Surface and interlayer base-characters in lepidocrocite titanate: The adsorption and intercalation of fatty acid

Journal Article · Wed Jun 15 00:00:00 EDT 2016 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/J.JSSC.2016.03.030· OSTI ID:22584117

Maluangnont, Tosapol ^[1]; Arsa, Pornanan ^[2]; Limsakul, Kanokporn; Juntarachairot, Songsit; Sangsan, Saithong ^[3]; Gotoh, Kazuma ^[4]; Sooknoi, Tawan ^[2]

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1. College of Nanotechnology, King Mongkut's Institute of Technology Ladkrabang, Bangkok 10520 (Thailand)
2. Catalytic Chemistry Research Unit, Faculty of Science, King Mongkut's Institute of Technology Ladkrabang, Bangkok 10520 (Thailand)
3. Department of Chemistry, Faculty of Science, King Mongkut's Institute of Technology Ladkrabang, Bangkok 10520 (Thailand)
4. Graduate School of Natural Science & Technology, Okayama University, 3-1-1 Tsushima-naka, Okayama 700-8530 (Japan)

While layered double hydroxides (LDHs) with positively-charged sheets are well known as basic materials, layered metal oxides having negatively-charged sheets are not generally recognized so. In this article, the surface and interlayer base-characters of O{sup 2−} sites in layered metal oxides have been demonstrated, taking lepidocrocite titanate K{sub 0.8}Zn{sub 0.4}Ti{sub 1.6}O{sub 4} as an example. The low basicity (0.04 mmol CO{sub 2}/g) and low desorption temperature (50–300 °C) shown by CO{sub 2}− TPD suggests that O{sup 2−} sites at the external surfaces is weakly basic, while those at the interlayer space are mostly inaccessible to CO{sub 2}. The liquid-phase adsorption study, however, revealed the uptake as much as 37% by mass of the bulky palmitic acid (C{sub 16} acid). The accompanying expansion of the interlayer space by ~0.1 nm was detected by PXRD and TEM. In an opposite manner to the external surfaces, the interlayer O{sup 2−} sites can deprotonate palmitic acid, forming the salt (i.e., potassium palmitate) occluded between the sheets. Two types of basic sites are proposed based on ultrafast {sup 1}H MAS NMR and FTIR results. The interlayer basic sites in lepidocrocite titanate leads to an application of this material as a selective and stable two-dimensional (2D) basic catalyst, as demonstrated by the ketonization of palmitic acid into palmitone (C{sub 31} ketone). Tuning of the catalytic activity by varying the type of metal (Zn, Mg, and Li) substituting at Ti{sup IV} sites was also illustrated. - Graphical abstract: Interlayer basic sites in lepidocrocite titanate, K{sub 0.8}Zn{sub 0.4}Ti{sub 1.6}O{sub 4}, lead to an intercalation of palmitic acid with a layer expansion. Display Omitted - Highlights: • K{sub 0.8}Zn{sub 0.4}Ti{sub 1.6}O{sub 4} intercalates palmitic acid, forming the occluded potassium salt. • The interlayer expansion is evidenced by PXRD patterns and TEM image. • Two types of basic sites are deduced from ultrafast {sup 1}H MAS NMR. • Lepidocrocite titanate catalyses ketonization of palmitic acid to palmitone and corresponding cracked products.

• OSTI ID: 22584117
• Journal Information: Journal of Solid State Chemistry, Vol. 238; Other Information: Copyright (c) 2016 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ADSORPTION
CARBON DIOXIDE
CATALYSTS
CLATHRATES
DESORPTION
ELECTRONS
FOURIER TRANSFORMATION
HEXADECANOIC ACID
HYDROXIDES
INFRARED SPECTRA
KETONES
LAYERS
LIQUIDS
NUCLEAR MAGNETIC RESONANCE
POTASSIUM
POWDERS
SURFACES
TITANATES
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION