In order to further affirm the presence of acid sites in CL8.0,
acidity of catalyst was analyzed by using TPD-NH3 technique. The
NH3-TPD profile (Fig. 6) showed that the catalysts (La2O3 and CL8.0)
had distinct desorption peak at Tmax of >500 C, indicating the
presence of strong acid sites for both catalysts. Once again, it proved
that binary system of CaOeLa2O3 rendered higher acidity
(287.05 mmol of NH3/g) than individual La2O3 catalyst (186.72 mmol
of NH3/g). This is due to the presence of synergism effect between
CaO and La2O3. The unique cooperative action of acidebase sites
from CaeOeLa, CaeOeCaeO and LaeOeLaeO bonds render a
simultaneous esterificationetransesterification reaction for biodiesel
production. This is in agreement with the studies above
(Table 4), where the presence of FFA in oil was esterifies into ester
products.