Dibenzothiophene hydrodesulfurization over PdPt/Al₂O₃-TiO₂. Influence of Ti-addition on hydrogenating properties

The effect of Ti addition in alumina carriers on the catalytic properties of corresponding supported-PdPt materials, as tested in liquid-phase dibenzothiophene (DBT) hydrodesulfurization (HDS) was studied. To that end, Al₂O₃-TiO₂ materials (at Al/Ti = 25, 10, and 2, mol ratio) were synthesized by low-temperature sol-gel method. Point of zero charge decreased by augmenting titania concentration in binary oxides, as to that of Al₂O₃. On the other hand, textural properties and Lewis acidity (as determined by FTIR of adsorbed pyridine) increased with TiO₂ content in mixed supports. Noble metals were impregnated (nominal 1 wt%, Pd:Pt 4:1 mol ratio) on mixed supports and on reference alumina single oxide. Textural and surface modifications of alumina substrate provoked by titania addition resulted in improved metallic particles dispersion, as observed by High Resolution-TEM. Enhanced catalytic performance of noble metals-based materials with carriers of higher Ti-content was registered when tested in HDS reaction. In those cases, higher selectivity to products from hydrogenation reaction pathway was observed as well. Augmented medium and strong surface acidity and improved textural properties of carriers of enhanced TiO₂ concentration seemed to play a major role in obtaining noble metals catalysts of improved hydrogenating properties.