Highly selective hydrocracking of polypropylene to gasoline-range fuels over the Pt/MCM-22 catalyst

Abstract

The catalytic conversion of polypropylene (PP) waste into valuable liquid hydrocarbons represents a particularly significant strategy for advancing a circular economy. Unlike polyethylene (PE) upgrading, a fundamental challenge in PP upgrading arises from its methyl-rich structure, which would preferentially undergo direct cleavage toward terminal C–C bonds, thereby promote the formation of undesirable methane (CH₄) as a byproduct. Herein, we, for the first time, showed that the Pt/MCM-22 catalyst exhibits superior performance for the hydrocracking of PP, achieving a 92.3% PP conversion with a 98.9% selectivity for C₄–C₁₀ alkanes while effectively suppressing the formation of CH₄. Notably, the liquid products consisted primarily of iso-alkanes, with a remarkably high selectivity of 82.6% towards isomerized C₅–C₁₀ alkanes, highlighting their suitability as premium high-octane blending components for gasoline. Comprehensive characterizations demonstrated that the high dispersion of Pt nanoparticles, combined with the unique pore structure and abundant Brønsted acid sites of the MCM-22 zeolite, facilitated efficient PP hydrocracking. Reaction monitoring and the H₂/D₂ exchange experiment suggested that the reaction followed the classical bifunctional catalytic mechanism. This work enables the direct upcycling of PP into valuable gasoline-range fuels using a highly selective catalyst.