Preparation of Ni2P with a Surface Nickel Phosphosulfide Layer by Reduction of Mixtures of Na4P2S6 and NiCl2

Abstract A series of physical mixtures of Na 4 P 2 S 6 and NiCl 2 (P‐NiPS(x), where x represents the P/Ni molar ratio) were employed for the preparation of Ni 2 P. For comparison, a sulfur‐containing Ni 2 P catalyst (Ni 2 P‐S) and a sulfur‐free Ni 2 P catalyst (Ni 2 P‐TPR) were prepared by reduction of Ni 2 P 2 S 6 and a nickel phosphate precursor, respectively. The reduction of the P‐NiPS(x) precursors with P/Ni ratios above 2/3 yielded Ni 2 P catalysts with a distinct nickel phosphosulfide layer (NiPS(x)), and the Ni 2 P phase started to form at ca. 200 °C. The reduction of Ni 2 P 2 S 6 to Ni 2 P most likely follows a disproportionation mechanism. The P 3+ species in Ni 2 P 2 S 6 disproportionate to PH 3 and P 5+ during the reduction, and PH 3 further reacts with nickel and sulfur species to form Ni 2 P and the surface nickel phosphosulfide layer. The sulfur atoms in the nickel phosphosulfide phase were in the form of S 2− . The introduction of sulfur to Ni 2 P favored the hydrogenation pathway of the hydrodesulfurization (HDS) of dibenzothiophene (DBT), but hardly affected the direct desulfurization (DDS) pathway and inhibited the hydrogenation of biphenyl. The DDS pathway rate constants of DBT HDS over the Ni 2 P‐TPR and NiPS(x) catalysts were observed to increase linearly with the increase in their surface Ni atomic concentrations.