Transesterification of triolein to biodiesel fuel over mordenite-supported CaO catalysts

Article abstract of DOI:10.1246/cl.2010.198

CaO catalysts supported on several metal oxides and zeolites were investigated for transesterification of triolein with methanol. Zeolite-supported CaO catalysts showed high catalytic activity for transesterification compared to the metal oxide-supported CaO catalysts; among the zeolites tested in this work, mordenite exhibited the best support. The catalytic activity of mordenite-supported CaO catalyst depended on both the amount of CaO loading and the calcination temperature for catalyst precursor.

Full text of DOI:10.1246/cl.2010.198

doi:10.1246/cl.2010.198
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Published on the web January 30, 2010
Transesterification of Triolein to Biodiesel Fuel over Mordenite-supported CaO Catalysts
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Syuhei Yamaguchi, Makiko Asamoto, Syun Inoue, Satomi Kawahito, Yasuhiro Mieno, Kenji Ikushima, and Hidenori Yahiro*
1
Department of Materials Science and Biotechnology, Graduate School of Science and Engineering,
Ehime University, Matsuyama 790-8577
Shikoku Operations, Taiyo Oil Co., Ltd., Imabari 799-2393
2
(
Received November 20, 2009; CL-091030; E-mail: hyahiro@eng.ehime-u.ac.jp)
a
b
CaO catalysts supported on several metal oxides and zeolites
were investigated for transesterification of triolein with methanol.
Zeolite-supported CaO catalysts showed high catalytic activity for
transesterification compared to the metal oxide-supported CaO
catalysts; among the zeolites tested in this work, mordenite
exhibited the best support. The catalytic activity of mordenite-
supported CaO catalyst depended on both the amount of CaO
loading and the calcination temperature for catalyst precursor.
Table 1. BDF yields and specific surface areas of supported CaO catalysts
Specific
Calcination
temp/°C
BDF yield
/©10¹2 mol (g-CaO)¹1
Catalyst
surface area
2
¹1
/m (g-cat.)
CaO/MOR
500
600
0
®c
84.8
55.6
44.2
40.2
14.3
12.6
5.5
23.3
25.5
26.6
31.7
39.7
19.7
4.0
7
7
7
7
8
9
00
25
50
75
00
00
Biodiesel fuel (BDF) is a promising non-toxic and biode-
gradable renewable alternative fuel comprised of fatty acid
methyl esters derived from vegetable oil or animal fat. Methyl
esters are usually produced by the transesterification of triglyc-
CaO/MFI
775
775
775
775
36.5
9.0
11.3
6.8
39.5
175
169
CaO/SiO ­Al O
2
2
3
CaO/SiO2
1
CaO/Al O
80.7
eride with methanol. The transesterification reaction has been
2
3
reported to proceed efficiently in the presence of homogeneous
base or acid catalysts.2 Homogeneous base catalysts such as
NaOH and KOH are potential candidates for use in the latest
industrial processes for BDF production, due to faster reaction
CaO
MOR
CaCO3
a
900
775
none
2.5
0
0
12.0
®
®c
­6
c
Reaction condition: catalyst (0.05 g), triolein (2.0 g), methanol (10 mL),
50 °C, 0.5 h. bCaO loading of supported catalyst was 30 wt %. cNot
7
rates compared to the acid catalysts; however, it is difficult to
measured.
separate the homogeneous catalysts from the reaction solution.
A large number of heterogeneous base catalysts have been
studied for the transesterification of vegetable oil to BDF:
alkaline earth metal oxides and various alkaline metal com-
pounds supported on alumina or zeolite.8 In particular, calcium
oxide (CaO), a heterogeneous base catalyst, has been widely
by the yields of methyl oleate ester (BDF yield), where the BDF
yields were normalized by the weight of CaO loaded.
The BDF yields and the specific surface areas of supported
CaO catalysts are summarized in Table 1, together with those of
­16
1
4­16
studied for transesterification due to economical advantages.
CaO and CaCO reference catalysts. As shown in Table 1, the
3
By calcination in a helium gas flow, CaO was activated to match
NaOH at catalyzing transesterification of soybean oil with
BDF yields of all the supported CaO catalysts calcined at 775 °C
were higher than that of unsupported CaO reference catalyst
calcined at 900 °C. Predictably, BDF yield was enhanced by
supporting CaO on oxides with high surface area. BDF yields
of the supported CaO catalysts calcined at 775 °C were depend-
ent on the kind of supports and decreased in the following order:
CaO/MOR > CaO/MFI º CaO/SiO > CaO/SiO ­Al O >
CaO/Al2O3. The order of BDF yield was not in agreement with
that of specific surface area, suggesting that the specific surface
area is not the main parameter controlling catalytic activity.
Among the supported CaO catalysts listed in Table 1, CaO/
MOR exhibited the highest catalytic activity for transesterifica-
ton of triolein with methanol to BDF. Therefore, the catalytic
properties of CaO/MOR were studied in more detail.
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refluxing methanol. It is expected that supporting CaO on metal
oxides with high surface area enhances the catalytic activity.
However, there is little information about the catalytic activity of
supported CaO catalysts for transesterification.18 In this study, we
investigated the catalytic activities of CaO catalysts supported on
several metal oxides and zeolites for the transesterification of
triolein with methanol to BDF.
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An aqueous calcium acetate solution was impregnated on
each support, followed by the calcination in vacuum at 500­
900 °C for 1 h to obtain supported CaO catalysts (designated as
CaO/support). The amount of CaO loaded on each support
ranged between 0 and 40 wt %. As reference catalysts, commer-
cial CaO calcined at 900 °C in vacuum and as-received CaCO3
were used.
A 2.0-g portion of triolein, 0.05 g of catalyst, and 10 mL of
methanol were added to a 100-mL flask under magnetic stirring
at 500 rpm. Transesterification reactions were carried out at
The catalytic activity of CaO/MOR catalyst significantly
depended on the calcination temperature of impregnated pre-
cursor, (CH CO ) Ca/MOR, as shown in Table 1. No catalytic
3
2 2
activity was observed for CaO/MOR calcined at 500 °C. When
the CaO/MOR was calcined above 600 °C, BDF was produced.
The BDF yield was most increased by catalyst calcined at 775 °C
and drastically decreased by catalysts calcined at 800 and 900 °C.
Figure 1 shows in situ XRD patterns of (CH3CO2)2Ca/
5
0 °C for 0.5 h under N atmosphere. After the reaction, the solid
2
catalysts were removed by filtration. Products in the filtrate were
fractionated and analyzed by GC-MS. The amount of methyl
oleate ester was determined by comparison with that of 1-
octanol as an internal standard. Catalytic activity was evaluated
MOR recorded at 600­900 °C under flowing N . When the
2
sample was heated up to 600 °C, the diffraction peaks attributed
Chem. Lett. 2010, 39, 198­199
© 2010 The Chemical Society of Japan
www.csj.jp/journals/chem-lett/

