Structural Defects and Acidic and Basic Sites in Sol-Gel MgO
Structural Defects and Acidic and Basic Sites in Sol-Gel MgO
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DOI：
10.1021/jp970233l
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发表时间：
1997-09
影响因子：
3.3
通讯作者：
J. A. Wang;O. Novaro;X. Bokhimi;T. López;R. Gómez;J. Navarrete;M. E. Llanos;E. López-Salinas
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文献类型：
--
作者：
J. A. Wang;O. Novaro;X. Bokhimi;T. López;R. Gómez;J. Navarrete;M. E. Llanos;E. López-Salinas
通过 X 射线粉末衍射和晶体结构细化，用溶胶凝胶技术制备的 MgO 具有晶体结构缺陷，这与其酸性和碱性位点相关。当水镁石和 MgO 共存时，通过吸附吡啶和 NH3 测量发现酸性位点，只有在 673 K 退火样品后才出现。通过吸附 CO2 测量，存在两个不同的碱性位点，总浓度约为每克 1021 个位点。这些位点与 MgO 晶体中镁空位的存在相关。当样品退火温度升高时，碱性位点和镁空位浓度均减少。
MgO prepared with the sol−gel technique had crystalline structure defects, obtained from X-ray powder diffraction and crystalline structure refinement, that correlated with its acidic and basic sites. The acidic sites, measured by adsorbing pyridine and NH3, were found when brucite and MgO coexisted, which only occurred after annealing the sample at 673 K. Two different basic sites, measured by adsorbing CO2, were present in a total concentration of about 1021 sites per gram. These sites correlated to the presence of magnesium vacancies in MgO crystal. Both basic site and magnesium vacancy concentrations diminished when the sample annealing temperature was increased.