International Journal of Organic Chemistry, 2011, 1, 20-25
doi:10.4236/ijoc.2011.12004 Published Online June 2011 (http://www.SciRP.org/journal/ijoc)
Rapid Biodiesel Fuel Production Using Novel Fibrous
Catalyst Synthesized by Radiation-Induced Graft
Polymerization
Yuji Ueki1*, Nor Hasimah Mohamed2,3, Noriaki Seko1, Masao Tamada1,3
1Environment and Ind ustri al Materials Research Division, Quantum Beam Science Directorate,
Japan Atomic Energy Agency, Takasaki, Japan
2Radiation Processing Technology Division, Malaysian Nuclear Agency, Selangor, Malaysia
3Department of Chemistry and Chemical Biology, Graduate School of Engineering, Gunma University, Kiryu, Japan
Received March 30, 2011; revised April 25, 2011: accepted May 16, 2011
Abstract
An efficient fibrous catalyst for the biodiesel fuel production has been synthesized by radiation-induced graft
polymerization of 4-chloromethylstyrene onto a nonwoven polyethylene (NWPE) fabric followed by amina-
tion with trimethylamine (TMA) and further treatment with NaOH. The degree of grafting of NWPE fabric
and TMA group density of fibrous catalyst could easily and reproducibly be controlled within a range of up
to 340% and 3.6 mmol-TMA/g-catalyst, respectively. In the transesterification of triglycerides and ethanol
using the synthesized fibrous catalyst, the conversion ratio of triglycerides reached 95% after 4 h reaction at
50˚C.
Keywords: Biomass, Biodiesel Fuel, Triglycerides, Heterogeneous Catalysis, Radiation-Induced Graft
Polymerization, Renewable Resources
In order to deal with the future exhaustion of fossil fuels
and growing international energy demand, numerous
attempts to study and develop alternative fuels with re-
newability are underway in various parts of the world.
Among others, biodiesel fuel (BDF), which is defined as
the monoalkyl esters of fatty acids derived from triglyc-
erides (TGs) by transesterification with alcohols, has
been regarded as a promising alternative fuel over petro-
leum because of its qualities such as renewable resources
(plant and animal), lower kinetic viscosity, and decrease
in petrochemical dependence, green house effect and air
pollution. The BDF production be classified into several
methods according to the type of catalyst; acid- [1-3],
alkali- [1,4-6], lipase- [7,8], and metal oxide-catalyzed
method [9,10] and non-catalytic supercritical methanol
method [11-13]. Some methods of industrial production
of BDF from oil/fat have already been developed; and at
present, an alkali catalyst method of using a homogene-
ous catalyst such as NaOH or KOH is in the mainstream
due to faster reaction rates [1,4-6]. However, occurrence
of undesired saponification and difficulty on the separa-
tion of homogenized catalyst from the reaction mixture
are its weak points.
Recently, use of porous anion exchange resins was
proposed by N. Shibasaki-Kitakawa et al., as a modifica-
tion technique over the traditional alkali catalyst method
[14,15]. According to the method of using such a porous
anion exchange resin, the catalyst does not dissolve in
the reaction system, and therefore a step of separating the
catalyst is omitted. However, sample diffusion into the
pores of the catalyst is rate-limiting since the catalyst has
a reaction site inside the pores. Accordingly, the reaction
speed is slow; thus limiting its use in the mass-scale in-
dustrial production of BDF.
Meanwhile, our team has developed a grafted polymer
as an ion exchanger that secures high reaction speed and
enables high-speed processing [16-18]. The grafted
polymer was synthesized by a radiation-induced graft
polymerization that combined the surface of the polymer
substance (trunk polymer) with another polymer chain
(graft chain). Especially, our team has been intensively
studying about the grafted polymers with a substrate of a
fibrous polymer having a large specific surface area and
having a high-level contact efficiency, and it has found

Y. UEKI ET AL.21
that its adsorption rate was 10 - 100 times higher than
that of conventional granular resins with respect to the
metal absorption. Therefore, it is expected that this fea-
ture of the grafted fibrous polymer can lead to the
high-efficiency BDF production as in the case of the
metal adsorption. In the present paper, the applicability
of the grafted fibrous polymer to BDF production has
been investigated in lab-scale.
Fibrous catalyst for BDF production was synthesized
by combination of a pre-irradiation grafting method and
an emulsion graft polymerization technique, in a manner
similar to our previous paper [16-18]. Nonwoven poly-
ethylene (NWPE) fabric, of which the fiber diameter was
13 μm, was used as a trunk polymer for grafting. The
NWPE fabric was irradiated with an electron beam up to
100 kGy in nitrogen atmosphere at dry-ice temperature,
and the irradiated NWPE fabric was reacted with a
monomer emulsion, which was composed of 4-chloro
methylstyrene (CMS), polysorbate 20 (Tween 20) and
deionized water, in a deaerated glass ampoule for 4 h at
40˚C. The monomer emulsion was bubbled with nitrogen
gas to eliminate dissolved oxygen in the monomer emul-
sion, before using. After grafting, the grafted fabric was
treated with 0.5 M trimethylamine (TMA) at 50˚C to
introduce quaternary ammonium groups into the
CMS-graft chains, and then the resultant fabric was fur-
ther treated with 1 M NaOH to replace Cl– with OH–
before using. The degree of grafting (Dg) was defined by
the following equation;



