The effect of reduction temperature on ceria-promoted platinum and platinum-zinc catalysts supported on silica has been studied on catalysts prepared from chlorine-free precursors and characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS). Their catalytic behavior has been evaluated in the vapor-phase hydrogenation of toluene and of crotonaldehyde (2-butenal), after reduction at low (473 K) and high (773 K) temperatures. Catalytic results in the selective hydrogenation of crotonaldehyde show that the presence of Zn produces a fivefold increase in catalytic activity after high-temperature reduction over that with the monometallic catalyst. This promoting effect is accompanied with an increase in the selectivity for the C=O double bond hydrogenation to yield the corresponding unsaturated alcohol, crotyl alcohol (2-buten-1-ol).