Effect of the reduction conditions of the supported palladium precursor on the activity of Pd/C catalysts in hydrogenation of sodium 2,4,6-trinitrobenzoate

Article abstract of DOI:10.1007/s11172-018-2039-1

The study addresses the effect of the reduction conditions of palladium polynuclear hydroxo complexes (PHC) supported on the Sibunit carbon material on the dispersion of the metal particles and the activity of 0.5%Pd/Sibunit catalysts in the selective hyd

Full text of DOI:10.1007/s11172-018-2039-1

Russian Chemical Bulletin, International Edition, Vol. 67, No.1, pp. 71—78, January, 2018
71
Effect of the reduction conditions of the supported palladium precursor
on the activity of Pd/C catalysts in hydrogenation of
sodium 2,4,6ꢀtrinitrobenzoate*
O. B. Belskaya,a,b R. M. Mironenko,a,c T. I. Gulyaeva,a M. V. Trenikhin,a,b,d and V. A. Likholobova,b,d
aInstitute of Hydrocarbons Processing, Siberian Branch of the Russian Academy of Sciences,
54 ul. Neftezavodskaya, 644040 Omsk, Russian Federation.
Fax: +7 (381 2) 64 6156. Еꢀmail: chꢀmrm@mail.ru
bOmsk State Technical University,
11 prosp. Mira, 644050 Omsk, Russian Federation.
Fax:+7 (381 2) 65 2698
cF. M. Dostoevsky Omsk State University,
55a prosp. Mira, 644077 Omsk, Russian Federation.
Fax: +7 (381 2) 22 3641
dOmsk Scientific Center, Siberian Branch of the Russian Academy of Sciences,
15 prosp. Karla Marksa, 644024 Omsk, Russian Federation.
Fax:+7 (381 2) 37 1762
The study addresses the effect of the reduction conditions of palladium polynuclear
hydroxo complexes (PHC) supported on the Sibunit carbon material on the dispersion of the
metal particles and the activity of 0.5%Pd/Sibunit catalysts in the selective hydrogenation of
sodium 2,4,6ꢀtrinitrobenzoate to 1,3,5ꢀtriaminobenzene in an aqueous solution (temperature
of 323 or 343 K, pressure of 0.5 MPa). The palladium PHC were reduced using the most
common methods pertaining to catalyst preparation: liquidꢀphase reduction with sodium
formate and reduction in a hydrogen flow at elevated temperature. It was found that highꢀ
temperature reduction in the gas phase gives rise to Pd particles with a markedly lower
dispersion compared with the sample obtained under mild liquidꢀphase reduction conditions.
The catalytic activity of the sample containing large Pd particles proved to be higher than the
activity of the catalyst obtained by reduction with sodium formate.
Key words: 2,4,6ꢀtrinitrobenzoic acid, catalytic hydrogenation, palladium catalyst,
reduction.
The supported palladium catalysts have found wide use
in organic synthesis processes.1—3 Fairly popular among
them are catalysts of the "palladium on carbon" type, which
are used, in particular, in the catalytic hydrogenation of
various organic compounds for the synthesis of dyes, fraꢀ
grances, pharmaceuticals, and biologically active comꢀ
pounds.1—6 Considerable researchers´ interest is aroused in
both the structures of these catalysts and the physicoꢀ
chemical aspects of their synthesis.6—11 The properties of
supported catalysts can be optimized, in particular, by
varying the size and morphology of metal particles.12,13 This
control over the catalyst properties can be accomplished
during the catalyst preparation, which consists in the deposꢀ
ition of a precursor of the active component on the support,
heat treatment (drying, calcination), and/or reduction.
