Capturing the carbon dioxide from billowing out of fossil fuel power plants and other factories is an essential part of most realistic routes to net-zero greenhouse gas emissions, according to the nonprofit International Energy Agency. TheThe dominant carbon-capture technology today, bubbling the flue gas through aqueous amine solutions, saps around 30% of a power plant’s output.
Researchers from ExxonMobil and the City College of New York think they can do better with a microtextured solid lattice coated in pure liquid amines (Sci. Adv. 2022, DOI: 10.1126/sciadv.abm0144). The company has filed for three US patents based on the work.
Up to 80% of the energy that traditional amine systems use goes to regenerate the aqueous solvent, heating large volumes of water to drive out the captured CO2 out for storage, the authors write. Approaches that use less water could slash the energy demand of the process.
Other carbon-capture systems under development eliminate water by using functionalized metal-organic frameworks (MOFs) or other microporous materials with CO2-grabbing amine groups. But MOFs are a new type of material that are still expensive. The approach proposed by ExxonMobil’s Mohsen Yeganeh and coworkers in some ways marries such solid sorbents with the more established aqueous amine solutions.
The team 3D printed a textured lattice of metallic AlSi10Mg, then oxidized the surface to encourage the liquid amines to adhere in a layer tens of micrometers thick. The researchers say the resulting lattice—which they call a solid with infused reactive liquid, or SWIRL—offers more reactive amine groups per unit volume than conventional aqueous solvent systems and most MOFs while remaining relatively cheap to build and operate.
David Heldebrant, a carbon capture chemist at the Pacific Northwest National Laboratory, says eliminating water from amine-based capture solvents can cut energy use by 20%. And the the SWIRL material’s ability to work well at 90 °C means there is less need to cool the flue gas before it reaches the capture equipment. Existing systems take “a lot of cooling water and wasted energy to heat and cool the sorbent from 40–120 °C during heating and cooling cycles,” Heldebrant says. But he cautions that the reported sorbent regeneration method—stripping the CO2 with an inert gas—wouldn’t be practical in an industrial-scale device.
Joanna Aizenberg, a chemistry professor at Harvard University, pioneered the use of microtextured surfaces to immobilize thin layers of liquid in an approach called slippery liquid-infused porous surfaces, or SLIPS.“The novelty of this work is to introduce a reactive medium into SLIPS,” which up to now has been mostly applied primarily to lubrication, she says. “This is a very interesting and promising application.”