Mechanistic studies of lower temperature isomerization of n-heptane over fibrous silica molybdenum catalyst

Platinum (Pt) inclusion on fibrous silica molybdenum (FSMO) and MoO₃/KCC-1 catalysts has been prepared and utilized for the lower temperature (200–350 °C) catalytic isomerization of n-heptane. The impact of Pt inclusion towards the structure, morphology, and acid distribution of catalysts was characterized by XRD, FTIR, N₂-physisorption, Py-IR, and H₂-IR. Compared with MoO₃/KCC-1, FSMO demonstrated superior MoO₃ dispersion and amount of Lewis acid site associated with the in-situ synthesis technique. Although Pt inclusion slightly lessened acid sites due to inevitable partial coverage by the Pt cluster, the considerably higher amount of Lewis acid sites compared to Brønsted and conjugated sufficiently for generating protonic acid sites for enriching the isomerization activity. In contrast to Pt/MoO₃/KCC-1 and undoped catalysts, Pt/FSMO achieved a superior conversion of 70.9% with 63.6% isomer yield at a low temperature of 250 °C. The 28-h stability tests demonstrated that Pt/FSMO recorded stable isomerization activity, with a superior isomer yield (∼48–52%) and inferior cracking yield (<3.0%) than Pt/MoO₃/KCC-1.