Mesoporous organic Pd-containing catalysts for the selective hydrogenation of conjugated hydrocarbons

Article abstract of DOI:10.1007/s11172-014-0657-9

Palladium catalysts supported on ordered organic mesoporous polymers were synthesized. The catalysts are characterized by the narrow size distribution of palladium nanoparticles with an average particle size of 2.2-5.2 nm. They demonstrate high catalytic activity and selectivity in phenylacetylene hydrogenation (896-2590 min^-1, selectivity 89-98%). High activity and selectivity for alkenes are observed in the hydrogenation of conjugated dienes (for isoprene, TOF = 1850-5000 min^-1, selectivity 99%; for 2,5-dimethyl-2,4-hexadiene, TOF = = 1294-2400 min^-1, selectivity 100%; for 1,4-diphenyl-1,3-butadiene, TOF = 14-22 min^-1, selectivity 7-16%). A dependence of the selectivity on the nature of the support and substrate was found for the hydrogenation of 1,4-diphenyl-1,3-butadiene.

Full text of DOI:10.1007/s11172-014-0657-9

1
710
Russian Chemical Bulletin, International Edition, Vol. 63, No. 8, pp. 1710—1716, August, 2014
Mesoporous organic Pdꢀcontaining catalysts for the selective
hydrogenation of conjugated hydrocarbons
E. A. Karakhanov,a A. L. Maksimov,a,b I. A. Aksenov, V. S. Kuznetsov, T. Yu. Filippova,
a
a
a
a
a
S. V. Kardashev, and D. S. Volkov
aChemical Department, M. V. Lomonosov Moscow State University,
Build. 3, 1 Leninskie Gory, 119991 Moscow, Russian Federation.
Fax: +7 (495) 932 8846. Eꢀmail: kar@petrol.chem.msu.ru
b
A. V. Topchiev Institute of Petrochemical Synthesis,
2
9 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (495) 633 8520
Palladium catalysts supported on ordered organic mesoporous polymers were synthesized.
The catalysts are characterized by the narrow size distribution of palladium nanoparticles with
an average particle size of 2.2—5.2 nm. They demonstrate high catalytic activity and selectivity
in phenylacetylene hydrogenation (896—2590 min– , selectivity 89—98%). High activity and
selectivity for alkenes are observed in the hydrogenation of conjugated dienes (for isoprene,
1
–
1
TOF = 1850—5000 min , selectivity 99%; for 2,5ꢀdimethylꢀ2,4ꢀhexadiene, TOF =
1294—2400 min–1, selectivity 100%; for 1,4ꢀdiphenylꢀ1,3ꢀbutadiene, TOF = 14—22 min–1
=
,
selectivity 7—16%). A dependence of the selectivity on the nature of the support and substrate
was found for the hydrogenation of 1,4ꢀdiphenylꢀ1,3ꢀbutadiene.
Key words: organic mesoporous supports, palladium nanoparticles, selective hydrogenaꢀ
tion, phenylacetylene, conjugated dienes.
Development of catalysts for selective hydrogenation
trices are used, for example, for the stabilization of nanoꢀ
particles.
3
is one of the most important problems of petrochemical
synthesis. Olefins obtained by pyrolysis or dehydrogenaꢀ
tion contain acetylene and diene hydrocarbons that poiꢀ
son the catalysts in the course of subsequent olefin polyꢀ
merization. Therefore, one of the main stages of olefin
preparation to polymerization is the selective hydrogenaꢀ
tion of acetylene and diene hydrocarbons to alkenes. When
styrene is produced by catalytic dehydrogenation, phenylꢀ
acetylene is formed, whose content, according to GOST
Methods for synthesis of mesoporous organic supports
4
—7
are being actively developed recently.
The obtained
materials seem to be very promising since they can easily be
synthesized and the supports have regular structure, large
surface area, variable pore dimensions, and surfaces amenꢀ
able to chemical modification. This provides prerequisites
for the synthesis of catalysts with a substrate selectivity.
The purpose of this work is to synthesize a series of
Pdꢀcontaining catalysts using an organic mesoporous polyꢀ
mer as a support and to test the obtained catalysts in the
hydrogenation of various unsaturated compounds.
