Material could lead to cheaper methods of CO2 capture

Researchers at Nottingham University have developed a material that could lead to cheaper, more efficient and environmentally friendly methods of capturing carbon dioxide (CO2).

The aluminium-based solid material absorbs CO2 and sulphur dioxide (SO2) in a different way to materials used in existing carbon capture and storage (CCS) technology, which tend to be produced using toxic organic solvents.

The material, known as NOTT-300, is made with water and relatively cheap and simple organic substances, and does not require as much energy as conventional materials in order to release the gases once they have been captured.

CCS is seen as a way of cutting carbon emissions without having to move entirely away from generating energy with fossil fuels. But the technology, which typically involves passing exhaust gases through liquid amine solvents to remove the CO2, uses a lot of energy and so is seen as a burden by industry.

Prof Martin Schröder, who led the research, said NOTT-300 used a different chemical bonding mechanism that can more easily be reversed compared with existing CCS materials, which contain chemicals known as amines (derived from ammonia).

‘You’re not using amines, which themselves can be toxic and have an environmental penalty,’ he told The Engineer.

‘But also with amines you often have to heat the material up to release the CO2. In this present case, the CO2 comes off very readily just by varying the pressure.’

Once the Nottingham researchers had discovered the material, they used the neutron imaging facilities at the ISIS research centre in Oxfordshire to examine and explain how it bonded to the CO2 at a molecular level.

‘The issue is do you want one strong bond or multiple weaker bonds to selectively bind a substrate,’ said Schröder. ‘Having multiple bonds seems to be better even though they are weaker. The net effect is that it holds the CO2 more effectively.’

These weaker bonds, known as hydrogen bonds, form between the oxygen atoms of the CO2 and the hydrogen atoms of the NOTT-300 molecules, rather than between the CO2’s carbon atoms and the amine’s nitrogen atoms.

Other advantages of NOTT-300 are that it is stable in the presence of water and can stably absorb the corrosive and reactive SO2.

The scientists now plan to test NOTT-300 with actual flue gas rather than using controlled laboratory substances, so that it can eventually be scaled up and potentially used in CCS technology.

Their research was funded by the Engineering and Physical Sciences Research Council (EPSRC) and published in the journal Nature Chemistry.