Author: Tronserve admin
Thursday 5th August 2021 02:25 AM
Holy Grail? Scientists Devise ‘Nanocatalysts’ To Recycle Carbon Dioxide Back Into Fuels
It’s a Holy Grail idea: Take carbon dioxide from the combustion of fossil fuels and run it through a chemical reaction that transforms it magically back into useful hydrocarbons. It would be a virtuous cycle, a carbon-neutral closed loop that could dramatically reduce greenhouse gases. If it works.
The chemistry to do such a thing has been known for a while, and involves a reaction called hydrogenation—swapping the oxygen atoms in the carbon dioxide with hydrogen atoms, to yield hydrocarbons like methane (the primary ingredient in natural gas).
So far it’s been nowhere close to economic, as the reactions have required special catalysts using expensive precious metals like platinum that could only be made in reactor vessels containing volatile gases operating at 1,100 degrees Fahrenheit.
But that could be about to change. Scientists at the University of Southern California and the National Renewable Energy Lab have announced an innovation that could someday lead us to a nirvana of near-endless carbon offsets.
The breakthrough: a cheaper, more sustainable way to make nanocatalysts that work as well as platinum but use the far more plentiful metal molybdenum—and can be manufactured 90% cheaper at “low” temperatures closer to 600 degrees.
Catalysts are substances that increase the rate of a chemical reaction without being consumed. The nano size of these resulting molybdenum carbide catalysts is vital to their efficacy, says NREL chemist Frederick Baddour, because the hydrogenation reactions happen on the surface of the catalyst, triggered by its physical characteristics. “The catalyst provides a surface for the chemicals to stick to,” says USC’s Noah Malmstadt. “Nano particles are all surface.”
Usually when chemists want to make more of something, cheaper, they scale up to bigger vats and higher temperatures. But making nanocatalysts requires a more delicate touch. “You can’t just get a giant flask,” says Baddour. “It heats differently, it’s not uniform.”
Their process instead utilizes tiny “millifluidic” reactors—tubes just a millimeter in diameter in which they can create bespoke catalysts. “We can control more features of the final product, different shapes, incorporate other metals,” says Baddour.
Tiny reactors can’t make a lot of catalysts, so Malmstadt’s lab at USC has advanced the scalability of this process, via modularization. They now have 16 millifluidic reactors, working in parallel. It’s akin to how the mainframe supercomputers of the 1970s evolved into giant server farms with thousands of processors.
It’s still early, but before too long they could be making “industrially relevant amounts” measured in kilograms per year. Within a decade, demand for such nanocatalysts could be more like tons per year, with myriad applications.
At NREL Baddour has been working to turn wood and grasses into more versatile fuels by subjecting the biomass to pyrolysis (heating in the absence of oxygen), which yields charcoal plus vapor perfect for reacting with nanocatalysts. Another application is in “biorefineries” that manufacture ethanol and a stream of nearly pure CO2.
Further out is the potential to coat electrodes with nanocatalysts and fashion them into membranes that could be incorporated into existing power plant “scrubber” systems through which exhaust gases flow. The required hydrogen could be made by electrolyzers powered by cheap renewable energy.
It’s an area ripe for more breakthroughs. Asked if he can recall any particular “eureka” moments that have driven his recent work, Baddour says, “I’d like to think they happen most days.”