Factors affecting the synthesis of microsized NaY zeolite

A detailed investigation was carried out to determine the effects of time a nd temperature of aging and crystallization on the synthesis of microsized NaY zeolite. Gels were prepared by adding a sodium silicate solution to an initial solution of aluiminosiliate and stirring until a clear mixture form ed, then adding aluminum sulfate solution and sodium aluminate solution in sequencer After stirring for Ih, gels with the composition Na2O:Al2O3:SiO2: H2O = 3.01:1.00:7.50-10.0:200 were aged at fixed temperature and time, and then crystallined at 100 degrees C. The kinetics of crystallization were fo llowed by powder X-ray diffraction. Compositional and structure information was provided by elemental chemical analysis, infrared and Raman spectrosco pies and scanning electron microscopy. It was found that the rate of crysta llization and the composition of the crystalline products depend strongly o n the aging time and temperature. Compared with the unaged sample, the aver age particle size of the aged products decreased from 2.8 to 0.25 mu m and the overall particle distribution reduced from the 0.5-5 mu m range to 0.05 -0.8 mu m. With yield greater than 95%, the ratio of Si/Al greater than or equal to 5.5. The decomposition temperature (as measured by dynamic thermal analysis) is as high as 890 degrees C and the surface area reaches 1050 m( 2)/g. (C) 1998 Elsevier Science B.V. All rights reserved.