Having markedly shorter diffusion path lengths for molecules than conventional zeolites, hierarchical zeolites have advantages in catalysis and gas separations, but that has not been the case in the literature especially for the latter applications. Herein we present simple, scalable synthesis of hierarchical NaX zeolites with exceptionally high crystallinity and show the merits of the material in CO2 separation. The precursor solutions are often called geopolymer resin which is prepared with inexpensive precursor such as NaOH, sodium silicate and metakaolin and an ambient curing of the inorganic resin usually results in a dense dried gel consisting of amorphous 3D network structure of corner-sharing AlO4/SiO4 tetrahedra. By employing vegetable oil to control the alkalinity during the crystal formation/growth, we demonstrate that hierarchical NaX zeolites with a high crystallinity (&gt;95% based on micropore properties) can be produced in a high yield (&gt;0.5 kg/L). The mesopores in the materials exhibit a broad pore distribution with average mesopore widths (4V/A) of about 10 nm, mesopore volumes up to 0.2 cm3/g and external surface areas up to ~120 m/g. Unlike previous reports with nanosized zeolites, the newly synthesized hierarchical zeolites show improved gas diffusion, high CO2-over-N2 and CO2-over-CH4 selectivities (&gt;300% enhancement in comparison to conventional 13X) and negligible regeneration loss. Together with the advantage of the newly developed scalable sustainable synthetic method, the exceptional CO2 sorption properties of the materials present a viable industrial potential of the materials in reduction of the greenhouse gas emission.

New scalable synthetic route for high-crystallinity hierarchical zeolite X as superb sorbent in CO2 separation

254th National Meeting (2017)

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