1
0003ꢀ90, should be decreased to 0.01% (for styrene of the
superior quality). According to GOST 25043ꢀ87, the volꢀ
ume fraction of hydrocarbons (propadiene and butadiene)
in propylene of the superior quality should be 0.01%.
Since selective hydrogenation is structureꢀsensitive
process in which activity and selectivity of the catalyst
depend on the particle size of the active component, it is
necessary to develop methods for the production of cataꢀ
Experimental
8
Supports were synthesized as described earlier using a proꢀ
cedure of solvent evaporationꢀinduced selfꢀassembly (EISA). The
synthesis conditions are presented in Table 1. The role of
the precursor was played by the lowꢀmolecularꢀweight soluꢀ
ble phenol resin (resol UPF) obtained by the polymerization
of urea, phenol, and formaldehyde (Scheme 1). Triblock coꢀ
polymer Pluronic F127 (M = 12600, PEO —PPO —PEO106,
1
lysts with the rigidly controlled particle sizes. Modern
methods for direct supporting of metals, for example, laser
ablation, can form catalysts with a narrow size distribuꢀ
2
tion of metallic particles. However, the main problem
w
106
70
appeared when using metal nanoparticles in catalytic proꢀ
cesses is their aggregation leading to a decrease in the
catalytic activity during operation. Such supports as meꢀ
soporous aluminosilicates or crosslinked dendrimeric maꢀ
Aldrich) was used as
a template. The molar fraction
urea : phenol : formaldehyde for all samples was 1 : 1 : 2.5.
Phenol (11.0 g) was placed in a glass reactor equipped with a
magnetic stirrer and a reflux condenser and was melted at 45 С.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1710—1716, August, 2014.
066ꢀ5285/14/6308ꢀ1710 © 2014 Springer Science+Business Media, Inc.
1

Mesoporous catalysts for hydrogenation
Russ.Chem.Bull., Int.Ed., Vol. 63, No. 8, August, 2014
1711
Table 1. Synthesis conditions for the mesoporous polymer
dish, where ethanol evaporated for 5—8 h at ~20 C, after which
supports
the sample was placed in drying box and heated for 24 h at
1
00 С. The product, being a semitransparent orange film, was
powdered. The template in samples 1—3 was removed by anꢀ
nealing in a tubular furnace under evacuation, and that in
sample 4 was removed by annealing the sample in a muffle furꢀ
nace without evacuation. In all cases, the template was removed
at a certain temperature in an inert atmosphere of nitrogen for
Cataꢀ Phenol : template
lyst
Annealing
temperature/С
Annealing
time/h
1
2
3
1 : 0.01
1 : 0.01
1 : 0.01
380
380
380
15
10
10
15
15
–
1
a certain time (see Table 1). The heating rate was 1 С min
,
and the flow rate was 90 mL min– . The obtained product was
1
4
50
4*
1 : 0.012
380
a black powder.
Supports were studied using the methods of lowꢀtemperature
nitrogen adsorption, solidꢀstate NMR spectroscopy, and transꢀ
mission electron microscopy (TEM). Nitrogen adsorption/desꢀ
orption isotherms were studied at 77 K using a Gemini VII 2390
instrument. Prior to measurements, samples were degassed at
*
The sample was not evacuated.
Scheme 1
1
30 С for 6 h. The adsorption data obtained in the range of
relative pressures (Р/Р ) 0.04—0.2 were used for the calculaꢀ
0
tion of the surface area (SBET). The pore volume and pore size
distribution were determined from the adsorption branch of
the isotherms using the Barrett—Joyner—Halenda (BJH) modꢀ
el. The total pore volume (V ) was calculated taking into acꢀ
t
count the amount of nitrogen adsorbed at the relative pressure
Р/Р = 0.995.
0
An analysis by solidꢀstate 13С NMR cross polarization magic
angle spinning (CPMAS) spectroscopy was carried out on a Variꢀ
an NMR Systems instrument at a working frequency of 125 MHz
in the pulse mode at the rotation frequency 10 kHz.
TEM analysis was carried out with a LEO912 AB OMEGA
microscope.
