化学链重整过程中LaFeO3载氧体的CH4部分氧化反应机理研究OA北大核心CSTPCD

Density functional theory(DFT)calculations were employed to reveal the CH4 partial oxidation mechanism of LaFeO3 oxygen carrier during chemical looping reforming.The CH4 partial oxidation reaction network was constructed by systematically studying the elementary reaction steps,including CH4 adsorption activation,H2 and CO formation,and oxygen diffusion.It was found that CH4 undergoes a gradual dehydrogenation reaction to form H atoms,and the energy barrier(1.50 eV)of CH3 dehydrogenation is the highest,which is the rate-limiting step.There are two possible paths for H2 formation on the surface of oxygen carrier.It is the main route that the H atom from O-top site to Fe-top site bonds with another H atom on O-top site to form H2 molecule.Due to its relatively low energy barrier(1.27 eV),the CO formation process is easier to occur.Oxygen diffusion needs to overcome an energy barrier of 1.35 eV,indicating that it occurs at high temperatures and the diffusion rate is low.By comparing the energy barrier of each elementary reaction,it was found that the H2 formation is the rate-limiting step of CH4 partial oxidation kinetics for LaFeO3 oxygen carrier.The H migration is the key to limiting H2 formation,and accelerating the H migration is the main approach to improve the performance of LaFeO3 oxygen carrier.Based on DFT calculations,the H migration of A/B site doped LaFeO3 oxygen carriers could be studied,which is expected to achieve the rapid screening of potential A/B site effective dopants and guide the design and development of high-performance LaFeO3 oxygen carriers.