Intermetallic Pd1–Zn1 nanoparticles in the selective liquid-phase hydrogenation of substituted alkynes

Article abstract of DOI:10.1134/S0023158417040139

A comparative study of the catalytic characteristics of monometallic Pd/α-Al₂O₃ and bimetallic Pd–Zn/α-Al₂O₃catalysts in the liquid-phase hydrogenation of structurally different substituted alkynes (terminal and internal, symmetrical and asymmetrical) was carried out. It was established that an increase in the reduction temperature from 200 to 400 and 600°C led to a primary decrease in the activity of Pd–Zn/α-Al₂O₃ due to the formation and agglomeration of Pd1–Zn1 intermetallic nanoparticles. The Pd–Zn/α-Al₂O₃ catalyst containing Pd1–Zn1 nanoparticles exhibited increased selectivity to the target alkene formation, as compared with that of Pd/α-Al₂O₃. Furthermore, the use of the Pd–Zn/α-Al₂O₃ catalyst made it possible to more effectively perform the kinetic process control of hydrogenation because the rate of an undesirable complete hydrogenation stage decreased on this catalyst.

Full text of DOI:10.1134/S0023158417040139

ISSN 0023-1584, Kinetics and Catalysis, 2017, Vol. 58, No. 4, pp. 480–491. © Pleiades Publishing, Ltd., 2017.
Original Russian Text © I.S. Mashkovsky, P.V. Markov, G.O. Bragina, A.V. Rassolov, G.N. Baeva, A.Yu. Stakheev, 2017, published in Kinetika i Kataliz, 2017, Vol. 58, No. 4,
pp. 508–520.
Intermetallic Pd –Zn Nanoparticles
1
1
in the Selective Liquid-Phase Hydrogenation of Substituted Alkynes
I. S. Mashkovsky, P. V. Markov, G. O. Bragina, A. V. Rassolov, G. N. Baeva, and A. Yu. Stakheev*
Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, 119991 Russia
*
e-mail: st@ioc.ac.ru
Received March 6, 2017
Abstract⎯ A comparative study of the catalytic characteristics of monometallic Pd/α-Al O and bimetallic
2
3
Pd–Zn/α-Al O catalysts in the liquid-phase hydrogenation of structurally different substituted alkynes (ter-
2
3
minal and internal, symmetrical and asymmetrical) was carried out. It was established that an increase in the
reduction temperature from 200 to 400 and 600°C led to a primary decrease in the activity of Pd–Zn/α-Al O
2
3
due to the formation and agglomeration of Pd –Zn intermetallic nanoparticles. The Pd–Zn/α-Al O cata-
1
1
2
3
lyst containing Pd –Zn nanoparticles exhibited increased selectivity to the target alkene formation, as com-
1
1
pared with that of Pd/α-Al O . Furthermore, the use of the Pd–Zn/α-Al O catalyst made it possible to
2
3
2
3
more effectively perform the kinetic process control of hydrogenation because the rate of an undesirable com-
plete hydrogenation stage decreased on this catalyst.
Keywords: Pd–Zn/α-Al O , selective liquid-phase hydrogenation, intermetallic compound, selectivity, pheny-
2
3
lacetylene, diphenylacetylene, 1-phenyl-1-propyne, 1-phenyl-1-butyne, 4-octyne, terminal alkynes, internal
alkynes, styrene
DOI: 10.1134/S0023158417040139
INTRODUCTION
lic clusters with a specified composition as active com-
ponents are considered as hybrid systems with
adjustable catalytic properties [9, 10]. Among the most
commonly used catalysts, Pd–Ag [11, 12], Pd–Au [13],
and Pd–Cu [14] should be mentioned.
The catalytic hydrogenation of hydrocarbons con-
taining a triple carbon–carbon bond is a key reaction
of contemporary chemistry [1, 2]. Selective hydroge-
nation is used in large-scale industrial processes for
the removal of alkyne compounds (for example, acet-
The Pd–Zn composition is a promising bimetallic
ylene or phenylacetylene) from commercial olefins to system, which finds wide use in hydrogenation reac-
be utilized for the production of polymers [3]. This tions. The high selectivity of the Pd–Zn catalysts in
process is also of paramount importance for fine the hydrogenation of acetylene into ethylene was
organic synthesis because the products of selective tri- found [15–18] and discussed in reviews [19, 20]. Den-
ple bond hydrogenation—cis- and trans-olefins—are sity functional theory (DFT) calculations showed that
source materials for the food and pharmaceutical an increase in the selectivity of the Pd–Zn system is
industry; they are also used in a number of processes related to a decrease in the heat of adsorption of eth-
for the production of detergents, light-emitting ylene because of a change in the Pd electronic struc-
diodes, liquid-crystal displays, etc. [4–7].
ture upon the formation of a bimetallic compound of
Pd with Zn [21]. In this case, the activation barrier of
ethylene desorption is lower than the activation barrier
of its hydrogenation, and olefin desorption from the
catalyst surface becomes the preferential reaction path.
As a result, the selectivity of the bimetallic catalyst for
the formation of ethylene considerably increases in
comparison with that of a monometallic analog,
although due to a loss of activity.
For the effective reaction performance, hydrogena-
tion catalysts should be highly selective for the target
olefin even at the high conversions of a parent alkyne
compound [8]. The currently used palladium catalysts
are insufficiently selective, and the efforts of researchers
are directed toward the development and refinement of
methods for improving their catalytic characteristics.
The promotion of Pd catalysts with a second metal
is a possible method of increasing selectivity. The
bimetallic compositions obtained by alloying possess ability to form Pd–Zn intermetallic compounds with a
high selectivity and operational stability under reac- crystal structure different from that of the parent met-
tion conditions. In the context of the currently avail- als. Because of the strict ordering of the intermetallic
able classification, these catalysts containing bimetal- compound, active centers with a more uniform struc-
A unique property of the Pd–Zn composition is the
480

INTERMETALLIC Pd –Zn NANOPARTICLES
481
1
1
ture are formed on the catalyst surface; this can facili- a considerable effect on the structure of Pd–Zn
tate an increase in the catalyst selectivity [22]. For nanoparticles. It was found that, on the one hand, par-
example, Zhou et al. [23] found that the intermetallic ticles with an insufficiently ordered structure were
Pd–Zn nanosystems possess high selectivity in the formed at relatively low temperatures (200–400°C)
hydrogenation of acetylene into ethylene. According to and an increase in the temperature facilitated the for-
the data of microcalorimetric measurements and DFT mation of Pd–Zn intermetallic compound nanoparti-
calculations, the specific spatial arrangement of Pd sec- cles. On the other hand, the concentration of Zn on
tions in the Pd–Zn–Pd ensembles of the intermetallide the surface of nanoparticles can decrease at high tem-
leads to the moderate σ-binding of acetylene with two peratures because of its evaporation and/or diffusion
adjacent Pd centers and the weak π-binding adsorbed into the near-surface layers and the bulk of a nanopar-
ethylene on individual Pd centers. This facilitates the ticle, which can also negatively affect the catalytic
chemisorption of acetylene and accelerates the desorp- properties. The main goal of this work was to study in
tion of ethylene from the catalyst surface. As a result the detail the catalytic characteristics of Pd–Zn/α-Al O
2
3
selective hydrogenation of acetylene into ethylene samples, which were activated at different tempera-
becomes kinetically preferable.
tures, in the liquid-phase hydrogenation of structur-
ally different terminal and internal alkynes.
