Synthesis of biodiesel
The simultaneous transesterification and esterification of WCO
containing 15 wt.% free fatty acids was carried out using prepared
solid acid catalysts in a 500 cc Parr reactor (Parr Instrument Co.)
equipped with a temperature controller. Initially the reactor was
charged with 100 g of WCO and heated to a temperature of 50 8C.
Anhydrous methanol and catalyst were then added to the reaction
vessel and the temperature was increased to 200 8C and stirring
speed of 600 rpm optimized previously [8]. To ensure that at
the reaction temperature the reactants were in the liquid phase,
the reactor was pressurized to 600 psig with nitrogen gas. The
reactions were carried out for a period of 10 h unless otherwise
stated. The products were analyzed using gel permeation
chromatography (GPC) equipped with a RI detector and two
300 mm 7.8 mm phenogel columns connected in series. Tetrahydrofuran
(THF) was used as a mobile phase and the triglycerides,
diglycerides, monoglycerides and methyl esters in the product
were quantified by comparing the peak areas of their corresponding
standards. The percentage free fatty acid content was
determined from the acid value following the AOCS method Te
1a-64.