Preparation of spherical Li4SiO4 pellets by novel agar method for high-temperature CO2 capture

Li4SiO4 sorbents have received extensive attention in the field of high-temperature CO2 capture due to lower regeneration temperatures and good cyclic durability. The granulation of the sorbent powder is a necessary prerequisite for the practical application of Li4SiO4 in the removal of CO2 from the industrial exhaust gas. This study, for the first time, proposed a facile agar method to achieve the single-step synthesis of spherical Li4SiO4 pellets. The prepared Li4SiO4 pellets presented a high degree of sphericility and uniform diameter ranges of 3-4 mm. The characterization results indicated that the pellets exhibited improved microstructures with loose morphology and enhanced specific surface areas. It was believed that the burning of agar at high temperatures released large volumes of gases in a short time and, thus, led to the formation of massive pore channels. The burning out of the well-dispersed fine agar powder left rich porosity in situ for the pellets. As a result, the granulated pellets showed higher CO2 sorption capacities than the corresponding sorbent powder during the cyclic tests. In addition, during the prolonged sorption/desorption cycles, the prepared pellets displayed excellent cyclic durability and high sorption capacities (> 0.330 g CO2/g sorbent). The mechanical strengths of the pellets were also evaluated and during 1000 rotations in the friability test, the pellets exhibited the weight loss lower than 10 wt%. In general, the single-step agar method is suitable for the production of Li4SiO4 pellets for cyclic CO2 capture.