Influence of heating on the solid acidity of montmorillonite: A combined study by DRIFT and Hammett indicators
Influence of heating on the solid acidity of montmorillonite: A combined study by DRIFT and Hammett indicators
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加热对蒙脱石固体酸度的影响：DRIFT和Hammett指标的联合研究
DOI：
10.1016/j.clay.2011.03.016
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发表时间：
2011-06-01
影响因子：
5.6
通讯作者：
Zhu, Jianxi
中科院分区：
文献类型：
--
作者：
Liu, Dong;Yuan, Peng;Zhu, Jianxi
采用Hammett指示剂和漫反射傅里叶变换红外光谱相结合的方法测定了蒙脱石及其加热产物的固体酸性。固体酸总量为0.10 mm o l/g蒙脱石，加热后固体酸总量增加。由于蒙脱石的脱水和脱羟基，不饱和Al3+离子的Lewis酸位的数量增加。Bronsted酸中心是由层间极化的水分子、带负电荷的AlO4吸附H3O+离子和不饱和Al3+离子吸附水所致。加热后Bronsted酸量增加，在120℃时达到最大值，这是由于层间水分子的解离增强所致。由于层间水分的逐渐去除，随着加热时间的延长，温度逐渐降低。400℃和600℃焙烧后蒙脱石的层间距较小，影响了固体酸中心的测定。120℃、200℃和600℃加热后出现的高强度酸中心归因于层间极化水和再水化的不饱和Al3+离子。(C)2011爱思唯尔B.V.保留所有权利。
The solid acidity of montmorillonite and its heated products was determined by combining Hammett indicators and diffuse reflectance Fourier transform infrared spectroscopy. The total amount of solid acid sites was 0.10 mmol/g montmorillonite and increased after heating. The amount of Lewis acid sites, unsaturated Al3+ ions, increased due to the dehydration and dehydroxylation of montmorillonite. The Bronsted acid sites resulted from interlayer polarized water molecules, H3O+ ions adsorbed by the negatively charged AlO4, and water adsorbed on the unsaturated Al3+ ions. The Bronsted acid amount increased after heating and the largest value was found at 120 degrees C due to the enhanced dissociation of the interlayer water molecules. It decreased with further heating due to the gradual removal of the interlayer water. The determination of solid acid sites was affected by the small basal spacing of montmorillonite after calcination at 400 and 600 degrees C. High-strength acid sites, appearing after heating at 120, 200 and 600 degrees C were attributed to interlayer polarized water and rehydrated unsaturated Al3+ ions. (C) 2011 Elsevier B.V. All rights reserved.