سال انتشار: ۱۳۸۷

محل انتشار: دومین کنگره بین المللی علوم و فناوری نانو

تعداد صفحات: ۲

نویسنده(ها):

S Manafi – Materials Engineering Department, Islamic Azad University, Shahrood Branch, Shahrood, Iran
S Joughehdoust –

چکیده:

Zeolites or crystalline aluminosilicates are largely used in separation and refinery industries as catalysts, adsorbents and ion exchangers because of their meso and microporous structures [1]. Conventionally manufactured zeolites, for instance NaA type may contain nano-sized crystals. These are typically lumped together in agglomerates or even intergrowths which resist to a complete breakdown to single crystals. First time, Schoeman and coworkers, prepared zeolites consisting of single crystals with diameters around 100 nm or less. These syntheses produce colloidal sols of zeolites in uniform crystals sizes and have been developed for the preparation of zeolite films and membranes. Reding et al. have been shown that it is possible to control the agglomeration and peptisation of such colloidal zeolites in aqueous media [2]. This is a prerequisite for their efficient solid–liquid separation, and for the manufacturing of catalysts containing small zeolite crystals.The hydrothermal technique usually gives zeolite powders with a high degree of crystallinity. However, the obtained powders are usual in agglomeration and the size distribution is usual in the wide range. However, sometimes it is detected that the creation of a zeolite phase may be preceded with another phase throughout the path of zeolite crystallization. So, this event could be contemplated to be a second synthesis approach for the hydrothermal conversion of one zeolite into another, i.e., zeolite–zeolite transformation. In addition, it is an important route to achieve a novel zeolite which cannot be crystallized by a conventional procedure. Nevertheless, there are just a few researches concerning this method, in which a specific zeolite is utilized as a crystalline aluminosilicate origin rather than amorphous aluminosilicate gels