Production of light hydrocarbons at atmospheric pressure from CO2 hydrogenation using CexZr(1-x)O2 iron-based catalysts

Considering that the combination of ZrO2 and CeO2 have superior catalytic properties compared to the individual oxides, the present work investigates the production of light hydrocarbons by carbon dioxide hydrogenation at atmospheric pressure, using iron catalysts constituted of CexZr(1-x)O2 solid solutions (x = 0, 0.25, 0.5, 0.75, and 1). The aim was to determine the effect of the composition of the CexZr(1-x)O2 oxides on the reaction. The materials were characterized by XRF, XRD with Rietveld refinement, textural analysis, Raman spectroscopy, H2-TPR, H2-TPD, and CO2-TPD. The catalysts were tested in the CO2 hydrogenation reaction at 370 °C, under atmospheric pressure, using a molar ratio H2/CO2 = 3, for at least 5 h of time on stream. For the iron-based catalysts constituted of CeO2 and/or ZrO2, the CO2 conversion and selectivity towards the light olefins first increased as the Zr content increased, reaching the highest values with the iron catalyst supported on the material containing 50 % of Ce and 50 % of Zr (molar concentrations on an oxygen-free basis), and then decreased at higher Zr concentrations. The highest CO2 conversion achieved with this catalyst could be attributed to the quantity of basic sites. An appropriate balance between the amounts of adsorbed CO2 and H2 could provide a suitable surface C/H concentration ratio, leading to the best products distribution.