Previously, we studied in detail14—17 the liquidꢀphase
hydrogenation of the sodium salt of 2,4,6ꢀtrinitrobenzoic
acid (NaꢀTNBA) in the presence of Pd/C catalysts. This
reaction is of interest, first of all, in relation to safe utiliꢀ
zation of explosives to obtain valuable chemicals for civil
purposes. We were able to optimize the reaction condiꢀ
tions and catalyst composition, which allowed the synꢀ
thesis of 1,3,5ꢀtriaminobenzene (TAB) in a nearly 100%
yield.15,16 In a study of a series of Pd/C catalysts differing
in the dispersion of supported palladium, we found that
hydrogenation of NaꢀTNBA is a structureꢀsensitive reacꢀ
tion: the turnover frequency (TOF) increased with inꢀ
creasing average size of supported palladium particles.17
These catalysts were synthesized by deposition of palladiꢀ
um polynuclear hydroxo complexes (PHC) with the comꢀ
position {Mn[Pd(OH)2]m}n+ (M = Li, Na, K) on the
Sibunit carbon material and subsequent reduction with
sodium formate. The dispersion of Pd particles was conꢀ
* Dedicated to Academician of the Russian Academy of Sciences
G. A. Abakumov on the occasion of his 80th birthday.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 0071—0078, January, 2018.
1066ꢀ5285/18/6701ꢀ0071 © 2018 Springer Science+Business Media, Inc.

72
Russ.Chem.Bull., Int.Ed., Vol. 67, No. 1, January, 2018
Belskaya et al.
trolled by varying the nature of M in the reactant forming
the PHC and the pH of hydrolysis, i.e., conditions of the
initial stages of synthesis of the Pd/C catalyst. Meanꢀ
while, it is of interest whether it is possible to control the
particle size of the supported metal and catalytic properꢀ
ties of the resulting Pd/C composite at the final stage of
catalyst preparation by selecting conditions of reduction
of the (Pd PHC)/C system.
Experimental
Catalysts containing 0.5 wt.% Pd were prepared by hydroꢀ
lytic precipitation of palladium PHC on the surface of the
Sibunit carbon material. 24—26 This material with a BET specifꢀ
ic surface area of 422 m2 g–1 and grain size of 50—140 μm was
synthesized at the Department of Experimental Technologies
of the Institute of Hydrocarbons Processing, Siberian Branch
of the Russian Academy of Sciences. The deposition of palladiꢀ
um was carried out as follows. Palladium chloride was disꢀ
solved in hydrochloric acid in the Pd to HCl molar ratio of 1 : 2
and the solution was diluted with water to the required concenꢀ
tration. A solution of KHCO3 was added dropwise to the obꢀ
tained aqueous solution of H2PdCl4 until pH 5 was reached.
The resulting brown solution of PHC was mixed with an aqueꢀ
ous suspension of Sibunit. This was accompanied by complete
adsorption of the complexes by the support and discoloration of
the solution. Then the Sibunit with the supported complexes
was separated from the solution by filtration and washed. The
reduction of Sibunitꢀsupported palladium PHC was carried out
in an HCOONa solution at 363 K for 0.5 h or in a flow of
hydrogen gas at 573 K for 1 h.27 The sample obtained after the
sodium formate reduction was thoroughly washed with water
and stored wet (relative water content of ∼50%). This catalyst is
designated below as Pd/CꢀF. The sample obtained upon the
reduction with hydrogen is designated as Pd/CꢀH (Fig. 1).
Methods for catalyst investigation. The palladium content in
the catalysts was determined by atomic absorption spectrometry
(AAS) on an AAꢀ6300 instrument (Shimadzu) after sample disꢀ
solution in a mixture of nitric and perchloric acids. The measurꢀ
ed palladium content was the same in both samples (0.5 wt.%).
The palladium dispersion in reduced Pd/CꢀF and Pd/CꢀH
samples (see Fig. 1) was determined by pulse chemisorption of
CO molecules at room temperature using an AutoChem II 2920
chemisorption analyzer (Micromeritics) equipped with a therꢀ
mal conductivity detector. A mixture containing 10 vol.% CO
in helium was injected in pulses at regular intervals into a flow
of helium carrier gas. The injection was continued until the
detector signal became constant. The metal dispersion was calꢀ
culated from the CO chemisorption data with the assumption
that CO : Pd = 1, relying on published data19,22,28 for the Pd/C
catalysts synthesized and pretreated under similar conditions.
