4,6-Dimethyl-dibenzothiophene conversion over Al2O3–TiO2-supported noble metal catalysts

Al2O3 and Al2O3–TiO2 (molar ratio Al/Ti = 2, AT2) mixed oxides were synthesized using a low-temperature sol–gel method and were further pore-filling impregnated to obtain Pd and Pt catalysts with ∼1 wt% nominal metal loading. Simultaneous impregnation was used to prepare bimetallic materials at Pd:Pt = 80:20. Solids characterization was carried out by N2-physisorption, high-resolution transmission electron microscopy (HR-TEM and E-FTEM), X-ray diffraction, temperature-programmed reduction and CO-chemisorption. Reduced (350 °C, H2 flow) catalysts were tested in the 4,6-dimethyl-dibenzothiophene hydrodesulfurization (HDS) (in n-dodecane, at 300 °C and 5.5 MPa, batch reactor). In Pd-containing materials, TiO2 incorporation into the alumina support was favorable to the catalytic activity of noble metal catalysts, where bimetallic Pd–Pt with AT2 carrier had the highest organo-S compound conversion. Enhanced intrinsic activity (per exposed metallic site) was obtained in Pt-containing catalysts supported on the AT2 mixed oxide (as compared to alumina-supported ones). Yield to different products over various catalysts seemed to be strongly influenced by metallic particles dispersion.