Optimization of sodium loading on zeolite HY for catalyzed transesterification of triolein in excess methanol to biodiesel was studied. Zeolite HY catalyst was activated by loading sodium ions to their surface via an ion-exchange method. The effects of ion-exchange process parameters, including the temperature, the process time, the pH value, as well as concentrations and sources of Na+ cations (NaOH, NaCl and Na-2 SO4), on the conversion yield of triolein to biodiesel were investigated. Most of these Na+-activated zeolite HY catalysts could really facilitate the catalyzed transesterification reaction of triolein to biodiesel at a lower temperature near 65 degrees C. Consequently, a high conversion yield of triglycerides to biodiesel at 97.3% was obtained at 65 degrees C. Moreover, the durability of zeolite catalysts was examined as well. Catalytic performance tests of these zeolite catalysts in transesterification did not show a significant decrease in catalysis at least for three batch cycles. (C) 2013 Elsevier Ltd. All rights reserved.