Influence of the Distance between Brønsted Acid Sites and Mo Sites in Mo/HZSM-5 on the Mechanism of Methane Dehydroaromatization Performance
Methane dehydroaromatization (MDA) offers a carbon-neutral route to benzene, toluene, and xylene (BTX), yet the regulatory mechanisms of Brønsted acid site (BAS) strength and spatial proximity to Mo sites remain unresolved. This study systematically tunes BAS strength via isomorphous substitution (Al, Ga, Fe, B) and Mo-BAS proximity in ZSM-5, integrating catalytic evaluations with density functional theory (DFT). Strongly acidic Al-zeolites achieve the highest methane conversion, while weakly acidic B-substituted systems exhibit optimal mono-/bifunctional synergy, outperforming moderate-acid counterparts. DFT reveals that deprotonation energy (DPE) correlates with acid strength; Al-ZSM-5 (DPE = -5.68 eV) lowers the C–H activation barrier (ΔG = 1.467 eV). Spatial proximity analysis shows that nanoscale Mo-BAS distances, achieved via ball milling, enhance methane conversion by 33% and BTX yield by 31% compared to micrometer-scale mixtures, by accelerating intermediate transport and suppressing coke. These findings establish a multi-scale framework linking acid strength, spatial confinement, and electronic modulation, providing actionable guidelines for designing next-generation MDA catalysts.