Synthesis And Characterization Of Mesoporous Mordenite Without The Addition Of Organic Template

Mordenite is one kind of crystalline microporous aluminosilicates. Because of regular pore array, large surface area,high stability and strong acidity, it has been widely used in the fields of adsorption and separation, catalytic cracking and isomerization. However, due to the diffusion limitation resulted from small pore size, the catalyst showed low catalytic acitivity in reactions with large-sized molecules. To solve the problem, one way is to synthesize nanosized zeolites. However, because of some disadvantages including low stability and the difficulties of separation and controlling the particle size, the nanosized zeolites can not meet the need in industry. Recently, the discovery of mesoporous zeolites opens a new way to solve the above problem. Because of their advantages about that they not only maintained the strong acidity and high stability of zeolites, but also possessed the mesoposity to improve the ability of mass transfer, mesoporous zeolites have potentials in industrial application.The dissertation mainly focused on the synthesis and characterization of mesoporous mordenite without the addition of organic template, which included three sections: 1. synthesis of mordenite; 2. synthesis of mesoporous mordenite by alkali treatment; 3. acidity test and evaluation of catalytic activity about mordenite.By the route of hydrothermal synthesis, the influence of various factors such as silica sources, the molar ratio of Si/Al, water content, crystallization time and additives was investigated about the synthesis of mordenite. Moreover, the synthesis of mordenite with high Si/Al was also explored. The results indicated that the parameters including silica source, alkali concentration and the ratio of Si/Al in the original gels played a vital role on the synthesis of mordenite. The optimum synthesis condition is that the molar ratio of Na₂O/SiO₂ is 0.2⁰.3, the molar ratio of H₂O/SiO₂ is 7¹0, the hydrothermal temperature and time is 180 oC and 5 days, respectively. The presence of additives in our synthesis system can not increase the ratio of Si/Al in product, but change the morphology of mordenite crystal.By alkali treatment, mesoporous mordenite was synthesized. Some parameters including alkali type, alkali concentration, and the type of mordenite before alkali treatment were studied. The results show that NaOH is a good treatment reagent and H-form mordenite is more benificial for the formation of mesopore than Na-form mordenite.The Friedel-Crafts alkylation of benzene with benzyl alcohol was used to evaluate the catalytic performance of mordenite. The results from acidity test and catalytic data prove that meoporosity in zeolites plays an important role on improving the catalytic performance in the reaction.