Page 230 - Advances in Eco-Fuels for a Sustainable Environment

194 Advances in Eco-Fuels for a Sustainable Environment

operating conditions, the pyrolysis process can be divided into three subclasses: con-
ventional pyrolysis, fast pyrolysis, and flash pyrolysis. Many researchers have studied
the pyrolysis of nonedible vegetable oils and their cakes such as Babassu, Karanja
(Pongamia pinnata), Jatropha curcas, Copra, mahua (Madhuca indica), and Tung.
Castor oil is one of the suitable alternative and renewable fuel for internal combustion
engine.

7.5.2 Microemulsification
Microemulsification is defined as a transparent, thermodynamically stable colloidal
˚
dispersion of the microstructure with diameter ranges from 100 to 1000 A. Micro-
emulsion can be made of vegetable oils with an ester and dispersant (co solvent) or
of vegetable oils, and alcohol such as ethanol, buthanol, hexanol, and a surfactant,
with or without diesel fuels. Microemulsification has been considered a reliable
approach to solve the problem of the high viscosity of vegetable oils [30].

7.5.3 Dilution
Nonedible oil can be diluted with diesel to reduce the viscosity and thus improve the
performance of the engine. No chemical process is required in this method.
According to this method, no 100% nonedible oil can be used directly as biofuel;
therefore 20%–25% of oil is blended with commercial diesel fuel, which has shown
considerably good results [30]. The use of blends of conventional diesel fuel with a
variety of nonedible oils such as rubber seed, turpentine, linseed, Putranjiva
roxburghii, cotton seed, Jatropha curcas,and Pongamia pinnata oil has been
described in the literature [30].

7.5.4 Transesterification (alcoholysis)
Transesterification or alcoholysis is defined as the process in which nonedible oil is
allowed to chemically react with alcohol. In this reaction, methanol and ethanol are the
most commonly used alcohols because of their low cost and availability. This reaction
has been widely used to reduce the viscosity of nonedible oil and for the conversion of
triglycerides into ester. Transesterification can be carried out in two ways: catalytic
transesterification and noncatalytic transesterification [30, 45]. It is widely known that
catalytic transesterification faces two problems. The main problem is the processes are
relatively time consuming and need separation of the oil, alcohol, catalyst, and sapon-
ified impurities mixture from the biodiesel [46]. Purification of biodiesel is much
easier as no catalyst is required during the supercritical transesterification process,
thus preventing soap formation or saponification from occurring. However, the draw-
backs of the supercritical alcohol transesterification process are the high temperature
and pressure that result in the high cost of the apparatus [47].