B-Mg co-substituted binder-free ZSM-5 zeolites with recrystallized cheese-like hierarchical porosity for enhanced benzene-methanol alkylation: Synergistic micro-meso-macroporous mass transfer and acid-site engineering

The benzene-methanol alkylation offers a strategic route to valorize methanol surplus and meets the growing demand for high-purity aromatics. For industrially viable shaped catalysts, achieving a balance between sufficient acidity and optimal diffusion capacity remains critical. Traditional shaping methods using binders inadvertently compromise mass transfer efficiency within zeolite crystals while introducing strong acid sites that disrupt the tailored weak-acid properties. To overcome these limitations, we developed a dual-approach strategy employing 1) B-Mg-co- substitution in ZSM-5 frameworks to effectively suppress ethylbenzene generation while enhancing catalytic durability, and 2) recrystallization-driven structural engineering to create binder-free architectures featuring cheese-like macropore. Intelligent gravimetric analysis (IGA) and fluorescence probe diffusion mapping further reveals three-dimensionally interconnected micro-meso-macroporous networks that facilitate enhanced molecular transport for both small and bulky aromatic species. The optimized catalyst demonstrates remarkable stability during extended operation (1008 h) under 460 °C, 0.4 MPa and 2.5 h −1 , achieving 45–50 % benzene conversion (X B ) with toluene selectivity (S T ) ~50 %, C 8 selectivity (S C8 ) ~37 %, C 9+ selectivity (C 9+ ) ~ 14.0 %, and yield of EB in C 8 (Y EBinC8 ) <9 %. This work establishes a morphology-directed synthesis protocol for isomorphously substituted zeolites, offering a scale-up manufacturing route for acid site-engineered catalysts that combine hierarchical porosity with optimized Brønsted-Lewis acid synergy.