Improving mechanical stability of ZSM-5 zeolite by defect-healing treatment

Aluminosilicate zeolites are a group of microporous materials widely used in numerous technical applications as catalysts, adsorbents and ion exchangers. Zeolites are subjected to mechanical stress throughout their lifecycle, resulting in the loss of their crystallinity and micropore volume. Therefore, developing zeolites with excellent mechanical properties is important. Recently, our group has reported a liquid-mediated, defect-healing treatment to eliminate the silanol defects in aluminosilicate zeolites with high Si/Al ratios, resulting in imparting extreme chemical stability against water vapor, one of the major chemical damages to destroy zeolite structures. Herein, we investigate an influence of a liquid-mediated, defect-healing treatment on the intrinsic mechanical features of zeolites. ZSM-5 is selected as the target zeolite in this study. Silanol defects in the parent ZSM-5 (HSZ-890HOA, Tosoh) are eliminated by a liquid-mediated, defect-healing treatment. The parent and healed zeolites are subjected to planetary ball milling to compare their mechanical stabilities. Planetary ball-milling treatments, such as rotation at 600 rpm, degrade the crystalline structures of both the parent and healed ZSM-5 with an increase in duration. The diffraction peaks corresponding to the MFI-type structure in parent ZSM-5 completely diminish after planetary ball milling for 60 min. Conversely, diffraction peaks in healed ZSM-5 were retained after such operations, confirming that the mechanical stability of zeolites was enhanced by the liquid-mediated, defecthealing treatment.