Comparative Study on CO2 Hydrogenation to Higher Hydrocarbons over Fe-Based Bimetallic Catalysts

This paper reports on notable promotion of C2+ hydrocarbons formation from CO2 hydrogenation induced by combining Fe and a small amount of selected transition metals. Al2O3-supported bimetallic Fe–M (M = Co, Ni, Cu, Pd) catalysts as well as the corresponding monometallic catalysts were prepared, and examined for CO2 hydrogenation at 573 K and 1.1 MPa. Among the monometallic catalysts, C2+ hydrocarbons were obtained only with Fe catalyst, while Co and Ni catalysts yielded higher CH4 selectively than other catalysts. The combination of Fe and Cu or Pd led to significant bimetallic promotion of C2+ hydrocarbons formation from CO2 hydrogenation, in addition to Fe–Co formulation discovered in our previous work. CO2 conversion on Ni catalyst nearly reached equilibrium for CO2 methanation which makes this catalyst suitable for making synthetic natural gas. Fe–Ni bimetallic catalyst was also capable of catalyzing CO2 hydrogenation to C2+ hydrocarbons, but with much lower Ni/(Ni+Fe) atomic ratio compared to other bimetallic catalysts. The addition of a small amount of K to these bimetallic catalysts further enhanced CO2 hydrogenation activity to C2+ hydrocarbons. K-promoted Fe–Co and Fe–Cu catalysts showed better performance for synthesizing C2+ hydrocarbons than Fe/K/Al2O3 catalyst which has been known as a promising catalyst so far.