Experimental and Theoretical Investigation of the Synergy Effect of Zr and Ce on the Catalytic Efficiency of NiMoS Grafted on SBA-15 for Oil Hydrodesulfurization

In
this study, the synergy effect of biheteroatoms (ZrOx and CeOy) and a
Ni promoter on the catalytic performance of MoS2 crystallites
grafted on SBA-15 silica for the hydrodesulfurization (HDS) of dibenzothiophene
(DBT) in diesel was investigated. The pyridine-Fourier transform infrared
(py-FTIR) spectroscopy, ammonia temperature-programmed desorption
(NH3-TPD), and X-ray photoelectron spectroscopy (XPS) analyses
revealed that the surface acidity, number of active sites, and the
dispersion of MoS2 crystallites increased significantly
with the incorporation of ZrOx and CeOy on SBA-15 than other supported catalysts evaluated.
The ZrOx–CeOy–SBA-15-supported NiMo catalyst could remove 59%
of DBT in diesel spiked with 1000 ppm of DBT after 1 h of reaction
and up to 96% of DBT after 5 h of reaction. Density functional theory
(DFT) simulations further gave interesting insights; a thin-film model
of SBA-15 decorated with Zr and Ce indicates that the metal sites
induced a strong hydrogen bond network leading to higher surface stability.
Furthermore, Ce grafted on SBA-15 enhanced the adsorption of water
molecules that increases the Bro̷nsted acid sites and subsequently
improved its catalytic efficiency. DFT simulation of thiophene HDS
showed a stepwise rupture of thiophene C–S bonds with the second
C–S bond breaking as the plausible rate-determining step.