Development of synthetic CaO sorbents via CTAB-assisted sol–gel method for CO2 capture at high temperature

• A CTAB-assisted sol–gel route to prepare tailor-made CaO sorbents.
• A remarkable development in BET surface area and total pore volume.
• A significant improvement in CO2 uptake capacity as well as stability.
• A clear relationship between structures and its performance.

The use of calcium oxide (CaO) for the CO2 looping cycle has attracted increased attention due to several potential advantages. The main drawback of this cycle in practical applications is a sharp decay subsequent to a few cycles of carbonation–calcination. In this work, we report the development of synthetic CaO sorbents via a sol–gel method. Effect of Ca2+/CTAB molar ratios on physical properties of the CaO sorbents as well as their CO2 capture performance were investigated. The presence of CTAB was found to effectively prevent an agglomeration of CaO particles, and to greatly increase BET surface area and total pore volume of the resulting CaO sorbents. Volcano-shaped trends in the BET surface area and total pore volume with respect to the increase of CTAB concentration signal an optimum Ca2+/CTAB ratio. The CaO sorbent prepared with the Ca2+/CTAB molar ratio of 10:3 achieves the highest carbonation conversion of 76.55% in the first cycle, and retains an excellent carbonation conversion of 63.28% subsequent to 20 consecutive test cycles. Furthermore, the analysis results suggest the presence of two linear relationships between: carbonation conversion at reaction stage and BET surface area, and carbonation conversion at diffusion stage and CaO crystallite size.

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