Control of the pore-opening size of HY zeolite by CVD of silicon alkoxide

Modification of HY zeolites with an SiO(2)/AL(2)O(3) molar ratio of 4.8, 5.6, 14.6 and 40.4 was carried out by the method of chemical vapor deposition of silicon alkoxides such as Si(OCH(3))(4) and Si(OCH(3))(2)(CH(3))(2). The pure and silica-deposited HY zeolites were characterized by adsorption measurements of nitrogen and 1,3,5-triisopropylbenzene, and infrared spectroscopy. The pore-opening size, which was controlled by the silanation, was affected by the aluminum concentration of the HY zeolite and the silanation temperature. Pore openings on the HY zeolites with high aluminum concentration (SiO(2)/Al(2)O(3) = 4.8 or 5.6) were completely closed by the deposition of large amounts of silica, while pores in those with low aluminum concentration (SiO(2)/Al(2)O(3) = 14.6 or 40.4) could be controlled by the deposition of Si(OCH(3))(4). We obtained thus silica-deposited USY zeolites with different pore sizes, indicating a great potential as catalysts for the fluid catalytic cracking process. (C) 1999 Elsevier Science B.V. All rights reserved.