ON THE DEACTIVATION OF PT/L-ZEOLITE CATALYSTS

Pt/L-zeolite catalysts have a unique activity for n-hexane aromatization to benzene. There have been proposals which attribute this to electronic and to geometric origins of the L-zeolite. Recently, the uniqueness of the L-zeolite support has been understood to derive from the ability to stabilize very small particles in a non-acidic environment and it has been proposed that a further stabilization against deactivation (by geometric constraint of bimolecular coke precursor reactions) is what distinguishes these catalysts relative to SiO2 supported small Pt particles. We have investigated the initial deactivation rate of four Pt/L-zeolite catalysts and a Pt/SiO2 reference during reaction of n-hexane, neopentane and 2-methyl-2-pentene. In all cases, the relative rates of deactivation correlate with the apparent acidity (as determined by competitive benzene/toluene hydrogenation) suggesting that the deactivation stabilization may have an electronic component.