Insights and utility of cycling-induced thermal deformation of calcium-based microporous material as post-combustion CO2 sorbents

Abstract

On the quest of finding ideal sorbent for post-combustion CO2 capture, calcium-based sorbent seems to have the potential, but often it cannot sustain its reactivity, especially after repeated cycle of sorption. This work aims to unravel the controlling factors in carbonation reaction and thermal-induced deformation of skeleton pore network that limits the CO2 absorptivity of calcium-based sorbent. Through precise measurement of CO2 absorption activity using TGA/DSC and a series of characterization, this study paves the way for the development of next-generation CaO sorbent that has high CO2 uptake capacity and thermal stability. Key findings include CaO particles with severe point defects contribute to fast CO2 absorption activity. The transformation from CaCO3 phase to CaO phase from organic precursor is 4 times higher than the inorganic precursor. Decomposition of calcium formate is thermally stable regardless of calcination temperature. Citrate-based structure precursor is able to produce homogeneous nanosized CaO particle. Shifting of reaction controlling regime from fast carbonation reaction to diffusion limited stage happened at Thiele modulus of 1.35. Lastly, first stage of fast carbonation reaction will take place at CaO sorbent’s surface with proximate zero activation energy and second stage of slow carbonation reaction is controlled by high activation energy of ion diffusion behavior in CaCO3 ionic crystals at product diffusion layer. Future research direction can focus on reproducing long periodical citrate-like structural precursor using sol-gel method to mimic the behavior of calcium formate and calcium citrate to form nano-sized CaO particles with thermally stable crystal structure.