Cooperative Cracking of 1-Pentene and n-Pentane on ZSM-5: Diene-Mediated Pathway Control to Light Olefins

Coconversion of hydrocarbons offers a sustainable and efficient route to high-value products while lowering the cost and energy demand for pure feedstock preparation. Here, we propose a cocracking process for alkanes and alkenes, and systematically investigate their interactions under mixed feed conditions through experiments and simulations. Introducing 0–40% alkanes into the alkene feed enhances conversion and maintains high selectivity for light olefins while suppressing methane and aromatics. At 20% alkane, the combined selectivity of ethylene and propylene reaches 69.8%, with an ethylene/methane ratio of 11.94. Validation experiments using cocracking of pentadiene and n-pentane with in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) show that dienes improve the product profile of alkane cracking and strengthen n-pentane adsorption on acidic zeolites, which favors alkene formation and suppresses methane and aromatics. Density functional theory (DFT) calculations further support that interactions between pentadiene and n-pentane facilitate a shift in the cracking pathway from a pentacoordinate to a tricoordinate carbocation mechanism, lowering the energy barrier. This work demonstrates a feasible strategy for the production of light olefins via hydrocarbon coconversion and advances mechanistic understanding of alkane–alkene cocracking.