Surface and interlayer base-characters in lepidocrocite titanate: The adsorption and intercalation of fatty acid
Surface and interlayer base-characters in lepidocrocite titanate: The adsorption and intercalation of fatty acid
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DOI：
10.1016/j.jssc.2016.03.030
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发表时间：
2016-06-01
影响因子：
3.3
通讯作者：
Sooknoi, Tawan
中科院分区：
文献类型：
--
作者：
Maluangnont, Tosapol;Arsa, Pornanan;Sooknoi, Tawan
虽然具有带正电片层的层状双氢氧化物（LDH）作为基本材料是众所周知的，但具有带负电片层的层状金属氧化物通常不被认可。本文以纤铁矿钛酸盐K0.8Zn0.4Ti1.6O4为例，论证了层状金属氧化物中O2-位的表面和层间基性。 CO2-TPD显示的低碱度（0.04 mmol CO2/g）和低解吸温度（50-300℃）表明外表面的O2-位点呈弱碱性，而层间空间的O2-位点大多难以与CO2接触。然而，液相吸附研究表明，大体积棕榈酸（C-16 酸）的吸收量高达 37%（按质量计）。 PXRD 和 TEM 检测到伴随的层间空间膨胀约 0.1 nm。以与外表面相反的方式，层间 O2- 位点可以使棕榈酸去质子化，形成夹在片材之间的盐（即棕榈酸钾）。根据超快 H-1 MAS NMR 和 FTIR 结果提出了两种类型的碱性位点。纤铁矿钛酸酯中的层间碱性位点导致该材料作为选择性且稳定的二维 (2D) 碱性催化剂的应用，如棕榈酸酮化为棕榈酮（C-31 酮）所证明的那样。还说明了通过改变 Ti-IV 位点的金属（Zn、Mg 和 Li）取代类型来调节催化活性。 (C) 2016 Elsevier Inc. 保留所有权利。
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 O2- sites in layered metal oxides have been demonstrated, taking lepidocrocite titanate K0.8Zn0.4Ti1.6O4 as an example. The low basicity (0.04 mmol CO2/g) and low desorption temperature (50-300 degrees C) shown by CO2- TPD suggests that O2- sites at the external surfaces is weakly basic, while those at the interlayer space are mostly inaccessible to CO2. The liquid-phase adsorption study, however, revealed the uptake as much as 37% by mass of the bulky palmitic acid (C-16 acid). The accompanying expansion of the interlayer space by similar to 0.1 nm was detected by PXRD and TEM. In an opposite manner to the external surfaces, the interlayer O2- 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 H-1 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-31 ketone). Tuning of the catalytic activity by varying the type of metal (Zn, Mg, and Li) substituting at Ti-IV sites was also illustrated. (C) 2016 Elsevier Inc. All rights reserved.