Poly (styrene-co-divinylbenzene) amine functionalized polymer supported ruthenium nanoparticles catalyst active in hydrogenation of xylose

Article abstract of DOI:10.1016/j.catcom.2013.07.002

Poly (styrene-co-divinylbenzene) amine functionalized polymer supported ruthenium nanoparticles catalyst is evaluated first time in selective hydrogenation of xylose to xylitol. The catalyst Ru/PSN is characterized by different techniques such as X-ray powder diffraction, transmission electron microscopy and CO chemisorption. To develop our understanding for the activity of catalyst Ru/PSN, xylose hydrogenation experiments were carried out using catalyst of Ru/PSN with different ruthenium loading (from 1.0% to 3.0%), at different temperatures (from 100 to 140 C) and hydrogen pressures (from 30 to 55 bar). For deactivation test, the catalyst of Ru/PSN recovered from the product solution was reused up to the four times.

Full text of DOI:10.1016/j.catcom.2013.07.002

Catalysis Communications 41 (2013) 52–55
Contents lists available at SciVerse ScienceDirect
Catalysis Communications
journal homepage: www.elsevier.com/locate/catcom
Short Communication
Poly (styrene-co-divinylbenzene) amine functionalized polymer
supported ruthenium nanoparticles catalyst active in hydrogenation
of xylose
Dinesh Kumar Mishra, Aasif Asharaf Dabbawala, Jin- Soo Hwang ⁎
Bio-refinery Research Center, Korea Research Institute of Chemical Technology (KRICT), Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 6 May 2013
Received in revised form 27 June 2013
Accepted 1 July 2013
Available online 8 July 2013
Poly (styrene-co-divinylbenzene) amine functionalized polymer supported ruthenium nanoparticles catalyst is
evaluated first time in selective hydrogenation of xylose to xylitol. The catalyst Ru/PSN is characterized by
different techniques such as X-ray powder diffraction, transmission electron microscopy and CO chemisorption.
To develop our understanding for the activity of catalyst Ru/PSN, xylose hydrogenation experiments were carried
out using catalyst of Ru/PSN with different ruthenium loading (from 1.0% to 3.0%), at different temperatures
(
from 100 to 140 °C) and hydrogen pressures (from 30 to 55 bar). For deactivation test, the catalyst of Ru/PSN
Keywords:
Hydrogenation
Xylose
recovered from the product solution was reused up to the four times.
© 2013 Elsevier B.V. All rights reserved.
Xylitol
Ruthenium nanoparticles
Polymer
1
. Introduction
production, less sensitive to the deactivation and recyclable. It was
found that activated carbon supported ruthenium catalyst highly ac-
tive than Ni metal was capable to replace conventional nickel cata-
lysts for the hydrogenation of xylose to xylitol [20]. Recently, our
Catalytic hydrogenation of xylose has widely been studied and
used to produce xylitol, one of the top twelve platform molecules
and building block molecules [1–3] that can further be transformed
into a variety of chemicals [4–6]. Xylitol, a pentose sugar alcohol, is
also known to be a best sweetener similar to sucrose, nearly twice
that of sorbitol and approximately three times that of mannitol,
occurs in a small amount in nature [7–10]. Xylitol has some other
interesting properties such as anti-carcinogenic, sugar substitute
and higher sweetening capacity than different alcohols. It has wide
range of applications in food, pharmaceutical, cosmetic, and synthetic
resin industries [11–13].
Over the last few decades, the hydrogenation of xylose was carried
out in three phase slurry reactor using Raney nickel catalyst, and later
using nickel metal supported catalysts [14,15]. During hydrogenation
experiments of xylose, it was seen that the formation of by products
and accumulation of organic impurities on the catalyst surface easily
deactivated nickel catalyst due to the poisoning of the active sites
and also led to metal leaching-off by the morphological changes
take place on the metal surface [16–19]. To overcome these problems,
research was continued in search for proper metals and support ma-
terials combination catalyst systems for the hydrogenation of xylose
that can lead to high activity and selectivity towards xylitol
research group spotlighted on
a catalyst of ruthenium and
NiO-modified TiO support is active and highly selective to the main
2
product, xylitol [21].
Even though a number of catalysts based on ruthenium and inorgan-
ic metal oxide supports as such or their modified forms are used and
active for catalytic hydrogenation of xylose to xylitol, there have been
no reports in the literatures so far on use of polymer supported
ruthenium catalyst. In this study, preparation method of hitherto
unreported poly (styrene-co-divinylbenzene) amine functionalized
(PSN) polymer supported ruthenium nanoparticles catalyst is described.
The results obtained from xylose hydrogenation experiments using cata-
lyst Ru/PSN are discussed.
2. Experimental section
2.1. Materials
3 2
Ruthenium trichloride (RuCl .3H O) was supplied by Strem
Chemicals, USA. Granules of poly (styrene-co-divinylbenzene)
amine functionalized (PSN) polymer, xylose and sodium borohydride
(
4
NaBH ) were purchased from Sigma-Aldrich Chemicals, USA. Ethanol
⁎
Corresponding author. Tel.: +82 42 860 7382; fax: +82 42 860 7676.
E-mail address: jshwang@krict.re.kr (J.-S. Hwang).
was purchased from Sigma-Aldrich Chemicals, USA and used as solvent.
1566-7367/$ – see front matter © 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.catcom.2013.07.002

