Evaluation of palm-oil fly ash derived lithium silicate for CO₂ sorption under simulated gasification conditions

CO₂ utilization through high temperature CO₂ enhanced sorption processes is a promising pathway to achieve widespread decarbonisation and to be successful, highly performing CO₂ acceptors have to be developed. In this work, a fly ash derived lithium silicate material (Li-FA) was evaluated as CO₂ sorbent under simulated biomass gasification conditions. The CO₂ uptake tests were carried out using a high-pressure wire mesh apparatus between 380 °C and 700 °C, 15 bar and in presence of steam, H₂, CO and CO₂. The Li-FA sorbent was able to selectively adsorb CO₂ with a maximum uptake of 4.2 mmol CO₂/g at 700 °C under 4.5 bar CO₂ (15 bar P total). The stability of the Li-FA CO₂ sorbent was tested under more realistic exposition time in a 10-cycles experiment at 700 °C. Adsorption was very fast (138 mg CO₂/g in average) requiring less than 20 s to achieve about 95 % of the total CO₂ uptake of 3.2 mmol/g after 10 cycles and only 2 min to desorb the CO₂ at 710 ° C and 15 bar. SEM/elemental mapping revealed that the good elemental dispersion was retained unchanged after 10 cycles. The kinetic analysis demonstrated that the sorption constants k₁ and k₂ were larger than those of similar high-temperature sorbents, which combined to their stability and CO₂ uptake capacity offer promising application in CO₂ sorption enhanced processes.