Boosting the hydrodesulfurization of dibenzothiophene efficiency of Mn decorated (Co/Ni)-Mo/Al2O3 catalysts at mild temperature and pressure by coupling with phosphonium based ionic liquids

Abstract

Hydrodesulfurization (HDS) of fuel oils is the most viable and commercially acceptable approach operated under harsh operating conditions. To avoid harsh reaction conditions, this study is designed on the HDS of dibenzothiophene (DBT) under the combined effect of five types of Phosphonium based ionic liquids (PILs) i.e. [C4H9)3(C14H29)P]Br, [(C8H17)(C4H9)3P]Br [(C4H9)4P]Cl, [BMIM]PF6 and [C4H9)3(C16H33)P]Br with 5 wt% Mn promoted (Co or Ni)-Mo/Al2O3 catalysts at extremely ambient temperature and pressure. Catalysts were prepared by wet impregnation technique followed by their sulfidation (30% CS2 in cyclohexane) and textural characterization via SEM, BET, PXRD and XPS techniques. Catalytic activity results indicated that DBT conversion was boosted from 24% (by mere Mn-Ni-Mo/Al2O3) to 84% (by Mn-Ni-Mo/Al2O3 coupled with 10 g of [(C4H9)3(C16H33)P]Br) at 3 MPa H2 pressure, 120 °C and 4 h reaction time. Among the five types of PILs, the enhancement in HDS activity combined with solid catalyst was found dependent on the type and length of cation chain. The enhanced DBT conversion caused by Mn-Ni-Mo/Al2O3 solid catalyst coupled with IL was envisioned to be due the synergy between hydrogenation reaction (by the former) and extractive desulfurization (by the later) with an overall HDS activity order of: Mn-Ni-Mo/Al2O3 > Mn-Co-Mo/Al2O3 > Ni-Mo/Al2O3 > Co-Mo/Al2O3. HDS products were analyzed by GC-MS and possible reaction route was anticipated. This study successfully discovered and elaborated of boosting of HDS of DBT at extremely mild operation conditions under the integrated effect of solid catalyst and PILs and hence can be pragmatically envisaged as an alternative approach for fuel oils desulfurization and other similar reactions on industrial level.