D.K. Mishra et al. / Catalysis Communications 41 (2013) 52–55
53
All the chemicals were used as such without further purification.
Hydrogen gases (99.9%) used was from Deokyang Co. Ltd.
5.0RuPSN
3
1
.0RuPSN
.0RuPSN
PSN
2
.2. Preparation of PSN supported ruthenium nanoparticles catalyst
PSN supported Ru nanoparticles catalysts were prepared by im-
pregnation method. Granules of poly (styrene-co-divinylbenzene)
amine functionalized (PSN) polymer were crushed until the fine
powders were formed. The fine powders of PSN were then impreg-
nated into RuCl
was stirred under N
NaBH solution prepared in ethanol was added drop wise to resultant
mixture with constant stirring and entire reaction mass was stirred
500 rpm) at room temperature. Finally, catalyst Ru/PSN was separated
3
.3H
2
O solution prepared in ethanol. The mixture
2
atmosphere for a period of 24 h. For reduction,
4
(
by filtration, washed with ethanol and dried to give dark black. The
catalysts with different ruthenium contents, 1.0Ru/PSN and 3.0Ru/PSN,
1
0
20
30
40
50
60
70
80
2
theta/degree
were also prepared by varying the amount of RuCl
.3. Catalyst characterization
Powder X-ray diffraction patterns of all samples were obtained by a
3 2
.3H O.
Fig. 1. XRD patterns of PSN and its corresponding catalysts.
2
1.0Ru/PSN, 3.0Ru/PSN and 5.0Ru/PSN. No diffraction peaks of ruthenium
metal appeared in the XRD patterns of the catalysts (1.0Ru/PSN, 3.0Ru/
PSN and 5.0Ru/PSN). These indicate that ruthenium nanoparticles were
highly dispersed on PSN support during the catalyst preparation.
However, CO chemisorption results of 5.0Ru/PSN showed that the disper-
sion of ruthenium nanoparticles and metallic surface area were 24 % and
Rigaku diffractometer (D/MAX IIIB, 2 kW) using Ni-filtered Cu Kα-
radiation (40 kV, 30 mA, λ = 1.5406 Å) and a graphite crystal mono-
chromator. FT-IR spectra were recorded using KBr pellet on a Nicolet
Magna-560 IR spectrophotometer. Surface area measurements were
carried out using Micromeritics, Tristar II analyzer. The samples were
−
2
2
activated at 250 °C for 4 h under vacuum (5 × 10 mmHg) prior to
adsorption measurements. The specific surface areas, pore diameters,
87.8 m /gmetal, respectively.
N
2
TEM image of 5.0Ru/PSN is given in Fig. 2. It can be seen clearly
that the ruthenium particles with average size of 2.5 nm are homoge-
neously distributed on the surface of PSN support which is responsi-
ble for efficient xylose hydrogenation.
FT-IR spectra (as shown in Fig. S1) of samples without reduction
confirmed that ruthenium chloride was strongly sorbed on PSN sup-
port. The sorption behaviour was also confirmed from the SEM im-
ages. On comparing the images (PSN1 and PSN 2), it can be seen
that morphology of PSN is different from that of catalyst, 5.0 Ru/PSN
(as shown in Fig. S2). In TGA analysis (Fig. S3), the curves of PSN and
its corresponding catalysts are identical. That's why the PSN could be
used as support material due to its high thermal stability. As expected,
and pore volumes of the samples were calculated from nitrogen adsorp-
tion isotherms measured at 77 K as per Brunauer, Emmett, Teller (BET)
method. Scanning electron microscopy (SEM) images of support and
catalyst were seen on SEM, JEOL JSM-840 A. Transmission electron
microscope (TEM) images were taken with a Maker FEI, Model Technai
G2 microscope with acceleration voltage of 200 kV using carbon
coated 200 mesh copper grids. Thermogravimetric analyses (TGA)
were performed using TA instrument model, TGA Q500 V6.7 with
2
heating rate of 10 °C/min in N atmosphere. CO chemisorption was
carried out by using an instrument model ASAP 2020C V1.09 G. The
metal contents, ruthenium catalyst in product solution obtained after
xylose hydrogenation, were determined by inductively coupled plasma
mass spectrometry (ICP-MS).
2
the BET surface area of 5.0Ru/PSN (812.91 m /g) which is comparatively
less than that of PSN i.e. 1165.97 m /g. This remarkable change in surface
2
area value might be due to the pore blockage by ruthenium metals as
strong active sites on the surface of PSN support.
2
.4. Catalytic hydrogenation of xylose to xylitol
Ruthenium leaching was estimated by the analysis of product solu-
tion for the catalyst of 5.0Ru/PSN and the result is summarized in
Table S1. It has been found that ruthenium metal could not be detected,
and there is no ruthenium leached into the product solution after
filtration.
2
Hydrogenation experiments of xylose (20 wt.% in 200 ml of H O)
were carried out batch wise in 300 mL of three phase slurry reactor
in the temperature range from 80 to 120 °C at hydrogen pressure
(
40–65 bar) at constant stirring rate (1200 rpm). In a typical hydrogena-
tion experiment, required amount of catalyst Ru/PSN and 200 ml of xy-
lose solution were charged into stainless steel autoclave reactor. The
reactor was fitted air tight and flushed with nitrogen gas three times at
room temperature. Then, reactor was brought to desired temperature
and pressurized with hydrogen which was considered as the zero reac-
tion time. Hydrogenation reaction was initiated by stirring the entire re-
action mass. During hydrogenation at different time intervals, the
product components were analyzed using a HPLC (Younglin Instrument,
Acme 9000) equipped with refractive index (RI) detector and Sugar-Pak
column [21].
3
. Results and discussion
3
.1. Characterization
Fig. 1 represents the XRD patterns of PSN, 1.0RuPSN, 3.0RuPSN,
and 5.0RuPSN. It can be seen that the XRD pattern of PSN support
looks alike to its corresponding PSN supported ruthenium catalysts,
Fig. 2. TEM view of 5.0Ru/PNS.

