Page 130 - Advances in Eco-Fuels for a Sustainable Environment

102 Advances in Eco-Fuels for a Sustainable Environment

acid (34.8wt%), and palmitoleic acid (6.8wt%). Palmitic acid (5.9wt%) and stearic
acid (2.3wt%) are the other fatty acids present in the oil [17]. According to work car-
ried out by Holser and Kuru [49], >99% methyl esters of milkweed oil have been
obtained for a methanol to oil molar ratio of 6:1 at 60°C in a reaction time of
60min using 1g CH 3 ONa catalyst. Some of the properties displayed by methyl esters
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of milkweed seed oil include a kinematic viscosity of 5.2mm /s, a cloud point of
0.8°C, and a pour point of 6.7°C [49].

Tung oil (Vernicia fordii)
Tung (Vernicia fordii) belonging to the Euphorbecaeae family, is a small- to medium-
sized deciduous tree. It is native to countries such as China, Burma, and Vietnam. The
fruit is 4–6cm long and 3–5cm in diameter and is a hard, woody, pear-shaped drupe
containing 4–5 large seeds [17]. The nuts of the Tung tree are used to extract Tung oil.
The oil content in the nut is 30–40wt%. Tung oil contains a high content of unsatu-
rated fatty acid, thus Tung biodiesel shows very low oxidation stability and very good
low-temperature behavior. The unsaturated fatty acids present in Tung oil are
eleostearic acid (63.8wt%), linoleic acid (11.51wt%), and oleic acid (8.56wt%),
and the saturated fatty acids present are palmitic acid (3.03wt%) and stearic acid
(2.2wt%). Tung oil also contains other fatty acids such as behenic acid (8.39wt%),
eicosenoic acid (0.75wt%), and heneicosanoic acid (0.46wt%) [17]. Park et al.
[50] found that the maximum conversion of 90.2% has been obtained for a methanol
to oil molar ratio of 7.5:1 at a reaction temperature of 80°C and in a reaction time of
20min using KOH as a catalyst. Some of the properties exhibited by tung oil biodiesel
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include a kinematic viscosity of 9.8mm /s, an acid value of 0.59mgKOH/g, and a
cold filter plugging point of 11°C [50].

Rubber seed oil (Hevea brasiliensis)
The rubber tree (Hevea brasiliensis) originating from South America has been culti-
vated as an industrial crop since its introduction to Southeast Asia and it belongs to the
Euphorbiaceous family. Below 200m altitudes and temperature about 27–28°C, the
growth of the rubber tree is most rapid. Thailand (35%), Indonesia (23%), Malaysia
(12%), India (9%), and China (7%) are the natural rubber tree producers [51].The
trees grow 34m in height and produce seeds that weigh 2–4g. The oil content in rubber
seeds ranges from 40 to 50wt% and the free fatty acid (FFA) content is 17wt%. The
main unsaturated fatty acids present in rubber seed oil are linoleic acid (39.6wt%),
oleic acid (24.6wt%), and linolenic acid (16.3wt%). Palmitic acid (10.2wt%) and
stearic acid (8.7wt%) are the saturated fatty acids in rubber seed oil [17]. As per
the work carried out by Morshed et al. [52], the maximum conversion of free
fatty acids from rubber oil to its corresponding methyl esters obtained has been
98% for methanol to free fatty acid molar ratio of 5:1 in a reaction time of 30min
and at reaction temperature of 68–70°C using 5% (wt of oil) NaOH catalyst.
Some of the properties displayed by methyl esters of rubber seed oil include a kine-
2
matic viscosity of 4.5mm /s, an acid value of 0.12mgKOH/g, a calorific value of
32.6MJ/kg, a cloud point of 3°C, and a pour point of 5°C [52].