Epoxidation of allyl acetate was carried out over MoO3/alpha-Al2O3 using tert-butyl hydroperoxide (TBHP) as an oxidizing reagent. Only a small amount of glycidyl acetate was formed. The low yield was due to the cleavage of an epoxy-ring of glycidyl acetate with the acid sites of MoO3/alpha-Al2O3. The acid sites were neutralized with amines to keep the glycidyl acetate intact during the reaction. Pyridine derivatives greatly improved epoxide selectivity, but addition of aliphatic amines and 2,2'-bipyridine only resulted in retardation of the reaction. The volcano-type plot of Hammett's p-substituent constant versus epoxide selectivity indicated that pyridine derivative also exerts a ligand effect, and non-substituted pyridine was found to the most suitable additive. The optimum amount of loading Of MoO3 was 2 wt.%; at this value, MoO3 was highly dispersed on alpha-Al2O3. The optimum molar ratio of pyridine to MoO3 for epoxide production was 2/3. (C) 2004 Elsevier B.V. All rights reserved.