O
O
(H 2 SO 4 )
HO–C–R + CH 3 OH
CH 3 –O–C–R + H 2 O
Fatty acid
Methanol
Methyl ester
Water
R 2 OH
O
R–C–O–R 1
O–R 2
H
R–OC–O + –R 1
R–OC–R 1
H
+
H
H
+
R–OC–O
+
–R 2
–H
+
R–OC–O–R 2
H
50
Alternative Fuels for Transportation
the separation of methyl esters from the glycerol and contributes to emulsion formation during the water wash. For these cases, acid catalyst such as
sulfuric acid is used to esterify the FFAs to methyl esters. Figures 3.4 and 3.5
show the acid esterification reaction equation and its mechanism, respectively. Figure 3.6 shows the ester conversion with respect to molar ratio.
Canakci and Van Gerpan (1999) reported that the standard conditions of
the reaction consisted of 60°C reaction temperature, 3% sulfuric acid, 6:1
molar ratio of the methanol to the oil, and reaction duration of 48 hours.
Figure 3.6 shows the ester conversion with respect to molar ratio. The ester
conversion increased from 87.8 to 95.1% when the reaction time was increased
from 48 to 96 hours.
Different alcohols have different boiling points and reaction temperature
is chosen nearer to the boiling point. Effect of alcohol type on transesterification of vegetable oils is shown in Table 3.1. The ester conversion is inhibited
by the presence of water in the oil. If the water concentration in oil is greater
than 0.5%, the ester conversion drops below 90%. The alcohols with higher
boiling points increase the ester conversion. Water formed by esterficiation
further reduces reactions. It has been reported that more than 0.5% water in
the oil would decrease the ester conversion to below 90%.
Figure 3.4
Acid esterification equation.
Figure 3.5
Mechanism of acid catalyzed transesterification of vegetable oils. (From Demirbas, A.,
Energy Conversion and Management, 50, 14–34, 2009. Reprinted with permission from Elsevier
Publications.)
O
(H 2 SO 4 )
HO–C–R + CH 3 OH
CH 3 –O–C–R + H 2 O
Fatty acid
Methanol
Methyl ester
Water
R 2 OH
O
R–C–O–R 1
O–R 2
H
R–OC–O + –R 1
R–OC–R 1
H
+
H
H
+
R–OC–O
+
–R 2
–H
+
R–OC–O–R 2
H
50
Alternative Fuels for Transportation
the separation of methyl esters from the glycerol and contributes to emulsion formation during the water wash. For these cases, acid catalyst such as
sulfuric acid is used to esterify the FFAs to methyl esters. Figures 3.4 and 3.5
show the acid esterification reaction equation and its mechanism, respectively. Figure 3.6 shows the ester conversion with respect to molar ratio.
Canakci and Van Gerpan (1999) reported that the standard conditions of
the reaction consisted of 60°C reaction temperature, 3% sulfuric acid, 6:1
molar ratio of the methanol to the oil, and reaction duration of 48 hours.
Figure 3.6 shows the ester conversion with respect to molar ratio. The ester
conversion increased from 87.8 to 95.1% when the reaction time was increased
from 48 to 96 hours.
Different alcohols have different boiling points and reaction temperature
is chosen nearer to the boiling point. Effect of alcohol type on transesterification of vegetable oils is shown in Table 3.1. The ester conversion is inhibited
by the presence of water in the oil. If the water concentration in oil is greater
than 0.5%, the ester conversion drops below 90%. The alcohols with higher
boiling points increase the ester conversion. Water formed by esterficiation
further reduces reactions. It has been reported that more than 0.5% water in
the oil would decrease the ester conversion to below 90%.
Figure 3.4
Acid esterification equation.
Figure 3.5
Mechanism of acid catalyzed transesterification of vegetable oils. (From Demirbas, A.,
Energy Conversion and Management, 50, 14–34, 2009. Reprinted with permission from Elsevier
Publications.)