Note that the applicability of supported Pd–Zn
catalysts to selective liquid-phase hydrogenation reac-
tions of complex organic molecules remains almost
unexplored. The characteristics of Pd–Zn catalysts
were studied only in the processes of the liquid-phase
hydrogenation of phenylacetylene. In this context,
EXPERIMENTAL
Catalyst Preparation
The 3 wt % Pd–1.8 wt % Zn/α-Al
O bimetallic
2
3
note that Yoshida et al. [24] compared the catalytic catalysts were prepared by the incipient wetness
characteristics of Pd and Pd–Zn samples in the liquid- impregnation of a preliminarily calcined (550°C, air)
2
phase hydrogenation of phenylacetylene in a toluene support (α-Al O , S = 8 m /g, Alfa Aesar) with the
2
3
sp
solution. The Pd–Zn catalyst prepared by a coprecip-
itation method possessed low activity, in comparison
with that of a monometallic analog, but higher target
selectivity. Furthermore, a decrease in the rate of the
second (undesirable) stage of the complete hydrogena-
tion of the target olefin into ethylbenzene on the bime-
tallic catalyst was found. Wang and coauthors [25] also
found increased selectivity in the hydrogenation of phe-
nylacetylene on the supported Pd–Zn/Al O samples,
aqueous solutions of the nitrates Pd(NO ) and
3
2
Zn(NO ) . Metal concentrations in the solution were
3
2
calculated in such a way as to obtain a molar ratio of
1
: 1 between the metals in the catalyst. For studying
the temperature dependence of the intermetallic
nanoparticles formation, a series of Pd–Zn samples
reduced at 200, 400, 600, and 800°C (in 5% H /Ar for
2
2
h) was synthesized. After drying, the samples were
2
3
immediately reduced without preliminary heat treat-
as compared with the monometallic Pd. The authors
showed that a ratio between metal components in the
catalyst has an additional effect on selectivity. The
sample with Zn/Pd = 6 exhibited maximum selectiv-
ity. Unfortunately, Wang et al. [25] did not perform a
detailed study of Pd–Zn particles structure and it
remains unclear whether the active component
occurred on the support surface as the nanoparticles
of Pd–Zn alloy with a face-centered cubic (FCC)
structure or highly ordered Pd–Zn intermetallic com-
pounds were formed in this case. Furthermore, the
properties of Pd–Zn catalysts in the hydrogenation of
substituted alkynes with more complex structures were
not investigated.
ment. The reference monometallic 1 wt % Pd/α-Al O
2
3
catalyst was also obtained by incipient wetness
impregnation with an aqueous solution of the nitrate
Pd(NO ) . A series of the samples reduced at 200, 400,
3
2
600, and 800°C was prepared.
Liquid-Phase Hydrogenation
The liquid-phase hydrogenation of phenylacety-
lene (98%, Aldrich) and other substrates (styrene,
diphenylacetylene, 1-phenyl-1- propyne, 1-phenyl-1-
butyne, and 4-octyne; all of the substrates with 99%
purity were purchased from Aldrich) were carried out in
an autoclave type reactor with a magnetic stirrer and a
In connection with this, the aim of the present work gas supply system. The autoclave was equipped with a
was to study the characteristics of catalysts based on sampling system and an electronic pressure gage for the
Pd–Zn nanoparticles in the liquid-phase hydrogena- monitoring of the degree of hydrogen absorption. The
tion reactions of structurally different substituted reaction was performed in n-hexane (98%, Merck) at
alkynes. A previous study of the Pd–Zn nanoparticles 25°C and an initial hydrogen pressure of 10 bar. The
formation on the surface of α-Al O showed that the catalyst sample weight and the intensity of stirring were
2
3
chosen to perform the process in the kinetic region. The
procedure used for the determination of process condi-
tions was described in detail earlier [27].
variation of the reductive catalyst activation condi-
tions makes it possible to obtain the supported parti-
cles of intermetallic compounds and to almost com-
pletely avoid the formation of monometallic Pd clus-
The reaction mixture was analyzed by chromatog-
ters [26]. In this case, the reduction temperature exerts raphy on a Kristall 5000 instrument (Khromatek,
KINETICS AND CATALYSIS Vol. 58 No. 4 2017

4
82
MASHKOVSKY et al.
2
.0
.8
.6
.4
.2
.0
r2
by the atoms of the second metal, the value of TOF
was calculated based on the total number of palladium
1
atoms (N ) in the catalyst via the formula
Pd
1
1
r1
r
TOF =
.
(1)
1
NPd
1
Selectivity in the formation of target olefin (S ) was
=
0.8
0.6
0.4
0.2
determined based on the data of the chromatographic
analysis of the reaction mixture according to Eq. (2),
where n and n are the mole fractions of the resulting
=
–
Pd/α-Al O (800°С)
olefin and alkane, respectively:
2
3
n=
n= + n−
S =
.
(2)
=
0
10
20
30
40
50
Time, min
The effectiveness of the kinetic process control was
evaluated by comparing the r /r ratios between the
1
2
Fig. 1. General view of a kinetic curve of the dependence of
the amount of absorbed hydrogen AH2 on the reaction time
of the liquid-phase hydrogenation of phenylacetylene (PA).
rates of parent alkyne hydrogenation at the first and
second stages [28, 29].
RESULTS AND DISCUSSION
Phenylacetylene Hydrogenation
Russia) with a flame-ionization detector. The reaction
mixture was analyzed on an HP5-MS column
(
5% phenyl dimethylsiloxane; 30 m; inner diameter,
Comparison between the activities of Pd and Pd–Zn
0
.25 mm; stationary phase film thickness, 0.25 μm; catalysts. The hydrogenation of phenylacetylene was
and carrier gas, helium). It was found that aromatic studied in detail [24, 25, 30, 31]. The reaction occurs via
ring hydrogenation did not occur under the reaction a classical two-stage mechanism. At the first stage, the
conditions. Furthermore, it was established that, on predominant hydrogenation of parent phenylacetylene
the hydrogenation of phenylacetylene in a hydrogen to styrene occurs, and it is accompanied by the absorp-
absorption range of 0.1–0.5 equiv H (the first stage of tion of 1 equiv H . At the second stage, the resulting sty-
2
2
hydrogenation), the amount of ethylbenzene formed rene is hydrogenated to ethylbenzene; in this case, the
was no higher than 0.2 mol % on a total basis (pheny- second equivalent of H is absorbed. Figure 2 shows the
2
lacetylene + styrene + ethylbenzene), and the occur-
rence of complete hydrogenation reaction can be
ignored. The analysis of the reaction mixture at the
second stage of reaction (in a hydrogen absorption
characteristic kinetic curves of the time dependence of
the amount of absorbed hydrogen for reactions per-
formed on Pd/α-Al O and Pd–Zn/α-Al O reduced at
2
3
2
3
different temperatures.
range of 1.2–1.5 equiv H ) showed that the residual
2
An analysis of the initial section of kinetic curves
for both mono- and bimetallic catalysts showed that the
reaction rate was almost independent of the degree of
conversion of initial phenylacetylene, and they were lin-
phenylacetylene amount was no higher than 0.5% and
the absorption of hydrogen during hydrogenation was
also negligibly small. A similar result was also obtained
for the other substrates.
ear up to the absorption of 0.8–0.9 equiv H (Fig. 2).
2
−
Cat
1
The linear dependence indicates that the rate of a tri-
ple bond hydrogenation has a zero order with respect
to phenylacetylene, which is consistent with published
data. Thus, it was found [27, 32, 33] that, on the
hydrogenation of an alkyne compound, the zero order
with respect to a reactant was retained up to the high
degrees of conversion because of its strong adsorption.
The results of the comparative calculations of the heats
of adsorption of alkyne and alkene compounds (based
on an example of acetylene) [34–36] indicated that the
heat of adsorption of an alkyne (1.6 eV) is much higher
than that of an alkene (1.0 eV). As a result, high surface
coverage was retained even at small concentrations of
the initial alkyne.
–
1
The reaction rate r (mmolH2 mg
min ) was
determined based on the rate of hydrogen absorption
from a graph of the dependence of the amount of
absorbed hydrogen on the reaction time (Fig. 1).
