100
95
90
85
80
75
70
Ester conversion (%)
0.894
0.892
0.89
0.888
0.886
0.884
0.882
0.88
0.878
Specific gravity
3
4
6
2 0
3 0
Molar ratio
Ester conversion
s.g. of ester
Biodiesel
51
Figure 3.6
Ester conversion with respect to molar ratio. (From Canakci, M. and Van Gerpan, J., ASAE,
42, 1203–10, 1999. Reprinted with permission from the American Society of Agricultural and
Biological Engineers.)
TABLe 3.1
Effect of Alcohol Type on Ester Conversion and Specific Gravity of Ester
Alcohol
Type
Boiling
Temperature (ºC)
Reaction
Temperature (ºC)
Ester
Conversion (%)
Ester Specific
Gravity
Methanol
2-propanol
1-butanol
Ethanol
65.0
82.4
117.0
78.5
60
75
110
75
87.8
92.9
92.1
95.8
0.8876
0.8786
0.8782
0.8814
Source: From Canakci, M. and Van Gerpan, J., ASAE, 42, 1203–10, 1999. Reprinted with permission from the American Society of Agricultural and Biological Engineers.
Test conditions: molar ratio: 6:1, sulfonic acid amount: 3%, reaction temperature: 48 hours.
3.2.3 Supercritical Alcoholysis
Free fatty acid content and water in the vegetable oil plays a major role in
conventional transesterification process. Presence of FFAs and water causes
soap formation, consumes catalyst, and reduces the effectiveness of catalyst
that leads to reduction in conversion efficiency. Transesterification of the
vegetable oil with the help of catalysts reduce the reaction duration but promotes complications in purification of biodiesel from catalysts and saponified products. Purification of biodiesel and separation of glycerol from the
catalyst are necessary, but it would increase the cost of overall production
process. The supercritical alcohol transesterification process is catalyst-free