The Meerwein-Ponndorf-Verley (MPV) reduction of crotonaldehyde to but-2-enol was conducted in the presence of ZrO2 based catalysts modified by impregnation with gold, cobalt, nickel or zinc chloride. The resulting solids were characterized in depth and used as catalysts in the previous reaction, where they provided high but-2-enol yields at the expense of a considerable loss of activity with time on stream. The catalysts were found to contain both Bronsted and Lewis acid sites active in the reaction. Based on the results, however, the Lewis sites are much more active but undergo much stronger deactivation than the Bronsted sites. Judging by the reactivity and characterization of the spent catalysts, the Bronsted sites are seemingly more selective despite their lower activity. Modifying ZrO2 with metal chlorides enhanced the surface Lewis acidity although these sites were found to be responsible for the surface deposition of carbonaceous species leading to catalyst deactivation. The presence in the Au/ZrO2 catalyst of a type of Lewis acid sites that scarcely deactivates in the process might be related to the presence of metallic Au particles interacting with chlorinated species. (C) 2013 Elsevier B.V. All rights reserved.