CO2 hydrogenation over Fe-Mn-Zn spinel oxide nanohybrids precatalysts
Yaqian Liu, Fuminao Kishimoto, Xiaofei Lü, Jinjun Li, Kazuhiro Takanabe
Abstract
Catalytic CO 2 hydrogenation using green hydrogen is a promising approach for mitigating CO 2 emissions and utilizing CO 2 as a feedstock. While Fe-based catalysts produce long-chain hydrocarbons under high-pressure CO 2 hydrogenation reactions, the C 2+ hydrocarbon yield tends to be insufficient at low-pressure conditions over the catalyst. This study reports the enhancement of light olefin selectivity of CO 2 hydrogenation over Fe-based catalysts at low pressure via nanoscale hybridization with manganese (Mn) and zinc (Zn) oxides. The resulting hybridized catalyst exhibited distinctive performance in terms of CO 2 hydrogenation to light olefins at relatively low pressure (0.7 MPa) in terms of CO 2 conversion rate and C 2 -C 4 yield with high olefin rates. Mn and Zn incorporation in Fe oxide decreased the reduction temperature, forming more Fe carbide phase. CO 2 adsorption capability at relevant temperatures seems to be improved when Mn and Zn are present. This mixed oxide precatalyst approach can be extended to other elements. • Fe, Mn and Zn oxides nanohybrid catalysts were successfully synthesized via reduction of Spinel-type Mn x Zn (2-x) Fe 4 O 8 with different Mn/Zn ratio. • The optimized catalyst, Mn 1.5 Zn 0.5 Fe 4 O 8 , exhibited 50.5% selectivity toward C 2 –C 4 products at a CO 2 conversion of 26.6% under the conditions of relatively low pressure (0.7 MPa) and medium temperature (310°C). • While the catalysts without Mn or Zn exhibited a negative reaction order in CO 2 partial pressure, the reaction orders of both H 2 and CO 2 over Mn 1.5 Zn 0.5 Fe 4 O 8 , were close to 0.5th, resulting in the non-competitive adsorption of CO 2 and H 2. • The optimized catalyst, Mn 1.5 Zn 0.5 Fe 4 O 8 , exhibited significantly superior durability over 60 h.