By Irina Slav
Carbon capture technology has been garnering more and more attention as one way to solve the world’s human-made emissions problem, but costs remain an obstacle. But another technology might help: turning CO2 back into fuel.
Two recent inventions are giving hope, and both have to do with nanocatalysts.
As the name suggests, these are microscopic catalysts—chemicals that accelerate a chemical reaction between other elements—and these catalysts can be used in hydrogenation to produce useful gases.
Hydrogenation put simply, means adding hydrogen atoms to a molecule and therefore removing other atoms from it. With carbon dioxide, hydrogenation could work by removing the oxygen atoms and replacing them with hydrogen, creating hydrocarbons.
Normally, hydrogenation requires extremely high temperatures to occur, and this makes the process costly. It also requires a catalyst, which typically comes in the form of platinum or palladium—both expensive precious metals. Now, it seems there are two alternatives to this process.
A team of researchers from the University of Southern California and the National Renewable Energy Lab developed a new sort of catalyst that can help convert waste CO2 into fuels and precursors for chemical products.
In a news release, the National Renewable Energy Lab said the new catalyst used nanoparticles of molybdenum carbide—a compound featuring a metal and carbon that has an extensive range of applications, among them the conversion of carbon dioxide into carbon monoxide, which is used in chemicals production, and into hydrocarbons.
What’s perhaps more important, however, the process that the NREL and the USC devised involves much lower temperatures than the 1,100 degrees Celsius required to turn metal carbides into catalysts. At these lower temperatures, not only is the process cheaper, but it also allows scientists to manipulate the properties of the nanoparticles and improve the catalytic process.
What’s the big deal? The big deal is that if the technology advances sufficiently to make large enough amounts of these nanocatalysts—the researchers are currently using what they call millifluidic (read miniature) reactors—it could provide a cheaper way of using CO2 rather than leaving it in the atmosphere.
Another team is also attacking this problem, using, besides molybdenum, nickel and magnesium, both much less expensive than the platinum group metals.
“We set out to develop an effective catalyst that can convert large amounts of the greenhouse gases carbon dioxide and methane without failure,” said the lead author of the second study, Cafer T. Yavuz from the Korea Advanced Institute of Science and Technology.
What the KAIST scientists did was use a combination of nickel-molybdenum nanoparticles and crystalline magnesium oxide. They heated the nanoparticles and this forced them to move onto the magnesium oxide creating, according to the news release, a catalyst that “sealed its own high-energy active sites and permanently fixed the location of the nanoparticles — meaning that the nickel-based catalyst will not have a carbon build up, nor will the surface particles bind to one another.”
These both sound like promising methods of utilizing carbon dioxide, essentially recycling it, but where will the carbon dioxide come from? For all the headline space carbon capture has been taking, it still remains, for the most part, prohibitively expensive.
This may be about to change, however, at least in the United States.
Earlier this week, the IRS released new rules for energy companies involved in carbon capture that explain how they can claim higher tax credits for their carbon capture projects.
Congress passed the law that doubled the tax credit companies could claim on their carbon capture projects, the Houston Chronicle’s James Osborne recalled in a report on the news, but it was left to the IRS to say exactly how these credits could be claimed.
“We are still actively reviewing the details at this time. However, we are very pleased to see that the IRS has taken into account key recommendations of the Carbon Capture Coalition,” the head of the CCC, Brad Crabtree, said. “Nevertheless, this work took far too long and has delayed hundreds of millions, if not billions of dollars in investments.”
Now that there is clarity about the tax credits, these investments could materialize, and carbon capture may finally take off. Catalytic technologies such as the ones developed by the American and Korean teams could be a major help in making carbon capture and reuse standard practice at some point in the future.
And the capture part? The MIT has solved this: last year a paper detailed a device that could suck out carbon dioxide from the air, store it and release it when needed for reuse into other chemicals.
“The greatest advantage of this technology over most other carbon capture or carbon absorbing technologies is the binary nature of the adsorbent’s affinity to carbon dioxide,” one of the authors, Sahag Voskian, explained at the time. “This binary affinity allows capture of carbon dioxide from any concentration, including 400 parts per million (the levels in the atmosphere), and allows its release into any carrier stream, including 100 percent CO2.”
So, we’ve got the raw material, we’ve got the capture technology, we’ve got the catalyst and now we’ve also got the legislation that will make applying all this less costly for those who know how to apply it. Maybe carbon capture does have a future, after all.