Authors: Hong Khanh Dieu Nguyen Toan Dang Nguyen Dung Ngoc Hoang Duc Sy Dao Thao Tien Nguyen Limphirat Wanwisa Lan Linh Hoang
Publish Date: 2016/12/07
Volume: 34, Issue: 2, Pages: 314-319
Abstract
Hydrotalcitelike compound containing metal cations such as Mg2+ Al3+ and Ni2+ was characterized using Ni Kedge EXAFS and in situ Ni Kedge XANES techniques for clarifying its bonding environment around Ni2+ sites and structure changes during calcination from room temperature to 550 °C respectively At the fixed molar ratio of Mg/Ni/Al of 2/1/1 the results obtained from EXAFS analysis showed a slight blue shift before and after the calcination at 550 °C and a reduction in white line peak the best fits of the two samples revealed tiny change in coordination number about 7 for NiO path but considerable difference for NiMgAl path from about 45 to 95 confirming a modification from brucite like to mixed oxide structure On the other hand bond distances of the NiO and NiMg paths nearly fixed at about 206 Å to 30 Å reflected stability of the cationic bond order on each plane but partial collapse and decomposition of the interlayer formed by water molecules and anion CO 3 2− after the calcination Linear combination fit extracted from the in situ Ni Kedge XANES also confirmed the changes along with the calcination such as slow and fast decreases of brucite fraction at 150 °C and 330 °C respectively in corresponding to the mixed oxide fraction increases The achieved bonding structures were also applied to explain acidbase occurrence of the hydrotalcitelike material especially the acid sites generated by different static charges along with the bonds The explanation was illustrated by NH3TPD method
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