TITLE:
Synthesis and Characterization of Methanesulfonate and Ethanesulfonate Intercalated Lithium Aluminum LDHs
AUTHORS:
Anton Niksch, Herbert Pöllmann
KEYWORDS:
LDH, Lithium, Aliphatic Sulfonic Acid, X-Ray Powder Diffraction, High Temperature PXRD, Layered Double Hydroxides, Sulfonate
JOURNAL NAME:
Natural Resources,
Vol.12 No.3,
March
23,
2021
ABSTRACT: LDH-phases become increasingly interesting due to their broad ability to
be able to incorporate many different cations and anions. The intercalation of methanesulfonate
and ethanesulfonate into a Li-LDH as well as the behavior of the interlayer
structure as a function of the temperature is presented. A hexagonal P63/m
[LiAl2(OH)6][Cl?1.5H2O] (Li-Al-Cl) precursor LDH was
synthesized by hydrothermal treating of a LiCl solution with γ-Al(OH)3. This precursor was
used to intercalate methanesulfonate (CH3O3S?)
and ethanesulfonate (C2H5O3S?)
through anion exchange by stirring Li-Al-Cl in a solution of the respective
organic Li-salt (90?C, 12 h). X-ray diffraction pattern showed an
increase of the interlayer space c' (d001) of Li-Al-methanesulfonate
(Li-Al-MS) with 1.2886 nm and Li-Al-ethanesulfonate (Li-Al-ES) with 1.3816 nm
compared to the precursor with 0.7630 nm. Further investigations with
Fourier-transform infrared spectroscopy and scanning electron microscopy
confirmed a complete anion exchange of the organic molecules with the precursor
Cl?. Both synthesized LDH compounds [LiAl2(OH)6]CH3SO3?nH2O
(n = 2.24-3.72 (Li-Al-MS) and [LiAl2(OH)6]C2H5SO3}?nH2O
(n = 1.5) (Li-Al-ES) showed a monomolecular interlayer structure with
additional interlayer water at room temperature. By increasing the temperature,
the interlayer water was removed and the interlayer space c' of Li-Al-MS decreased to 0.87735 nm (at 55?C).
Calculations showed that a slight displacement of the organic molecules is
necessary to achieve this interlayer space. Different behavior of Li-Al-ES
could be observed during thermal treatment. Two phases coexisted at 75?C - 85?C, one with a reduced c' (0.9015 nm, 75?C) and one with increased c' (1.5643 nm, 85?C) compared to the LDH
compound at room temperature. The increase of c' is due to the formation of a bimolecular interlayer
structure.