Synthesis and characterization of bundle-shaped ZSM-22 zeolite via the oriented fusion of nanorods and its enhanced isomerization performance

• Published in: Journal of catalysis Vol. 361; pp. 177 - 185
• Main Authors: Chen, Zhiqiang, Liu, Suyao, Wang, Honghao, Ning, Qiang, Zhang, Huaike, Yun, Yifeng, Ren, Jie, Li, Yong-Wang
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.05.2018
• Subjects: acidity; aluminum; Bronsted acids; catalysts; crystal structure; F-T oil; Isomerization; Lewis acids; micropores; nanorods; nuclear magnetic resonance spectroscopy; Oriented fusion; silicon; stable isotopes; X-ray diffraction; X-ray fluorescence spectroscopy; zeolites; ZSM-22 zeolite; F-T oil; ZSM-22 zeolite; Oriented fusion; Isomerization
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/j.jcat.2018.02.019

[Display omitted] •ZSM-22 zeolites with different morphologies are synthesized.•Z-BUN possesses more framework Al atoms over T1+T2+T3 sites than that of Z-CON.•The interfacial effect can suppress B acid strength and generate more L acid sites.•Isomerization selectivity is enhanced due to the oriented fusion of nanorods. ZSM-22 zeolites with needle-shaped, bundle-shaped, as well as bulk-shaped morphologies are prepared by tuning hydrothermal synthesis conditions. These as-synthesized zeolites have similar crystallinity, Si/Al ratios and micropores revealed by XRD, XRF and BET. However, the oriented fusion of nanorods in the bundle-shaped ZSM-22 zeolite leads to the formation of more framework aluminum atoms over T1 + T2 + T3 sites on the 10-membered rings than that of needle-shaped ZSM-22 zeolite as detected by the 27Al 2D 3Q MAS NMR. The acidity properties determined by Py-FTIR and DMPy-FTIR show that the interfacial effect between the adjacent nanorods can effectively suppress Brönsted acid strength at the pore mouths and external surface. Interestingly, more Lewis acid sites are generated due to the interfacial defects. As a result, the Pt/Z-BUN catalyst with the weaker acidity and high dispersion of Pt exhibits the highest isomerization selectivity due to the more balanced bifunctionality between acid sites and metal sites among the as-prepared catalysts.