Enhancement of Fast CO2 Capture by a Nano-SiO2/CaO Composite at Ca-Looping Conditions

In this paper we show the performance of a new CO2 sorbent consisting of a dry physical mixture of a Ca-based sorbent and a SiO2 nanostructured powder. Thermo-gravimetric analysis (TGA) performed at conditions close to the Ca-looping process demonstrate that the rate of CO2 capture by the mixture is enhanced during the fast carbonation stage of practical interest in applications. Moreover, the residual capture capacity of the mixture is increased. SEM/EDX, physisorption, and XRD analyses indicate that there is a relevant interaction between the nanostructured SiO2 skeleton and CaO at high temperatures, which serves to improve the efficiency of the transfer of CO2 to small reactive pores as well as the stability of the sorbent pore structure.