Amine-grafted Na-LTA zeolite precursors as basic catalysts for Knoevenagel condensation

Knoevenagel condensation is a C–C bond formation reaction widely used in fine chemistry, which can be catalyzed by bases, such as Na-zeolites and supported amines. Due to the high size of the molecules that are used, its application is highly influenced by the accessibility of the catalytic sites that promote the reaction. In this context, this work studied the effect of the crystallization time of aluminosilicate precursors of LTA zeolite on the propylamine anchoring capacity. The materials were compared in terms of the amount of grafted propylamine as well as the accessibility of the sites in the Knoevenagel condensation reaction. Functionalized solids prepared with shorter times in hydrothermal synthesis were more active in the reaction due to the greater propylamine anchoring capacity. Also, the amorphous precursors of LTA zeolite were more active, due to their greater accessibility of the catalytic sites before the microporous structure was formed. [Display omitted] •Amorphous precursors of zeolite 4A have greater catalytic activity in Knoevenagel condensation than crystallized zeolite.•Anchoring propylamine on amorphous aluminosilicates improves its catalytic activity in Knoevenagel condensation.•Anchoring capacity is defined by the amount of surface silanols.