Improvement of the catalytic activity of an algerian clay by acid treatment under solvent and solvent-free conditions for 3,4-dihydropyrimidin-2(1h)-one synthesis

Official URL: https://dx.doi.org/10.17159/0379-4350/2023/v77a23

This work aims to study the effects of acid treatment on the structural and catalytic properties of Algerian montmorillonite. Acid activation of montmorillonite is carried out by sulfuric acid (H2SO4) at different concentrations under controlled conditions. The structural changes of the montmorillonite are investigated by XRD, FTIR, XRF, and BET techniques. The results of the proposed study indicated that acid activation causes significant changes in the structure of the samples. This leads to an increase in specific surface area and pore volume. The FTIR spectrum of adsorption of pyridine on montmorillonite showed an increase of the acidic sites depending on the concentration of the treatment solution. The activated montmorillonite is then used as a heterogeneous acid catalyst for the synthesis of dihydropyrimidinone molecule (DHPM) by Biginelli reaction using different solvents, and under solvent-free conditions. It was found that the reaction under solvent-free conditions simplifies the preparation process and gives excellent yields (92%, 8 h), in addition, it is an environmentally friendly process and deals with green chemistry. In this work, the importance of the order of introduction of the reagents is proven, thus allowing us to propose a reaction mechanism.