Comparison and performance of different sulphided Ti-loaded mesostructured silica-supported CoMo catalysts in deep HDS

Abstract

Ti-loaded mesostructured silica materials (HMS, MCM-41 and SBA-15), with Si/Ti atomic ratio of 40, were used for the preparation of supported CoMo catalysts. The catalysts were tested in the reaction of HDS of 4,6-DMDBT carried out in a continuous-flow microreactor in the liquid-phase. The samples were characterized by DRS UV-Vis, XPS, Micro-Raman spectroscopy, SBET, XRD, TPR, FT-IR of adsorbed NO and pyridine. The type of mesostructured material has an important effect on the dispersion of both Mo and Co species. The highest catalytic performance in the HDS of 4,6-DMDBT was observed for the catalysts prepared on the Ti-HMS material. The superior performance of this sample was related to the following factors: (i) larger specific area value, (ii) higher acidity, (iii) higher dispersion of the Co and Mo species, and (iv) the lower reduction temperature of the supported species. Traditional reaction pathways for the HDS of 4,6-DMDBT were observed on the conventional CoMo/γ-Al2O3 and CoMo/Ti-SBA-15 samples, while the CoMo/Ti-MCM-41 and CoMo/Ti-HMS samples show some dealkylation of the alkyl groups in the 4,6-DMDBT molecule (producing DBT). Additionally, the CoMo/Ti-HMS sample recorded the isomerization of the one alkyl group in the 4,6-DMDBT molecule. The differences observed in the reaction pathways via the HDS of 4,6-DMDBT are related to the acidity of the samples.