Pt-Pd/WO3-ZrO2 catalysts for isomerization-cracking of long paraffins

The objective of this work was to optimize the acid function and metallic function of a Pt-Pd/WO3-ZrO2 catalyst for isomerization-cracking of long paraffins. The calcination temperature and the W content were the preparation variables varied and studied. The catalysts were tested in the reaction of n-decane isomerization-cracking. The focus of the optimization was put on the synthesis of a catalyst with a good isomerizing activity and a minimum activity for the formation of light gases. In this way an isomerizate of high octane number and high liquid yield would be obtained and used for blending into the gasoline pool. The catalysts were further characterized by temperature programmed desorption of probe molecules (TPD).Varying both the W content and the calcination temperature enabled the regulation of the acid function properties. Thus both the activity and selectivity could be fine-tuned. The highest activity was obtained with the samples with a 15% of W and calcined at 700 °C. The samples calcined at 700 °C were also the most stable ones, i.e. the activity of the acid function was less affected by coking. All the prepared catalysts produced a high octane number gain that was between 75 and 95 points and low yields of light gases (<10%). Deactivation by carbonaceous deposits was attributed to coking on Lewis acid sites.

Graphical abstractThe acid and metal function of a Pt-Pd/WO3-ZrO2 catalyst were optimized for the isomerization-cracking of long paraffins, increasing its liquid yield and RON gain. Varying both the W content and the calcination temperature enabled the regulation of the acid function properties. n-Decane was used as a reaction probe. The highest activity and stability were obtained a 15% W catalyst calcined at 700 °C. All catalysts produced a high RON gain that was between 75 and 95 points and low yields of light gases. Coke deactivation was attributed to coke formation on Lewis acid sites. The figure shows correlation between the amount of Lewis acidity and the amount of carbon deposits after the run. Figure optionsDownload full-size imageDownload as PowerPoint slide