Because the hydrogenation reaction of alkyne com-
pounds occurs in two stages, the reaction rate was
determined for each of them: in an absorption range of
0
.1–0.5 equiv H for the first stage (r ) or 1.2–
2 1
.5 equiv H for the second stage (r ).
1
2
2
The catalytic activity of the test samples at each
stage of the reaction was evaluated from the turnover
–1
frequency (TOF, s ). Taking into account the fact
that, in the case of bimetallic catalysts, the amount of
surface Pd atoms cannot be determined by electron
microscopy because a part of the surface is occupied Al
The activities of the Pd/α-Al O and Pd–Zn/α-
2
3
O catalysts were compared based on the values of
3
2
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INTERMETALLIC Pd –Zn NANOPARTICLES
483
1
1
2
.0
.8
.6
.4
.2
.0
1
1
1
1
.4
.2
.0
0.8
1
Pd
1
1
1
0
0
0
0
.8
.6
.4
.2
Pd–Zn
0.6
0.4
0.2
0
10
20
30
100
0
20
40
Time, min
60
80
Fig. 2. Dependence of the amount of absorbed hydrogen AH2 on the reaction time of the liquid-phase hydrogenation of pheny-
lacetylene (PA) on (d) the monometallic 1% Pd/α-Al O (800°С) catalyst and the bimetallic 3% Pd–1.8% Zn/α-Al O catalyst
2
3
2 3
reduced at different temperatures: (n)200, (h) 400, (s) 600, and ( )800°C.
TOF calculated from the rates of phenylacetylene catalyst reduction temperature for the Pd/α-Al O
3
1
2
hydrogenation at the first stage of the process (Table 1). and Pd–Zn/α-Al O catalysts. The monometallic
2
3
A comparison between the values of TOF for mono- samples exhibited a gradual decrease in the value of
1
metallic and bimetallic Pd–Zn catalysts reduced at TOF by a factor of about 1.8 as the reduction tem-
1
identical temperatures (Table 1) showed that the activ- perature was increased. According to electron-micro-
ity of the Pd–Zn/α-Al O samples was lower by a fac- scopic data, this was related to the agglomeration of
2
3
0
tor of 3–9 than that of monometallic ones. Note that Pd nanoparticles and an increase in their size from 5–
analogous data were obtained previously by Wang 7 nm for the sample reduced at 200°C to 30–40 nm for
et al. [25]. A decrease in the catalytic activity of the Pd/α-Al O reduced at 800°C; this led to a decrease in
2
3
samples based on supported Pd–Zn nanoparticles in
the hydrogenation of phenylacetylene was found and
explained by the influence of geometric effects. On the
surface of bimetallic particles, palladium atoms pre-
dominantly occurred in the environment of zinc atoms,
the surface area accessible to the reaction [26].
For the Pd–Zn/α-Al O catalyst, an increase in
2
3
the reduction temperature from 200 to 400°C led to a
sharp decrease in the reaction rate, which decreased by
−
1
which do not exhibit catalytic activity in this reaction. a factor of >2 from 70 to 34 mmol min–1 mg
.
Cat
H2
As a result, the number of the Pd active centers at which This considerable decrease in the activity of the bime-
hydrogenation occurs decreased to cause a decrease in tallic catalyst, as compared with the monometallic
the total activity. An analogous effect of a decrease in Pd/α-Al O , can be explained by the following two
2
3
the activity was also observed on Pd–Cu [27], Pd–In
factors: (1) the agglomeration of metal nanoparticles
and (2) the disappearance of monometallic Pd
nanoparticles with the subsequent formation of Pd–Zn
intermetallide nanoparticles [26]. As the reduction
temperature was further increased to 600°C, the rate of
hydrogenation continued to decrease, although not so
sharply. This can occur because of both the continu-
ous agglomeration of a metal phase and the formation
of Pd–Zn intermetallic compound nanoparticles with
a more ordered structure.
[
37, 38], and Pd–Ag [39] bimetallic catalysts, in which
the second metal did not possess essential activity in the
reaction of hydrogenation, and discussed by Schlögl
with coworkers [40, 41] as applied to the Pd–Ga sys-
tems.
Effect of reduction temperature on the activity of Pd
and Pd–Zn catalysts. Because it was established earlier
that the structure of metallic Pd–Zn nanoparticles to
a considerable degree depends on the catalyst reduc-
tion temperature, it is of interest to analyze the influ-
ence of this factor on the catalytic characteristics. Fig- Al
An unexpected result was obtained for Pd–Zn/α-
O reduced at 800°C. It was found that an increase
3
2
ure 3 shows the dependence of the reaction rate on the in the temperature from 600 to 800°C led to a more
KINETICS AND CATALYSIS Vol. 58 No. 4 2017

4
84
MASHKOVSKY et al.
Table 1. Kinetic characteristics of the liquid-phase phenylacetylene hydrogenation in the presence of monometallic
1
%Pd/α-Al O and bimetallic 3%Pd–1.8%Zn/α-Al O reduced at different temperatures
2 3 2 3
Reduction
temperature
3
Catalyst
r × 10 *
TOF **
TOF **
TOF /TOF2
1
1
2
1
Pd
Pd–Zn
Pd
Pd–Zn
Pd
Pd–Zn
Pd
67.4
69.4
60.2
33.6
59.0
20.9
37.6
44.6
2.4
0.8
2.1
0.4
2.1
0.3
1.3
0.5
1.1
0.06
0.9
0.04
1.1
0.02
0.62
0.05
2.2
13.6
2.3
10.6
1.9
10.7
2.2
11.7
2
4
6
8
00°C
00°C
00°C
00°C
Pd–Zn
mol min–1
−1
.
*
g
H2
Cat
–
1
*
* s .
than twofold increase in the catalytic activity, as com- increase in the surface fraction occupied by palladium
–
1
pared with the sample reduced at 600°C: r increased atoms. Thus, a peak at ~1947 cm , which corresponds
1
−
1
to CO adsorbed in a bridging form, was detected in the
from 21 to 45 mol min–1
in spite of an increase
g
H2
Cat
IR-CO spectra of the Pd–Zn sample reduced at 400°C;
of the Pd–Zn nanoparticles size. The most probable
explanation for this fact consists in the zinc defi-
ciency of the surface of bimetallic particles. Accord-
ing to the study of the surface composition by XPS,
the surface concentration of Zn decreased by a factor
of 4 as the reduction temperature was increased from
this is indicative of the appearance of multiatomic Pd
n
centers in the structure of the catalyst. As the reduction
temperature was increased to 650°C, the peak intensity
of CO adsorbed in a bridging form increased. In this
case, a shift of the linearly adsorbed CO peak from 2075
–
1
to 2087 cm , which is characteristic of CO adsorption
4
00 to 800°C [26].
on Pd(III), was observed.
The decrease of the Zn surface concentration at a
The desorption of zinc from the surface at high
high temperature can be caused by both its diffusion temperatures can be an alternative mechanism of
into the bulk of bimetallic nanoparticles and evapora- decreasing the surface concentration of zinc. With the
tion from the surface of nanoparticles. Holzapfel et al. use of a set of physicochemical techniques, it was
[
42] demonstrated the possibility of Zn diffusion. Based found [20, 43] that the destruction of the Pd–Zn alloy
on the data obtained by TPD and IR-CO methods, they occurred as a result of Zn evaporation at a temperature
made a conclusion on alloy decomposition in the higher than 600°C. Thus, the observed increase in the
course of high-temperature treatment, which led to an activity of Pd–Zn/α-Al O after its high-temperature
2
3
reduction at 800°C may be related to an analogous
change in the surface structure of nanoparticles.
