Hydrodesulfurization Properties of Nickel Phosphide on Boron‐treated Alumina Supports

The deep hydrodesulfurization (HDS) properties of nickel phosphide (Ni 2 P) on boron‐modified alumina (xB−Al 2 O 3 ) supports having different B contents have been investigated. Ni 2 P precursors were prepared on the xB−Al 2 O 3 supports using hypophosphite (‐hypo) or phosphate (‐phos) as the P source and were subsequently reduced in flowing hydrogen. The 4,6‐dimethyldibenzothiophene HDS activities and turnover frequencies of the Ni 2 P/xB−Al 2 O 3 catalysts showed a strong dependence on B loading, with a maximum observed for the hypophosphite‐ and phosphate‐based Ni 2 P/B−Al 2 O 3 catalysts corresponding to 0.8 wt % and 1.2 wt % B loadings, respectively. Based on XPS and IR spectral measurements, the optimal B loadings corresponded to ∼20 % B 2 O 3 coverage of the γ‐Al 2 O 3 support and coincided with removal of the most basic hydroxyl groups on the alumina surface. At 573 K, a Ni 2 P/0.8B−Al 2 O 3 ‐hypo catalyst was 2.5 times more active than a B‐free Ni 2 P/Al 2 O 3 ‐hypo catalyst, while a Ni 2 P/1.2B−Al 2 O 3 ‐phos catalyst was 8.6 times more active than a B‐free Ni 2 P/Al 2 O 3 ‐phos catalyst. Overall, the hypophosphite‐based Ni 2 P/B−Al 2 O 3 catalysts exhibited higher HDS activities than the phosphate‐based Ni 2 P/B−Al 2 O 3 catalysts, in part due to smaller Ni 2 P particle sizes. The optimized catalysts, Ni 2 P/0.8B−Al 2 O 3 ‐hypo and Ni 2 P/1.2B−Al 2 O 3 ‐phos , were more active than a sulfided Ni−Mo/Al 2 O 3 catalyst.