G. C. Díaz et al. / Natural Science 3 (2011) 530-534
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534
- Hydrolysis of soybean oil at 250˚C and 270˚C, using
25% NiO/Al2O3 as catalyst, at 1, 2 and 3 hours of reac-
tion time.
- Hydrolysis of tallow at 250˚C and 270˚C, using 25%
NiO/Al2O3 as catalyst, at 1, 2 and 3 hours of reaction
time.
Linoleic and linolenic acids selectivity was estimated
from the selectivity ratio (SR). SR was calculated using
Allen’s method [14] as original proposed by Albright
[15].
SR is defined as K2/K3, where K2 = l – Lo, K3 = S – So.
Lo and So represent the linoleic and stearic acid contents
in the original raw material and L and S in the hydro-
genated sample. In the same manner the selectivity ratio
(SR) regarding linolenic acid is calculated by: SR=K1/K 2,
K1 = 1 – Lno, K2= O – Oo, Lno and Oo represent the lino-
lenic and oleic acid contents in the original raw material
and Ln and O in the hydrogenated sample. The results
for soybean oil and tallow are reported in Table 6.
During the hydrogenation of raw materials the selec-
tivity ratios (SR) were high, thus can be assumed that the
reactions were selective under these conditions.
The selectivity can be increased with the temperature,
or by increasing the pressure and agitation. Analyzing
the influence of temperature on SR, it is observed that
increasing the temperature of the reaction of soybean oil
using catalyst 25% NiO/Al2O3 decreases the selectivity
of linoleic acid and increases the selectivity of linolenic
acid. In comparison, the temperature has not significant
influence on the reaction with tallow.
Results of high selectivity in hydrogenation of linoleic
acid and linolenic acid were observed only in reactions
catalyzed by 25% NiO/Al2O3, it is known that commer-
cially employed Ni catalyst has a limited linoleic selec-
tivity [15].
4. CONCLUSIONS
The hydrolysis of soybean oil and tallow were studied
in this paper. Hydrogenation occurs in-situ during the
hydrolysis, producing large amount of saturated and
mono unsaturated fatty acids, such as stearic and oleic
acids. These effects were best manifested under 3 hours
of the reaction and with the catalysts 25% NiO/Al2O3.
The glycerol formed during the hydrolysis behaves as
a hydrogen donor. The reform of the glycerol generates
the in-situ hydrogen, hydrogenating the fatty acids pro-
duced. High hydrogenation selectivity of linoleic and
linolenic acid were observed in the reactions using 25%
NiO/Al2O3. It was not observed hydrogenation of un-
saturated fatty acids during the hydrolysis using 5 and
10% NiO/Al2O3.
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