Effect of Na exchange of a HBEA zeolite on the activity and the selectivity of a bifunctional Pt-HBEA catalyst for n-hexadecane hydroisomerization. Comparison with a Pt-HZSM-22 catalyst

The transformation of n-hexadecane was carried out in a fixed-bed reactor at 220 degrees C under 30 bar total pressure on bifunctional Pt-zeolite catalysts. The Pt-HBEA catalyst was very active but yielded much cracked products due to a rather strong protonic acidity. Pt-Na-HBEA catalysts obtained through partial exchange by sodium ions of the protonic sites of the HBEA zeolite were less active than Pt-HBEA but allowed to decrease significantly cracking. The effect of Na exchange on the activity of the catalysts was quantified using a kinetic model. Pt-HZSM-22 was much less active than Pt-HBEA but more selective for isomerization. However, the selectivity for isomerization of the Pt-Na-HBEA was very similar to that of Pt-HZSM-22 up to a 80% n-hexadecane conversion, while its activity was 2.5 times higher.