Rapid Biodiesel Fuel Production Using Novel Fibrous Catalyst Synthesized by Radiation-Induced Graft Polymerization

doi:10.4236/ijoc.2011.12004

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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

E-mail: [email protected]

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

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

zed fibrous

of CMS

NWPE fabric.

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.

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

(D) After 1 h

(E) After 2 h

(F) After 4 h

TGs

BDF

1.0 Abs.

(A) Before reaction

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

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

Figure 4. BDF l chain lengths.

catalyst and granular resin for BDF production.

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

(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.

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