V. LORENZELLI

This work has shown that CO2 molecules can interact at b.t. with high surface α-Fe2O3 obtained by thermal decomposition of goethite giving: a) physisorption, possibly via charge transfer mechanism between the carbon atom and the oxygen of a surface hydroxyl; b) formation of both monodentate and bidentate carbonate ions which can be easily...

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An infrared spectroscopic study of the adsorption of NO2, NO, and N2O on α-Fe2O3 was carried out in order to identify chemisorbed species which could act as catalytic intermediates. Presorptions of pyridine and water were used in addition to usual pretreatments of the surface, in order to identify and discuss adsorption sites and mechanisms....

Pyridine adsorption on α-Fe2O3 has been studied by IR spectroscopy. The splitting of the 8a band of chemisorbed pyridine at infrared beam temperature has been interpreted as due to the existence on the haematite surface of at least two types of Lewis acid sites, possibly tetrahedrically and octahedrically coordinated cations, with a medium...

Published data on the infrared spectra and coordination of carbonate, bicarbonate and formate ions, and of CO2 in metal complexes are reported. The usual assignments of absorption bands due to products of CO and CO2 reactive adsorption on metal oxide surfaces are also critically reexamined. © 1982.

The OH stretching absorptions (3670, 3640 and 3460 cm-1) detected on haematite samples obtained by thermal decomposition of goethite, are assigned to monocoordinated and bridged free surface OH's and to hydrogen bonded OH's in surface micropores, respectively, on the basis of their behavior to successive adsorption of methanol, pyridine and D2O...

Infrared spectra of acetone adsorbed at beam temperature on α-Fe2O3 show that acetone can chemisorb on Lewis-acid sites and gives, at least partially, enolate anions; these, by aldolic condensation with molecules from the gas phase, produce a chemisorbed form of mesityl oxide. At 523 K acetate ions are formed. Two different forms of...

The interaction of methane, ethane and ethylene, and of some C1 and C2 oxygenates on the surface of model oxidation catalysts (Co3O4 and Pd-TiO2) has been investigated by FT-IR spectroscopy. Oxidation of alkanes is observed on Co3O4 starting from near 673 K, and near 373 K on Pd-TiO2. Olefins are oxidized already at room temperatures. Attempts...

The adsorption of benzene and the evolution of the adsorbed species upon heat treatment in oxygen over vanadia-titania have been studied by FT-IR spectroscopy. For comparison analogous experiments have been carried out by adsorbing phenol and pbenzoquinone. It has been demonstrated that benzene reacts with the clean surface producing different...

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The surface structure and the acid behaviour of titanias doped with sulphuric (TS), tungstic (TW), molybdic (TMo) and phosphoric (TP) acids has been studied using FT-IR spectroscopy. The acidity scale detected using the olefin oligomerization activity in the IR cell as the discriminant is TS « TW < TMo « TP « TiO2 and seems to agree with...