Optimization of silica content in alumina–silica support for NiMo sulfide to achieve deep desulfurization of gas oil

Abstract

NiMoS supported on a series of alumina–silica with variable silica contents of up to 70% were examined to investigate their activities in hydrotreating of straight run gas oil (SRGO) and its conventionally hydrodesulfurized oil (HSRGO). Their structure and properties were characterized by Laser Raman spectroscopy (LRS) and NH 3–TPD. Silica contents of 50 and 27% provided the highest activities in the hydrodesulfurization (HDS) of SRGO and HSRGO, respectively. The highest activity in hydrodenitrogenation (HDN) of SRGO was obtained with the particular silica content of 50%, which was same as that for HDS of SRGO. LRS showed that silica content of up to 27% provided the same shift of octahedral molybdenum oxide species as that at 949 cm −1 on alumina alone. Higher silica contents of 50 and 70% catalysts shifted to higher wave lengths, giving 950 and 960 cm −1, respectively. It must be noted that all sulfide catalysts with various silica contents all provided almost the same shift at 402 cm −1 in Raman spectroscopy. Silica contents of 27 and 50% provided the largest surface area, pore volume, and NH 3 desorption amount.