Synthesis of catalysts. Palladium was deposited on the synꢀ
thesized supports by impregnation with a solution of (AcO) Pd
2
II
0
A 20% aqueous solution of NaOH (2.34 g) was added with stirꢀ
ring and stirred for 10 min more. Then, a 37% aqueous solution
of formaldehyde (18.97%) was added dropwise at 50 С, the mixꢀ
ture was stirred for 30 min at 70—75 С, and then urea (7.02 g)
and a 37% aqueous solution of formaldehyde (4.74 g) were addꢀ
ed at once. The reaction mixture was stirred for 4 h at 65 С and
cooled to 20 C. The pH of the reaction mixture was brought to
followed by the reduction of Pd to Pd with sodium borohydride.
The properties of the obtained catalysts are listed in Table 2.
A sample of mesoporous polymer (0.35 g) was preꢀdried for
60 min using a vacuum rotor evaporator at 90 С. The dried
sample and palladium acetate (15.07 mg) were placed in a roundꢀ
bottom 50ꢀmL flask equipped with a magnetic stirrer and a reꢀ
flux condenser, then CHCl (3 mL) was poured, the mixture was
3

7.0 using 0.6 М HCl. After removal of water from the reaction
stirred for 24 h, and CHCl was removed from the mixture using
3
mixture with a vacuum rotor evaporator at 50 С, the final
product was dissolved in ethanol, and a precipitate of sodium
chloride was filtered.
Copolymer F127 (1.0 g) was placed in a roundꢀbottom flask
equipped with a magnetic stirrer and dissolved with stirring in
ethanol (10.0 g). Then, resol precursor UPF (2.7 g) containing
urea (0.40 g), phenol (0.62 g), and formaldehyde (0.50 g) was
added to the solution. A homogeneous solution was obtained
within 10 min of stirring. The solution was poured to the Petri
a rotor evaporator at 30 С. Then NaBH (26 mg) was added to
4
the dried mixture and CHCl (3 mL) and methanol (1.5 mL)
3
were poured. Palladium was reduced for 24 h. The obtained
mixture was three times washed with distilled water and three
times with methanol to remove borax, and the solid product was
separated from the supernatant by centrifugation. The final prodꢀ
uct was a black powder.
The obtained catalysts 1—4 were studied by TEM and Xꢀray
photoelectron spectroscopy (XPS). Palladium in the synthesized
Table 2. Properties of the Pd catalysts on the mesoporous polymer supports
Catalyst
Support
surface/m g
Pore volume
/cm g
Size/nm
of particles
Content
of Pd (%)
2
–1
3
–1
of pore
1
2
3
4
114
131
125
257
0.04
0.09
0.13
0.15
20.4
11.7
7.0
5.2±1.7
4.1±1.2
3.5±1.3
2.2±1.0
1.6
1.6
1.3
1.9
5.0

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Russ.Chem.Bull., Int.Ed., Vol. 63, No. 8, August, 2014
Karakhanov et al.
samples were quantitatively determined on an ICPꢀAES 720ꢀES
spectrometer (Agilent Technologies, USA).
The particleꢀsize distribution and average particle size on the
support surface were found using an analysis by the ImageJ program
of TEM images of the samples containing 100—200 particles.
XPS studies were carried out on a LASꢀ3000 instrument
equipped with an OPXꢀ150 photoelectron analyzer with deꢀ
laying potential. The Xꢀray radiation of the aluminum anode
(
E(AlꢀK) = 1486.6 eV) at the voltage on the tube 12 kV and
emission current 20 mA was applied for the excitation of photoꢀ
electrons. The C1s with a binding energy of 285 eV was used as
a reference to calibrate binding energies.
100 nm
Catalytic experiments were carried out in a steel temperaꢀ
tureꢀcontrolled autoclave equipped with a magnetic stirrer and
a glass tubeꢀbush. The constant temperature in the reactor was
maintained with a UTUꢀ2/77 thermostat with an accuracy of
Fig. 1. TEM image of sample 4.
