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Article Dans Une Revue Nanoscale Année : 2022

Evaluating acid and metallic site proximity in Pt/γ-Al2O3–Cl bifunctional catalysts through an atomic scale geometrical model

Ana-Teresa Fialho-Batista
Céline Chizallet
Anne-Sophie Gay
Pascal Raybaud

Résumé

Quantifying the distances between metallic sites and acid sites is crucial for tuning the catalytic activity and selectivity of bifunctional catalysts involving sub-nanometric platinum (Pt) nano-particles (NP) highly dispersed on a chlorinated alumina support. Thanks to the quantitative use of high resolution scanning transmission electron microscopy in the high angle annular dark field mode, we first highlight the presence of few Pt NP together with Pt single atoms (SA) on γ-alumina supports exhibiting various morphologies (flat-like or egg-like), and chlorine (Cl) and Pt loadings. We demonstrate that increasing the Pt loading does not impact the NP sizes but only the Pt NP inter-distances, whereas the Cl loading influences the SA/NP proportion. Then, we establish a thorough geometrical model which accounts for the way in which the global average metallicacid inter-site distances evolve from 1 nm to 6 nm as a function of three key physico-chemical descriptors: alumina morphologies, chlorine contents and size factor of alumina particles (directly linked to specific surface area). Considering that Cl is predominantly located at alumina crystallite edges, the morphology strongly impacts the Cl edge saturation: 0.4% for flat-like, and 1.2% for egg-like alumina at fixed specific surface area (∼200 m 2 g −1). At Cl edge saturation, the intersite distance is found to be 3 nm for flat-like, and 1 nm for egg-like alumina. However, for fixed Cl loading, the inter-site distance is less discriminated by the morphology. We discuss these trends in the case of naphtha reforming catalysts and thanks to the as-obtained geometrical model, we identify the key alumina descriptors to tune the inter-site distance.

Domaines

Catalyse
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Origine : Publication financée par une institution

Dates et versions

hal-03797272 , version 1 (04-10-2022)

Licence

Paternité - Pas d'utilisation commerciale

Identifiants

Citer

Ana-Teresa Fialho-Batista, Céline Chizallet, Fabrice Diehl, Anne-Lise Taleb, Anne-Sophie Gay, et al.. Evaluating acid and metallic site proximity in Pt/γ-Al2O3–Cl bifunctional catalysts through an atomic scale geometrical model. Nanoscale, 2022, 14 (24), pp.8753 - 8765. ⟨10.1039/d2nr00261b⟩. ⟨hal-03797272⟩
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