The pretreatment of the Pd/CꢀF catalyst before the measureꢀ
ments included drying at 393 K in air and subsequent reduction
in a flow of 10 vol.% H2 in argon in the temperatureꢀproꢀ
grammed mode in the temperature range of 303—343 K (heatꢀ
ing rate of 10 °C min–1), with the hydrogen consumption proꢀ
file being recorded. The conditions of formation of metal partiꢀ
cles from the Sibunitꢀsupported palladium PHC during the synꢀ
thesis of the Pd/CꢀH catalyst were studied using the temperaꢀ
tureꢀprogrammed reduction (TPR) technique in a flow of
10 vol.% H2 in argon in the temperature range of 303—573 K
(heating rate of 10 °C min–1). The TPR and pulse chemisorpꢀ
tion experiments were conducted using special purity gases (not
less than 99.999 vol.% purity) and gas mixtures manufactured
by the Pure Gases, LLC.
The reduction (activation) step is significant for the
use of catalyst in the catalytic hydrogenation and oxidaꢀ
tion reactions, because the degree of reduction of supꢀ
ported palladium can vary.18 The reducing agents used
for supported palladium precursors include sodium forꢀ
mate, sodium borohydride, formaldehyde, hydrazine, and
gaseous hydrogen.5,6,10,13,18,19 The effect of the reducꢀ
tion conditions on the dispersion and catalytic action of
supported palladium in various reactions has been adꢀ
dressed in numerous studies.8,13,18—21 In particular, it
has been shown21 that the dispersion of palladium partiꢀ
cles in the Pd/C catalysts subjected to reduction with
hydrogen (in water under pressure) is 2—5 times higher
than that in the samples reduced in sodium formate soluꢀ
tions. The method used to reduce the palladium precurꢀ
sor was found to affect the activity of Pd/C catalysts toꢀ
wards the selective hydrogenation of isophorone. According
to another study dealing with the Pd/C catalysts,19 the
reduction of the supported precursor in a sodium formate
solution gives rise to highly dispersed palladium particles.
The average particle size is more than twice smaller than
that in the samples obtained by reduction with hydrogen
gas at elevated temperature. In the latter case, increase in
the reduction temperature leads to enlargement of the
supported palladium particles. The conditions of reducꢀ
tion of palladium precursor and the size of the palladium
particles being formed were found to affect the activity
and selectivity of the Pd/C catalysts towards liquidꢀphase
hydrogenation of 2,4ꢀdinitrotoluene.
Each reduction method has its own specific features
that are to be taken into account in the synthesis of cataꢀ
lysts with specified physicochemical properties. Thus afꢀ
ter the reduction of palladium precursor with sodium forꢀ
mate, thorough washing is needed, because the finished
catalyst may be contaminated with sodium cations, while
in the case of reduction with hydrogen gas, too high temꢀ
perature of reduction may lead to sintering of palladium
particles and their interaction with the carbon supꢀ
port.10,19,22,23
The purpose of this study is to elucidate the effect of
the conditions of reduction of the Sibunitꢀsupported palꢀ
ladium PHC on the Pd particle size and the Pd/Sibunit
catalyst activity towards hydrogenation of NaꢀTNBA. The
reduction techniques used most widely in the catalyst
preparation practice were chosen, namely, liquidꢀphase
reduction with sodium formate and reduction in a hydroꢀ
gen flow at elevated temperature.
The obtained palladium dispersion (D) values in the catalysts
were used to calculate the average volumeꢀsurface diameter of
Pd particles (the particles were assumed to be spherical):29,30
(1)

Hydrogenation of 2,4,6ꢀtrinitrobenzoic acid
Russ.Chem.Bull., Int.Ed., Vol. 67, No. 1, January, 2018
73
Pd PHC (aq.)
