Natural Science, 2009, 1, 55-62 NS
http://dx.doi.org/10.4236/ns.2009.11010
Synthesis of biodiesel from Jatropha curcas L. seed oil
using artificial zeolites loaded with CH3COOK as a
heterogeneous catalyst
Wei Xue1, You-Chun Zhou1, Bao-An Song1, Xia Shi1, Jun Wang1, Shi-Tao Yin1, De-Yu Hu1,
Lin-Hong Jin1, Song Yang1,*
1Key Laboratory of Green Pesticide and Bioengineering, Ministry of Education of China, Center for Research and Development of
Fine Chemicals, Guizhou University, Guiyang 550025, P. R. China; To whom correspondence should be addressed: Tel.: +86-851-
362-0521, Fax: [phone].
Received 18 May 2009; revised 30 May 2009; accepted 10 June 2009.
ABSTRACT
An environmentally benign process was devel-
oped for the transesterification of Jatropha
curcas L. seed oil with methanol using artificial
zeolites loaded with potassium acetate as a
heterogeneous catalyst. After calcination for 5 h
at 823 K, the catalyst loaded with 47 wt.%
CH3COOK exhibited the highest efficiency and
best catalytic activity. The easily prepared cata-
lysts were characterized by means of X-ray dif-
fraction and IR spectroscopy, as well as
Hammett indicator titration. The results revealed
a strong dependence of catalytic activity on ba-
sicity. The optimum reaction conditions for
transesterification of J. curcas oil were also in-
vestigated. The methyl ester content in the bio-
diesel product exceeded 91% after 4h reaction
at reflux temperature in the presence of 2%
solid catalyst and no water washing process is
needed during workup.
Keywords: Biodiesel; Heterogeneous Catalyst;
Artificial Zeolites; Jatropha Curcas L. seed Oil
1. INTRODUCTION
Biodiesel is a biodegradable and non-toxic renewable
alternative to diesel fuel that is composed of mono-alkyl
esters of long-chain fatty acids derived from vegetable
oils or animal fats. Biodiesel is increasing in importance
because of its benign impact on the environment. [1,2]
Biodiesel is produced mainly through the transesterifica-
tion of vegetable oils using short-chain alcohols, typi-
cally methanol or ethanol [3], because these are cheap
and readily available from syngas, in which methanol is
usually preferred. [4,5] Transesterification of vegetable
oils with methanol, also called methanolysis, is typically
carried out in the presence of homogeneous base or acid
catalysts. Homogeneous base catalysts, including potas-
sium hydroxide, sodium hydroxide and potassium and
sodium alkoxides, such as NaOCH3 [1], have higher
catalytic activity than acid catalysts. Furthermore, since
acid catalysts are more corrosive than base catalysts,
base catalysis is usually preferred in commercial proc-
esses. [6] In the conventional homogeneous reaction,
removal of the base after reaction is a major problem,
since aqueous quenching results in the formation of sta-
ble emulsions and saponification, making the separation
of methyl esters difficult and producing waste water. [7]
However, the use of solid base catalysts can not only
overcome those disadvantages, but also confer some
advantages, such as the elimination of a quenching step
(and associated contaminated water waste) during the
work-up process and the scope to operate in continuous
mode. [8,9] Therefore, environmentally friendly hetero-
geneous catalysts are promising for biodiesel production
because of environmental constraints and potential sim-
plification of existing processes.
Recently, heterogeneous catalysts used to catalyze the
transesterification of vegetable oils to prepare fatty acid
methyl esters (FAME) have attracted considerable atten-
tion. Wilson et al. [5] prepared a series of Li-promoted
CaO catalysts with Li loading in the range 0.26-4.0
wt.% to catalyze the transesterification of glyceryl
tributyrate and methanol. They found that the optimum
loading correlated with the formation of an elec-
tron-deficient surface Li+ species and associated-OH
species at defect sites on the support. Lee et al. [10] re-
ported a process for the production of biodiesel from
vegetable oils using an Na/NaOH/γ-Al2O3 heterogene-
ous catalyst. Under optimized reaction conditions, this
Na/NaOH/γ-Al2O3 heterogeneous base catalyst showed
almost the same activity as a conventional homogeneous
NaOH catalyst. However, the base catalyst had to be

56 W. Xue et al. / Natural Science 1 (2009) 55-62
prepared in special apparatus equipped with a nitrogen
flow line and cold circulating water flow. These disad-
vantages restrict potential industrial applications. Xie et
al. [11] developed a type of Al2O3-loaded KNO3 solid
base catalyst for the transesterification of soybean oil.
