ENSEMBLE SIZE-REDUCTION BY RHENIUM SULFUR AS A METHOD TO LOWER THE RATE OF DEACTIVATION OF HYDROCARBON REACTIONS OVER PT CATALYSTS

The reactions of cyclohexane (6.7 kPa) and n-hexane (13.3 kPa) in H-2 (450 kPa) were studied on platinum-rhenium model catalysts in the range 570-740 K. The catalysts were prepared by depositing rhenium on a platinum foil or platinum on a rhenium foil. The catalyst total area was 0.5-1.0 cm2. The surfaces were pre-sulfided before reaction and thiophene added to the feed to maintain the surface sulfided under reaction conditions. Sulfur binds with rhenium forming a catalytically inactive rhenium-sulfur compound. As the concentration of rhenium-sulfur on the surface is increased and the platinum ensembles become smaller, only dehydrogenation-hydrogenation activity is observed. However, the catalyst becomes more resistant to deactivation.