Promotional effect of TiO2 on quinoline hydrodenitrogenation activity over Pt/γ-Al2O3 catalysts

Abstract

The structural and electronic properties of Pt/γ-Al2O3 catalysts for quinoline hydrodenitrogenation were modified by introducing TiO2. The results indicated that the addition of TiO2 enhanced the reducibility of PtOx species, which increased the number of metallic Pt active sites. TiO2 facilitated quinoline hydrodenitrogenation over Pt/γ-Al2O3 catalysts, with an increase in activity from 80.6% to 91.5% at 340 °C and 3 MPa when the TiO2 content was 16.3 wt%; and improved resistance to the inhibiting effects of sulfur species, therefore the hydrodenitrogenation activity decreased less sharply. High activity in dibenzothiophene hydrodesulfurization, i.e., above 91%, was maintained with different sulfur concentrations. Density functional theory calculations confirmed that dibenzothiophene and quinoline had comparable adsorption energies on a metallic Pt surface. We propose that the partially reduced TiO2 mitigated inhibition by dibenzothiophene and enhanced the hydrogenation of quinoline via the formation of electron-rich Pt species.