Hydroisomerization of n-Heptane over Pt-Loaded USY Zeolites. Effect of Steaming, Dealumination, and the Resulting Structure on Catalytic Properties

Abstract

The hydroconversion of n-heptane was studied on five USY zeolite samples loaded with 1 wt % Pt. Experiments were performed on a continuous fixed-bed stainless steel reactor at 210-310 ??C and pressures up to 15 bar. Three in-house samples were subjected to steaming treatment, and the remaining were acid-leached from a commercial source. The study aimed to evaluate the effect of acid leaching, and its subsequent extraframework alumina (EFAL) species removal, on the performance of bifunctional USY zeolite catalysts during n-heptane transformation. Results have shown that steamed samples generate more cracked products at higher conversions when compared to acid-leached ones, more than likely due to a high presence of EFAL species. The degree of steaming played a role in decreasing cracking tendency at higher pressures, which is attributed to pore structure change and decreasing acidity. In addition, steaming resulted in a catalyst sample capable of generating isomers with blended research octane numbers close to those achieved with a robust commercial catalyst. However, poisoning experiments have shown that these two catalysts are highly sensitive to sulfur and require sulfur-free feeds in order to demonstrate their full capacities.