Catalytic Dehydrogenation of Cyclohexene on Silica Overlayer Films

The preparation of nobel-metal catalysts resistant to poisoning is a possibility opened up by the following experiment: On SiO2/Pt/Si layer catalysts (shown schematically below) in the presence of H2, cyclohexene undergoes reaction to give benzene and cyclohexane. The same is true when Pt/Si catalysts are used except that the activity is lower by a factor of 100. SiO2 over-layers of 0 to 30 nm lower the activity exponentially, after which the value remains constant up to 2200 nm. The results indicate that, instead of the transition-metal surface, “active hydrogen” (atomic hydrogen) is the true catalytic species.