Development of novel preparation method for monolithic and fibrous zeolites by unidirectional freezing of gels

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Silica-alumina hydrogels were synthesized by a sol-gel method as zeolite precursors, and monolithic or fibrous zeolites were prepared by unidirectional freezing of the hydrogels, drying, and steam-assisted crystallization (SAC) using structure-directing agent (SAD). Zeolites prepared in the present work showed excellent properties, which satisfied an objective of development, and their degree of crystallinity and crystal size could be controlled by changing the SDA concentration, SAC temperature, and SAC time. The influence of Si/Al ratio on the hydrophilic property of zeolite was also examined. It was found that the hydrophilic or hydrophobic property could be controlled by choosing the Si/Al ratio. In addition, a controlling method of morphology of zeolite was proposed by using experiments and heat transfer simulation of unidirectional freezing.