Influence of Pt concentration on tungsten oxide-promoted zirconia during n-hexane isomerization Original Research Article

The effect of platinum concentration on tungsten oxide-promoted zirconia over the catalytic activity for n-hexane isomerization was studied. Catalysts were prepared by impregnation of tungsten oxide-promoted zirconia reaching up to 1.50% platinum, followed by calcination at 500°C. The n-hexane reaction was studied at 200°C, 5.9 bar, WHSV 4 and H2: n-hexane (molar) ratio 7. It was found that catalytic activity and stability increase for platinum concentrations above 0.05% because of higher hydrogen availability at the surface, measured as a function of the methylcyclopentane/C6 isomers ratio. Further increments in platinum concentration do not produce important modifications in catalytic activity or hydrogen availability. Mechanical mixtures of Pt/SiO2 and tungsten oxide-promoted zirconia present a lower conversion than platinum over tungsten oxide-promoted zirconia due to the larger distance between the acid and metallic functions.