Coke deposition on platinum promoted WOx–ZrO2 during n-hexane isomerization Original Research Article

Platinum on tungsten oxide promoted zirconia catalysts were prepared by calcining the zirconium hydroxide impregnated with tungsten species at different temperatures before platinum addition. Both the amount and nature of coke deposited on these catalysts during the n-hexane isomerization were studied. It was found that the amount of coke formed is small (<0.5%) over all samples. A similar type of coke was produced on catalysts calcined above 600°C, its amount showing a relationship with the catalytic activity. The higher the specific rate, the larger the carbon content. A more hydrogenated and aliphatic coke was observed over the catalyst calcined at 500°C, the difference being related to the properties of WOx–ZrO2 calcined at this temperature. The material calcined at 700°C before platinum addition reached the largest catalytic activity and a similar carbon content referred to the surface area than materials calcined at higher temperatures. Coke can be burnt out at 500°C.