Preparation Of Silicalite-1 Hollow Fibers And Hollow Spheres Using Plant Templates

Zeolite materials with hollow structures, such as hollow fiber and hollow spheres, have attracted considerable attention because of their potential applications such as in microreactors, supports, membrane separation, gas sensors, photovoltaics, controlling releasing capsules, artificial cells, shape selective catalysis and adsorption. At present, the template approach was the main method to prepare zeolite hollow fibers and hollow spheres, which was conducted by first absorbing zeolite crystal seeds on the surface of modified templates, such as carbon fibers and polystyrene microspheres, through Layer-by-Layer technique, followed by hydrothermal synthesis to prepare zeolite/template composite materials. After remove-off of the template, zeolite hollow fibers and hollow spheres were prepared. However, these templates were expensive and complex surface modification had to be used in the process. In this thesis, natural materials, such as daily used cotton threads, palm fibers and rapeseed pollens were, respectively, used as the templates to prepare silicalite-1 hollow fiber and hollow sphere by hydrothermal synthesis. These samples were characterized by TG-DSC, XRD, BET and SEM.Firstly, daily-used cotton thread was used as the template. By using loose cotton thread as template, bunchy silicalite-1 hollow fibers could be prepared after hydrothermal synthesis and calcination. On the basis of bunchy silicalite-1 hollow fibers, silicalite-1 honeycomb can be prepared by increasing the cycles of hydrothermal synthesis. Furthermore, by stretching the cotton thread to reduce the space between cotton fibers to certain extent, single silicalite-1 hollow fiber with an inner diameter of 56μm and siliaclite-1 monolith with a size of 800μm×3 cm could be prepared.Secondly, by using palm fiber as the template, single silicalite-1 hollow fiber with inner diameter of 220μm was prepared. When a bunch of about 15 palm fibers was wrapped together by a Teflon tape and then immersed in the synthesis solution, silicalite-1 honeycomb with strong mechanic strength was prepared after synthesis for...