Sibunit
Filtration,
washing
573 K,
1 h
363 K,
0.5 h
Pd PHC /Sibunit
TEM
AAS
TPR
(303—343 K)
TPR
(303—573 K)
Filtration,
washing
TEM
AAS
CO pulse
CO pulse
chemisorption
chemisorption
Fig. 1. Block diagram of the preparation and subsequent examination of Pd/CꢀF and Pd/CꢀH catalysts: TEM is the transmission
electron microscopy, AAS is the atomic absorption spectrometry, TPR is the temperatureꢀprogrammed reduction.
where VPd is the atomic volume of the metal phase, which is
equal to 0.0147 nm3 for Pd; and aPd is the average effective
area occupied by one metal atom on the surface, which is
0.0793 nm2 for Pd.
As the reaction was over (hydrogen was no longer consumed),
the autoclave was cooled down and the reaction mixture was
sampled with a syringe.
The TOF was calculated from the equation
Transmission electron microscopy (TEM) images were
obtained on a JEMꢀ2100 (JEOL) electron microscope with
a lattice resolution of 0.14 nm at an accelerating voltage of
200 kV. The samples were prepared as suspensions in ethanol
and deposited on copper grids coated by perforated amorphous
carbon film, which were then mounted in the electron microꢀ
scope. The TEM images were analyzed using the DigitalMicroꢀ
graph program package (Gatan).
TOF = r(H2)/(nD),
(3)
where r(H2) is the reaction rate (moles of H2) s–1 measured
10 min after the reaction has started, i.e., in the linear segment
of the hydrogen consumption curve; n is the amount of supꢀ
ported palladium, moles; D is the dispersion of palladium deterꢀ
mined by CO pulse chemisorption or by TEM.
The hydrogenation products were analyzed by 1H NMR
spectroscopy. The spectra were measured on an Avanceꢀ400
NMR spectrometer (Bruker). The signal of the residual methyl
protons of methanolꢀd4 (δH 3.30, quintet) was used as the interꢀ
nal standard. The water signal was suppressed by zgpr presatuꢀ
ration pulses (Bruker).
The average volumeꢀsurface diameter of Pd particles was
calculated from the formula29,30
(2)
where Ni is the number of particles with an average diameter
of di.
Results and Discussion
Catalytic hydrogenation of NaꢀTNBA and analysis of the reacꢀ
tion products.14—17 An aqueous solution of NaꢀTNBA was preꢀ
pared by adding powdered NaHCO3 (0.59 g) to a gently stirred
aqueous suspension of TNBA (2.00 g) up to complete dissoluꢀ
tion and the cessation of CO2 evolution. Hydrogenation of
NaꢀTNBA in the aqueous solution (2 wt.%, 100 mL) was carꢀ
ried out with hydrogen gas in the presence of a catalyst (500 mg)
in a steel autoclave at a temperature of 323 K or 343 K and
a pressure of 0.5 MPa. The reaction mixture was magnetically
stirred at 1400 rpm. The completion of the reaction was deterꢀ
mined from the volume of hydrogen consumed per unit time.
Effect of the reduction conditions of supported PHC on
the dispersion of the formed palladium particles. The proꢀ
cedure of synthesis of Pd/C catalysts by alkaline hydrolysis
of palladium chloride complexes followed by adsorption
of the resulting palladium PHC on the carbon support
surface has been described in detail previously.10,31—33
The formation and the fraction of supported palladium
particles exposed are largely determined by the initial conꢀ
ditions of synthesis such as the nature of the alkali metal

74
Russ.Chem.Bull., Int.Ed., Vol. 67, No. 1, January, 2018
Belskaya et al.
