Thermal intercalation of layered double hydroxides: capric acid into an Mg–Al LDH
- 1 January 1995
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of Materials Chemistry
- Vol. 5 (9), 1433-1442
- https://doi.org/10.1039/jm9950501433
Abstract
Molten decanoic acid, capric acid, reacted with the layered double hydroxide (LDH) of initial composition Mg6Al3.4(OH)18.82(CO3)1.51(NO3)0.36·4.5 H2O, at a temperature of 150 °C using a heating rate of 1 °C min–1. Powder X-ray diffraction (PXRD) showed that the reaction products were microcrystalline. The polyphasic nature of the reaction products was thought to derive from the presence, in all cases, of some residual unreacted LDH host plus mono- and bi-layers of caprate anion guests in the LDH. Typically, dominant phases were non-intercalated LDH (at initial capric acid:LDH ratios of up to 2:1); stacks of horizontal caprate anions (4:1); full, intercalated monolayers (6:1) and full bilayers (8:1). 27Al Solid-state magic-angle spinning nuclear magnetic resonance (MAS NMR) studies indicated that the exclusively octahedral nature of the aluminium sites of the host LDH were not altered by thermal reaction with capric acid. Two-dimensional (2D)27Al MAS NMR suggested that the thermal reaction products contained two octahedral aluminium environments. 13C MAS NMR confirmed the presence of the monoanion of capric acid, CH3(CH2)8COO–. The suggested mechanism for intercalation involves the removal of the LDH interlayer carbonate in a similar manner to that observed in the corresponding LDH-sebacic acid thermal reactions. The products of the thermal reaction were compared with material prepared via a modified coprecipitation reaction. PXRD suggested that the products of this coprecipitation reaction and the 8:1 thermal reaction product contained bilayers having similar calculated slant angles. 2D 27Al MAS NMR suggested that the coprecipitated reaction differed from the thermal reaction products in that it contained a tetrahedral aluminium site in addition to the two octahedral sites also exhibited by the thermal reactions. There was no direct evidence of kinking of the acid or anion carbon chains in the thermal or coprecipitation reaction products owing to possible interaction with the alcohol during washing of the products.Keywords
This publication has 18 references indexed in Scilit:
- Reaction of molten sebacic acid with a layered (Mg/Al) double hydroxideJournal of Materials Chemistry, 1994
- Composition and Properties of Synthetic HydrotalcitesClays and Clay Minerals, 1992
- Inorganic and Organic Anionic Pillars Intercalated in Lamellar Double HydroxidesMaterials Science Forum, 1992
- Thermal characteristics of a synthetic hydrotalcite-like materialJournal of Materials Chemistry, 1992
- Dynamics and ordering of intercalated water in layered metal hydroxidesThe Journal of Physical Chemistry, 1989
- Intercalation of organic and inorganic anions into layered double hydroxidesJournal of the Chemical Society, Chemical Communications, 1989
- Synthesis of isopolymetalate-pillared hydrotalcite via organic-anion-pillared precursorsInorganic Chemistry, 1988
- Synthesis of anionic clay minerals (mixed metal hydroxides, hydrotalcite)Solid State Ionics, 1986
- The nature of the thermal decomposition of a catalytically active anionic clay mineralJournal of Catalysis, 1986
- Crystal structures of some double hydroxide mineralsMineralogical Magazine, 1973