Synthesis of Mg−Al Hydrotalcites with Various Surfactants as Solid Base Catalyst for the Knoevenagel Condensation Reaction.

Mg−Al layer double hydroxide (Mg/Al=3.0), commonly designed as hydrotalcite (HT), has been prepared in the presence of surfactant reagents of various types to control its genesis during co‐precipitation. Among cationic, anionic, noninonic, and amphoteric surfactants, the cationic surfactant of benzyldimethyltetradecylammonium chloride (denoted as HT‐a, here) served a highly‐active Mg−Al HT for the Knoevenagel condensation reaction of furfural and diethyl malonate to diethyl 2‐furfurylidenemalonate, which was selected as a model base‐catalyzed reaction for this study. It was found that crystalline sizes of (003) had a linear relation to the product yield. Based on FE‐SEM observations and N2 adsorption isotherm analysis, aggregation and growth of HT crystals are expected to be prohibited in the presence of benzyldimethyltetradecylammonium chloride, affording the smaller size domains (secondary particles). These results are associated with enhanced reactivity for the base‐catalyzed reaction. [ABSTRACT FROM AUTHOR]