In-situ preparation of highly dispersed zeolite-based FCC catalysts for hierarchical cracking of macromolecules

Optimizing the dispersion of ZSM-5 zeolite-based cracking active components is essential for enhancing the performance of FCC catalysts in cracking macromolecules. A series of composite catalysts with varying ZSM-5 zeolite contents were synthesized via an in-situ solid-phase crystallization method by controlling the crystallization time. Unlike the significant aggregation of zeolite components observed in the physically mixed catalyst, the ZSM-5 zeolite is uniformly distributed within the alumina matrix of the in-situ crystallized composite catalyst (Z/A-36). The distinctive distribution characteristics of zeolite enhance the accessibility and utilization efficiency of active components. The catalytic cracking performance of the composite catalysts was evaluated using 1,3,5-triisopropylbenzene (TIPB) as a model macromolecule. Notably, Z/A-36 exhibits excellent catalytic performance, achieving a cracking conversion of 81.2% while maintaining high stability. The improvement in catalytic activity is attributed to the effective utilization of zeolite components rather than to the amount of zeolite. • A composite with uniform ZSM-5 distribution is obtained by in-situ crystallization. • The growth of ZSM-5 zeolite on the alumina substrate is effectively controlled. • The utilization efficiency of zeolite components has been significantly optimized. • The Brønsted acid sites provided by the matrix facilitate the pre-cracking of TIPB. • The in-situ crystallized composite exhibits excellent TIPB cracking performance.