New plasma approach can make chemistry greener
UAntwerp researchers develop new method to achieve very sustainable nitrogen fixation
UAntwerp chemists have built a new plasma reactor based on microwave radiation, that makes it possible to perform industrial nitrogen fixation in a much more sustainable way. Nitrogen fixation – used for the production of fertilisers, among other things – is currently a huge burden on the environment, so this development is very important.
Let us start off with a few definitions:
- Atomic nitrogen (N): an essential component for all lifeforms.
- Molecular nitrogen (N2): 78% of the air consists of nitrogen molecules, but these are not reactive.
- Nitrogen fixation: the process by which non-reactive nitrogen molecules from the air are converted into reactive nitrogen components, such as ammonia or nitrogen oxides.
- Plasma: the fourth state of matter aggregation, alongside solid, liquid and gaseous, which is created either by heating a gas or by introducing electrical energy into a gas.
The 'fixing' of nitrogen is essential in order to use the two nitrogen atoms of molecular nitrogen as basic building blocks for living organisms. The process requires an enormous amount of energy. A process that requires fixation is the production of fertilisers: this is currently done through the Haber-Bosch process. ‘Unfortunately, this process consumes almost 3% of the world's natural gas production and emits more than 300 million tonnes of CO2 per year. So there is an urgent need for sustainable alternatives’, explains Professor Annemie Bogaerts.
Electrification
At the University of Antwerp, Bogaerts heads the research group PLASMANT specialising in plasma technology for sustainable chemistry. ‘Plasma is both promising and sustainable’, says the chemistry professor. ‘Plasma technology is very interesting for the “electrification” of chemical processes, one of the great challenges of this century, to stop further climate change and global warming. With this technology, it is possible to achieve nitrogen fixation by using lasma and air powered by renewable electricity.’
Sean Kelly, a postdoctoral researcher at PLASMANT, has built a new plasma reactor based on microwave radiation. This reactor could possibly be the step towards sustainable nitrogen fixation on a larger scale. ‘This new reactor works without electrodes’, explains Kelly. ‘The plasma itself does not come into contact with the walls, significantly extending the reactor’s lifespan and causing less energy loss.’
Industrial upscaling
The Antwerp researchers have also measured record numbers in yields with the lowest energy cost ever reported for plasma-based nitrogen fixation at atmospheric pressure. The experiments show that this process scales very well with increasing electrical power and gas flow rate, as the best results were obtained at the highest powers and flow rates. This indicates possibilities for industrial upscaling.
The ground-breaking research appeared in the journal Joule, one of the leading journals on sustainable chemistry and energy.