Detailed molecular dynamic study on benzene decomposition and soot formation over Fe2O3(0 0 1) surface under external electric field (EEF) during chemical looping gasification

Abstract

Tar is an obstacle for biomass gasification industrialization. Tar catalytic decomposition over iron-based oxygen carrier under external electric field (EEF) was firstly studied using molecular dynamic method in this work. The results indicate that significant polymerization occurs during the pyrolysis of benzene, leading to the formation of large-molecular PAHs and soot. DFT calculation proves that EFF reduces that band gap of benzene from 0.24262 (without EEF) to 0.05755 (EFF = X+0.04a.u.), which indicates that intensive EEF will active benzene molecule largely by changing the polarization and the polarity. ReaxFF MD modeling results show that intensive EEF (0.5 V/Å and 1 V/Å) could inhibit to formation of soot as well as enhance the decomposition rate of benzene. EEF inhibits the polymerization reaction of benzene, and more small molecules (mainly hydrocarbons) are produced, in which hydrogen yield is inhibited. Fe₂O₃(0 0 1) surface could active benzene molecule by adsorbing hydrogen atom to form C₆H₅. At 2000K, the conversion rate of benzene reaches 86.8 % at 400ps in the presence of Fe₂O₃. EEF also affects the catalytic cracking of benzene. When the electric field intensity is 0.3 V/Å, the yield of CO is improved by 61.5 % compared with the pyrolysis without electric field. The combination of Fe₂O₃(0 0 1) and EEF could achieve high-efficient tar removal during chemical looping gasification of biomass.