Abstract
Hierarchically porous ZSM-5 was prepared by utilizing a two-step crystallization procedure with carbon–silica composites as precursors. The hierarchically porous zeolites obtained a regular mesoporous structure with aluminum incorporated into the carbon–silica composite frameworks. The carbon–silica composite zeolites were characterized by XRD, TEM, SEM, and nitrogen adsorption/desorption. As-prepared hierarchical zeolites were used in the 1,3,5-triisopropylbenzene (TIPB) cracking reaction and exhibited significantly high TIPB conversion, while the accessibility factors were also determined.
Highlights
Zeolites are crystallized aluminosilicates with uniform micropores which have been widely utilized for ion exchange, catalysis, and adsorption [1,2,3]
After the prepared hierarchically porous ZSM-5 samples were further hydrothermally treated at 373 K for 7 d, the HPZ-CSI-x showed the morphology of sphere particles composed of nanocrystal, which appeared rather dense and smooth (Figure 1e,f)
The results suggest that the hierarchical zeolites have excellent catalytic properties in TIPB cracking reactions involving bulky molecules
Summary
Conventional zeolites often lead to diffusion and mass transfer obstacles due to the nature of micropores, resulting in a relatively low utilization of the zeolite active sites in catalysis. In order to overcome these limitations, the synthesis of novel materials which combine both zeolites and ordered mesoporous materials is essential, especially for the field of catalysis. As-made micro-meso-large-pore zeolites have some important advantages, such as their hierarchical pore system, their increased number of active sites, as well as their better diffusivity and hydrothermal and thermal stabilities. Low structural stability as well as the synthesis of materials with poor pore channel ordering and wide ranges of pore size distribution are still considerable challenges
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