Table 1. Average particle size of palladium in the 0.5%Pd/Sibunit catalyst samples and catalytic activity of the
samples in hydrogenation of NaꢀTNBA
a
b
Catalyst
〈d〉CO
〈d〉vs
r(H2)/(μmol H2) s–1 c
TOF/(mol H2) (mol Pds)–1 s–1 d
vs
nm
323 K
343 K
323 K
343 K
Pd/CꢀF
Pd/CꢀH
7.9
27.8
5.9
7.7
31.2
41.0
38.3
51.2
9.4 (6.0)
43.5 (9.1)
11.6 (7.3)
54.2 (11.3)
a
Average volumeꢀsurface diameter of Pd particles calculated from the CO pulse chemisorption data by Eq. (1).
b Average volumeꢀsurface diameter of Pd particles calculated from TEM data by Eq.(2).
Reaction rate measured 10 min after the start of reaction, i.e., in the linear segment of the hydrogen consumpꢀ
c
tion curve.
d
TOF values were calculated by Eq. (3) and using dispersion values derived from CO chemisorption data. The TOF
values calculated using the dispersion values derived from TEM data are given in parentheses.
in the compound involved in PHC formation and pH of
hydrolysis.17 Therefore, in order to identify the effect of
the reduction method, the PHC synthesis and adsorption
on Sibunit were carried out under identical conditions
using KHCO3 as the alkaline reagent at pH 5. The Siꢀ
bunitꢀsupported palladium PHC were reduced either in a
sodium formate solution at 363 K or in a hydrogen flow at
573 K (see Fig. 1).
palladium PHC with hydrogen involves palladium βꢀhyꢀ
dride formation34 and subsequent decomposition in the
303—353 K range (see Fig. 2, b). However, at higher
temperature, intense hydrogen consumption by reduced
palladium particles is observed. The consumption of hyꢀ
drogen in the 353—573 K temperature range in an amount
much exceeding the stoichiometric amount, that is, the
As follows from the CO pulse chemisorption data, the
dispersion of supported palladium depends on the reducꢀ
tion method. The dispersion of Pd particles is 14% for the
Pd/CꢀF sample (sodium formate reduction) and 4% for
the Pd/CꢀH sample (hydrogen reduction). The obtained
dispersion values are in line with the calculated average
a
I/V
0.04
T/К
380
360
340
320
300
diameters of the palladium particles (〈d〉 CO): 7.9 nm for
vs
Pd/CꢀF and 27.8 nm for Pd/CꢀH (Table 1).
0.02
0
The observed difference in the dispersion values may
be due not only to the difference between the Pd particle
size in the Pd/CꢀF and Pd/CꢀH samples, but also to
different adsorption behaviors. The chemisorption of CO
molecules on Pd particles is known to be structureꢀsensiꢀ
tive; therefore, in addition to the metal particle size, the
mode of CO adsorption (linear vs. bridging) also changes,
and so does the CO : Pd ratio, which is necessary to
calculate the dispersion.22,29,30
10
20
30
40
50 t/min
T/К
I/V
b
0.15
0.10
0.05
0
In addition, according to TPR data (Fig. 2), the cataꢀ
lyst samples differ in the amount of hydrogen consumed
during the synthesis. Despite the fact that the Pd/CꢀF
sample was reduced with sodium formate before the meaꢀ
surements and contained palladium metal particles (acꢀ
cording to TEM data), it additionally consumed hydroꢀ
gen during pretreatment in an autoclave at the reaction
temperature, that is, at 323 or 343 К. Indeed, according
to TPR data, hydrogen consumption takes place in the
303—343 K range (see Fig. 2, a). However, the amount of
hydrogen additionally consumed by this sample is relaꢀ
tively low under these conditions (H2 : Pd = 0.5) and is
likely to be associated with the reduction of oxidized palꢀ
ladium species formed on the particle surface upon conꢀ
tact of the sample with air. The reduction of supported
550
500
450
400
350
300
10
20
30
40
50
t/min
Fig. 2. Hydrogen consumption—evolution profiles recorded
during TPR of the Pd/CꢀF catalyst (a) and Sibunitꢀsupported
palladium PHC (b); I is the thermal conductivity detector signal,
T is temperature.

