Pt-And Pd-containing nanodiamonds in hydrogenation and hydroamination reactions1

Article abstract of DOI:10.1134/S0023158412040052

The catalytic activity of platinum-And palladium-containing nanodiamonds has been investi-gated in liquid-phase nitrobenzene, allyl alcohol, and cyclohexene hydrogenation and propanal hydroami-nation with 4-Aminobenzoic acid as model reactions. The catalysts suggested are significantly more active than commercial Pd/C. The catalysts with a low metal weight content are the most effective in liquid phase catalytic hydrogenation. Pleiades Publishing, Ltd., 2012.

Full text of DOI:10.1134/S0023158412040052

ISSN 0023ꢀ1584, Kinetics and Catalysis, 2012, Vol. 53, No. 4, pp. 482–485. © Pleiades Publishing, Ltd., 2012.
Published in Russian in Kinetika i Kataliz, 2012, Vol. 53, No. 4, pp. 505–508.
Ptꢀ and PdꢀContaining Nanodiamonds in Hydrogenation
1
and Hydroamination Reactions
a,
a
b
b
N. A. Magdalinova *, M. V. Klyuev , N. N. Vershinin , and O. N. Efimov
a
Ivanovo State University, Ivanovo, 153025 Russia
b
Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow oblast, 142432 Russia
eꢀmail: mn2408@mail.ru
*
Received November 30, 2011
Abstract—The catalytic activity of platinumꢀ and palladiumꢀcontaining nanodiamonds has been investiꢀ
gated in liquidꢀphase nitrobenzene, allyl alcohol, and cyclohexene hydrogenation and propanal hydroamiꢀ
nation with 4ꢀaminobenzoic acid as model reactions. The catalysts suggested are significantly more active
than commercial Pd/C. The catalysts with a low metal weight content are the most effective in liquid phase
catalytic hydrogenation.
DOI: 10.1134/S0023158412040052
1
In recent years, special attention has been given to
EXPERIMENTAL
obtaining catalysts based on various carbon nanomaꢀ
terials: fullerenes [1, 2], fullerene black [1, 2], carbon
nanotubes and nanofibers [1, 3, 4], nanodiamonds
Nanodiamonds containing Pd or Pt were syntheꢀ
sized according to a patented method [12]. The detonaꢀ
2
–1
tion NDs had a specific surface area of 307–314 m g
the average size of the crystalline diamond core of the
(
NDs) [5–9], etc., which, owing to their structure,
show high activity, selectivity, and stability [1]. Earlier
3, 4], we demonstrated that the nature and size of the
(
ND particles was ~4 nm). The total percentage of
nonꢀcarbon admixtures in the NDs was no higher than
[
metal sites and their accessibility to the substrate molꢀ
ecules are determined by the nature of the support.
0
.5 wt %. Samples of the Pdꢀ and Ptꢀcontaining NDs
were combined with active carbon (180 mg of catalyst +
20 mg of carbon), so the total weight was of the samꢀ
ple was 1 g.
Nanodiamonds are a carbon nanostructure with a
diamondꢀtype crystal lattice. Usually, the size of
nanocrystals is 1 to 10 nm. The surface of ND crystals
is always defective, and its structure depends on the
ND production and purification procedure [10–13].
The surface carbon atoms in ND have dangling bonds,
which are favorable for generation of uniform metal
sites and ensure the maximum increase in the catalytꢀ
ically active surface area, which is necessary for
adsorption of reactants, for the reaction itself, and for
product desorption. The “righter” the configuration
of the metal sites and the higher their uniformity, the
higher the selectivity of the catalyst. We have shown
8
The proportion of the catalytically active metal in
the Pt/ND and Pd/ND samples was determined by
electron probe Xꢀray microanalysis; the total specific
surface area, by the BET method. The relative error in
the determination of the platinum and palladium conꢀ
tents of the catalyst was no larger than 10%. Electron
±
probe Xꢀray microanalysis was carried out on a VEGA
TS 5130MM fully PCꢀcontrolled scanning electron
microscope (CamScanMV2300)TP1PT) equipped
with secondary electron and backscatter electron
detectors and an energy dispersive Xꢀray microanaꢀ
lyzer with an INCA Energy2 semiconducting Si(Li)
detector. The results of electron probe Xꢀray
microanalysis were calculated using the INCA Energy
[
14, 15] for the first time that use of detonation NDs as
supports for platinum group metals makes it possible
to obtain platinum and palladium clusters with a charꢀ
acteristic diameter of 5 nm and a characteristic thickꢀ
ness of 0.4 to 1.2 nm.
2
00 program, which was followed by recalculation of
the resulting data using the TP3PT program package,
In the present work, we consider the possibility of developed at the Institute of Experimental Mineralꢀ
employing the NDꢀbased catalysts in model liquidꢀ ogy, Russian Academy of Sciences. The analysis was
phase reactions, namely, nitrobenzene, allyl alcohol, carried out at an accelerating voltage of 20 kV. The
and cyclohexene hydrogenation and propanal absorbed electron current on the standard cobalt samꢀ
ple was 516–565 pA, and that on the samples examꢀ
ined was 540–620 pA. The size of the electron probe
on the sample surface was 157–200 nm. The amount
of titanium and chlorine impurities was mo larger than
hydroamination with 4ꢀaminobenzoic acid, which are
of practical interest to the pharmaceutical industry.
1
This article was translated by the authors.
482

