Fabrication of efficient and stable Li4SiO4-based sorbent pellets via extrusion-spheronization for cyclic CO2 capture

Li4SiO4 is a promising solid sorbent for high-temperature CO2 capture due to the high and stable CO2 adsorption performance. It is required to possess good mechanical properties in practical fluidized-bed systems and pelletization is necessary. However, pelletization generally results in a large decline in the CO2 uptake or a continuous loss-in-capacity of Li4SiO4 sorbents in cyclic reactions. In this work, three kinds of Li4SiO4 powders were synthesized and screened, and spherical pellets were further prepared via an extrusion-spheronization technique using polyethylene as a pore-former to develop porous microstructure. Then sorbent pellets were systematically tested on the CO2 adsorption performance, compression strength and attrition resistance. Results shows that the pellets modifying with 20 wt% polyethylene reach and stabilize a CO2 sorption capacity of 0.31 g CO2/g sorbent in the whole 40 tested cycles under typical conditions, which is even higher than that in powder form. Moreover, the pellets are observed to have an outstanding compression strength (27.5 MPa after calcination) and an excellent attrition resistance (only 1.01 wt% mass loss in 10 h-attrition test), which are both far more better than sorbents reported in the literature. The simultaneous physiochemical performances indicate that the prepared Li4SiO4 sorbent pellets could be suitable for high temperature CO2 capture in fluidized-bed reactors.