8
7
6
5
4
3
2
0
0
0
0
0
0
0
Comparison of the ratios between the rates of hydro-
genation at the first and second stages on the Pd and
Pd–Zn catalysts. The TOF /TOF ratio between the
Pd
Pd–Zn
1
2
rates of hydrogenation at the first and second stages of
the process is an important kinetic parameter, which
characterizes the selective hydrogenation reactions of
alkyne compounds. A decrease in the rate of reaction at
the second stage makes it possible to more effectively
control the process kinetics and to stop the reaction at
the necessary point in time for preventing the excessive
hydrogenation of an olefin intermediate. Therefore, the
TOF /TOF ratio is an important characteristic of a
10
1
2
catalyst, which should be taken into consideration in
the analysis of its catalytic properties [28].
0
200
400
600
800
According to the data of a kinetic study (Fig. 2), on
going from the first to the second stage of hydrogena-
tion on monometallic Pd/α-Al O (after the absorption
Reduction temperature, °С
Fig. 3. Dependence of the reaction rate of the liquid-phase
2
3
hydrogenation of phenylacetylene on the catalyst reduc-
of 1 equiv H ), the rate of reaction decreased insignifi-
tion temperature for Pd/α-Al O and Pd–Zn/α-Al O .
2
2
3
2 3
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INTERMETALLIC Pd –Zn NANOPARTICLES
485
1
1
cantly; this is evident from the smooth kinetic curve, a comprehensive study of the structure of Pd–Zn/α-
which does not have clearly pronounced bends in this Al O synthesized for this work [26]. For the reduced
2
3
region. The calculation of the ratio between the rates of catalysts, the binding energy of the Pd3d peak was
5
/2
hydrogenation for the monometallic Pd/α-Al O cata-
0
2
3
~335.6 eV, and it was shifted by 0.5 eV relative to Pd
lysts, which is given in Table 1, shows that the average
value of this parameter is ~2.1 ± 0.1.
standard; this fact is indicative of a decrease in elec-
tron density on the atoms of Pd and an increase in
their electron deficiency. The above allowed us to
assume that the decrease of electron density on the
atoms of Pd facilitates the desorption of styrene from
the catalyst surface into the solution and decreases the
rate of its hydrogenation [19, 24, 51].
The kinetic curves for the Pd–Zn catalysts had
another shape. All of the bimetallic catalysts exhib-
ited a clearly pronounced bend after the absorption of
~
1 equiv H , which is indicative of considerable reac-
2
tion retardation on going from the first to the second
stage. The TOF /TOF ratio for the Pd–Zn/α-Al O
1
2
2
3
Thus, based on an analysis of the experimental
catalysts was 11.8 ± 0.9; that is, the decrease of the results and published data, we can conclude that, upon
hydrogenation rate upon going from the first to the the formation of intermetallic Pd–Zn nanoparticles,
second stage of the process was pronounced to a con- the observed decrease in the hydrogenation rate at the
siderably larger degree than that for the monometal- second stage of the process is caused by the predomi-
lic Pd/α-Al O sample (Fig. 2).
nant decrease in the activity of the Pd–Zn/α-Al O
2 3
2
3
bimetallic catalyst in the hydrogenation of an olefin, as
compared with activity in the hydrogenation of the par-
ent alkyne.
An analysis of the literature showed that the pre-
dominant decrease in the rate of hydrogenation at the
second stage of the reaction and, as a consequence, the
appearance of a characteristic bend in the kinetic curves
To confirm this hypothesis, we carried out a com-
of hydrogen absorption for the Pd–Zn/α-Al O cata- parative study of the hydrogenation rate of styrene
2
3
lysts can be explained by two factors:
1) The suppression of the formation of a PdHx
and phenylacetylene on the Pd–Zn bimetallic and
Pd monometallic catalysts. The rates of hydrogena-
tion were determined based on the hydrogen absorp-
tion rates at low degrees of the initial substrates con-
version (see Experimental). The ratio between the
rates of hydrogenation of phenylacetylene and styrene
(
phase as a result of the formation of bimetallic Pd–Zn
particles. It is widely known that, under normal condi-
tions, palladium metal can dissolve a considerable
amount of hydrogen to form α- and β-PdH hydride
x
(
r
/r
) measured in two independent
styrene phenylacetylene
phases [1, 44, 45]. In the course of reaction, the
hydrogen constituent of a hydride migrates to the sur-
face of palladium and facilitates the complete hydro-
genation of an olefin intermediate adsorbed on the
surface by reacting with it [24, 46]. The use of bimetal-
lic alloy catalysts makes it possible to avoid the forma-
experiments was used as a criterion for evaluating the
effect of zinc on the rate of styrene hydrogenation. The
commercial Lindlar catalyst (5%Pd–4%PbO/CaCO ,
3
Aldrich-62145) was studied as a reference catalyst.
The results of the comparative measurement of the
tion of a hydride phase or to substantially decrease its hydrogenation rates (Table 2) show that the ratio
quantity. A similar effect was observed in bimetallic between the hydrogenation rates of phenylacetylene
systems such as Pd–Ge, Pd–Sb, Pd–Sn, Pd–Pb [47], and styrene (r
/r
) on monometallic Pd
styrene phenylacetylene
Pd–Ga [39, 48, 49], Pd–Ag [50], and Pd–Zn [19].
The suppression of Pd hydride formation as a result of
the formation of bimetallic Pd–In nanoparticles was
also found by the temperature programmed desorp-
tion of hydrogen in the Pd–In systems [37].
nanoparticles was 3.27, which is consistent with pub-
lished data, according to which an alkene is hydroge-
nated more rapidly than a corresponding alkyne [1]. If
hydrogenation was carried out on the Pd–Zn/α-Al O
2
3
sample, the value of r
/r
decreased to
styrene phenylacetylene
(
2) Another possible factor is a change in the elec- ~2.0; that is, the relative rate of styrene hydrogenation
tronic structure of Pd as a result of the formation of an decreased by a factor of 1.6. Analogous data were
alloy or Pd–Zn intermetallic compound. Thus, Wang obtained by Wowsnick et al. [54] for the Pd–Ga cata-
et al. [25] studied the electronic structure of Pd–Zn lyst. It is possible to conclude that, although the forma-
nanoparticles supported onto Al O by XPS and found tion of a Pd–Zn intermetallic compound decreases the
2
3
total catalyst activity, the activity decreased to a greater
degree at the styrene hydrogenation stage; this makes it
possible to more effectively implement the kinetic con-
trol of the process performed on the Pd–Zn catalyst.
that the Pd3d peak in the spectra of Pd–Zn/Al O
3
5/2
2
was shifted toward higher binding energies by ~0.4–
0
.5 eV, as compared with that of Pd/Al O . The
2
3
observed increase in the binding energy of the Pd3d
5
/2
peak indicates an electron density shift from the atoms
Selectivity of catalysts in the formation of a target
of Pd to the atoms of Zn [51–53]. An analogous effect olefin. The dependence of selectivity to styrene forma-
was observed in a study of the Pd/ZnO catalyst [24]. tion on the conversion of initial phenylacetylene was
With the use of XPS, it was established that, upon the studied for the Pd–Zn/α-Al O catalysts reduced at
2
3
formation of Pd–Zn alloy, the Pd3d line shifted 200, 400, 600, and 800°C. The commercial Lindlar
5/2
from 355.2 to 355.8 eV. A similar result was obtained in catalyst was used as a reference sample (Fig. 4).
KINETICS AND CATALYSIS Vol. 58 No. 4 2017

4
86
MASHKOVSKY et al.
Table 2. Kinetic characteristics of the liquid-phase reactions of phenylacetylene and styrene hydrogenation in the presence
of the monometallic 1%Pd/α-Al O * and bimetallic 3%Pd–1.8%Zn/α-Al O * catalysts and the Lindlar catalyst
2
3
2
3
3
Catalyst
Substrate
rhydr × 10 ** r
/rphenylacetylene
TOF ***
TOF ***
styrene
1
2
Phenylacetylene
Styrene
Phenylacetylene
Styrene
Phenylacetylene
Styrene
37.6
123.0
44.6
90.4
27.6
1.3
–
0.5
–
0.4
–
0.62
4.4
0.05
1.1
0.03
0.17
Pd
3.2
Pd–Zn
Lindlar
2.0
0.4
11.9
A dash denotes that the stage of phenylacetylene hydrogenation was absent with the use of styrene.
