Skeletal Isomerization of n-Butane on Zeolites and Sulfated Zirconium Oxide Promoted by Platinum: Effect of Reaction Pressure

Abstract

The isomerization of n-butane catalyzed by sulfated zirconium oxide and H-form zeolites with the promotion of platinum has been studied by measurements of the conversion and product distribution at temperatures of 240 ∼ 390°C at atmospheric pressure and at 20.4 atm. The skeletal isomerization proceeds mainly via the bimolecular disproportionation mechanism on Pt/H-zeolite at 1 atm and via the monomolecular carbocation mechanism on Pt/SO2−4–ZrO2 at temperatures of ≤ 300°C at both 1 and 20.4 atm. At 20.4 atm pressure, the monomolecular cracking and isomerization of butane can also occur on Pt/H-zeolite. Hydrogen molecules may be dissociated and converted to hydride and proton ions on Pt/SO2−4–ZrO2, promoting the desorption of surface carbenium ions and the cracking of butane molecules, which have been enhanced under high reaction pressures.