Abstract: High-crystallized β-zeolites with different silica-alumina molar ratios were successfully synthesized in extremely dense aqueous system using tetraethylammonium hydroxide (TEAOH) as template and solid silica gel as silica source, respectively. The silica-alumina molar ratios in the initial gels were 30, 60, 150, 300, 500, and pure silica, respectively, which were consistent with those in so-prepared samples determined by chemical method and XRF analysis. Subsequently, the physicochemical properties of samples were characterized by XRD, FT-IR, SEM, NH3-TPD, and N2-adsorption analysis. The results showed that the extent of dealumination was changed obviously and the acid content was decreased significantly in the low silica β-zeolite with highest aluminium content after hydrothermal treatment. The high silica or pure silica β-zeolites could not display higher hydrothermal stability partly due to their small grain sizes. After hydrothermal treatment, the medium silica-alumina ratio zeolite beta could remain higher acid amount and showed better hydrothermal stability. The effect of β-zeolites with different n(SiO2)/n(Al2O3) ratios as an active additive on cracking performance has been investigated. It was found that β-zeolite could increase the activity of cracking catalyst and improve the performance of resistance to carbon deposition. As β-zeolite with n(SiO2)/n(Al2O3) molar ratio of 150 was added, the cracking catalyst exhibited the higher cracking gasoline yield and lower carbon deposition.

Key words: Silica-alumina ratio, β-Zeolite, Physicochemical property, Catalytic cracking