*
The catalysts were reduced at 800°C.
−1
*
* mol min–1
** s .
g
.
H2
Cat
–1
*
At conversions of no higher than 50%, all catalysts contribution of the direct hydrogenation reaction of
demonstrate the target selectivity around 93–96%. In the adsorbed olefin intermediate to the course of the
the region of high phenylacetylene conversions, this reaction is small and the second stage of hydrogena-
characteristic gradually decreased for all of the sam- tion predominantly proceeds through the readsorption
ples. As the conversion of phenylacetylene increased of the resulting olefin [55].
to ≥90%, selectivity decreased to 80–85%.
With increasing the conversion of phenylacetylene,
the concentration of styrene in the reaction solution
increased; as styrene accumulated, it began to displace
the initial alkyne from the catalyst surface because of
the alkyne/alkene competitive adsorption (a thermo-
dynamic factor). As a result of an increase of read-
sorbed styrene amount on the catalyst surface, the rate
of its hydrogenation increased to cause the formation
of ethylbenzene and a decrease in the selectivity.
According to the classical two-stage mechanism of
hydrogenation adapted to liquid-phase processes [55,
5
6], the experimental data can be explained as follows:
In the region of low phenylacetylene conversions, the
main reason for a decrease in selectivity is the direct
hydrogenation of an adsorbed olefin intermediate (a
kinetic factor). This is due to the fact that the concen-
tration of formed styrene in the solution is small and
the process of its readsorption can be neglected. In this
case, the observed high selectivity indicates that the
The comparison of the catalytic properties of the
Pd–Zn/α-Al O samples reduced at temperatures of
2
3
2
00, 400, 600, and 800°C showed that the catalyst
reduced at 200°C exhibited the lowest selectivity in the
phenylacetylene hydrogenation over the entire range
of conversions. At a ~90% conversion of phenylacety-
Sstyrene
1.00
lene, the value of S was no higher than 85–86%. The
=
catalysts reduced at 400–800°C were noticeably
0.95
more selective (S ~ 91–93%) at the same values of
=
phenylacetylene conversion. It should also be noted
that the values of S for these samples were the same
=
0.90
as those for the commercial Lindlar catalyst (Fig. 4).
2
4
6
8
00°C
00°C
00°C
00°C
The low selectivity of the sample reduced at 200°C
can be explained by the fact that this temperature is
insufficient for the completion of the Pd–Zn interme-
tallide nanoparticles formation. According to the XRD
analysis data, after the reduction of Pd–Zn/α-Al O at
0
.85
.80
Lindlar
2
3
0
2
00°C, the XRD pattern of the catalyst exhibited a
0
.4
0.5
0.6
0.7
0.8
0.9
1.0
number of diffraction peaks that indicated the forma-
tion of both a solid solution of Pd with Zn and a Pd–Zn
intermetallic compound. At the same time, a Bragg
peak at 2θ ~41.5°, which is characteristic of a palla-
dium metal phase [26], was retained in the XRD pat-
tern. An increase in the reduction temperature to 400–
Хphenylacetylene
Fig. 4. Dependence of the selectivity of styrene formation
) on the conversion of phenylacetylene in the liq-
(S
styrene
uid-phase phenylacetylene hydrogenation on the monome-
tallic Pd/α-Al O (800°C) and bimetallic Pd–Zn/α-Al O
2 3
2
3
8
00°C led to the transformation of Pd-containing
catalysts reduced at different temperatures and on the
Lindlar catalyst.
nanoparticles into the Pd–Zn intermetallic nanopar-
KINETICS AND CATALYSIS
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No. 4
2017

INTERMETALLIC Pd –Zn NANOPARTICLES
487
1
1
Table 3. Kinetic characteristics of the liquid-phase reactions of hydrogenation of different substrates in the presence of the
monometallic 1%Pd/α-Al O and bimetallic 3%Pd–1.8%Zn/α-Al O catalysts reduced at 600°C
2
3
2
3
3
3
Substrate
Catalyst
r × 10 *
r × 10 *
TOF **
TOF **
r1/r2
17.01
32.69
1
2
1
2
Pd
Pd–Zn
53.0
3.12
0.43
1.88
0.16
0.11
13.9
0.005
Pd
Pd–Zn
Pd
80.7
93.0
18.3
0.98
0.82
3.68
5.72
2.20
0.65
0.07
0.02
0.13
82.56
113.87
4.98
H C
3
CH3
Pd–Zn
3
8.8
1.35
0.46
0.02
28.70
CH3
CH3
Pd
Pd–Zn
3.1
0.85
0.14
0.11
0.02
0.03
3.68
1.8
0.002
12.19
–1
−1
*
molH min
* s .
g
.
2
Cat
–
1
*
ticles, which facilitated an increase in the selectivity of the value of TOF for Pd/α-Al O was higher by a factor
1
2
3
the catalyst. Chin et al. [57] obtained an analogous of 2.5 than that for the bimetallic sample. The experi-
result. They found that the Pd/ZnO catalyst reduced mental data are consistent with the results of pheny-
at 350°C was more selective than the sample activated lacetylene hydrogenation (see the previous section),
at 125°C; this fact can be explained by the presence of and they are also indicative of the Pd–Zn/α-Al O cat-
2
3
a large amount of palladium metal in the structure of
the latter.
alyst lower activity, as compared with that of the mono-
metallic samples.
It is likely that a relatively rapid decrease in selec-
tivity in the region of high phenylacetylene conver-
sions on both the Pd–Zn catalysts and the Lindlar cat-
alyst was related to the special features of the triple
bond geometry in the molecules of terminal alkynes.
In a number of publications [27, 58, 59] it was shown
that terminal alkynes possess higher reactivity than that
of internal alkynes. This can lead to the complete
hydrogenation of an intermediate olefin to an alkane
even on the Lindlar catalyst [58]. A similar result was
also obtained earlier in the hydrogenation of pheny-
lacetylene on the samples containing supported Pd–In
particles [38].
An analysis of the shapes of the kinetic curves of
diphenylacetylene and 4-octyne hydrogenation on
both the mono- and bimetallic catalysts showed that
for both substrates, a sharp bend was observed after
the absorption of 1 equiv H , which indicated a
2
decrease in the rate of hydrogenation on going from
the first to the second stage (Figs. 5a, 5c). Note that
the effect of the preferred retardation of the second
stage of reaction for diphenylacetylene and 4-octyne
was pronounced to a considerably larger degree than
that for other substrates: it will suffice to compare
data in Fig. 5 with the kinetic curves obtained on the
hydrogenation of phenylacetylene (Fig. 2), 1-phenyl-
1
-butyne, and 1-phenyl-1-propyne (Figs. 6a, 6c).
It is likely that the appearance of a bend is related
Symmetric Alkyne Hydrogenation
to the geometry of a substrate molecule and the spe-
cific character of its adsorption on the catalyst surface.
For example, on the hydrogenation of phenylacetylene
and other asymmetrical alkynes (see below), a bend in
The Pd and Pd–Zn catalysts reduced at 600°C
were chosen for studying the catalytic properties in the
hydrogenation of different substrates.
