Synthesis of monodisperse zeolite A/chitosan hybrid microspheres and binderless zeolite A microspheres

Zeolite A/chitosan hybrid microspheres with uniform particle size of ∼700 μm and high crushing strength were prepared by bioorganic molecule-assisted impregnation-gelation-hydrothermal synthesis of silica/chitosan hybrid microspheres in a sodium aluminate alkaline solution. Binderless zeolite A microspheres with similar particle size and medium crashing strength were subsequently obtained after calcination of the zeolite A/chitosan hybrid microspheres. The silica/chitosan hybrid microspheres were prepared by solidification of chitosan microdroplets, which were formed in a microfluidic device from a silica sol-chitosan aqueous solution, in the sodium aluminate alkaline solution. X-ray diffraction, FT-IR, scanning and transmission electron microscopy, thermogravimetric analysis, and adsorption were applied to examine the obtained products. The zeolite A/chitosan hybrid microspheres are composed of zeolite A crystals with particle sizes of 200-400 nm and chitosan, with zeolite A crystals covered with and linked by chitosan. Removal of chitosan in the zeolite A/chitosan hybrid microspheres by calcination has no influence on the structure of the microspheres. Furthermore, the resulting binderless zeolite A microspheres exhibit a high surface area of 30 m ² g ^-1, high static water adsorption amount of 290 mg g ^-1, and quite different adsorption capacities for CH ₄ from H ₂, with a high ideal separation factor for CH ₄/H ₂ of 12. The crushing strength of binderless zeolite A microspheres can be greatly enhanced after a secondary growth. In addition, the formation process of the microspheres was analyzed.