The distinct roles of cellulose nanocrystals and seeds in tailoring the properties and catalytic performance of ZSM-5 zeolites

Hierarchical ZSM-5 zeolites address diffusion limitations in microporous frameworks but require sustainable templating. This study elucidates the distinct roles of cellulose nanocrystals (CNCs) and silicalite-1 seeds in tailoring zeolite porosity, acidity, and morphology for catalytic cracking of molecules with different sizes. CNCs act as green mesopore-directing agents, yielding materials with 86% mesoporosity ideal for bulky molecules such as 1,3,5-triisopropylbenzene (TIPB), while seeds promote nanocrystalline frameworks with strong Brønsted acidity and spherical morphology critical for cracking macromolecular plastics like low-density polyethylene (LDPE). Catalytic tests show that catalysts with high CNC content (Only CNC and CNC/Seed (4)) achieve enhanced TIPB cracking efficiency (35% selectivity to benzene, toluene, and xylene, BTX) compared to seed-dominated catalysts (Only Seed and CNC/Seed (2), < 25% BTX). The improved performance arises from either enhanced acid-site accessibility (Only CNC) or optimized acid density (CNC/Seed (4)). Seed-derived catalysts lower the LDPE pyrolysis temperatures by 140 ℃ through nanoscale dispersion. The dual-regulator strategy enables independent control: seeds dominate crystallization, while CNCs enhance mesopores only in seed-free systems. This work provides a blueprint for designing hierarchical zeolites tailored to specific reactant dimensions.