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 copre cipitation at pH 10. The hydroxide and the mixed oxides resulting from its thermal decomposition at 523, 823 and 1073 K were characterized b y X-ray diffraction, diffuse reflectance infrared spectroscopy, high-r esolution solid-state nuclear magnetic resonance (MAS NMR), and thermo gravimetric analysis. The surface properties of the solid (specific su rface) 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 mo nitored by using H-1 and Ga-71 MAS NMR; H-1 MAS NMR spectra revealed t he loss of interlayer OH groups supporting the brucite-like structure on calcination at 823 K. (C) 1997 Academic Press.