Synthesis and characterization of hydrotalcites by mechanical milling and conventional method

Interest in the use of mixed oxides of Mg and Al has increased notably. These solids are used as catalysts in reactions of basic character and as catalysts supports, due to their structural properties. Mesoporous hydrotalcites, with the formula Mg6Al2(OH)16CO3·4H2O, have been synthesized by two techniques: first, an innovative one, the mechanical milling (MM) and second, the conventional coprecipitation method (CM). The synthesis by CM was prepared from Mg(NO3)2·6H2O and Al(NO3)3·9H2O over a solution of NaOH and Na2CO3, with a Mg/Al molar ratio of 3. The MM technique was employed over the hydrotalcites in an aqueous media previously prepared by CM. In this case, the milling retained the pillared lamellar structure and resulted in the formation of hydrotalcites with refined thickness layers and higher specific areas, compared with those that were prepared by CM. The materials obtained by both methods were calcined at 500 °C and analyzed.