Study On Modification And Characterization Of USY Zeolite With Low Rare Earth Content

Fluid catalytic cracking (FCC) is the major heavy-oil refining operation, and also is thecrucial technology to oil refining enterprises. Y zeolite has been used as active ingredient incracking catalyst for FCC process almost all the time when it was found, due to it‘s specialstructure of twelve-membered ring‘in Y zeolite as Three-dimensional Open Framework, it‘smarkedly physicochemical properties and the lower cost. The cracking activity and selectivityof zeolite largely decide the products distribution; Therefore, the structure stability, crackingactivity and selectivity of Y zeolite are so important to petrochemical companies aboutmanufacture and economic interests.Currently, zeolite catalysts with higher rare earth (RE) content and bigger unit cell havesucceeded in industrialized application, nevertheless, the ratio of residual oil in FCC rawmaterials has become much more gradually. In order to adapt to complex reactionenvironment better, the zeolite catalysts with higher performance badly in need. Forexploiting a new style of Y zeolite catalyst, which possess higher silica-alumina ratio, smallerunit cell, better stability and selectivity. In this study, the ultra stable Y (USY) zeolites whichwith different rare earth content and different sodium (Na) content are prepared byimpregnation method. For the aim that synthetic effects of RE and Na on physicochemicalParameters of USY Zeolite with different content were investigated thoroughly, Thesesamples were characterized using X-ray diffraction (XRD), The NH3-temperatureprogrammed desorption technique (NH3-TPD), infrared spectra of pyridine adsorbed (IR),X-ray fluorescence (XRF), micro-activity reactor (MAT) and N2-adsorption technique. Inaddition to this, the modified USY zeolites by a series of RE elements of various ionicradiuses, by a series of some chemical elements and by a series of various impregnationmethods are also studied.The results suggest that the contents of RE and Na play significant roles inphysicochemical characteristics of Y zeolite. The thermostability of modified USY zeolitescan be much improved within8%content of RE. There is no significant boost in activity ofUSY if the RE increased over12%. When RE content reaches about4%, the extra-frameworkaluminum can be restrained notably. It was found that the unit cell constant of Y zeolites withhigher RE content is increased, however, the amount of weak acid is decreasing. With a traceof sodium, the mesoporous can be created and dealumination is restrained. In that way, theactivity and available acid sites also are improved partly. Following reduction of ionic radiusof RE elements, crystallization of retention-rate to USY zeolite become increasing as a whole,it seems that the reduction can exert an influence on stability of USY. The other chemicalelements such as boron (B) and phosphorus (P) can cause the decrease toward zeolites in acid amounts and acid strength. Some conclusions also can be drawed that the differentimpregnation methods put the different influences on physicochemical characteristic of USYzeolite. All acquired results from this study, which will provide the theoretical basis forfurther research of this related field and be the salutary lessons or reference for industrializedapplications.