E. Finocchio et al., FTIR STUDIES ON THE SELECTIVE OXIDATION AND COMBUSTION OF LIGHT-HYDROCARBONS AT METAL-OXIDE SURFACES - PROPANE AND PROPENE OXIDATION ON MGCR2O4, Journal of the Chemical Society. Faraday transactions, 90(21), 1994, pp. 3347-3356
Citations number
71
Categorie Soggetti
Chemistry Physical","Physics, Atomic, Molecular & Chemical
The interaction of propene and propane with the surface of the oxidize
d spinel MgCr2O4+x has been studied in the temperature range 300-773 K
by FTIR spectroscopy. This solid is reduced reversibly by reaction wi
th these organic compounds in the temperature range 300-673 K, giving
rise to stoichiometric MgCr2O4 and more oxidized organic species that
finally produce CO2. Comparison with the results of adsorption and oxi
dation of C3 oxygenates (propan-1-ol, propan-2-ol, allyl alcohol, prop
ionaldehyde, acetone, acrolein, propionic acid and acrylic acid) as we
ll as of C2 and C1 oxygenates showed that the predominant oxidation pa
thways for the two molecules are different. Oxidation of propene occur
s predominantly through its previous activation at C1 to give strongly
adsorbed acrolein and acrylate species. These species later burn. Ace
tone is the primary oxidation product of propane at the surface, at 42
3 K. Acetone is later oxidized to formate species (which rapidly decom
pose) and to acetate species that burn at higher temperatures (573-773
K). The different observed paths are rationalized by taking into acco
unt the lower C-H dissociation energy at the methylene group in the ca
se of propane and at the allylic methyl group in the case of propene.
The data reported here are consistent with the data available on catal
ytic alkane oxidation over this and similar catalysts. A comparison is
made with the behaviour observed with more selective oxidation cataly
sts like Mg3(VO4)2, V2O5-TiO2 and MoO3-TiO2. A mechanism for propene a
nd propane catalytic combustion is proposed.