Engineering synergistic Brønsted–Lewis sites in MFI zeolite via atomic niobium dispersion for selective alkylation to durene

Atomic-Level Nb Engineering: isolated Nb sites with ~4.8 average coordination number. • Tailored Acidic Landscape and Synergistic Catalysis: medium-strength sites and balanced Lewis/Brønsted ratio selectively boosts alkylation over disproportionation, overcoming the activity-selectivity-stability trilemma. • Superior Catalytic Performance: 39.0% conversion , 58.2% durene selectivity, and 704.7 mg·g cat -1 ·h -1 space-time yield, outperforming conventional catalysts. • Structural Robustness and Practicality: excellent regenerability, structural robustness and stable framework-Nb chemical state over six reaction-regeneration cycles. The selective alkylation of 1,2,4-trimethylbenzene (pseudocumene) to durene represents a pivotal route for C 9 aromatic valorization, yet it is constrained by an inherent activity-selectivity-stability trade-off in conventional HZSM-5 catalysts. Herein, we break this limitation by engineering synergistic Brønsted and Lewis acid sites within an MFI zeolite via the atomic dispersion of low-loading niobium (Nb). A one-step hydrothermal method successfully incorporates Nb into the framework, creating isolated Nb sites with an average coordination number of ∼4.8. This unique structure generates medium-strength acidity and a balanced Brønsted-to-Lewis acid ratio, which are crucial for the selective methylation pathway. The optimized catalyst (Nb/Si ≈ 5.67‰) achieves a remarkable 1,2,4-trimethylbenzene conversion of 39.0% with 58.2% durene selectivity (98.0% among tetramethylbenzenes) and a high space-time yield of 704.7 mg·g cat −1 ·h −1 under optimal conditions (390 °C, 0.8 MPa). Comprehensive characterization and stability tests confirm the structural integrity and regenerability of the catalyst. This work demonstrates a rational design strategy for zeolite catalysts through precise heteroatom modulation, offering broad implications for aromatic upgrading and related tandem processes. Download: Download high-res image (131KB) Download: Download full-size image