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CONTROLLING THE ACTIVITY AND CHEMOSELECTIVITY IN THE CINNAMALDEHYDE HYDROGENATION BY INSERTION OF NONNOBLE METALS IN THE MATRIX OF HYDROALCITE-LIKE MATERIALS
Autori: Adrian Ungureanu, Alexandra Sasu, Alexandru Chirieac, Alina Moscu Corcodel, Brindusa Dragoi, Constantin Rudolf, Emil Dumitriu
Data aparitiei: January/2012
Revista: Environmental Engineering and Management JournalVol. 11Nr. 1
ISSN: 1843 - 3707
Pret: 25.00 RON    
N.A.
The purpose of this study was to prepare new nanocomposite catalysts of Metal/LDHs type by mild reduction of transition metal cations Co2+ and Cu2+ substituted in the matrix of ZnAl-LDH at 150°C and atmospheric pressure, under hydrogen flow. To this end, a series of ZnCuCoAl layered double hydroxides (LDH) precursors were synthesized by co-precipitation method. M2+/M3+ (i.e., Zn2+/Al3+) molar ratios were kept constant while the Cu2+/Co2+ molar ratios were varied in order to investigate their influence on the structural and textural properties of the resulted catalysts. The LDH precursors were systematically characterized by different techniques such as powder XRD, nitrogen physisorption, FT-IR and DR UV-Vis spectroscopy as well as temperature programmed reduction (TPR). The results indicate that all the precursors present well-crystallized layered structures and a high degree of substitution of cobalt and copper cations in the ZnAl matrix. Upon the mild reduction treatment the layered structure of precursors was maintained, whereas a certain part of transition cations was reduced to metallic centers acting as highly dispersed catalytic active sites. The effect of chemical composition of the ZnCuCoAl LDHs on the catalytic properties in the selective hydrogenation of cinnamaldehyde was studied in propylene carbonate at 150°C and atmospheric pressure. It was observed that catalytic activity gradually increases with the Cu content of LDH, whereas the selectivity to unsaturated alcohol does not depend on the chemical composition. However, a substantial increased chemoselectivity to cinnamyl alcohol can be attained by replacing Cu with Ni in ZnCoAl LDH precursors at the expense of decreased activity.


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