The catalytic activity was ascribed to the presence of
K2O and K-O-Al groups derived from KNO3 or other
potassium compounds during high-temperature calcina-
tion.
Zeolites have attracted much attention in the prepara-
tion of solid base catalysts. [12,13,14,15] The basicity
and catalytic activity of these zeolites can be modulated
through ion exchange of alkali and the occlusion of al-
kali metal oxides in zeolite cages by decomposition.
However, the preparation procedures for these modified
zeolites have some disadvantages. For ion-exchanged
zeolites, the exchanged samples need to be washed with
distilled, deionized water to remove excess alkali re-
maining in the ETS-10 zeolite cages. [13] Furthermore,
the treatment process requires a long time and produces
much waste water.
In the present study, a modified artificial zeolite for
catalysis of the transesterification of Jatropha curcas L.
seed oil was developed using a simple preparation proc-
ess. This catalyst preparation technique has many ad-
vantages: (1) compared with ETS-10 and NaX zeolites,
artificial zeolites are cheaper; (2) artificial zeolites are
used directly as a support without any pretreatment; and
(3) after impregnation with potassium acetate, artificial
zeolite samples were dried and then simply calcined in a
muffle furnace. Unlike NaX occluded catalysts, [13,14]
artificial zeolite-supported potassium acetate was ther-
mally decomposed in an uncontrolled manner and the
catalyst sample was prepared easily. To the best of our
knowledge, this is the first time that a catalyst of artifi-
cial zeolites loaded with CH3COOK has been adopted
for biodiesel production from J. curcas oil, a plant be-
longing to the Euphorbiaceae family with seed oil that is
non-edible and a good material for industrial biodiesel
production. [16] After calcination for 5 h at 823 K, the
artificial zeolite catalyst loaded with 47 wt.%
CH3COOK exhibited the highest basicity and the best
catalytic activity for the reaction. The catalytic activity
was evaluated in terms of the methyl ester content of the
product after transesterification of J. curcas oil. The op-
timum reaction conditions were determined using an
orthogonal experimental method.
2. EXPERIMENTAL
2.1. Catalyst Preparation
Artificial zeolites (Na2OAl2O3xSiO2yH2O) were ob-
tained from Shanghai Qingxi Chemical Science and
Technology Ltd. (Shanghai, China). CH3COOK/artificial
zeolite supported catalysts were prepared by impregnat-
ing artificial zeolites with an aqueous solution of potas-
sium acetate. Samples with various CH3COOK loadings
were impregnated for 12 h to ensure that the CH3COOK
diffused and dispersed thoroughly over the surface and
through the pores of the artificial zeolites. The samples
were then dried overnight at 383 K and calcined (typi-
cally at 823 K) in air for 5 h to yield readily usable cata-
lysts. In experiments, catalyst samples with loading
amounts of 9,23,33,41,44,47 and 50 wt.% (relative to the
total mass of the catalyst before calcination) were des-
ignated as 9%, 23%, 33%, 41%, 44%, 47% and 50%
CH3COOK/artificial zeolites, respectively. [11]
2.2. Catalyst Characterization
The basic strength (H_) of the solid base was assessed
using Hammett indicators. [17,18,19] In our experiments,
the following Hammett indicators were used: bromthy-
mol blue (H_=7.2), phenolphthalein (H_=9.8), 2, 4-di-
nitroa-niline (H_=15.0), and nitroaniline (H_=18.4).
Approximately 50 mg of the catalyst sample was shaken
with 10 mL of anhydrous ethanolic solution of Hammett
indicator and left to equilibrate for 2 h. [20] Then the
color change of the solution was observed. When the
solution exhibits a color change, this indicates that the
basic strength of the catalyst is stronger than the indica-
tor used. However, when the solution produces no color
change, the basic strength of the catalyst is weaker than
that of the indicator used. The basicity of the catalysts
was determined by titration with a Hammett indicator
and a 0.02 mol/L anhydrous ethanolic solution of ben-
zene carboxylic acid. [6] It should be noted that
Hammett indicator titration can only give qualitative
information about the basic properties of catalysts.
