Effect of temperature
The temperature at which reaction conducted has significant
impact over rate of reaction. Using higher reaction temperature
can diminish the viscosity of the oil which results in enhanced
reaction rate. It is said that, there action temperature must be
lower than the boiling point of the alcohol to make sure that
alcohol does not get vaporised. If higher reaction temperature is
used unnecessarily, yield drops down due to soap formation. On
Table 9
Literature summary of biodiesel prepared in super critical conditions.
Vegetable oil Alcohol used Molar ratio Temperature (°C) Time (min) Pressure (bar) Yield (%) Reference
Pongamia pinnata Methanol 50:1 300 40 200 85 [87]
Ethanol 90
Jatropha curcas Methanol 80
Ethanol 82
Palm oil Ethanol with hexane as co-solvent 25:1–50:1 260–300 10–30 – 90 [88]
Camelina sativa oil Butanol 40:1 305 80 – 87.6 [89]
Canola Ethanol 40:1 350 30 200 93.7 [90]
Microalgae oil (Chlorella protothecoides) Methanol 10:1–42:1 270–350 10–50 – 90.8 [91]
Ethanol 87.8
Rapeseed oil Methanol 42:1 350 15 120 93 [92]
Ethanol 20 91.9
1-Propanol 25 91.1
Sunflower oil Ethanol with CO2 as co-solvent 20:1 to 45:1 150–200 2–10 150–200 80 [93]
Sunflower oil Ethanol 25:1 150–200 2–10 200 80 [94]
Palm oil Ethanol 33 349 30 – 79.2 [95]
Palm oil Methanol – 300–420 150–200 81.5 [96]
Ethanol 79.2
Rapeseed oil Methanol 42:1 350 15 120 93 [97]
Ethanol 42:1 350 15 100 91
Castor Ethanol with 0.1% NaOH – 200–350 30–90 – 98.9 [98]
Canola oil Methanol 40:1 350 10 200 100 [99]
Ethanol 30 80
Tert-butyl methyl ether 30 60`
Table 10
Summary of some non-traditional biodiesel production processes.
Feedstock Technology used Finding Advantage Reference
Yellow horn oil Microwave-assisted
transesterification
High yield of 96% was obtained Rapid conversion of triglycerides into biodiesel. [76]
Food industry
waste
Corona discharge plasma
technology
Acid value indicates the content of free fatty
acids in the biodiesel and the value obtained in
this study was 0.43 mg KOH/g.
1. Acceleration of the esterification reaction.
2. Easy separation of the biodiesel.
3. Elimination of waste generation
[100]
High acid value
waste oil
Ultrasonic assisted Enzyme catalytic
transesterification
Conversion of 95% was achieved in 50 min 1. Ultrasonic energy reduced the adsorption of
glycerol by-product on the surface of the
immobilized lipase.
2. Ultrasonic irradiation avoids the generation
of water or glycerine phases inside the
catalyst
[101]
Canola oil Membrane technology Highly pure biodiesel 1. Reduction of cost incurring in separation of
products and recycling.
2. Higher conversion in single reaction.
3. Products obtained are rich in purity.
[102,105]
Feedstock with
high FFA
Reaction distillation Reduces the usage of alcohol in excess 1. Less time required to achieve equilibrium.
2. Less usage of alcohol
3. Reduced energy requirement for reaction.
[103,104]
P. Verma et al. / Renewable and Sustainable Energy Reviews 56 (2016) 319–333 329
the other hand, Sánchez et al. [57] figured out something contradictorythat
conducting reaction withhigher temperature, better
conversion is obtained for all tested alcohols. But using methanol
or ethanol for biodiesel production, didn’t face any significant
effect on yield whereas n-butanol and 2-propanol were more
sensitive to temperature and catalyst percent changes,
respectively.