Synthesis Of Nano-NaY Molecular Sieve By Means Of Microwave Pretreatment

Y-type zeolite as a active catalyst, with its good catalytic activity and high temperature stability, was widely used in catalytic cracking and hydrocracking process. Compared with commercial Y zeolite, Y zeolite with nanosized particals had the unique features, such as greater external surface area, more exposed active sites, short and regular pores, which resulted in a higher catalytic activity, selectivity, longer catalytic lifetime and higher resistance to sulfur, nitrogen and heavy metal pollution performance.In this thesis, the factors affecting preparation of nano-NaY zeolite with hydrothermal synthesis method, such as crystallization time, aging time of nucleation gel, alkalinity of the precursor for the synthesis NaY were investigated in detail. The samples synthesized were characterized by XRD and SEM techniques. The corresponding results are as follows:(1) The results indicated that the most important factor affecting the synthesis of nano-NaY is alkalinity of the synthesis system. For synthesizing pure nano-NaY zeolite, the best molar composition of synthesis system is 9.5Na2O:Al2O3:10SiO2:210H2O, and the aluminosilicate gel obtained should be crystallized at 90℃for 4 hour. The nucleation gel should be aged for four days before being added to hydrothermal kettle in wt.10% of the synthesis precursor accounted in moles of Al2O3.(2) It was found that treating the aluminosilicate gel in microwave for several minutes before hydrothermal crystallization benefits to the nanosized NaY synthesis, while ultrasonic pretreatment do not work. Under the optimized synthesis condition, NaY zeolite with uniform grain size of about 90 nm was successfully obtained.