Russian Journal of Applied Chemistry, 2012, Vol. 85, No. 12, pp. 1887−1892.
Pleiades Publishing, Ltd., 2012.
Original Russian Text © V.Z. Radkevich, A.Yu. Volodin, M.F. Gorbatsevich, V.P. Sokol, Yu.G. Egiazarov, 2012, published in Zhurnal Prikladnoi Khimii,
2012, Vol. 85, No. 12, pp. 1999−2004.
Determination of the Degree of Palladium Reduction
in Supported Catalysts Based on Anion Exchangers
V. Z. Radkevich, A. Yu. Volodin, M. F. Gorbatsevich,
V. P. Sokol, and Yu. G. Egiazarov
Institute of Physicoorganic Chemistry, National Academy of Sciences of Belarus, Minsk, Belarus
Received June 21, 2012
Abstract—A procedure is suggested for determining the degree of palladium reduction in ﬁ brous anion exchang-
ers from data on the quantitative recovery of Pd(II) from samples with a hydrochloric acid solution of thiourea
before and after the reduction stage.
Palladium supported by polymeric cation or anion
exchangers exhibits high activity in oxidation of
hydrogen [1–3], removal of oxygen from water [4–6],
and other processes.
Catalysts based on ion exchangers are commonly
fabricated in two stages: ion-exchange introduction
of palladium into an ion exchanger (in the form of
) and its reduction in the
gas (hydrogen) or liquid (hydrazine hydrate, organic
acids) phase. The operation efﬁ ciency of catalysts is
determined by the number of active centers (clusters of
reduced palladium) and the dispersity of these clusters,
which, in turn, depend on the reduction conditions:
temperature, duration, and nature and concentration of
a reducing agent.
Raising the degree of reduction requires severe
conditions, which, however, commonly leads to an
intense aggregation of metal particles. Mild conditions
provide a high dispersity of palladium, but the degree
of its reduction is insufﬁ ciently high. In each particular
case, it is necessary to carry out special studies to
reach a compromise between these two factors. It is
apparent that studies of this kind require a procedure
yielding correct on-line information about the degree of
palladium reduction in the catalyst.
As supports for fabrication of palladium-containing
catalysts served ﬁ brous anion exchangers FIBAN A-5
and FIBAN A-6, based on a polyacrylonitrile (PAN)
ﬁ ber. We synthesized FIBAN A-5 by amination of
the PAN ﬁ ber with N,N-dimethylaminopropylamine.
This ﬁ ber is characterized by the presence of weakly
basic (tertiary and secondary amino) and weakly
acid (carboxy) groups. FIBAN A-6 was produced by
alkylation of FIBAN A-5 with an aqueous solution
of epichlorohydrin. This ﬁ ber contains, together with
weakly basic amino groups, strongly basic ammonium
group with quaternized nitrogen.
We prepared samples of palladium catalysts as
follows. A swollen ion exchanger was submerged
in solution of H
and kept there for 30 min
under vigorous agitation. The volume of the contacting
solution was 20 mL per 1 g of an air-dry ion exchanger.
The concentration of palladium in solution was varied
within the range 2.36–0.068 × 10
M, and pH, within
the range 05–8.9.
After palladium was introduced, the solution was
separated, acidiﬁ ed with a 1 M aqueous solution of HCl
(to pH ≤ 1), and analyzed for the content of palladium;