Ptꢀ AND PdꢀCONTAINING NANODIAMONDS IN HYDROGENATION
483
0
.3 and 0.1 wt %, respectively. The ash content of the where
ρ
is the density of diamond and
ρ
is the denꢀ
M
ND
initial BDs did not exceed 2 wt %.
sity of the metal. The following values were used in the
3
3
The specific surface area of palladium and platiꢀ calculations:
ρ
= 3.5 g/cm ,
ρ
= 12.02 g/cm ,
ND
Pd
ρ
= 21.45 g/cm3, SND = 312 m /g (for ND with palꢀ
2
num (SМ) was calculated as
Pt
2
SМ = [
S – S mND(1 – k1k2)]/mM,
Σ
ND
ladium), and SND = 313 m /g (for ND with platinum).
where mND is the ND content of the catalyst (in grams The SM values are presented in Table 1.
per gram of catalyst), mM is the Pd or Pt content of the
The hydrogenation reaction was performed as folꢀ
catalyst (in grams per gram of catalyst), SND is the speꢀ low (Scheme 1): 30 mg of a catalyst and 10 mg of
cific surface area of ND determined by extrapolation NaBH
to zero Pd or Pt content,
were placed under a solvent layer (10 mL of
4
S
is the total specific surface ethanol) in a reactor, and the catalyst was activated for
Σ
1
0 min. Next, 1 mmol of a substrate (nitrobenzene,
area of the catalyst (ND + metal), k1 is the constant
accounting for the decrease in the ND surface area at
the metal cluster–ND contact places, and k2 is the
constant that accounts for the fact that part of the Pd
or Pt particles is not located on the ND surface, formꢀ
ing separate clusters. In previous studies [14, 15] it was
found that 20–30% of the catalytic metal particles of
the total metal weight form separate clusters. The
value of k2 is 0.7–0.8. The value of k1 for an average
metal cluster thickness of 0.8–1.1 nm can be defined
using the formula
allyl alcohol, or cyclohexene) was introduced under
flowing hydrogen. The reaction temperature was 318 K,
and the hydrogen pressure was 0.1 MPa.
The hydroamination of propanal with 4ꢀamiꢀ
nobenzoic acid (Scheme 2) was performed as follow:
30 mg of a catalyst and 10 mg of NaBH were placed
4
under a solvent layer (5 mL of ethanol) in a reactor,
and the catalyst was activated for 10 min. Next, a soluꢀ
tion of 4ꢀaminobenzoic acid (0.274 g, 2 mmol) and
propanal (0.15 mL, 2 mmol) in 20 mL of ethanol were
introduced. The reaction mixture was purged with
hydrogen, and the process was carried out under the
above conditions.
m ρ
M
ND
M
k1 =
,
mND
ρ
NO2
CH2 CH CH2 OH
–H
2
O
NH2
H , Cat.
2
CH3 CH2 CH2 OH
Scheme 1.
O
HOOC
NH2
+
C CH2 CH3
HOOC
N CH CH2 CH3
–H O
2
H
H , Cat.
2
HOOC
NH CH CH CH3
H , Cat.
2
HOOC
NH CH2 CH2 CH3
Scheme 2.
The reaction rate was measured as hydrogen uptake
Under the conditions examined, both reactions
using the volumetric method. The catalytic activity of were zerothꢀorder with respect to the substrate and
the samples was evaluated in terms of the turnover firstꢀorder with respect to the catalyst and hydrogen.
–
1
number of the catalyst (TON, min ), i.e., the number
The hydrogenation and hydroamination products
of moles of the substrate converted per mole of metal were analyzed on a Model 3700 commercial chroꢀ
per minute. The efficiency of the NDꢀbased catalysts matograph with a flameꢀionization detector using a
was compared with the efficiency of the commercial glass column (diameter of 3 mm, length of 2000 mm)
2
Pd/C catalyst (1 wt % Pd,
S
= 14 m /g).
packed with Lucopren G–1000 (5%) on Chromaton
Σ
KINETICS AND CATALYSIS Vol. 53
No. 4
2012

