Preparation and Characterization of Al-Rich Zn-Al Hydrotalcite-Like Compounds

F. Thevenot, R. Szymanski and P. Chaumette
Institut Français du Pétrole, 1 & 4 Avenue de Bois Préau, B.P. 311 92506 Rueil-Malmaison Cedex, France

Abstract: Hydrotalcite-like compounds, described by the formula [Zn1-xAlx(OH)2][(CO3)x/2 · nH2O], were prepared by coprecipitation methods at 80°C and characterized by bulk chemical analysis, X-ray powder diffraction (XRD), nuclear magnetic resonance (NMR), and scanning-transmission electron microscopy (STEM). An x value of 0.33 was previously assumed to be an upper limit, but recently, Al-rich hydrotalcite-like compounds have been prepared with x as large as 0.44 by hydrothermal synthesis. In the Zn-Al system, Al-rich hydrotalcite was synthesized at normal pressure by coprecipitation. Zn-Al hydrotalcite-like compounds were obtained in the range of x = 0.3 to 0.4. An Al-rich hydrotalcite-like compound with x = 0.44 was formed in mixtures containing large amounts of a poorly crystalline Zn-Al phase. A continuous contraction of the hydrotalcite-like structure occurred as x increased, both the a and c lattice parameters decreasing for x values as large as 0.44. This study illustrates the advantages of using quantitative analytical electron microscopy with high spatial resolution to complement conventional (and bulk) characterization techniques for correlating structural and compositional characteristics of finely divided materials.

Key Words: Hydrotalcite • Nuclear magnetic resonance • Scanning-transmission electron microscopy • Synthesis • X-ray powder diffraction • Zinc

Clays and Clay Minerals; October 1989 v. 37; no. 5; p. 396-402; DOI: 10.1346/CCMN.1989.0370502
© 1989, The Clay Minerals Society
Clay Minerals Society (www.clays.org)