Binding and decomposition of oxovanadium(IV) phthalocyanine, tetraphenylporphyrin and etioporphyrin on hydrotreating catalysts studied by X-ray photoelectron and ultraviolet–visible spectroscopies. Relevance to catalytic demetallisation
- 1 January 1985
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases
- Vol. 81 (4) , 1047-1056
- https://doi.org/10.1039/f19858101047
Abstract
The interactions of oxovanadium(IV) phthalocyanine, VOPc, oxovanadium(IV) tetraphenylporphyrin, VOTPP, and oxovanadium(IV) etioporphyrin, VOETP, with alumina, silica–alumina, fluorided silica, Co3O4, MoO3, MoS2, MoO3/Al2O3 and Co–Mo/Al2O3 catalysts in the oxide and sulphide forms have been studied by X-ray photoelectron spectroscopy and u.v.–visible diffuse reflectance spectroscopy. Partial demetallisation of VOTPP and VOPc, but not VOETP, occurs on acidic (H+) supports. The VO2+ thereby released is reduced in the X.p.s. spectrometer; porphyrin-bound vanadium is not reduced. Changes of core-electron binding energies of vanadium and nitrogen caused by interaction of the porphyrins with the supports is small, and there is no evidence of a strong interaction with the surface through vanadium or nitrogen. It is therefore suggested that the porphyrins are bound to the surfaces by a donor–acceptor, or charge-transfer, interaction through the π system of the porphyrin ring and Brønsted- and/or Lewis-acid sites of the surfaces.Keywords
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