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The BDF yields of MOR-supported CaO catalysts calcined
at 775 °C with different CaO load were also investigated. Na-
MOR without CaO exhibited no catalytic activity (Table 1),
supporting our statement that CaO acts as the active site for
transesterification of triolein. Catalytic activity was low for
CaO/MOR catalyst with 10 wt % CaO loading. Maximal
activity was achieved for CaO/MOR catalyst with 30 wt %
CaO loading. When the amount of CaO loading was further
increased, the catalytic activity drastically decreased. This may
be due to the aggregation of CaO particles. A similar result has
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3
been reported by Xie et al.
Catalytic activity for transesterification has been reported
to be dependent on basicity; the stronger the basicity, the higher
8
,9,11
the activity.
Arishtirova and co-workers reported that the
basicity of BaO supported on zeolite changed according to
the type of zeolite support used and that the MOR-supported
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4
BaO showed the strongest basicity. Considering the above
literature, CaO/MOR catalyst may have the strong basicity,
resulting in the high catalytic activity for transesterification.
Further study is required.
We first demonstrated that the zeolite-supported CaO
catalysts, especially CaO/MOR calcined at 775 °C, exhibited
the best performance for transesterification of triolein with
methanol to BDF among several metal oxide- and zeolite-
supported CaO catalysts. The stabilities of supported CaO
catalysts are under investigation.
Figure 1. In situ XRD patterns of (CH3COO)2Ca/MOR heated at
a) 600, (b) 700, (c) 800, and (d) 900 °C. , CaO; , CaCO3; , CaSiO3;
£-CaSiO3; and , MOR.
(
,
to CaCO3 ( ) were clearly observed together with those to MOR
zeolite ( ). For the sample heated at 700 °C, the diffraction
We thank Professor Dr. Koichi Eguchi and Dr. Hiroki
Muroyama, Kyoto University, for permission and support to use
the in situ XRD equipment.
peaks due to CaCO decreased and those assigned to CaO ( )
3
were newly observed. The crystalline sizes of CaO on MOR
were calculated from Scherrer’s equation to be ca. 21 nm at 700­
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© 2010 The Chemical Society of Japan www.csj.jp/journals/chem-lett/