Construction of high performance binder-free zeolite monolith

Compared to conventional spheres, strips, and granules, structural adsorbents offer shaping of the adsorbent materials. In this work, we report a straightforward procedure to shape binder-free zeolite monolith (BF-ZM). During the synthesis, hydroxypropyl methylcellulose was applied as a binder, and the zeolite precursor material halloysite nanotubes and Y zeolites were mixed to produce the initial zeolite monolith. The binder was removed by high-temperature calcination to gain preliminary mechanical strength, followed by hydrothermal crystallization to convert the binder into Y zeolites to obtain a 100% pure Y zeolite structure. The as-synthesized BF-ZM exhibits excellent mechanical properties, showing negligible powdering after 1.34 × 10⁵ cycles of accelerated pressurization/depressurization test; in comparison, ordinary packed columns using zeolite beads suffered from 3.51% loss due to powdering. This result indicates that BF-ZM is favorable for filling large pressure swing adsorption columns and can significantly alleviate the issue of adsorbent chalking and slabbing caused by the reciprocal pressure swing of the gas flow. The BF-ZM also achieved a high CO₂ adsorption capacity of 6.4 mmol·g⁻¹ at 1.2 bar and 273 K, superior to commercial Y zeolite pellets. The results of the breakthrough experiments showed a CO₂ adsorption capacity of 4 mmol·g⁻¹ at 333 K and 1.25 bar before the permeation started. The selectivities (CO₂/N₂:15/85) of BF-ZM have been calculated using the IAST method, showing 74 excellent selectivity at 333 K and 1 bar. This study provides a straightforward approach to the design and fabrication of high-strength binder-free adsorbents for large-scale industrial gas separations.