The use of palladium nanoparticles supported on active carbon for synthesis of disproportionate rosin (DPR)

Abstract

Disproportionate rosin (DPR) is a mixture of rosin acids with dehydro-abietic acid as its major component. Alkaline salts of DPR are used as emulsifier surfactant in emulsion polymerization reactions. In this work, synthesis of DPR by the use of palladium nanoparticles loaded on activated carbon was studied. The nanocatalyst was characterized by TEM, SEM, XRD, N2 adsorption–desorption and AAS. The reusability of the prepared nanocatalyst was successfully examined three times with only a very slight loss of catalytic activity.

Full text

ORIGINAL RESEARCH
The use of palladium nanoparticles supported on active carbon
for synthesis of disproportionate rosin (DPR)
Ramin Mostafalu
1
•Akbar Heydari
1
•Abbas Banaei
2
•Fatemeh Ghorbani
2
•
Marzban Arefi
1
Received: 6 December 2016 / Accepted: 12 January 2017
ÓThe Author(s) 2017. This article is published with open access at Springerlink.com
Abstract Disproportionate rosin (DPR) is a mixture of
rosin acids with dehydro-abietic acid as its major compo-
nent. Alkaline salts of DPR are used as emulsifier surfac-
tant in emulsion polymerization reactions. In this work,
synthesis of DPR by the use of palladium nanoparticles
loaded on activated carbon was studied. The nanocatalyst
was characterized by TEM, SEM, XRD, N
2
adsorption–
desorption and AAS. The reusability of the prepared
nanocatalyst was successfully examined three times with
only a very slight loss of catalytic activity.
Keywords Disproportionated rosin DPR Gum rosin 
Palladium nanoparticles Palladium–carbon
Introduction
Disproportionated rosin (DPR) is a mixture of rosin acids
with dehydro-abietic acid (DAA) (2a) as its major com-
ponent [1]. Because of its low brittleness, high thermal
stability, good oxidation resistance and light color, DPR is
widely used in the production of butadiene and chloroprene
rubber [2]. Alkaline salts of DPR are used as emulsifier
surfactant in emulsion polymerization reactions. This
reaction is used for polystyrene and styrene butadiene
rubber (SBR) preparation in petrochemical industries
[3,4]. The main constituent of the DPR (i.e., DAA) is also
of potential value in the pharmaceutical industry and a
number of its derivatives have many biological activities
such as anti-cancer effects [5–7].
Disproportionation of rosin is described as a hydrogen
exchange between molecules of resin [8,9]. The main
product of the reaction is DAA, and reaction can be viewed
as the conversion of abietic acid (AA) to DAA (Fig. 1). At
temperatures between 250 and 280 °C, the reaction is very
slow and the addition of a catalyst increases the reaction
rate.
Iodide, sulfur, lithium and iron salt, have traditionally
been used to promote or catalyze disproportionation of
rosin [9–11]. At the present time, palladium catalysts have
been of great interest, in part because of the good proper-
ties that the DPR feature regarding light color, low odor,
medium softening-point, and excellent resistance to oxi-
dation [1,2,12–15]. In the continuation of our research
[16–21], the disproportionation of rosin with Pd nanopar-
ticles supported on activated carbon (AC) was studied in
this work.
Experimental section
Materials and methods
The reagents were purchased from the Merck, Sigma-
Aldrich and Daejung companies and were used without
further purification. The starting gum rosin was commer-
cially available. For TEM studies, samples were placed on
copper grids covered with carbon film and examined with a
Electronic supplementary material The online version of this
article (doi:10.1007/s40097-017-0220-y) contains supplementary
material, which is available to authorized users.
&Akbar Heydari
heydar_a@modares.ac.ir
1
Chemistry Department, Tarbiat Modares University,
P.O. Box 14155-4838, Tehran, Iran
2
Research and Development, Padideh Shimi Jam Co.,
Eshtehard Industrial Town, Karaj, Iran
123
J Nanostruct Chem
DOI 10.1007/s40097-017-0220-y

