Base-catalyzed condensation of citral and acetone at lowudtemperature using modified hydrotalcite catalysts

摘要

A study on the catalytic properties of properly activated hydrotalcite (HT) with special attention to the nature and amountudof active sites present in this solid base catalyst has been undertaken. Only a small fraction (5%) of the available basic sitesudin the rehydrated calcined HT is active in liquid-phase aldol condensations. These sites exhibit high catalytic activity and areudmost likely localized at the edges of the HT-platelets. Besides a high activity, these modified HTs also show a high selectivity.udNo further condensation products other than diacetone alcohol (DAA) in the acetone self-condensation could be observed.udInitial results with the citralu96acetone condensation show that even at 273 K this reaction is catalyzed by modified HTs withuda conversion of 65% and a selectivity of 90%, when the citral concentration is not too high ( 1 wt.%). At higher citraludconcentrations, no reaction is observed indicating a negative order in citral concentration. © 2000 Elsevier Science B.V. Alludrights reserved.