High Temperature CO2 Sorption on Li2ZrO3 Based Sorbents

Abstract

In this study, the Li2ZrO3 based sorbents with different compositions were synthesized by the solid-state reaction method from the mixtures of Li2CO3, K2CO3 and ZrO2. CO2 sorption properties of Li2ZrO3 based sorbents were investigated by analyzing the phases and microstructure changes with the help of thermogravimetric analysis, X-ray diffraction and scanning electron microscopy. The thermodynamic calculations were carried out based on the second law of thermodynamics. Li2CO3/K2CO3-doped Li2ZrO3 sorbent with the composition of 36.23 wt % Li2CO3, 55.12 wt % ZrO2 and 8.65 wt % K2CO3 was considered to achieve excellent capability for high temperature CO2 sorption and presented the maximum sorption rate at 525 °C and 0.15 atm of CO2 partial pressure. The sorbent kept rather stable for multicycles sorption and regeneration, and maintained its original capacity during 12 cycle processes. There were three distinct phases in the nonisothermal CO2 sorption process while the main CO2 sorption occurred during the second phase. An improved iterative Coats–Redfern method was used to evaluate nonisothermal kinetics of the CO2 sorption process, and the kinetic parameters were derived by the MATLAB model. The Fn nth-order reaction model predicted accurately the main phases and differences in the activation energies and the frequency factors for different sorbents in the sorption phases corroborated different mechanism integral functions and reaction orders.