Beyond y-Al2O3crystallite surfaces: The hidden features of edgesrevealed by solid-state1H NMR and DFT calculations

Ana T.F. Batista (1) , Dorothea Wisser (1, 2) , Thomas Pigeon (1) , David Gajan (2) , Fabrice Diehl (1) , Mickael Rivallan (1) , Leonor Catita (1) , Anne-Sophie Gay (1) , Anne Lesage (2) , Céline Chizallet (1) , Pascal Raybaud (1)

1 IFPEN - IFP Energies nouvelles
2 CRMN - Centre de RMN à très hauts champs de Lyon

Elucidating the nature of high surface area gamma alumina sites is of great interest for numerous catalytic applications. In this work, the structural and spectroscopic features of edge sites are unravelled thanks to density functional theory (DFT) calculations combined with high field 1H MAS NMR of two high surface area alumina samples exhibiting distinct morphologies. DFT chemical shift calculations were carried out for relevant surface models with different hydration degrees. However, the best assignment is achieved by considering the first DFT model representing the hydroxylated edges located at the intersection of (1 1 0) and (1 0 0) alumina facets. The sharp 1H NMR peak at 0 ppm corresponds to µ1-OH groups which are located on this edge and are free from hydrogen bonding. Moreover, we show that these edge sites are the most reactive with respect to chlorine exchange.

Keywords: alumina; density functional theory; edge; hydroxyls; NMR spectroscopy

Domains: Chemical Sciences; Catalysis

Ana T.F. Batista, Dorothea Wisser, Thomas Pigeon, David Gajan, Fabrice Diehl, et al.. Beyond y-Al2O3crystallite surfaces: The hidden features of edgesrevealed by solid-state1H NMR and DFT calculations. Journal of Catalysis, 2019, 378, pp.140-143. ⟨10.1016/j.jcat.2019.08.009⟩. ⟨hal-02333915⟩