Highly selective iron-based catalysts derived from Al-containing MIL-53 for CO2 hydrogenation to light olefins

Hydrogenation of CO2 is a catalytic reaction for effectively utilizing CO2 as a carbon feedstock for the production of valuable chemicals. Fe-based catalysts are well known as potential catalysts for CO2 hydrogenation to produce C2+ hydrocarbons via carbon–carbon bond formation. In this work, MIL-53(Al) was used as a support material for preparing Fe-based catalysts through incipient wetness impregnation, followed by calcination. The effects of iron loading content, type of second metals added (Cu, Co, or Zn), and the addition of a K promoter on the CO2 conversion and hydrocarbon products distribution were investigated. The MIL-53(Al)-derived Fe-based catalysts were characterized by a high dispersion of iron oxide nanoparticles even though the Fe loading level was as high as 58 wt%. The catalytic performance of the obtained Fe-based catalysts was strongly related to the crystallite size of iron oxide, which determined the type and amount of surface-active iron species. The bimetallic catalysts with Zn addition enhanced the C2+ hydrocarbons formation, whereas the C2–C4 olefins yield was increased remarkably by adding K as a catalyst promoter for facile generation of iron carbides and altering CO2 and H2 adsorption on the catalyst surface. 0.15K-0.1Zn-58%FeAlMIL-53 was a potential catalyst for producing light olefins via the CO2 hydrogenation, where the desired olefins selectivity of 40.4% was achieved at 36.0% conversion and an olefin-to-paraffin ratio of 6.3.