Next-Level Nanoscience

FROM THE MARCH ISSUE: The accidental discovery that a carbon, nitrogen and copper-based catalyst can convert carbon dioxide to ethanol shows potential.
By Lisa Gibson | February 15, 2018

In 2016, Adam Rondinone and his team at Oak Ridge National Laboratory discovered that a simple catalyst based on carbon, nitrogen and copper could convert carbon dioxide into ethanol. It was a surprise. “We were studying catalysis based on nanoscience and we had some hypotheses about how to set up a reaction,” Rondinone says. “The reaction worked better than we expected.”

The team was experimenting with arranging the atoms on a surface to create a highly selective catalyst—one that produces mostly one product. “For catalysis, getting selectivity is always the challenge,” Rondinone says. “You push the chemicals across the catalyst, add some energy and hopefully you get the right product. … We expected an alcohol, but we didn’t expect ethanol. And that started us on a couple-year journey to understand how the catalyst worked. We’re still on that journey. We don’t fully understand how the catalyst works. But we understand what products it can make.”
Now, the team is continuing development on that reaction, with a target of commercialization in mind. Rondinone says it could be ideal for yield boosts and CO2 abatement in the ethanol industry. It’s not a competitor, he emphasizes.

The Reaction
The catalyst itself is a coating made of the carbon, nitrogen and copper. Rondinone works exclusively in nanoscience, which plays a major role in the reaction. The carbon and nitrogen are arranged into tiny, sharp spikes, like little lightning rods, with copper nanoparticles imbedded among them, Rondinone explains. The spikes generate high electric fields and kick off the reaction, converting the CO2 into carbon monoxide, which then becomes a reagent for the rest of the reaction to produce ethanol. The coating is being applied to silicone for reactions, but the team is looking at other materials, also.

Essentially, when CO2, water and electricity are applied to the catalyst, ethanol results. “Just the idea that you can take carbon dioxide and water, which are the byproducts of combustion, add energy back in as the form of electricity and push the reaction backwards to hydrocarbon fuel was really appealing, I think, to people and that’s why it attracted a lot of attention.”

The yield is high, also. From an electricity perspective, it averages 63 percent, with a range of 60 to 70 percent, Rondinone says. That means if 100 electrons are run across the catalyst, 63 of those electrons are stored as ethanol. With respect to Co2, the yield is 84 percent, with the remaining 16 CO2 molecules converted to methane or carbon monoxide. “That makes it a pretty selective catalyst,” Rondinone says.

Every chemical reaction has multiple steps and every step has the potential to branch in different directions. “We want to minimize branching,” he says. “We want to minimize diversions down the wrong pathway and keep all the products moving together toward this final outcome, which is the alcohol. That’s what the catalyst does very well.

“Our understanding of how the catalyst works now is much more sophisticated than it was a year ago.” Rondinone says the team has verified that the reaction is a three-step sequence, with each step taking place on a certain area of the catalyst. “We’re working fast to understand the technology as an industrial technology, not necessarily as a science project.” That means understanding it from the point of view of a party that might commercialize it.

What’s Next
The team is studying energy efficiency, conducting economic analysis and looking at the purest chemicals in the reaction, including how pure the CO2 needs to be. How long does the catalyst last? When it does fail, why?

Several parties are interested in participating in commercialization, but the most obvious option is the fuel ethanol industry, Rondinone says. The team has funding to continue its development work for another year, after which time Rondinone hopes to find a party to license and further scale the technology.

Rondinone says, from his standpoint, the process seems scalable and represents an enormous opportunity. The ethanol industry could see widespread adoption of the technique. “We’ve learned nothing in the last year that would say that that won’t happen or that it can’t happen. Whether or not it does, of course, depends on economic circumstances. But we’ve spent the last year now really studying the technology from the industrial perspective and it looks like it will scale. It looks like the economics will work under certain circumstances. … We have been successful scaling the technology in-house.”

Tammy Klein, principal of consulting firm Future Fuel Strategies, says the technology holds great potential for the industry, as long as ORNL’s further development finds that the economics, energy efficiency and other aspects of the concept work out. “If all those pieces fall into place for producers, it could be really beneficial.” Klein points to the increase in carbon-reduction tactics in the ethanol industry, many that increase efficiency. “The science is evolving,” she says. “They’ve been doing all sorts of things to reduce their carbon intensity and this is another avenue to do that.”

Other jurisdictions are starting to follow California’s footsteps, implementing policies similar to the Low Carbon Fuel Standard. It’s a carbon-constrained world, she says, citing Canada and Brazil. “The race to capture that value of the fuel greenhouse gas-reducing potential is on.

“We’ll have to stay tuned and see how this all works out,” she adds. “I think it has a lot of promise.”

Before Commercialization
Electricity costs are the biggest consideration to commercial development currently, Rondinone says. He recommends low-cost excess wind power, an option that Klein says many ethanol producers already are exploring.

Rondinone says ORNL’s catalyst potential in the ethanol industry doesn’t have barriers, so much as risks. Nobody understands the long-term viability of the catalyst, for instance. “It may be that the catalyst doesn’t last as long as we’d like it to and makes it nonviable,” he says. Maybe the off gas won’t be appropriate for some reason; the contamination intolerance is unknown. “We have incomplete data. The only barriers are incomplete knowledge. Technical development is crucial. 

“We’re early on in this process. If things continue to work out and continue to look good, we will progressively work our way toward larger demonstration. And this will be a several-year process. This is a new technology and it’s going to take some time to develop.”

On-site, an ethanol plant would need a large-scale chemical reactor. CO2 from the fermenter would be fed into the reactor, along with electricity, then the ethanol would be separated from the water with vacuum distillation. Rondinone says the team is also exploring options that don’t use water.

The catalyst is unique in its efficiency, as well as its lack of rare metals or expensive components. Carbon, nitrogen and copper are affordable, Rondinone says. “This is one of the reasons we think this is scalable.”

Another Option
Rondinone and his team aren’t the only ones looking at CO2-to-ethanol conversion at existing plants. Gary Young, president of Bio-Thermal Energy Inc., says he has been developing a gasifier that can take CO2 and the carbonaceous material in steam to create a syngas that then can be converted to ethanol through a Fischer-Tropsch system.

The gasifier heats to 2,000 degrees Fahrenheit and converts the CO2 to 70 percent syngas, Young says.

He says he is working with a rural municipality in the Midwest to develop a project that would include construction of a 50 MMgy ethanol plant, as well as his system attached to produce more ethanol from the CO2. At that size, the plant could produce ethanol at a cost of 70 cents per gallon, including the cost of the capsule required to house his technology, with 6 percent interest for 20 years, he says. “It more than doubles ethanol production from that plant.” He declines to name the municipality, saying he still is working on the agreement.

Young says he hopes to have a project under development with his potential partners in about a year. The system could use CO2 from any industry with a gaseous stream, but ethanol represents the best opportunity because of its pure CO2. “The low-hanging fruit is really the CO2 coming off an ethanol plant.”

Increasing Fuel Supply
Meanwhile, Rondinone says several parties and industries are interested in helping commercialize ORNL’s catalyst, and it clearly fits within ethanol’s existing infrastructure. It could even prompt higher blends.

“What you have here is an opportunity to capture that carbon dioxide, convert it back into the product you’re looking for, and then just feed it right back into the same distribution pipeline that you already have in place. It opens up the possibility of actually greatly increasing the fuel supply for ethanol, which then, in my mind, puts us on the path toward a higher ethanol blend.”

Author: Lisa Gibson
Managing Editor, Ethanol Producer Magazine