Synthesis and characterization of a novel single-crystalline core–shell zeolite A

Abstract

A novel core–shell LTA zeolite (CSLTA) with uniform mesoporous core and compact microporous shell was hydrothermally synthesized with ultrasonic processing employing a bridged polysilsesquioxane monomer (BPM) as mesoporogen. The morphology of as-prepared CSLTA particles transformed from cubic to circular structure upon introduction of BPM to the synthesis mixture. The XRD patterns confirmed the synthesized CSLTA samples of well LTA-type crystal phase and TEM micrographs clearly showed the novel core–shell structure. The obvious difference of external surface area in nitrogen isotherms between Na+- and Ca2+-CSLTA samples further demonstrated that abundant mesopores were encapsulated within the particles. BET data indicated that the as-prepared CSLTA zeolite samples had large total BET surface area and external surface area. DFT pore size distribution illustrated that the mesopores formed in core mainly centered at around 2–8nm. The exchange rate of Na+ by Mg2+ showed that CSLTA samples had faster initial exchange rate and more efficient Mg2+ removal ability than conventional LTA zeolite.