Li4SiO4-based sorbents from expanded perlite for high-temperature CO2 capture

Abstract

In this work, expanded perlite (EP) was firstly used as a silicon source for Li4SiO4 sorbent. It was found that the metal impurities of EP compared with commercial SiO2 can result in a rough morphology with smaller size particles of the synthesized sorbent, improving the sorption performance of sorbent in the temperature range of 500–650 °C. EP-Li4SiO4 possessed fine cyclic stability and higher CO2 capture capacity during the multiple cycles. Moreover, the sorbent pellets produced via graphite moulding method showed good sphericity and cyclic stability. Due to the hydrophobic force and shrinking force during the granulation process, the densification of the microstructure and the reduction of the specific surface area led to the deterioration of the CO2 sorption performance of the pellets. The addition of agar or using organic lithium source can effectively enhance the sorption capacities of pellets due to the improvement of the mesoporous structure and specific surface area. The best sorption capacities of the pellets modified with agar and the pellets using lithium oxalate as the lithium source were 21.9 wt% and 25.3 wt% respectively at 650 °C under pure CO2. The sorbent pellets showed good mechanical properties, including compressive strength (>2.1 MPa) and attrition resistance (<7 wt% after 2000 rotations). Considering its fine physicochemical properties, the EP derived Li4SiO4-based sorbent has promising prospects for CO2 capture.