±
0.5 С. The calculated weighed sample of the powdered cataꢀ
The XPS analysis (Table 3) indicates that the spectra
of samples 1—4 contain the characteristic peaks of the
groups present in the structure of the phenol—urea—formꢀ
aldehyde polymer. In sample 4, the ratio of groups NCON/
C—C is significantly higher than that for samples 1, 2,
and 3. For samples 1 and 2, the ratio of surface areas of the
characteristic peaks changes insignificantly with an inꢀ
crease in the annealing time, whereas an increase in the
annealing temperature for sample 3 results in a considerꢀ
able decrease in the intensity of signals from all groups,
except for aromatic С—С and С—Н bonds.
lyst, a magnetic stirrer, and calculated amounts of the substrate
and solvent were placed in the glass bush. The amount of the
substrate was calculated depending on the palladium content in
the catalyst. Toluene served as a solvent. The bush was placed in
the autoclave, and the autoclave was sealed, filled with hydroꢀ
gen to a pressure of 10 atm, and connected to the thermostat.
The experiments were carried out at 80 С. After the end of the
reaction, the autoclave was cooled and depressurized. The reacꢀ
tion mixture was analyzed by GLC.
A ChromPack CP9001 gas chromatograph with a flameꢀ
ionization detector, a capillary column (length 30 m, inner diaꢀ
meter 0.2 mm) with the SEꢀ30 stationary phase was used for
analysis of the substrates and reaction products. The substrate
conversion was determined from a change in the relative surface
area of peaks of the substrate and products (in %).
The commercially available catalyst Pd/AC, being palladiꢀ
um supported in active carbon, was used for comparison of the
catalytic activity. The Pd content was 10 wt.%, and the average
size of palladium particles in the Pd/AC catalyst was 2.2±0.7 nm.
The specific catalytic activity (turnover frequency on cataꢀ
lytic site per 1 min, TOF) was calculated using the following
formula taking into account the surface palladium atoms
The 13С CPMAS spectrum of sample 4 exhibits signals
at  125—130 (carbon atom of the aromatic ring) and
150—155 (carbon atoms of the aromatic ring linked with
phenolic hydroxyl). An increase in the annealing temperꢀ
Table 3. Results of XPS analysis of the mesoporous polymer
supports
Catalyst
support
Bond energy C1s/eV
Surface area
of peak (%)
TOF = (Cvsubstr/vcat)(1/D ),
M
1
2
3
4
284.3 (aromatic С—С, С—Н)
285.3 (aromatic С—ОН)
286.0 (aliphatic С—ОН)
286.5 (С=О, N—С=О)
287.1 (NCON)
51
12
11
5
where C is conversion; vsubstr and vcat are the fractions of the
substrate and catalyst, respectively; DM is dispersity.
Dispersion defined as the ratio of the number of surface
metal atoms to a total number present was calculated using the
20
9
formula DM = 0.885/d, where d is the average diameter of partiꢀ
284.6 (aromatic С—С, С—Н)
46
10
11
7
cles (nm), and 0.885 is coefficient for palladium corresponding
to the ratio of the atomic volume of the metallic phase M to the
average effective surface area of atom аМ on the particle surface,
which can be calculated by the formula
2
2
2
2
85.6 (aromatic С—ОН)
86.4 (aliphatic С—ОН)
87.1 (С=О, N—С=О)
87.7 (NCON)
25
284.7 (aromatic С—С, С—Н)
85.9 (aromatic С—ОН)
83
6
6
1
3
v /a = A /(N a ),
M
M
r
A
M
2
where A is the relative atomic weight of the metal, NA is
287.0 (aliphatic С—ОН)
288.0 (С=О, N—С=О)
r
Avogadro´s number, and  is the density of the metal.
2
88.9 (NCON)
284.9 (aromatic С—С, С—Н)
86.0 (aromatic С—ОН)
286.9 (aliphatic С—ОН)
Results and Discussion
28
4
5
10
53
2
Results of studying the supports and catalysts. The TEM
images indicate that the structure in the synthesized samꢀ
ples of the supports is ordered (Fig. 1).
2
2
87.7 (С=О, N—С=О)
89.1 (NCON)

Mesoporous catalysts for hydrogenation
Russ.Chem.Bull., Int.Ed., Vol. 63, No. 8, August, 2014
1713
Table 4. Results of XPS analysis of the mesoporous organic
Pdꢀcontaining catalysts and Pd/AC catalyst
palladium oxide (PdO). The presence of palladium oxide
is due to the fact that Pd nanoparticles are readily oxiꢀ
0
dized by air oxygen. The palladium concentration on the
surface on going from sample 1 to sample 4 decreases
more than twofold (see Table 4). This is explained by
a decrease in the palladium amount on the surface with an
increase in the surface area and porosity of the samples,
while the amount of palladium in pores increases.
