CHEMISORPTION OF HYDROGEN AND OXYGEN ON GAMMA-ALUMINA-SUPPORTED RHENIUM .2. CHEMISORPTION OF OXYGEN AND HYDROGEN OXYGEN TITRATION

The chemisorption of oxygen and hydrogen-oxygen titration on γ-alumina-supported rhenium (10.4 wt.% and 1.04 wt.%) have been investigated gravimetrically using a Cahn RG (HV) electrobalance with respect to time (within 300 h), pressure (50-150 Torr or 50-250 Torr, 1 Torr = 133.3 N m-2) and temperature (20-400°C or 20-550°C). The chemisorption of oxygen was found to be slow and occurred on the surface, as well as in the volume of the rhenium. The reaction of hydrogen with surface oxygen or volume oxygen is slow or very slow and occurs only at properly enhanced temperatures. The catalyst of lower rhenium content is more resistant to oxidation and to reduction by hydrogen, indicating a strong metal-support interaction. Because of the low rate and the volume processes, chemisorption of oxygen and hydrogen-oxygen titration are considered unsuitable methods for estimating the surface area and dispersion of rhenium in the applied temperature ranges. © 1990.