Synthesis And Characterization Of Zeolite Composite Materials

Zeolites, which are crystalline aluminosilicates with uniformly sized pores of molecular dimensions in their three-dimensional framework structures, have many fascinating and exploitable properties, such as ion-exchange, sorption capacity, shape selectivity, catalytic activity, and the ability of acting as hosts in advanced materials. In this thesis, in order to make a good application for zeolite, we will focus on the synthesis of zeolite membrane and core shell zeolite composites.In general, the growth of zeolite has nucleation and crystallization two steps. In this thesis, hydrothermal synthetical method is employed for the study on the growth when the nucleation is heterogeneous. These substrates for nucleation include stainlesss steel net and different type zeolite. Zeolite membrane has some advantages, besides it can make zeolite powder as a'device', the mainly contribution is zeolite membrane can carry out the property of shape selective separation. Under certain pressure, the separation by using membrane will be more effective compared with the traditional adsorption separation. Supported zeolite membrane has better mechanical performance and convenient operation than self-supported zeolite membrane. But diverse supported substrates have different properties, which will influence a lot for further zeolite growing. Therefore, it is very important to know about the characters of different substates. Compared with growing zeolite on ceramic support, zeolite growing on metal support has the nucleation happened randomly, and this will make the crystallization of zeolite be disordered. Growing zeolite membrane on porous metal support, it is hard to prepare even covered zeolite membrane when the nucleation is random. So, it is necessary to set the position for nucleation, a desired position and lead the nucleation to happen in a proper way. In our group, Xiaoju Yin used stainless steel net as support, vio heating by electric resistance furnace, and utilized surface tension of water to seed zeolite crystals on the support, uniformly. In this work, the same method was used for preparing several types of zeolite membranes, especially for zeolite X membrane. The mainly aim of this work is to check the factors during the synthesis to the growth of membrane, and then better the preparation of film.To grow one type of zeolite on another type of zeolite, is a good method to study the nucleation and crystallization of zeolite, and is also a significative attempt for zeolite membrane, especially for orientation growth-zeolite membrane. Zeolite core-shell composites are crystals with one type of zeolite fully covered growing on the surface of another type of zeolite crystals. This new material not only achieves the intergrowth of these two zeolites, but also obtains the combination property of them. This thesis was focused on the study of core shell X/A composites, including the structure determination and gas adsorption test. The growth process of the shell zeolite A was detected by SEM and powder XRD. FIB technique was used for the specimen preparation for TEM, and finally the specimen was checked by TEM and the EM patterns were obtained. All the TEM results confirmed that the growth of zeolite A on zeolite X is epitaxial, which was validated by Single crystal XRD. Epitaxial growth means the growth of zeolite A is not disordered, the channels between them are open. The channel system on the interface is open; this was also proved by gas adsorption. The X/A core shell composites have the gas adsorption volume for CO2closer to that of zeolite X and larger than that of zeolite A, and have the selectivity for CO2closer to that of zeolite X and much larger than that of zeolite X. This reached the so-called combination of structures and properties.