Engineering of Zeolite Framework Aluminum Spatial Distribution Boosts Light Olefins Yield in Catalytic Pyrolysis of Fatty Acid

The spatial distribution of framework aluminum (AlF) in ZSM-5 zeolites critically controls catalytic pathways for converting fatty acids to value-added short-chain olefins (C4=-C8=). Here, we synthesize hierarchical-porous BioZ5-PX catalysts using phytic acid (PA)-modified tea seed husk (TSH) biomass templates to strategically position AlF. Interestingly, PA optimization precisely directs aluminum toward channel intersections, enhancing Brønsted acidity and Al-pair proximity. This spatial engineering achieves near-complete deoxygenation (100% conversion) with exceptional 97.4% total olefin selectivity and 92.6% C4=-C8= selectivity, outperforming unmodified analogs by >32%. Mechanistic studies reveal that aluminum enrichment at intersections facilitates a cascade reaction: stearic acid first undergoes decarbonylation to a C17H35OH, followed by dehydration and selective C–C cleavage to C4=-C8= products. Conversely, aluminum confined to straight/sinusoidal channels as isolated sites restricts intermediate diffusion (due to large steric hindrance) and cracking efficiency. This work establishes AlF spatial control as a key design principle for designing high-performance zeolite catalysts for sustainable, high-yield olefin production from biomass.