As can be seen from Table 2, as the surface area of the
support and pore volume increase, the pore and particle
size increases and the fraction of particles with a broad
size distribution increases (Fig. 2). This is related most
likely to the fact that the palladium precursor penetrates
deep inside the support and then forms smaller particles
(2.2 nm) than other catalysts do. According to the XPS
data, the palladium content on the support surface deꢀ
creases regularly (see Table 4). At the same time, the palꢀ
ladium content on the surface of catalysts 1—3 increasꢀ
es and the particle size distribution becomes broader
(see Fig. 2).
Catalyst Bond energy Surface area
* (%)
Pd3d5/2/eV
of peak (%)
Pd
22
C
O
N
0
1
335.2 (Pd )
3
19
81
54
46
16
84
59
41
14
86
42
60
60
46
65
23
13
37.8 (Pd +)
2
0
2
335.8 (Pd )
14
11
10
18
16
17
29
17
10
12
15
—
3
37.3 (Pd +)
2
0
3
336.7 (Pd )
37.5 (Pd2+)
3
0
4
337.4 (Pd )
3
39.1 (Pd +)
2
0
Pd/AC
336.4 (Pd )
3
37.4 (Pd2+
)
*
Weight fractions of elements on the surface.
ature of the template to 450 С results in the formation of
carbonaceous deposit on the sample, which is indicated by
an increase in the surface area of the peak corresponding
to the aromatic С—С and С—Н bonds compared to the
surface areas of other signals in the XPS spectrum of samꢀ
ple 3. In addition, evacuation during annealing results in
a significant decrease in the ratio of groups NCON/C—C
in the samples (see Table 3).
Activity and selectivity of the catalysts in hydrogenation.
The synthesized catalysts were studied in the hydrogenaꢀ
tion of phenylacetylene (A), isoprene (B), 2,5ꢀdimethylꢀ
hexaꢀ2,4ꢀdiene (C), and 1,4ꢀdiphenylꢀ1,3ꢀbutadiene (D)
(Scheme 2, Table 5).
Catalytic activity in the hydrogenation of phenylꢀ
acetylene, isoprene, 2,5ꢀdimethylhexaꢀ2,4ꢀdiene increasꢀ
es with an increase in the size of metallic particles (Fig. 3),
which is consistent with the published data on the hydroꢀ
genation of acetylene and diene hydrocarbons on the palꢀ
According to the data of lowꢀtemperature nitrogen
adsorption, sample 4 has a considerably larger surface area
2
–1
2 –1
(
257 m g ) than samples 1, 2, and 3 (14, 31, and 125 m g ,
respectively) (see Table 2). Sample 4 has a narrower pore
size distribution than other samples. Template annealing
under evacuation conditions destroys the mesoporous strucꢀ
ture. The presence of coke on the sample also strengthens
the porous structure and increases its resistance to mechanꢀ
ical stress, which is indicated by a larger size of the surface
area of sample 3 than those for samples 1 and 2 (see Table 2).
The XPS results (Table 4) show that surface palladium
1
0
ladium nanoparticles. It should be mentioned that the
conventional catalyst for hydrogenation Pd/AC exhibits
somewhat higher activity than catalyst 4 (see Scheme 2),
although the particle sizes of these catalysts are comparaꢀ
ble. It is most likely that this is related to two factors.
First, the porous structure of the Pd/AC catalyst is more
developed and its catalytically active sites are more accesꢀ
sible for reactants. Second, the support of catalyst 4 conꢀ
0
exist on the catalyst as metallic nanoparticles (Pd ) and
Table 5. Results of the hydrogenation of substrates A—D on the mesoporous organic Pdꢀcontaining catalysts
Catalyst
Aa
Bb
Cc
Dd
e
–1
Sf (%)
Ce (%) TOF/min–1 S (%)
Ce (%) TOF/min–1 S (%)
Ce (%) TOF/min–1 S(%)
C (%) TOF/min
1
2
3
4
66
48
42
64
92
2593
1487
1367
1896
1219
98
98
98
89
85
63
50
60
66
94
5001
3082
3911
1849
2484
99
99
99
99
95
131
132
129
147
100
2398
1939
1863
1294
2652
100
100
100
100
199
16
19
15
16
14
21
22
14
19
16
12
13
17
16
15
Pd/AC
a
0
Reaction conditions: Pd /substrate = 1 : 8000 (mol.), 15 min, 80 С, 10 atm H .
