Activation of C−H Bond of Propane by Strong Basic Sites Generated by Bulk Proton Conduction on V‐Modified Hydroxyapatites for the Formation of Propene. Issue 9 (31st March 2020)

• Record Type: Journal Article
• Authors: Petit, Sarah; Thomas, Cyril; Millot, Yannick; Krafft, Jean‐Marc; Laberty‐Robert, Christel; Costentin, Guylène
• Is Part Of: ChemCatChem. Volume 12:Issue 9(2020)
• Page Start: 2506
• Page End: 2521
• Publication Date: 2020-03-31
• Subjects: vanadium -- oxy-hydroxy-apatite -- ODHP -- acid-base properties -- operando ionic conduction.; Catalysis -- Periodicals; 541.39505
• DOI: 10.1002/cctc.201902181
• Languages: English
• ISSNs: 1867-3880

Abstract

Abstract: Insights into the catalytic transformation of propane to propene on V‐apatite catalysts are provided based on structure‐reactivity relationships. Substitution of phosphates by vanadates in the hydroxyapatite structure leads to the formation of Ca10 (PO4 ) 6‐x (VO4 ) x (OH)2‐y Oy V‐oxy‐hydroxy‐apatite solid solutions ( x= 0→6). Bulk vanadium incorporation promotes (i) calcium rich terminations (XPS, CO adsorption), (ii) proton deficiency inside the OH − channels ( 1 H NMR) giving rise to O 2− native species, (iii) the thermally‐activated formation of additional O 2− species along the OH − channels resulting in H‐bonding interaction (in situ DRIFT) and (iv) the proton conduction process that eventually results in the surface exposure of O 2− species ( in situ impedance spectroscopy). The exposure of Ca 2+ −O 2− surface acid‐base pairs allows the dissociation of hydrogen, emphasizing the strong basicity of the related O 2− species. Whereas an increasing vanadium content is beneficial to propene selectivity, it scarcely impacts propane conversion. The reaction proceeds mainly upon oxidative dehydrogenation, even if the minor dehydrogenation route is also observed. Surface O 2− generated thanks to proton mobility are involved in the C−H bond activation, as shown by the synergistic effect between the oxidative dehydrogenation of propane reaction and the bulk proton conduction measured under operando conditions. This puts emphasis on the key role of strong basic sites for propane activation. Abstract : Structure‐reactivity relationships : Insights into the catalytic transformation of propane to propene on V‐apatite catalysts are provided based on structure‐reactivity relationships. A synergistic effect between propane activation and proton conduction was identified.