Reprint of: Oxidative dehydrogenation of cyclohexane and cyclohexene over supported gold, -palladium catalysts

摘要

Supported gold, palladium and gold-palladium catalysts have been used to oxidatively dehydro-genate cyclohexane and cyclohexenes to their aromatic counterpart. The supported metal nanoparticles decreased the activation temperature of the dehydrogenation reaction. We found that the order of reactivity was Pd ≥ Au-Pd > Au supported on TiO2. Attempts were made to lower the reaction temperature whilst retaining high selectivity. The space-time yield of benzene from cyclohexane at 473 K was determined to be 53.7 mol/kg_(cat)/h rising to 87.3 mol/kg_(cat)/h at 673 K for the Pd catalyst. Increasing the temperature in this case improved conversion at a detriment to the benzene selectivity. Oxidative dehydrogenation of cyclohexene over AuPd/TiO2 or Pd/TiO2 catalysts was found to be very effective (conversion >99% at 423 K). These results indicate that the first step in the reaction sequence of cyclohexane to cyclohexene is the slowest step. These initial results suggest that in a fixed-bed reactor the oxidative dehydrogenation in the presence of oxygen, palladium and gold-palladium catalysts are readily able to surpass current literature examples and with further modification should yield even higher performance.