The role of metallic modifiers of SBA-15 supports for propyl-amines on activity and selectivity in the Knoevenagel reactions

A series of bifunctional heterogeneous catalysts based on SBA-15 supports modified with Zr, Nb and Mo species functionalized by aminopropyl siliceous species has been used in the Knoevenagel condensation. The results indicated that the acid-base synergetic effects of the centres present on these catalysts seem to have significant effect on the Knoevenagel condensation of benzaldehyde with active methylene compounds. Basic sites and Lewis acid sites play different roles depending on the methylene compound used in the Knoevenagel condensation. Depending on the chemical composition of the catalysts, the reaction can proceed on basic sites exclusively or on the pairs of acidic-basic centres. The nature of metal species strongly influences the activity in the Knoevenagel condensations but does not affect the selectivity. (C) 2015 Elsevier Inc. All rights reserved.