Capturing and converting CO2 simultaneously

RESEARCHERS have developed a new form of carbon capture technology which simultaneously captures and converts CO₂ so that it can be used to make syngas.

In conventional carbon capture and utilisation, the CO₂ is captured via a sorbent and is then converted into other products in an additional step using a transition-metal-based catalyst. However, this method has a problem with the catalyst becoming deactivated. These catalysts are also expensive and can cause pollution of the environment. In contrast, integrated carbon capture and utilisation (ICCU) uses a “dual functional material” to capture and convert the CO₂ simultaneously.

In the new research, published in IChemE journal Carbon Capture Science & Technology, limestone-derived CaO is used as both a sorbent and catalyst to convert the CO₂ into syngas. While CaO has previously been used as a sorbent, it is usually inactive as a catalyst for CO₂ conversion. The new method captures CO₂ from flue gas and then feeds hydrogen into the reactor to convert the CO₂ into CO. As the captured CO₂ is in the form of CaCO₃, it can be converted without the need for a transition metal catalyst.

The method also has the advantage that when the CaO is at the end of its life, it can then be used in the cement industry, which contributes to a zero-waste economy. It also eliminates the step of transporting captured CO₂ to be utilised.

Chunfei Wu, Reader at the School of Chemistry and Chemical Engineering at Queen’s University Belfast, spoke about the possibilities of scaling up the technology. “We believe it is easy to scale up this ICCU-CaO only process, as it is relatively simple without material circulating, and most importantly, only CaO is used. It is environmentally friendly. However, one key challenge will be the use of hydrogen, which is expensive…all CO₂ hydrogenation processes use hydrogen.”

Carbon Capture Science & Technology https://doi.org/g22w