In selective hydrogenation of pyrolysis gasoline, Pd/Al2O3 is often deposited with iron species due to corrosion of equipment. The impact of deposited iron on the Pd/Al2O3 is examined. TPR (temperature-programmed reduction) results suggest that the clusters of deposited iron remain segregated from Pd clusters. By use of a model of Fe2O3-Pd/Al2O3 in hydrogenation of pyrolysis gasoline, the deposited iron is shown to increase isoprene conversion, olefin selectivity, and coke formation. TPD (temperature-programmed desorption) of NH3 and TPR results indicate that the deposited iron is in the form Fe2O3, which increases the acidity of the catalyst. The increased acidity promotes coke formation. Excess coke formation leads to high-pressure drops and eventually bed plugging.