Influence of SiO2 and MgO on CaO-based carbon capture

https://doi.org/10.1016/j.cej.2020.124140

“It is clearly observed in Fig. 8 that CO₂ uptake of the BFS-derived sorbents presented a positive correlation with the content of MgO, however, a negative correlation with that of SiO₂ in the material. This is attributed to the different mechanisms of interaction between the two stabilisers and the CaO phase. The MgO stabiliser appears independently in the sorbent matrix without the formation of solid solutions with CaO, while the SiO₂ stabiliser will react with CaO, as discussed above, to form a Ca₂SiO₄ layer on the CaO-SiO₂ interface. The formation of solid solutions between stabilisers and CaO has also been reported in the studies on the investigation of other stabilisers, including Al₂O₃ [52] and ZrO₂ [53]. These solid solutions on the interface would prevent the CaO particles from agglomeration and sintering, but come at the expense of a portion of the free CaO which is supposed to be available for CO₂ capture. Accordingly, the fact that N₁-30 has the highest content of SiO₂ explained its inferior CO₂ capture capacity in this study. With regard to the development of CaO-based CO₂ sorbents using the BFS waste as a feedstock, special attention should be paid to controlling the content of Si in the material in order to balance its uptake of CO₂ and cyclic stability for CO₂ capture.”

“Fig. 8. Influence of the chemical composition of inert components on CO₂ uptake of the BFS-derived, CaO-based CO₂ sorbents.”