Humans depend on ammonium in synthetic fertilizers for food. However, producing ammonia from nitrogen is extremely energy intensive and requires the use of transition metals.
Researchers from the Julius-Maximilians-Universität (JMU) Würzburg in 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 reported by a research group led by JMU scientist Holger Braunschweig in the journal Natural chemistry.
A new toolbox for binding nitrogen
The industrial production of ammonia, the so-called Haber-Bosch process, requires high temperatures and pressures and is estimated to consume approx. two percent of all energy produced on earth. This process is also dependent on transition metal elements, relatively heavy and reactive atoms.
The key to both of these discoveries was the use of boron, the fifth lightest element, as the atom to which nitrogen binds. “After these two discoveries, it was clear that we had a rather special system in our hands,” says Braunschweig.
Just add water
Although their system binds and converts nitrogen, only half of the puzzles were in place. “We knew that completing the conversion of nitrogen to ammonia would be a major challenge as it requires a complex series of chemical reactions that are often incompatible with each other,” the JMU professor explains.
The breakthrough came from the simplest reagents: traces of water left in a sample were enough to promote a sequential reaction that brought the team only a single step away from the target ammonium. It was later discovered that the key reactions could be performed using a solid acid so that the reactions could occur sequentially in a single reaction flask, all at room temperature.
Production of ammonium with beer
When the team realized that the acidification step in 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 detect the preammonium product in the reaction mixture.
“This experiment was a bit fun in part, but it also shows how tolerant the system is to water and other compounds,” explains Dr. Marc-André Légaré, the postdoctoral researcher who started 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 done with beer, and it is especially fitting that it was done in Germany,” says Dr. Rian Dewhurst, Akademischer Oberrat and co-author of the study.
Lots of work left
Although the reaction is exciting, it is still far from a truly practical process for the industrial production of ammonium. Ideally, it will be necessary to find a way to reshape the active species to make the process energy efficient and economical.
Nevertheless, the discovery is an intriguing demonstration that the lighter elements can tackle even the biggest challenges in chemistry. “There is a lot left to do here, but living and the other light elements have already surprised us so many times. They are clearly capable of so much more,” says Holger Braunschweig.
Newly designed molecule binds nitrogen
One-pot, room temperature conversion of dinitrogen to ammonium chloride in a main group element, Natural chemistry (2020). DOI: 10.1038 / s41557-020-0520-6, www.nature.com/articles/s41557-020-0520-6
Provided by the University of Würzburg
Citation: Reduction of nitrogen with boron and beer (2020, 14 September) retrieved 15 September 2020 from https://phys.org/news/2020-09-nitrogen-boron-beer.html
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