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UIC Engineers “Symphonize” Cleaner Ammonia Production


BYLINE: Rob Mitchum

Newswise — Of the many chemicals we use every day, ammonia is one of the worst for the atmosphere. The nitrogen-based chemical used in fertilizers, dyes, explosives and many other products ranks second after cement in carbon emissions, due to the high temperatures and energy required to its manufacture.

But by improving a well-known electrochemical reaction and orchestrating a “symphony” of lithium, nitrogen and hydrogen atoms, engineers at the University of Illinois at Chicago, led by Meenesh Singh have developed a new ammonia production process that meets several green objectives.

The process, called lithium ammonia synthesis, combines nitrogen gas and a hydrogen donor fluid such as ethanol with a charged lithium electrode. Instead of breaking apart the nitrogen gas molecules at high temperature and pressure, the nitrogen atoms stick to the lithium and then combine with the hydrogen to form the ammonia molecule.

The reaction operates at low temperatures and is also regenerative, restoring the original materials with each ammonia production cycle.

“There are two loops that occur. One is the regeneration of the hydrogen source and the second is the regeneration of lithium,” said Singh, an associate professor of chemical engineering at UIC. “There is a symphony in this reaction, due to the cyclical process. What we’ve done is understand this symphony better and try to modulate it in a very effective way, so that we can create resonance and move it forward more quickly.

The process, described in a paper published and featured on the cover of ACS Applied Materials & Interfaces, is the latest innovation from Singh’s lab in the quest for cleaner ammonia. Previously, his group developed methods to synthesize the chemical using sunlight and wastewater and created an electrified copper mesh screen this reduces the amount of energy needed to make ammonia.

Their latest advance is based on a reaction that is hardly new. Scientists have known this for almost a century.

“The lithium-based approach can actually be found in any organic chemistry textbook. It’s very well known,” Singh said. “But our contribution has been to ensure that this cycle occurs efficiently and selectively enough to achieve economically feasible goals.”

These goals include high energy efficiency and low cost. If scaled up, the process would produce ammonia at about $450 per ton, or 60 percent cheaper than previous approaches based on lithium and other proposed green methods, according to Singh.

But selectivity is also important, because many attempts to make ammonia production cleaner have ended up creating large amounts of unwanted hydrogen gas.

The Singh group’s results are among the first to achieve levels of selectivity and energy consumption that could meet Department of Energy standards for industrial-scale ammonia production. Singh also said the process, which can be carried out in a modular reactor, can be made even greener by powering it with electricity from solar panels or other renewable sources and fueling the reaction with l. air and water.

The process could also help achieve another energy goal: the use of hydrogen as a fuel. Achieving this goal was hampered by difficulties in transporting this highly combustible liquid.

“You want the hydrogen to be generated, transported and delivered to hydrogen pumping stations, where the hydrogen can be injected into cars. But it is very dangerous,” Singh said. “Ammonia could serve as a hydrogen carrier. Its transportation is very cheap and safe, and once you arrive at your destination, you can convert the ammonia back into hydrogen.

Currently, the scientists are partnering with General Ammonia Co. to pilot and scale their lithium-based ammonia synthesis process at a Chicago-area facility. The UIC Office of Technology Management has filed a patent for the process.

The research was supported by grants from General Ammonia Co. Co-authors of the paper are Nishithan C. Kani and Ishita Goyal of UIC, Joseph A. Gauthier of Texas Tech University, and Windom Shields and Mitchell Shields of General Ammonia Co.


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