Rh-modified alumina membranes: preparation, characterization and reaction studies

The Rh-modified gamma-Al2O3 membranes were prepared by two ways. The pore s ize distribution demonstrates that, after addition of a small amount of rho dium to the boehmite sol, the structure of gamma-Al2O3 membrane still remai ns intact. The mean pore diameter remained at about 3 nm. Meanwhile, Rh-mod ified gamma-Al2O3 membrane exhibited a much higher separation factor of H-2 /Ar than pure gamma-Al2O3 membrane in the range of 100-350 degrees C. In ad dition, the Rh-modified gamma-Al2O3 membranes were applied to the membrane reactors of ethanol dehydrogenation, and the effects of the temperature and flow rate of sweeping argon on ethanol conversion were investigated. The r esults showed that the ethanol conversion and the selectivity of acetaldehy de in the Rh-Al2O3 membrane reactor were higher than those in Al2O3-Rh memb rane reactor, owing to the former's higher hydrogen permeability and separa tion factor in the range of experimental temperature. The reduction tempera ture and hydrogen adsorption properties of Rh-modified alumina membrane wer e measured by TPR and TPD separately; the morphology and structure of the m embrane were characterized by SEM. TEM and XRD, respectively. (C) 1999 Else vier Science B.V. All rights reserved.