Studies On The Syntheses Of Zeolites From The Layered Aluminosilicate Materials

This dissertation is about the transformation of layered materials to zeolite. And the layered materials include layered silicate and kaolin. The main work and the results of our study are outlined as following:In the first part, we used three kinds of natural layered silicate, kenyaite, magaditte and kanemite as parent materials, CTAB as intercalated reagent to synthesize zeolites directed by different templates. We hope that the two-dimensional layered structure could be retained during the zeolite growth, that is to say, the products would end up with perfect combination of zeolitic layered structure and improved external surface areas. The results show that Na-magaditte and Na-kanemite only served as silica source in such a pure silica system and their layers were totally destroyed during the crystallization. Due to its thick layers, Na-kenyaite is most likely to get the products we expect. We also introduced urea into the system, with the great hope that it could sustain or even delamination the layers. But what we find is that urea only increased the alkalinity and thus facilitated the growth of zeolite.On the based of the first part, we employed Na-kenyaite as starting materials and added Al which could control the growth speed of zeolites. The platelet ZSM-5zeolites, whose thickness average50-150nm, were synthesized through transformation from the CTAB-intercalated Na-kenyaite. And they could be sliced into zeolitic ZSM-5nanosheets via delamination, whose thickness was approximate to that of Na-kenyaite. The results indicate that instead of total destruction of the layered sheets, the layered structure of kenyaite was preserved throughout the transformation process due to the efforts of long-chain surfactants intercalated between the interlayer spacing. The influence of the CTAB was also investigated. Besides, MEL, Beta and FER were also obtained under the direction of different templates. We find that SiO2/ALO3, synthesis compositions, temperature and stirring period would exert noticeable influence on the final products. The third part focuses on the in-situ synthesis of NaY, with the kaolin powder and kaolin microspheres (KMT, T refers to KM’s activated temperature) as parent materials. In the light of the study on kaolin calcined/activated at different temperatures, we learn that with the increase of the temperature, the amount of activated SiO2increased while the activated AL2O3dropped. Moreover, premium synthesis compositions were also found. In the other part of the work, kaolin microspheres were used as starting materials and we adjusted the alkalinity, prepared clear structure-direct agent and modified kaolin microspheres, hoping to get FCC catalysts with small NaY crystals and high specific surface area of kaolin matrix. The results demonstrate that when we used KM830as parent materials, the resulting products were bulky NaY crystals which merged with each other intimately, without exposure of kaolin matrix. KM950would produce smaller NaY (200-300nm) which distributed separately among the kaolin matrix.