54
D.K. Mishra et al. / Catalysis Communications 41 (2013) 52–55
6
3
.2. Catalytic hydrogenation of xylose to xylitol
The catalyst performance of synthesized 5.0Ru/PSN was evaluated in
xylose hydrogenation using water as a green solvent. The catalytic hy-
drogenation of xylose gives mainly xylitol. However, formation of sev-
eral by-products were also observed (supporting information, scheme
S1). Therefore, the studies have been focused on selectivity issues and
product distribution using Ru catalyst. Initially, we performed the few
preliminary experiments by varying the stirring speed from 400 to
E = 26.5KJ/mol
a
5
4
3
1
200 rpm (400, 800, 1000 and 1200 rpm) under similar reaction condi-
tions to check the influence of gas-liquid mass transfer resistance. The
hydrogenation experiments performed at 400–800 rpm had compara-
tively lower conversion and gave somewhat lower xylitol selectivity
indicating gas-liquid mass transfer limitations in this range. A further
increase in stirring rate from 1000 to 1200 rpm, no significant changes
in conversion and selectivity were observed. Thus, the stirring rate was
fixed at 1200 rpm in all of hydrogenation experiments to avoid the gas
liquid mass transfer limitation.
2.5
2.6
2.7
2.8
2.9
-3
(
1/T) x 10 , K
The effect of reaction temperature on xylose conversion and yield
of xylitol was clear. An increased hydrogenation temperature clearly
improved the reaction rate at the experiments between 80 and
Fig. 4. Arrhenius plots of the initial rates for the xylose hydrogenation.
1
20 °C (Fig. S4a). The yield of xylitol was also affected by changing
activated H. Finally, the carbonyl group in xylose reacted with the acti-
vated H on the surface of catalyst to produce xylitol.
the hydrogenation temperature from 80 to 120 °C (Fig. S4b). During
xylose hydrogenation experiments at different temperatures, it was
observed selectivity to xylitol was decreased as expected continuous-
ly on increasing temperature from 80 to 120 °C. It is attributed to the
formation of other by-products such as arabitol, furfural and etc dur-
ing hydrogenation of xylose [22,23].
The effect of catalyst amount was studied by hydrogenating xylose
(
1
20 wt.%) solution using different amount of catalyst (1.0, 1.25 and
.5 g) and the results are given in Table 1. As expected, xylose conver-
sion and yield of xylitol increased continuously on increasing the
amount of catalyst from 1.0 to 1.5 g. The selectivity to xylitol increased
up to the certain limit and thereafter it decreased on further increasing
catalyst amount from 1.25 to 1.5 g. It is stated that the catalyst amount
i.e. 1.25 g, is found to be sufficient for highest xylose conversion and
selectivity to xylitol. The catalytic activity and selectivity of the
Time versus xylose concentration data using [Ci] =20 wt% is
given in Table S2. Plot of final xylose concentration (C
