Synthesis and characterization of hydrotalcites

Jugraj Jatav, Ramesh Jatav, Sa

Abstract

new synthesis of hydrotalcite like materials having a composition [M+xA13+] (OH)2Ax.mH20, where M 2+ is magnesium, nickel or cobalt and A- is a monocarboxylic anion, is described. The synthesis involves reacting a source of the divalent cation with a monocarboxylic acid in aqueous slurry at 1100C for 24 hours. The reactive source of magnesium is either magnesium oxide or hydroxide and the reactive source for nickel and cobalt are the respective hydroxides. This synthesis method results in the formation of hydrotalcite with a unique sheet-like morphology with the sheets having breadth to thickness ratio in excess of 100, in contrast to the previously known hexagonal hydrotalcites which have a breadth to thickness ratio between 5 and 10. The phrase 'sheet-like' in this work describes the macroscopic morphology of the hydrotalcite crystallites. A key finding was that the presence of monocarboxylic acid was necessary for the formation of sheet morphology. It was also demonstrated that sheet and hexagonal morphologies readily interconvert via a common mixed oxide precursor.