A hierarchical zeolitic Murray material with a mass transfer advantage promotes catalytic efficiency improvement

Abstract

By employing carbon-packed zeolite nanocrystals as primary building blocks, hierarchically porous MFI-type zeolites with precise dimensions spanning meso- and micro-length scales were successfully synthesized using an in situ crystallization strategy. The generalized Murray's law was firstly used to theoretically investigate the advantage of the porous hierarchy of the zeolites. The porosity distribution and coordination in the resultant zeolite crystals were found to be basically following the generalized Murray's law. Probing using the catalytic cracking reaction of isopropyl benzene revealed that as-prepared HierZSM-5 exhibited much higher conversion (∼74.5%), compared with nanoZSM-5 (∼30%) and bulky ZSM-5 (∼28.6%). The outstanding catalytic performance was ascribed to the highly enhanced mass transfer of the Murray zeolite material in the heterogeneous catalytic reaction. Such a hierarchical single zeolite structure, designed by adopting the generalized Murray's law, can improve the thermal/hydrothermal stability of nanozeolites, and offer an alternative option for a long-term stable catalyst.