EP-4739819-A1 - PROCESS FOR ELECTROLYTIC PRODUCTION OF AMMONIA FROM NITROGEN USING METAL CARBONITRIDE CATALYSTS

Abstract

The invention relates to a process and system for electrolytic production ammonia. The process comprises feeding nitrogen to an electrolytic cell, where it comes in contact with a cathode surface, wherein said surface has a catalyst surface comprising at least one transition metal carbonitride, the electrolytic cell further comprising a proton donor, and running a current through said electrolytic cell, whereby nitrogen reacts with protons to form ammonia.

Inventors

• SKÚLASON, Egill
• ABGHOUI, Younes
• IQBAL, Atef
• FLOSADÓTTIR, Helga Dögg

Assignees

• Atmonia EHF.

Dates

Publication Date

20260513

Application Date

20240702

Claims (1)

1. P15459PC00 CLAIMS 1. A process for producing ammonia comprising: a. feeding N 2 to an electrolytic cell that comprises a cathode, an anode, an electrolyte and at least one source of protons, b. allowing the N 2 to come into contact with at an electrode surface of the cathode in the electrolytic cell, wherein said electrode surface comprises at least one catalyst surface selected from the group consisting of: Vanadium carbonitride, Niobium carbonitride, Tungsten carbonitride, Titanium carbonitride, Tantalum carbonitride, Hafnium carbonitride, Molybdenum carbonitride, Chromium carbonitride, Scandium carbonitride, Yttrium Carbonitride and Zirconium carbonitride, and, c. running a current through said electrolytic cell, whereby nitrogen reacts with protons to form ammonia. 2. The process according to claim 1, wherein the catalyst surface comprises one or more transition metal carbonitrides selected from the group consisting of Vanadium carbonitride, Niobium carbonitride and Tungsten carbonitride. 3. The process according to any one of the preceding claims, wherein the at least one catalyst comprises a Rocksalt structure. 4. The process according to any one of the preceding claims, wherein the catalyst surface comprises at least one surface having a (100) facet. 5. The process according to any one of the preceding claims, wherein the catalyst surface comprises at least one nitrogen vacancy and/or carbon vacancy. 6. The process according to any of the preceding claims, wherein ammonia is formed in the electrolytic cell at an electrode potential at less than about -1.0 V, more preferably less than about -0.6 V and even more preferably less than about -0.3 V using a reversible hydrogen electrode (RHE) as a reference. 7. The process according to any one of claims 1 to 6, wherein a cyclic varied potential is used that fluctuates between an active potential and a resting potential to generate a cyclic varied potential through the electrolytic cell. P15459PC00 8. The process according to any one of the preceding claims, wherein less than 50% moles H 2 are formed compared to moles NH 3 formed, and preferably less than 20% and even more preferably less than 10%. 9. The process according to any one of the preceding claims, wherein said electrolytic cell comprises one or more aqueous electrolytic solution. 10. The process according to any one of the preceding claims, wherein the source of protons in the formation of ammonia is from water splitting at the anode or H 2 oxidation reaction in the anode. 11. The process according to any one of the preceding claims, wherein the electrolytic cell comprises an anode within one cell compartment and a cathode within another cell compartment. 12. The process according to any one of the preceding claims, wherein the process is carried out at a temperature in the range from about -10°C to about 80°C, preferably in a range from about 10°C to about 50°C, more preferably in the range from about 20°C to about 30°C, even more preferably in the range from about 20°C to about 25°C. 13. The process according to any one of the preceding claims, wherein the process is carried out at atmospheric pressure. 14. The process according to any one of claims 1-12, wherein the process is carried out at a pressure in the range of 1 to 30 atmospheres, preferably in the range of 1-20 atmospheres, preferably in the range of 1-10 atmospheres, more preferably in the range of 1-5 atmospheres. 15. The process according to any of the preceding claims, wherein said feeding N2 to the electrolytic cell comprises feeding gaseous nitrogen or air or liquid with dissolved nitrogen to the electrolytic cell. 16. A system for generating ammonia, the system comprising at least one electrochemical cell, which comprises at least one cathode having at least one catalytic surface, wherein the at least one catalytic surface comprises at least one catalyst selected from the group consisting of: Vanadium carbonitride, Niobium carbonitride, Tungsten P15459PC00 carbonitride, Titanium carbonitride, Tantalum carbonitride, Hafnium carbonitride, Molybdenum carbonitride, Chromium carbonitride, Yttrium carbonitride, Scandium carbonitride and Zirconium carbonitride. 17. The system according to claim 16, wherein said at least one catalyst is selected from the group consisting of Vanadium carbonitride, Niobium carbonitride and Tungsten carbonitride. 18. The system according to any one of claims 16 to 17, wherein the at least one catalyst comprises a Rocksalt structure. 19. The system according to any one of claims 16 to 18, wherein the catalyst surface comprises at least one surface having a (100) facet. 20. The system according to any one of claims 16 to 19, wherein said electrolytic cell further comprises one or more electrolytic solution, preferably an acidic, neutral or alkaline aqueous solution. 21. The system according to claim 20, wherein the electrolytic solution comprises an aqueous water-miscible organic solvent. 22. The system according to any one of claims 16 to 21, wherein the electrolytic cell comprises an anode within one cell compartment and a cathode within another cell compartment. 23. The system according to any one of claims 16 to 22, wherein ammonia is formed in the electrolytic cell at an electrode potential at less than about -1.0 V, more preferably less than about -0.6 V and even more preferably less than about -0.3 V using a reversible hydrogen electrode (RHE) as a reference. 24. The system according to any one of claims 16 to 23, wherein a cyclic varied potential is used that fluctuates between an active potential and a resting potential to generate a cyclic varied potential through the electrolytic cell.

