Impact of Iron Deposition on Pd/δ-Al₂O₃ in Selective Hydrogenation of Pyrolysis Gasoline

Abstract

In selective hydrogenation of pyrolysis gasoline, Pd/Al 2 O 3 is often deposited with iron species due to corrosion of equipment. The impact of deposited iron on the Pd/Al 2 O 3 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 Fe 2 O 3 −Pd/Al 2 O 3 in hydrogenation of pyrolysis gasoline, the deposited iron is shown to increase isoprene conversion, olefin selectivity, and coke formation. TPD (temperature-programmed desorption) of NH 3 and TPR results indicate that the deposited iron is in the form Fe 2 O 3, 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.