CO₂ capture efficiency and carbonation/calcination kinetics of micro and nanosized particles of supercritically precipitated calcium carbonate

Calcium based CO₂ solid sorbents reveal a different efficiency of the carbonation/calcination cycle according to their origin, natural or synthetic, and the synthesis method. The objective of this research was to develop high-performance sorbents for CO₂ capture at high temperature by using a supercritical method to precipitate CaCO₃ precursors. Two different sorbents were synthesized: micrometric particles of CaCO₃ surrounding Ca(OH)₂ and nanometric calcite with a CaO core. Results were compared with atmospherically precipitated calcium carbonate. Capture performance of produced materials was tested in a magnetic microbalance under mild calcination conditions (750°C and N₂) and at 900°C under CO₂ pressure. Further, tubular furnace treated samples under the mild carbonation conditions (700°C and N₂) were used to perform an extensive investigation on the morphological and textural characteristics of calcined and carbonated samples. At a calcination temperature of 750°C, an enhanced reversibility of the reaction and faster kinetics were observed for the supercritically prepared micrometric sample compared to the other two studied materials. After 25 cycles, this micrometric sample has one of the highest values of residual carbonation conversion described in the literature. At 900°C calcination temperature and in the presence of CO₂, severe sintering occurred in both micrometric and nanometric materials and similar conversion values were recorded for the two supercritically prepared samples. Nevertheless, these sorbents still have a residual conversion value two times higher than that of natural limestone.