Hydrogenation of 2,4,6ꢀtrinitrobenzoic acid
Russ.Chem.Bull., Int.Ed., Vol. 67, No. 1, January, 2018
75
amount needed to reduce the supported complexes, can
also affect the adsorption properties of palladium. This
excessive consumption of hydrogen may be caused by the
formation of large palladium particles during highꢀtemꢀ
perature reduction, as it is known28 that the amount of
hydrogen consumed by palladium particles increases with
increasing particle size.
Due to uncertainty in the measurement of dispersion
inherent in the chemisorption method, the determined D
should be taken as apparent.22 Nevertheless, even though
the absolute values of the dispersion determined at a specꢀ
ified CO : Pd ratio are not quite adequate, they correctly
reflect the relative particle size, which can be used to
compare the catalysts.
The average Pd particle size was additionally deterꢀ
mined using TEM, that is, a direct technique (Fig. 3).
This method also has limitations associated with the meaꢀ
surement of sizes of highly dispersed particles, especially
when the strong interaction with the support deteriorates
the image contrast. Several assumptions have to be made
to measure the size of aggregates with a complex shape.
The 〈d〉vs values determined by TEM were 5.9 and 7.7 nm
for the Pd/CꢀF and Pd/CꢀH catalysts, respectively (see
1H NMR spectra of reaction mixtures (one spectrum is
shown in Fig. 4) exhibit an intense singlet with δ 5.74,
H
which corresponds to TAB aromatic protons.14—17 The
other signals correspond to intermediate hydrogenation
products whose concentrations are very low in all reacꢀ
tion mixtures.
The exhaustive reduction of three nitro groups (i.e.,
conversion of NaꢀTNBA to TAB) requires 9 moles of H2
per mole of NaꢀTNBA. As can be seen from the hydrogen
consumption curves (Fig. 5), the amount of hydrogen
consumed during hydrogenation is close to the stoichioꢀ
metric value. Thus, irrespective of the palladium precurꢀ
sor reduction conditions, NaꢀTNBA is completely conꢀ
verted during hydrogenation catalyzed by 0.5%Pd/Sibunit
with selective formation of TAB at both 323 K and 343 K
(Scheme 1).
Scheme 1
Table 1). The considerable difference between the 〈d〉
vs
CO
and 〈d〉
values for the sample obtained by highꢀtemꢀ
vs
perature reduction with hydrogen is consistent with pubꢀ
lished results19 and can be attributed to predominance of
the bridgeꢀsite adsorption of CO on large Pd particles. In
this case, the use of the CO : Pd = 1 ratio for the calculaꢀ
tion of 〈d〉 CO may be improper.
