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Chemistry

Giving Nitrogen a New Break

 

nitrogen

© Quadrelli, Basset and Taoufik

Exciting dinitrogen full cleavage by isolated silica-supported tantalum atom.


Nitrogen makes up almost 80% of the Earth’s atmosphere and is an essential element of all living tissues and amino acids. Its molecular form, dinitrogen or N2, consists of two nitrogen atoms joined by one of the strongest triple bonds known in chemistry.
A team of CNRS scientists from the C2P2 laboratory1 has found a new mechanism for splitting these bonds,2 an act which is fundamental to both biology and modern industrial chemistry; it is the basis for producing ammonia and from oxidized ammonia are produced nitrates and nitrites, key constituents of fertilizers and explosives.
Until now, removing this bond required the usage of different metallic atoms as catalysts. On a biological level, certain bacteria producing enzymes containing up to 20 metals are capable of breaking down the N2 bond. In an industrial context, it is split using the Haber-Bosch process, invented more than 100 years ago by German chemist Fritz Haber. His discovery involves the use of several metals in a process of heterogeneous catalysis. This energy-intensive process is how the 100 million tons of industrial ammonia are produced in the world each year, using up about one percent of the world’s energy production.
The CNRS team has discovered that the triple bond can be undone by single atoms of tantalum, a metallic element low in electrons, which are isolated on a silica surface like surface hydrides–a method quite distinct from other bond-breaking mechanisms. Their findings follow several years of research into surface organometallic chemistry. By using methane (another molecule difficult to activate) to build longer carbon atom backbones on alkanes (the saturated hydrocarbons also known as paraffin), they succeeded in producing new catalytic reactions.
The research is still in progress; when splitting the N2 triple bond, tantalum hybrides do not release ammonia–the separated nitrogen atoms stay separately bound to the metal. There is also the possibility of using the catalyst to incorporate nitrogen into organic substrates– such as transforming alkanes into amines. The potential is tantalizing.
Graham Tearse

Notes :

1. Laboratoire Chimie, catalyse, polymères et procédés (CNRS / Université Lyon 1 / Ecole supérieure de chimie physique électronique de Lyon).
2. P. Avenier et al.,
“Dinitrogen
Dissociation on an
isolated Surface
Tantalum Atom,”
Science. 317: 1056-60. 2007.

Contacts :

C2P2, Villeurbanne.

Jean-Marie Basset
basset@cpe.fr

Elsje Alessandra Quadrelli
quadrelli@cpe.fr

Mostafa Taoufik
taoufik@cpe.fr


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