Olefin impurity effect on n-pentane bimolecular isomerization over WOx/ZrO2

Depending on the catalyst used, the reaction conditions and the molecules converted, alkane isomerization proceeds via a monomolecular or a bimolecular mechanism. n-Pentane isomerizes via both mechanisms which makes it an excellent probe molecule. In this study, n-pentane isomerization was investigated using WOx/ZrO2. Propylene and 1-pentene were co-fed separately to study the effect on n-pentane isomerization and it was identified that only 1-pentene increases the isomerization selectivity to isopentane. Our results support the model of a bimolecular mechanism that proceeds via a C10 intermediate on Zr-WOx Brønsted sites.

► Isomerization activity increases when olefins are co-fed with pentane. ► High olefin concentration increases activity but promotes coke formation. ► Propylene traces promote only the formation of isobutane and C4 olefins. ► The induction period is critical for the formation of C5+ species. ► The bimolecular isomerization mechanism over WOx/ZrO2 is the dominant pathway.