Application of modified-lithium triborate produced by mechano-thermal synthesis in CO2 capture processes

VILLA CRISTIAN; ARNEODO LAROCHETTE, PIERRE; SORIA BEATRIZ; GENNARI, F. C.

Congreso; XXIX INTERNATIONAL MATERIALS RESEARCH CONGRESS; 2021

The development of effective CO2 capture systems is crucial for mitigating climate change by reducing CO2 emissions into the Earth´s atmosphere. Lithium triborate has been recently reported as an efficient CO2 absorbent and is a good candidate for being used in post-combustion capture processes. With the aim of further study its CO2 capture properties, we synthesized Li3BO3 by following a two-step procedure. First, Li2CO3 and H3BO3 (3:2) were milled in air at room temperature, inducing a first reaction that yields LiB5O8.5H2O and unreacted lithium carbonate. Then, the resulting powder was thermally treated at 600 °C in air, which produces Li3BO3 as a single phase. In this synthesis method, the heat treatment temperature and time, as well as the milling duration, were optimized. The synthesis procedure developed is solvent-free and easily scalable. Afterwards, the addition of NaF or KF was implemented to partially modify the Li3BO3 base material. Spectroscopic (FTIR and Raman), thermal (TG and DSC), and X ray diffraction techniques were employed to characterize the material and study the mechanism of the proposed mechano-thermal procedure. Thermodynamic and kinetic properties of the absorbent materials during their reaction with CO2 were studied by TG technique. Thermodynamic properties of Li3BO3 and doped-based Li3BO3 materials were determined from equilibrium measurements using the van´t Hoff relation. These measurements provide key information such as minimum CO2 partial pressure at a fixed temperature for CO2 absorption. The new doped materials displayed better kinetics and regenerability performance than pristine Li3BO3, with CO2 capture capacities around 40 wt% after 30 cycles of CO2 uptake/release. The analysis of the reaction rate during carbonation revealed that CO2 can diffuse faster into molten compounds or into fast ionic conductor compounds to facilitate the rapid formation of carbonate and lithium borate products. The best material was K-doped Li3BO3, which absorbs/desorbs 50 wt.% of CO2 in 50 minutes at 550 °C. The effect of NaF and KF addition on the absorbent kinetics and stability as well as the mechanism of CO2 adsorption is analyzed in this work.