Catalytic hydrogenation of carbon dioxide for hydrocarbon synthesis

Abstract

Catalytic hydrogenation can turn CO2 into hydrocarbon fuel. The development of the catalysts for CO2 hydrogenation has become important since the catalysts are critical for selective production of more higher hydrocarbons for practical application. In this work, the titania supported monometallic and bimetallic Fe-M (M = Co and Cu) catalysts were synthesized and tested for CO2 hydrogenation at 573 K and 1.1 MPa. Among the monometallic catalysts (Fe, Co and Cu/TiO2), only Fe/TiO2 catalyst exhibited some selectivity to higher hydrocarbons, while Co/TiO2 and Cu/TiO2 catalysts were highly selective only to CH4 and CO, respectively. The addition of a small amount of a second metal M (M= Co, Cu) to Fe at M/(M + Fe) = 0.10 atom atom-1 showed the synergetic promotion on the CO2 conversion and the space-time yields (STY) of hydrocarbon products. Characterization by temperature-programmed desorption (TPD) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) showed that the presence of K promoter significantly decreased the adsorption of H2, which suppressed the CH4 formation. On the other hand, La addition could promote the moderately adsorbed CO2 species (mainly monodentate carbonate species), which led to the enhanced C5-C7 selectivity. The simultaneous use of La and K promoters can tailor the H and C coverage on the catalyst surface, which plays an important role in altering product distribution in CO2 hydrogenation. Thus, incorporation of K and La as promoter can further improve the catalyst activity and product selectivity to higher hydrocarbons, indicating that the promoted Fe-based bimetallic catalysts are promising for CO2 hydrogenation to higher hydrocarbons.