ISSN 1070-3632, Russian Journal of General Chemistry, 2007, Vol. 77, No. 12, p. 2214.
Pleiades Publishing, Ltd., 2007.
Original Russian Text
O.A. Timonova, Yu.S. Mardashev, 2007, published in Zhurnal Obshchei Khimii, 2007, Vol. 77, No. 12, p. 2069.
LETTERS
TO THE EDITOR
Inversion in Selectivity of the Methane Oxidation
under the Influence of the Support
O. A. Timonova and Yu. S. Mardashev
Moscow State Pedagogical University,
ul. M. Pirogovskaya 1, Moscow, 119435 Russia
e-mail: Otimon.ru@mail.ru
Received June 22, 2007
DOI: 10.1134/S1070363207120250
From the practical point of view, the selectivity of
oxidation of metane to CO2 + H2O [1] or to CH2O +
H2O [2,3] is important. To evaluate of the selectivity
of catalytic systems, a special efficiency parameter
defined as the quotient of the division of selectivity
by the activity is used.
catalysts of mild oxidation of hydrocarbons. In the
case of Fe(III)/BaTiO3, the valence levels lie higher
(4.6 4.8 eV). Hence, oxygen is more mobile, which is
manifested in 100% selectivity with respect to CO2.
The Ag/FePO4 and Au/FePO4 catalytic systems
exhibited significantly increased activity (the
Au/FePO4 efficiency is 16.7).
The Fe(III)/support (BaSO4 or BaTiO3) and
M/FePO4 (M = Ag, Au) systems were studied. The
experiments were carried out in a flow-type installa-
tion [4]. Two types of supports oppositely affecting
the reaction selectivity were found. With the support
the first type (BaSO4), it is possible to develop cat-
alysts ensuring 100% selectivity with respect to
formaldehyde [for Fe(III)/BaSO4, the efficiency is
54.7]. Supports of the second type provide complete
oxidation of methane.
It was shown [6] that the dependence of the selec-
tivity on the velocity of the reaction mixture (V) is
linear, whereas the acivity is proportional to 1/V. The
optimal rate veolcity for our conditions is evaluated.
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An important role in oxidation is played by the
valence levels of oxides, which were investigated in
our samples by X-ray photoelectron spectroscopy [5].
The band of oxygen levels for the valence 2p1/2 and
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spektroskopiya kristallov (Electronic Spectroscopy of
Crystals), Kiev: Naukova Dumka, 1976.
+
in formation of the excited CH4 molecule. The
catalysts with high selectivity with respect to form-
aldehyde had deeper-lying valence levels of the 2p3/2
type (5.3 5.6 eV), which is consistent with the well-
known fact that strongly bound oxygen forms the
6. Kozlova, L.V. and Mardashev, Yu.S., Nauchn. Tr.
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Timonova