A comparison of the kinetic curves of hydrogen the kinetic curve is pronounced to a much smaller
absorption in the course of the hydrogenation reac- degree than that for diphenylacetylene and 4-octyne—
tions of diphenylacetylene (DPA) and 4-octyne on the compounds with symmetrical structures. A similar
Pd/α-Al O and Pd–Zn/α-Al O catalysts and the val- result was obtained by Spee et al. [28], who observed a
2
3
2
3
ues of TOF calculated on their basis (see Figs. 5a, 5c considerably larger retardation of the second stage of
1
the process in the hydrogenation of internal alkynes
with symmetrical structures.
and Table 3) allowed us to conclude that the monome-
tallic Pd catalyst is substantially more active than
Pd‒Zn/α-Al O . In the hydrogenation of dipheny-
2
3
A comparative analysis of the shapes of kinetic
lacetylene, the value of TOF calculated for Pd/α-Al O
curves for Pd/α-Al O and Pd–Zn/α-Al O made it
1
2
3
2
3
2
3
was higher by a factor of 11 than this value for possible to conclude that the effect of the preferred
Pd‒Zn/α-Al O . In the hydrogenation of 4-octyne, decrease of the second reaction stage rate was pro-
2
3
KINETICS AND CATALYSIS Vol. 58 No. 4 2017

4
88
MASHKOVSKY et al.
(а)
(b)
AH2, (mol H )/(mol diphenylacetylene)
2
S=
2
1
1
1
1
1
.0
.8
.6
.4
.2
.0
1.00
0
.95
.90
0.85
.80
.75
.70
0
0.8
0.6
0.4
0.2
0
Pd
Pd–Zn
Pd
Pd–Zn
0
0
0
20
40
60
80
100
0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Time, min
XDPA
(c)
(d)
AH2, (mol H )/(mol octyne)
2
S
=
2
1
1
1
.0
.8
.6
.4
.2
1.00
.95
.90
0.85
.80
.75
.70
0
0
1
1
.0
.8
.6
.4
.2
0
0
0
0
0
Pd
Pd
Pd–Zn
0
Pd–Zn
0
0
10
20
30
40
50
60
0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Time, min
Xoctyne
Fig. 5. Dependences of the amount of absorbed hydrogen AH2 on the reaction time (a, c) and of selectivity to olefin formation
on alkyne conversion (b, d) in the hydrogenation of (a, b) diphenylacetylene (DPA) and (c, d) 4-octyne on the Pd/α-Al O and
2
3
Pd–Zn/α-Al O catalysts reduced at 600°C.
2
3
nounced to a much larger degree for Pd–Zn/α-Al O
upon the formation of intermetallic Pd–Zn particles,
2
3
than for Pd/α-Al O . This was confirmed by the data as confirmed by [19]. In the case of 4-octyne, the
2
3
influence of Pd–Zn intermetallic compound forma-
tion on the process selectivity was expressed to a lesser
degree, and the selectivity of the Pd and Pd–Zn cata-
lysts was almost identical in the entire range of conver-
sions (Fig. 5d).
of the quantitative analysis of the rates: the ratios of
the rates of the first and second stages of dipheny-
lacetylene hydrogenation (TOF /TOF ) were ~17 and
1
2
~
33 for the Pd and Pd–Zn catalysts, respectively (see
Table 3). In the hydrogenation of 4-octyne, the
TOF /TOF ratios were 83 and 114 for the Pd and
1
2
Pd–Zn samples, respectively.
Asymmetric Alkyne Hydrogenation
An analysis of “Selectivity to alkene formation–
Figures 6a and 6c show the dependence of the
DPA conversion” plot (Fig. 5b) showed that the selec- hydrogen absorption on the reaction time in the hydro-
tivity of the samples approached 100% in the region of genation of asymmetric alkynes (1-phenyl-1-butyne
low diphenylacetylene conversions. However, at high and 1-phenyl-1-propyne) on the Pd and Pd–Zn cata-
conversions, this characteristic was noticeably higher lysts. The formation of Pd–Zn intermetallic com-
for the Pd–Zn catalyst than for Pd/α-Al O . This pounds leads to an insignificant decrease in the cata-
2
3
experimental result is consistent with data on the lytic activity, as compared with that of monometallic
hydrogenation of phenylacetylene, which are also Pd. The values of TOF obtained in the hydrogenation
indicative of an increase in the reaction selectivity of 1-phenyl-1-butyne on the Pd and Pd–Zn samples
1
KINETICS AND CATALYSIS
Vol. 58
No. 4
2017

INTERMETALLIC Pd –Zn NANOPARTICLES
489
1
1
(а)
(b)
AH2, (mol H )/(mol 1-phenyl-1-butyne)
2
S
=
2
1
1
1
.0
.8
.6
.4
.2
1.00
.95
.90
0.85
.80
.75
.70
Pd
Pd–Zn
0
0
1
1
.0
.8
.6
.4
.2
0
0
0
0
0
Pd
Pd–Zn
0
0
0
50
100
150
200
0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Time, min
X1-phenyl-1-butyne
(c)
(d)
AH2
, (mol H2)/(mol 1-phenyl-1-propyne)
S=
1.00
2
1
1
1
.0
.8
.6
.4
.2
0
.95
.90
0.85
.80
.75
.70
0
1
1
.0
.8
.6
.4
.2
0
0
0
0
0
Pd
Pd–Zn
Pd
Pd–Zn
0
0
0
200
400
600
800
0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Time, min
X1-phenyl-1-propyne
Fig. 6. Dependences of the amount of absorbed hydrogen AH2 on the reaction time (a, c) and of selectivity for olefin formation
on alkyne conversion (b, d) in the hydrogenation of (a, b) 1-phenyl-1-butyne and (c, d) 1-phenyl-1-propyne on the Pd/α-Al O
2
3
and Pd–Zn/α-Al O catalysts reduced at 600°C.
2
3
–1
were 0.65 and 0.46 s , respectively (Table 3). The more than 5. In the hydrogenation of 1-phenyl-1-pro-
bimetallic Pd–Zn catalyst was also less active than the pyne, the value of TOF /TOF for Pd–Zn/α-Al was
monometallic one in the hydrogenation of 1-phenyl- also higher by a factor of 3 than that for Pd/α-Al O .
O
2 3
1
2
2
3
1
-propyne. The value of TOF (0.02) for this catalyst
1
An analysis of the dependence of the selectivity of
was lower than that for Pd (0.11) by a factor of 5.
the Pd/α-Al O and Pd–Zn/α-Al O catalysts in the
2
3
2
3
formation of alkene compounds on the conversion of
initial alkynes showed that the catalyst containing
Pd–Zn intermetallide nanoparticles as an active com-
ponent exhibited much higher selectivity than that of
In contrast to the hydrogenation of symmetrical
compounds, a bend in the kinetic curves for asym-
metrical substrates in the region of an equimolar H
2
quantity absorption was not so clearly pronounced,
although a tendency toward reaction retardation on
going to the second stage was also observed (Table 3,
Figs. 6a, 6c). As in the hydrogenation reactions of
other substrates, the rate ratio TOF /TOF increased
monometallic Pd/α-Al O in the hydrogenation of
2
3
both 1-phenyl-1-butyne (Fig. 6c) and 1-phenyl-1-
propyne (Fig. 6d). These results are consistent with data
obtained in the hydrogenation of the other substrates:
phenylacetylene, diphenylacetylene, and 4-octyne.
1
2
on going from Pd/α-Al O to Pd–Zn/α-Al O . Thus,
2
3
2
3
in the hydrogenation of 1-phenyl-1-butyne, the value
Note that the high values of S were obtained on
=
of TOF /TOF for Pd–Zn/α-Al O was higher than the hydrogenation of asymmetrical alkynes on Pd–
1
2
2
3
this ratio for monometallic Pd/α-Al O by a factor of Zn/α-Al O in the entire range of the initial alkyne
2
3
2
3
KINETICS AND CATALYSIS Vol. 58 No. 4 2017

4
90
MASHKOVSKY et al.
conversions. This is related to the fact that on the
hydrogenation asymmetrical alkynes noticeable
amounts of complete hydrogenation products were
formed already at the very beginning of the process at
a low conversion. The observed regularity indicates
that the contribution of the direct hydrogenation of
adsorbed olefin intermediates on the hydrogenation of
asymmetrical alkynes plays a noticeably greater role
than that in the hydrogenation of structurally symmet-
rical molecules.
