Abstract
In this work, an Algerian montmorillonite (Mt) is exchanged by different cations from the transition metals family, namely: Cu2+, Ni2+, Cr3+, Co2+, Fe2+ and Fe3+, it is used as a heterogeneous catalyst for Biginelli reaction. The exchanged cations are known for their catalytic properties in homogeneous catalysis. The main purpose is to study the effect of the exchanged cations on the yield and the kinetics of the reaction. The characterization of montmorillonite was carried out by XRD, which allows us to follow the evolution of the basal spacing d001 as a function of the exchanged cation and to show that the exchange operation has not altered the montmorillonite structure. The cation exchange capacity (CEC) is determined by the titration of the exchanged cation by atomic absorption. The product of the reaction is characterized by NMR, IR and by the determination of the melting point. In addition, the importance of the introduction order of the reagents into the reaction medium has been demonstrated on the yield and the kinetics. Finally, the obtained results show that the exchanged montmorillonite is competitive with other costly heterogeneous and homogeneous catalysts.
Highlights
IntroductionThe chemical industry and in particular the fields of organic and pharmaceutical chemistry are confronted with certain constraints of environmental interests
The chemical industry and in particular the fields of organic and pharmaceutical chemistry are confronted with certain constraints of environmental interests. This requires the adoption of new procedures which respect the environmental and ecological balance while improving the cost and efficiency of the reactions. In this sought-after environmental framework, heterogeneous catalysis greatly contributes to the development of the chemical industry and offers many advantages compared to homogeneous catalysis, because the solid catalyst is easy to recover from the reaction medium and to regenerate and it can be used in small amounts.[1,2,3]
In this field commonly known as green chemistry, montmorillonite which is a material of natural origin, has gained interest for contact and surface phenomena applications such as adsorption for elimination of pollutants and heterogeneous catalysis; this is justified by its abundance and low cost, its effectiveness in developing important specific surfaces area, the presence of electrical charges on its surface and its cation exchange capacity.[4,5,6,7]
Summary
The chemical industry and in particular the fields of organic and pharmaceutical chemistry are confronted with certain constraints of environmental interests. This requires the adoption of new procedures which respect the environmental and ecological balance while improving the cost and efficiency of the reactions In this sought-after environmental framework, heterogeneous catalysis greatly contributes to the development of the chemical industry and offers many advantages compared to homogeneous catalysis, because the solid catalyst is easy to recover from the reaction medium and to regenerate and it can be used in small amounts.[1,2,3] Scientific research continues to progress in this area and mainly aims to find new solid catalysts that better meet economic and environmental requirements. Each sheet has a negative charge due to the substitution of the central atoms of these layers by atoms of lower charges; the negative charge
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