Effect of MgAl2O4 on the structure, acidity as well as the catalytic performance of Nb2O5/alpha-Al2O3 catalyst for ethylene oxide hydration was studied using IR, XRD, NH3-TPD, CO2-TPD and catalytic reaction. Modification of alpha-Al2O3 support with MgAl2O4 led to an increase in both basicity and mechanical strength of the support. As a result, the density and strength of the acidity of the niobium oxide catalyst supported on the MgAl2O4 modified alpha-Al2O3 reduced in comparison with that supported on the pure alpha-Al2O3. The acidity of 10% Nb2O5/MgAl2O4/alpha-Al2O3 decreased with increasing loading of MgAl2O4. Catalytic test showed that EO conversion decreased monotonously with increasing MgAl2O4 loading, whereas the selectivity to MEG exhibited a maximum of 90.6% at MgAl2O4 loading of 2.23%. In terms of MEG yield, optimal MgAl2O4 loading should be around 2%. Durability test demonstrated that 10% Nb2O5/MgAl2O4/alpha-Al2O3 catalyst exhibited excellent stability within 1000 h time-on-stream. (C) 2004 Elsevier B.V. All rights reserved.