Selective aromatization of polyolefins by temporal decoupling from cracking

Cracking of polyolefins is a prerequisite for their selective conversion over microporous zeolites to value-added small molecules such as monocyclic aromatics. However, cracking and aromatization often proceed concurrently, creating an intrinsic accessibility-selectivity conflict that limits aromatic yield and productivity. This paper describes a strategy that temporally decouples polyolefin cracking from selective aromatization in one-pot with tandem catalysts. This strategy delivers an aromatic yield of ca. 60.3 wt% within 0.5 h at 380 °C from postconsumer polyolefins over 40 consecutive cycles, corresponding to an aromatic space-time yield of 11 g gcat−1 h−1, more than twofold higher than reported values of ≤ 5 g gcat−1 h−1. Kinetic and mechanistic studies reveal that self-pillared pentasil zeolite rapidly and processively cracks polyolefins to small olefinic intermediates below 320 °C, enabling temporal decoupling of low-temperature cracking from higher-temperature aromatization through distinct dominant kinetic windows. Process modeling further suggests favorable economic potential and life-cycle greenhouse-gas emissions 26% lower than fossil-based aromatics production and 66% lower than incineration. This work establishes temporal decoupling as a reaction-engineering strategy for reconciling polymer accessibility with micropore-controlled selectivity in plastic upcycling. Turning plastic waste into useful chemicals is limited because breaking polymer chains and controlling products need conflicting conditions. This study separates these steps in time, enabling fast, durable aromatic production with lower emissions.