ACKNOWLEDGMENTS
This work was supported by the Russian Science
Foundation (grant no. 16-13-10530).
REFERENCES
. Borodzinski, A. and Bond, G.C., Catal. Rev., 2006,
vol. 48, p. 91.
1
2. Ananikov, V.P., Khemchyan, L.L., Ivanova, Yu.V.,
Bukhtiyarov, V.I., Sorokin, A.M., Prosvirin, I.P.,
Vatsadze, S.Z., Medved’ko, A.V., Nuriev, V.N.,
Dil’man, A.D., Levin, V.V., Koptyug, I.V., Kovtu-
nov, K.V., Zhivonitko, V.V., Likholobov, V.A., et al.,
Russ. Chem. Rev., 2014, vol. 83, p. 885.
. Nikolaev, S.A., Zanaveskin, L.N., Smirnov, V.V.,
Aver’yanov, V.A., and Zanaveskin, K.L., Russ. Chem.
Rev., 2009, vol. 78, p. 231.
4. Bonrath, W., Medlock, J., Schütz, J., Wüstenberg, B.,
and Netscher, T., Hydrogenation: Overview, Karamé, I.,
Ed., InTech, 2012. http://www.intechopen.com/
books/hydrogenation/hydrogenation-in-the-vitamins-
and-fine-chemicals-industry-an-overview.
CONCLUSIONS
3
In general, the results of a comparative study of the
characteristics of the monometallic 1%Pd/α-Al O
2
3
and bimetallic Pd–Zn/α-Al O catalysts in the selec-
2
3
tive liquid-phase hydrogenation of structurally differ-
ent alkynes allowed us to draw the following basic con-
clusions: We established that the catalytic activity of
the bimetallic catalyst in acetylene bond hydrogena-
tion was lower by a factor of 3–10 than the activity of
its monometallic analog in the hydrogenation of all of
the substrates. As the catalyst reduction temperature
was increased from 200 to 600°C, difference in the
activities increased. According to the data of an earlier
physicochemical study, this is related to the formation
and agglomeration of Pd –Zn intermetallic nanopar-
5
6
. Ichimura, K., Chem. Rev., 2000, vol. 100, p. 1847.
. Halim, M., Samuel, I.D.W., Pillow, J.N.G., Monk-
man, A.P., and Burn, P.L., Synth. Met., 1999, vol. 102,
p. 1571.
7. Furukawa, Sh., Yokoyama, A., and Komatsu, T., ACS
Catal., 2014, vol. 4, p. 3581.
8. Blaser, H.-U., Schnyder, A., Steiner, H., Rossler, F.,
and Baumeister, P., in Handbook of Heterogeneous
Catalysis, Ertl, G., Knözinger, H., Schüth, F., and
Weitkamp, J., Eds., Weinheim, Germany: Wiley–
VCH, 2008, vol. 8, p. 3298.
1
1
ticles in the Pd–Zn/α-Al O catalyst and the disap-
2
3
pearance of monometallic Pd ones. The favorable
process kinetics is an advantage of the catalyst con-
taining Pd–Zn intermetallide nanoparticles as active
sites. Thus, for all of the substrates investigated in this
work, the rate of hydrogenation of an initial acetylene
compound on Pd–Zn/α-Al O was higher than the
9
. Ananikov, V.P., Galkin, K.I., Egorov, M.P.,
Sakharov, A.M., Zlotin, S.G., Redina, E.A.,
Isaeva, V.I., Kustov, L.M., Gening, M.L., and Nifan-
tiev, N.E., Mendeleev Commun., 2016, vol. 26, p. 365.
1
0. Ananikov, V.P., Khokhlova, E.A., Egorov, M.P.,
2
3
Sakharov, A.M., Zlotin, S.G., Kucherov, A.V.,
Kustov, L.M., Gening, M.L., and Nifantiev, N.E.,
Mendeleev Commun., 2015, vol. 25, p. 75.
rate of the undesirable hydrogenation of the target
alkene by a factor of 10–100. This fact makes it possi-
ble to perform the effective kinetic control of the pro-
cess and to stop the reaction upon the completion of the
1
1. Karunananda, M.K. and Mankad, N.P., J. Am. Chem.
Soc., 2015, vol. 137, p. 14598.
first stage. The Pd–Zn/α-Al O catalyst possesses
2
3
12. Pei, G.X., Yan, LiuX., Wang, A., Lee, A.F.,
Isaacs, M.A., Li, L., Pan, X., Yang, X., Wang, X.,
Tai, Z., Wilson, K., and Zhang, T., ACS Catal., 2015,
vol. 5, p. 3717.
higher selectivity than that of its monometallic analog.
A detailed analysis of the kinetic characteristics
obtained and the available published data makes it pos-
sible to conclude that different catalytic properties of
Pd–Zn/α-Al O and Pd/α-Al O are related to the
1
3. Tan, L., Wu, X., Chen, D., Liu, H., Menga, X., and
Tang, F., J. Mater. Chem. A, 2013, vol. 1, p. 10382.
2
3
2
3
1
4. McCue, A.J., Gibson, A., and Anderson, J.A., Chem.
lower adsorption energies of the initial alkyne and an
Eng. J., 2016, vol. 285, p. 384.
olefin intermediate, which is formed upon its hydroge-
1
5. Chinayon, S., Mekasuwandumrong, O., Praserthdam, P.,
nation, on the Pd –Zn intermetallic nanoparticles. On
1
1
and Panpranot, J., Catal. Commun., 2008, vol. 9, p. 2297.
the one side, this leads to a decrease in the hydrogena- 16. Mashkovskii, I.S., Tkachenko, O.P., Baeva, G.N., and
tion rate on the Pd–Zn/α-Al O catalyst, as compared
Stakheev, A.Yu., Kinet. Catal., 2009, vol. 50, no. 50,
2
3
p. 768.
with that on Pd/α-Al O . However, on the other hand,
2
3
1
7. Zhou, H., Yang, X., Wang, A., Miao, Sh., Liu, X.,
Pan, X., Su, Y., Li, L., Tan, Y., and Zhang, T., Chin. J.
Catal., 2016, vol. 37, p. 692.
the lowered adsorption energy facilitates the desorp-
tion of the olefin intermediate, which decreases the
probability of its further hydrogenation. This predom-
inantly decreases the rate of the complete hydrogena-
tion and increases catalyst selectivity in the hydroge-
nation of structurally different substrates.
1
8. Mashkovsky, I.S., Baeva, G.N., Stakheev, A.Yu., Var-
gaftik, M.N., Kozitsyna, N.Yu., and Moiseev, I.I.,
Mendeleev Commun., 2014, vol. 24, p. 355.
19. Föttinger, K., Catalysis, 2013, vol. 25, p. 77.
KINETICS AND CATALYSIS
Vol. 58
No. 4
2017

INTERMETALLIC Pd –Zn NANOPARTICLES
491
1
1
2
0. Armbrüster, M., Behrens, M., Föttinger, K., Fried-
Yakushev, I.A., Vargaftik, M.N., and Stakheev, A.Yu.,
rich, M., Gaudry, É., Matam, S.K., and Sharma, H.R.,
Kinet. Catal., 2016, vol. 57, no. 6, p. 859.
Catal. Rev. Sci. Eng., 2013, vol. 55, p. 289.
40. Osswald, J., Giedigkeit, R., Jentoft, R.E., Arm-
brüster, M., Girgsdies, F., Kovnir, K., Ressler, T.,
Grin, Yu., and Schlögl, R., J. Catal., 2008, vol. 258,
p. 210.
21. Studt, F., Abild-Pedersen, F., Bligaard, T., Sørensen, R.Z.,
Christensen, C.H., and Nørskov, J.K., Science, 2008,
vol. 320, p. 1320.
