Solvent-free Synthesis Of Aluminosilicate Zeolites And Its Catalytic Performance

During the last several decades, the high demand of olefins and p-xylene has brought about great progress in methanol-to-olefin and m-xylene isomerization technologies using aluminosilicate zeolites as shape selective catalysts, duing to their uniform microporous channels, high surface area, and excellent hydrothermal stabilities. In general, the traditional syntheses of zeolites usually require large amounts of solvents such as water and other alcohols. The presence of solvents in the solvothermal synthesis produces wastes, generates high pressure and influences the product yield. On the other hand, The use of toxic and costly organic templates not only increases the zeolite cost but also results in the pollution of the environment.Recently, to overcome the drawbacks brought from using large amounts of solvents, a solvent-free synthesis route was successfully developed for synthesizing zeolites which includes both aluminosilicate and aluminosilicates. However, the solvent-free synthesis routes of SSZ-13and EUO have still not been found. The SSZ-13exhibits extraordinary catalytic properties in MTO and NH3-SCR. However, the expensive cost of the template and relatively low yield in the hydrothermal synthesis of SSZ-13strongly hinder its wide applications. The one-dimensional EUO zeolite which has peculiar pore architecture displays excellent application in m-xylene isomerization.In this work, solvent-free synthesis of high silica SSZ-13is successful in the presence of a novel low-cost organic template (DMECHABr). This synthesis is atom-enconomic, giving the efficiency of silica species in the product is as high as95.7%. More importantly, this sample exhibits similar chemical and physical properties to those of conventional SSZ-13synthesized from hydrothermal route. In the third chapter of the thesis, solvent-free synthesis is successfully extended to the synthesis of EUO zeolites. Notably, crystal size of ZSM-5zeolites can be controlled by adding seed in the solvent-free synthesis process. The effect of crystal size of solvent-free zeolites on the selectivity and deactivation of related catalytic performance is studied in the fourth chapter.The advantages of high yields, low pollution, reduction of pressure, and good properties for solvent-free synthesis of zeolites would offer more opportunities for wide applications in the fields of adsorption, separation, and catalysis in the future. The new green methodology for zeolite synthesis is of great importance for the sustainable development of the world.