12-Phosphotungstic acid (PW) and cesium salt of PW supported on dealuminated ultra-stable Y zeolite (DUSY) with various loadings were prepared by impregnation method, and their physicochemical properties were characterized by X-ray powder diffraction (XRD), N-2 adsorption, solid state P-31 and Si-29 MAS NMR, Hammett indicator and SEM techniques. Their catalytic performances were evaluated in the liquid-phase acetalization of ethyl acetoacetate with ethylene glycol to fructone. The catalytic stability was tested using water treatment, in which the concentration of heteropoly compound was measured by ultraviolet-visual spectrophotometer. A high catalytic activity was found over the supported heteropoly compound catalysts. However, for the supported PW catalysts, a severe leaching of heteropoly anions into water was observed, leading to their poor reusability. By contrast, the Cs salt of PW catalyst supported on DUSY exhibited very high catalytic activity with high water-tolerance and reusability. The conversion of ethyl acetoacetate of 98.7% with the selectivity of fructone above 97% could be obtained over the DUSY supported sample containing 30% of Cs2.5H0.5PW12O40 by weight at the optimal reaction conditions, and a considerable catalytic activity still could be achieved after five times of reaction cycle. (c) 2005 Elsevier B.V. All rights reserved.