Synthesis Of Microsized NaY Zeolite And Grain Size Distribution Control

Zeolite microsized Y can noticeably improve the catalytic cracking selectivity with reduced coking, and increase both diesel yield and the gasoline qulity due to the fact that microsized Y have high surface areas, fast diffusion characteristics. Although numerous studies have addressed the preparation of zeolites, it has been very difficult to understanding of the synthesis mechanism under hydrothermal synthesis conditions. So the size and grain size distribution of the obtained NaY are still not satisfactory.The effection of ageing time on seed solution is investigated firstly. The seed solution is characterized by UV Raman spectroscopy. UV Raman spectra indicate that no precursor appear. The synthesis of zeolite Y is characterized by UV Raman spectroscopy and X-ray diffraction. UV Raman spectra of solid phase of the synthesis system indicate that characteristic band appear at 505 cm^-1 which is four-membered rings after 2 hours crystallization. However, X-ray diffraction indicates that the synthesized product is amorphous. No characteristic bands appear in UV Raman spectra of liquid phase at the time. After 4 hours crystallization, characteristic bands appear at 505cm^-1 and 305 cm^-1,360 cm^-1 which are double six-membered rings. UV Raman spectra of liquid phase of the synthesis system indicate that only one characteristic band appears at 500 cm^-1 during crystallization, double six-membered rings are not appeard. The synthesis of no seed solution system is characterized by UV Raman spectroscopy and X-ray diffraction. UV Raman spectra of solid phase of the synthesis system indicate that only 490cm^-1 band appear, 305 cm^-1,360 cm^-1 are not appeard all the time during 20 hours crystallization.Microsized NaY zeolite was synthesized by industrial raw materials and surfactant Tween20 using hydrothermal techniques. The mean particle size of NaY was reduced by adding small amount of Tween20 into the starting mixture. Whereas, the grain size distribution of the obtained NaY was in a wide range due to the extremely low water solubility of Tween20. Alcohols were choosen to solubilize Tween20. The effects of different alcohols, alcohol concentration and alcohol/Tween20 ratio on mean particle size and size distribution were investigated. The results show that the grain size distribution can be effectively controlled in a quit narrow range by adding ethanol as an assistant solvent of Tween20 in an optimized ratio. Catalytic performances of NaY zeolite were investigated in the cracking of diisopropylbenzene as probe reaction. Catalytic activity of NaY zeolites increased with the decreased of particle size. However, the catalytic activity and stability are decreased when the particle size became to 330 nm.