Non-oxidative dehydrogenation of ethane to ethylene over ZSM-5 zeolite supported iron catalysts

Abstract

The shale gas boom has stimulated tremendous interests in ethylene production using ethane as the feedstock. Catalytic non-oxidative ethane dehydrogenation (EDH) to ethylene represents a viable strategy to improve the process energy efficiency and to minimize the environmental impact. The breakthroughs in catalyst design play a key role in the successful development of this process. Herein, we demonstrate that iron supported on ZSM-5 zeolite (Fe/ZSM-5) is a highly efficient catalyst for the EDH reaction. Under comparable conditions, Fe/ZSM-5 exhibits superior activity and stability over various metal (Pt) or metal oxide catalysts (Zn, Ga, Cr, Mo) supported on ZSM-5. The use of ZSM-5 instead of conventional γ-Al2O3 as the support for Fe catalysts is critical to achieve high activity and selectivity in the EDH reaction. Detailed structure characterizations combined with density functional calculations indicate that iron oxides in the as-prepared Fe/ZSM-5 catalysts are reduced to iron metal and then carburized under reaction condition, which accounts for the excellent activity and stability for the EDH reaction. Compared with Fe/Al2O3, the relatively weaker binding strength of ethylene and the weaker surface acidity on Fe/ZSM-5 allow facile desorption of ethylene, which suppresses its consecutive transformation into higher hydrocarbons and carbon deposits, resulting in higher ethylene selectivity.