Abstract: NaY/kaolin composite microspheres were prepared by in-situ crystallization of kaolin microspheres after introducing Y zeolite seed solution in the preforming process, and it was characterized by X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), N2 adsorption-desorption at low temperature and scanning electron microscopy (SEM). XRF and XRD showed that compared with conventional methods, the silicon aluminum ratio of NaY/kaolin composite microspheres prepared by introducing seed solution increased from 1.61 to 1.70, and the crystallinity of Y zeolite increased from 21% to 29%. N₂ adsorption-desorption characterization result showed that the specific surface area and pore volume of NaY/kaolin composite microspheres prepared by conventional methods were 311.8m²/g and 0.28cm³/g, respectively. After the introduction of seed solution, the specific surface area and pore volume increased to 521.8m²/g and 0.41cm³/g, respectively, and the mesoporous distribution increased from 4-25 nm to 10-150 nm. The catalytic cracking test results of heavy oil showed that compared with conventional methods,the slurry yield over the in-situ crystallization catalyst prepared by introducing seed solution as additives decreased by 3.78 percentage points,the gasoline yield increased by 3.48 percentage points, and the total liquid yield increased by 3.11 percentage points.

Key words: kaolin, in-situ crystallization, Y zeolite, seed solution, catalytic cracking