Preparation and selective adsorption performance of F-modified ZSM-5 zeolite for m-cresol and p-cresol

M-cresol and p-cresol, typically produced as mixtures in industrial processes, are crucial chemical intermediates. However, their separation is challenging due to their similar structures and properties. ZSM-5 zeolite has shown potential as an adsorbent for separation, while the performance is yet to be improved. In this study, ZSM-5-F(x) was synthesized via hydrothermal method, incorporating F − ions during the synthesis process. The adsorption behaviour of m-cresol and p-cresol on ZSM-5-F(x) was investigated through static experiments, with ZSM-5-F(8) demonstrating the highest selectivity (9.01). Both ZSM-5-F(0) and ZSM-5-F(8) were characterized using XRD, scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) techniques. In addition, the introduction of F − ions increased the material's electronegativity, as demonstrated by the change in zeta potential from 53.22 to −45.93 mV. Single-component adsorption of m-cresol or p-cresol on ZSM-5-F(0) and ZSM-5-F(8) respectively were investigated in detail. The adsorption of m-cresol on ZSM-5-F(8) showed a non-monotonic phenomenon with a significant decrease after 0.06 mol/L. The thermodynamic parameters including Δ G , Δ H , and Δ S were calculated accordingly. All the values |Δ G |, |Δ H |, and |Δ S | of both components on ZSM-5-F(8) were greater than those on ZSM-5-F(0), suggesting that the introduction of F − ions facilitated the adsorption. Competitive adsorption experiments on both ZSM-5-F(0) and ZSM-5-F(8) were conducted at 298.2 K. The results indicated that the selectivity α p/m on ZSM-5-F(8) increased with increasing initial concentration and laid between 13 and 14. After seven consecutive regeneration cycles, the selectivity (α p/m ) only decreased to 13. This study suggests that ZSM-5-F(8) could be a promising adsorbent for m-cresol and p-cresol in industrial applications.