Effect of Atmosphere-Controlled Pressurized Steaming on the Structure and Cracking Performance of As-Prepared LaY Zeolite

This study focuses on exploring the impact of atmosphere-controlled pressurized steaming (at 500 °C and 0.3 MPa) on the structure and catalytic performance of LaY zeolite. A weakly alkaline calcination atmosphere (pH 9.6) is introduced during the pressurized steaming process. This introduction significantly promotes the solid-state migration of La³⁺ ions from supercages to sodalite cages, resulting in an 18% increase in the I₁/I₂ ratio. It also enhances the B/L acid ratio by 45% and improves the hydrothermal stability of the zeolite with the crystallinity retention rate rising by 25%. The proposed process achieves a balanced dealumination-desilication mechanism. While maintaining the crystallinity of the zeolite, it generates uniform 3–4 nm intracrystalline mesopores. The mesopore volume accounts for an increasing proportion of the total pore volume, from 5% to 16%. Catalytic evaluation results show that, compared with the atmospheric calcination reference sample, the heavy oil conversion rate increases by 8.8% points, the gasoline yield rises by 8.0% points, and the coke yield is lower. This can be attributed to the mesopores improving the accessibility of reactants and reducing diffusion resistance. This research demonstrates that the atmosphere-controlled pressurized steaming under a weakly alkaline calcination atmosphere is an effective strategy for preparing LaY zeolite with high stability and high activity, which is suitable for heavy oil cracking.