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

Li 4 SiO 4 is a promising solid sorbent for high-temperature CO 2 capture due to the high and stable CO 2 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 CO 2 uptake or a continuous loss-in-capacity of Li 4 SiO 4 sorbents in cyclic reactions. In this work, three kinds of Li 4 SiO 4 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 CO 2 adsorption performance, compression strength and attrition resistance. Results shows that the pellets modifying with 20 wt% polyethylene reach and stabilize a CO 2 sorption capacity of 0.31 g CO 2 /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 Li 4 SiO 4 sorbent pellets could be suitable for high temperature CO 2 capture in fluidized-bed reactors.