2
b
c
d
e
f
0
Reaction conditions: Pd /substrate = 1 : 16000 (mol.), 15 min, 80 С, 10 atm H .
2
0
Reaction conditions: Pd /substrate = 1 : 16000 (mol.), 15 min, 80 С, 10 atm H .
2
0
Reaction conditions: Pd /substrate = 1 : 8000 (mol.), 3 h, 80 С, 10 atm H .
2
Conversion.
In all cases, selectivity (S) based on alkene (in the case of phenylacetylene, based on styrene).

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Russ.Chem.Bull., Int.Ed., Vol. 63, No. 8, August, 2014
Karakhanov et al.
a
e
N (%)
5
4
3
2
1
0
0
0
0
0
1
00 nm
2
4
6
8
10
12 d/nm
b
f
N (%)
8
6
4
2
0
0
0
0
1
00 nm
2
4
6
8
10 d/nm
c
g
N (%)
00
1
8
6
4
2
0
0
0
0
1
00 nm
2
4
6
8
10 d/nm
d
h
N (%)
8
6
4
2
0
0
0
0
5
0 nm
2
4
6
8
d/nm
Fig. 2. TEM images (a—d) and histograms of the Pd particle distribution (e—h) for catalysts 1—4, respectively; N is the fraction of
particles with the sized.

Mesoporous catalysts for hydrogenation
Russ.Chem.Bull., Int.Ed., Vol. 63, No. 8, August, 2014
1715
Scheme 2
Sup is support.
tains oxygenꢀcontaining moieties, due to which the elecꢀ
tron density on the metal increases, decreasing the specifꢀ
ic catalytic activity.
lished data, the number and the surface area of Pd(111)
faces, which are the most active in hydrogenation, decrease
1
1
with a decrease in the palladium particles, while for adꢀ
sorption of 1,4ꢀdiphenylꢀ1,3ꢀbutadiene a higher molecuꢀ
lar area on the metal face is needed than for adsorption of
other substrates. Correspondingly, catalytic activity deꢀ
creases with a decrease in the size of palladium partiꢀ
According to the performed studies, palladium exists
in two valent states on the support surface and exerts no
effect on the catalytic activity in hydrogenation, because
0
palladium oxide is rapidly reduced to Pd due to the interꢀ
2
action with gaseous hydrogen from the reaction mixture.
For the hydrogenation of 1,4ꢀdiphenylꢀ1,3ꢀbutadiene,
the activity of catalysts 1, 2, and 4 remains almost unꢀ
changed with a change in the palladium particle size (see
Table 5). However, for catalyst 3 with an average particle
size of 3.5 nm, catalytic activity decreases twofold and
TOF/min–1
5
000
–
1
TOF is 14 min . The surface area of the support and the
average particle size exert, most likely, no effect on the
catalytic activity (see Table 2, Fig. 3). A similar depenꢀ
dence can be due to the fact that in the case of catalysts 1
and 2 hydrogenation occurs on the external surface of the
support and the dimensional effect of the palladium nanoꢀ
particles plays the decisive role. Catalyst 4 has a large
surface and the substrate can penetrate deep inside the
support. However, it can be assumed that the product do
not immediately leave the support pores because of diffuꢀ
sional restrictions, resulting in a decrease in the TOF. It is
most likely that the products of 1,4ꢀdiphenylꢀ1,3ꢀbutadiꢀ
ene hydrogenation can more easily be desorbed from the
surface of catalyst 3 than from the surface of catalyst 4. In
this case, the dimensional effect exerts a stronger effect
than the geometry of the support. According to the pubꢀ
4000
A
3
2
1
000
000
000
B
C
D
2.2
3.5
4.1
5.2
d/nm
Fig. 3. Catalytic activity (TOF) in the hydrogenation of phenylꢀ
acetylene (A), isoprene (B), 2,5ꢀdimethylhexaꢀ2,4ꢀdiene (C),
and 1,4ꢀdiphenylꢀ1,3ꢀbutadiene (D) vs palladium particle size (d)
on the support surface.

