Mechanisms of metal active site diffusion and function in 3D cavity-structured ZSM-5 evolution (solid → yolk-shell → hollow) during coal-derived oil conversion to light aromatics

In the structural evolution of 3D cavity ZSM-5 zeolites (Solid → Yolk-Shell → Hollow), diffusion properties show marked variations, with yolk-shell and hollow configurations offering distinct advantages. Strategic control of metal active sites proves crucial for optimizing evolution pathways and addressing conventional catalysts’ diffusion limitations and low activity. This research comprehensively evaluates Co/Ni-modified yolk-shell ZSM-5 catalysts through experiments, molecular simulations, and DFT calculations. Experimental results reveal the hydrothermally modified HZ5-Co catalyst achieved 387.91 mg·g⁻¹ BTX (benzene, toluene, xylene) yield, substantially outperforming the unmodified sample (236.83 mg·g⁻¹). Hydrothermal treatment induces recrystallization forming hollow structures that enhance pore characteristics and metal distribution. Molecular simulations demonstrate hollow structures’ superior adsorption/diffusion capabilities: 16.4 % higher 4,6-dimethylnonane adsorption (5.88 vs. 5.05 mg · g⁻¹ in solids) and 4.6-fold greater benzene diffusion coefficient (9.28 × 10⁻²⁰ vs. 2.01 × 10⁻²⁰ m²/s in solids), with yolk-shell structures showing intermediate values. DFT analysis indicates Co modification enhances electronic transfer, stabilizes active sites, and optimizes reactant pathways, improving aromatic selectivity. This work clarifies the synergy between pore engineering, metal modification, and diffusion optimization, offering design principles for efficient catalytic conversion of complex macromolecules to BTX aromatics.