Page 357 - Advances in Eco-Fuels for a Sustainable Environment

312 Advances in Eco-Fuels for a Sustainable Environment

Then the seeds were crushed in a household mixer-grinder and sieved to a particle size
less than 0.75mm.
Ultrasonic-assisted extraction is one of the oil extraction techniques from the ker-
nel. In this, an ultrasonic sonicator (Lark Innovative Teknowledge, India) with a max-
imum output power of 900W Model 650Y was used. The extraction process was
carried out with 100g of seeds that were taken in a beaker and mixed with acetone:
heptane (400mL) solvent at 35% of ultrasonic output power. The operating temper-
ature was maintained to below 40°C using an ice bath to prevent solvent evaporation.
After 20min extraction time, the mixture of solvent-oil was separated from the solid
seed powder by gravity filtration. Finally, the solvents were distilled in the rotatory
evaporator at 95°C and then crude AMC oil was obtained and stored in an airtight
container for further processes.

11.2.3 Biodiesel synthesis
The free fatty acid value of oil is the deciding parameter to proceed with one-step or
two-step transesterification process. If the acid value of oil is greater than 1.0mg
KOH/g oil, the two-step transesterification process is required for the conversion
of oil into biodiesel and to prevent saponification. The AMC crude oil acid value
was measured 2.5mg KOH/g oil, so two-step microwave-assisted transesterification
was chosen. The microwave system Cata-R Model (Catalyst System, India) consists
of a magnetic stirrer, a temperature control system, and a reflux condenser that allows
continuous stirring and constant temperature control.

11.2.3.1 Acid-catalyzed transesterification

Acid-catalyzed transesterification was carried out in a two-neck, flat-bottom glass
reactor (500mL) with a sample of 30% of the reactor volume. After the oil temper-
ature reached 60°C, the stoichiometric ratio of methanol (6:1) and 0.5% (wt/wt) of an
acid catalyst (HCl) were poured into the glass reactor. The reaction process was car-
ried out for 20min with a continuous stirring speed of 650rpm. The products were
shifted to a separating funnel after the accomplishment of the process and allowed
to form two distinct layers. The top layer contained the excess methanol and acid cat-
alyst and the bottom layer contained esterified oil. The bottom layer was collected and
several times washed with warm water to remove impurities and right after, the meth-
anol was recovered by the rotatory evaporator.

11.2.3.2 Base-catalyzed transesterification

Base-catalyzed transesterification was performed in the same manner as the acid-
catalyzed process except for the catalyst and process conditions. The reaction was car-
ried out with oil, a sodium methoxide catalyst (1% wt/wt), and stoichiometry meth-
anol (1:6) at 60°C for 20min. After attainment of the process, the products were
discharged to a separating funnel to form two dissimilar layers. The top layer consists
of biodiesel and excess methanol. The bottom layer consists of glycerol and base