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首页> 外文期刊>The journal of physical chemistry, C. Nanomaterials and interfaces >Preparation and Characterization of Sol-Gel MgAl Hydrotalcites with Nanocapsular Morphology
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Preparation and Characterization of Sol-Gel MgAl Hydrotalcites with Nanocapsular Morphology

机译：纳米囊形态的溶胶凝胶MgAl水滑石的制备与表征

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摘要

A series of MgAl hydrotalcites (HTs) were synthesized by a sol-gel procedure with ethanol, 2-propanol, and 1-butanol as solvents. Particular attention was paid to controlling hydrolysis reactions by means of using a substoichiometric H2O/Al molar ratio equal to 1. The sol-gel HTs were characterized by means of thermogravimetry, mass spectrometry (MS) of the decomposition products, X-ray diffraction, diffuse reflectance infrared spectroscopy (DRIFT), electron microscopy, and N2 adsorption-desorption. Decomposition products of sol-gel HTs were identified by MS and included, among others, CxHy fragments from alkoxy groups, which were partially withdrawn between 250 and 450 C. Alkoxy groups, from the alcohols employed as solvents, are probably intercalated within the HT layers, as indicated by XRD and DRIFT analyses. CxHy groups in these alkoxy groups were detected by DRIFT at ~2945 and ~2831 cm-1 in dried HTs, even after annealing at 500 C. The HTs obtained by the sol-gel procedure described in this work showed nanocapsular morphology. Transmission electron microscopy and Rietveld refinement techniques evidenced the curvature of the HT layers. In comparison with coprecipitated MgAl-CO3 HT particles (>10 m), sol-gel HTs showed very small particle aggregates (ca. 300~350 nm). Calcined HTs presented specific surface area and pore volume values between 254~332 m2/g and 0.81~1.39 cm3/g, respectively, depending on the alcohol used in the sol-gel procedure.
机译：通过溶胶-凝胶法，以乙醇，2-丙醇和1-丁醇为溶剂，合成了一系列的MgAl水滑石（HTs）。特别注意通过使用亚化学计量的H2O / Al摩尔比等于1来控制水解反应。溶胶-凝胶HTs的特征在于热重分析，分解产物的质谱（MS），X射线衍射，漫反射红外光谱（DRIFT），电子显微镜和N2吸附-脱附。通过MS鉴定了溶胶-凝胶HT的分解产物，其中包括烷氧基的CxHy片段，该片段在250至450℃之间被部分抽出。用作溶剂的醇中的烷氧基可能插入了HT层中，如XRD和DRIFT分析所示。即使在500°C退火后，也可以通过DRIFT在干燥的HT中在〜2945和〜2831 cm-1处检测到这些烷氧基中的CxHy基团。通过本文中描述的溶胶-凝胶程序获得的HTs显示出纳米囊的形态。透射电子显微镜和Rietveld精修技术证明了HT层的曲率。与共沉淀的MgAl-CO3 HT颗粒（> 10 m）相比，溶胶-凝胶HTs显示出非常小的颗粒聚集体（约300〜350 nm）。煅烧的HT的比表面积和孔体积值分别在254〜332 m2 / g和0.81〜1.39 cm3 / g之间，具体取决于溶胶-凝胶法中所用的醇。

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