Effect of Ti on the catalytic properties of CoMo/Ti( x)-HMS catalysts in the reaction of hydrodesulfurization of 4-ethyl-6-methyl dibenzothiophene

Abstract

The effect of the presence of varying titanium concentrations introduced into hexagonal mesoporous silica (HMS) support on the catalytic activity of the catalysts was evaluated in the hydrodesulfurization of 4-ethyl-6-methyl dibenzothiophene (4E6MDBT) in a fixed-bed reactor at T = 598 K , P = 5.0 MPa , and WHSV = 46.4 h −1. The catalysts were characterized by S BET , XRD, DRS, FTIR spectroscopy of the framework vibration, DRIFTS in the OH region, H 1 - NMR , FT-IR spectroscopy of adsorbed NO and pyridine, XPS, and TGA. All Ti-containing catalysts showed higher activity than the Ti-free CoMo/HMS sample. The catalyst with a Si/Ti molar ratio of 40 is the most active. The HDS of 4E6MDBT over the Ti-free catalyst proceeds mainly via the dealkylation (DA) route, and then HDS of the more reactive DBT occurs. After Ti-incorporation into the HMS material, additional acid-catalyzed isomerization occurs, followed by direct HDS and HYD. Based on the catalyst activity–structure correlation, the increase in HDS activity over the Ti-containing catalysts with respect to the Ti-free sample was attributed to increased CoS 2 and MoS 2 surface exposure, as well as increased Lewis and Brønsted acidity.