Ultrasmall Fe3O4 Nanoparticles on ZrO2 as Catalysts for CO2 Hydrogenation to Lower Olefins

Organic synthesis presents significant opportunities for converting the abundant and hazardous carbon dioxide (CO2) in the atmosphere into a more sustainable carbon source. To reduce the carbon footprint, we explored the direct hydrogenation of CO2 to lower (C2-4=) olefins using various catalysts composed of ZrO2-supported alkali-metal-promoted superparamagnetic iron oxide nanoparticles (SPIONs; Fe3O4). These catalysts are notable for their straightforward preparation; we employed a cost-effective dry-mixing method to create a range of alkali metal-doped SPIONs supported on ZrO2. Results showed that the strong interactions between Fe3O4 and the ZrO2 support enhanced CO2 hydrogenation performance compared to other forms.. Under optimal conditions - using a gas hourly space velocity (GHSV) of 4500 mL/h/gcat. and a feed ratio of H2:CO2=3 : 1 - this catalyst achieved over 22 % CO2 conversion and high selectivity for light (C2-4=) olefins at 30 bar and 375 degrees C, with 30 wt% Fe3O4 loading on ZrO2 and 2 wt% K promoter. We also investigated several variables, including alkali metal concentration, iron content, reaction conditions, and catalyst stability over 96 hours.