The impact of the “memory effect” on the catalytic activity of Mg/Al; Mg,Zn/Al; Mg/Al,Ga hydrotalcite-like compounds used as catalysts for cycloxene epoxidation

• Published in: Applied catalysis. A, General Vol. 341; no. 1; pp. 50 - 57
• Main Authors: Angelescu, E., Pavel, O.D., Bîrjega, R., Florea, M., Zăvoianu, R.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.06.2008; Elsevier
• Subjects: Catalysis; Chemistry; Epoxidation of cyclohexene; Exact sciences and technology; General and physical chemistry; Hydrotalcites and mixed oxides catalysts; Memory effect; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Hydrotalcites and mixed oxides catalysts; Memory effect; Epoxidation of cyclohexene; Mixed catalyst; Heterogeneous catalysis; Hydrotalcite; Catalytic reaction; Epoxidation; Oxides; Ethylenic compound
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2007.12.022

Zn and Ga containing hydrotalcites present higher activity than the MgAl hydrotalcite for the oxidation of cyclohexene to cyclohexene oxide in the initial stages of the process. This effect is more pronounced for the activity of the derived mixed oxides. The reconstructed hydrotalcite structures obtained by rehydration have higher activity than the as-synthesized HT. ▪ The epoxidation of cyclohexene by hydrogene peroxide and benzonitrile, in methanol as solvent on solid base catalysts, hydrotalcites (HT) and corresponding mixed oxides (C-HT) was investigated. The employed catalysts were as-synthesized Mg/Al; Mg,Zn/Al; Mg/Ga,Al hydrotalcites, their derived mixed oxides and the corresponding reconstructed hydrotalcite forms (R-HT) obtained via the “memory effect” upon a rehydration treatment of C-HT. The catalysts were characterized by XRD, CO 2-TPD and N 2 adsorption–desorption measurements. The reconstructed HT samples exhibit higher activity in comparison to the as-synthesized carbonated HT samples. A tentative correlation of the catalytic properties with the base strength of the active sites, the structural and textural characteristics of the catalysts, has been explored.