Improved activity and coking-resistance of Fe2O3/ZrO2 catalysts by hydrothermal synthesis in propane dehydrogenation with CO2: Experimental, DFT calculations, and deactivation modeling

Abstract

In this work, two ZrO₂-supported Fe₂O₃ catalysts were synthesized through the impregnation (Fe₂O₃/t-ZrO₂) and the hydrothermal (Fe₂O₃/c-ZrO₂) methods. The hydrothermal preparation improved the catalyst activity and propylene yield; propane conversion: 45.8 % vs. 31.2 %, propylene yield: 31.1 % vs. 23.2 %. This higher activity was attributed to the high specific surface area and thereby higher Fe dispersion that led to more formation of active Fe^3 + sites. According to results, the t-ZrO₂ surfaces were known to be more favorable for coke reaction compared to c-ZrO₂. Adsorption energy of propane and propylene onto the most stable surfaces of ZrO₂ was measured as a criterion for side reactions and coke deposits by DFT calculations. The results showed that propane and propylene are more adsorbed onto t-ZrO₂ than onto c-ZrO₂, which indicates more cracking of propane and propylene onto t-ZrO₂. Finally, the experimental data were successfully fitted with the Deactivation Model with Residual Activity (DMRA). It was found that the Fe₂O₃/c-ZrO₂ catalyst has a higher resistance against the deactivation by coke deposits compared to the Fe₂O₃/t-ZrO₂ catalyst; activation energy of deactivation function: 83.64 vs. 70.09 kJ/mole.