(513k) Experimental and Theoretical Studies of an Iron-Based Oxygen Carrier with a Core-Shell Structure of Fe2O3@CeO2 for Chemical Looping Biomass Gasification

Biomass that is originated from plants or animal waste is one of abundant renewable resources. Chemical looping gasification (CLG) that is considered as one of crucial biomass utilization strategies to produce syngas, is the thermochemical conversion technique that benefits from the use of lattice oxygen in an oxygen carrier such as metal oxides as a gasifying agent to avoid direct contact between fuel and air. The promotion of iron oxide with ceria will create a synergetic effect between iron oxide and cerium oxide as a bimetallic oxygen carrier with high oxygen capacity, reactivity and selectivity for syngas production in CLG. In this research, a comparative theoretical study to investigate the role of oxygen vacancy formation energy of Fe₂O₃ and CeO₂ oxygen carriers and adsorption pathways of pyrolyzed gaseous compounds of CO, H₂, CO₂ and CH₄ has been conducted. The Density Functional Theory (DFT) studies of Fe₂O₃ and CeO₂ surfaces showed the lower energy for the formation of oxygen vacancy in CeO2 (1 1 0) than Fe2O3 (0 0 1), which implies the better performance of CeO₂ in gasification reaction. In addition, CeO₂ has lower activation energy and reaction energy in the conversion of CO₂ into CO, which is beneficial in gasification reaction. Consistent with theoretical results, thermogravimetric analysis of the oxidization of biomass with the oxygen carriers showed the increase of CeO₂ loading of the Fe₂O₃@CeO₂ oxygen carrier from 50% to 60% increased the ability of the carrier to release oxygen.