300 keV transmission electron microscope (TEM) JEM-
3010 UHR (Jeol Ltd., Japan), equipped with a
retractable high-resolution slow scan CCD-Camera (Gatan
Inc., USA) with GOS phosphorous scintillator and lan-
thanum hexaboride cathode as the electron source. The
X-ray powder patterns were recorded with a D8
ADVANCE (Bruker, Germany) diffractometer (CuK-radi-
ation). Pd atomic absorption spectroscopy (AAS) was
performed on an Atomic Absorption Spectrometer Varian
SpectrAA 110. Prior to analysis, the sample was added to
hydrochloric acid and H
2
O
2
and the reaction was carried
out for 180 min at 90 °C. The solutions were then diluted,
and analyzed by AAS.
Preparation of palladium chloride
Palladium chloride is prepared by dissolving 1 g palladium
metal in 4 ml freshly prepared aqua regia (mixture of nitric
acid (99%) and hydrochloric acid (37%) optimally in a
volume ratio of (1:3) for 4 h at 80 °C. After 4 h a blood-red
solution was obtained.
Preparation of palladium nanoparticles loaded
on activated carbon (Pd-NP-AC)
Pd nanoparticles were loaded on AC through a liquid phase
reduction method. 19 g AC was suspended in 50 ml of
water. Prepared palladium chloride was added and the
reaction was continued for 2 h at 80 °C. Subsequently, the
mixture was filtered in vacuum and rinsed using Millipore
water. Prepared active carbon–palladium chloride was
suspended in 60 ml of water. The pH of solution was
adjusted to 9 by the use of NaOH and the suspension was
stirred for 2 h. After 2 h, 60 ml of formalin (37%) reduc-
tant was added dropwise to the solution. The obtained
suspension was magnetically stirred for two additional
hours at 80 °C. Subsequently, the mixture was filtered in
vacuum and rinsed using Millipore water. The resultant
product was dried in a furnace at 105 °C overnight. The
final amount of Pd loaded in sample was determined by
atomic absorption.
Disproportionation of rosin by Pd-NP-AC catalyst
100 g of rosin were inserted into a 250-ml three-neck
round-bottom flask equipped with a mechanical stirrer,
temperature sensor and condenser. The reaction was run at
280 °CinanN
2
atmosphere to avoid oxidation. Once the
reaction temperature was reached, the Pd-NP-AC catalyst
(0.05% w/w) was added to the reaction. At the reaction
temperature, a zero time sample was withdrawn before the
catalyst was added, and more samples were taken during
the first 6 h following the addition of the catalyst. A
quantitative GC–FID analysis of the withdrawn samples
was performed. Samples were methylated with tetram-
ethylammonium hydroxide solution (10%) and analyzed on
an Agilent model 7890A gas chromatograph with a flame
Fig. 1 Disproportionation of
rosin
900
1400
1900
2400
2900
3400
3900
10 20 30 40 50 60 70 80 90
2 Teta (degree)
Fig. 2 XRD pattern of Pd-NP-AC catalyst
Fig. 3 TEM image of Pd-NP-AC catalyst
J Nanostruct Chem
123

ionization detector. The instrument conditions are as
follows:
Inlet: heater =300 °C; pressure =10.8 psi; total
flow =14 ml/min;
Septum purge: flow =3 ml/min; split =10:1;
Analytical column: DB 1701 (60 m);
Oven: initial =100 °C, 5 min; ramp 1:2 °C/min;
270 °C 40 min; run time 130 min;
Detector: FID; heater =300 °C; H
2
flow =30 ml/min;
air flow =300 ml/min; make up flow =40 ml/min.
Results and discussion
Pd-NP-AC was prepared by the method described by
Mamlouk et al. [22] with some modifications. The structure
of prepared compounds was characterized with various
techniques, including TEM, BET, XRD and AAS. The
XRD pattern of the Pd-NP-AC sample is shown in Fig. 2.
Fig. 4 Elemental maps of the
Pd-NP-AC catalyst with carbon
on the left and palladium on the
right
Fig. 5 SEM images of the Pd-
NP-AC catalyst
0
100
200
300
00.51
p/p0
Va/cm3(STP) g-1
Fig. 6 Adsorption/desorption isotherm of Pd-NP-AC catalyst
Vmmc[551 3(STP) g-1]
as,BET m[876 2 g-1]
038201C
Total pore volume(p/p0=0.990) 0.39 [cm3 g-1]
Average pore diameter 2.29 [nm]
0
0.002
0.004
0.006
0 0.25 0.5
p/p0
p/Va(p0-p)
Fig. 7 BET plot of Pd-NP-AC catalyst
J Nanostruct Chem
123