100
Degree of grafting: Dg% /100WWW
where W0 and W1 are the dry weights of the NWPE fab-
ric before and after grafting, respectively. The TMA
group density of the resulting catalyst was estimated by
the analysis of their nitrogen content using elemental
analyzer.
As a result of trial and error, it was found that the
CMS-grafted NWPE fabric with enough Dg (over 100%)
to use as a catalyst precursor was synthesized when the
pre-irradiation dose was more than 20 kGy, the CMS
concentration was 3 wt%, and the weight ratio of CMS to
Tween 20 was 10 to 1, respectively. Under these opti-
mum grafting conditions, the grafted CMS chain onto
NWPE fabric could be easily and reproducibly controlled
within a range of up to 340% (5.1 mmol-CMS/g-fabric),
as shown in Figure 1. Furthermore, after detailed studies
of the amination of the CMS-grafted NWPE fabric, it
was also found that the amination was finished within 30
min, regardless of the Dg. The degree of amination
reached over 85%, and the TMA group densities were
2.7, 3.3 and 3.6 mmol-TMA/g-catalyst for the Dg of
100%, 200% and 300%, respectively. These TMA group
01234
0
100
200
300
400
Graft polymerization time [h]
Degree of grafting [
20 kGy
50 kGy
100 kGy
Figure 1. Effect of pre-irradiation dose on Dg onto
nion exchange resin (DIAION PA306S: 3.4 mmol-
aft chain and
TM
zed fibrous
ca
%]
of CMS
NWPE fabric.
a
TMA/g-resin, particle size: 150 - 425 μm), which was
purchased from Mitsubishi Chemical Co.
To confirm the introduction of CMS-gr
A groups onto the NWPE fabric, the individual
chemical structures of the NWPE fabric, CMS-grafted
fabric and fibrous catalyst were examined using an ATR-
FTIR spectrometer. After grafting, the CMS-grafted fab-
ric shows new characteristic peaks; the peaks at 1264,
816 and 670 cm–1 were ascribed to C-Cl stretching vibra-
tion of a chloromethyl group [19,20] and the peaks at
1611, 1511 and 1421 cm–1 were ascribed to aromatic ring.
The intensity of the CMS-derived bands gradually in-
creased with the increase in graft polymerization time,
indicating that more CMS were introduced onto the sur-
face of the NWPE fabric; that is, the CMS-grafted chain
grew longer with time. After amination, new characteris-
tic peaks at 1485 and 1222 cm–1, that were attributed to
quaternary ammonium cations [21,22] and symmetric
C-N stretching vibration [23], appeared in spectrum of
the fibrous catalyst, and yet at the same time the strong
peaks derived from C-Cl bond disappeared.
The catalytic performance of the synthesi
talyst was evaluated through the transesterification of
triolein (purity: 60%) and ethanol, and the transesterifi-
cation test was conducted in batch mode. The transesteri-
fication was performed by adding the pretreated fibrous
catalyst with NaOH (catalyst weight: 0.5 g, TMA group
density: 3.5 mmol-TMA/g-catalyst) in a homogenous
reaction solution (triolein: 2.8 g, ethanol: 7.2 g, decane as
a cosolvent: 10.0 g) at 50˚C. The TGs and BDF concen-
tration in the reaction solution were measured by using
high performance liquid chromatography system, in a
similar manner to the method described by M. Holčapek,
et al. [24]. As shown in Figure 2, the TGs, of which the
chromatographic peaks appeared at 21 - 24 min, were
consumed with the lapse of reaction time, and on the
other hand the BDF, of which the chromatographic peaks
appeared at 11 - 14 min, were gradually produced. These
results confirm that the synthesized fibrous material
functions as a catalyst for BDF production. The conver- densities are comparable to that of commercial granular

