n-Hexane Isomerization in the Presence of Nanodispersed Catalysts Supported on Acid-Activated Montmorillonite in the Sodium Form

Abstract

Catalysts based on a palladium sol supported on acid-activated montmorillonite in the Na form (Pd-sol/NaHMM) have been tested in the n-hexane isomerization reaction. An increase in the Pd content from 0.1 to 0.35% leads to an increase in the catalyst activity. The C₆₊ isomer selectivity remains stable and fairly high: it is 94.6–98.0% in the presence of the catalysts with a Pd content of 0.1 or 0.35%, respectively. The maximum conversion of n-hexane over the 0.35%Pd catalyst is 52.6% at a temperature of 400°C; the addition of mordenite leads to a slight decrease in conversion to 50.9%. The maximum conversion at 400°C in the presence of the 0.1%Pd catalyst and the mordenite-modified catalyst is 45.0 and 50.4%, respectively. The maximum yield of isomeric hexanes over the zeolite-free 0.35%Pd and 0.1%Pd catalysts is 44.9 and 39.3%, respectively. In the presence of the mordenite-containing 0.35%Pd/NaHMM+HM catalyst and the low-percentage 0.1%Pd/NaHMM+HM catalyst, the C₆ isomer yield is 44.3 and 43.0%, respectively. The amount of hydrocracking products does not exceed 0.7%. The particle size of the Pd sols is 3.5–5 nm, as determined on a JEM 2100 high-resolution transmission electron microscope. The elemental composition of the Pd-sol/NaHMM catalysts containing different amounts of palladium and the catalysts modified with mordenite has been determined by energy dispersive X-ray fluorescence spectroscopy.