2
2. Furukawa, S. and Komatsu, T., ACS Catal., 2017, 41. Armbrüster, M., Kovnir, K., Behrens, M., Teschner, D.,
vol. 7, p. 735.
Grin, Yu., and Schlögl, R., J. Am. Chem. Soc., 2010,
vol. 132, p. 14745.
2. Holzapfel, H.H., Wolfbeisser, A., Rameshan, C., Wei-
lach, C., and Rupprechter, G., Top. Catal., 2014,
vol. 57, p. 1218.
3. Gabasch, H., Knop-Gericke, A., Schlögl, R., Penner, S.,
Jenewein, B., and Hayek, K., and Klötzer, B., J. Phys.
Chem. B, 2006, vol. 110, p. 11391.
2
3. Zhou, H., Yang, X., Li, L., Liu, X., Huang, Y., Pan, X.,
Wang, A., Li, J., and Zhang, T., ACS Catal., 2016,
vol. 6, p. 1054.
4
2
2
2
4. Yoshida, H., Zama, T., Fujita, S., Panpranot, J., and
4
Arai, M., RSC Adv., 2014, vol. 4, p. 24922.
5. Wang, Z., Yang, L., Zhang, R., Li, L., Cheng, Z., and
Zhou, Z., Catal. Today, 2016, vol. 264, p. 37.
4
4
4. Palczewska, W., Adv. Catal., 1975, vol. 24, p. 245.
5. García-Mota, M., Gómez-Díaz, J., Novell-Leruth, G.,
Vargas-Fuentes, C., Bellarosa, L., and Pérez-Ramírez, J.,
and López, N., Theor. Chem. Acc., 2011, vol. 128, p. 663.
6. Caga, I.T., Shutt, E., and Winterbottom, J.M.,
J. Catal., 1976, vol. 44, p. 271.
6. Mashkovsky, I.S., Markov, P.V., Bragina, G.O.,
Baeva, G.N., Bukhtiyarov, A.V., Prosvirin, I.P., Bukh-
tiyarov, V.I., and Stakheev, A.Yu., Kinet. Catal., 2017,
vol. 58, p. 471.
4
2
7. Markov, P.V., Bragina, G.O., Baeva, G.N.,
Tkachenko, O.P., Mashkovskii, I.S., Yakushev, I.A.,
Kozytsyna, N.Yu., Vargaftik, M.N., and Sta-
kheev, A.Yu., Kinet. Catal., 2015, vol. 56, p. 591.
4
7. Aduriz, H.R., Bodnariuk, P., Coq, B., and Figueras, F.,
J. Catal., 1991, vol. 129, p. 47.
4
8. Armbrüster, M., Behrens, M., Cinquini, F., Föt-
tinger, K., Grin, Yu., Haghofer, A., Klötzer, B.,
Knop-Gericke, A., Lorenz, H., Ota, A., Penner, S.,
Prinz, J., Rameshan, C., Révay, Z., Rosenthal, D.,
et al., ChemCatChem, 2012, vol. 4, p. 1048.
2
8. Spee, J., Boersma, J., Meijer, M.D., Slagt, M.Q.,
van Koten, G., and Geus, J.W., J. Org. Chem., 2001,
vol. 66, p. 1647.
2
9. Mashkovsky, I.S., Markov, P.V., Bragina, G.O.,
Tkachenko, O.P., Yakushev, I.A., Kozitsyna, N.Yu.,
Vargaftik, M.N., and Stakheev, A.Yu., Russ. Chem.
Bull., 2016, vol. 65, no. 2, p. 425.
4
9. Ota, A., Armbrüster, M., Behrens, M., Rosenthal, D.,
Friedrich, M., Kasatkin, I., Girgsdies, F., Zhang, W.,
Wagner, R., and Schlögl, R., J. Phys. Chem. C, 2010,
vol. 115, p. 1368.
0. Yang, B., Burch, R., Hardacre, C., Headdock, G., and
Hu, P., J. Catal., 2013, vol. 305, p. 264.
1. Tew, M.W., Emerich, H., and van Bokhoven, J.A.,
J. Phys. Chem. C, 2011, vol. 115, p. 8457.
2. Rodriguez, J., J. Phys Chem., 1994, vol. 98, p. 5758.
3. Araña, J., Homs, N., Sales, J., Fierro, J.L.G., and
Ramirez de la Piscina, P., Catal. Lett., 2001, vol. 72,
p. 183.
4. Wowsnick, G., Teschner, D., Armbrüster, M., Kasat-
kin, I., Girgsdies, F., Grin, Yu., Schlögl, R., and Beh-
rens, M., J. Catal., 2014, vol. 309, p. 221.
5. Bond, G.C., Metal-Catalysed Reactions of Hydrocar-
bons, New York: Springer Science + Business Media,
2005.
30. Domínguez-Domínguez, S., Berenguer-Murcia, A.,
Cazorla-Amorós, D., and Linares-Solano, A., J. Catal.,
5
2006, vol. 243, p. 74.
31. Karakhanov, E.A., Aksenov, I.A., Kardashev, S.V.,
5
Maksimov, A.L., Putilin, F.N., Shatokhin, A.N., and
Savilov, S.V., Appl. Catal., A, 2013, vols. 464–465,
p. 253.
5
5
3
3
3
3
3
2. Marin-Astorga, N., Alvez-Manoli, G., and Reyes, P.,
J. Mol. Catal. A: Chem., 2005, vol. 226, p. 81.
3. Jung, A., Jess, A., Schubert, T., and Schütz, W., Appl.
5
Catal., A, 2009, vol. 362, p. 95.
4. Segura, Y., López, N., and Pérez-Ramírez, J., J. Catal.,
2007, vol. 247, p. 383.
5
5. Teschner, D., Borsodi, J., and Wootsch, A., Science,
2008, vol. 320, p. 86.
6. Vilé, G., Almora-Barrios, N., Mitchell, Sh., Lóopez, N., 56. Markov, P.V., Bragina, G.O., Rassolov, A.V., Mash-
and Pérez-Ramírez, J., Chem. Eur. J., 2014, vol. 20,
p. 5926.
kovsky, I.S., Baeva, G.N., Tkachenko, O.P., Yaku-
shev, I.A., Vargaftik, M.N., and Stakheev, A.Yu.,
Mendeleev Commun., 2016, vol. 26, p. 494.
37. Markov, P.V., Bragina, G.O., Baeva, G.N.,
5
7. Chin, Y.H., Dagle, R., Hu, J.L., Dohnalkova, A.C.,
Tkachenko, O.P., Mashkovskii, I.S., Yakushev, I.A.,
and Wang, Y., Catal. Today, 2002, vol. 77, p. 79.
Vargaftik, M.N., and Stakheev, A.Yu., Kinet. Catal.,
2016, vol. 57, no. 5, p. 617.
58. Mitsudome, T., Takahashi, Y., Ichikawa, S., Mizugaki, T.,
Jitsukawa, K., and Kaneda, K., Angew. Chem., Int. Ed.
Engl., 2013, vol. 52, p. 1481.
38. Markov, P.V., Bragina, G.O., Baeva, G.N., Mash-
kovskii, I.S., Rassolov, A.V., Yakushev, I.A., Varga-
ftik, M.N., and Stakheev, A.Yu., Kinet. Catal., 2016, 59. Niu, M., Wang, Y., Li, W., Jiang, J., and Jin, Z., Catal.
vol. 57, no. 5, p. 625.
Commun., 2013, vol. 38, p. 77.
Translated by V. Makhlyarchuk
3
9. Rassolov, A.V., Markov, P.V., Bragina, G.O.,
Baeva, G.N., Krivoruchenko, D.S., Mashkovskii, I.S.,
KINETICS AND CATALYSIS Vol. 58 No. 4 2017