X-Ray diffraction (XRD) patterns of the samples were
recorded on a Rigaku D/MAX-2200 powder X-ray dif-
fractometer with Cu K (λ=0.154nm) radiation using an
acceleration voltage of 40 kV and a current of 30mA,
over a 2
 range of 0-65° with a step size of 0.04° at a
scanning speed of 3°/min. The data were processed us-
ing DiffracPlus software. The phases were identified
using the Power Diffraction File (PDF) database (JCPDS,
International Center for Diffraction Data).
IR spectra of the samples were measured using the
KBr pellet technique. Spectra were recorded on a Shi-
madzu IR-Prestige-21 spectrometer with resolution of 4
cm–1 over the range 400-4000cm–1.
2.3. Transesterification Reaction
Jatropha curcas oil was prepared by squeezing seeds of J.
curcas from Luodian county, Guizhou Province, south-
west China. The crude oil obtained was then further pu-
rified by filtering out solid impurities and refined to re-
duce the water content. According to gas chromatogra-
phy (GC) analysis, the fatty acids of J. curcas oil con-
sisted of: palmitic acid (12.47%), palmitoleic acid
(2.10%), stearic acid (6.42%), oleic acid (32.04%), and

W. Xue et al. / Natural Science 1 (2009) 55-62 57
linoleic acid (42.47%). The acid value of the oil was
approximately 2.63mg KOH/g, and an average molecu-
lar weight of 880g/mol was calculated from the saponi-
fication value (Sv=194mg KOH/g).
A 250-mL three-necked glass flask equipped with a
water-cooled condenser, thermometer and magnetic
stirrer was charged with 110.0g (125mmol, calculated
from the average molecular weight) of J. curcas oil,
different volumes of methanol and various amounts of
catalyst. The mixture was vigorously stirred and re-
fluxed for the required reaction time. After completion
of methanolysis, the mixture was filtered and excess
methanol was recovered by rotary evaporation. The
liquid phase was transferred into a separatory funnel
and allowed to settle; the upper layer, the biodiesel
product, was analyzed by GC.
2.4. Analysis Methods
The external standard method was adopted for GC product
analysis. An Agilent 6890GC instrument equipped with a
flame ionization detector was used. The chromatographic
conditions were as follows: column, HP-Innowax (30m×
0.32mm, 0.25m); inlet temperature, 523K; detector tem-
perature, 523K; split ratio, 20:1; oven temperature program,
463K for 3min, ramp at 15K/min to 513K, hold for 8min;
injection volume, 1L; carrier gas, N2 at 1.0mL/min; air
flow, 450mL/min; H2 flow, 40mL/min.
3. RESULTS AND DISCUSSION
3.1. Basic Strength of the Catalyst
Table 1 shows the basic strength of the parent artificial
zeolite (entry 1) and various CH3COOK/artificial zeolite
catalysts calcined at different temperatures. The basic
strength of catalyst samples with CH3COOK loading of
＜33wt.% and calcined at 823 K are in the range 7.2<H_
＜9.8 (entries 2-4). The basic strength increased to 15.0＜
H_＜18.4 when the CH3COOK loading exceeded 33 wt.%
(entries 5-＜9). This indicates that there are at least two
types of active base sites in the supported catalysts.
For loading of <33wt.%, the amount of CH3COOK is
not enough to cover all of the support surface and in-
corporation of potassium ions into the vacancies of the
support is mainly through strong salt-support or oxide-
support interaction. [20] New active base species emerge
when CH3COOK loading exceeds 33wt.%, indicating
that (CH3COOK)n -support interaction plays an impor-
tant role in this process. However, the basic strength of
47 wt.% CH3COOK/artificial zeolite calcined at a tem-
perature less than 623 K showed no increase compared
with the artificial zeolite (entries 1, 10, 11). This is likely
because CH3COOK loaded onto the artificial zeolite is
not decomposed at temperature less than 623 K. The
catalysts calcined between 623 and 973 K exhibit similar
basic strength (entries 12-15). According to the defini-
tion of Tanabe, [21] these catalyst samples, with base
strength in the range 15.0＜H_＜18.4, can be regarded
as strong bases.
3.2. Basicity of the Catalyst
Table 2 summarizes the basicity of a series of
CH3COOK/artificial zeolite catalysts calcined at differ-
ent temperatures, as determined using Hammett indica-
tors. As shown in Table 2, the basicity of catalysts cal-
cined at 823 K first increases and then decreases with the
increasing CH3COOK loading (entries 2-8), with 47
wt.% CH3COOK/artificial zeolite exhibiting the highest
Table 1. Basic strength of various CH3COOK/artificial zeolite catalysts calcined at different temperatures.
