Effects of Supported Metals on the Rearrangement of Tetrahydrodicyclopentadiene to Adamantane over a Rare-earth-ion-exchanged Y-Zeolite

Abstract

Bifunctional catalysts, metals supported on Y zeolite exchanged by rare-earth ion(RE³⁺), have high catalytic activity for the synthesis of adamantane from tetrahydrodicyclopentadiene (TCD) in the presence of hydrogen and hydrogen chloride. These catalysts were prepared by the impregnation of metal salts with RE-Y zeolite. Their activity was measured by the batch reactor system. The TCD conversion consists of two reactions, the rearrangement of TCD to adamantane and hydrocracking to ring opening products (C₁₀, H₁₈ isomers). No tarry matertials were produced in the TCD conversion over bifunctional catalysts in the presence of hydrogen. The activity of metals supported on RE-Y for hydrocracking of TCD varied in proportion to the %d character of the metals, while for the rearrangement, it was independent of the %d character of the metals (Fig.3). In the case of a binary system of platinum and rhenium, the maximum activity for both reactions was observed at Re/(Re+Pt) =0.25. In the case of a Ni-Pt-Re system, the activity for hydrocracking of TCD decreased with increasing fraction of nickel(Ni/(Ni+Re+Pt)). Furthermore, poisoning by atomic sulfur on a bifunctional catalyst, the activity for the hydrocracking of TCD was depressed. Based on these findings, control of the surface state of platinum (e. g, surface composition)is quite important for increasing the adamantane selectivity.