Transesterification of triolein in excess methanol over sodium-loaded catalysts prepared from Na-ion exchange with zeolites at a relatively lower reaction temperature, namely, at 60 degrees C, is studied in this work. Two zeolites, i.e., as-synthesized Zeolite MCM-22 and commercial Zeolite HY (CBV-780), are employed in this study. Although both zeolites show to some extent the capability of catalyzing transesterification of triolein in methanol to biodiesel, the resulting yields are only ca. 90% for CBV-780 after a 40-h reaction and 16.3% for MCM-22 after a 90-h reaction. In contrast, the conversion yields are much improved with Na-ion exchange to the surface of zeolite catalysts. For example, the yields of triolein to biodiesel have reached 98% and 99% within a 5.5-h reaction, respectively, using the NaOH-treated CBV-780 and MCM-22 catalysts, even if these NaOH-treated catalysts become amorphous and have suffered a loss of the Brunauer-Emmett-Teller surface area. Furthermore, no saponification was observed using these NaOH-treated catalysts.