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The effect of acid treatment on the structure and surface acidity of tetraalkylammonium-montmorillonites.
MedLine Citation:
PMID:  23332795     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
The effect of tetrabutylammonium (Bu(4)N(+)) and tetrapentylammonium (Pe(4)N(+)) cations on the modification of the organo-montmorillonite structure upon acid-treatment was investigated. Samples were treated with HCl for various times (2-12h). Structural changes were followed by MAS NMR spectroscopy. The (29)Si MAS NMR spectra of initial Na-saturated form (Na-SAz) showed gradual decrease of the intensity of the resonance assigned to SiO(4) cross-linked in the tetrahedral sheets Q(3)(0Al) while signals arising from the reaction product Q(3)1OH and Q(4)(0Al) became more pronounced upon acid treatment. The Q(3)(0Al) signal almost completely disappeared for Na-SAz treated for 8h on contrary to Bu(4)N-SAz and Pe(4)N-SAz showing signal of relatively high intensity even after 12h. The (27)Al MAS NMR measurement proved that more than one half of Al remained in the reaction product of Bu(4)N-SAz and Pe(4)N-SAz after 8h treatment, while Al content dropped below 5% for Na-SAz. Formation of acid sites was investigated via pyridine adsorption. Only physically adsorbed and H-bonded pyridine was detected for acid-untreated samples. In contrast, the IR spectra of the samples partially decomposed in HCl revealed bands of pyridine adsorbed on Brønsted acid sites. Strongly bonded pyridine was able to bear up heating even at 230°C.
Authors:
Helena Pálková; Viktor Hronský; L'uboš Jankovič; Jana Madejová
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-12-19
Journal Detail:
Title:  Journal of colloid and interface science     Volume:  -     ISSN:  1095-7103     ISO Abbreviation:  J Colloid Interface Sci     Publication Date:  2012 Dec 
Date Detail:
Created Date:  2013-1-21     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0043125     Medline TA:  J Colloid Interface Sci     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2012 Elsevier Inc. All rights reserved.
Affiliation:
Institute of Inorganic Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, 845 36 Bratislava, Slovakia. Electronic address: helena.palkova@savba.sk.
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