Synthesis of New Sn-Incorporated Layered Double Hydroxides and Their Thermal Evolution to Mixed Oxides

Abstract

A new series of Mg II Al III Sn IV hydrotalcite (HT)-like layered double hydroxides (LDHs) with Mg:Al:Sn = 3:1:0 to 3:0:1 were synthesized for the first time by a simple coprecipitation method at room temperature. The physicochemical properties of both as-synthesized and their thermally decomposed products were investigated in detail by various analytical and spectroscopic methods such as powder X-ray diffraction (PXRD), chemical analysis, scanning electron microscopy (SEM), FT-IR spectroscopy, 119 Sn and 27 Al MAS NMR, simultaneous TG/DTA, and N 2 adsorption−desorption experiments. A single phase corresponding to LDH could be obtained in the composition range Mg:Al:Sn = 3:1:0 to 3:0.7:0.3. Above this composition, in addition to LDH, the MgSn(OH) 6 phase also was formed. The 119 Sn NMR showed a broad signal in the range −525 to −660 ppm for Sn atoms existing in a distorted octahedral environment. Thermal calcination of MgAlSn-LDHs at 450 or 700 °C resulted in the formation of MgO-like solid solution, in which both Al 3+ and Sn 4+ were dissolved. The surface area and pore volume had decreased with increasing Sn content for both as-synthesized and calcined samples. Calcination at 1100 °C yielded a mixture of well-crystallized phases corresponding to MgO, MgAl 2 O 4, and Mg 2 SnO 4 “inverse spinel”.