One-step synthesis of porous Li4SiO4-based adsorbent pellets via graphite moulding method for cyclic CO2 capture

Abstract

In this study, a novel one-step graphite moulding pelletization method was used to produce porous Li4SiO4 adsorbent pellets conveniently. The produced pellets were primarily composed of Li4SiO4 phase from X-ray diffraction analysis. The as-prepared adsorbent pellets exhibited good sphericity and a uniform diameter distribution of 2–2.5 mm. The detected porous structure resulting from the fast release of gases during the synthesis process could increase the porosity of pellets significantly and lead to a greater specific surface area of 1.02 m2/g. This pelletization method produced a high CO2 capture capacity of 0.22 g/g at the 50th cycle when the adsorption process was performed at 550 °C under 15 vol% CO2 for 30 min. Moreover, the extra contraction force due to the shrinkage during the chemical reaction of the calcination process could enhance the mechanical strength of the pellets, resulting in the high compression strength (2.84 MPa) and the superior attrition resistance (a weight loss of 6.72% after 2000 cycles). The good overall performance (i.e., CO2 capture capacity and mechanical strength) of the produced pellets in this work indicates that the graphite moulding method may be applied in the synthesis of Li4SiO4 adsorbent pellets for CO2 capture.