ISSN 1070-4272, Russian Journal of Applied Chemistry, 2007, Vol. 80, No. 7, pp. 1073!1077. + Pleiades Publishing, Ltd., 2007.
Original Russian Text + V.V. Sidorchuk, V.A. Zazhigalov, V.S. Aleksandrova, L.S. Kuznetsov, 2007, published in Zhurnal Prikladnoi Khimii, 2007,
Vol. 80, No. 7, pp. 1104!1108.
AND ION-EXCHANGE PROCESSES
Synthesis of H
Based Heteropoly Compounds
Chemically Fixed on Silica Surface
V. V. Sidorchuk, V. A. Zazhigalov, V. S. Aleksandrova, and L. S. Kuznetsov
Institute of Sorption and Endoecology Problems, National Academy of Sciences of Ukraine, Kiev, Ukraine
Received September 12, 2006
Abstract-Possibility of activating the silica surface for chemical fixation of tungsten heteropoly compounds
of the 12th series on its surface was analyzed.
Thanks to a combination of valuable properties,
heteropoly compounds (HPCs) find wide use in
numerous practically important processes. On the one
hand, heteropoly acids (HPAs) are very strong
Brønsted acids in both dissolved and solid states
, which predetermines their successful use in
homo- and heterogeneous acid3base catalyses 
and also as solid electrolytes . For this reason, both
HPAs and their salts are promising in ion-exchange
processes [6, 7]. On the other hand, HPCs include
in their composition such elements as molybdenum,
tungsten, and vanadium, which imparts redox proper-
ties to these compounds and enables their use in
catalytic oxidation of organic compounds [234, 8, 9].
Thus, HPCs are clearly pronounced bifunctional cata-
lysts. Also known are numerous examples of their use
in adsorption [3, 6, 7, 10], membrane [11, 12], and
Together with possessing a wide variety of valu-
able properties, compounds of this class also have
a number of shortcomings, mostly of technological
nature. For example, HPCs have a small specific sur-
face area, up to 5 m
[2, 3], and a poorly devel-
oped porous structure, mainly represented by micro-
pores , which restricts their applications in hetero-
geneous catalysis and adsorption. At the same time,
HPA salts exhibit higher porosity and larger specific
surface area, even though they most frequently belong
to microporous materials [3, 13, 14] and this leads to
slow attainment of equilibrium and impossibility of
access of large reagent molecules to the inner surface
of pores (diffusion hindrance). Another disadvantage
is the comparatively low thermal stability: for HPCs
of the 12th series, the Keggin structure disintegrates
at 4003450oC , which restricts their applicability
in some gas-phase catalytic processes.
The purely technological disadvantages of HPCs is
their difficult granulation, poor filterability of finely
crystalline HPC salts in processes performed in the
liquid phase, and low mechanical strength . In
economical regard, HPC are rather expensive chemic-
als, which can also hinder their practical use. How-
ever, industrial processes in which HPCs are used as
catalysts already exist .
One way to eliminate these disadvantages of HPCs
is their deposition on porous solid supports, both in-
organic and organic. Silicas of varied origin are
the most frequently used supports for HPCs, as well
as for the majority of catalysts.
This study is devoted to synthesis of HPCs on
the surface of silica activated by groups that can bind
phosphotungstic acid (PTA).
A mesoporous aerosilogel with cylindrical grains
was used as the starting silica . This aerosilogel
was preliminarily activated in two ways.
(1) Reaction of surface silanol groups with 3-ami-
nopropylthriethoxysilane (APTES). It should be noted
that this compound has already been used in HPC
deposition onto the SiO
surface [16, 17]. The reac-
tion itself between APTES and the silica surface is
well understood . In the present study, we ob-
tained, by modifying the aerosilogel in an autoclave
at 70 and 150oC (preliminarily the aerosilogel was
vacuum-treated at 250oC), surface concentrations of
amino groups of 0.34 and 0.68 mmol g
, or 2.2 and
5.9 mmol m
(supports 1 and 2, respectively).
(2) Reaction of silanol groups with polyhydric
alcohols, butanediol and glycerol. The resulting con-