Synthesis of mesoporous sodalite by mixed quaternary ammonium cation templates for knoevenagel condensation reaction

Abstract

Sodalite (SOD) is a microporous zeolite with pore size about 2.8 Å which limits its role as catalyst for the reaction involving bulky molecules. To overcome this disadvantage, mesotemplate can be added to create mesoporosity in the synthesis of SOD. A series of SOD samples was synthesized using dual templates approach by mixing tetrapropylammonium hydroxide (TPAOH) with different quaternary ammonium cations. The samples were characterized using X-ray Diffraction (XRD), Fourier Transformation Infrared (FTIR) and N2 adsorption analysis. From N2 adsorption analysis, only SOD sample prepared by mixing TPAOH with organosilane (SOD-TO) showed the characteristic of mesoporosity with a narrow pore size distribution peak centered at ca. 66 Å. The basicity properties of all SOD samples were evaluated by Hammett indicators test and back titration method. While, the basicity property of SOD-TO was compared with the microporous SOD (Na-SOD) using TPD-CO2 analysis. All SOD samples were tested in the Knoevenagel condensation reaction of benzaldehyde and diethyl malonate, giving diethyl-2-benzylidenemalonate as the main product. The results showed that SOD-TO catalyst which possessing the highest amount of basicity and the highest surface area with mesoporosity character gave the highest percentages of conversion and yield of Knoevenagel reaction.