Y. UEKI ET AL. 22
B
igure 2. BDF production using the fibrous catalyadiation-induced graft polymerization. Sample: BDF
sion ratio of TGs in different reaction times reached 23%,
48%, 70%, 82%, and 95% at 10 min, 30 min, 1 h, 2 h,
and 4 h, respectively. TGs in Figure 2 are specifically
noted; and the conversion ratio of TGs relative to the reac-
tion time is plotted as Figure 3 where the data with
DIAION PA306S are also included for comparison. The
fibrous catalyst promoted the transesterification at a reac-
tion speed higher by at least 3 times than that with the
granular resin. This is because the fibrous catalyst com-
prised fibers with specific shape. It is noteworthy that
conversion ratio of TGs in a reaction time of 2 h was 82%
with the fibrous catalyst and 26% with the granular resin.
In addition, the influence of the type of alcohol on
DF production was investigated. In this experiment,
primary alcohols having different alkyl chain lengths,
such as methanol, ethanol, 1-propanol, 1-butanol, 1-pen-
tanol and 1-hexanol, were used; and the transesterifica-
tion time was held constant at 2 h. The other conditions
were the same as in Figure 2. As in Figure 4, BDF was
produced irrespective of the types of alcohol used, and it
was found that the synthesized fibrous catalyst could be
applicable to the transesterification of TGs with other
various types of alcohols as well as ethanol. From the
peaks of BDF in Figure 4, it was demonstrated a ten-
dency that the alcohol having a longer alkyl chain length
took a longer retention time. These differences in the re-
tention time of each BDF represent the differences in the
structure (hydrophobicity) of the produced BDF, and it
was also found that different types of BDF could be pro-
duced from different types of alcohol. The conversion
(B) After 10 min
(C) After 30 min
(D) After 1 h
(E) After 2 h
(F) After 4 h
TGs
BDF
1.0 Abs.
(A) Before reaction
1.0 Abs.
1.0 Abs.
1.0 Abs.
1.0 Abs.
1.0 Abs.
0 5 10 15 20 25
Retention time [min]
Fst synthesized by r
solution (10 times dilution); injection volume: 5.0 μL; column: octadecyl bonded column (column size: 2.1 mm i.d. × 150 mm
long, particle size: 5 μm); mobile phase: (A): water, (B): acetonitrile, (C): 2-propanol–hexane (5:4, v/v); flow rate: 0.5 mL/min;
linear gradient: 30%A + 70%B (0 min) → 100%B (10 min) → 50%B + 50%C (20 min) → 50%B + 50%C (25 min); column
temperature: 40˚C; detection: UV absorption at 205 nm.

Y. UEKI ET AL.23
01234
0
20
40
60
80
100
%]
Transesterification time [h]
Conversion ratio of TGs [
Granular resin
Fibrous catalyst
Figure 3. Comparison of catalytic performance of fibrous
tio of TGs in transesterification with different alcohols
land 1-butanol due to steric hindrance. On the other hand,
for BDF production
ca
Figure 4. BDF l chain lengths.
catalyst and granular resin for BDF production.
ra
after the reaction time of 2 h was 48% with methanol,
82% with ethanol, 82% with 1-propanol, 89% with
1-butanol, 53% with 1-pentanol and 44% with 1-hexanol,
respectively. The conversion ratio of 1-pentanol and
1-hexanol became lower than that of ethanol, 1-propano-
for short-chain alcohol like methanol, phase separation
occurred before and after experiment, even if the cosol-
vent such as decane was added to uniformize the reaction
solution. As a result, the conversion ratio of methanol was
lower than that of ethanol, although the alkyl chain length
of methanol was shorter. This phase separation might be
attributed to the immiscibility between the TGs and
methanol. To increase the miscibility of the two com-
pounds, Tang et al. suggested that higher pressure and
higher temperature are needed [25].
In conclusion, the fibrous catalyst
n be synthesized by radiation-induced graft polymeri-
zation, and it can produce BDF with faster and higher
efficiency. This new kind of catalyst demonstrates strong
potential in the acceleration of BDF production by offer-
ing and easy, efficient and reliable technique which
eventually contributes on solving the current environ-
mental issues.
TGs
(A) Before reaction
y TGs) BDF
(B) Methanol
(C) Ethanol
(D) 1-Propanol
(E) 1-Butanol
(F) 1-Pentanol
(G) 1-Hexanol
production using the different alcohols having different alky
Retention time [mim]
types of the primary
(Onl
0.5 Abs.
. . . . . . 0.5 Abs0.5 Abs0.5 Abs0.5 Abs0.2 Abs0.2 Abs
05 10 15 20 25
0 5 10 15 20 25

Y. UEKI ET AL. 24
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