Synthesis of MTT zeolite catalysts with surface Al depletion

Selective catalytic cracking of n-hexane to propylene over hierarchical MTT zeolite

“…It was confirmed by 27 Al NMR spectra (Fig. 4) that insignificant octahedral Al at 0 ppm was observed.…”

“…Meanwhile, a strong peak at d = 56 ppm which corresponds to tetrahedral coordination of aluminum (in the framework) was obviously seen. The results showed that after desilication, all aluminum was still located in the framework of zeolite ZSM-23 as confirmed by solid-state 27 Al MAS. Al sitting and distribution are very crucial as De Waele and co-workers reported that MTT zeolite catalysts with surface Al depletion affected activity considerably [27].…”

“…The physical-chemical properties of parent and hierarchical MTT catalysts were characterized by X-ray diffraction, fieldemission scanning electron microscopy, N 2 physisorption, NH 3 TPD and solid-state 27 Al and 29 Si nuclear magnetic resonance (NMR) to obtain the physical and chemical properties of zeolite catalysts. Zeolite crystals were characterized by using field-emission scanning electron microscopes (FE-SEM, JSM-6500F, JEOL and LYRA 3 Dual Beam, Tescan) equipped Energy Dispersive XRay Spectrometry (EDX, Oxford Instruments) operated at Acceleration voltage: 30 kV.…”

“…The acidity of zeolites was analyzed by NH 3 TPD experiment with 1.0% NH 3 in He balance, a heating rate of 5 K/min and a final temperature of 950 K. XRF and EDX was used to analyze the Si/Al ratio of the zeolite catalysts. All solid-state 27 Al MAS-NMR spectra were recorded by using a Bruker MSL300 spectrometer. Rapid sample spinning ca.…”

“…The 27 Al magic-angle spinning (MAS) NMR was carried out to detect the presence of tetrahedral coordinated atoms (in the framework sites) and octahedral coordinated aluminum atoms (possibly as extra-framework aluminum/EFAL); before and after sequential alkaline-acid treatment under microwave irradiation. It was confirmed by 27 Al NMR spectra (Fig.…”