Making ammonia truly “green”

AUSTRALIA: Chemical engineers at UNSW Sydney and University of Sydney claim to have found a new eco-friendly and cheap way to manufacture ammonia from air, water and renewable electricity.

Widely used in the production of fertiliser, ammonia is also one of the low GWP “natural” refrigerants vital to global efforts to reduce the environmental impact of refrigeration. Its production, however, requires the high temperatures, high pressure and an infrastructure that leaves a huge carbon footprint.

Traditional ammonia production via the Haber-Bosch process is said to consume 2% of the world’s energy and accounts for 1% of the industrial world’s carbon dioxide emissions.

The Haber-Bosch process is only cost-effective when carried out on a massive scale, due to the huge amounts of energy and expensive materials required. These centralised production locations means even more energy is required to transport ammonia around the world, not to mention the hazards that go with storing large amounts of it in the one place.

The new process produces ammonia cheaply, on a smaller scale and using renewable energy.

Previous attempts to convert atmospheric nitrogen directly to ammonia using electricity has previously posed significant challenges to researchers due to the inherent stability of nitrogen gas.

The university team devised lab experiments using plasma (a form of lightning made in a tube) to convert air into an intermediary, either NO2 (nitrite) or NO3 (nitrate). The nitrogen in these compounds is much more reactive than atmospheric nitrogen.

“Working with our University of Sydney colleagues, we designed a range of scalable plasma reactors that could generate the NOx intermediary at a significant rate and high energy efficiency,” said team member Dr Ali Jalili.

“Once we generated that intermediary in water, designing a selective catalyst and scaling the system became significantly easier. The breakthrough of our technology was in the design of the high-performance plasma reactors coupled with electrochemistry.”

In addition to the advantages of being able to scale down the technology, the team’s “green” method of ammonia production could solve the problem of storage and transport of hydrogen energy.

The team will next turn its attention to commercialising this breakthrough, and is seeking to form a spin-out company to take its technology from laboratory-scale into the field.

Source: Cooling Post