Synthesis Of Nanosized ZSM-5 Zeolite With High Molar Ratio Of Silica To Alumina

The crystal size of zeolite is an important factor that affects the properties of zeolite. Nanosized ZSM-5 zeolites have larger external surface, high surface energy and shorter channels as compared with the microsizd zeolites, which are particularly suited for catalysis applications. But, investigations show that the thermal stability of nanosized ZSM-5 is not so good as that of microsized ZSM-5.To improve it, the synthesis of nanosized ZSM-5 zeolites with high molar ratio of silica to alumina have been synthesized successfully in this thesis, which were characterized by X-ray diffraction, transmission electron mocroscope, scan electron mocroscope, X-ray fluorescence. A better synthesis was selected and was enlarged in a 100L autoclave. Good results have been achieved.Factors affecting the synthesis of ZSM-5 zeolite with traditional method are investigated such as crystallization temperature, supersaturated degree of reaction mixture, salt amount, alkalinity, seed crystal size, stirring rate, the sequence of adding material and so on. In this paper, two synthesis methods of ZSM-5 zeolites were developed based on the traditionally synthetic method .one is to add a little mount of tween series as nonionic surfactants. The other method is to use iso-propyl alcohol and n-Butylamine as co-template. Results show that tween series (tween 20, tween 40,tween 60, tween 80) can decrese crystal size. Because tween series would be saponified under the high PH of system and changed into polyoxyethylene sorbitol anhydride and hard soap which reduce the surface energy of little particles. Results showed that tween 20 is the best choice, In the system of iso-propyl alcohol and n-butylamine as co-template, the molar ratio 0.36 of iso-propyl alcohol to n-butylamine is favorable. Sodium chloride plays different role in the different system of tween series and co-template, the presence of sodium chloride in the tween series has negtive effect to the formation of nano-size ZSM-5, however, the presence of sodium chloride in the system of iso-propyl alcohol and n-butylamine as co-template has positive effect, the suitable ratio of NaCl toAl2O3 is 57.8.The thermo- and hydrotherm-ostability of nanosized ZSM-5 zeolites were comparatively studied with micronsized ZSM-5 zeolites by high-temperature furnace calcinations. These results indicate that the change of the crystal size from micron-size to nano-size results in the decrease of the thermostability but not the hydrothermostability of ZSM-5 zeolite. Some investigation was also carried out on the route of removing template.