Mankind relies on ammonia in synthetic food fertilizers. However, the production of ammonia from nitrogen is extremely energy intensive and requires the use of transition metals.
Researchers at the Julius-Maximilians-Universität (JMU) in Würzburg, Bavaria, Germany, have now achieved the conversion of nitrogen to ammonium at room temperature and low pressure without the need for transition metals. This was announced by a research group led by JMU scientist Holger Braunschweig in the journal Chemistry of nature.
New box with tools for connecting nitrogen
Industrial ammonia production, the so-called Haber-Bosch process, requires high temperatures and pressures and is expected to consume approximately two percent of all energy produced on earth. This process also relies on elements of transition metals, relatively heavy and reactive atoms.
The key to both discoveries was the use of boron, the fifth lightest element, as the atom to which nitrogen binds. “After these two discoveries, it became clear that we had a very special system in our hands,” says Braunschweig.
Just add water
Although their system binds and converts nitrogen, only half of the puzzle pieces were in place. “We knew that completing the conversion of nitrogen to ammonia would be a great challenge, as it requires a complex sequence of chemical reactions that are often incompatible with each other,” explains the JMU professor.
The breakthrough came from the simplest reagents: the traces of water left in the sample were enough to stimulate a consistent reaction that took the team just one step away from the ammonium target. It was later discovered that key reactions could be performed using solid acid, allowing the reactions to proceed sequentially in a single reaction flask, all at room temperature.
Preparation of ammonium with beer
Realizing that the acidification stage of the process seemed to work even with simple reagents such as water, the team repeated the reaction using locally brewed Würzburger Hofbräu beer. To their delight, they were able to find the preammonium product in the reaction mixture.
“This experiment was partly a bit amusing, but it also shows how tolerant the system is to water and other compounds,” explains Dr. Marc-Andre Legare, the postdoctoral fellow who initiated the study. “The reduction of nitrogen to ammonia is one of the most important chemical reactions for mankind. This is undoubtedly the first time it has been made with beer, and it is particularly appropriate that it has been made in Germany,” said Dr. Ryan Duhurst, Akademischer Oberrat. and co-author of the study.
There is still a lot of work to be done
The reaction, while exciting, is still far from a truly practical process for the industrial production of ammonium. Ideally, it will be necessary to find a way to reform the active species to make the process energy efficient and economical.
However, the discovery is an exciting demonstration that lighter elements can handle even the greatest challenges in chemistry. “There’s still a lot to do here, but pine and other light elements have already surprised us so many times. They’re obviously capable of so much more,” says Holger Braunschweig.
A newly designed molecule binds nitrogen
Conversion of nitric chloride to ammonium chloride into an element in the basic group Chemistry of nature (2020). DOI: 10.1038 / s41557-020-0520-6, www.nature.com/articles/s41557-020-0520-6
Provided by the University of Würzburg
Quote: Nitrogen reduction with boron and beer (2020, 14 September) extracted on 15 September 2020 from https://phys.org/news/2020-09-nitrogen-boron-beer.html
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