How to figure out the mechanism of carbon capture and quicklime rehydration – Diamond Light Source X-Ray Diffraction to the rescue!

Carbon capture and storage is an essential part of recycling waste carbon, and ensuring it goes back into the carbon cycle. It is also beneficial for the environment because there is less atmospheric carbon dioxide present and therefore has a positive impact pn the global warming effect.

 

A low cost carbon capture method, which could be used by factories and power plants, underwent X-Ray Diffraction using a Diamond Light Source to study the process in deep detail. In situ X-Ray diffraction was used to make nanoscale observations on the specific details of the steps within the process of Carbon capture and rehydration of the Calcium Oxide.

The basic chemical reaction of the process is as follows:

CaO_(s) + CO_2(g) →  CaCO_3(s) 

The X-Ray diffraction imaging using the Diamond Light Source allowed a more precise and higher resolution view of the processes taking place, which led to insight towards how the Calcium Oxide (CaO) can be kept efficient even after several rounds of sintering, and how the hydration process can be tweaked to make this step efficient. Science Daily explained why it is necessary to study this process pretty well:

"after multiple capture and regeneration cycles, [Calcium Oxide's] capacity for capture decreases due to the loss of surface area through sintering, a process that fuses powders together to create a single solid object. Although the surface area can be restored through hydration, the material suffers a reduction in mechanical strength. If these problems can be overcome, CaO based materials could provide a low cost answer for carbon capture on a very large scale."

Although CaO based capturing of CO2 seems promising and is known to be low-cost, the reactions require temperatures of up to 800 °C which would mean this process needs the burning of a lot of fossil fuels.

However, the researchers who carried out this work explored and obtained a lot of information through the light scattering imaging results from the X-Ray diffraction, for example about the hydration process of the CaO.

Source: Molinder J et al. In situ X-ray diffraction of CaO based CO2 sorbents. Energy & Environmental Science (2012), http://dx.doi.org/10.1039/C2EE21779A