Research On The Self-assembly Method And Catalytic Property Of Y Zeolite Introduced By Lathanum Cations

Active metal and support play an important role in the preparation of catalysts for deep catalytic cracking (DCC), one of the most widely applied processes that base on fluid catalytic cracking (FCC).A base NaY zeolite was exchanged to LaHY zeolite with law Na content under twice modifications. The preparation conditions and the modification methods of HY zeolite have effect on the resulting catalysts, which were evaluated with physichemical properties by means of characterization of technology, and catalytic activities by catalytic cracking of n-hexane.The catalysts of La supported on different HY zeolites was prepared by isovolume impregnation method, which were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), BET surface area measurements, and NH3-temperature programmed desorption, and evaluated for the catalytic cracking of n-hexane. The results showed that the lower Na content, the lower crystallinity and cell parameters did LaHY zeolite acquire, while total acid amount and specific surface areas were more and the catalytic activity and olefin selectivity was higher. The LaHY zeolite has higher crystallinity, total acid amount, specific surface areas and the catalytic activity at higher temperature of HY zeolite. When the temperature was higher than550℃, the physichemical and catalytic properties of LaHY zeolite were decreased.A series of LaHY zeolites were prepared by isovolume impregnation method, improving isovolume impregnation method and adherency method. In comparison with zeolite Y modified by different methods, the physichemical properties of catalysts were studied by XRD、NH3-TPD、BET and Py-IR, and catalytic activities were investigated by the catalytic cracking of n-hexane. It is found that the amount of lanthanum in sodalite cage is one of the significant factors in determining the structure and properties of modified Y zeolite. Comparison of adherency method and isovolume impregnation method indicated that LaHY zeolite prepared from the latter with the more rare earth loading in sodalite cage exhibited the higher conversion and selectivity. Furthermore, improving isovolume impregnation method is favorable to the migration of more lanthanum from super cage to sodalite cage, which improves the stability and activity of LaHY zeolite, then adjusts the distribution of acid content and product yield.