Entry Samples Calcination temperature (K) Basic strength (H_)
1 Artificial zeolite – 7.2＜H_＜9.8
2 Artificial zeolite 823 7.2＜H_＜9.8
3 9%CH3COOK/artificial zeolite 823 7.2＜H_＜9.8
4 23%CH3COOK/artificial zeolite 823 7.2＜H_＜9.8
5 33%CH3COOK/artificial zeolite 823 15.0＜H_＜18.4
6 41%CH3COOK/artificial zeolite 823 15.0＜H_＜18.4
7 44%CH3COOK/artificial zeolite 823 15.0＜H_＜18.4
8 47%CH3COOK/artificial zeolite 823 15.0＜H_＜18.4
9 50%CH3COOK/artificial zeolite 823 15.0＜H_＜18.4
10 47%CH3COOK/artificial zeolite – 7.2＜H_＜9.8
11 47%CH3COOK/artificial zeolite 523 7.2＜H_＜9.8
12 47%CH3COOK/artificial zeolite 623 15.0＜H_＜18.4
13 47%CH3COOK/artificial zeolite 723 15.0＜H_＜18.4
14 47%CH3COOK/artificial zeolite 923 15.0＜H_＜18.4
15 47%CH3COOK/artificial zeolite 973 15.0＜H_＜18.4

58 W. Xue et al. / Natural Science 1 (2009) 55-62
Table 2. Basicity of various CH3COOK/artificial zeolite catalysts calcined at different temperatures.
Entry Samples Calcination temperature (K) Basicity (mmol KOH/g)
1 Artificial zeolite – 0
2 Artificial zeolite 873 0
3 9%CH3COOK/artificial zeolite 823 0.0246
4 23%CH3COOK/artificial zeolite 823 0.1393
5 33%CH3COOK/artificial zeolite 823 0.3122
6 41%CH3COOK/artificial zeolite 823 0.3527
7 47%CH3COOK/artificial zeolite 823 0.4058
8 50%CH3COOK/artificial zeolite 823 0.3786
9 47%CH3COOK/artificial zeolite – 0.2079
10 47%CH3COOK/artificial zeolite 523 0.2540
11 47%CH3COOK/artificial zeolite 623 0.2832
12 47%CH3COOK/artificial zeolite 723 0.3689
13 47%CH3COOK/artificial zeolite 923 0.2956
14 47%CH3COOK/artificial zeolite 973 0.1654
basicity (0.4058 mmol KOH/g; entry 7). This is similar
to the findings of Xie et al. [11] The calcination tem-
perature also affects catalyst basicity. It is evident from
Table 2 that catalysts calcined at 823K had the highest
basicity (entries 7, 9-14). It was noted that 47% CH3
COOK/artificial zeolite without calcination had higher
basicity than 23% CH3COOK/artificial zeolite calcined
at 823 K (0.2079 vs. 0.1393 mmol KOH/g, entries 9
and 4).
3.2 Basicity of the Catalyst
Table 2 summarizes the basicity of a series of
CH3COOK/artificial zeolite catalysts calcined at differ-
ent temperatures, as determined using Hammett indica-
tors. As shown in Table 2, the basicity of catalysts cal-
cined at 823 K first increases and then decreases with the
increasing CH3COOK loading (entries 2-8), with 47
wt.% CH3COOK/artificial zeolite exhibiting the highest
basicity (0.4058 mmol KOH/g; entry 7). This is similar
to the findings of Xie et al. [11] The calcination tem-
perature also affects catalyst basicity. It is evident from
Table 2 that catalysts calcined at 823 K had the highest
basicity (entries 7, 9-14). It was noted that 47%
CH3COOK/artificial zeolite without calcination had
higher basicity than 23% CH3COOK/artificial zeolite
calcined at 823 K (0.2079 vs. 0.1393 mmol KOH/g, en-
tries 9 and 4).
