NEW MATIERALS COUD REDUCE PARASITIC LOAD OF CO2 CAPTURE BY UP TO 40%, RESEARCHERS SAY

Tamar Hallerman
GHG Monitor
06/08/12

Researchers in California and Texas say they have tested a class of materials that has the potential to be ideal for capturing CO2 emissions in post-combustion systems. In a recent study published in the journal Nature Materials, researchers from the University of California-Berkeley, Lawrence Berkeley National Laboratory, the Electric Power Research Institute (EPRI) and Rice University said that a group of roughly 500 adsorbents could have the potential, if further tested, to reduce the parasitic load of CO2 capture systems by 30 to 40 percent compared to current amine solvent capture systems. “Our screening shows a large set of … structures which have a parasitic energy well below the current technology,” the study says.

The scientists combined several Department of Energy grants to develop a computer program that simulates running nanoporous adsorbent materials known as zeolites and metal organic frameworks (MOFs) through power plant-like conditions to see if they are ideal for carbon capture systems. Researchers can create different versions of the zeolites and MOFs, which are micro-porous crystal frameworks of atoms, by changing the type of metal and organic linkers found on the molecular level. Head author Berend Smit, a professor of Chemical and Bimolecular Engineering at the University of California-Berkeley, said the research team tested 5 million simulated materials through the program—since testing each one physically would be expensive and time-consuming given the large number of available options—to see which materials were optimal for CCS. “The database of 5 million structures is basically a theoretical attempt to enumerate all possible materials and examine which [ones] are ideal for CCS,” Smit said in an interview with GHG Monitor. 

Smit said this round of testing focused exclusively on parasitic load, or the energy penalty needed to separate the CO2 from flue gas, currently considered one of the major cost barriers to the commercial deployment of CCS. “Here we looked at parasitic energy because that was felt by EPRI as the most relevant thing to do first. If the parasitic energy doesn’t go down significantly, then it’s not worth looking at other properties,” Smit said. Of those 5 million materials tested, Smit said roughly 500 turned out to be “promising” and will soon undergo further tests to evaluate those adsorbents against other criteria such as diffusion limitations and reactions with water.

Some Commonalities Discovered

Researchers found that many of the optimal materials for parasitic load were found to have similar qualities, Smit said. The best adsorbents tested tended to have large internal surfaces, he added. “What is optimum in this case is very mild,” Smit said. “A material needs to have a pleasant environment for CO2 molecules to adsorb, and this adsorption needs to be sufficiently strong such that you have selectivity with respect to nitrogen. But if it’s too strong it costs too much energy to [separate].”

The researchers also created an electronic database that classifies all of the materials tested by their level of potential for CCS. From there, Smit said, other researchers can access their database and work off of their results, which have drastically narrowed down the number of materials considered promising. “What we tried to do was come up with a very simple criteria where chemists could easily check whether they had a promising material or not,” he added. “We have helped narrow the field of possibilities from millions of materials to hundreds, which is much more manageable to test.”

Smit said that while the research deals largely with simulated materials that have not yet been tested outside of a computer program, the work is significant because it will likely save time for researchers looking for the next optimum post-combustion technology. “It’s quite cool to be able to screen millions of materials and see which ones are the best and actually at a level that engineers are comfortable with,” he said, adding that, if developed, nanoporous materials could be competitive with current amine technology. “It’s worth looking at these types of materials,” he said.