Selective catalytic low pressure hydrogenation of acetophenone on Pd/ZnO/ZnAl2O4

A PdZn alloy-based catalyst was prepared by impregnation with a Pd salt of the oxides obtained by the thermal decomposition of a Zn-Al hydrotalcite. Two samples were obtained by carrying out the reduction at 373 and 673 K, that were characterized by chemical analysis, powder XRD and TEM. The catalytic activity was tested in the low pressure hydrogenation of acetophenone. The results were compared with those obtained using a conventional palladium catalyst

Photoexcited triplets of dyes in zeolitic nanostructured channels. A Time Resolved EPR study

Two dyes (4-nitrostilbene, NST and 4-N,N-dimethylamino-40-nitrostilbene, DANS) included in zeolites with nanometric channels and different Si : Al ratios have been photoexcited and their triplet state studied by time resolved EPR (TR-EPR). This is the first time that a TR-EPR spectrum of photoexcited triplet states of dyes in zeolites has been observed. The zeolites used were ZSM-5 and mordenite, with either protons or lithium as charge compensating ions, and the aluminium-free porosil. The ZFS parameters and the polarized spin populations have been obtained, and compared with those obtained in glassy solutions and in the organic nanostructured matrix perhydrotriphenylene (PHTP). For 3DANS in neutral solvents and in PHTP the dimethylamino group is p conjugated, whereas only its acid form is detected in all the zeolites. In the latter the spectra of the radical cations formed by spontaneous oxidation have also been observed both by cw-EPR and TR-EPR, the last spectra being spin polarized in emission. The mobility of the triplets is discussed, taking into account the spin polarization of the radical cations indicating a strong radical–triplet interaction