Environmental Engineering Reference
In-Depth Information
taBle 25.5
Fatty acid methyl ester composition of Biodiesel Fuels
Percentage of
united states
myristic
c14:0
Palmitic
c16:0
stearic
c18:0
linoleic
c18:2
linolenic
c18:3
Biodiesel
lauric c12:0
oleic c18:1
ROME
88.00
Trace
0.10
6.00
5.90
16.00
71.40
0.60
LOME
78.87
Trace
0.24
12.46
8.32
27.78
37.65
13.44
KOME
72.32
Trace
0.05
9.94
7.83
53.19
19.09
0.04
NOME
60.40
Trace
0.47
18.20
20.10
43.70
16.40
0.30
MOME
50.00
Trace
0.00
24.20
25.80
37.20
12.80
0.00
taBle 25.6
Pearson correlation coefficient
correlation
coefficient
x variable
y variable
Percentage of
unsaturation
Density
0.955
Heating value
-0.869
Cetane number
-0.989
Iodine value
0.956
other properties. From Table 25.4, it can be observed that the density of different biodiesels is not
the same and that the maximum is observed for ROME (885 kg/m 3 ) and minimum for MOME
(875  kg/m 3 ). It was observed from the literature (Shigley et al. 1995) that the density decreases
with an increase in chain length, carbon number, or molecular weight and increases with degree
of unsaturation. Density decreases from C8:0 to C18:0 and increases from C18:1 to C18:3. Because
ROME is dominated by unsaturated linoleic ester (C18:2), the density of which is higher compared
with lower saturated carbon chain esters, it exhibits a higher density compared with other biodiesel
fuels. In the case of ROME, the unsaturation (the double bond) and when it deforms the linearity
when it is introduced in a structure and forms a bend structure. This is only in the case of the cis-
structure in which two hydrogen atoms are on the same side of the carbon atom and they repel each
other, thereby giving a bend structure. On the other hand MOME, which is equally dominated by
both unsaturated and saturated esters (C12:0), shows a lower density compared with other biodiesel
fuels. From Table 25.6, it can be observed that a high positive correlation exists between the unsatu-
ration percentage and density.
The relationship between the fatty acid methyl ester composition and density of biodiesel fuels
was investigated, revealing that the higher density of ROME may be more due to the contribution
of unsaturated fatty acids in ROME than that of the other biodiesels. Similarly, the lower density
of MOME is believed to be due to the lesser contribution of unsaturated fatty acids in MOME.
The scatter plot between the density and percentage of unsaturation with the fitted trend line equa-
tion is shown in Figure 25.5. The figure provides a clear picture that a highly positive correlation
exists between density and percentage of unsaturation. Therefore, it may be stated that the density
of biodiesel fuels increases with an increase in the percentage of unsaturation or in the number of
double bonds.
By differentiating the fitted line equation y = 0.268 x + 860.47 with respect to x (i.e., percentage
of unsaturation) the gradient between density and percentage of unsaturation can be found as 0.268.
This means, for every 1% increase in unsaturation, it may result in 0.268 units (kg/m 3 ) increase in
density, where, r 2 denotes the coefficient of determination.
 
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