Preparation and characterization of sol-gel MgAl hydrotalcites with nanocapsular morphology

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sol−gel HTs were identified by MS and included, among others, CxHy fragments from alkoxy groups, which were partially withdrawn between 250 and 450 °C. Alkoxy groups, from the alcohols employed as solvents, are probably intercalated within the HT layers, as indicated by XRD and DRIFT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 s...