based transesterification, sodium hydroxide, potassium hydroxide, carbonates, and
some sodium and potassium alkoxides, i.e. sodium methoxide, sodium ethoxide,
sodium propoxide, and sodiumbutoxide are used as alkali catalysts (Brennan and
Owende 2010). The commonly used acid catalysts are sulfuric acid, sulfonic acids,
and hydrochloric acid. Lipases also can be used as biocatalysts. Alkali catalyzed
transesterification is much superior in use than acid catalyzed transesterification due
to fast reaction. In case of high acid value of oil, acid catalyst is preferred. Some
important parameters that affect the rate of transesterification reaction are: reaction
temperature, type and amount of catalyst, stirring intensity, ratio of alcohol to oil,
quality, and water content. After transesterification, quality of biodiesel can be
improved by repeated washing with water to remove glycerol and methanol. Use
of lipases offers important advantages, but its high cost is not currently feasible.
Lipases can be obtained from Rhizomucor miehei, Rhizopus oryzae, Candida
antarctica, Candida rugosa, Pseudomonas cepacia, and Thermomyces lanuginosus.
The commercial immobilized lipase isolated from C. antarctica (Novozym 435) is
also commonly used. Instead of using methanol, the lipase catalyzed synthesis of
FAME can also be performed using alternative alcohol donors such as methyl (alkyl)
acetate or dimethyl carbonate. The process of such a biodiesel synthesis is irreversible because the intermediate compound (carbonic acid monoacyl ester) immediately
decomposes to carbon dioxide and an alcohol.
1.4.2 Reactive Distillation Technique
It is a modeling transesterification reaction with a reactive distillation column. Two
processes such as transesterification reaction and the separation of the subsequent
products take place within the same unit operation during reactive distillation. It is a
more effective separation technique which aimed to maximize biodiesel yield
(Mueanmas et al. 2010). This helps in reduction in capital cost which is important
for sustainable development. It also offers higher conversion of oil to biodiesel with
low energy consumption and solvents elimination during process.
1.4.3 Supercritical Fluid Technique
It is environment friendly, fast separation technique. Under this technique, alcoholic
polarity and its dielectric constant are reduced. At this condition, alcohol can solvate
triacylglyceride and form an oil/alcohol mixture which coexist in a single phase.
This can yield free fatty acid alkyl esters (Saka and Kusdiana 2001).
1.4.4 Microemulsion Technique
Viscosity and other atomization problems of oil can be solved by microemulsion
method (Vivekpantidar et al. 2014). It is a thermodynamically stable, transparent
12
N. Maheshwari et al.
some sodium and potassium alkoxides, i.e. sodium methoxide, sodium ethoxide,
sodium propoxide, and sodiumbutoxide are used as alkali catalysts (Brennan and
Owende 2010). The commonly used acid catalysts are sulfuric acid, sulfonic acids,
and hydrochloric acid. Lipases also can be used as biocatalysts. Alkali catalyzed
transesterification is much superior in use than acid catalyzed transesterification due
to fast reaction. In case of high acid value of oil, acid catalyst is preferred. Some
important parameters that affect the rate of transesterification reaction are: reaction
temperature, type and amount of catalyst, stirring intensity, ratio of alcohol to oil,
quality, and water content. After transesterification, quality of biodiesel can be
improved by repeated washing with water to remove glycerol and methanol. Use
of lipases offers important advantages, but its high cost is not currently feasible.
Lipases can be obtained from Rhizomucor miehei, Rhizopus oryzae, Candida
antarctica, Candida rugosa, Pseudomonas cepacia, and Thermomyces lanuginosus.
The commercial immobilized lipase isolated from C. antarctica (Novozym 435) is
also commonly used. Instead of using methanol, the lipase catalyzed synthesis of
FAME can also be performed using alternative alcohol donors such as methyl (alkyl)
acetate or dimethyl carbonate. The process of such a biodiesel synthesis is irreversible because the intermediate compound (carbonic acid monoacyl ester) immediately
decomposes to carbon dioxide and an alcohol.
1.4.2 Reactive Distillation Technique
It is a modeling transesterification reaction with a reactive distillation column. Two
processes such as transesterification reaction and the separation of the subsequent
products take place within the same unit operation during reactive distillation. It is a
more effective separation technique which aimed to maximize biodiesel yield
(Mueanmas et al. 2010). This helps in reduction in capital cost which is important
for sustainable development. It also offers higher conversion of oil to biodiesel with
low energy consumption and solvents elimination during process.
1.4.3 Supercritical Fluid Technique
It is environment friendly, fast separation technique. Under this technique, alcoholic
polarity and its dielectric constant are reduced. At this condition, alcohol can solvate
triacylglyceride and form an oil/alcohol mixture which coexist in a single phase.
This can yield free fatty acid alkyl esters (Saka and Kusdiana 2001).
1.4.4 Microemulsion Technique
Viscosity and other atomization problems of oil can be solved by microemulsion
method (Vivekpantidar et al. 2014). It is a thermodynamically stable, transparent
12
N. Maheshwari et al.