Development of metallic element-stabilized Li4SiO4 sorbents for cyclic CO2 capture

Abstract

Lithium orthosilicate (Li4SiO4) doped with different metallic elements, K, Mg, Cr, or Ce, was prepared by a sol–gel method for high-temperature CO2 capture. The doped sorbents were systematically studied and compared with non-doped Li4SiO4. The influence of element doping on the crystal, textural and microscopic structure of Li4SiO4 was characterized using X-ray diffraction (XRD), nitrogen adsorption and scanning electron microscopy (SEM). The CO2 absorption properties were assessed by thermogravimetric analysis, and the cyclic absorption–desorption properties were analyzed on a fixed-bed reactor. All the metallic elements could insert into the crystal lattice. In particular, Ce doping effectively inhibited the growth of crystal aggregation, resulting in a foam-like morphology with small particle size. Thus, significantly improved CO2 chemisorption properties were achieved with higher capacity and faster absorption kinetics. The optimal doping molar content of Ce/Li4SiO4 was 0.02, with a maximum absorption capacity of 34.57 wt%. Moreover, this improved performance was maintained for 10 sorption/desorption cycles.