High-temperature and low concentration CO2 sorption on Li4SiO4 based sorbents: Study of the used silica and doping method effects

Lithium orthosilicate (Li4SiO4) is one of the most promising materials for CO2 capture from flue gas at high temperature due to its high reactivity. Improved sorption properties can be obtained by appropriate doping. In this study, different lithium orthosilicate based sorbents, pure and modified with potassium carbonate, obtained using amorphous and crystalline silica were prepared and characterized by scanning electron microscopy and X-ray diffraction. The CO2 adsorption properties were investigated by thermogravimetric analysis under a flux of 4 vol.% CO2 (atmospheric pressure) in a range of temperature of 500–600 °C. To investigate the durability, multiple CO2 sorption/desorption cycles were performed on selected samples. The influence of different operating parameters such as sorption temperature, type of silica, doping method with K2CO3 on CO2 sorption capacity has been investigated. At optimal experimental conditions (580 °C, Li4SiO4 from crystalline quartz with simple addition of 10 mol% K2CO3) the CO2 sorption capacity was 270 mg CO2/g sorbent (corresponding to 80% conversion of Li4SiO4) after 2 h. The selected sorbent maintained its original sorption capacity after multiple adsorption/desorption cycles.

► The type of used silica (amorphous and crystalline) and the doping method strongly effect the morphology and, consequently, the sorption properties of Li4SiO4-based sorbents.
► Under a flux of 4 vol.% CO2 the optimal sorption temperature for the Li4SiO4-based sorbents was 580 °C.
► The use of crystalline quartz and 10 mol% K2CO3 addition to pure Li4SiO4 allowed to obtain a sorbent with high sorption capacity and good cyclic performance.