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.
ABSTRACT
La1-xSrxAlO3-δ (x = 0, 0.1, 0.15) fine particles were prepared by the Pechini process using citric acid and ethylene glycol at low temperature 900 °C. The powders were studied by several physical characterization techniques. The FTIR spectrum of the resin treated at 200 °C revealed the formation of a metalorganic complex and a polymerized form of ethylene glycol. XRD spectra of the samples, calcined at 900 °C, illustrated a single phase LaAlO3. However, La0.9Sr0.1AlO3-δ and La0.85Sr0.15AlO3-δ powders mainly consist of a deficient hexagonal perovskite phase with a small amount of a second phase (LaSrAl3O7). Ionic conductivities of these materials were studied by impedance spectroscopy in the range of 100-700 °C in air.
