Synthesis, characterization, and H-1 and Ca-71 MAS NMR spectroscopy of a novel Mg/Ga double layered hydroxide

A new brucite-like layered Mg/Ga double hydroxide (LDH) of composition [Mg0.174Ga0.256(OH)(2)] (CO3)(0.134). mH(2)O was synthesized by coprecipitation at pH 10. The hydroxide and the mixed oxides resulting from its thermal decomposition at 523, 823 and 1073 K were characterized by X-ray diffraction, diffuse reflectance infrared spectroscopy, high-resolution solid-state nuclear magnetic resonance (MAS NMR), and thermogravimetric analysis. The surface properties of the solid (specific surface) and its basicity were also determined. The Mg/Ga LDH was found to be stable up to 523 K and to decompose into a mixture of periclase MgO and amorphous Ga2O3 at 823 K. Its changes with temperature were monitored by using H-1 and Ga-71 MAS NMR; H-1 MAS NMR spectra revealed the loss of interlayer OH groups supporting the brucite-like structure on calcination at 823 K. (C) 1997 Academic Press.