Fabrication of hierarchical zeolite 4A microspheres with improved adsorption capacity to bromofluoropropene and their fire suppression performance

• Hierarchical zeolite 4A microspheres were prepared from Kaolin precursor in a simple ethanol–water mixed solvent.
• The concentration of ethanol in the solvent played a key role for the formation of zeolite 4A microspheres.
• Zeolite 4A microspheres showed higher adsorption capacity to a clean fire suppressant of bromofluoropropene than that of cubic ones.
• The microspheres soaked with bromofluoropropene showed better fire suppression performance than that of the cubic counterparts.

Novel hierarchical zeolite 4A microspheres consisted of interconnected nanoflakes were successfully prepared from Kaolin precursor in a simple ethanol–water mixed solvent system. While in aqueous solution without ethanol, only commonly cubic particles were obtained. It was found that the concentration of ethanol in the solvent was crucial to the production of microspheres. There existed an optimized concentration range of ethanol where microspheres were fabricated with highly yield. Thus-prepared single-phase zeolite 4A microspheres exhibited a large Brunauer–Emmett–Teller (BET) surface area of 666.9 m2/g, pore volume of 0.0147 cm3/g and average pore size of 6.9 nm. The porous spheres exhibited an adsorption capacity of 8.7 wt.% to a clean gas fire suppressant of 2-bromo-3,3,3-trifluoropropene (BTP) at room temperature, much higher than that of conventional cubic zeolite 4A particles (4.2 wt.%). Bench scale fire tests revealed that these zeolite 4A microspheres soaked with BTP exhibited much better performance than that of cubic counterparts in suppressing methane/air coflowing diffusion flames in cup burner, with the fire extinguishing concentration decreased by more than 20% at the comparable powder discharging rate. Such an improvement could be ascribed to the larger surface area and higher adsorption capacity of zeolite 4A microspheres.

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