NiMo catalysts supported on titania-modified SBA-16 for 4,6-dimethyldibenzothiophene hydrodesulfurization

Abstract

A series of Ti-containing mesoporous SBA-16 supports and the respective NiMo catalysts were prepared to study the effect of the method for support preparation and TiO 2 loading on the dispersion of titania, characteristics of Ni and Mo surface species and their catalytic activities in the 4,6-dimethyldibenzothiophene hydrodesulfurization (HDS). The solids prepared were characterized by N 2 physisorption, X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy (DRS), FT–Raman spectroscopy, temperature-programmed reduction (TPR), chemical analysis and HRTEM. Titania was incorporated to purely siliceous SBA-16 support by two post-synthetic methods: chemical grafting and incipient wetness impregnation. The results show that Ti-SBA-16 supports with different TiO 2 content and dispersion can be obtained without substantial loss of SBA-16 characteristics. The best dispersion of TiO 2 in the SBA-16 pore channels was obtained by the grafting method (DRS, FT–Raman). However, titania loading in this case was limited to 15.1 wt.% TiO 2. Samples prepared by impregnation show the presence of different Ti species: isolated Ti species and small anatase clusters (inside the mesopore channels of SBA-16) and anatase crystallites (on the external surface), even for low titania loadings (XRD). Crystal size of anatase phase increased with titania loading. It was found that TiO 2 incorporation in the SBA-16 support leads to stronger interaction of Mo and Ni oxidic species with the support (TPR) providing better dispersion to the sulfided metal species (HRTEM). NiMo catalysts supported on Ti-modified SBA-16 showed high activity in 4,6-dimethyldibenzothiophene HDS. It can be concluded, therefore, that Ti-SBA-16 materials prepared by post-synthetic routes show promising features as supports for Mo-based hydrotreating catalysts.