Journal
MICROPOROUS AND MESOPOROUS MATERIALS
Volume 252, Issue -, Pages 79-89Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.micromeso.2017.05.036
Keywords
Amino acid; Mesoporous zeolite; LTA zeolite; Hydrothermal synthesis
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Funding
- National Natural Science Foundation of China [11325420, 21671010]
- Guangdong Science and Technology Program [2013A061401002]
- Shenzhen Strategic Emerging Industries [CXZZ20140419131807788, KQCX2015032709315529, GJHS20150918111107883]
- Nanshan District Energy Saving Program [FG2014JNYF0017A]
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Hydrothermal crystallization of LTA zeolite has been conducted in the presence of amino acid in order to introduce mesoporosity. Eight different types of proteinogenic amino acids have been employed. The influence of their structure and physicochemical properties on the formation of hierarchically mesoporous LTA (MLTA) zeolite have been investigated. All eight amino acids bearing either basic, or acidic, or polar non-ionizable, or non-polar non-ionizable side chains were able to generate mesopores within LTA crystals. The isoelectric points of amino acids influenced the resulting MLTA's morphology, crystallization kinetics, and impurity content. Pure phase MLTA with controllable shape was obtained. Amino acid with a higher isoelectric point generated smaller and more spherical MLTA in less crystallization time, but induced slightly more impurity FAU phase. The mesopore size generally decreased with hydropathy index so that amino acids with non-polar, non-ionizable side groups generated 14-15 nm mesopores, 5 10 nm smaller than those generated by amino acids in other categories. The hydrophobic moieties in amino acids tended to shrink the mesopores, in contrast with their pore expansion effect in surfactant mediated mesopore generation route, suggesting a different mesopore formation mechanism. Stability of amino acid during the hydrothermal zeolite synthesis and easy amino acid removal by washing with water was further confirmed. The findings discovered in this study paves a new way for tailoring hierarchical zeolite materials with controlled texture properties. (C) 2017 Elsevier Inc. All rights reserved.
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