Researchers achieve breakthrough in production of ammonia without CO2 emissions

Date: 13 October 2020

Introduction: KU Leuven and the University of Antwerp join forces for sustainable ammonia synthesis.

The production of ammonia - a very important chemical building block as part of synthetic fertilisers, among other things - is one of the main sources of CO2 emissions. By combining two different technologies, researchers from KU Leuven and the University of Antwerp have now discovered a CO2-free alternative. This research has been made possible thanks to the Moonshot innovation programme of the Flemish Government.

Ammonia is a basic substance within the chemical industry and has many applications, of which engineered fertilizers are the best known example. The production of ammonia, however, is associated with a large amount of CO2 emissions. Worldwide, two per cent of CO2 emissions can be attributed to the production of ammonia. In the chemical industry in Flanders, ammonia synthesis even accounts for fifteen per cent of emissions.

The production is mainly based on the Haber-Bosch process, which was developed at the beginning of the twentieth century. It works with a mixture of nitrogen gas and hydrogen gas, which is then converted into ammonia by means of high temperature and pressure. The use of natural gas, as a source for hydrogen gas, causes large CO2 emissions.

Sustainable alternatives

Researchers of KU Leuven and the University of Antwerp have now achieved a first breakthrough in the search for a sustainable alternative to ammonia synthesis. Their research is supported by the Flemish Government via the Moonshot innovation programme, which aims to ensure a CO2-neutral industry by 2050.

In a first phase, plasma technology will be used. This is the research expertise of Professor Annemie Bogaerts (University of Antwerp). “A first hurdle to producing ammonia is splitting the nitrogen molecule N2. This is a very stable molecule, due to the triple bonding of two nitrogen atoms. Instead of using the high temperatures and pressures of the Haber-Bosch process, we use a plasma reactor.”

"Plasma is obtained by heating gas or introducing electrical energy into it. This creates a cocktail of different reactive particles in which new chemical reactions are possible. In the plasma reactor, you get electrical charges and high temperatures, comparable to lightning. These conditions allow us to split the stable nitrogen molecule N2. Nitrogen oxides are then formed as a result of the reaction with oxygen."

Inspiration from the automotive sector

Nitrogen oxides are better known as NOx. “The automotive sector already has the technologies to eliminate NOx molecules from exhaust gases, which is what we based ourselves on”, says Professor Johan Martens (KU Leuven). “We’ve adapted an existing filter so that it doesn't convert the NOx molecules into nitrogen, but into ammonia.”

“By combining plasma technology with concepts from the automotive industry, we can produce ammonia in a sustainable way. And the great thing is that the necessary raw materials, air and water, are available always and everywhere. For the production of the plasma, on the other hand, you can use renewable electricity from solar or wind energy.”

Decentralised production

“We’ve found a convincing concept, now we need to develop this idea into an industrial process”, says Professor Bogaerts. “This is first done with a pilot set-up in the lab. Ultimately, we want to achieve a functional application that can contribute to the fight against global warming.”

“Our technology will not replace the Haber-Bosch process immediately, but it can provide a particularly valuable addition in the short term”, adds Professor Martens. “Unlike the current ammonia production, that takes place in a limited number of gigantic reactors, plasma technology can be used locally with small installations in different locations. Think of farmers in remote areas: they could use this technology, powered by solar or wind power, to produce their own fertilisers.”

The study ‘A new route towards green ammonia synthesis through plasma‚Äźdriven nitrogen oxidation and catalytic reduction’ by L. Hollevoet, F. Jardali, Y. Gorbanev, J. Creel, A. Bogaerts and J. Martens was published in Angewandte Chemie.