Effects of pretreatment on iron-based catalysts for forming light olefins via Fischer-Tropsch synthesis

摘要

The effects of ethylene glycol modified co-precipitation were applied to develop a catalyst with higher activity and selectivity of light olefins in the Fischer-Tropsch synthesis. The catalysts prepared by an ethylene glycol (EG) modified co-precipitation realized smaller and homogeneously distributed catalyst particles as 15-25 nm, which was two times smaller than that of the catalyst prepared from conventional co-precipitation. The Fe/Mn-EG catalyst has higher activity and enhanced selectivity to light olefins, as well as the doubled olefin to paraffin ratio (C (2) (=) -C (4) (=) /C (2) (0) -C (4) (0) ), comparing to un-pretreated catalyst. Furthermore, the addition of magnesium promoter to the Fe/Mn-EG catalyst inhibits the chain growth ability, and enhances the formation of light olefins (C (2) (=) -C (4) (=) ), realizing the high selectivity of light olefins as 50.1 %. The properties of catalyst structure, active phase, reduction and carburization of obtained catalysts were characterized by N-2 physisorption, XRD, SEM, XPS, TPR and DRIFTS measurements.