Synthesis and Post-synthesis Modification of Zeolite Y for Improved Methanol Adsorption and Coke Formation Resistance

Zeolite Faujasite Y was synthesized, ion-exchanged with NH₄⁺, and calcined to provide the protonated H-Y form. Subsequent post-synthesis alterations included dealumination with oxalic acid for varied durations (1 and 2 h), resulting in samples labeled as H-Y/1h and H-Y/2h. Characterization techniques demonstrated the persistence of the zeolite Y structure despite minor crystallinity loss, particularly in H-Y/2h. Textural improvements were seen following protonation and dealumination. NH₃-TPD analysis revealed that acid treatment resulted in considerable aluminum removal from the zeolite structure, increasing the concentration of strong acid sites in the treated samples. Methanol adsorption kinetics at 25 °C exhibited pseudo-second-order behavior due to its small kinetic diameter and low polarity, which facilitated diffusivity in micro- and hierarchical pores. At 35 °C, Na-Y, H-Y, and H-Y/1h samples exhibited second-order kinetics, indicating favorable methanol adsorption dynamics within zeolite pores. DTG study of methanol adsorption showed that hierarchical porosity creation efficiently suppressed coke formation, hence conserving catalytic activity, as seen in H-Y/2h at high temperatures. These findings highlight the crucial significance of post-synthesis treatments in increasing methanol adsorption and imparting coke resistance to zeolite-Y catalysts.