A new material that acts as a ‘CO2 sponge’ could help kick start a hydrogen economy and remove greenhouse gas from the energy cycle.
The brown powdery polymer is a form of plastic inspired by polystyrene, a plastic used in styrofoam and other packaging material, that can hold onto large amounts of carbon dioxide when under pressure.
Part of a class of material known as adsorbents – differs from absorption in that the soaked up material remains in place and does not dissolve – the material could be integrated into smokestacks and other exhaust streams to remove unwanted emissions.
But the researchers behind the new microporous polymer believe its true value lies in its application to an emerging technology called integrated gasification combined cycle (IGCC), which can convert fossil fuels into hydrogen gas.
As a fuel hydrogen holds great promise for use in both cars and electricity generation because it produces almost no pollution, but the process yields a mixture of hydrogen and CO2 gas, which must be separated.
IGCC is a bridging technology that is intended to jump-start the hydrogen economy, or the transition to hydrogen fuel, while still using the existing fossil-fuel infrastructure. But the IGCC process yields a mixture of hydrogen and CO2 gas, which must be separated.
Lead scientist Dr Andrew Cooper, from the University of Liverpool, said: "The key point is that this polymer is stable, it's cheap, and it adsorbs CO2 extremely well. It's geared toward function in a real-world environment.
"In a future landscape where fuel-cell technology is used, this adsorbent could work toward zero-emission technology."
According to Cooper, the sponge works best under the high pressures intrinsic to the IGCC process and tests have also shown that it is highly stable, even immune, to being boiled in acid, and could therefore withstand the harsh conditions in power plants.
Just like a kitchen sponge swells when it takes on water, the adsorbent swells slightly when it soaks up CO2 in the tiny spaces between its molecules. When the pressure drops, explained Cooper, the adsorbent deflates and releases the CO2, which can then be collected for storage or convert into useful carbon compounds.
Other advantages of the new adsorbent include its ability to adsorb CO2 without also taking on water vapour, which can clog up other materials and make them less effective, as well as its low cost.
“Compared to many other adsorbents, they’re cheap,” Cooper added, mostly because the carbon molecules used to make them are inexpensive. “And in principle, they’re highly reusable and have long lifetimes because they’re very robust.”
Details of the research were presented at the annual meeting of the American Chemical Society in San Francisco.