Le Chatelier’s Principle Sparks New Green Ammonia Breakthrough
Now that everyone knows about the Queen’s Gambit, get ready for Le Chatelier’s principle. That’s the notion behind a new high efficiency process that could pump up the market for green ammonia and green hydrogen both at the same time. Green hydrogen is already a thing, which leaves the ammonia piece of the puzzle to figure out, and the US Department of Energy is already plotting a course in that direction.
Green Ammonia For The Green Hydrogen Economy
For those of you new to the topic, hydrogen is an abundant, zero emission fuel and chemical building block that comes mainly from fossil sources — but not for long. Because the cost of wind and solar power keeps dropping, the financial picture is improving for electrolysis, which involves “splitting” hydrogen from water with electricity.
Other green hydrogen pathways are also in development, but electrolysis appears to have the edge for now in terms of market-readiness, so now everyone is getting all excited about the green hydrogen economy of the future. However, technological obstacles remain to be overcome, and one of them is how to transport the hydrogen in a way that makes bottom line sense. Piggybacking hydrogen onto existing gas pipeline infrastructure is one option, but that leaves wide swaths of the potential market untapped.
Transportation options crack open a bit wider when hydrogen is liquefied, but it costs money to liquefy hydrogen. One emerging solution is to use the green hydrogen at or near its point of production make green ammonia (the formula for ammonia is NH3). Ammonia is less expensive to liquefy, the US already has an extensive ammonia transportation and storage infrastructure in place, and the ammonia industry could certainly do with a green makeover (for the record, most ammonia is currently produced from methane or other fossil sources).
US Energy Department Banks On Green Ammonia
That’s all well and good, but what does it have to do with the hydrogen economy of the sparkling green future? Plenty, if the new research pans out. The idea is to use green ammonia as a transportable carrier for green hydrogen.
That’s easier said than done, because now the issue getting the hydrogen away from the ammonia. That costs money, and the whole thing has to make sense financially.
And, that’s where the US Department of Energy comes in. The agency has been front and center in the push for green hydrogen, and it has hopping on the green ammonia bandwagon as well.
The Energy Department formalized its efforts in 2016 through a new hydrogen initiative called REFUEL, short for Renewable Energy to Fuels through Utilization of Energy-dense Liquids. REFUEL aims at developing “scalable technologies for converting electrical energy from renewable sources into energy-dense carbon-neutral liquid fuels (CNLFs) and back into electricity or hydrogen on demand.”
REFUEL took shape in 2016 during the last days of the Obama administration, and if you’re thinking the Energy Department dropped the ball after Obama left office in January 2017, guess again. Green ammonia is just one of several decarbonization programs pursued by the Energy Department with gusto over the past four years. The transformative energy office ARPA-E was tasked with heading up REFUEL and it went ahead with an invitation-only kickoff conference in August 2017.
Lending gravitas to the effort was Siemens, which declared that green ammonia would enable “decarbonization of global economy by 2100 and fundamental changes in worldwide energy market already today.”
So much for saving all your coal jobs!
The Decarbonization Of The Global Economy Continues
Where were we? Oh right, green ammonia. If our tally is correct, REFUEL already has 17 projects on its funding roster, including an ammonia-to-hydrogen grant awarded to a team of researchers at Northwestern University. along with an assist from the National Science Foundation.
The Northwestern team just published their results in Joule under the title, “Solid Acid Electrochemical Cell for the Production of Hydrogen from Ammonia,” and if you don’t have time to read the whole thing, the lead author on the study is Sossina M. Haile, Walter P. Murphy Professor of Materials Science and Engineering at Northwestern, and she provides a handy summary.
“It’s difficult and expensive to transport hydrogen, but an extensive ammonia delivery system already exists,” Professor Haile explains. “There are pipelines for it. We deliver lots of ammonia all over the world for fertilizer. If you give us ammonia, the electrochemical systems we developed can convert that ammonia to fuel-cell-ready, clean hydrogen on-site at any scale.”
“Converting ammonia to hydrogen on-site and in a distributed way would allow you to drive into a fueling station and get pressurized hydrogen for your car. There’s also a growing interest for hydrogen fuel cells for the aviation industry because batteries are so heavy,” she adds.
To ice the green cake, the new ammonia conversion device operates at a relatively low temperature of 250 degrees Celsius, which enabled the team to deploy electricity from renewable energy to power the process. A conventional electrochemical process of that sort requires higher heat of 500 to 600 degrees Celsius.
To ice the icing on the cake, the device produces pure hydrogen that does not require further processing, and it does not lose energy to side reactions.
All of this is very interesting from the perspective of DERS, aka distributed energy resources, which the Energy Department has nailed as the key to the future of the sparkling green, secure, and resilient grid of the future. Think ammonia fuel, distributed wind energy, and rooftop solar arrays, and you can see where the hydrogen-ammonia-hydrogen angle fits.
What’s All This About Le Chatelier’s Principle?
The heart of the Northwestern breakthrough is an electrochemical cell that sports a proton-conducting membrane, hooked up with a catalyst that can split ammonia into hydrogen and nitrogen.
The reaction converts the hydrogen into protons, which are then pulled out through the membrane of the electrochemical cell.
“By continually pulling off the hydrogen, we drive the reaction to go further than it would otherwise. This is known as Le Chatelier’s principle,” explains Haile. “By removing one of the products of the ammonia-splitting reaction — namely the hydrogen — we push the reaction forward, beyond what the ammonia-splitting catalyst can do alone.”
Le Chatelier’s principle is a predictive tool that enables chemists to predict what will happen if you disturb a chemical in a state of equilibrium (spoiler alert: it tries to re-establish equilibrium).
In an interesting twist, the French scientist who developed it — Henry Louis Le Chatelier — dabbled in ammonia production at one point in his long and notable career.
Unfortunately, he did not dabble very far. Our friends over at sciencenotes.org explain that his experimental ammonia synthesis device exploded and killed one of his assistants, putting an end to his efforts in that area.
Others continued hammering away at the problem, and just a few years later the Haber-Bosch process popped up, which was similar to Le Chatelier’s trial but filled in the missing piece by deploying nitrogen extracted from the air.
Le Chatelier was still around during that breakthrough (he died in 1936), and was known to express regret for not pursuing his work. Little did he know!
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Image (screenshot): via US Department of Energy, ARPA-E.
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