Small-molecule catalysts improve CO2 capture

Researchers in the Lawrence Livermore National Laboratory (LLNL), based in California, are working with Illinois University and Babcock & Wilcox to develop synthetic small-molecule catalysts that greatly speed up the absorption of CO₂ into liquid solvents that enable them to bind CO₂ less tightly and reduce the energy required to release the CO₂ from the solvent afterwards.

This will open up a range of process conditions and methods for industrial CO₂ capture, ranging from the near-term improvement of existing processes to new capture technologies in the longer term.

’At the highest level, this will speed up systems that absorb CO₂ from flue gas,’ said Roger Aines, LLNL’s Carbon Fuel Cycle programme leader.

The team is replicating one of the fastest enzymes known – carbonic anhydrase – which speeds up the rate in which CO₂ is hydrated.

The catalysts have already been developed in the biomedical field but need to be enhanced to provide industrial robustness against thermal and chemical degradation.

The work will combine LLNL’s scientific experience in creating synthetic small-molecule catalysts with Babcock & Wilcox’s industrial experience and testing to design, synthesise and demonstrate the use of the catalysts in both existing and new CO₂ capture systems.

The three-year project received $3.6m (£2.4m) in funding from the US Department of Energy’s Advanced Research Projects Agency-Energy (ARPA-E), and Babcock & Wilcox will supply its own research and testing costs.

The team will develop three systems: dissolved catalyst systems, which can be immediately applied to industrial practice; tethered catalyst systems, which promise very high efficiency but may require changes in industrial practices; and catalyst-enhanced encapsulated systems, which use liquid solvents enclosed in very thin membrane coats that may represent an entirely new type of carbon-capture system.

Laboratory researchers are working to replicate the enzyme – carbonic anhydrase – so that it can be used to speed up the absorption of CO₂ in the industrial field. Image by Sergio Wong/LLNL

The laboratory’s computational tools will be used to test catalyst designs to ensure their long-term stability. The testing is typically a slow, arduous process, but with LLNL’s supercomputers the team will be able to test hundreds of candidate compounds, produce dozens for bench testing and in only two years be ready for long-term stability tests in large-scale testing facilities, according to Aines.