ZHANG Yulong, SHAO Guangyin, ZHANG Zhengpai, et al. Activation atmospheres on structure-performance relationship of K-promoted Fe catalysts for lower olefin synthesis from CO2 hydrogenation[J]. CIESC Journal, 2018, (2): 690-698. DOI: 10.11949/j.issn.0438-1157.20170995.
ZHANG Yulong, SHAO Guangyin, ZHANG Zhengpai, et al. Activation atmospheres on structure-performance relationship of K-promoted Fe catalysts for lower olefin synthesis from CO2 hydrogenation[J]. CIESC Journal, 2018, (2): 690-698. DOI: 10.11949/j.issn.0438-1157.20170995.DOI:
Lower olefins synthesis from direct CO2 hydrogenation over Fe-based catalysts is an important process of CO2 utilization. Iron catalysts with different K loading (1%
3%
5%
7% and 9%) prepared by thermal decomposition were used in CO2 hydrogenation. Fe95-K5 (95%Fe-5%K
mass fraction) catalyst showed the highest activity and C2-C4 olefin selectivity. Further enhancement on Fe95-K5 catalytic performance was achieved by pre-treatment under three different activation atmospheres (10%H2/Ar
10%CO/Ar
5%CO/5%H2/Ar) prior to CO2 hydrogenation. 10%CO/Ar-activated catalyst showed the highest C2-C4 olefin selectivity (38.1%) and chain growth probability (α=0.644). In addition
the structure evolution of Fe95-K5 during activation and CO2 hydrogenation was characterized by X-rays diffraction (XRD)
Raman and temperature-programmed hydrogenation (TPH) techniques. CO introduction in pretreat process accelerated formation of iron carbides. γ1-iron carbide was formed after pretreating in 10%CO/Ar and 5%CO/5%H2/Ar
while γ2-iron carbide was produced in the hydrogenation reaction after pretreating in 10%H2/Ar. Both carbides could promote CO2 dissociation on catalyst surface.