3.3. Lnfluence of Catalyst Preparation
Conditions
3.3.1. Lnfluence of CH3COOK Loading
The catalytic activity of the catalysts was evaluated by
comparing the FAME content of the transesterification
products. The effect of CH3COOK loading on the cata-
lytic activity is shown Fig. 1. As the CH3COOK loading
increases from 9% to 47%, the methyl ester content in-
creases. The highest methyl ester content (91.58%) was
obtained for 47 wt.% CH3COOK loading. However, the
FAME content decreased slightly for a further increase
in CH3COOK loading, which may be due to partial cov-
ering of basic sites by K2O species from the excess
CH3COOK on the surface of the composite. It is impor-
tant to point out that the conversion decreased signifi-
cantly when potassium salt loading exceeded the critical
limit for the transesterification of soybean. [11]
3.3.2. Influence of Calcination Temperature
Figure 2 shows the influence of calcination temperature
on the catalytic activity in the temperature range from
523 to 923 K. The optimal calcination temperature ob-
served was 823 K. At this temperature, the methyl ester
content reached 91.58%. However, when the calcination
temperature increased to 923 K, the catalyst activity de-
creased. Such results are in line with the basicity proper-
ties shown in Table 2, indicating that higher basicity
results in higher conversion and higher methyl ester
content. However, the FAME content obtained using 47
wt.% CH3COOK/artificial zeolite calcined at 523 K is
lower than that obtained using 23 wt.% CH3COOK/arti-
ficial zeolite calcined at 823 K, although the basicity of
the former is higher than that of the latter (0.2540 vs.
0.1393 mmol KOH/g). This implies that basicity is the
most important, but not the only factor affecting the ac-
tivity of these supported catalysts.
3.4. FTIR Analysis
IR spectroscopy was used to investigate the CH3COOK/
artificial zeolite catalysts. The results are shown in Fig. 3.
For the parent artificial zeolite, two absorption bands at

W. Xue et al. / Natural Science 1 (2009) 55-62 59
Table 3. Results of orthogonal experiment L9_3_4 for base-
catalyzed transesterification and range analysis.
Factors and levelsExperimental results
Experimental
no. A B C Methyl ester content(%)
1 1 1 1 42.35
2 1 2 2 65.02
3 1 3 3 62.38
4 2 1 3 74.39
5 2 2 1 91.08
6 2 3 2 81.85
7 3 1 2 62.56
8 3 2 3 88.89
9 3 3 1 87.12
I 56.58 59.77 71.03
II 82.44 81.66 75.51
III 79.52 77.12 72.00
R 25.86 21.90 4.48
1020 30 40 50 60
0
20
40
60
80
100
Content of methyl esters (%)
Loading amount of Potassium acetate (wt. %)
Figure 1. Influence of CH3COOK loading on the content of
methyl esters. Reaction conditions: methanol/oil molar ratio,
10:1; catalyst amount, 2wt.%; reaction time, 4h; and methanol
reflux temperature.
500 600 700 800 9001000
20
30
40
50
60
70
80
90
100
Content of methyl esters (%)
Calcination temperature (K)
Figure 2. Influence of calcination temperature on the content
of methyl esters. Reaction conditions: methanol/oil molar ratio,
10:1; catalyst amount, 2wt.%; reaction time, 4h; and methanol
reflux temperature.
3440 and 1650cm–1 were attributed to stretching and
bending vibrations of physically absorbed water, respec-
tively. CH3COOK/artificial zeolites catalysts calcined at
high temperature (curves b, c, d, f and g in Fig. 3)
showed intense absorption at approximately 3440 cm–1,
which could be assigned to νOH stretching vibrations of
hydroxyl groups attached to the support. Such hydroxyl
groups are mainly formed by the reaction of sur-
face-absorbed water with the support during the activation
by calcination. [22] When the catalyst samples were cal-
cined at higher temperatures (curves d, f and g in Fig. 3),
there was very little absorbed water on the support sur-
face. However, there was still a strong absorption peak
at1650cm–1. This indicates that the peak at 1650cm–1
was mainly due to surface hydroxyl groups and that these
surface OH groups were possibly active sites, as reported
by Xie and Huang. [23]
Furthermore, the absorption broad band at 3440cm–1
could be partly assigned to stretching vibrations of
Al-O-K or Si-O-K groups. [24,25,26] According to Stork
and Pott, [27] K+ ions may replace the protons of hy-
droxyl groups attached to the support during activation.
Thus, K+ ions from CH3COOK could form Al-O-K or
Si-O-K groups by replacing the protons of hydroxyl
groups attached to the artificial zeolites during activation
by calcination, and can probably be considered to be
another active basic species of this catalyst in trans-
esterification.