vs
Despite the differences between the absolute values
obtained by chemisorption measurements and TEM, the
general trend of the influence of the reduction method on
the particle size of supported palladium is retained. The
catalyst obtained by the highꢀtemperature reduction with
hydrogen is characterized by a lower dispersion of supꢀ
ported palladium than the sample obtained under mild
conditions by sodium formate reduction. As can be seen
from the Pd particle size distribution histograms, the
Pd/CꢀF sample has a relatively narrow size distribution
with a maximum in the 3—6 nm range (see Fig. 3, e),
whereas the Pd/CꢀH sample has a higher percentage of
large particles (see Fig. 3, f), which are often aggregates
of smaller spherical particles. Thus, the reduction in
a hydrogen flow at elevated temperature results in sinterꢀ
ing of Pd particles, which is consistent with the earlier
results for Pd/C systems.19,22
The TOF values were determined from the reaction
rates calculated from the amount of consumed hydrogen
in the initial linear segments of the consumption curves
(10 min after the start of the reaction) and the amount of
the surface Pd atoms for each sample. It follows from the
results (see Table 1) that the TOF of the Pd/CꢀH catalyst
is considerably higher than that of Pd/CꢀF in which the
dispersion of the supported palladium is higher. This reꢀ
sult is consistent with our recent results17 and published
data on the hydrogenation of 2,4ꢀdinitrotoluene,19 nitroꢀ
benzene,35,36 and 4ꢀchloronitrobenzene37 in the presence
of supported palladium catalysts. The increase in the TOF
with increasing average particle size of supported palladiꢀ
um in the catalyst provides the conclusion that the cataꢀ
lytic reaction in question is structureꢀsensitive.38 It is evꢀ
ident that the rate of catalytic reactions depends on the
state of both substrate and hydrogen molecules on the
catalyst surface. It is known that as the supported metal
particle size decreases, the interaction of palladium with
the substrate nitro groups becomes stronger than the inꢀ
teraction with hydrogen molecules.37 As a result of
strong adsorption of the substrate (and intermediate hyꢀ
Effect of reduction conditions of the supported PHC on
the activity of 0.5%Pd/Sibunit catalysts towards hydrogeꢀ
nation of NaꢀTNBA. The Pd/CꢀF and Pd/CꢀH catalysts
differing in the conditions of reduction and dispersion of
supported palladium were studied in the hydrogenation
of NaꢀTNBA in an aqueous solution at temperatures of
323 and 343 K and a pressure of 0.5 MPa. The reaction
1
products were identified by H NMR spectroscopy. All

76
Russ.Chem.Bull., Int.Ed., Vol. 67, No. 1, January, 2018
Belskaya et al.
a
b
50 nm
50 nm
5 nm
c
d
5 nm
f (%)
30
f (%)
30
e
f
〈d〉vs = 5.9 nm
〈d〉vs = 7.7 nm
25
20
15
10
5
25
20
15
10
5
1
2
3
4
5
6
7
8
9 10 11 12 dPd/nm
1
2
3
4
5
6
7
8
9 10 11 12
dPd/nm
Fig. 3. TEM images of Pd/CꢀF (a, c) and Pd/CꢀH (b, d) catalysts at different magnifications and the corresponding histograms for
Pd particle size distribution (e and f).
drogenation products containing nitro group) on highly
dispersed palladium particles, the reaction rate and TOF
would be lower than in the case of large Pd particles.
Thus, we studied the influence of conditions of the
reduction of Sibunitꢀsupported palladium PHC on the
dispersion of the resulting metal particles and activity of

Hydrogenation of 2,4,6ꢀtrinitrobenzoic acid
Russ.Chem.Bull., Int.Ed., Vol. 67, No. 1, January, 2018
77
5.74
catalysts for selective hydrogenation of polyfunctional orꢀ
ganic compounds.
The authors are grateful to S. V. Sysolyatin (Institute
for Problems of Chemical and Energetic Technologies,
Siberian Branch of the Russian Academy of Sciences)
for providing a 2,4,6ꢀtrinitrobenzoic acid specimen,
V. A. Rodionov and S. V. Vysotskii for the help in the
catalyst synthesis and performing catalytic experiments,
Residual protons
in CD3OD
1
and to V. P. Talzi for H NMR analysis of the reaction
products.
7.5
7.0
6.5
6.0
3.5
3.0
δH
The study was performed using the equipment of the
Omsk Regional Center of Collective Use, Siberian Branch
of the Russian Academy of Sciences.
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 16ꢀ03ꢀ
00601ꢀa).
Fig. 4. 1H NMR spectrum of the reaction mixture during
hydrogenation of NaꢀTNBA in an aqueous solution at a temꢀ
perature of 343 K and a pressure of 0.5 MPa catalyzed by
Pd/CꢀH. The spectra of mixtures obtained ofter hydrogenation
at 323 K in the presence of Pd/CꢀF and Pd/CꢀH catalysts are
similar to that presented in the Figure.
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Received May 16, 2017;
in revised form July 19, 2017
accepted October 19, 2017