Catalyst Design by NH4OH Treatment of USY Zeolite |
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| Authors: | Joost Van Aelst Danny Verboekend An Philippaerts Nicolas Nuttens Mert Kurttepeli Elena Gobechiya Mohamed Haouas Sreeprasanth P Sree Joeri F M Denayer Johan A Martens Christine E A Kirschhock Francis Taulelle Sara Bals Gino V Baron Pierre A Jacobs Bert F Sels |
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| Affiliation: | 1. Centre for Surface Chemistry and Catalysis, KU Leuven, Heverlee, Belgium;2. EMAT, University of Antwerp, Antwerp, Belgium;3. Institut Lavoisier de Versailles, University of Versailles Saint Quentin en Yvelines, Tectospin, Versailles CEDEX, France;4. Department of Chemical Engineering, Vrije Universiteit Brussel, Brussels, Belgium |
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| Abstract: | Hierarchical zeolites are a class of superior catalysts which couples the intrinsic zeolitic properties to enhanced accessibility and intracrystalline mass transport to and from the active sites. The design of hierarchical USY (Ultra‐Stable Y) catalysts is achieved using a sustainable postsynthetic room temperature treatment with mildly alkaline NH4OH (0.02 m ) solutions. Starting from a commercial dealuminated USY zeolite (Si/Al = 47), a hierarchical material is obtained by selective and tuneable creation of interconnected and accessible small mesopores (2–6 nm). In addition, the treatment immediately yields the NH4+ form without the need for additional ion exchange. After NH4OH modification, the crystal morphology is retained, whereas the microporosity and relative crystallinity are decreased. The gradual formation of dense amorphous phases throughout the crystal without significant framework atom leaching rationalizes the very high material yields (>90%). The superior catalytic performance of the developed hierarchical zeolites is demonstrated in the acid‐catalyzed isomerization of α‐pinene and the metal‐catalyzed conjugation of safflower oil. Significant improvements in activity and selectivity are attained, as well as a lowered susceptibility to deactivation. The catalytic performance is intimately related to the introduced mesopores, hence enhanced mass transport capacity, and the retained intrinsic zeolitic properties. |
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| Keywords: | hierarchical zeolite USY alkaline treatment NH4OH catalysis |
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