As observed from Fig. 3, the absorption intensity at
3440cm–1 increased with the CH3COOK loading
(curves b-d), indicating that an increase in basic sites
resulted in an increase in catalytic activity, which is in
accordance with the results shown in Fig. 1. On the other
hand, the intensity of the abso0rption at 3440cm–1 de-
creased at higher calcination temperatures (curves d, f
and g), indicating a decrease in basic sites, in line with
Hammett basicity measurement (Table 2). The absorp-
tion peak at 1552cm–1 can be assigned to asymmetric
vibration of COO– [28] of CH3COOK (curve e), which
disappeared after calcination at 823K (curve d), demon-
strating that CH3COOK decomposed completely after
calcination at 823 K. In addition, there were some other
absorption peaks at 400-1400cm–1 for all samples,
which can be attributed to Al-O (or Si-O) symmetric
stretching and ring vibration in Al-O and Si-O tetraheda
formed through the oxygen atom.
3.5. XRD Analysis
XRD patterns of artificial zeolites and CH3COOK/arti-
ficial zeolite samples with different CH3COOK loading
are shown in Fig. 4. The XRD pattern of artificial zeo-
lites is irregular, which may be related to their structure.
After calcination of artificial zeolites loaded with
CH3COOK, more regular and distinct diffraction peaks
(* and □ in Fig. 4) appeared in the XRD patterns.

60 W. Xue et al. / Natural Science 1 (2009) 55-62
Figure 3. FTIR spectra: (a) artificial zeolites; (b) 33%
CH3 COOK/artificial zeolites calcined at 823 K for 5 h; (c)
41% CH3COOK/artificial zeolites calcined at 823 K for 5
h; (d) 47% CH3COOK/artificial zeolites calcined at 823 K
for 5 h; (e) 47% CH3COOK/artificial zeolites without cal-
cination; (f) 47% CH3COOK/artificial zeolites calcined at
923 K for 5 h; and (g) 47% CH3 COOK/artificial zeolites
calcined at 973 K for 5 h.
Figure 4. XRD patterns: (a) parent artificial zeolites; (b)
33% CH3COOK/artificial zeolites calcined at 823 K for 5 h;
(c) 41% CH3COOK/artificial zeolites calcined at 823 K for
5 h; (d) 47% CH3COOK/artificial zeolites calcined at 823
K for 5 h; and (e) 47% CH3COOK/artificial zeolites cal-
cined at 923 K for 5 h. * KAlSiO4, Kalsilite; □
K0.85Na0.15AlSiO4; ● K2Al2O4; and ▼ K2O.
This is possibly due to the reaction of CH3COOK with
the support during activation, resulting in the more
regular and stable structure necessary for catalysis.
As shown in Fig. 4, when the CH3COOK loading was
below 47wt.% (curves b and c), the XRD patterns con-
tained only diffraction peaks (2
 =20.5°,22.3°,28.6°,
34.6°,40.6°) assigned to new species formed by reaction
between CH3COOK and the support during the activa-
tion process. These diffraction peaks can probably be
ascribed to two new species, KAlSiO4 (Kalsilite; *) and
K0.85Na0.15AlSiO4 (□), formed by the movement of K+
from CH3COOK into the crystal lattices of the support
and subsequent reaction. There were no characteristic
peaks for CH3COOK or K2O, probably due to good dis-
persion of K+ derived from CH3COOK on artificial zeo-
lites in the form of various compounds, while a K2O
phase undetectable by XRD may have dispersed onto the
artificial zeolite surface as a monolayer. [29] In addition,
2  diffraction peaks at 32.8° and 58.6° can probably be
ascribed to K2Al2O4 (•), also obtained by reaction be-
tween K+ and the support.
However, when the CH3COOK loading increased to
47 wt.%, the characteristic XRD peaks of K2O (2  =
25.8°,41.9°) were detected (curve d in Fig. 4). According
to the results shown in Fig. 1 and Table 2, this K2O spe-
cies may account for the high catalytic activity and ba-
sicity of the catalyst, because 47% CH3COOK/artificial
zeolites calcined at 823K for 5h exhibited the highest
catalytic activity and basicity. Furthermore, when the
calcination temperature increased to 923K, the charac-
teristic XRD peak at 2
 =32.8° vanished, presumably
because K2Al2O4 (•) was destroyed at higher calcination
temperatures.
