Abstract
A series of ZSM-5 zeolites with hierarchical porous structure were synthesized using NaOH solutions treatment method. The structural and acidity properties of hierarchical ZSM-5 zeolites as-synthesized were characterized by X-ray diffraction (XRD), N2 adsorption, scanning electron microscope (SEM), NH3-temperature programmed desorption (TPD), and pyridine Fourier transform infrared spectroscopy (Py-FTIR). The adsorption and diffusion performances of benzene in hierarchical ZSM-5 zeolites were studied by an intelligent gravimetric analyzer (IGA). It was found that mass transfer (adsorption and diffusion) performance of benzene was significantly affected by synergetic effect of hierarchical structure, acid amount, acidity, adsorption sites of ZSM-5 zeolites. After suitable alkali treatment, the crystal structure of ZSM-5 was retained and finely tailored. Hierarchical ZSM-5 was obtained with a uniform size of mesoporous and microporous structure. Acidity of hierarchical ZSM-5 zeolites was improved, which produced more adsorption sites and thus increased the adsorption performance of benzene in hierarchical ZSM-5. As a result, connectivity in hierarchical ZSM-5 was improved with increasing of mesopores in hierarchical ZSM-5. Hierarchical ZSM-5 well-contributed to the adsorption performance of benzene on active sites and improved catalytic performance of hierarchical ZSM-5.
Highlights
ZSM-5 are commonly used in industry due to the thermal stability and high surface area, appropriate pore size
X-ray diffraction (XRD) patterns results showed the hierarchically structured ZSM-5 can be obtained by alkali-treatment methods while preserving the MFI micropore structure
The hierarchically ZSM-5 with good connectivity was successfully synthesized by alkali treatment method
Summary
ZSM-5 are commonly used in industry due to the thermal stability and high surface area, appropriate pore size. The acidic property has very little change quantitatively or qualitatively, even though the catalytic activity for cracking of cumene was enhanced by the alkali-treatment due to that the adsorptive and diffusive performance of cumene are increased by the creation of mesopores in microporous ZSM-5. XRD patterns results showed the hierarchically structured ZSM-5 can be obtained by alkali-treatment methods while preserving the MFI micropore structure.
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