Page 279 - Biosystems Engineering

Biodiesel and Ethanol in Engines 257

oils are degummed by phosphoric acid. The quantity of the acid
required during this process is very important in optimizing results
21
such as reduction of viscosity. Three percent phosphoric acid is
mixed with oil at 40°C with vigorous stirring. After being stirred for
half an hour, the mixture is kept for 1 week so that the reacted gum
materials may settle. Solid gum materials that can be used as soil fer-
tilizer are separated by decantation, and the degummed oil is washed
3 times to remove the remaining acid followed by filtering through a
packed bed that is filled by activated carbon. The filtered oil is then
ready for transesterification. 21
Generally, transesterification of vegetable oils is done by acid,
base, and enzyme catalysts. Preparation of biodiesel is optimized
through a series of reactions. In the transesterification process the oil
(4.0 g) is poured into a three-necked round-bottom flask and is heated,
for 1 hour at a temperature of 100°C, with continuous stirring, to
remove excess moisture. In the acid-catalyzed process, sulphuric acid
(1 percent of oil and methanol) is mixed well with methanol. Oil is
poured into a round-bottom flask that is fitted with a thermometer and
a condenser; the flask is then placed on a magnetic stirrer. The acid–
methanol mixture is added slowly in the flask. The methanol–catalyst
solution is kept for 2 hours at 67°C with vigorous stirring. The mix-
ture is cooled by ice water. Two layers are formed in which the upper
layer is the product layer and the lower layer is the glycerol layer. The
upper layer is placed into a separating flask and is washed 3 times
with distilled water to remove the acid and the methanol. The washed
oil is stirred with anhydrous sodium sulfate and is kept for 3 hours at
room temperature for dehydration. The dehydrated oil is used for its
properties, performance, and emission measurement.
In a base-catalyzed process, sodium methoxide (1.5 percent, that
is, w/w of the total reactant) is put in the methanol and then is dis-
solved by stirring. The solution is added slowly in the oil present in
the round-bottom flask. The reaction procedure and purification of
the product are done similar to the acid process.
In the enzymatic process, specified ratios of oil and methanol are
poured into a conical flask fitted with a standard joint-stoppered
cock. The enzyme, Candida antarctica, is taken as 1 percent (w/w) of
the oil as the catalyst. The conical flask is placed in an incubator
shaker for stirring at 600 rpm. The reaction mixture is drawn out after
a specified duration of time and is filtered to remove the catalyst.
Then, the product is washed with water to remove the methanol and
the glycerol immediately. The washed product is treated with anhy-
drous sodium sulfate for 2 hours to remove excess moisture.

8.1.2 Analyzing the Products
The fatty acid compositions of nonedible oils and their transesterified
products can be analyzed by a CN10543004 gas chromatograph
(Restek International, Bellefonte, Pennsylvania) with a flame-ionization