Abstract
10 % and 30 % wt.CuO/wtsupport CuO/Al2O3, CuO/ZnAl2O4 and CuO/MgAl2O4 were prepared through wet impregnation, starting from commercial supports (Sasol). The catalysts were characterized, before and after catalytic runs, by XRD, IR and UV–vis spectroscopies, SEM and energy dispersive X-ray spectroscopy, surface area and porosity measurements. The fresh CuO-containing powders are converted into supported Cu metal catalysts in an ethanol/nitrogen stream, and act as efficient dehydrogenation catalysts producing acetaldehyde yields in the range 65–90 % at 500−650 K. The best selectivity observed on Cu/ZnAl2O4 is apparently mostly associated to the low activity of the uncovered support surface in the dehydration reactions to diethyl ether and ethylene. These catalysts are progressively deactivated already at 623 K by carbon deposition on copper sites, which leaves almost intact the activity of the uncovered support surface for dehydration reactions. This effect is easily reversed by burning in oxygen at around 650 K. Increasing copper loading only produces some increase in acetaldehyde selectivity. At higher temperature, Cu particle sintering is also observed, but it not necessarily causes evident deactivation.
Published Version
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