(740b) Computational Investigation of the Metal Phosphide Chemistry for Ethane Dehydrogenation Catalyst
AIChE Annual Meeting
2020
2020 Virtual AIChE Annual Meeting
Catalysis and Reaction Engineering Division
Hydrocarbon Conversion II: Light Alkane Dehydrogenation
Wednesday, November 18, 2020 - 8:15am to 8:30am
We employed density functional theory (DFT) to contrast EDH reactivities on Ni(111) and Ni2P(001). DFT calculations on model Ni(111) and Ni2P(001) reveal that surface P generally decreases binding energies (BEs) of fragments relevant to EDH at surface Ni sites, but that P itself participates in binding some of these intermediates. These non-linear influences of P cause CH3CH2-H activation to occur with the similar facility on metal and phosphide surfaces, while CH2CH-H activation, an indicator of coking tendency, has much greater barriers on the phosphide. This suggests that MPs could be a new class of EDH catalyst.
We then constructed Ni2P-like hexagonal M2P(001) models (M = Fe, Co, Cu, Ru, Rh, Pd, Pt, Ag) to figure out an influence of a metal element in phosphide surface chemistry. DFT calculations showed that rough correlations of BEs at the metallic site of M2P(001) and parent metals. However, BEs on M2P(001) generally span a greater range than on parent metals. Further, we observed that adsorbates generally prefer to bind onto the metallic site over the P site on M2P(001). CH3 binding is an exception case given that the P site on some M2P(001) offers stronger bindings than the metallic site. Our result demonstrates phosphide surface chemistry is sensitive to metal elements, and it is complex because of the existence of P site. However, they have a greater tunability than transition metal catalysts.