1
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Russ.Chem.Bull., Int.Ed., Vol. 63, No. 8, August, 2014
Karakhanov et al.
cles,12,13 which is a reason for decreasing catalytic activity
observed on going from catalysts 1 and 2 to catalyst 4.
In the case of 1,4ꢀdiphenylꢀ1,3ꢀbutadiene hydrogenaꢀ
tion, the selectivity for alkenes was low (7—16%) (see
Table 5). This can be explained by a stronger adsorption of
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. Y. Shao, Z. Xu, H. Wan, Y. Wan, H. Chen, S. Zheng, D. Zhu,
1
,4ꢀdiphenylꢀ1,3ꢀbutadiene on the catalyst surface due to
—ꢀstacking interactions with aromatic groups on the
3
support surface. As a result, alkenes are poorly desorbed
from the support surface and can undergo deeper hydroꢀ
genation to 1,4ꢀdiphenylbutane. The lowest selectivity
[
4
(
7%) corresponds to catalyst 3 that, according to the XPS
Catal. Commun., 2011, 12, 1405.
data, contains the highest number of aromatic С—С bonds
compared to other samples.
5. Q. Hu, J. Pang, N. Jiang, J. E. Hampsey, Y. Lu, Microporous
Mesoporous Mater., 2005, 81, 149.
According to the performed studies, the synthesized
catalysts turned out to be more active in hydrogenation
than Pd/С. In all cases, the selectivity for olefins is higher
with the catalysts described in this work (see Table 5) than
that recorded in the presence of the Pd/C catalyst.
Thus, the palladium catalysts using mesoporous polymers
as supports were synthesized. The catalysts were tested in
6. Y. Meng, D. Gu, F. Zhang, Y. Shi, H. Yang, Z. Li, C. Yu,
B. Tu, D. Zhao, Angew. Chem., 2005, 117, 7215.
7
8
9
. S. Tanaka, Y. Katayama, M. P. Tate, H. W. Hillhouse,
Y. Miyake, J. Mater. Chem., 2007, 17, 3639.
. J. Yang, Y. Zhai, Y. Deng, D. Gu, Q. Li, Q. Wu, Y. Huang,
B. Tu, D. Zhao, J. Colloid Interface Sci., 2010, 342, 579.
. Б. Mastalir, Z. Király, F. Berger, Appl. Catal., A, 2004,
2
69, 161.
–1
the hydrogenation of isoprene (TOF = 1850—5000 min ),
10. Yu. A. Ryndin, M. V. Stenin, A. I. Boronin, V. I. Bukhꢀ
tiyarov, V. I. Zaikovskii, Appl. Catal., 1989, 54, 277.
11. D. Uzio, G. Berhault, Cat. Rev. Sci. Eng., 2010, 52, 106.
12. W. M. H. Sachtler, R. A. van Santen, Advances in Catalysis,
Vol. 26, Academic Press, San Diego, 1977, p. 69.
–
1
phenylacetylene (TOF = 900—2590 min ), 2,5ꢀdimethꢀ
–
1
ylꢀ2,4ꢀhexadiene (TOF = 1294—2400 min ), and 1,4ꢀdiꢀ
–
1
phenylꢀ1,3ꢀbutadiene (TOF = 14—22 min ). The selecꢀ
tivity for alkenes in hydrogenation was 85—100%. The exꢀ
ception is the hydrogenation of 1,4ꢀdiphenylꢀ1,3ꢀbutadiene
in which the selectivity is 7—16%. The decreased selectivꢀ
ity can be explained by a facile adsorption of 1,4ꢀdiphenylꢀ
1
3. R. Coekelbergs, A. Frennet, G. Lienard, P. Resibois, J. Phys.
Chem., 1963, 39, 604.
1
,3ꢀbutadiene on the support surface due to —ꢀstacking
interactions with aromatic groups of the support surface.
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 14ꢀ03ꢀ00210).
Received June 5, 2014;
in revised form July 7, 2014