Hierarchical Accessibility and Framework‐Al Organization in Ultra‐High‐Silica ZSM‐5 Enable Efficient Cracking of Polyolefin Waste to Light Olefins

ABSTRACT

Selective conversion of waste polyolefins to light olefins offers a promising route for waste‐plastic valorization but is often limited by the trade‐off between cracking activity and secondary reactions over acidic zeolites. Here we report a tetrapropylammonium hydroxide‐directed synthesis strategy assisted by cetyltrimethylammonium bromide (CTAB) and tert‐butanol (TBA) to construct an ultra‐high‐silica hierarchical ZSM‐5 with a highly isolated framework‐Al distribution within a low‐acidity environment. Under hydrogen‐free conditions at 450°C, the optimized catalyst CTAB _2.5 /TBA ₅ ‐ZSM‐5 achieves a gas yield of 95.3 wt%, a C _2– C ₄ olefin selectivity of 88.2% in the gas phase, and a light‐olefin yield of 84.0 wt%, while maintaining a light‐olefin yield of ∼77 wt% over 20 consecutive cycles without regeneration. The catalyst also maintains high gas yields and light‐olefin selectivity across representative post‐consumer polyolefin feedstocks. Structural and catalytic analyses show that the superior performance stems from enhanced mass transport through the hierarchical pore network coupled with a highly isolated, channel‐preferential framework‐Al distribution, thereby suppressing deep secondary conversion. The concerted control of hierarchical accessibility and framework‐Al distribution in low‐acidity zeolites offers a useful framework for designing efficient polyolefin‐cracking catalysts.