Lithium (black tiles) mediates the conversion of nitrogen (blue blocks) and hydrogen (white blocks) to ammonia. Credit: Meenesh Singh of UIC and Crystal Price and Joseph Gauthier of Texas Tech University
Engineers from the University of Illinois Chicago have developed a greener method for producing ammonia that lowers the temperatures required to drive the reaction. Currently, ammonia production is amongst the highest producers of carbon emissions worldwide due to the temperatures and energy required to manufacture it.
The process, dubbed “lithium-mediated ammonia synthesis”, relies on nitrogen gas as well as a hydrogen-donating fluid such as ethanol. In the synthesis process, nitrogen atoms stick to the lithium, which is then combined with hydrogen to make an ammonia molecule. The entire process occurs at low temperatures and is fully regenerative.
“There are two loops that happen. One is regeneration of the hydrogen source and second is the regeneration of the lithium,” said Meenesh Singh, associate professor of chemical engineering at UIC. “There is a symphony in this reaction, due to the cyclic process. What we did was understand this symphony in a better way and try to modulate it in a very efficient way, so that we can create a resonance and make it move faster.”
The method, published in ACS Applied Materials & Interfaces, is nearly a century old. “The lithium-based approach can actually be found in any organic chemistry textbook. It’s very well-known” Singh said. “But making this cycle run efficiently and selectively enough to meet economically feasible targets was our contribution.”
The team reports that when scaled, the method provides nearly a 60% reduction in costs when compared to traditional or other proposed green production methods of ammonia. Additionally, the team is among the first to achieve suitable selectivity levels that could meet Department of Energy standards for ammonia production.
The team is currently working with the General Ammonia Co. to scale up their synthesis process, and UIC has filed a patent application.