ALKALINE PROMOTED LITHIUM SILICATE AND ZIRCONATE SORBENTS FOR HIGH TEMPERTURE CO2 CAPTURE. REACTIVITY STUDIES THROUGH OPERANDO TECHNIQUES

DIANA PELTZER, LUIS A. SALAZAR HOYOS, BETINA FAROLDI, JOHN MÚNERA, LAURA CORNAGLIA

Simposio; XXIX International Materials Research Congress and International Conference on Advanced Materials.; 2021

NVITED TALKSeveral attempts have been performed to improve the performance of lithium silicates and zirconates for high temperature CO2 capture. Microstructural and morphological modifications, employment of efficient silicon and lithium sources, and also alkaline doping were proposed. However, alkaline doping is one of the most widely adopted strategy for modifying their capture properties. The addition of metals like K and Na enhances the CO2 capture performance at low temperatures and CO2 partial pressures. The improvement of the properties is mainly attributed to the formation of eutectic phases that melt during the capture process at high temperatures. These molten phases facilitate the diffusion processes, which is commonly reported as the limiting step during the sorption process. This presentation focuses on the study of the CO2 capture kinetic properties and reactivity of different alkali-based sorbents. Different doping techniques are described to enhance the efficiency of the lithium-based sorbents. The CO2 partial pressure and temperature effects are discussed analyzing the kinetics of the sorbents by different models.The operando Raman technique was applied to study of the behavior of the sorbents in reaction conditions, by monitoring the phase transformation along with the gas evolution during the capture/desorption cycles. In all cases, the evolution of the species was consistent with the kinetic analysis. For lithium zirconate materials, the presence of molten carbonates during the capture steps was verified, supporting the role of ion mobility in the reaction rates. In addition, the positive influence of potassium-doping on the reactivity of lithium zirconate to ZrO2 was confirmed for the first time under operando conditions. The exhaustive analysis of the operando results for the K-doped lithium silicates led to propose a scheme on solid transformation during the carbonation step. This scheme allowed to understand how the potassium incorporation method affected their performance, becoming an important tool for the design of a future Li4SiO4 sorbents with appropriate chemisorption properties.The application of operando techniques during the capture/desorption cycles allowed to clearly follow the changes that occur simultaneously in the course of the different cycle steps and shows a high potential to study other high temperature sorbents under real conditions.