Abstract: In order to solve the problem of poor thermal stability and hydrothermal stability of small crystal size Y zeolite, the USY zeolites were prepared by SiCl4 gas phase hyperstabilization using different particle size NaY zeolites as raw materials. The effects of different particle size and different silicon-aluminum ratios on physicochemical properties, MAT activity and hydrothermal stability of Y zeolite were investigated. The results showed that the hydrothermal stability of small crystal size Y zeolite could be greatly improved by the SiCl4 gas phase hyperstabilization where the skeleton aluminum was substituted by silicon. After the hydrothermal treatment at 800 ℃, 4 h, 100% steam, the crystallinity retention and acid properties of small crystal stablized Y zeolite with crystal size about 700 nm and crystal lattice constant over 2.440 nm were similar to those of gaseous stablized traditional Y zeolite. Since small crystal zeolites had much more active centers on the external surface, leading the large molecular, which could hardly diffuse into the zeolite canal, more conducive to react. The conversion of 1, 3, 5-triisopropylbenzene could increase 15-23 percentage points on the SiCl4 stabilized Y zeolite with small crystal size, compared with gaseous stablized ordinary Y zeolite.

Key words: small crystal Y zeolite, gas phase hyperstablization, heavy oil, catalytic cracking