Demonstration of Improved Effectiveness Factor of Catalysts Based on Hollow Single Crystal Zeolites

Pt/NaY zeolites with bulk and hollow morphologies have been used as model catalysts in the hydrogenation of cyclohexene as model reaction. In contrast to most hierarchical zeolites, the presence of a single internal cavity modifies only the mean diffusion length, without changing the external surface area and the crystal size. Differences in catalytic activities have been attributed to a shorter diffusion length in hollow crystals. The volume fraction of zeolite used in bulk crystals (ca. 0.63-0.70) matches well with the shell thickness in hollow crystals, leading to an efficiency factor value for the latter close to 1.