Several polymers with ion exchanging groups showing acidic strength comparable with that of "concentrated" sulfuric acid were used to prepare silica-heterogenized perfluorosulfonic (PFS) acid catalysts by either incipient wetness impregnation of commercial silicas or sal-gel and precipitation routes. Solid-acid catalysts were probed in the synthesis of acetal at 4 degrees C and 3 atm in a stirred batch reactor. A systematic analysis of activity data and the acid strength of the various catalysts points out a direct relationship between the acidic capacity and catalytic activity, pointing out a minor influence of the strength distribution on the main reaction path. (C) 2009 Elsevier B.V. All rights reserved.