Polymerꢀimmobilized Pd nanoparticles
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 10, October, 2009
2071
PdCl •4H O (reagent grade), acrylamide (AAm) (99.0%, Fluꢀ
under a constant atmospheric hydrogen pressure at 36 °C with
vigorous stirring (300—400 rocking min– ). Hydrogen was fed to
the reactor from a calibrated receiver with the waterꢀgate valve.
Before the introduction of the substrate into the reactor, the
solvent and catalyst were treated with hydrogen for 15 min diꢀ
rectly in the reactor with stirring. The reaction rate was calculatꢀ
ed from the kinetic dependences of the hydrogen consumption
in time. The discrepancies in parallel entries did not exceed 5%.
Xꢀray photoelectron spectra (XPS) were recorded on an
ESꢀ2401 spectrometer with the magnesium anode. The power of
the Xꢀray tube was 200 W, the pressure in the analyzer chamber
2
2
1
ka), and nitroꢀ, 2,4ꢀdinitroꢀ, and trinitrotoluene (NT, DNT,
and TNT, respectively) (reagent grade) were used without addiꢀ
–
3
tional purification. Concentrated HNO (ρ = 1.18 g cm ) was
3
distilled under atmospheric pressure, and the main fraction was
taken at b.p. 110 °C. Inorganic supports were silica gels 60
(
220—240 mesh, Lancaster) preꢀactivated (calcination with
evacuation at 450 °C) and carbon black (specific surface area
2
–1
2 –1
Ssp = 850 m g ) and Al O (S = 123 m g ).
2
3
sp
II
Synthesis of Pd(NO ) •2H O. Pd nitrate was synthesized
3
2
2
by the reaction of freshly distilled concentrated HNO and freshly
3
–
2
–6
precipitated palladium hydroxide (2.6 g, 1.84•10 mol), which
was obtained by the treatment of the Na PdCl complex salt
was 10 Pa, and the energy of the analyzer was 50 eV. The
spectrometer was calibrated by the Au4f7/2 line with E = 84 eV.
2
4
(
5.5 g, 1.84•10–2 mol) with sodium hydroxide. Found (%):
The bond energy (Е ) of the line of the C1s electrons in the alkyl
b
H, 1.4; N, 12.4; Pd, 40.4. Calculated (%): H, 1.5; N, 10.5; Pd,
9.9. IR (KBr pellet), ν/cm–1: 850, 1386 (NO ), 1650. XPS,
E/eV: Pd3d5/2, 338.8; N1s, 407.2; O1s, 532.8.
group was accepted to be 285.0 eV. The accuracy of determinaꢀ
tion of the line position by the scale of bond energies was
0.1—0.2 eV. The mathematical processing of the spectra was
3
3
1
8
Synthesis of Pd(H C=CHCONH ) (NO ) (hereinafter,
performed according to the earlier described procedure.
Standard samples in the XPS analysis were PdCl •4H O
2
2 2
3 2
PdAAm). The synthesis of PdAAm was carried out by the modiꢀ
fied procedure for the preparation of acrylamide complexes of
transition metal nitrates.17 Palladium(II) nitrate and AAm were
mixed in a mole ratio of 1 : 5 in inert atmosphere and triturated
to a pasty state. Then the mixture was washed with anhydrous
ether and dried in vacuo to a constant weight. Found (%): C, 20.8;
H, 3.5; N, 15.1; Pd, 29.4. Calculated (%): C, 19.4; H, 2.7;
2
2
(Е (Pd3d ) = 337.5 eV) and palladium black (Е (Pd3d5/2) =
b
5/2
b
= 335.5 eV).
Intermediate compounds and reaction products of hydrogeꢀ
1
nation were identified by Н NMR in acetoneꢀd on a Bruker
6
ACꢀ200P spectrometer (200 MHz). The XPS analysis of the
powders was carried out on a DRON UMꢀ2 spectrometer using
CuꢀKα radiation. The microscopic studies were carried out with
a JEMꢀ3010 transmission electron microscope.
