Page 177 - eProceeding - IRSTC & RESPEX 2017

NUR SHUHADA ARBAAN / JOJAPS – JOURNAL ONLINE JARINGAN COT POLIPD
2.2 Vegetable Oils

Most vegetable oils are triglycerides (TGs; triglycerides=TG). Chemically, TGs are the triglycerides esters of various fatty
acids with glycerol (Figure 2.3). Some physical properties of the most common fatty acids occurring in vegetable oils and animal
fats as well as their methyl esters are listed in Table 2.2. Besides these fatty acids, numerous other fatty acids occur in vegetable
oils and animals fats, but their abundance usually is considerably lower. Table 2.1 lists the fatty acid composition of some
vegetable oils and animal fats that have been studied as sources of biodiesel.
CH 2OOR CH 2OH

CHOOR + 3 CH 3OH 3 CH 3OOCR CHOH
→ +
CH 2OOR CH 2OH

Triglyceride Methanol Methyl Ester Glycerol

Figure 2.3: Structure of triglycerides and principle of the transesterification reaction

The most common derivatives of TGs or fatty acids for fuels are methyl esters. These are formed by transesterification of the
TG with methanol in presence of usually a basic catalyst to give the methyl ester and glycerol as in Figure 2.3. Other alcohols
have been used to generate esters, for example, the ethyl, propyl, and butyl esters (Gerhard Knothe, 2009)

Table 2.1: Major fatty acids (in wt. -%) of some oils and fats used or tested as alternative diesel fuels (Gerhard Knothe, 2009)
Oil or Fat Fatty Acid Composition (Wt. - %)
12:0 14:0 16:0 18:0 18:1 18:2 18:3 22:1
Babassu 44- 15-17 5.8-9 2.5- 12-16 1.4-3 - -
45 5.5
Canola - - 4-5 1-2 55-63 20-31 9-10 1-2
Coconut 44- 13- 7.5- 1-3 5-8.2 1.0-2.6 - -
51 18.5 10.5
Corn - - 7-13 2.5-3 30.5-43 39-52 1 -
Cottonseed - 0.8- 22-24 2.6-5 19 50-52.5 - -
1.5
Linseed - - 6 3.2-4 13-37 5-23 26-60 -
Olive - 2.3 7-18.3 1.4- 55.5- 4-19 - -
3.3 84.5
Palm - 0.6- 32- 4-6.3 37-53 6-12 - -
2.4 46.3
Peanut - 0.5 6-12.5 2.5-6 37-61 13-41 - 1
Rapeseed - 1.5 1-4.7 1-3.5 13-38 9.5-22 1-10 40-64
Safflower - - 6.4- 2.4-29 9.7-13.8 75.3- - -
7.0 80.5
Safflower, high-oleic - - 4-8 2.3-8 73.6-79 11-19 - -

Sesame - - 7.2- 5.8- 35-46 35-48 - -
9.2 7.7
Soybean - - 2.3-11 2.4-6 22-30.8 49-53 2-10.5 -
Sunflower - - 3.5- 1.3- 14-43 44-69.7 - -
6.5 5.6
Tallow - 3-6 25-37 14-29 26-50 1-2.5 - -
(beef)
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