Hydroisomerization of n-Hexane Using Unloaded and Low-Platinum-Loaded H-ZSM-5 and H-MOR Catalysts

Abstract

The applicability for investing and comparing two zeolites (H-ZSM-5 and H-MOR) as supports for low-platinum (less expensive) catalysts used principally for hydroisomerization of n-paraffins in light petroleum naphtha is investigated using n-hexane as a model n-paraffin feed at temperatures of 250°C–500°C in a flow-type reactor with a hydrogen flow of 20 cm3 min−1 at atmospheric pressure. H-ZSM-5 zeolite acquires higher density of strong acid sites, which are still somewhat weaker than the respective sites in H-MOR. These milder sites in H-ZSM-5 zeolite enhanced hydroisomerization and dehydrocyclization but suppressed hydrocracking after incorporating 0.15% Pt. Hydrochlorination (HCl) and hydrofluorination (HF) of 0.15% Pt/H-ZSM-5 were carried out to modify its acidity and Pt dispersion with the goal of maximizing n-hexane hydroisomerization. The HCl treatment seems to have significantly approached the requirement for optimum catalytic bifunctionality, whereas HF treatment appears mostly deteriorative.