N, 15.0; Pd, 28.6. IR (KBr pellet), ν/cm– : 3190 (ν NH), 3428
1
s
(
ν NH), 1665 (C=O), 1384 (NO ).
as
3
Preparation of PdAAm on the inorganic support surface. The
The specific surface area of the inorganic supports and polyꢀ
merꢀhybrid nanocomposites and the pore size distribution were
synthesis of PdAAm in the presence of an inorganic support
SiO , Al O , C) was carried out according to the above deꢀ
(
determined from N adsorption at 77 K by the static volumetꢀ
2
2
3
2
scribed procedure from the assumption that the Pd content in
the catalyst of the mixed type, namely, polymer + SiO (Al O ,
ric method on an AUTOSORBꢀ1 instrument (Quantachroꢀ
me, USA).
2
2
3
C), is 5—10 wt.% g–1. In a typical experiment, a mixture of
II
calculated amounts of Pd nitrate, AAm, and SiO were trituꢀ
2
Results and Discussion
rated in an agate mortar in the box with an inert atmosphere to
the pasty state, washed with benzene and ether, and dried in vacuo
Synthesis of Pd(H C=CHCONH )(NO ) . The acrylꢀ
2
2
3 2
for at least 12 h at 30 °C. Pd content (wt.%): 5.2 (PdAAm/SiO ),
2
II
amide complex Pd nitrate was synthesized by the substiꢀ
tution of water of crystallization in the crystalline hydrate
of metal nitrate for AAm molecules. The elemental analyꢀ
sis and XPS data for the synthesized complex are given
in Table 1.
8
.9 (PdAAm/Al O ), 10.2 (PdAAm/C).
2 3
Preparation of Pd/C. Palladium of carbon was obtained by
the impregnation of activated carbon (AGꢀ3M trade mark, S
=
sp
2
–1
=
500 m g ) with an aqueous solution of PdCl followed by the
2
reduction with NaBH at 40 °C and additional heating at 80 °C
4
for 15 min. The prepared catalyst was filtered off and washed
The IR spectroscopic data indicate that the metal atom
is coordinated to the oxygen atoms of the carbonyl group
with distilled Н О and dried for 3—5 h at 110 °C. The content of
2
Pd was 5 wt.%.
Frontal polymerization of PdAAm and PdAAm/SiO (Al O ,
2
2
3
C). The PdAAm or PdAAm/SiO (Al O , C) samples for fronꢀ
tal polymerization were pressed as pellets with the diameter
Table 1. Elemental analysis data and the relative content of eleꢀ
ments according to the XPS data (Y) for the acrylamide comꢀ
plexes of Pd nitrate
2
2
3
II
d = 0.5—0.8 cm, height h = 1.2—1.5 cm, and density ρ =
=
1.45±0.02 g cm–3 and placed in a glass ampule. To initiate
polymerization, the bottom region of the ampule with the samꢀ
ple was immersed by 0.2 cm into the bath with the heat carrier
Complex
Found
Calculated
Y (at.%)
(
wt.%)
С
O
N
Pd
(
Wood alloy) for 10—15 s. The reaction rate was estimated from
С
H
N
Pd
the migration of the front of the colored zone in time. The powꢀ
dered polymeric and hybrid nanocomposite products were
washed with methanol and ether and then dried in vacuo at room
temperature to a constant weight.
Pd(NO3)2
PdAAm
—
1.4 12.4 40.4
.5 10.5 39.9
20.8 3.5 15.1 29.4
9.4 2.7 15.0 28.6
—
68 21 10.5
1
52
27 19
2
Catalytic hydrogenation of diꢀ and trinitrotoluenes. Experiments
on the hydrogenation of nitroaromatic compounds was carried
out in a nonꢀflow glass reactor (soꢀcalled duckꢀreactor) in methꢀ
anol with the substrate concentration (4.72—14.5)•10–3 mol L
1
PdAAm/SiO2
PdAAm/C
—
—
—
—
—
—
5.2
10.2
16
83
57
14
6
0.7
2.8 0.2
–1