Investigation of the pore structure of hierarchical Y-zeolite via experimental and computational approaches

Abstract

Numerous studies have investigated hierarchical Y-zeolites experimentally, given their significance in overcoming diffusion limitations during heavy oil cracking applications. However, computational modeling of these micro-mesoporous structures remains limited. This study presents a computational technique for simulating hierarchical Y-zeolites to analyze structural properties at an atomistic level. Three hierarchical models were considered, comprising microporous materials with mesopores carved into their structure. These models were constructed with various pore sizes using the Visualizer module in Materials Studio and characterized through molecular simulations. Specific surface area, porosity, adsorption isotherms, and pore size distributions were calculated using the Forcite and Sorption modules within Materials Studio. Simulation results were experimentally validated by synthesizing hierarchical Y-zeolites with varying pore sizes through post-synthetic surfactant-templating treatments. An acid reagent expanded pores and achieved controlled dealumination within the zeolite framework. Simulated adsorption isotherms and pore-size distributions closely matched experimental data. Key parameters characterizing hierarchical Y-zeolite structures were identified by fitting computational results to experimental isotherms, laying the foundation for predicting the adsorption behavior of different adsorbates in mesoporous Y-zeolites. Grand Canonical Monte Carlo (GCMC) simulations were also utilized to explain the nitrogen adsorption microstructure and multilayer adsorption mechanism. This approach provides a basis for constructing and modeling other micro-mesoporous structures in future studies.