Hierarchical USY Zeolites for Removing of Trace Olefins from Aromatics : Effect of Acid Leaching in the Dealumination of Zeolites

Hierachical USY zeolite prepared by citric acid treatment was demonstrated to be an effective catalyst for removing trace olefins from aromatics with the suitable ratio of Lewis/Brønsted acid. The samples were investigated by X-ray diffraction, N₂ adsorption, and fourier transform infrared spectroscopy. The results indicated that the mesopores might be generated by skeletal reconstruction and the AlO⁺ change the distribution of acid sites in the samples. It can improve the catalytic activity by facilitating diffuse out the polyaromatic components and thus avoided the coke formation. Optimization of pores and acid sites of ultrastabilized USY zeolite modified with citric acid might result in an industrial process to design novel catalysts for removing trace olefins.