Reducing nitrogen with boron and beer

Date:
September 14, 2020
Source:
University of Wu"rzburg
Summary:
The industrial conversion of nitrogen to ammonium provides
fertilizer for agriculture. Chemists have now achieved this
conversion at room temperature and low pressure using only light
elements.



FULL STORY ========================================================================== Humankind is reliant on the ammonium in synthetic fertiliser
for food. However, producing ammonia from nitrogen is extremely energy-intensive and requires the use of transition metals.


========================================================================== Researchers from Julius-Maximilians-Universita"t (JMU) Wu"rzburg 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 Nature 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 roughly two percent of all energy produced on earth. This process also relies on transition metal elements, relatively heavy and reactive atoms.

In 2018, Professor Braunschweig's team reported the binding and chemical conversion of nitrogen using a molecule constituted only of lighter,
non-metal atoms. A year later, they used a similar system to demonstrate
the first combination of two nitrogen molecules in the laboratory, a
reaction that had otherwise only been seen in Earth's upper atmosphere
and under plasma conditions.

The key in both of these discoveries was the use of boron, the fifth
lightest element, as the atom to which the nitrogen binds. "After these
two discoveries, it was clear that we had a pretty special system on
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 major 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 most simple of reagents: traces of water
left behind 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 done using a solid acid, allowing the reactions to occur sequentially in a single reaction flask,
all at room temperature.

Making ammonium with beer Realising that the acidification step of
the process appeared to work even with simple reagents such as water,
the team repeated the reaction using locally brewed Wu"rzburger Hofbra"u
beer. To their delight, they were able to detect the pre-ammonium product
in the reaction mixture.

"This experiment was in part a bit of fun, but it also shows how tolerant
the system is to water and other compounds," explains Dr. Marc-Andre'
Le'gare', the postdoctoral researcher who initiated the study. "The
reduction of nitrogen to ammonia is one of the most important chemical reactions for humankind. This is undoubtedly the first time it has
been done using beer, and it is particularly fitting that it was done
in Germany!" says Dr. Rian Dewhurst, Akademischer Oberrat and coauthor
of the study.

Much work left to be done The reaction, while exciting, is still
far from being a truly practical process for industrially producing
ammonium. Ideally, finding a way to re-form the active species will be
needed to make the process energy efficient and economical.

Nevertheless, the discovery is an exciting demonstration that the lighter elements can tackle even the biggest challenges in chemistry. "There is
much left to be done here, but boron and the other light elements have
already surprised us so many times. They are clearly capable of so much
more," says Holger Braunschweig.


========================================================================== Story Source: Materials provided by University_of_Wu"rzburg. Original
written by Robert Emmerich. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Marc-Andre' Le'gare', Guillaume Be'langer-Chabot, Maximilian
Rang, Rian
D. Dewhurst, Ivo Krummenacher, Ru"diger Bertermann, Holger
Braunschweig.

One-pot, room-temperature conversion of dinitrogen to ammonium
chloride at a main-group element. Nature Chemistry, 2020; DOI:
10.1038/s41557-020- 0520-6 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200914112210.htm

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