Niobium oxide (Nb2O5) supported on alpha-alumina (alpha-Al2O3) prepared by impregnation was studied for hydration of ethylene oxide. The effects of mobium oxide loadings, calcination temperature and molar ratio of water to ethylene oxide (EO) on the reaction performance were investigated. The structure and acidity of the catalysts were characterized by using X-ray diffraction (XRD), differential thermal analysis (DTA)-thermogravimetric (TG) and infrared (IR) of pyridine adsorption. A durability test of niobic acid and Nb2O5/alpha-Al2O3 catalyst was carried out over a period of 1000 h. It was found that Nb2O5/alpha-Al2O3 demonstrated very high activity and selectivity for hydration of ethylene oxide to monoethylene glycol (MEG) under mild conditions. Compared with the result of non-catalytic reactions, the conversion of ethylene oxide was increased from 34 to 99.8% on keeping monoethylene glycol selectivity almost unchanged when the hydration was carried out over 10 wt.%Nb2O5/alpha-Al2O3 catalyst. The yield of monoethylene glycol over Nb2O5/alpha-Al2O3 was higher than that obtained over other solid acid catalysts. Moreover, the supported niobia catalyst demonstrated excellent stability and no deactivation was observed within 1000 h of time-on-stream. (C) 2004 Elsevier B.V. All rights reserved.