Peer-Reviewed Journal Details
Mandatory Fields
Thompson, D.J,Fanning, M.O,Hodnett, B.K
The interplay of electrostatic and covalent effects in 1-butene oxidation over vanadyl pyrophosphate
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Quantum mechanical reactivity indices were computed from B3LYP calculations on 1-butene and active site clusters representing stoichiometric and phosphorous-enriched (VO)2P2O7 (1 0 0) surfaces. Results indicate that 1-butene may chemisorb via formation of a π–cation complex at the stoichiometric (Open) surface, with comparison of local softnesses in 1-butene and the Open active site indicating a strong interaction. Coulombic repulsion at the phosphorous-enriched (Cleft) surface blocks vanadium sites from the CC region of 1-butene, precluding π–cation complex formation in the Cleft active site. The phosphorous-enriched surface naturally features a greater concentration of nucleophilic terminal PO oxygen species, which may promote CH, rather than CC, bond rupture in subsequent oxidation of adsorbed 1-butene. Hence, a rationale may be offered for both the ease of adsorption, and the low selectivity to maleic anhydride, observed experimentally when 1-butene undergoes oxyfunctionalisation over vanadyl pyrophosphate. Results also indicate that oxidative transformation of n-butane over (VO)2P2O7 is unlikely to proceed via an olefin intermediate.
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