The balance of acid-base property is crucial for the catalytic performance of Side-Chain Alkylation of Toluene with Methanol (SATM). In this work, Na 3 PO 4 modified NaX catalysts with suitable middle base strength and feasible acid-base center distance were prepared by direct solvent-evaporation and exhibited the best styrene selectivity of 45.4 % and the total yield of side chain alkylation products of 71.7 %, respectively at methanol conversion up to 99.9 % in NaX-P (0.075) . Notably, the selectivity exhibits surprising stability in the evaluated 15 days, which might owe to the uniform dispersion of active species and constant acid base property. Combined the comprehensive characterizations of solid-state NMR, FTIR, SEM, and XPS, etc., with Density Functional Theory (DFT) calculation results, it is revealed that O-1264 are affected mostly by loading Na + or both of Na + and PO 4 3- , which exhibits the least adsorption energy and the highest electronic cloud density in the four kinds of oxygen atoms according to the calculated Bader charge. Therefore, the structure S4 (O-1264) was considered to be the most stable and meet the basicity requirements for SATM.
Achieving an optimal acid-base synergy and uniform dispersion of active sites on catalyst surface is essential for high catalytic performance in the side chain alkylation of toluene with methanol (SATM). Herein, we report that ammonium (NH₃) treatment of Cu-modified NaX zeolite catalysts effectively modulates acid-base properties and enhances the dispersion of Cu active sites across the catalyst surface. A series of Cu-modified catalysts were prepared with and without NH₃ treatment and further modified with NaOH to evaluate their synergistic effects. Comprehensive characterization techniques, including Scanning Electron Microscopy (SEM), HAADF-STEM and EDS, Pyridine FTIR, Temperature-Programmed Desorption of NH₃ (TPD-NH₃), X-ray Photoelectron Spectroscopy (XPS O 1 s), and regression analysis, were used to correlate catalyst structure, and acid-base property and nature of acid sites with catalytic performance. Results reveal that NH₃ incorporation into the Cu-modified NaX framework significantly enhances catalytic efficiency by tuning acid-base properties and promoting a homogeneous distribution of Cu active sites. Notably, the 3Cu-4Na-N catalyst achieved a superior yield of ethylbenzene and styrene production, reaching 84.9 %, compared to 64.3 % for the 3Cu-4Na catalyst under identical conditions. Methanol conversion reached 97.7 %, with the catalyst demonstrating robust stability over 168 h of operation. Additionally, 3Cu-4Na-N catalyst exhibited the highest turnover frequency (TOF) reaching 27.3 h -1 , confirming its superior intrinsic activity. This study highlights the critical role of NH₃ in advancing Cu-NaX catalysts for SATM and provides a promising strategy for optimizing catalytic performance through controlled acid-base interactions and active site dispersion.
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