Scalable synthesis of Li4SiO4 sorbent from novel low-cost orthoclase mineral for CO2 capture

Abstract

A novel Li4SiO4 sorbent has been synthesized using low-cost and naturally occurring mineral (orthoclase) as silicon source for high-temperature CO2 sorption. This new CO2 sorbent O-Li4SiO4 exhibited looser microstructures with enhanced surface area and porosity compared to the sorbent using conventional SiO2 powder as raw materials (S-Li4SiO4) perhaps due to the existence of the support oxides and alkali impurities. As a result, the CO2 sorption rate and cyclic capacity of the new sorbent were significantly enhanced. Over 20 cycles under low CO2 sorption conditions (15%), O-Li4SiO4 still showed high sorption capacity of ∼ 0.255 g CO2/g sorbent, nearly 8 times higher than the last-cycle capacity of S-Li4SiO4. The new sorbent powder was further granulated into spherical pellets and it was demonstrated that the mechanical granulation process led to the densification of sorbent structures and, thus, the reduction of sorption capacity. However, the reduced cyclic CO2 sorption performance could be regained by adding microcrystalline cellulose as pore-forming materials. In addition to the good chemisorption performance, the pellets also presented excellent mechanical properties, i.e., high compressive strength and attrition resistance, to satisfy the requirements for realistic application. Thanks to its fast sorption rate, high CO2 capture capacity, good stability, excellent mechanical strength, and characterizations of low cost and scalable synthesis, orthoclase-derived Li4SiO4 sorbent is a promising candidate for realistic CO2 removal.