Performance and mechanism study of LaFeO3 for biomass chemical looping gasification

Abstract

Perovskite oxide is widely used in many important technological fields due to the excellent characteristics. In this work, the performances of the LaFeO3 as oxygen carrier in biomass chemical looping gasification were investigated. It is found that there is no significant decrease in CO and H2 yield with the increase in oxygen carrier cycle number. No obvious change of syngas yield with the increase in LaFeO3 mass is observed, indicating the stability of LaFeO3. The volume fraction of water vapor should be controlled as 39.9%. The DFT calculation results show that CO desorption is identified to be the rate-limiting step with an activation barrier of 0.648 eV for CO molecule formation. For CO oxidation, formation of COO* complex is the rate-limiting step with energy barrier of 0.368 eV. During the process of H2 formation, the pathway of H2 production over surface Fe site is more favorable with the calculated activation energy of 0.428 eV. Formations of H2O and H2 are competing reactions during chemical looping process. However, the relatively low activation energy barriers of H2O dissociation (0.141 eV or 0.081 eV) and H2 formation (0.428 eV) suggest that H2 formation is more competitive. For comparison, performances of Fe2O3 as oxygen carrier were also investigated. The calculation results show a relatively high energy barrier (1.314 eV) of CO formation and relatively low energy barrier (0.434 eV) of CO oxidation.