484
MAGDALINOVA et al.
Table 1. Characteristics of the Pd/ND and Pt/ND catalysts
A comparison of the TON values for nitrobenzene
hydrogenation shows that the activity of the catalyst
decreases as the metal (Pt or Pd) content is increased
and the rates of nitrobenzene hydrogenation over them
Parameter
(
Table 1). This finding points to the inefficiency of the
Metal content,
104,
–1
metalꢀrich samples. The TON value for commercial
S
m /g
,
S
m /g
,
TON,
wt %
Σ
M
2
W ×
–1
2
mol L s–1 min
–1
Pd/C under the same conditions is 2.2 min .
A number of substrates, namely, nitrobenzene, allyl
alcohol, cyclohexene, and 4ꢀ(propylydenamino)benꢀ
zoic acid (product of propanal and 4ꢀaminobenzoic
acid condensation, Scheme 2), were studied in hydroꢀ
genation hydrogenated over 10 wt % Pd/ND. Accordꢀ
ing to GLC data, the substrates underwent total conꢀ
version without yielding any byꢀproducts.
Pd
3
6
9
305 140 ± 70
299 160 ± 40
293 165 ± 40
281 120 ± 40
3.2
4.6
6.3
7.5
8.0
127 ± 13
90 ± 9
83 ± 9
74 ± 8
65 ± 6
1
2
5
1
263
50 ± 20
Pt
The choice of substrates was dictated by their pracꢀ
tical significance and by interest in the mechanisms of
reduction of their functional groups (–NO2, >C=C<,
5
0
5
0
5
311 324 ± 60
307 304 ± 40
295 244 ± 40
288 240 ± 40
277 220 ± 40
0.7
0.6
3.1
3.0
3.0
29 ± 3
12 ± 1
42 ± 5
32 ± 3
26 ± 3
1
1
2
2
>C=N–), which differ in their nature and occupy difꢀ
ferent positions.
Nitrobenzene hydrogenation proceeds most
readily: the reaction rate is 1.4 and 1.8 times higher
than in the case of allyl alcohol and cyclohexene,
respectively, and 26 times higher than the hydrogenaꢀ
Table 2. Activity of the 10 wt % Pd/ND catalyst in the hyꢀ tion rate of 4ꢀ(propylydenamino)benzoic acid
drogenation of some organic compounds
(Table 2). This may be due to the higher steric accessiꢀ
bility and higher electronegativity of the NO group,
2
Parameter
which is favorable provided that activated hydrogen
bears a positive charge [16]. The terminal double bond
>С=C< in allyl alcohol is also more accessible than
the inner double bond in cyclohexene. The low rate of
hydrogenation of 4ꢀ(propylydenamino)benzoic acid is
due to the >С=N– bond being difficult to access
because of steric effects.
Substrate
4
W × 10 ,
TON, min–1
mol L s–1
–1
Nitrobenzene
5.2
3.8
2.9
0.2
60 ± 6
45 ± 5
35 ± 4
5 ± 1
Allyl alcohol
Cyclohexene
The results obtained can also be explained in terms
of the significant difference between the mechanisms
4ꢀ(Propylidenamiꢀ
no)benzoic acid
of –NO , >C=C<, and >C=N– hydrogenation.
2
In the hydroamination reaction (Scheme 2) over
the commercial catalyst Pd/C under similar condiꢀ
tions, TON = 0.3 min , almost 17 times smaller than
NꢀAWꢀDMCS. The carrier gas was argon; injection
port temperature, 200 ; oven temperature, 230
carrier gas flow rate, 1.60
.1–0.5 L.
°
С
°
С
;
–1
–1
±
0.02 L h ; sample volume,
the TON value for Pd/ND.
0
µ
Thus, the Ptꢀ and Pdꢀcontaining NDs can be used
in the hydrogenation of unsaturated and functionalꢀ
ized organic compounds. The most effective catalysts
for liquidꢀphase hydrogenation are Pd/ND and
RESULTS AND DISCUSSION
The platinumꢀ and palladium–containing NDs Pt/ND with a relatively low weight percentage of
with different weigh percentages of supported metal metal.
2
had a total specific surface area of 263 to 311 m /g and
2
SM = 50–324 m /g (Table 1). Experimental data on
nitrobenzene hydrogenation in the presence of
Pd/ND and Pt/ND (Table 1) show that, every time
ACKNOWLEDGMENTS
This work was carried out in the framework of the
the metal content of the Pd/ND catalyst is increased
by 3 wt %, the reaction rate ( ) increases by a factor program “Development of Basic Research in Creation
W
of 1.4–1.1. For the Pt/ND samples with a platinum of Functional Nanomaterials at the Chemical Physics
content of 5 and 10 wt % and 15–25 wt %, the reaction Educational Scientific Complex of Ivanovo State Uniꢀ
rate has similar values. For the 15 wt % Pt/ND cataꢀ versity and at the Institute of Problems of Chemical
lyst,
W is 5 times higher than for the samples containꢀ Physics, Russian Academy of Sciences” (project RNP
ing 5 and 10 wt % Pt (Table 1).
2.2.1.1/11465).
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Ptꢀ AND PdꢀCONTAINING NANODIAMONDS IN HYDROGENATION
485
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2012