versus time for zero and second- order, respectively, are nonlinear
as shown in Figs. S5 and S6, while plot of LN(C /C ) versus time is lin-
ear as shown in Fig. 3. This proves that the reaction xylose hydrogena-
tion follows the first- order in nature.
It was found that the activation energy calculated from Arrhenius
equation or a plot of rate constant (as shown in Table S3) LN(k) ver-
sus 1/T, K as shown in Fig. 4, is 26.5 KJ mol . This value of activation
energy is very close to the values reported earlier in the literatures
f f
) and (1/(C )
i
f
5
Ru/PSN was also compared with 5Ru/C (5% Ru supported on carbon),
the experiment was carried out with catalyst 5Ru/C under similar reac-
tion conditions (Temp 120 °C, 5.5 MPa hydrogen pressure). From the
results of 5Ru/C, it can be seen that 5Ru/PSN exhibited similar catalyst
activity to Ru/C however, the xylitol yield was less compared to our
−
1
2
previously reported catalyst systems, Ru/NiO/TiO and Ru/HY Zeolite
[
18].
An increased hydrogen pressure had positive effect on reaction rate
Fig. S7a) and yield of xylitol (Fig. S7b). The selectivity to xylitol was
improved continuously on increasing the hydrogen pressure from 40
to 65 bar. Xylose hydrogenation proceeds through H dissolution, H
adsorption on the active centers of the catalyst, to produce
[21,22].
(
3.3. Reuse of the catalyst
2
2
diffusion, H
2
The reusability of the catalyst is of great importance for industri-
al application, therefore tests of Ru/PSN catalyst were also carried
out in hydrogenation of xylose and the results are presented in
Fig. 5. The catalyst wt% on xylose concentration was kept constant
i.e. 3.03 wt%. The results demonstrated that the activity of the
catalyst was decreased slightly in the four successive catalytic cycles
but not significantly indicating that the Ru/PSN catalyst may possess
long-term stability. From the TEM images of fresh catalyst and that of
catalyst after four cycles given in Fig. S8, change in the morphology of
the catalyst was not observed considerably.
1
0
0
0
.2
.9
.6
.3
0
o
120 C
o
1
00 C
Table 1
a
Effect of catalyst (5.0RuPSN) amount on xylose hydrogenation .
8
0oC
Entry
Catalyst amount
g)
Conv.
Sel.
Yield
(
xylose
Xylitol
Xylitol
1
2
3
4
0.00
1.00
1.25
1.50
–
–
–
85.9
97.2
99.8
91.9
95.8
94.1
79.0
93.1
93.9
0
20
40
60
80
100
Hydrogenation time, min.
[
a] Reaction conditions: Substrate (xylose) = 20 wt%,Temp. = 120 °C, Pressure
Fig. 3. Test for first order of reaction.
2
(H ) = 55 bar, Stir. Speed = 1200 rpm and Reaction time = 120 min.

D.K. Mishra et al. / Catalysis Communications 41 (2013) 52–55
55
Conv
Appendix A. Supplementary data
100
Sel.
Yield
Electronic supplementary information (ESI) is available: Analysis
results of FT-IR, SEM and TGA are described. Supplementary data to
this article can be found online at http://dx.doi.org/10.1016/j.
catcom.2013.07.002.
9
8
7
6
5
0
0
0
0
0
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