Evaluating the functionalities of NiMo/y-Al2O3-B2O3 catalysts in naphthalene hydrodearomatization and dibenzothiophene hydrodesulfurization

The aim of this work is to contribute to the current understanding on the role of the support’s acidic properties in the hydrogenating function of NiMo/-Al2O3 type catalysts during hydrodearomatization (HDA) and dibenzothiophene (DBT) type molecules desulfurization. NiMo/-Al2O3-B2O3 catalysts of different B2O3 (0, 2, 3, 6 and 8 wt.%) contents were prepared and tested in independent and simultaneous naphthalene (NP) HDA and DBT hydrodesulfurization (HDS) reactions. For HDA the catalytic activity as a function of the B2O3 content followed a volcano-shape trend, with a maximum around 3 wt.% of B2O3. In DBT desulfurization boron was found to have a positive effect in the development of the HYD route of desulfurization possibly due to an increase in total acidity. Conversely, the direct desulfurization route (DDS) was negatively affected by boron addition. The presence of NP during the HDS of DBT was found to have a significant effect in neither total HDS activity nor the HYD/DDS selectivity. The findings in this paper are significant for ultra-deep HDS of heavy oil cuts where increasing in the selectivity to HYD is a must because highly refractory alkyl-DBTs mostly react by this reaction route.