Synthèse et caractérisation d'hydrotalcites Mg-Al. Application à l'éldolisation de l'acétone

Hydrotalcites were prepared with various Mg/Al ratios. The influence of pH and alkaline solution of the precipitation were examined. The compounds are well cristallized when the precipitation is done with NaOH + Na2CO3 alkaline solutions at pH near 10. These samples contain Cl- and (CO3)2- compensating anions in the interlayer space. In all cases well defined hydrotalcites phases are obtained. By exchange reactions of the synthetized samples with Na2CO3 the Cl- anions are totally removed. The production of diacetone alcohol by aldol condensation of acetone is an important industrial reaction using soda or potash as catalysts. The substitution of liquid base catalysts by solid catalysts is desirable to preserve environment. In this goal the basicity of Mg-Al hydrotalcites have been tested in the condensation reaction of acetone. It is also evidenced that for the activation temperature higher 400 °C the catalytic activity of these materials increases with the content of (CO3)2- and the Mg/Al ratio