Investigating the Effects of Guest–Host Interactions on the Properties of Anion-Exchanged Mg–Al Hydrotalcites

✍ Scribed by François Malherbe; Jean-Pierre Besse

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 249 KB
• Volume: 155
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2000.8922

✦ Synopsis

A starting [Mg+Al+Cl] LDH, prepared by coprecipitation, was further anion-exchanged to incorporate a variety of anions in the interlayer domain: (Fe(CN) 6 ) 3؊ , (P 2 O 7 ) 4؊ , (V 2 O 7 ) 4؊ , (CrO 4 ) 2؊ , and (Cr 2 O 7 ) 2؊ . The resulting materials were fully characterized using classical techniques like XRPD, FTIR, TGA/DTA, and BET, and their structural modi5cations studied as a function of calcination temperatures. Under mild calcination, only the oxo-anions were shown to interact strongly with the host matrix. This resulted in a systematic shrinkage of the interlamellar domain, with a negative impact on the surface properties. However, intercalation of oxo-anions proved to be bene5cial to thermal stability, the lamellar structure being maintained up to 4003C in the case of the dichromate intercalated [Mg+Al]. A thorough analysis of the FTIR spectra, revealing an evolution in the symmetry of some oxo-anions, con5rmed the occurrence of a grafting process. Furthermore, the permanent character of the pillars was evidenced through unsuccessful rehydration and back-exchange reactions.