Molybdenum/carbon catalysts for reforming reactions

Abstract

The activities and selectivities of Mo/C and Mo/Al₂O₃ catalysts (prepared by impregnating a coconut charcoal and γ-Al₂O₃, respectively, with ammonium heptamolybdate) have been determined for the reforming of cyclohexane, n-hexane, methylcyclopentane and n-heptane in a microreactor by pulse and flow techniques at 1 atm and 773 K. The Mo/C catalyst was more selective and more stable than the Mo/Al₂O₃ catalyst. The Mo/C catalyst was more active for dehydrogenation and dehydrocylisation whereas Mo/Al₂O₃ was more active for ring expansion, isomerization and cracking. Over Mo/C in the pulse experiments the predominant cracked product was methane. The Mo/C catalyst behaved mainly as a metallic-type catalyst catalysing ring-closure reactions (n-hexane to benzene, n-heptane to toluene) directly and not via a methylcyclopentane intermediate, while the Mo/Al₂O₃ catalyst had both metallic and acidic functions. The molybdenum catalysts are compared with Pt/Al₂O₃ catalysts.