Description

P15459PC00 PROCESS FOR ELECTROLYTIC PRODUCTION OF AMMONIA FROM NITROGEN USING METAL CARBONITRIDE CATALYSTS FIELD OF INVENTION The disclosure is within the field of process chemistry, and specifically relates to the catalytic production of ammonia from nitrogen with electrolytic methods using novel transition metal carbonitride catalysts for the cathode surface. BACKGROUND Ammonia is a high value chemical owing to its use in fertilizers, with an annual production of 175 million tonnes, but its potential as an energy storage material and a carbon-free maritime fuel have recently gained attention. For more than a century, ammonia has been produced via the Haber-Bosch process, in which nitrogen and hydrogen gases react over a promoted Fe/Ru catalyst at a temperature exceeding 400°C and pressure upwards of 150 bar; N2(g) + 3H2(g) → 2NH3(g) This leads to substantial carbon emissions, owing mostly to the production of hydrogen gas via steam reforming, but also to the extreme reaction conditions rendering the process highly energy consuming. These are in stark contrast to the ambient conditions at which the enzyme nitrogenase in bacteria naturally catalyses nitrogen reduction from solvated protons, electrons and atmospheric nitrogen; N2(g) + 8H+ + 8e- → 2NH3(g) + H2(g) This natural process of nitrogen fixation has inspired the search and development of catalysts that can work at (much milder) ambient conditions. However, as is common knowledge, the search for a suitable catalyst for a specific reaction is both challenging and complex, wherein a search needs to be based on factors such as availability, cost, stability, activity, and selectivity of the catalyst material under the desired operational conditions. In particular, the realisation of the electrochemical nitrogen reduction reaction (NRR) using solid catalytic electrodes in an aqueous solution, with the protons coming from water splitting at the anode, has been an active field of research, both computationally and experimentally [1]. Despite the research interest and recent efforts, little progress has been made in finding a suitable catalyst for NRR with the main culprit being the competing hydrogen evolution reaction (HER), as most of the materials that are active towards the NRR are more selective towards HER, especially at higher overpotentials. This leads to extremely low Faradaic efficiencies, i.e., most of the P15459PC00 electrical energy supplied to the system is being wasted on the HER rather than being utilized for the NRR. To emphasize the challenge of finding a suitable NRR catalyst, a few examples from the literature and from previous efforts by the applicants are discussed below. Out of the pure transition metals, namely, Sc, Y, Ti, Zr Re, Os, Co, Ru, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, V, Nb, Ta, Cr, Mo, W, and Fe it has been predicted (with computational studies) that none of the pure transition metals is capable of catalysing the NRR because of the facile H2 formation. [2] The linear scaling relations of adsorption energies for the pure metals in the periodic table predict that they are not able to catalyse this reaction. Some of these predictions have been verified in experiments, namely for Ru, Rh and Re, with strict protocols used to avoid false positive results. [3] In fact, it is safe to say that efficient ammonia synthesis in an aqueous solution verified with strict experimental protocols remain a challenge, with the literature littered with likely false positives [3,4,5]. Recent efforts by the present applicants have focused on novel ceramics materials, i.e., using transition metal nitride (TMN), transition metal oxide (TMO) and transition metal sulphide (TMS) catalyst surfaces, as disclosed in WO2015189865, WO2019053749 and WO2020110155, respectively. Despite these efforts, most investigated materials still catalyse HER over NRR. The identification of a promising catalyst is one of the steps needed to realise electrochemical NRR at low to moderate overpotentials. The present invention seeks to ameliorate these problems by providing novel catalyst compounds capable of catalysing the electrochemical nitrogen reduction reaction (NRR) at mild operational conditions such as in an aqueous solution, using low to moderate overpotentials/voltage. References: [1] Guo, W., Zhang, K., Liang, Z., Zou, R., and Xu, Q. (2019). Electrochemical nitrogen fixation and utilization: theories, advanced catalyst materials and system design. Chem. Soc. Rev.48, 5658-5716. [2] Skúlason, E., Bligaard, T., Gudmundsdóttir, S., Studt, F., Rossmeisl, J., Abild-Pedersen, F., Vegge, T., Jónsson, H., and Nørskov, J.K. (2012). A theoretical evaluation of possible transition metal electro-catalysts for N2 reduction. Phys. Chem. Chem. Phys.14, 1235-1245. [3] Andersen, S.Z., Colic, V., Yang, S., Schwalbe, J.A., Nielander, A.C., McEnaney, J.M., Enemark-Rasmussen, K., Baker, J.G., Singh, A.R., Rohr, B.A., et al. (2019). A rigorous P15459PC00 electrochemical ammonia synthesi