D.M. Reinoso et al. / Applied Catalysis A: General 449 (2012) 88–95
95
diffraction and FTIR spectrometry. These solids were evaluated in
the transesterification of soybean oil and in the esterification of
oleic acid with methanol.
Zinc laurate, palmitate, stearate and oleate were tested in the
transesterification of soybean oil at 100 ◦C for 2 h, and they showed
oil conversions between 88 and 94% with FAME yields between 71
and 74%. These catalysts showed a long life and could be reused
for several catalytic cycles without deactivation. Zn carboxylates
showed a good tolerance to water. Zn acetate was not stable. At
140 ◦C the salts transformed into Zn glycerolate in the reaction
medium.
It was observed that in the presence of fatty acids the salts
gradually exchanged for the acid to be esterified. In oleic acid,
the exchange was complete for Zn acetate and laurate at 20 ◦C,
and at 60 ◦C for Zn palmitate and stearate. However, when the
esterification of the pure fatty acid was studied with the Zn car-
boxylic salt of the corresponding acid (Zn oleate), it was active
and stable (62% conversion at 140 ◦C), although the case was
different for zinc acetate, which partially transformed into zinc
oxide.
Zinc laurate, palmitate, stearate are crystalline solids, but solu-
ble in the reaction medium at 100 ◦C, and they re-crystallize rapidly
at room temperature, which generates important advantages: They
present lower mass transfer resistances than heterogeneous cata-
lysts, and they can be easily separated from the reaction medium
and reused without activation or cleaning treatments. These solids
are also environmentally friendly.
Fig. 13. ZnOl used in five consecutive esterification catalytic tests.
ZnOl T5
ZnOl T4
ZnOl T3
ZnOl T2
0
10
20
30
40
50
60
Fig. 14. XRD pattern of used ZnOl salts after five reaction cycles at 140 ◦C.
Acknowledgements
The authors thank the Agencia Nacional de Promoción Cientí-
fica y Tecnológica (National Agency of Scientific and Technological
Promotion, Argentina) and the Consejo Nacional de Investigaciones
Científicas y Técnicas (National Council for Scientific and Techno-
logical Research, CONICET) for the financial support.
ZnOlT5
ZnOlT4
ZnOlT3
ZnOlT2
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Zinc(II) acetate, laurate, palmitate, stearate and oleate were
prepared, and their correct synthesis was confirmed by X-ray