关键词: 分子筛, 沸石晶体材料, 无有机模板剂, 晶种导向合成

Zeolites with unique physical and chemical properties, such as Beta, ZSM-34 have been extensively studied for a long time as important materials in the chemical industries such as shape selective catalysis, adsorption, ion exchange etc. Normally, most of zeolites were synthesized in the presence of organic templates, and the use of them usually results in more or less shortcomings including high cost of organic templates and production of environmentally undesirable gases by high temperature calcination for removing these organic templates, which strongly influence their applications. Thus, it is very important to develop an organotemplate-free route for synthesizing zeolites. Addition of seeds crystals has been demonstrated as an effective method to accelerate the crystallization of zeolite, improving the purity of the crystal product. Based on the effect of seeds, we have successfully developed a seed-directed and organotemplate-free (SDS) synthesis of zeolites such as Beta, FER, ZSM-34 and LEV, where zeolite seeds play similar roles to the “templates’’ that direct crystallization of zeolites from the amorphous aluminosilicate gels. When no zeolites seeds were added, the product is amorphous products at the same condition. As a common process for the synthesis of these zeolites in the absence of organic templates, aluminum and alkali sources were dissolved into H₂O, followed by addition of fumed silica. After stirring at room temperature for 5 h, zeolite seeds were introduced into the aluminosilicate gel. After further stirring for 5 min, the mixture was transferred into an autoclave for crystallization. After filtrating, washing with deionized water and drying, zeolite products were obtained. The calcination of the sample for removing organic templates could be fully avoided due to the absence of organic template. In the present article, we show the recent results about the synthesis and characterizations of zeolites including Beta, FER, ZSM-34 and LEV using this SDS route.

Key words: zeolite, microporous crystals, organotemplate-free, seed-directed synthesis