In situ infrared study of n-heptane isomerization over Pt/H-beta zeolites

The isomerization of n-heptane over hydrogenated (H-) and Pt-loaded (Pt/H-) beta zeolites was observed directly by in situ infrared spectroscopy for investigation of the reaction mechanism and coking process. Carbonaceous species produced in the reaction are identified as either highly branched polyolefins (1485 cm−1 band) or coke (1600 cm−1). The former can be readily removed by O2 treatment at moderate temperatures (>573 K), whereas complete removal of the latter requires higher temperatures (>723 K). The formation of coke is successfully inhibited by the presence of H2 in the reaction stream. The hydrogenation and dehydration functionality of Pt particles in this catalyst system has been confirmed through H/D isotope exchange experiments.