In the spectra the sharp and narrow peaks at 2h=40°,
46.6°,68°,82°and 87°, which correspond to (111), (200),
(220), (311) and (222) crystalline planes of Pd, were
attributed to the presence of crystalline palladium and
indicating that palladium element exists in the form of
Pd(0). All diffraction peaks and positions for palladium
match well with those from the JCPDS card no. 05-0681.
The crystallite size of palladium nanoparticles was evalu-
ated using Scherrer equation for the (111) peak at 2h=40°
and was found to be 15 nm in size. The assignments are
concordant with the Sarioglan [23], Drelinkiewicz et al.
[24] and Zamani and Hossieni [25]. These crystalline
palladium peaks were well separated from the broad peak
of AC at around 2h=26°which corresponds to the peak
of graphite [26].
A TEM was used to obtain direct information about the
structure and morphology of the palladium nanoparticles.
Figure 3shows the TEM images of the Pd-NP-AC. The
mean diameter of palladium nanoparticles is about
10–45 nm with a mostly spherical shape.
Figure 4shows the chemical maps of the Pd-NP-AC
catalyst. It can be seen from the figure that the maps for
palladium and carbon clearly reveal their presence in the
structure of the catalyst. The amount of palladium (4.65%)
of Pd-NP-AC was determined by atomic absorption
analysis.
AC is a highly porous substance and has an extremely
large surface area. The SEM of the Pd-NP-AC catalyst
(Fig. 5) shows the porous characteristics of AC. To obtain
detailed information about the pore volume, pore size
distribution, and specific surface area, the N
2
adsorption
and desorption isotherms at 77 K are performed on the
samples (Fig. 6). BET indicated that surface area of the Pd-
NP-AC is 678 m
2
/g while total pore volume is 0.39 cm
3
/g
(Fig. 7). The average pore size diameter was calculated to
be 2.29 nm using BJH methods (Fig. 8).
Disproportionation of rosin involves dehydrogenation,
isomerisation and hydrogenation reactions of abietic-type
acids so that the mixture of acids evolves to a final com-
position that is more stable from a thermodynamical
viewpoint. The catalytic behavior of the Pd-NP-AC
nanoparticles was studied for disproportionation of gum
rosin and the progress of reaction was monitored by GC. In
the GC spectrums, the peak at 98.6 min was from AA and
the peak at 96.5 min was from DAA. The progress of
reaction is monitored as an increase in DAA peak and
decrease in AA peak. When the reaction was carried out
with 0.1% (w/w) of catalyst at 280 °C for 5 h, DPR was
obtained with a 72.4% yield. After evaluation of the cat-
alytic efficiency, the optimization of time and temperature
showed that the best result was obtained after 3 h at 280 °C
using 0.05% (w/w) of catalyst in nitrogen. Under this
condition, DPR was obtained with a 70% yield. A com-
parison with other reported efficient catalysts for the dis-
proportion of rosin demonstrated that our present catalytic
0
0.025
0.05
0.075
110100
rp/nm
dVp/drp
Fig. 8 BJH plot of Pd-NP-AC catalyst
Table 1 Comparison of different catalysts with our catalyst in the
disproportionation of rosin
Catalyst Wt% of catalyst AA% DAA% Reaction time
a
(h)
Pd-NP-AC 0.05 0.07 70 3
FeCl
3
135192
FeCl
3
–I
2
1 0.42 51 6
S–I
2
1 2 72 6
S 1 56 24 2
KI 1 11 50 3
Fe–LiI 1 4.3 45 6
Fe–I
3
1 22.44 30 5
a
They are the time it takes to reach maximum conversion. All
reactions were carried out at 280 °C
Table 2 Recyclability test of
Pd-NP-AC catalyst DAA% DAA% DAA%
1st run 2nd run 3rd run
70 70 68
0
20
40
60
80
100
120
140
160
180
200
11 21 31 41 51 61 71
2 Teta (degree)
Fig. 9 The XRD pattern of the recovered catalyst after the third run
J Nanostruct Chem
123

system exhibited a higher conversion and yield (see sup-
plementary material) (Table 1).
An important issue related to solid catalysts is
reusability. The reusability of the Pd-NP-AC catalyst was
also studied. To recycle the catalyst, the catalyst was fil-
tered from the reaction, washed with hot 2-propanol and
dried for the next cycle at 80 °C. The Pd-NP-AC catalyst
showed good stability for at least three runs in terms of
DAA% (Table 2). The XRD pattern of the recovered cat-
alyst after the 3rd run is shown in Fig. 9. In the spectra, the
sharp and narrow peaks at 2h=40°, 46.6°and 68°were
attributed to the presence of crystalline palladium [23–26].
Conclusions
In this paper, the catalytic disproportionation of Gum rosin
over palladium nanoparticles loaded on AC was investi-
gated. The catalyst was characterized by TEM, XRD, BET
and AAS. Compared with other reported efficient catalysts
in the literature, Pd-NP-AC is among the best catalysts for
the disproportion of rosin.
Acknowledgements We acknowledge Tarbiat Modares University,
Iran National Science Foundation (INSF) and Padideh Shimi Jam Co.
for support of this work.
Open Access This article is distributed under the terms of the
Creative Commons Attribution 4.0 International License (http://crea
tivecommons.org/licenses/by/4.0/), which permits unrestricted use,
distribution, and reproduction in any medium, provided you give
appropriate credit to the original author(s) and the source, provide a
link to the Creative Commons license, and indicate if changes were
made.
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