Taken together, the characterization results indicate
that K2O (derived from CH3COOK) and surface hy-
droxyl groups, as well as Al-O-K (or Si-O-K) groups,
were probably the active sites mainly responsible for the
transesterification of J. curcas oil with methanol.
3.6. Optimization of the Transesterification
Reaction
For the transesterification reaction, orthogonal experi-
ments were carried out to determine the optimum reac-
tion conditions. The effects of various factors on the
reaction were also studied. The orthogonal scheme cho-
sen and the data obtained are shown in Table 3.
As shown in Table 3, the extent to which the trans-
esterification of J. curcas oil was affected in terms of the
range (R) value was A＞B＞C, namely, oil/methanol
ratio (A) first, followed by catalyst amount (B) and reac-
tion time (C). Taking the FAME content into account,
the optimum reaction conditions were A2B2C2; namely,
oil/methanol ratio, 1:10; catalyst amount, 2wt.%; and
reaction time, 4h.
The molar ratio of J. curcas oil to methanol is the

W. Xue et al. / Natural Science 1 (2009) 55-62 61
most important factor affecting the transesterification to
methyl esters (Table 3). Theoretically, three moles of
methanol are required for one mole of triglyceride to
yield one mole of glycerol and three moles of FAME.
However, a slight excess of methanol is required to drive
the equilibrium to the product side, because the trans-
esterification reaction is reversible. [1] With an increase
in the oil/methanol molar ratio, the conversion increased
considerably. However, further addition of methanol not
only had no significant effect on the conversion, but also
seriously affected glycerine separation due to the in-
crease in solubility. [30] Thus, the optimum molar ratio
of J. curcas oil to methanol to produce methyl esters was
1:10.
The amount of catalyst is another important factor that
affects the reaction. With no catalyst, transesterification
does not occur. When the amount of catalyst was insuf-
ficient, the FAME content was very low (entries 1, 4, 7).
Saponification took place when the amount of catalyst
was increased to 3%, leading to product emulsion and
making separation difficult. The FAME content and
product yield were also influenced (entries 3, 6, 9). As
revealed in orthogonal experiments, 2 wt.% catalyst was
appropriate for this transesterification reaction.
The final factor affecting transesterification is the re-
action time. When the reaction time is too short, the con-
version of vegetable oil to methyl esters is incomplete,
and conversion increases with the reaction time. How-
ever, when the reaction reaches equilibrium, prolonged
reaction time does not increase the FAME content of the
product, but increases the cost for biodiesel production.
In homogeneous base-catalyzed transesterification, the
reaction time is usually less than 1 h. For heterogeneous
transesterification the reaction time needs to be longer,
because the system components, the base catalyst,
methanol and J. curcas oil in the present study, require a
longer contact time. According to orthogonal experi-
ments, an optimum reaction time of 4 h was chosen.
An experiment was carried out under above optimum
reaction conditions, a product yield of 94.27% and
methyl ester content of 91.58% were obtained after
transesterification.
4. CONCLUSIONS
Easily prepared solid-base catalysts using artificial zeo-
lites as a support were developed for the transesterifica-
tion of J. curcas oil with methanol to produce biodiesel.
The CH3COOK/artificial zeolites solid catalysts exhib-
ited high catalytic activity in the transesterification
process. The methyl ester content exceeded 91% when
the catalyst with 47 wt.% CH3COOK was calcined at
823 K for 5 h. Catalyst characterization revealed that
K2O, surface hydroxyl groups and Al-O-K (or Si-O-K)
groups are the main basic sites. Furthermore, the activity
of the catalysts depends strongly on their basicity. Or-
thogonal experiments revealed the following optimum
reaction conditions: oil/methanol ratio, 1:10; catalyst
amount, 2wt.%; and reaction time, 4h. No water washing
step is needed thus no waster water was produced during
this process. The information mentioned above estab-
lishes certain basis for industrial biodiesel production
from J. curcas seed oil using the heterogeneous catalysts.
Further investigations on the reaction mechanism and
active sites are under way in our laboratory.
ACKNOWLEDGEMENT
This work is financially supported by Program for New Century Ex-
cellent Talents in Chinese University (NCET-05-0818), Key Science
and Technology Project of Guizhou Province (No. 20076004), and the
National Key Technology R&D Program (2006BAD07A12).
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