Effect of micro-structure and oxygen vacancy on the stability of (Zr-Ce)-additive CaO-based sorbent in CO2 adsorption

Abstract

This study describes the role of micro-structure and oxygen vacancy in CO2 adsorption over (Zr-Ce)-additive CaO. The sorbent was prepared by sol-gel and subjected to characterization in terms of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR). The sorbent (Ca/Zr/Ce=30:0.5:0.5) demonstrated an excellent CO2 capture capacity (0.65gCO2/gsorbent) up to 35 cycles. The enhanced performance is attributed to well-dispersed Ce2Zr2O7 crystallite particle which prevents CaO crystallite growth and agglomeration. The presence of flake microstructure with porosity, nanosized particles, and uniform distribution of Ca and the inert components are essential to the adsorption of CO2. The existence of Ce4+ in the crystal phase of Ce2Zr2O7 may create oxygen vacancy, which favors the diffusion of CO2 and mobility of O2−, further greatly facilitating the capture of CO2. The kinetics of CO2 adsorption was estimated by a double exponential method.