Can Ni phosphides become viable hydroprocessing catalysts?

• Hydrothermally synthesized Mo-substituted Ni hydroxy phosphite precursors.
• During sulfiding in H2/H2S, MoS2 segregates/dissociates H2 for phosphite reduction.
• MoS2 lowers reduction temperature of phosphite precursor to nickel phosphide.
• Prepared higher surface area nickel phosphides than by reducing nickel phosphate.
• Ni2P needs to be 30 Å to have comparable activity to supported sulfide catalysts.

We prepared higher surface area nickel phosphides than are normally found by reducing nickel phosphate. To do this, we hydrothermally synthesized Ni hydroxy phosphite precursors with low levels of molybdenum substitution. The molybdenum substitution increases the surface area of these precursors. During pretreatment in a sulfiding atmosphere (such as H2S/H2) dispersed islands of MoS2 segregate from the precursor and provide a pathway for H2 dissociation that allows reduction of the phosphite precursor to nickel phosphide at substantially lower temperatures than in the absence of MoS2. The results reported here show that to create nickel phosphides with comparable activity to conventional supported sulfide catalysts, one would have to synthesize the phosphide with surface areas exceeding 400 m2/g (i.e. with nanoparticles less than 30 Å in lateral dimension).

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