Enlightening ammonia production, new catalyst opens up routes to greener chemistry

Ammonia is a key component in many important chemical processes, like making artificial fertiliser and storing hydrogen. However, making ammonia requires high temperatures and/or expensive metal catalysts. Researchers from Utrecht and Eindhoven have now managed to make a catalyst that operates under moderate conditions and only contains carbon and potassium, both very common elements. This new catalyst has the potential to save energy and cost in this important industrial process. The team of researchers, led by Peter Ngene and Petra de Jongh from Utrecht University, are publishing their results today in Nature Catalysis.

“Ammonia is an incredibly important substance,” says Prof. Petra de Jongh. “It is made in such huge amounts that it is responsible for more two percent of our total energy consumption worldwide, as it is the base to make fertilisers. Any improvement in this process would have a large impact towards CO2 emission reduction. In addition, ammonia is seen as one of the key components in a hydrogen economy: you can store hydrogen in ammonia, which is easy to store and transport as a liquid, and then release the hydrogen when you need it.”

Splitting nitrogen

Ammonia molecules consist of nitrogen and hydrogen atoms. But simply mixing nitrogen and hydrogen together won’t give you ammonia, since the atoms in a nitrogen molecule have a very strong triple bond that needs to be broken. “Converting nitrogen into different compounds, like ammonia, requires the difficult task of splitting up the molecules,” explains Peter Ngene. “In our experiments, we were working with relatively light elements, which are traditionally not seen as viable catalysts. However, when testing hydrogen storage materials, we found out that some of these light elements are, in fact, powerful enough to split nitrogen molecules and easily form ammonia.”

Industrial applications

The new catalyst has great potential for industrial application. Whereas previous ammonia reactions required temperatures of 400-500 °C,  the new catalyst can work at 250-400 °C, rivalling the efficiency of catalysts based on rare and expensive materials like ruthenium, while the new catalyst is made of carbon and potassium, both very common elements. “Our main next step is further optimisation and upscaling the reaction beyond the lab,” says Prof. De Jongh. “We’ve just joined a European consortium where we will work with chemical industry to take on that challenge.”