The deactivation of acidic sites of NiMo/B2O3–Al2O3 catalysts during vegetable oil hydrodeoxygenation studied by EPR spectroscopy

This paper presents the study results of NiMo/B2 O3 -Al2 O3 (0-30% wt. of B2 O3 ) catalysts for vegetable oil hydrodeoxygenation before and after catalytic tests by different electron paramagnetic resonance (EPR) methodologies. For the initial catalysts, the concentration of Bronsted acidic sites (BAS) determined by probe EPR with perylene increases linearly with an increase in the modifier (B2 O3 ) content in the samples. It was found that the isomerization activity of the catalysts increases with increasing the concentration of determined BAS. As for the spent catalysts, linear correlation of paramagnetic species concentration with the content of carbon deposits (determined by thermogravimetric analysis [TGA]/differential thermal analysis [DTA]) was found. The main reasons for the NiMo/B2 O3 -Al2 O3 catalysts deactivation over the formation of carbon deposits related to the participation of acidic sites (both Lewis and Bronsted) in the polycondensation of hydrocarbons via radical species are also proposed.