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.