Catalytic CO2 Hydrogenation Using Cobalt Ferrite Nanoparticles for Selective Production of Light Olefins

Abstract

The steady increase of CO2 in the atmosphere owing to the excessive use of fossil fuels is seriously threatening the future of humankind by accelerating climate change. However, catalytic chemistry can turn this harmful greenhouse gas into a renewable source of carbon to provide an alternative feedstock for producing high-value hydrocarbon fuels, chemicals, and polymers as a carbon capture and utilization (CCU) strategy. Among the proposed CCU options, catalytic CO2 hydrogenation is attractive because the process is very similar to the well-established CO hydrogenation. The CO2 hydrogenation process usually involves two consecutive steps: the reverse water−gas shift (RWGS) and subsequent CO hydrogenation reactions. In CO2 hydrogenation over Fe-based catalysts, the Fe3O4 phase catalyzes the RWGS reaction, and its reduced form, the Hägg iron carbide (χ-Fe5C2) phase, provides active sites for CO hydrogenation and chain growth. To increase the CO2 conversion and light olefin selectivity, various strategies have been used to control the electronic and structural properties of Fe-based catalysts. Here, we synthesized monodisperse Fe3O4 and CoFe2O4 nanoparticles (NPs) with a size of 10−20 nm by the thermal decomposition of metal−oleate complexes and supported them on carbon nanotubes (CNTs). It was found that the Na and Co promoters played decisive roles in controlling the reaction rates and product selectivity of catalytic CO2 hydrogenation over these reduced CoFe2O4 NP/CNT catalysts.