High temperature capture of CO2 on Li4SiO4-based sorbents from biomass ashes



Highly efficient Li4SiO4 (lithium orthosilicate)/biomass-based (Li4SiO4/bio-based) sorbents for CO2 capture at high temperature, were developed using a water pretreated waste materials (biomass ashes). Three typical biomass ashes and a water pretreated biomass ash were as raw materials for preparing the Li4SiO4/bio-based sorbents. These raw biomass ashes and their resulting Li4SiO4/bio-based sorbents were characterized by energy dispersive X-ray, X-ray diffraction, scanning electron microscopy, nitrogen adsorption, and thermogravimetry. The stability of CO2 sorption was tested through 15 carbonation/calcination cycles in a fixed bed reactor. The characteristic results showed that the high amount of metals (especially alkali metals) of biomass ashes could produce low contents of silica and further led the amorphous silica nanoparticles to more severe quartz aggregation. Moreover, these different physical properties of biomass ashes had a significant effect on the phase composition, microstructure, specific surface area, and CO2 absorption properties of their synthesized Li4SiO4/bio-based sorbents. With the higher contents of SiO2 and the smaller particle size, its resulting sorbent using the water pretreatment biomass ashes presented the higher amount of Li4SiO4, smaller particle size and larger specific surface area. This special structure appeared to be the main reasons for increasing in CO2 capture performance and kinetic behavior as illustrated by the thermogravimetric analyses. This pretreatment Li4SiO4/bio-based sorbent also maintained its higher capacity during the multiple cycles. It was concluded that synthesis of Li4SiO4-based sorbents obtained from the pretreated biomass ash is a promising approach for CO2 capture at high temperature. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 526–532, 2015