(560dt) Effects of P and Metal Composition on the Performance of Mono- and Bimetallic Phosphides for Light Alkane Dehydrogenation

Catalytic dehydrogenation of light alkanes to alkenes is a practical route to create platform molecules for the production of polymers, chemicals, and fuels. Current catalysts used for this chemistry deactivate from coking and sintering and are based on expensive and/or environmentally unfriendly materials such as Pt and Cr, respectively. In this presentation we will discuss our recent results comparing Ni₂P and Ni for ethane dehydrogenation. Specifically, we have applied experimental and computational methods to understand the effect of P on the dehydrogenation ability of these materials. We are interested in transition metal phosphide materials because their geometrical and electronic properties can be tuned to provide a level of control over their catalytic properties.^1-4 Flow reactor studies, including time on stream measurements, have been performed with both ethane and propane as feeds to compare Ni₂P/SBA-15 and Ni/SBA-15. An alkene selectivity enhancement for both ethane and propane is observed for Ni₂P/SBA-15. Our results support the hypothesis that the incorporation of P provides a different preferred pathway for adsorbed ethylene on Ni₂P than Ni due to the presence of 3-fold Ni ensembles on Ni₂P, resulting in the improved selectivity and stability of Ni₂P over Ni. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to interrogate the interaction of ethylene with Ni and Ni₂P surfaces. Ethylene adsorption on Ni shows features associated with the formation of carbon precursors on the surface, whereas Ni₂P shows reversible adsorption of ethylene. Lastly, we will discuss the effect of metal composition using supported bimetallic phosphides for propane dehydrogenation.