Solvent-free phosphorus modification of Pt/Al2O3 catalysts to improve dispersion and dehydrogenation activity

This study introduces a solvent-free gas-phase method for modifying Al₂O₃-supported platinum (3 wt.%) catalysts with phosphorus (P) to enhance Pt dispersion and dehydrogenation activity. The process involves decomposing NaH₂PO₂ at 600 °C, releasing PH₃, interacting with Pt on the catalyst surface. P-modified catalysts showed up to a 24% increase in activity for perhydro-benzyltoluene dehydrogenation within a P:Pt ratio of 0.6-2.6. Additionally, they exhibited high resistance to sintering, maintaining Pt particle sizes of ~0.9 nm even at 600 °C. Characterization using CO chemisorption, STEM, NMR, and XPS revealed that PH₃ deposits phosphorus on the catalyst, which then oxidizes via support lattice oxygen. At 600 °C, this oxidized phosphorus migrates to the support/metal interface, stabilizing Pt nanoparticles and preventing sintering. However, when the P:Pt ratio exceeds 2.6, excess phosphorus remains on the surface, deactivating active sites. This study highlights the role of POₓ species in stabilizing Pt nanoparticles and optimizing catalyst performance.