Isomerization of n-heptane over Pt(Pd)/WO3/ZrO2 catalysts

Abstract

The effect of Pt and Pd concentration in WO3/ZrO2 catalysts on their acidic and catalytic properties in isomerization of n-heptane has been studied. It was found that the highest yield of the target products of the reaction – di- and trimethyl substituted (DTMS) high-octane heptane isomers – is reached on the samples with the platinum content of 1.0–1.5 wt.% and is equal to 29.2–29.3 wt.%. When Pd is used as a metallic component, the DTMS yield of ca. 29.1 wt.% is attained at a palladium content of 0.1 wt.%. Pt(Pd)/WO3/ZrO2 catalysts were subjected to thermal treatment in a hydrogen medium and effect of the treatment conditions on isomerization of n-heptane was investigated. The reduction of the catalysts at temperatures above 300°C was shown to reduce tungsten atoms with the formation of Lewis acid sites (LAS), thus promoting the side reactions leading to cracking of heptanes.