132
O.V. Vodyankina et al. / Catalysis Today 203 (2013) 127–132
Fig. 5 shows ethylene glycol conversion, selectivity to gly-
no strong influence either on the conversion of ethanol or on the
yield of acetaldehyde. This fact can be explained by the participa-
tion of Fe-containing additives in the process of selective ethanol
oxidation over Ag particles.
The main reason for high efficiency of Ag-containing cata-
lysts in selective oxidation of alcohols can be one-way action of
addition agent and active component. Also, in the case of diol oxi-
dation, monodentate ethylene glycol adsorption on Fe-containing
sites may lead to the decrease in selectivity with respect to gly-
oxal. This was not observed during the ethanol oxidation into
acetaldehyde.
oxal and distribution of the main by-products (except for carbon
oxides) over Ag–Fe/Si3N4–Zr, Ag–Fe/Si3N4–Al catalysts. Conver-
sion of ethylene glycol does not exceed 10% at temperature below
400 ◦C. While the temperature increases, the growth of ethy-
lene glycol conversion (∼90%) and glyoxal selectivity up to 50%
is observed. Glycolic aldehyde is detected as a basic liquid by-
Ag–Fe/Si3N4–Zr catalysts are used, the growth of glycolic alde-
hyde production is observed with the increase of temperature
until 550 ◦C (Fig. 5b), whereas for Ag–Fe/Si3N4–Al sample, the
yield of glycolic aldehyde decreases at temperature above 450 ◦C
(Fig. 5d). The latter catalyst generally shows predominant selectiv-
ity towards by-products, which are formed as a result of C C bond
scission to produce mono carbon compounds (formaldehyde and
carbon oxides) at temperatures above 500 ◦C.
Considerable production of compounds corresponding to oxida-
tion of a single CH2OH group in ethylene glycol can be explained by
the possibility of selective binding of one alcohol group to the cata-
lyst surface. Individual Si3N4 support (Aldrich, ␣-Si3N4) was shown
It seems probable that Fe-containing sites are able to participate in
ethylene glycol adsorption via one alcohol group. According to EDX
analysis data (Fig. 2 and Fig. S2) and X-ray fluorescent spectroscopy
(Table 1), the Fe-containing impurities are uniformly distributed
on the surface of all the catalysts studied. Formation of glyoxal is
catalyzed mainly by the Ag-containing species, as glyoxal is not
produced over the SHS ceramic supports, which do not contain Ag
particles.
Acknowledgements
This work was supported by the grant of the Russian Federal
purpose-oriented program “Research and teaching staff of innova-
tive Russia” and was partially supported by the Grant of the Russian
Ministry of Education and Science (contract No. 13.G36.31.0001 of
07.09.2010).
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
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