Fractal Extra-Framework Species in De-aluminated LaY Zeolites and Their Catalytic Activity
Fractal Extra-Framework Species in De-aluminated LaY Zeolites and Their Catalytic Activity
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DOI：
10.1007/s10562-008-9761-5
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发表时间：
2009
影响因子：
2.8
通讯作者：
P. Garcia;E. Lima;J. Aguilar;V. Lara
中科院分区：
文献类型：
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作者：
P. Garcia;E. Lima;J. Aguilar;V. Lara
以NaY分子筛为原料，采用离子交换法合成了含镧Y（LaY）分子筛。通过蒸汽使LaY沸石脱铝。脱铝沸石呈现不同的Si/Al比。采用X射线衍射、吡啶和氙吸附、红外光谱和29 Si、27 Al、129 Nd、139 La固体核磁共振等方法对催化剂的物化性质进行了表征。此外，采用分形几何方法来描述作为脱铝的结果在织构的演变。在正己烷裂解反应中评价了材料的催化性能。催化活性最高的催化剂是脱铝最高的沸石（Si/Al比为3.7）。这种性能一方面归因于沸石大空腔中的活性骨架外铝物种，另一方面归因于脱铝导致镧物种重新分布到沸石中。
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 and29Si,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.