Partial oxidation of propane to synthesis gas over noble metals-promoted Ni/Mg(Al)O catalysts - High activity of Ru-Ni/Mg(Al)O catalyst

摘要

Effect of the addition of small amount of noble metal, i.e. Ru, Rh, Pd, Ir or Pt, in the Ni/Mg(Al)O catalyst on the catalytic activity for the partial oxidation of propane has been investigated. Mg-2.5(Ni-0.5)-Al hydrotalcite was prepared by co-precipitation and was calcined to form Mg-2.5(Al,Ni-0.5)O periclase. When the powders of the periclase were dipped in an aqueous solution of the nitrate of Ru(111), Rh(111), Pd(II), Ir(Ill) or Pt(II), a reconstitution of the hydrotaclite took place on the surface Of Mg-2.5(Al,Ni-0.5)O particles due to a "memory effect". The calcination followed by the reduction of the dipped samples produced highly dispersed noble metal-Ni supported catalysts. The loading of noble metal gave rise to a decrease in the reduction temperature of Ni2+, to Ni-0 on Mg-2.5(Al,Ni-0.5)O periclase, an increase in the amount of H-2 uptake on the Ni metal and moreover a decrease in the particle size of Ni metal formed on the noble metals-Ni/Mg-2.5(Al)O catalyst. When the noble metals-Ni-0.5/Mg-2.5(Al)O catalysts were tested in the temperature-cycled operation of propane partial oxidation between 400 and 700 degrees C, the deactivation due to both Ni oxidation and coke formation on the catalyst was effectively suppressed by the loading of noble metals. The combination of Ru and Ni-0.5/Mg-2.5(Al)O was the most effective; the high sustainability against both Ni oxidation and coke formation was obtained only with 0.1 wt% of Ru loading. A dipping of 1.0 g of the powders of Ni-0.5/Mg-2.5(Al)O periclase in a 5 ml of Ru(III) nitrate-aqueous solution was enough to reconstitute the hydrotalcite on the surface of the powder particles, leading to the formation of the Ru-Ni bimetal loaded catalyst with the high activity as well as the high sustainability. (c) 2006 Elsevier B.V. All rights reserved.