev. 2014, 114, 4041- 4062). An economic analysis of hybrid H-B and e-NH3 approaches shows that while the former can be economically feasible in a large production scale, e-NH3 can outperform it in a small production scale (-0.03 tonNm/day) (Fernandez, C. A; Hatzell, M. C. Economic Considerations for Low-Temperature Electrochemical Ammonia Production: Achieving Haber-Bosch Parity. J. Electrochem. Soc. 2020, 167, 143504). Climate benefits of eNH3 include reduced carbon footprint associated with reduced maritime and overland transportation, reduced storage needs, enhanced ability to follow the intermittent electrical power input, and use of nitrogen with reduced purity. Together all these factors make decentralized ammonia production an attractive long-term option (Soloveichik, G. Electrochemical synthesis of ammonia as a potential alternative to the Haber-Bosch process. Nat. Cata!. 2019, 2, 377-380). [004] On-site, on-demand NH3 production will also improve decarbonization of agricultural and shipping sectors in and be more resistant against political-economic risks, which can decrease the availability of ammonia especially in rural areas (Arora, P.;Hoadley, A F. A; Mahajani, S. M; Ganesh, A Small-Scale Ammonia Production from Biomass: A Techno-Enviro-Economic Perspective. Ind Eng. Chem. Res. 2016, 55, 6422-6434). [005] Despite the advances toward both understanding N2 activation and NH3 formation, electrocatalytic reduction to NH3, (electro) catalyst development is still very much lagging behind (Chalkley, M. J.; Drover, M. W.; Peters, J.C. Catalytic N2-to-NH3 (or-N2H4) Conversion by Well-Defined Molecular Coordination Complexes. Chem. Rev. 2020, 120, 5582-5636). [006] It should also be noted that previous reports of e-N2RR reactions carried out in water as solvent and electron/proton donor, however, have been shown to be incorrect (Anderson, S. Z.; Coloci, V.; Yang, S.; Schwalbe, J. A; Nielander, AC.; McEnaney, J.M.; Enemark-Rassmussen, K.; Baker, J. G.; Singh, A R.; Rohr, B. A; Start, M. J.; Blair, S. J.; Mezzavilla, S.; Kibsgaard, J.; Vesborg, R. C. K.; Cargnello, M.; Bent, S. F.; Jaramillo, T. F.; Stephens, I.E. L.; N0rskov, J. K.; Chorkendorff, I. A rigorous electrochemical ammonia synthesis protocol with quantitative isotope measurements. Nature, 570, 504-508 (2019). [007] Polyoxometalates are attractive as catalysts because they are easy to synthesize, thermally and oxidatively stable, their intrinsic proper