Fractal Extra-Framework Species in De-aluminated LaY Zeolites and Their Catalytic Activity |
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Authors: | Pablo García Enrique Lima Julia Aguilar Víctor Lara |
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Affiliation: | 1. Universidad Autónoma Metropolitana, Azcapotzalco, Av. San Pablo 180, Col. Reynosa Tamaulipas, 02200, Mexico, DF, Mexico 2. Universidad Autónoma Metropolitana, Iztapalapa, Av. San Rafael Atlixco No. 186, 09340, Mexico, DF, Mexico
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Abstract: | Lanthanum-containing Y (LaY) zeolites were prepared by ionic exchange from NaY parent zeolite. The LaY zeolites were de-aluminated by steaming. De-aluminated zeolites presented different Si/Al ratio. The physicochemical properties of these catalysts were characterized by X-ray diffraction, pyridine and xenon adsorption, infrared spectroscopy and 29Si, 27Al, 129Xe, 139La solid-state nuclear magnetic resonance spectroscopy. Furthermore, a fractal geometry approach was adopted to describe the evolution in the texture as a consequence of de-alumination. The catalytic properties of materials were evaluated in the n-hexane cracking reaction. The catalyst with the highest catalytic activity was the zeolite highest de-aluminated (Si/Al ratio of 3.7). Such performance was attributed on the one hand, to active extra-framework aluminum species hosted in the large cavities of zeolites and, on the other hand to redistribution of lanthanum species into the zeolite as a consequence of de-alumination. |
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