254th ACS Meeting, Energy and Fuels Symposium “The Ammonia Economy” — Synthesis, Utilization & Nitrogen Reduction

A guest editorial by Michael Mock, Pacific Northwest National Laboratory, US.

In late August, the day before the exciting solar eclipse, the Ammonia Economy symposium was held as part of the Energy and Fuels Division of the American Chemical Society (ACS) National Meeting in Washington DC. This marks the third gathering of Ammonia related research since 2015 at the national level ACS conference. This year, in addition to the important focus on chemistries for the utilization of ammonia, which filled the morning session, the rapidly developing field of homogeneous catalysts and biological processes for nitrogen fixation was included as a major theme.

The afternoon session included several talks discussing homogeneous transition metal complexes for N₂ reduction to NH₃, biological N₂ reduction by nitrogenase, and recent engineering advances and challenges in running a carbon-neutral NH₃ production facility.

Professor John Berry from the University of Wisconsin-Madison started the session by discussing the fundamental bonding and reactivity of a novel metal-metal bonded Ru-nitride complex. In the pursuit of electrocatalysts for ammonia oxidation, he described the loss of N₂ in this bimetallic system by a nitride-nitride coupling reaction.

The next presentation was given by Dr. Simone Raugei at Pacific Northwest National Laboratory (PNNL), in which he highlighted recent experimental and computational results toward understanding the fast electron and proton transfer reactions that occur during the intricate mechanism of N₂ and CO₂ reduction by nitrogenase. The next two talks were also contributed by scientists at PNNL. First, Dr. Alexander Kendall discussed the development of molecular chromium complexes to cleave the N₂ triple bond in the catalytic silylation of N₂ to N(SiMe₃)₃. While NH₃ is not produced directly in this reaction, the subsequent treatment of N(SiMe₃)₃ with acid affords NH₃ quantitatively. Dr. Michael Mock then presented related work on homogeneous silylation catalysis using a molecular Fe complex; and concluded the talk by discussing a strategy to cleave the N-H bonds of NH₃ at Mo by hydrogen atom abstraction reactions using organic radicals.

Lastly, Dr. Mahdi Malmali from University of Minnesota provided a thought-provoking presentation on carbon-neutral NH₃ synthesis using renewable energy sources (hydrogen from electrolysis and nitrogen from pressure swing adsorption of air) at low N₂ pressures. Engineering challenges associated with running a scaled down NH₃ synthesis process (compared to a typical Haber-Bosch plant) and recent advances in supported absorbents rounded out the discussion.

Researchers interested in learning more about research activities in the study of ammonia (and hydrazine) as a fuel or energy carrier, may be interested in attending the 233rd Electrochemical Society (ECS) meeting, which will take place in Seattle, WA, May 13-17, 2018.

A symposium entitled, “Energy Conversion Systems Based on Nitrogen” will include the topics of

1. Using electrical energy to reduce N₂ directly to NH₃
2. electrochemical decomposition of NH₃ to produce H₂
3. direct carbon-free (e.g, NH₃, N₂H₄) fuel cells
4. electrochemically promoted biomass conversion.

For more information please visit the Electrochemical Society website or find out how to submit your abstract for the conference (deadline: Friday November 17).

A guest editorial by Michael Mock, Pacific Northwest National Laboratory, US.