Aug
13
A New Sponge to Soak Up CO2
August 13, 2014 | Leave a Comment
A sponge-like plastic that sops up the greenhouse gas carbon dioxide was presented at a meeting of the American Chemical Society by chemists from the University of Liverpool. The material, a relative of the plastics used in food containers could be integrated into power plant smokestacks in the future. The report on the material is one of nearly 12,000 presentations at the 248th National Meeting & Exposition of the American Chemical Society.
CO2 Polymer Sponge Process Illustration. Plastic that soaks up carbon dioxide could someday be used in plant smokestacks.
Image Credit: American Chemical Society. Click image for the largest view.
Andrew Cooper, Ph.D. 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.”
Today CO2 adsorbents are most commonly used to remove the greenhouse gas pollutant from smokestacks at power plants where fossil fuels like coal or gas are burned. However, Cooper and his team intend the adsorbent, a microporous organic polymer, for a different application, one that could lead to reduced pollution.
The new material would be a part of an emerging technology called an integrated gasification combined cycle (IGCC), which can convert fossil fuels into hydrogen gas. Hydrogen holds great promise for use in fuel-cell cars and electricity generation because it produces almost no pollution. 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.
Cooper explained that the sponge works best under the high pressures intrinsic to the IGCC process. 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 the adsorbent deflates and releases the CO2, which they can then collect for storage or convert into useful carbon compounds.
The material, which is a brown, sand-like powder, is made by linking together many small carbon-based molecules into a network. Cooper explained that the idea to use this structure was inspired by polystyrene, a plastic used in styrofoam and other packaging materials. Polystyrene can adsorb small amounts of CO2 by the same swelling action.
One advantage of using polymers is that they tend to be very stable. The material can even withstand being boiled in acid, proving it should tolerate the harsh conditions in power plants where CO2 adsorbents are needed. Other CO2 scrubbers, whether made from plastics or metals or in liquid form, do not always hold up so well, he says.
Another advantage of the new adsorbent is its ability to adsorb CO2 without also taking on water vapor, which can clog up other materials and make them less effective. Its low cost also makes the sponge polymer attractive.
“Compared to many other adsorbents, they’re cheap,” Cooper said, 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.”
Cooper described ways to adapt his microporous polymer for use in smokestacks and other exhaust streams. He explained that for instance, it is relatively simple to embed the spongy polymers in the kinds of membranes already being evaluated to remove CO2 from power plant exhaust. Combining two types of scrubbers could make much better adsorbents by harnessing the strengths of each.
Any news means to capture CO2 is welcome and Cooper may be on to something, so breaking out a new field. CO2 is very useful, critical to life on this planet, and offers a steady reliable source for a wide range of materials with fuel a leading cause to recycle.
The announcement is the first step and hopefully others will take up the research for even better CO2 scrubbing materials.
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