EPR Spectroscopic and Thermal Analysis Study of Spent NiMo/WO3–Al2O3 Catalysts for Hydrodeoxygenation of Vegetable Oil

Resumo

This paper presents the results of an electron paramagnetic resonance (EPR) and thermal analysis (TGA, DTA) study of a series of bifunctional NiMo/WO₃–Al₂O₃ catalysts containing 0 to 30 wt % WO₃ modifier before and after testing them in the process of hydrodeoxygenation of vegetable oil. The dependence of the content of carbonaceous deposits in the spent samples (according to EPR and TGA) on the concentration of acid sites as determined by EPR of perylene probe molecules in the initial catalysts is determined. Deactivation is explained by the participation of medium- and weak-strength Brønsted acid sites in the condensation of the initial unsaturated hydrocarbon molecules and their intermediates leading to the formation of various forms of coke precursors.