Speakers

Biography

Zixu Yang obtained his B.S. and M.S. degrees from Huazhong University of Science and Technology, China, in 2009 and 2012 and his Ph.D. from Oklahoma State University, U.S., in 2016. He was a postdoctoral researcher at Washington State University, US, from 2016 to 2017. He works now as a lecturer at the East China University of Science and Technology in China, focused on heterogeneous catalysis and reaction engineering to address the challenges in converting fossil and biomass feedstocks to fuels and chemicals.

Abstract

Fe-Mn bimetallic catalysts have shown great promise in directly converting syngas to olefins via Fischer-Tropsch Synthesis (FTS). However, due to the structural complexity of Fe-based catalysts and the interference of secondary promoters, the promotional effects of Mn on the phase transition of Fe-based FTS catalysts and catalytic performance are still under debate. Herein, Fe-Mn bimetallic catalysts were prepared from the solution combustion method (SCM) and co-precipitation (CP) method. Fe4Mn1-SCM exhibited excellent C₅₊ selectivity (45%) and stability over 100 h. In contrast, the product distribution given by Fe4Mn1-CP was dominated by C₁-C₄ hydrocarbons (85%). The superior chain growth ability of the Fe4Mn1-SCM was attributed to the abundant interfacial Fe-MnO_x structure, which retarded the oxygen removal and carbon diffusion process, resulting in less χ-Fe₅C₂ phase but a more e-Fe_2.2C phase that was highly active for C-C coupling. Moreover, Mn-induced promotional effects were analyzed via kinetic measurements, physiochemical characterizations, Operando Raman-mass spectroscopy, and theoretical calculations. It was found that the Fe-Mn proximity played a key role in controlling the interaction of structural and electronic impacts between Mn and Fe species. Additionally, Fe atoms on the Mn-promoted Fe₅C₂ (510) surface exhibit significant oxyphilicity when in contact with oxidizing agents like H₂O and CO₂. These findings may provide new insights for fabricating Fe-based FTS catalysts with tunable product distribution.